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Space Sci Rev (2020) 216:137
https://doi.org/10.1007/s11214-020-00765-9
The Mars 2020 Engineering Cameras and Microphone
on the Perseverance Rover: A Next-Generation Imaging
System for Mars Exploration
J.N. Maki1·D. Gruel1·C. McKinney1·M.A. Ravine2·M. Morales1·D. Lee1·
R. Willson1·D. Copley-Woods1·M. Valvo1·T. Goodsall1·J. McGuire1·R.G. Sellar1·
J.A. Schaffner2·M.A. Caplinger2·J.M. Shamah2·A.E. Johnson1·H. Ansari1·
K. Singh1·T. Litwin1·R. Deen1·A. Culver1·N. Ruoff1·D. Petrizzo1·D. Kessler1·
C. Basset1·T. Estlin1·F. Alibay1·A. Nelessen1·S. Algermissen1
Received: 8 June 2020 / Accepted: 9 November 2020 / Published online: 24 November 2020
© The Author(s) 2020
Abstract The Mars 2020 Perseverance rover is equipped with a next-generation engineer-
ing camera imaging system that represents an upgrade over previous Mars rover missions.
These upgrades will improve the operational capabilities of the rover with an emphasis on
drive planning, robotic arm operation, instrument operations, sample caching activities, and
documentation of key events during entry, descent, and landing (EDL). There are a total of
16 cameras in the Perseverance engineering imaging system, including 9 cameras for surface
operations and 7 cameras for EDL documentation. There are 3 types of cameras designed
for surface operations: Navigation cameras (Navcams, quantity 2), Hazard Avoidance Cam-
eras (Hazcams, quantity 6), and Cachecam (quantity 1). The Navcams will acquire color
stereo images of the surface with a 96◦×73◦field of view at 0.33 mrad/pixel. The Hazcams
will acquire color stereo images of the surface with a 136◦×102◦at 0.46 mrad/pixel. The
Cachecam, a new camera type, will acquire images of Martian material inside the sample
tubes during caching operations at a spatial scale of 12.5 microns/pixel. There are 5 types of
EDL documentation cameras: The Parachute Uplook Cameras (PUCs, quantity 3), the De-
scent stage Downlook Camera (DDC, quantity 1), the Rover Uplook Camera (RUC, quan-
tity 1), the Rover Descent Camera (RDC, quantity 1), and the Lander Vision System (LVS)
Camera (LCAM, quantity 1). The PUCs are mounted on the parachute support structure and
will acquire video of the parachute deployment event as part of a system to characterize
parachute performance. The DDC is attached to the descent stage and pointed downward,
it will characterize vehicle dynamics by capturing video of the rover as it descends from
the skycrane. The rover-mounted RUC, attached to the rover and looking upward, will cap-
ture similar video of the skycrane from the vantage point of the rover and will also acquire
video of the descent stage flyaway event. The RDC, attached to the rover and looking down-
ward, will document plume dynamics by imaging the Martian surface before, during, and
The Mars 2020 Mission
Edited by Kenneth A. Farley, Kenneth H. Williford and Kathryn M. Stack
BJ.N. Maki
Justin.N.Maki@jpl.nasa.gov
1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
2Malin Space Science Systems, San Diego, CA, USA
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137 Page 2 of 48 J.N. Maki et al.
after rover touchdown. The LCAM, mounted to the bottom of the rover chassis and pointed
downward, will acquire 90◦×90◦FOV images during the parachute descent phase of EDL
as input to an onboard map localization by the Lander Vision System (LVS). The rover also
carries a microphone, mounted externally on the rover chassis, to capture acoustic signatures
during and after EDL. The Perseverance rover launched from Earth on July 30th, 2020, and
touchdown on Mars is scheduled for February 18th, 2021.
Keywords Mars ·Remote sensing ·Planetary exploration ·Rovers ·Cameras ·
Space exploration
1 Introduction
The National Aeronautics and Space Administration (NASA) Mars 2020 Perseverance rover
launched from Earth on July 30th, 2020 and is scheduled to land on Mars on February 18th,
2021. The rover is designed to drive across the surface and collect samples of surface mate-
rial for possible return to Earth by a follow-on mission (Farley et al. 2020). To help achieve
this task the Mars 2020 Rover is equipped with a next-generation engineering camera imag-
ing system that represents a significant upgrade over the engineering camera systems flown
on previous missions. The Mars 2020 upgrades are focused on three key areas. The first area
is rover surface operations, including activities such as rover driving, robotic arm operations,
and science instrument operations. The second area includes documentation of sample pro-
cessing and handling operations inside the rover Adaptive Caching Assembly (ACA). The
third area includes documentation of the performance and operation of the Entry, Descent,
and Landing (EDL) system. Collectively the Perseverance next-generation imaging system
will improve the capabilities of the Mars 2020 mission and help to enhance the mission sci-
ence return relative to previous missions. This paper describes the Mars 2020 engineering
camera hardware and associated flight and ground software.
1.1 Scope
1.1.1 Engineering Cameras
This paper describes the 16 engineering cameras on the Mars 2020 rover. For the purposes
of this paper the Mars 2020 engineering cameras are divided into three groups, based on
the three separate development teams that designed, built, and delivered the hardware to
the Mars 2020 ATLO (Assembly, Test, and Launch Operations) team. The first group of
cameras is comprised of nine cameras dedicated to surface operations and includes the Nav-
igation cameras (Navcams, quantity 2), the Front Hazard Avoidance cameras (Front Haz-
cams, quantity 4), the Rear Hazard Avoidance cameras (Rear Hazcams, quantity 2), and
the sample Cache camera (Cachecam, quantity 1). The second group is comprised of six
cameras dedicated to EDL documentation and includes a Parachute Uplook Camera (PUC,
quantity 3), a Descent stage Downlook Camera (DDC, quantity 1), a Rover Uplook Cam-
era (RUC, quantity 1), and a Rover Downlook Camera (RDC, quantity 1). The third group
includes the LCAM (quantity 1), dedicated to providing critical image data to the Lander
Vision System (LVS) during the parachute descent phase of EDL. Data from all 16 cameras
will be available for use by the Perseverance science and engineering teams during the mis-
sion. Data from the engineering cameras will also be archived in NASA’s Planetary Data
System.
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The Mars 2020 Engineering Cameras Page 3 of 48 137
1.1.2 Science Cameras
In addition to the 16 engineering cameras described in this paper, there are seven cameras
on the rover dedicated to specific scientific investigations. The Mastcam-Z cameras (quan-
tity 2) acquire color stereo images with matching variable focal lengths using a zoom lens
(Bell et al. 2020). The SuperCam camera uses a next-generation Remote Microscopic Im-
ager (RMI), described in Maurice et al. (2020), to acquire context images for spectrometer
observations. The PIXL (Planetary Instrument for X-ray Lithochemistry) instrument uses
a Micro Context Camera (MCC) to acquire context images and images of projected laser
fiducial markings (Allwood et al. 2020). The SHERLOC (Scanning Habitable Environments
with Raman & Luminescence for Organics & Chemicals) instrument contains two cameras:
the Advanced Context Imager (ACI) for context imaging, and the WATSON (Wide Angle
Topographic Sensor for Operations and eNgineering) camera acquires image for general
documentation and context (Bhartia et al. 2020). The MEDA SkyCam acquires images of
the Martian sky as part of a larger atmospheric science instrument package (Rodriguez-
Manfredi et al. 2020).
The Navcam and Hazcam cameras provide targeting support and context imaging for
these science cameras. Images from the science cameras will be co-registered to the Navcam
and Hazcam images using calibration data acquired during Mars 2020 ATLO.
1.1.3 Summary of Perseverance Imaging System
There are a total of 23 cameras on the Perseverance mission (16 engineering cameras and 7
science cameras). Table 1lists the cameras and locations. Of the 23 cameras, 19 are rover-
mounted and 4 cameras are mounted to the entry vehicle. Of the 19 rover-mounted cameras,
16 of the cameras are designed for use during the nominal surface mission.
1.2 Background
1.2.1 Navcams, Hazcams, and Cachecam
The first Mars rover engineering cameras flew on the Mars Pathfinder Sojourner microrover
(Moore et al. 1997). The Sojourner rover flew three body-mounted cameras for traverse as-
sessment and documentation of vehicle state, augmented by a pair of pan/tilt mast-mounted
stereo color cameras on the Mars Pathfinder lander (Smith et al. 1997). The Spirit and Op-
portunity rovers standardized these camera types into an integrated imaging system, with
pan/tilt cameras (Navcams) and body-mounted cameras (Hazcams), as described in Maki
et al. 2003. The same Navcam and Hazcam designs were carried forward to the Mars Sci-
ence Laboratory (MSL) Curiosity rover, which flew identical copies of the MER cameras
(Maki et al. 2012).
The MER engineering cameras were designed and developed as part of a single camera
production effort with four Pancam cameras (Bell et al. 2003) and two Microscopic Imager
cameras (Herkenhoff et al. 2003). All 20 of the MER cameras shared the identical electronics
and detector design, with different lenses determining the camera type. The Mars Phoenix
mission flew two MER flight spare camera electronics and detector assemblies as part of the
Surface Stereo Imager camera system (Lemmon et al. 2008). The Mars Science Laboratory
(MSL) program ran a second production run of build-to-print copies of the MER Navcams
and Hazcams. A total of 14 of these cameras were flown on MSL (Maki et al. 2012). The
Mars InSight mission flew two MSL flight spare cameras, slightly modified with color filter
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137 Page 4 of 48 J.N. Maki et al.
Tab l e 1 List of cameras on the Perseverance rover and entry vehicle
Camera name Quantity Location Reference Type
Navcam 2 Rover (mast) Maki et al. (2020) (this paper) Engineering
Front Hazcam 4 Rover (body) Maki et al. (2020) (this paper) Engineering
Rear Hazcam 2 Rover (body) Maki et al. (2020) (this paper) Engineering
Cachecam 1 Rover (internal) Maki et al. (2020) (this paper) Engineering
PUCa3 Parachute structure Maki et al. (2020) (this paper) Engineering
DDCa1 Descent stage Maki et al. (2020) (this paper) Engineering
RUCb1 Rover (top deck) Maki et al. (2020) (this paper) Engineering
RDCb1 Rover (body) Maki et al. (2020) (this paper) Engineering
LCAMc1 Rover (body) Maki et al. (2020) (this paper) Engineering
Mastcam-Z 2 Rover (mast) Bell et al. (2020) Science
SuperCam RMI 1 Rover (mast) Maurice et al. (2020) Science
PIXL MCC 1 Rover (arm) Allwood et al. (2020) Science
SHERLOC ACI 1 Rover (arm) Bhartia et al. (2020) Science
SHERLOC WATSON 1 Rover (arm) Science
MEDA SkyCam 1 Rover (top deck) Rodriguez-Manfredi et al. (2020) Science
Totals 23 total: 19 rover-mounted +4 mounted to the entry vehicle
aDiscarded during rover landing event
bCommandable after landing, but not designed to withstand surface environment
cNot commandable after landing
arrays added to the detectors (Maki et al. 2018). A third MSL flight spare unit will fly on
the Mars 2020 Perseverance rover as part of the MEDA Skycam (Rodriguez-Manfredi et al.
2020).
A total of 36 individual flight unit cameras from the MER and MSL missions have flown
to Mars as of this writing. With an additional MSL flight spare camera flying on the Perse-
verance rover in 2020, the era for the MER/MSL cameras is coming to a close. The original
camera design from MER is now over 20 years old, and electronics parts obsolescence has
precluded any additional production runs without significant redesigns. Additionally, signif-
icant advancements in electronics and detector designs have occurred since MER, opening
up the possibility of improvements over the original designs.
In early 2013 an internal Mars 2020 project study was commissioned to examine the
possibility of modernizing the MER/MSL camera designs. After a prototyping phase, the
project baselined a set of new Navcam and Hazcam cameras in October 2014, along with
Cachecam, a new camera type. Detailed design began in 2015, and the next-generation en-
gineering cameras were delivered to the Mars 2020 ATLO in the summer of 2019. During
hardware development the next-generation engineering camera task was referred to as the
Enhanced Engineering Camera (EECAM) task. Once integrated onto the rover the engineer-
ing cameras assume the traditional ECAM name, along with the individual “cam” names of
Navcams, Front Hazcams, Rear Hazcams, and the newly designed Cachecam.
The Mars 2020 Navcams and Hazcams offer three primary improvements over MER
and MSL. The first improvement is an upgrade to a detector with 3-channel, red/green/blue
(RGB) color capability that will enable better contextual imaging capabilities than the pre-
vious engineering cameras, which only had a black/white capability. The second improve-
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The Mars 2020 Engineering Cameras Page 5 of 48 137
ment is that the Perseverance cameras have wider fields of view than previous versions,
which improves the quality of mosaics and increases downlink efficiency. The third im-
provement is that the Perseverance cameras have finer pixel scale (mrad/pixel) and are able
to resolve more detail than the MER/MSL cameras. All of the Navcam and Hazcam cam-
eras for MER, MSL, and Mars 2020 were built at the Jet Propulsion Laboratory/California
Institute of Technology, in Pasadena, CA.
The Mars 2020 rover carries a new camera type, the Cachecam, a fixed-focus imager
dedicated to sample inspection and documentation. Cachecam images will be used by the
sample operations teams to document and verify the processing of the sample material dur-
ing caching operations. The same images will also serve to document the tube contents
prior to sealing. The closest previous-mission analog to the Cachecam is the fixed-focus
Microscopic Imager (MI) flown on the MER mission (Herkenhoff et al. 2003). The MER
MI was mounted on a robotic arm and was placed into position by the arm for imaging. The
Cachecam, also a fixed-focus imager, is hard mounted inside the rover chassis. A robotic arm
inside the ACA brings sample tubes to the Cachecam for imaging operations. The Cachecam
was built at the Jet Propulsion Laboratory/California Institute of Technology as part of the
Navcam and Hazcam production run.
1.2.2 EDLCAMs
In 2014 the Mars 2020 project began to investigate options for improving knowledge of
Entry, Descent, and Landing (EDL) system performance using a video imaging system to
document key EDL events. Of particular interest were the parachute deployment, skycrane
deployment, rover touchdown, and lander rocket plume dynamics. The proposed solution
involved qualifying commercial off the shelf (COTS) hardware with an emphasis on low
cost and ease of system integration. In June of 2015 the Mars 2020 project added the EDL
cameras (EDLCAMs) to the project baseline. The EDLCAMs were delivered to ATLO in
the fall of 2019.
The EDLCAM system includes four new camera types, along with a rover chassis-
mounted microphone for recording audio. Three Parachute Uplook Cameras (PUCs) will
monitor parachute deployment. A Descent stage Downlook Camera (DDC) will record the
rover as it descends from the skycrane, while the Rover Uplook Camera (RUC) simultane-
ously records the descent stage as seen from the rover. The Rover Downlook Camera (RDC)
will image Mars as the rover touches down onto Mars. Video and audio from the EDLCAM
system will be relayed to Earth in the subsequent sols after the rover is safely on Mars. The
EDLCAM system was built with commercially available hardware, slightly modified for use
on Mars 2020, and integrated/tested at the Jet Propulsion Laboratory/California Institute of
Technology.
1.2.3 LCAM
The first camera sent to Mars for descent imaging was the Mars Descent Imager (MARDI),
which flew on the Mars Polar Lander (MPL) mission in 1998 (Malin et al. 2001). The MPL
spacecraft was lost during EDL and no image data were returned (Casani et al. 2000).
In 2004 the MER Descent Motion Estimation System (DIMES) system returned images
during EDL as part of a system to detect and remove excess horizontal velocity during EDL
(Johnson et al. 2007). The DIMES system acquired three images per rover at a rate of one
image every 3.75 seconds, using a modified Navcam camera as a descent imager (Maki
et al. 2003). The DIMES system successfully determined the horizontal velocity on both
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137 Page 6 of 48 J.N. Maki et al.
vehicles and triggered a successful velocity reduction on Spirit (no correction was required
on Opportunity).
In 2008 the Mars Phoenix mission flew a second version of the MPL MARDI to Mars,
along with a microphone. Phoenix MARDI data were not acquired during EDL due to last-
minute concerns that the data transfer from the camera to the lander might interfere with the
EDL system.
In 2012 the MSL Curiosity Mars Descent Imager (MARDI) successfully acquired images
during EDL (Malin et al. 2017). Although the Curiosity MARDI had heritage from the
earlier MPL and Phoenix MARDI designs, the Phoenix experience motivated a different
data handling architecture for MSL. Rather than relying on the spacecraft for the readout
and storage of MARDI images, the camera included its own non-volatile flash memory,
making data acquisition and storage independent of the spacecraft during EDL. The MSL
MARDI was developed along with the MSL Mastcam (Malin et al. 2017) and MAHLI
cameras (Edgett et al. 2012) and incorporates a number of other improvements relative to
the MPL and Phoenix versions of MARDI: a larger format (1600 ×1200 pixels), color
(Bayer pattern filter) detector, transform-based lossy image compression (Joint Photographic
Experts Group, JPEG) and a higher frame rate (∼4 frames/second). The Curiosity MARDI
improved the frame rate by 15×over the MER descent imager.
In 2016 the Mars 2020 project incorporated the Lander Vision System (LVS) system into
the Mars 2020 EDL design. A key component of the LVS is the LVS Camera (LCAM),
which acquires images of the surface during parachute descent. The LVS determines the
vehicle location by acquiring and correlating LCAM images to an onboard reference map.
The onboard map is generated using data from the Mars Reconnaissance Orbiter (MRO)
Context camera (CTX, Malin et al. 2007) and preloaded onto the vehicle prior to EDL.
The spacecraft uses the LVS localization to determine a landing target that avoids hazards
identified a-priori using MRO HiRISE (McEwen et al. 2007) imagery. The spacecraft flies
down to this safe target during the powered descent phase of EDL. LVS has heritage from
the MER Descent Motion Estimation System (DIMES) system. The technique employed by
the Mars 2020 LVS is called Terrain Relative Navigation (TRN).
The LCAM is required to acquire and send global shutter images immediately upon
command by the LVS with low time latency. Because these timing requirements could not be
met with any existing space-qualified flight imaging systems, Malin Space Science Systems
(MSSS) was selected to develop, build, and test a new system. LCAM has heritage from
the earlier MARDI designs, and also incorporates features of other MSSS imaging systems
(Ravine et al. 2016).
2 Instrument Objectives and Requirements
2.1 ECAMs
2.1.1 ECAM Objectives
The high-level objectives and requirements of the Perseverance engineering cameras are
largely unchanged from the original Spirit and Opportunity requirements. The Navcams are
designed to survey the terrain around the rover with a 360◦field of regard by acquiring im-
ages from atop a pan/tilt mast mounted on the top deck of the rover. Navcam images are
used for traverse planning, science target identification and selection, robotic arm operation,
and rover auto-navigation. Additionally, the Navcams will document the state of the vehicle
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The Mars 2020 Engineering Cameras Page 7 of 48 137
by acquiring images of rover hardware and determine the rover attitude in the local Mars
frame by acquiring images of the sun. The Hazcams are designed to image the areas imme-
diately fore/aft of the vehicle, particularly in areas that do not have Navcam coverage due
to occlusion by the rover body. The Hazcams support robotic arm operation and rover nav-
igation. They also support inspection of the front/rear wheels the contact interface between
the wheels and the terrain. The Cachecam will document the material in the sample tubes
during sample processing.
2.1.2 ECAM Requirements, Improvements over Previous Generations
The Perseverance engineering camera design upgrades were based on lessons learned from
rover surface operations on Mars, including the Spirit rover mission, active from 2004–
2010, the Opportunity rover mission, active from 2004–2018, and the Curiosity rover, active
from 2012 to present. Three primary limitations of the original MER/MSL designs have
emerged over the course of over 16 years of continuous rover operations on Mars. The first
is that the MER/MSL Navcam field of view (FOV) is too narrow to efficiently image the
Martian landscape around the rover. The second limitation is that the MER/MSL engineering
cameras provide a limited capability for the assessment of vehicle state and Martian terrain
due to lack of color information. The third limitation is that the low angular pixel scale of
the MER/MSL engineering cameras limit blind drive designations to approximately 40–50
meters and provide a limited ability to assess the state of vehicle hardware. The original
MER camera designs were designed for a 90-Sol nominal surface mission. By improving
on the original designs the Perseverance engineering cameras will help to improve mission
performance over predecessor missions.
2.1.3 Field of View
The MER/MSL Navcam FOV is 45◦×45◦at 0.82 mrad/pixel. While a relatively wide field
of view compared to Pancam (16◦×16◦at 0.27 mrad/pixel, Bell et al. 2003) or Mastcam
(20◦×15◦at 0.218 mrad/pixel, Malin et al. 2017), the MER/MSL Navcam FOV is too
narrow to allow simultaneous imaging of both the near field and far field terrain in a single
image. A total of 10 MSL Navcam images must be acquired to cover the full 360◦field of
regard. To cover both the near and far field terrain, two tiers of MSL Navcam panoramas (10
images wide ×2 images high) must be mosaicked together, creating image-to-image seams
at the interfaces between the images (Fig. 1). Parallax effects between adjacent overlapping
images within a panorama create imperfections within the final assembled mosaic.
The Perseverance Navcam field of view was chosen to be 90◦×70◦. The 90◦horizontal
FOV allows a 360◦Navcam panorama to be acquired with 5 overlapping images (compared
to 10 overlapping Navcam images on MSL). Additionally, the 70◦vertical FOV enables a
single Navcam image to cover the terrain from the area immediately near the rover all the
way out to the horizon. The larger Navcam FOV also requires less data volume to cover the
same terrain, saving between 5% and 10%, due to fewer overlap regions, as described in the
next section (Field of View, Image-to-Image spacing, and Mosaic Coverage Efficiency).
The Perseverance Hazcam FOV requirement was expanded slightly to >130◦horizontal,
compared to 124◦in the MER/MSL Hazcam design, to enable better coverage of the rover
wheels.
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137 Page 8 of 48 J.N. Maki et al.
Fig. 1 MSL Navcam mosaic. The mosaic as shown above covers a total field of approximately 90◦×70◦,
and required portions of 6 individual Navcam images (∼2.75 images wide by ∼1.75 images high) to cover
the field. The Perseverance Navcams will cover the same field of view in a single image. Reducing the
image-to-image overlap in a mosaic improves the quality of a mosaic by reducing the number of seams. The
reduction in overlap also reduces downlinked data volume by eliminating the redundant data in the overlap
regions
Field of View, Image-to-Image spacing, and Mosaic Coverage Efficiency When imag-
ing the terrain with a pan/tilt imaging system, the field of view of the camera is an important
consideration in determining the angular (azimuth/elevation) spacing between adjacent im-
ages. This image-to-image spacing is also called the center-to-center spacing, i.e., the dis-
tance between the centers of adjacent images. In the ideal case where objects are infinitely
far away from a perfect camera rotating about an idealized pinhole viewpoint, the center-
to-center distance can theoretically be exactly equal to 100% of the FOV of the camera. In
the case of a stereo pan/tilt system where the cameras rotate and translate about the pan/tilt
axes, parallax effects require that the spacing between adjacent images be less than 100%
of the FOV. Additionally, stereo coverage in a single stereo pair is not 100% due to par-
allax effects caused by the separation of the left/right eyes of a stereo pair. As a general
rule, a center-to-center spacing of 80% of the camera FOV robustly ensures sufficient stereo
coverage throughout an entire mosaic for virtually all scenes.
The spacing between the images in a mosaic can be expressed numerically with a spacing
factor αvariable multiplied by the FOV, where the value of αin this analysis ranges from
0.5 (50% spacing between images) to 1.0 (100% of the FOV) spacing between images).
The mosaic coverage efficiency (MCE) can be expressed as the ratio of the total number of
pixels acquired in a mosaic with spacing factor α, including redundant pixels in the overlap
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The Mars 2020 Engineering Cameras Page 9 of 48 137
Fig. 2 Individual image coverage efficiency of images within a 10 ×1, 360-degree mosaic with spacing
factor α=0.8. The total cumulative mosaic coverage efficiency is shown in Fig. 3
regions, divided by the number of pixels in the same mosaic with no overlap (α=1). For
the case of a single mosaic image (N =1), the MCE is 100%.
The equation for the MCE of a partial 360◦single tier mosaic containing nimages (n×1)
each with areal coverage Ais:
MCEpart ial =A1+α(A2+A3+···+An)
A×n
where A1,A2,A3, etc. are the individual areal coverages of each image in the mosaic (ig-
noring parallax effects) and αis the spacing factor.
Because the areal coverages are the same, the above equation simplifies to:
MCEpart ial =1+α(N −1)
N
In the case of an idealized full 360◦mosaic, ideally spaced so that nimages fit symmetrically
into a 360◦panorama and the last (nth) image overlaps the first, the MCE is:
MCEfull 360 =A1+α(A2+A3+···+An−1)+An(2α−1))
A×n
In the above equation, the first image, A0has 100% efficiency (no overlap), while subsequent
images have an efficiency of α. The very last image in a 360-degree mosaic is the least
efficient, with an efficiency of 2α−1 due to the fact that it is wrapping around to the first
image in mosaic and thus covering redundant areas on both sides of the image, as shown in
Fig. 2. This is equivalent to all of the images having an efficiency equal to α,andtheabove
equation can be simplified to show that the MCE of a full 360-degree mosaic is equal to the
spacing factor:
MCEfull 360 =α
One interesting result from this analysis is that the MCE for an idealized, complete 360◦
single-tier mosaic is equal to the spacing factor αregardless of the FOV of the camera.
A small FOV camera will have many seams, but as long as the panorama covers 360◦it will
have the same mosaic coverage efficiency as a large FOV camera. Conversely, for partial
panoramas, a camera with a wider FOV will generally give higher mosaic coverage efficien-
cies than smaller FOV cameras. The above analysis is idealized, but the results are generally
the same, even for non-idealized panoramas.
The plot in Fig. 3shows how the mosaic coverage efficiency for a single tier MSL Nav-
cam mosaic starts at 100% for the first image, decreases to 90% for the 2 ×1 mosaic, 86.7%
for the 3 ×1, and so on, finally dropping to αas the mosaic forms a complete 10 ×1, 360◦
panorama. Figure 4shows a MCE plot for a 5 ×1, 360◦Mars 2020 Navcam panorama.
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137 Page 10 of 48 J.N. Maki et al.
Fig. 3 Mosaic coverage
efficiency for an MSL 10 ×1
Navcam 360◦mosaic, plotted as
a function of the number of
images (horizontal FOV =45◦,
α=0.8, m=10). The variable m
represents the number of images
required for a full 360◦mosaic
Fig. 4 Mosaic coverage
efficiency for a Perseverance
5×1 Navcam 360◦Navcam
mosaic, plotted as a function of
the number of images (horizontal
FOV =90◦,α=0.8, m=5).
The variable mrepresents the
number of images required for a
full 360◦mosaic
With the same αvalue of 0.8, the MCE values for the Mars 2020 Navcam are identical to
the MSL Navcam values for the first 4 images. The fifth image in the Mars 2020 Navcam
completes the 360◦panorama, which drops the MCE for the full 5 ×1 panorama to 0.8,
while the efficiency of the 5 ×1 MSL Navcam panorama is 84%. The difference however
is that the MSL Navcam panorama only covers 180◦, while the Mars 2020 panorama covers
the full 360◦. This is more easily shown in Fig. 5, which compares the MCE values of four
different camera FOVs.
By increasing the FOV of the Navcam from 45◦(MSL) to 90◦(Perseverance), the mosaic
coverage efficiency improves across the whole range of azimuths. Of particular interest are
the partial panoramas covering between 90◦and 180◦, which are often acquired as part
of a drive direction or arm workspace images. For these types of panoramas, the mosaic
coverage efficiency for the Perseverance Navcams is typically 90%, compared to ∼85%
for the corresponding MSL Navcam. For panoramas less than 90◦,thePerseverance MCE
values are 100%, compared to the comparable Navcam MCE values of ∼90%.
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The Mars 2020 Engineering Cameras Page 11 of 48 137
Fig. 5 The MCE for several
camera types, plotted as a
function of azimuth. For
coverage less than 360◦,awider
FOV camera will have a higher
mosaic coverage efficiency than a
camera with a smaller FOV. The
variable mrepresents the number
of images in a full 360◦mosaic
The higher Perseverance Navcam efficiency results in a typical data volume savings of
approximately 5% when compared to the MSL Navcams. When tallied over the entire nom-
inal mission, such a data volume savings corresponds to the equivalent of several thousand
Navcam images.
The MCE analysis can be extended into two dimensions with a similar conclusion: cam-
eras with wider fields of view use downlink bandwidth more efficiently than narrower FOV
cameras when acquiring partial panoramas.
In addition to better mosaics with higher coverage efficiency, the wider Perseverance
Navcam FOV means that the onboard navigation software (visodom and autonav) only needs
a single stereo Navcam image acquisition rather than the 3 stereo Navcam images required
on MSL. This allows the Perseverance Navcams to be pointed once and left there during a
drive, saving actuator usage, Remote Sensing Mast (RSM) slew time, and image acquisition
time. This time savings can instead be spent directly on rover driving, which improves drive
distance per sol.
2.1.4 ECAM Pixel Scale
The MER/MSL Navcams have a pixel scale of 0.8 milliradians/pixel at the center of the
FOV, and the MER/MSL Hazcams have a pixel scale of 2.1 milliradians/pixel at the center
of the FOV. While these pixel scales are sufficient for basic context and planning, the limited
MSL Navcam pixel scale prevents drive planning beyond approximately 50 meters on MSL,
depending on the terrain. Additionally, the ability to resolve details of rover hardware with
the MSL Navcams is often insufficient, particularly when imaging the turret hardware on the
robotic arm. During surface operations the Curiosity rover engineering team often requests
images from the Mastcams, with a pixel scale of 0.218 mrad/pixel, for drive planning (Fig. 6)
and engineering inspection of hardware. The Perseverance Navcams and Hazcams were
required to have pixel scales of ≤0.4 mrad/pixel to allow better drive planning and hardware
inspection capabilities.
ECAM Color The MER/MSL engineering cameras acquire single-channel greyscale im-
ages, with a visible bandpass covering 600–800 nm. The lack of color information often
hampers the ability of ground operators to assess the state of the vehicle during surface
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137 Page 12 of 48 J.N. Maki et al.
Fig. 6 Drive direction imaging with the MSL Navcams (greyscale, 0.8 milliradians/pixel) and the left Mast-
cam (color, ∼0.2 mrad/pixel, inset in top image, and bottom image). The Perseverance Navcams have a pixel
scale of ∼0.3 mrad/pixel
Fig. 7 Distinguishing two types of Martian material against metallic surfaces is challenging when using
only luminance information (left), while the same assessment is relatively straightforward with 3-channel
color (right). This image is from the MSL Mastcam (Malin et al. 2017). All of the Perseverance engineering
cameras are color cameras
operations. One particularly challenging area involves assessing the level of dustiness of
rover hardware. When assessing the quantity of dust, soil, and drilled rock material against
anodized aluminum and other shiny metallic surfaces, the use of grayscale images for this
assessment is challenging even for experienced human operators (Fig. 7).
Color also improves the ability of operators and algorithms to distinguish between terrain
types, in particular areas that contain dust and soil versus areas that contain more rocky
materials. Because Martian soil/dust is a distinct yellowish brown in color (Huck et al. 1977;
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The Mars 2020 Engineering Cameras Page 13 of 48 137
Maki et al. 1999), it is readily identified in color images in ways that are not possible with
greyscale images (Maki et al. 2018). Because of this advantage over grayscale, all of the
Perseverance engineering camera designs were required to have color (RGB) detectors.
2.1.5 Other ECAM Design Considerations
As part of the Perseverance engineering camera design effort, all previous engineering cam-
era requirements from MER/MSL were either to be met or exceeded. During the design
phase, the MER/MSL cameras were used as the minimum performance threshold, with the
performance of the new ECAMs being capabilities-driven above that threshold, within a
project-defined cost constraint.
Interface As part of the upgrade to the next-generation designs, one of the key require-
ments on the Perseverance engineering camera design was that it maintain near 100% com-
patibility with the heritage MER/MSL interface, including electronics interface, data, power,
and mechanical interface. This was driven by the fact that the engineering camera interface
card inside the rover body is a build-to-print copy of the MSL card. Memory inside the
Perseverance Rover Compute Element (RCE) is also unchanged. This constraint drove the
design of the Perseverance ECAM tiling scheme, discussed in detail in Sect. 3.ThePerse-
verance ECAM design team was given the goal of designing a camera that was as close to
“plug and play” compatible with the MSL and MER interfaces as possible.
Thermal The MER/MSL camera thermal design isolated the camera head electronics
from the focal plane array electronics by placing them in separate housings/boxes, in an
effort to minimize the amount of energy required to heat the cameras. During surface op-
erations use however, the energy required to heat the engineering cameras on MER/MSL
was negligible. In fact, the MER/MSL engineering camera thermal design was so efficient
that it created overheat risk due to the fast warmup of the cameras when the camera heater
switches were turned on. Because of this lesson learned the Perseverance ECAM thermal
design combines the camera head electronics and focal plane array electronics into a single
mechanical package, thermally isolated from the bracket/mounting interface using titanium
standoffs. Unlike the focal planes used in the MER/MSL cameras, the Perseverance ECAM
focal planes are operated in the same temperature range as the main camera electronics.
The electronics boards for the Perseverance ECAMs are thermally coupled to the camera
housings. This thermally isolates the electronics from the mounting brackets and reduces
the amount of energy required to heat the electronics to operating temperature. A relatively
small amount of energy is required to energize the film heaters on the exterior of the camera
housings, which heats the enclosure and ultimately the electronics.
2.2 EDLCAMs
2.2.1 EDLCAM Objectives
The objectives of the EDLCAM imaging system are to record key events during EDL. The
first event, parachute deployment, will be recorded by three Parachute Uplook Cameras
(PUCs). The PUCs will record the deployment, inflation, and operational dynamics of the
parachute from just prior to mortar fire until backshell separation. The second event, sky
crane deployment, will be recorded by the Descent stage Downlook Camera (DDC) and the
Rover Uplook Camera (RUC). The DDC will record rover dynamics and ground interaction
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137 Page 14 of 48 J.N. Maki et al.
Fig. 8 Location, approximate boresight location and direction, and notional image examples for the EDL-
CAMs
with the sky crane plume through touchdown. The RUC will record the descent stage dy-
namics through touchdown as seen from the rover and will also capture the flyaway of the
sky crane. The sixth camera, the Rover Downlook Camera (RDC), will capture the rover
dynamics and plume interaction with the ground as the rover touches down onto Mars.
Additionally, the EDLCAM system includes a microphone, designed to capture acoustic
events from parachute deploy to touchdown. Figure 8shows the locations and notional fields
of view of the cameras. The EDLCAM recording phases are shown in Fig. 9.
2.2.2 EDLCAM Requirements
The EDLCAMs were developed with a minimal number of key requirements. The first re-
quirement was that the EDLCAMs must not interfere with the flight system during the crit-
ical EDL phase of the mission. This requires that the EDLCAM imaging system have zero
or near zero interaction with the MSL-heritage flight system elements during EDL. Data
for the EDLCAMs must be stored offline from the main rover computer during EDL, to
be retrieved after the vehicle is safely on the surface, much in the same way that the MSL
MARDI cameras operated (Malin et al. 2017). The EDLCAM system was specifically de-
signed to not impose significant changes to heritage hardware or software on the MSL flight
system. The frame rates for the camera video were driven by a minimum frame rate require-
ment of 30 frames per second (fps) for parachute imaging. All other EDLCAM performance
attributes are capabilities driven. The EDL camera system was categorized as a technology
demonstration during development, and the system uses a significant amount of commer-
cially available hardware, qualified and modified for EDL use.
2.3 LCAM
2.3.1 Objectives
LCAM will acquire images during the parachute descent stage of EDL for the LVS. Fig-
ure 10 shows how LCAM images are matched to a basemap during EDL.
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The Mars 2020 Engineering Cameras Page 15 of 48 137
Fig. 9 EDLCAM recording sequence, showing the approximate coverage of the data acquisition phases of
the EDLCAM system. The acquisition frame rates of the cameras are listed in frames per second (fps), and
the acquisition durations are listed on the bottom. The PUC frame rate listed in the yellow box is 75 fps
2.3.2 LCAM Requirements
The key LCAM requirements were for a field of view 90◦by 90◦, a format of 1024 by 1024
pixels, a detector with a global shutter, a frame latency of less than 100 ms between the
camera image trigger and the last pixel output of the image, a frame rate of up to 2 Hz, and
SNR of >80:1 with ∼1 millisecond exposure time under Martian illumination conditions.
3 Instrument Description and Performance
3.1 ECAMs
All of the Perseverance engineering cameras share the same detector and camera body de-
signs. This approach helps reduce development costs and greatly simplifies integration and
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137 Page 16 of 48 J.N. Maki et al.
Fig. 10 LCAM images are used by LVS to match features against a basemap. These feature matches are sent
to an Extended Kalman Filter (EKF) that estimates the vehicle position. The vehicle attitude is propagated by
an Inertial Measurement Unit (IMU). For details on the LVS see Johnson et al. 2017. Figure from Johnson
et al. 2017
test activities, the software and image processing architecture, and camera operation. Ta-
ble 2lists the characteristics of the Navcam, Hazcam, and Cachcam cameras. A total of
23 cameras were built in the Perseverance engineering camera production run, including
9 flight model units (FM), 9 engineering model (EM) units, 4 flight spare (kits), and one
qualification model (QM). The ECAM lenses were designed and manufactured by Jenoptik.
3.1.1 Detector
The Perseverance engineering cameras use a CMV-20000 detector (Fig. 11), a global shut-
ter CMOS (Complimentary Metal Oxide Semiconductor) device with 5120 ×3840 pixels,
built by AMS (formerly CMOSIS). The image array has 6.4micron×6.4 micron sized
pixels, digitized at 12 bits/pixel. The detector has a full-frame optical size of 32.77 mm by
24.58 mm with a Bayer pattern color filter array (Bayer 1976). The CMV-20000 was chosen
due to the large optical format, the relatively high dynamic range, and high frame rate ca-
pability. The Perseverance engineering cameras have a commandable exposure time range
of 410.96 microseconds to 3.277161 seconds, in 50 microsecond steps. The detector has
been radiation tested to 20 kRad, RDF (Radiation Design Factor) =2 and meets total dose
mission performance requirements.
3.1.2 Electronics
The camera electronics consist of 3 electronics PWBs (printed wiring boards) connected via
rigid flex polyimide film layers built into the inner layers of the boards. This integrated ap-
proach simplifies the design and manufacturing, and follows the approach used on MER and
MSL. The three PWBs are folded into the camera body mechanical housing. The electron-
ics are connected to the rover interface using a 37-pin microD connector. Figure 12 shows
the functional block diagram for the ECAM electronics. The pixel transfer rate between the
camera and the RCE was increased to 500,000 pixels/second without changing the heritage
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The Mars 2020 Engineering Cameras Page 17 of 48 137
Tab l e 2 Perseverance Navcam, Hazcam, and Cachecam characteristics
Navcam Hazcam Cachecam
Horizontal FOV 96◦136◦∼50 mm diameter circle
at the plane of focus
Vertical FOV 73◦102◦
Diagonal FOV 120◦172◦
Focal ratio f/12 f/12 N/A
Focal length 19.1 mm 14.0 mm 0.51 magnification
(measured)
Best focus 3.5 meters 0.9 meters ∼140 mm below
illuminator mirror and
∼130 mm below exit
aperture window
Depth of field ±5mm
Pixel scale
(centerofFOV)
0.33 mrad/pixel 0.46 mrad/pixel ∼12.5 microns/pixel at
plane of focus
Mass
(per camera)
411 grams 498 grams 397 grams (camera)
398 grams (vision station)
Volume 74 mm ×88 mm ×125 mm 74 mm ×88 mm ×140 mm 74 mm ×88 mm ×143 mm
Stereo baseline 42.4 cm Front: 24.8 cm N/A
Rear: 93.4 cm
Angle between
left/right
boresights
<0.4◦(parallel) Front: 20◦N/A
Rear: <1◦(parallel)
Boresight
mounting
orientation
Mounted to pan/tilt RSM,
left/right camera boresights
are parallel
Front: 28◦below nominal
horizon, left/right cameras
are canted outward by 10◦
each
Pointed downward inside of
the ACA. Samples are
brought up to the vision
station by the SHA (Sample
Handling Assembly)
Rear: 45◦below the
nominal horizon, left/right
camera boresights are
parallel
Height above
nominal surface ∼1.98 meters when
viewing horizon
0.73 meters 0.73 meters
Detector characteristics
Pixel format 5120 ×3840
Pixel pitch 6.4µm×6.4µm
Optical format Full frame (32.77 mm ×24.58 mm)
Pixel type Global shutter with correlated double sampling
Shutter type Pipelined global shutter
Full well 15,000 e-
Pixel dark noise 8 e- RMS
Conversion gain 0.24 DN/e-
Readout time 237 milliseconds
Exposure time (commandable) 410.96 microseconds to 3.277161 seconds, in 50 microsecond steps using
autoexposure algorithm from Maki et al. (2003)
Responsivity 0.29 A/W @ 55 nm with microlenses
Maximum SNR 41.8 dB
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137 Page 18 of 48 J.N. Maki et al.
Tab l e 2 (Continued)
Detector characteristics
Dynamic Range 66 dB
Color Filters RGB Bayer color filter array (CFA)
QE 64.5% @ 55 nm with microlenses
Camera interface to rover
Command and data interface LVDS
Protocol MER/MSL
Power Input +4.3 Volts to +5.9 Volts
Data Rate 500,000 pixels/second
Power 3 Watts (single camera, imaging mode)
1 Watt (single camera, idle)
Memory 1 Gbit SDRAM
FPGA MicroSemi Rad-Tolerant ProASIC3
Radiation Tolerance 20 kRad TID, RDF =2
Temperature Range −55 ◦Cto+50 ◦C (operational)
−135 ◦Cto+70 ◦C(survival)
Fig. 11 A CMV-20000 detector undergoing prototype testing in 2014 at JPL. The active imaging area is
32.77 mm ×24.58 mm
LVDS clock rate by inserting less space between pixel waveforms. The MER/MSL pixel
transfer rate is ∼200,000 pixels per/second.
3.1.3 Hazcams
The Hazcam lenses have a focal ratio of f/12 and a best focus distance of approximately
0.9 meters, optimized for the robotic arm workspace and views of the rover wheels. Each
Hazcam lens assembly contains 10 individual lens elements and a fused silica UV and IR
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The Mars 2020 Engineering Cameras Page 19 of 48 137
Fig. 12 Perseverance camera electronics block diagram
blocking filter mounted inside the lens assembly between the third and fourth elements. The
cameras are body-mounted to the fore and aft of the rover. The FOV of the Hazcams is
136◦(horizontal) by 102◦(vertical), with a 173◦diagonal. Figure 13 shows a set of flight
Hazcams.
Front Hazcams There are four Hazcams hard-mounted to the rover front chassis (Fig. 14).
The Front Hazcams form two stereo pairs: one pair is connected to RCE-A, and the second
pair is connected to RCE-B. The Front Hazcam stereo baseline for each pair is 24.8 cm;
the A/B cameras are interleaved to maximize the stereo baseline between the left and right
cameras. The Front Hazcams are pointed downward 28◦from the nominal horizon to allow
better coverage in the area immediately in front of the rover. Additionally, the left and right
Front Hazcam boresights are each angled outwards by 10◦(the left cameras are angled 10◦
to the left and the right cameras are angled 10◦to the right) to allow better viewing of the
rover wheels.
The Front Hazcams have a sun visor mounted above the cameras to prevent sunlight from
falling directly onto the lenses. This helps reduce lens flare and other scattered light artifacts.
To maximize sun shading during late afternoon imaging the visor extends into the top of the
camera FOV slightly. These upper regions of the FOV will typically be cropped (subframed)
out of the image before being sent for downlink.
The Front Hazcams are protected during EDL by a camera cover assembly. The camera
covers have transparent Lexan windows, which allow useable images to be acquired while
the covers are closed. The covers are released shortly after touchdown on Mars using a
non-explosive actuator (NEA). Once released, the covers flip open using a spring loaded-
mechanism and stay in the open position for the remainder of the mission.
Rear Hazcams There are two Hazcams mounted on the rear of the rover, one on each side
of MMRTG (Multi-mission Radioisotope Thermoelectric Generator). The stereo baseline
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137 Page 20 of 48 J.N. Maki et al.
Fig. 13 Flight Hazcam cameras
between the two Rear Hazcam cameras is 93.4 cm. Unlike the Front Hazcams, the Rear
Hazcams are connected to both RCEs. The Rear Hazcams are pointed 45◦below the nominal
horizon. Each of the Rear Hazcams has a deployable cover assembly similar in design to
the Front Hazcams. The Rear Hazcam covers are opened shortly after touchdown on Mars
in a similar fashion to the Front Hazcams. Unlike the Front Hazcams, the Rear Hazcams
do not have sun visors. Figure 15 shows a picture of the Rear Hazcams mounted on the
rover. The proximity of the Rear Hazcams to the RTG exposes these cameras to a slightly
higher radiation dose than the Navcams and Front Hazcams. Over the course of the prime
mission, the cumulative effects of radiation on the Rear Hazcam detectors will result in
higher dark current levels. Additionally, waste heat from the RTG warms the Rear Hazcams
by 10 ◦Cto20◦C relative to the Front Hazcams, further raising the Rear Hazcam dark
current levels. Both of these effects are also seen with the Curiosity rover Rear Hazcams. As
with the Curiosity Rear Hazcams, these effects are not expected to impact the useability of
the Perseverance Rear Hazcam images in any appreciable way during the prime mission. As
the dark current increases over time, operational considerations may be made to acquire Rear
Hazcam images during the cooler times of the day to reduce thermal dark current effects.
3.1.4 Navcams
The Navcam lenses have a focal ratio of f/12 and a best focus distance of approximately
3.5 meters. Each lens assembly contains six individual lens elements and a fused silica UV
and IR blocking filter mounted between the powered elements and the detector. The Navcam
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The Mars 2020 Engineering Cameras Page 21 of 48 137
Fig. 14 Perseverance Front Hazcams. L =left, R =right, A =RCE-A, B =RCE-B. Also shown are the
Left/Right Navcams
Fig. 15 Perseverance Rear Hazcams
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137 Page 22 of 48 J.N. Maki et al.
Fig. 16 Flight Navcam cameras
field of view is 96◦(horizontal) by 73◦(vertical), with a diagonal FOV of 120◦. The Navcam
cameras are shown in Fig. 16. The Navcams are mounted to the underside of the camera plate
on the Remote Sensing Mast (RSM) (Fig. 17).
3.1.5 Cachecam
The Cachecam has a fixed focus, 0.51 magnification lens with a depth of field of ±5mmand
a pixel scale of 12.5 microns/pixel. The Cachecam FOV forms a 50 mm diameter circle at the
plane of focus. The Cachecam lens contains six individual lens elements. The Cachecam has
no IR blocking filter because the LED illuminator has no output in the IR. At the end of the
lens is an integrated illuminator assembly, which contains a mirror that redirects incoming
light at an angle of 90◦. The front of the illuminator is sealed with a fused silica window.
The illuminator has a set of three light emitting diodes (LEDs) which allow the sample to
be illuminated during imaging. The LEDs are powered whenever camera power is applied.
The LEDs are made by Luxeon, part number LXZ1-4070, are white light LEDs with a CCT
(correlated color temperature) of 4000 K.
Figure 18 shows the flight Cachecam camera. The Cachecam is integrated into a sub-
assembly called the Vision Assessment Station (Fig. 19). The Vision Assessment Station
(VAS) contains a cylindrical shaped baffle sub-assembly. The VAS is placed into a larger
assembly, the Adaptive Cache Assembly (ACA), which is inside the rover body (Fig. 20).
Due to the small depth of field of the Cachecam, the sample tube must be moved in and
out of the plane of focus of the camera in small mm-sized vertical steps, with an image
acquisition occurring at each step. The small depth of field was chosen to help estimate
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The Mars 2020 Engineering Cameras Page 23 of 48 137
Fig. 17 Closeup view of the Navcams mounted on the Remote Sensing Mast (RSM), a pan/tilt mast that
points the cameras to targets of interest. The Navcams have a 42.4 cm stereo baseline. Also shown in the pic-
ture are the Mastcam-Z cameras (Bell et al. 2020, this issue) located between the Navcams, and the SuperCam
(Wiens et al. 2020, this issue), located above the Navcams
the height of the sample in the sample tube. The movement of the tube is done with the
Sample Handling Assembly (SHA) robot arm. The SHA robot arm brings the tube over
to the Vision Assessment Station and moves the sample tube through focus. The resulting
set images form a Z-stack data set. The individual images are downlinked to Earth and
processed. Information about the sample is extracted from this data set, including sample
depth within the tube, sample texture, and estimates of the sample volume.
3.1.6 Camera Hardware Processing
ECAM Readout Modes The MER/MSL camera data interface supports an image size of
1024 ×1024 pixels, and the available image buffer sizes in the RCE RAM are limited to the
MER/MSL heritage sizes. In order to use the heritage interface and memory allocation, a 20
Megapixel Perseverance ECAM image must be sent to the rover as a series of smaller sub-
images (tiles). After an ECAM camera acquires an image, it stores the entire 20 Megapixel
image temporarily in camera memory and returns individual, smaller sub-images to the rover
upon command. The individual sub-image tiles are nominally 1280×960 pixels in size, and
a total of 16 tiles must be transferred to copy an entire 5120×3840 pixel image into the rover
computer. Smaller-sized sub-image tiles can be requested if desired. Larger tiles can also be
requested, but they cannot be larger than 1296 ×976 pixels due to memory limitations in
the RCE. The tile starting location can be arbitrarily placed within an image as long as the
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137 Page 24 of 48 J.N. Maki et al.
Fig. 18 Flight Cachecam camera assembly, including the lens, illuminator, and camera body. This photo
shows the view looking directly into the Cachecam entrance aperture
entire tile fits within the boundaries of the larger image and the starting locations are even
multiples of 8.
The Perseverance cameras are also capable of reducing the pixel scale of an image prior
to transmission by performing a pixel summing operation. There are four possible pixel
scales available: full-scale (1 ×1, or no spatial downsampling), half-scale (2 ×2 spatial
downsampling), quarter-scale (4 ×4 spatial downsampling), and one-eighth scale (8 ×8
spatial downsampling). In all modes the resulting subimage tiles are nominally 1280 ×960
pixels, with the exception of the 8 ×8 downsampling mode, which always produces 640 ×
480 pixel images.
In addition to spatial downsampling modes, the Perseverance ECAMs also allow the sep-
arate readout of individual red, green, and blue color channels. Depending on the requested
mode, the camera either subsamples the Bayer cells by sending only the requested color,
or it averages all of the pixels of the same color together. The camera can also average all
of the pixels together and return a panchromatic image. In the 8 ×8 mode, the camera al-
ways returns a panchromatic image by averaging all 64 pixels together into a single pixel.
Tabl e 3lists all 10 available hardware processing modes, and Fig. 21 depicts the modes
schematically.
Image Co-adding The ECAM hardware allows in-camera co-adding of 2, 4, 8, or 16 im-
ages to improve the signal to noise ratio of the image. This capability may be useful when
imaging shadowed surfaces and acquiring images under low-light conditions such as night-
time imaging of the surface, nighttime atmospheric imaging, and astronomy observations.
During a co-add operation, the camera exposes an image, adds it to an image accumulator
buffer, acquires the next image, and continues until the desired number of images have been
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The Mars 2020 Engineering Cameras Page 25 of 48 137
Fig. 19 The Perseverance Vision Assessment Station, which includes the Cachecam camera and cylindrical
baffle. Sample tubes are presented to the camera by a Sample Handling Assembly (SHA), a small robot
arm that brings sample tubes into the baffle from the bottom (the SHA is not shown in this picture). The
illuminator assembly contains 3 LEDs that shine down onto the sample tube from the top. The camera looks
down into the tube and acquires images of the top of the material within the tube
co-added. In all cases the camera returns the final co-added image and discards the interme-
diate images. During the transmission of the image data to the RCE, the camera divides the
image by the number of co-added images by performing a bit-shift operation and returning
the most significant 12-bits of the co-added pixel data.
3.2 EDLCAMs
3.2.1 EDLCAM Cameras
The EDLCAM camera bodies were manufactured by FLIR (formerly Point Grey). They
have CS type lens mounts, which mate with custom lenses designed and manufactured by
Universe Kogaku America. The PUC, RUC, and RDC lenses are identical in design and
each contain 6 lens elements, including a front window, have a focal ratio of f/2.8, and a
focal length of 9.5 mm. The DDC lens assembly contains 7 lens elements, including a front
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137 Page 26 of 48 J.N. Maki et al.
Fig. 20 Location of the Cachecam within the Adaptive Caching Assembly (ACA), looking upwards from
below the rover chassis. A portion of the Front Hazcam cover mechanism spring assembly can be seen in the
upper right of the image
Tab l e 3 The 10 available color/pixel scale readout modes for the Perseverance ECAMs
Mode Sub-image pixel scale Sub-image tile size (pixels) Description
01×1 1280 ×960 RGB, Raw Bayer pattern
12×2 1280 ×960 2 Green Pixel Average ( G
2)
22×2 1280 ×960 Red Pixel Subsample
32×2 1280 ×960 Blue Pixel Subsample
42×2 1280 ×960 4 Pixel RGB Average ( R,G,B
4)
54×4 1280 ×960 8 Green Pixel Average ( G
8)
64×4 1280 ×960 4 Red Pixel Average (R
4)
74×4 1280 ×960 4 Blue Pixel Average (B
4)
84×4 1280 ×960 16 Pixel RGB Average ( R,G,B
16 )
98×8 640 ×480 64 Pixel RGB Average ( R,G,B
64 )
window. The DDC lens has a focal ratio of f/5.6 and has a focal length of 8 mm. See Table 4
for a summary of the EDLCAM camera types. The EDLCAM hardware is shown in Fig. 22,
and the locations of the DDC, RUC, and RDC on the rover are shown in Figs. 23,24 and 25.
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The Mars 2020 Engineering Cameras Page 27 of 48 137
Fig. 21 Schematic representation of the 10 available ECAM readout modes: a) full-scale (1 ×1, upper left),
b) half-scale (2 ×2, upper right), c) quarter-scale (lower left), and d) 1/8th scale (lower right). In modes 0
through 8, all image tiles returned from the cameras are nominally 1280 ×960 pixels in size. In mode 9 the
image tiles are 640 ×480 pixels in size. In the above figure the 1 ×1and2×2 tiles are shown aligned on
even multiples of 1280 ×960 for simplicity. In actuality the location of tiles can be located anywhere on the
sensor as long as the entire tile is inside the larger source image and the starting locations are even multiples
of 8
3.2.2 Microphone
The EDLCAM system contains an omnidirectional microphone capsule for the capturing of
sound during EDL. The microphone capsule was manufactured by DPA Microphones, part
number MMC4006. The microphone capsule is connected to a DPA digitizer electronics
board (part number MMA-A) that was repackaged into a custom aluminum chassis by the
EDLCAM hardware development team. The digitizer board has two audio channels but the
EDLCAM system only has one microphone capsule. The only key requirement on the mi-
crophone system was that it provided a simple interface to the EDLCAM DSU. The acous-
tic performance of the microphone system was not a key requirement – it has a frequency
response from 20 Hz to 20 KHz (±2 dB). The digitizer is connected to the EDLCAM sub-
system rover DSU via a USB2 connection. The microphone has a custom field grid that
was modified for the Martian acoustic environment. The grid controls the behavior of sound
waves on the diaphragm of the microphone while also minimizing the penetration of Martian
dust into the diaphragm. Figure 26 shows the microphone capsule and microphone digitizer
assembly. The microphone is mounted externally on the rover (Fig. 27).
Because the EDLCAM microphone is attached to the rover body, it will be commandable
after landing. If the microphone survives the diurnal temperature cycles, it could be used
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137 Page 28 of 48 J.N. Maki et al.
Fig. 22 EDLCAM flight hardware
Fig. 23 Location of the DDC on the descent stage
to record Martian ambient sounds on the surface, mechanism movements such as wheel
motions and coring operations, and other items of interest. The microphone could also be
used in collaboration with the SuperCam microphone described in Murdoch et al. (2019),
Chide et al. (2019), and Maurice et al. (2020).
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The Mars 2020 Engineering Cameras Page 29 of 48 137
Fig. 24 Location of the RUC on the rover
Fig. 25 Location of the RDC on the rover
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137 Page 30 of 48 J.N. Maki et al.
Fig. 26 The EDLCAM microphone (left, with bracket) and digitizer assembly (right). The microphone is
approximately 42 mm ×40 ×19 mm and weighs 52 grams. The digitizer assembly is approximately 56 mm
in diameter and weighs approximately 50 grams
Fig. 27 Location of the EDLCAM microphone on the Perseverance Rover. The microphone is located on
the port side (Y-axis, rover coordinate frame) of the rover body, above the middle wheel
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The Mars 2020 Engineering Cameras Page 31 of 48 137
Tab l e 4 EDLCAM properties and estimated operating modes
Item PUC (quantity 3) RUC RDC DDC
Horizontal FOV 35◦±3◦35◦±3◦35◦±3◦48◦±3◦
Vertical FOV 30◦±3◦30◦±3◦30◦±3◦37◦±3◦
Pixel scale ∼0.5 mrad/pixel ∼0.5 mrad/pixel ∼0.5 mrad/pixel ∼0.4 mrad/pixel
Focal ratio f/7 f/7 f/7 f/5.6
Focal length 9.5 mm 9.5 mm 9.5 mm 8 mm
Image Size (pixels) 1280 ×1024 1280 ×1024 1280 ×1024 2048 ×1536
Pixel Size 4.8 microns 4.8 microns 4.8 microns 3.45 microns
Camera type CM3-U3-13Y3C-CS CM3-U3-13Y3C-CS CM3-U3-13Y3C-CS CM3-U3-31S4C-CS
Detector On Semi P1300
(RGB color)
On Semi P1300
(RGB color)
On Semi P1300
(RGB color)
Sony IMX265
(RGB color)
Mass (with lens) 80 grams 80 grams 80 grams 140 grams
Expected Frame Rate
(and duration)
75 fps for parachute
deployment
(∼30 seconds)
30 fps
(∼140 seconds)
30 fps
(∼260 seconds)
12 fps
(∼75 seconds)
30 fps until
backshell separation
(∼98 seconds)
Estimated number
of total images
5,190 per PUC (×3) 4,200 7,800 900
Estimated total
number of images
from all cameras
28,470
3.2.3 Data Storage Unit (DSU)
In addition to six cameras and a microphone, the EDLCAM system includes two data stor-
age units (DSUs) and two USB3 hubs. The DSU is an off-the-shelf computer-on-module
(CoM) from CompuLab Ltd with an Intel Atom processor and solid-state memory. The
DSU runs the Linux operating system, along with additional software to communicate with
the EDLCAM sensors, perform the EDL data collection sequence, manage the data storage
and compress the collected data files. The DSU uses a high-density connector to provide
connectivity to the high-speed USB3, USB2, gigabit ethernet and SATA interfaces.
The main DSU is located inside the rover body. A second DSU, the descent stage DSU,
is located on the descent stage. In both DSUs the CoM is connected to a custom electronics
board that provides connectivity for all the USB devices. The two DSUs are almost identical
to each other and communicate with each other through a gigabit ethernet link. The rover
DSU includes a 480 GB solid-state flash memory drive (SSD) for data storage, provides a
gigabit Ethernet link between both DSUs, and implements the high-speed serial communi-
cation protocol to communicate to the rover computer.
The DDC streams data to the descent stage DSU over USB3, and the descent stage DSU
streams data back to the rover DSU in real time over the ethernet link. The three Parachute
Uplook Cameras (PUCs) connect to two USB3 hubs in series, which merge the USB3 stream
into one port on the rover DSU and also acts as a USB repeater, allowing the data signals to
travel beyond 5 meters. The RUC, RDC, and the microphone are USB2 devices and connect
directly to the rover DSU. After the rover touches down on Mars, data saved on the rover
DSU are available to be copied from the 480 GB NVM SSD into the RCE for subsequent
downlink. Figure 28 shows a functional block diagram of the EDLCAM system.
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137 Page 32 of 48 J.N. Maki et al.
Fig. 28 EDLCAM functional block diagram
3.2.4 Data Acquisition
A key feature of the design of the EDLCAM system is the requirement to not interfere with
the safety of the vehicle during EDL. To meet this requirement the communication lines
between the EDLCAM system and the rover are disabled at the hardware interface level
during EDL to prevent spurious signals. The EDLCAM system runs autonomously once
power is applied to the DSUs by the flight system. The application of power to the DSU
and cameras is driven by external EDL events, as sensed by the flight system. Because the
external triggering depends on the EDL system performance the exact number of images
expected from each of the cameras is unknown in advance and can only be estimated. See
Tabl e 4for the estimated number of images expected. The PUCs and DDC are jettisoned
with the backshell and skycrane, but the RDC, RUC, and microphone remain on the rover
and will continue to acquire data after touchdown.
PUCs The three PUCs start to acquire image data immediately before parachute deploy-
ment at a frame rate of 75 fps (frames per second). After 30 seconds the frame rate drops
to 30 fps until backshell separation, expected to occur approximately 98 seconds later. The
total number of expected PUC images is ∼5,190 images per PUC, or 15,570 total images.
DDC The DDC will start acquiring image data just before the rover separates from the
descent stage and continues acquiring data through rover touchdown on the surface. The
DDC acquires data at 12 fps for ∼75 seconds and is expected to acquire approximately 900
images.
RDC The RDC will start acquiring data just before heatshield separation and will continue
acquiring data through touchdown on the surface. The RDC acquires data at 30 fps for
approximately 260 seconds and is expected to acquire approximately 7,800 images.
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Tab l e 5 LCAM characteristics
Horizontal FOV 90◦
Vertical FOV 90◦
Diagonal FOV 118◦
Focal ratio f/2.7
Focal length 5.8 mm
Best focus 2 meters to infinity
Pixelscale 1.67mrad(2×2 summed pixels)
Mass 880 grams
Volume 82 mm ×102 mm ×154 mm
Boresight mounting direction -Z (pointed straight down)
Detector Type On Semiconductor Python 5000
Pixel format 1024 ×1024 pixels (2 ×2 summed mode), windowed from
a total format of 2592 ×2048 pixels
Pixel pitch 9.6 microns (2 ×2 summing of 4.8 micron pixels)
Optical format 9.83 mm ×9.83 mm
Pixel type global shutter with CDS
Full well 33,925 e- (effective with 2 ×2 summing, gain 1)
System noise 32.6 e-
Conversion gain 139.4 e-/DN (2 ×2 summing)
Maximum SNR 45 dB
Dynamic range 60 dB
Filter 480 nm to 720 nm
QE 55% peak
Command/data interface LVDS/ChannelLink
Voltages 4.25 V to 5.5 V
Data rate 480 Mbps video output
Power 3.7 Watts
Memory 32 Gbytes flash
FPGA MicroSemi Rad-tolerant (RTAX-SL)
Radiation tolerance TID RDF >10
Temperature range −25 ◦Cto+50 ◦C (operational)
−40 ◦Cto+70 ◦C(survival)
RUC The RUC will start acquiring data just before the rover separates from the descent
stage and continues acquiring data through rover touchdown on the surface. The RUC ac-
quires data at 30 fps for approximately 140 seconds and is expected to generate approxi-
mately 4,200 images.
Microphone The microphone will acquire data from immediately before parachute de-
ployment through post-touchdown. The expected data acquisition duration is approximately
287 seconds. The microphone records at a sampling rate of 48 kHz, digitized at 24 bits.
3.3 LCAM
The LCAM characteristics are listed in Table 5.
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137 Page 34 of 48 J.N. Maki et al.
Fig. 29 The LCAM flight unit,
just prior to delivery to ATLO
Fig. 30 Location of the LCAM on the rover
An image of the flight LCAM is shown in Fig. 29. Figure 30 shows the LCAM mounting
location on the Perseverance rover.
3.3.1 Optics
The LCAM lens is a 9-element, all-refractive lens with a nominal horizontal and vertical
FOV of 90 ×90 and an effective focal length of 5.785 mm. The nominal on-axis f/# is 2.7.
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The Mars 2020 Engineering Cameras Page 35 of 48 137
The LCAM lens was fabricated at Collins Aerospace with design support from Synopsys
Optical Design Services.
3.3.2 Detector
The detector is an On Semiconductor Python 5000, a global-shutter CMOS image sensor
with 2592 ×2048 ×4.8 µm pixels and on-chip 8-bit or 10-bit digitization. LCAM uses the
monochrome version of the sensor.
3.3.3 Electronics
The LCAM electronics design is derived from two previous camera designs by MSSS: the
VSS (Vision Sensor System) camera on the NASA Goddard Space Flight Center (GSFC)
Restore-L Mission and the P50 camera on the Naval Research Laboratory (NRL) Robotic
Servicing of Geosynchronous Satellites (RSGS) Mission. Both of these cameras used the On
Semiconductor Python 5000 detector. The LCAM electronics includes three printed circuit
assemblies: the Interface Adaptor (IFA), Digital Module (DM), and Focal Plane Assembly
(FPA).
The IFA connects to the LVS via a 25-pin Micro-D interface connector and commu-
nicates using asynchronous command and telemetry interface signals (LVDS), a discrete
LVDS trigger, and a ChannelLink video interface. The DM contains a Microsemi RTAX
FPGA and four NAND flash banks, which for LCAM are only used to store redundant
copies of non-volatile operating parameters. The FPA contains three Line Current Limiter
(LCL) modules that control the three power supplies to the sensor.
3.3.4 LVS Interface
In response to trigger signals, LCAM acquires each image, optionally sums it 2 ×2, and
transmits it to the Vision Compute Element (VCE) component of the LVS. Images are al-
ways summed 2×2 and sent with 8-bit pixel depth. The ChannelLink clock is run at 35 MHz
by default, with an optional mode at 17.5 MHz. Two pixels are sent in each ChannelLink
cycle.
4 Flight and Ground Software
4.1 ECAM Flight Software
The ECAM flight software runs in the RCE. The software is a copy of the MER ECAM
IMG software module described in Maki et al. (2003), Litwin and Maki (2005), modified
for MSL (Maki et al. 2012), and subsequently modified for Mars 2020. The flight software
handles camera control, command handling, and the post-processing of camera images after
they are transferred over to the RCE. The software is mostly identical to the MER/MSL
versions, and because of this the reader is referred to the above manuscripts for a more
detailed description. Key changes for Mars 2020 are described here.
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137 Page 36 of 48 J.N. Maki et al.
4.1.1 Image Acquisition and Readout
Perseverance ECAM images are exposed using either manual or auto exposure, using the
methods described in Maki et al. (2003). On Mars 2020 the resulting full-scale image re-
mains stored in camera memory until a new image is acquired or the camera is powered
off. As described in Sect. 3.1.6,thePerseverance engineering cameras do not send back the
entire 5120 ×3840 pixel image in a single image transfer due to limitations available RAM
for image buffers. Instead, image data are sent back in nominally-sized 1280 ×960 pixel
sub-images (tiles). In order to read out a full-scale image, 16 individual image acquisition
commands must be sent to the camera, with each command resulting in the transfer of a
single 1280 ×960 pixel image tile to the RCE. The 16 individual image tiles are saved as 16
separate files and sent back to Earth. The individual image files are reassembled back into
the original full-scale image using ground software.
The image tiling architecture imposes a requirement that the image acquisition com-
mands must distinguish the difference between exposing the sensor and reading out a
previously-exposed image from camera memory. The Mars 2020 ECAM flight software
accommodates this difference by repurposing the “NONE” exposure type from MER and
MSL. On the MER/MSL rovers, an exposure type of NONE would power on the cameras
and prepare for acquisition, perform any necessary pan/tilt pointing if applicable, but not ac-
quire an image. On Perseverance, the NONE exposure type is used to perform the transfer
of an image tile from a previously-exposed image. The flight software supports two modes
of camera hardware operation: 1) acquire an image and immediately transmit a tile, and
2) transmit a tile from the current image in camera memory without re-exposing the sensor.
Full-scale image acquisition with the Mars 2020 IMG FSW will typically be performed
in the following way: the first IMG_ACQUIRE command will request an exposure type of
AUTO, in camera mode 6, which corresponds to a 4×4 downsampled, full FOV, red channel
image. This will expose the sensor to the scene of interest using autoexposure over the full
field of view. The exposure command would be followed by 16 subsequent IMG_ACQUIRE
commands, each requesting an exposure type of NONE (readout only) in mode 0, which
would transmit a full-scale image tile (1×1 downsampling, Raw Bayer) from camera mem-
ory into the RCE.
Alternatively, a user may require that the 16 image tiles be autoexposed individually. This
would be performed by requesting 16 separate autoexposure commands, each with different
tile coordinates. The FSW allows any of the 10 available camera hardware modes to be used
for tile readout. Autoexposure can be run using any of the 10 available readout modes. This
enables the autoexposure of an image based on a single color channel in the 2 ×2and4×4
modes. Images can also be autoexposed in all color channels individually. Alternatively,
a single panchromatic autoexposure could be used to set the exposure time for the image,
with a subsequent readout of the red, green, and blue channels. A detailed discussion of
exposure strategies is beyond the scope of this manuscript, but it is expected that different
use cases will employ different exposure and readout strategies.
4.1.2 Image Compression
In addition to the ICER wavelet and LOCO compression used in Maki et al. (2003)and
described by Klimesh et al. (2001) and Kiely and Klimesh (2003), the Perseverance IMG
module inherits a lossy JPEG (Joint Photographic Experts Group) compressor from the Mars
InSight lander imaging system (Maki et al. 2018). ICER and LOCO support 8-bit or 12-
bit pixels. The JPEG compressor supports both greyscale and color image compression,
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The Mars 2020 Engineering Cameras Page 37 of 48 137
selectable compression quality, and selectable chroma subsampling for color images. The
JPEG code supports 8-bit pixels only. The JPEG code is originally from the Independent
JPEG Group (http://ijg.org) modified by InSight to run in the VxWorks environment. Mars
2020 inherited the JPEG code from InSight.
Color images are typically compressed using color JPEG compression, although the FSW
allows the individual color channels to be compressed separately if desired. Compressing
individual color channels separately is done via greyscale compression (ICER or JPEG) on
each of the individual channels, and incurs a significant (∼3×) data volume penalty over
JPEG color compression. JPEG color compression is much more efficient: most of the com-
pressed data volume of a color JPEG image (typically 90% or more) is the luminance data,
with the color data comprising 10% or less of the total volume. In some cases, when a high-
quality, full-scale image is desired, the raw Bayer pattern can be compressed using LOCO
lossless compression. The FSW allows many combinations of acquisition and compression
to cover the various use cases during surface operations. Demosaicking of raw Bayer tiles
is done using the algorithm by Malvar et al. (2004), using software code inherited from the
Mars InSight lander imaging system (Maki et al. 2018).
4.2 EDLCAM FSW
All EDL camera images and sound files are saved as raw data in the DSU. The raw data
can be compressed and saved separately in the DSU as compressed files. Either compressed
or raw data can be copied into the rover. Data can be compressed multiple times if desired
and saved to separate files for later transmission. Most video data will be compressed using
MPEG (Moving Picture Experts Group) video compression. Individual images will gener-
ally be compressed using lossy JPEG compression.
The EDLCAM DSU runs a custom-built version of Linux that has been tailored to max-
imize data throughput from the USB cameras to the rover DSU non-volatile storage (SSD).
The application layer consists of two modules that determine the two operating modes: com-
mand mode and EDL mode. Upon power-on, the system waits for commands from the rover
flight software. If no commands are received after a pre-determined timeout, the EDLCAM
software transitions to EDL and begins autonomously collecting data from the cameras.
Because the DSU does not receive any commands from the rover during EDL, the entire
EDL sequence is autonomous. If the DSU receives a command before transitioning to EDL
mode, the EDLCAM software transitions to command mode. While in command mode the
DSU sits idle until additional incoming commands are received from the rover. During sur-
face operations, commands will be sent to the DSU to initiate internal data compression and
subsequent file transfer into the RCE.
The core EDL data processing and compression engine is powered by FFMPEG
(ffmpeg.org). The JPL-developed custom software application layer is comprised of ap-
proximately 20,000 lines of code. All other functionality is provided by open-source soft-
ware projects. The total software storage footprint is less than 100 MB. During the 7-minute
EDL sequence, the EDLCAM system is expected to generate and store more than 40 GB of
camera and microphone data.
4.3 LCAM
LCAM has no software; all of the software for LVS is resident in the VCE. LCAM images
are exposed using exposure times computed in advance based on predictions of the signal
level under the expected illumination conditions. The VCE has the capability to dynamically
change the exposure time should the images appear too bright or too dark.
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137 Page 38 of 48 J.N. Maki et al.
Fig. 31 The Mars 2020 web-based image viewing and data search tool
4.4 Ground Software
The Perseverance ground image processing system is largely inherited from Mars Pathfinder
(LaVoie et al. 1999) and MER (Alexander et al. 2006), with subsequent updates for MSL and
the Mars InSight mission (Abarca et al. 2019). Many of the updates for Mars 2020 include
adding capabilities specific to the handling and assembly of the individual image tiles into
the larger original images. Another improvement to the heritage ground system involves the
development of web browser-based image viewing and cataloging tools (Fig. 31).
5 Calibration and Test
5.1 ECAMs
The Navcams, Hazcams, and Cachecam underwent instrument-level acceptance testing,
functional testing, and calibration prior to delivery to ATLO (Fig. 32). Calibration of the
ECAM cameras included the characterization of MTF (Modulation Transfer Function), SNR
(signal to noise ratio), boresight location, FOV, flat field, dark current, and color response
function.
5.1.1 Stereo Imaging Tests
The Mars 2020 stereo image processing system has been tested with data from the flight unit
cameras and flightlike prototype cameras. Because the Perseverance ECAMs are capable of
generating images at four different pixel scales, a preprocessing system re-assembles the
image tiles back into larger images (as applicable) prior to running the stereo matching
software on the stereo pairs. The pre-processing system generates several versions of the
reassembled images, resulting in a set of images with different pixel scales and use cases.
A typical example is shown in Fig. 33. A full description of the image products will be
included in the archive delivery to the NASA Planetary Data System (PDS).
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The Mars 2020 Engineering Cameras Page 39 of 48 137
Fig. 32 Instrument-level thermal vacuum testing of the Perseverance Hazcams
5.1.2 Solar Imaging Tests
Navcam images of the sun are used to autonomously determine the sun location in the local
Mars coordinate frame. The derived sun location is subsequently used by the rover FSW to
determine the rover three-axis attitude. There are three primary methods to determine the
vector to the sun with the Navcam: 1) sun find, 2) sun update, and 3) sun gaze. All three
methods use a disk centroiding algorithm to identify the location of the Sun in a Navcam
image. A preprocessing algorithm identifies the brightest area in the image (see Fig. 34)
over which to search for the sun centroid.
A sun find is requested when the location of the sun is poorly known and multiple Nav-
cam images may be required to perform a sky search and locate the sun. A sun update is
typically performed when the sun location is approximately known. A sun update uses the
estimated sun vector to acquire an image of the Sun, refine the sun position and improve the
rover azimuth knowledge based on the results. Finally, a sun gaze is used when the sun is at
a high elevation. A sun gaze acquires multiple images of the sun over a specified time period
to derive the vector of sun motion. The motion vector technique is used to avoid poor sun
location solutions that may arise when the sun is near zenith.
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137 Page 40 of 48 J.N. Maki et al.
Fig. 33 Results of stereo processing on a pair of 20 Megapixel prototype Navcam images in the JPL
Marsyard. The higher pixel scale of the M2020 Navcams (compared to MSL) allows denser stereo maps
at the same camera-to-object distance. The space between XYZ contours in the above figure is 10 cm. The
red contour lines represent distance in the X direction of the local site coordinate frame and the green contours
represent the distance in Y. The purple contours represent the distance in Z (height)
Fig. 34 Examples of Navcam outdoor solar image testing, conducted with a flight-like Navcam. The left
image was acquired in quarter-scale (4 ×4) mode, and the image on the right was acquired in full-scale
(1 ×1) mode. The image on the right is cropped to show detail
On Mars 2020 the sun update and sungaze methods have the ability to process saturated
Navcam images. When a Navcam acquires an image the sensor exposes the pixel and sub-
tracts a background level (correlated double sampling). However, the sun is so bright that it
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The Mars 2020 Engineering Cameras Page 41 of 48 137
Fig. 35 Front Left Hazcam Image. Note the top of the image is obscured by a sun visor. During operations
the sun visor region of the image will not typically be returned
often saturates both the exposed pixel and the background level. Subtracting these images
often creates a “black sun” image that is not adequate for centroiding. To solve this prob-
lem the camera has a mode that bleeds off charge from the background signal so that it is
only partially saturated. When using this mode, subtraction of the background signal from
the exposed image results in an image this is properly saturated (non-zero). This causes the
Sun to appear in the image as a bright spot surrounded by a ring, as shown in Fig. 34.De-
spite the ring artifacts the centroiding algorithm achieves high enough accuracy to meet the
requirements and reduce the rover pointing error even at high sun elevations.
5.1.3 ATLO
After the flight cameras were mounted on the rover in ATLO the locations and relative
alignments of the ECAM cameras were measured in the rover navigation coordinate frame
by performing a machine vision calibration similar to the calibration performed on the MER
and MSL cameras (Maki et al. 2003, and Maki et al. 2012). The results of the geomet-
ric calibration are recorded in the CAHVORE camera model system of Yakimovsky and
Cunningham (1978) and Gennery (2001,2006). The cameras also participated in functional
tests, including System-level Thermal Testing (STT) and other system testing, where a total
of over 6,000 ECAM images (tiles) were acquired. Figures 35,36,37 and 38 show example
images from these functional tests.
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137 Page 42 of 48 J.N. Maki et al.
Fig. 36 Rear Hazcam image
5.2 EDLCAMs
The EDLCAMs underwent extensive functional testing prior to delivery to ATLO. Video
tests were performed with live mortar firings (Fig. 39), demonstrating the ability of the
DSU and cameras to acquire video of high-speed external events. After the EDLCAMs
were integrated onto the rover in ATLO, they participated in functional and system testing,
including EDL test runs.
5.3 LCAM
Prior to delivery, LCAM was calibrated using a typical flow to measure its radiometric re-
sponse, geometric properties, and behavior over temperature. An MTF test image from this
testing is shown in Fig. 40. An extensive program of realistic imaging testing was performed
using flight-like EM hardware imaging from a helicopter (Johnson et al. 2020). After inte-
gration with the spacecraft in ATLO, imaging testing was performed with the flight LCAM
to verify functionality in the integrated system (Fig. 41) and to determine LCAM pointing
in the rover coordinate system.
6 Operations and Data Archiving
Operations of the ECAMs and EDLCAMs will be performed by the ECAM operations team
at JPL in Pasadena, CA. The operations team members, software tools, and processes draw
on heritage from the MER and MSL operations teams.
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The Mars 2020 Engineering Cameras Page 43 of 48 137
Fig. 37 Navcam image acquired during System Thermal Vacuum testing
6.1 ECAMs
The ECAM hardware modes described in Sect. 3.1.6 allow operators to request images of
differing pixel scales from the same 20 Megapixel source image. This new capability allows
higher-scale image tiles to be inset into lower-scale tiles, offering a combination of wider
coverage at lower scale for context and higher scale tiles targeted on particular areas of in-
terest. This context/targeted strategy can be used to significantly reduce overall data volume.
Figure 42 shows how this capability might be used for a drive direction planning panorama.
The Fig. 42 example includes two quarter-scale frames (1 and 8), 4 half-scale frames (2, 4,
6, and 7), and 2 full-scale frames (3 and 5). Because images 2 through 7 all come from the
same original source image, no repointing is required, although re-exposure could occur on
frames 2 through 7 if optimal exposure was desired on all frames. The example in Fig. 43
shows how the multi-scale capability might be used for a 360◦survey panorama. In that
example the farther field terrain covered by the full-scale tiles will have a spatial scale more
comparable to the near-field spatial scale covered by the lower-scale tiles.
6.2 EDLCAMs
EDLCAM operation during the surface phase of the mission will be focused primarily on the
cataloging and prioritization of the over 15,000 images expected to be acquired during EDL.
During the early phase of the mission, low-resolution videos, audio files, and still frame
images will be downlinked. After review and analysis by the EDL teams, higher-resolution
data may be requested and subsequently downlinked over the course of the surface mission.
EDLCAM data will also be available to the science teams.
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137 Page 44 of 48 J.N. Maki et al.
Fig. 38 Flight Cachecam image acquired during ATLO testing. The remove-before-flight cover shown in
this image has a diameter of approximately 46.4 mm. The spatial scale of this image is approximately 12.5
microns/pixel (the cover is not exactly at the best focus distance)
Fig. 39 EDLCAM testing. Indoor mortar firing test (left), outdoor mortar firing test (center), and simulated
parachute image testing (right)
6.3 LCAM
The LCAM takes images at variable rates during descent to reduce data storage require-
ments. Images are taken at 0.3 Hz starting just prior to heat shield separation down to the
start of localization. During localization, which occurs between 4200 meters and 500 me-
ters, images are taken at around 1 Hz. From 500 meters to the surface, images are taken at
0.3 Hz. All images will be downlinked to Earth later on during the surface mission for post-
EDL analysis and assessment. These images (along with the RDC images) will be made
available to the science team for potential landing site topography studies using structure-
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The Mars 2020 Engineering Cameras Page 45 of 48 137
Fig. 40 An MTF test image
taken with the LCAM flight unit
in the MSSS Cleanroom. This
image was acquired unsummed
and over the full format of the
detector
Fig. 41 LCAM image of the
ceiling in the JPL Spacecraft
Assembly Facility (SAF) taken
after integration with the flight
rover. This image was acquired in
the flight mode (2 ×2 summed
with windowing to give a
1024 ×1024 pixel format)
from-motion techniques (Garvin et al. 2017,2019) or other investigations. After landing,
LCAM image acquisition will not be possible because the camera interface FPGA will be
reconfigured to support stereo vision and visual odometry processing tasks.
6.4 Archiving
All of the raw images from the Perseverance engineering cameras will be archived in the
NASA Planetary Data System (PDS) within 6 months of receipt of the data on Earth. Ad-
ditionally, all of the derived geometric, radiometric, and stereo data products from the Nav-
cams and Hazcam cameras will be also be archived, along with additional derived products
from the other engineering cameras. Microphone data will also be archived.
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137 Page 46 of 48 J.N. Maki et al.
Fig. 42 Notional Navcam operations sequence for a rover “drive direction” planning panorama, acquiring
nine Navcam images of varying pixel scale. The background image for this figure (and Fig. 43) is from an
MSL Mastcam panorama (Malin et al. 2017)
Fig. 43 Notional Navcam 360◦survey panorama, comprised of a 5 ×1 quarter-scale portion (images 1
through 5, shown in red), and a full-scale 360◦inset panorama (16 ×1 full-scale tiles, shown in green)
7 Summary
The Perseverance rover carries a next-generation imaging system that will improve the op-
erational capabilities of the Mars 2020 mission. EDLCAM video of key EDL events will
document the performance of the Mars 2020 system and inform the design for future EDL
systems. The LVS/LCAM system will enable more targeted landing capabilities. Recorded
audio from the rover microphone may reveal new acoustic signatures that were unknown
prior to Mars 2020. If the microphone continues to operate during the surface mission,
recorded sounds of the rover mechanisms may have diagnostic value for assessing the state
of rover hardware. The next-generation Navcams and Hazcams will acquire images of Mars
with wider fields of view and higher pixel scale than versions on previous missions. The
Cachecam will acquire 12.5 micron/pixel images of the cached samples in the sample tubes.
Images from the cameras will play an important role during the operational phase of the
mission and will become part of the permanent record of the Perseverance mission. These
same images will also become a key component of any future sample return mission.
Acknowledgements This work was performed by the Mars 2020 project at the Jet Propulsion Laboratory,
California Institute of Technology, under contract with NASA. The authors thank the efforts of the entire Mars
2020 project team, including Matt Wallace, John McNamee, Rick Paynter, Mark Underwood, Cate Harris,
Jeff Srinivasan, Gun-Shing Chen, Jerry Mulder, Nicole Spanovich, Katie Stack-Morgan, Ken Farley, Ken
Williford, Sarah Milkovich, Jason Van Beek, Sabrina Feldman, Zach Ousnamer, Ben Riggs, Tony Ganino,
Ryan Van Schilfgaarde, Chris Chatellier, Mark Thompson, Hung Nguyen, Gene Poyorena, Ken Herkenhoff,
and many others.
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