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Mission Overview of the Miniature X-ray Solar Spectrometer (MinXSS) CubeSat

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Abstract

The Miniature X-ray Solar Spectrometer (MinXSS) is a 3-Unit (3U) CubeSat to study the energy distribution of solar flare soft X-ray (SXR) emissions of the quiet Sun, active regions, and during flares and to model the solar SXR impact in Earth’s ionosphere, thermosphere, and mesosphere (ITM) using these MinXSS solar measurements. The energy variability in the SXR range can vary by more than a factor of 100, yet we have limited spectral measurements in the SXR to accurately quantify the spectral dependence of this variability. Energy from SXR radiation is deposited mostly in the ionospheric E-region, from ~80 to ~150 km, but the precise altitude is strongly dependent on the SXR spectrum because of the steep slope and structure of the photoionization cross sections of atmospheric gases in this wavelength range. The new MinXSS solar SXR spectra measurements and associated modeling of the solar spectra and Earth’s ITM response will address these outstanding issues. MinXSS includes an Amptek X123 X-ray spectrometer to measure solar irradiance spectra from 0.5 – 30 keV [2.5– 0.04 nm] with a nominal 0.15 keV energy resolution [spectral resolution of 0.7 nm at 2.5 nm and 0.0002 nm at 0.04 nm] and a SXR photometer with similar spectral sensitivity. Both of these SXR instruments had pre-flight calibrations with an accuracy of about 5% at the National Institute for Standard and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF). This presentation will include an overview of the MinXSS CubeSat design and development that involved over 40 graduate students supervised by professors and professionals at the University of Colorado at Boulder. The MinXSS CubeSat was launched in December 2015 to the International Space Station (ISS) and awaits deployment from the ISS in April-May 2016. Assuming MinXSS has been deployed before June, we also intend to present first light observations from MinXSS to highlight solar SXR spectra and SXR variability during May 2016.
Above: SolidWorks
renders of the design
and mechanical block
diagram.
Left-Right: MinXSS
Flight model 1
Basic Specifications:
Mass: 3.51 kg
Volume: 34x10x10 cm
Power generated: 16 W
(orbit average)
Power consumed: 7 W
Downlink: 9600 baud
437 MHz (UHF)
P8.16 – MISSION OVERVIEW OF THE MINIATURE X-RAY SOLAR
SPECTROMETER (MINXSS) CUBESAT
THOMAS N. WOODS, AMIR CASPI, PHIL CHAMBERLIN, ANDREW JONES, RICK KOHNERT, XINLIN
LI, JAMES MASON, CHRIS MOORE, SCOTT PALO, COLDEN ROULEAU, AND STAN SOLOMON
UNIVERSITY OF COLORADO AT BOULDER -!AEROSPACE ENGINEERING SCIENCES - LABORATORY FOR ATMOSPHERIC AND SPACE PHYSICS
lasp.colorado.edu/home/minxss
MinXSS CubeSat will observe the
solar soft X-ray (SXR) spectrum
(0.4-30 keV or 2.5-20Å) at moderate
resolution (0.15 keV).
Solar SXRs are particularly important
because the greatest intensity
enhancements during solar flares are
expected to occur near 20 Å (Rodgers et
al., 2006, see Figure 1).
Additionally, the distribution of energy
in the SXRs plays an important role in
creating Earth’s ionosphere and heating
Earth’s thermosphere (Figure 2).
MinXSS is a 3U (34.5 cm x 10 cm x
10 cm), 4 kg CubeSat launched on
Dec. 6, 2015 to the ISS and then was
deployed on May 16, 2016 into its low-
Earth orbit. It is expected to be in
normal operations in early June.
OVERVIEW AND MOTIVATION
COLLABORATION AND INDUSTRY
The MinXSS ground station was built by the
MinXSS predecessor, the Colorado Student Space
Weather Experiment (CSSWE) CubeSat project, at
CU and is on the roof of LASP. Many of the
professionals and students involved with
successfully operating CSSWE are still at CU and
provide operations heritage for MinXSS.
OPERATIONS HERITAGE
THE SYSTEM
The Amptek X123 is a commercial off-the-shelf
(COTS) X-ray spectrometer that uses a silicon drift
detector and includes a thermoelectric cooler,
beryllium filter, and support electronics. Its price
(~$11k), size (14 x 5.4 x 2.5 cm3), mass (180 g),
and power (2.5 W nominal), make it ideal for a
CubeSat mission. Originally developed for
applications such as X-ray fluorescence analysis
for geology and archaeology, it will now be used to
observe the Sun from space to enable new
scientific studies of the solar flare variability and
its influence in Earth’s atmosphere.
[www.amptek.com/x123]
CUBESAT CARD CAGE
Right: EPS, CDH,
COMM, and battery
daughter boards in
motherboard. Science
instruments (X123,
SPS, XS) and ADCS
interface via cables.
Figure 1: Example
solar spectrum during
flare with coverage of
currently operating
h i g h - r e s o l u t i o n
missions (EVE and
R H E S S I ) a s
c o m p a r i s o n f o r
MinXSS.
Greatest flare enhancements
expected
[Rodgers et al. 2006]
[Courtesy of Amir Caspi]
[Courtesy of Tom Woods]
Figure 2: Top: Two
model solar spectra
s c a l e d t o h a v e
identical 0.1-7 nm
int egrate d energy
flux.
B o t t o m : The
deposition of the
s a m e a m o u n t o f
energy into Earths
atmosphere is very
different for the two
energy distributions.
T h e ~ 5 k m
differences in peaks is
comparable to the 5.8
km scale height at the
mesopause.
Active region spectrum
Flare spectrum
DESIGN/PURCHASING
Commercial off-the-shelf (COTS) subsystems.
These items are available on the market. Our
efforts are simply to interface with them. These
include the Amptek X123 instrument, AstroDev
Li-1 radio, and AzurSpace solar cells.
Designed, built, integrated, and tested by students
with guidance from professionals. EPS has
heritage from CSSWE. CDH and the motherboard
are new designs but have been flown on a rocket.
Strong collaboration. The ADCS is being designed
and built by Blue Canyon Technologies (BCT), a
relatively new aerospace company in Boulder.
Background: www.wallpaperpin.com/webdisk/sun-summit-desktop-wallpaper.jpg
THE WORK AND PEOPLE
Solar panel fabrication
Team Spring 2014
Students with NASA
administrator Bolden
Anechoic chamber testing
NIST instrument calibration
[Courtesy of Joe Harrison]
CU provides graduate students from aerospace and electrical engineering, computer science, and astrophysical and planetary
sciences. Professors act as mentors for the MinXSS graduate project. LASP provides professional mentors and facilities.
Blue Canyon Technologies provides the attitude determination and control system (ADCS). MinXSS will be the first flight
of their system with advanced capability for 7 arc-sec 3-axis pointing from a CubeSat. As a local company, they have
supported major reviews of the MinXSS project and have assisted in multiple air bearing tests of the satellite.
First RF in Boulder allowed us two opportunities to measure the RF gain pattern of our system in their anechoic chamber.
The data collected were used as model validation and high fidelity input to the MinXSS link budget.
MinXSS flight model satellites are being used to aid in the development of Braxton’s ground software for ground telemetry
and control operations, a system intended to improve upon and replace ISIS, the ground software MinXSS currently uses.
Vibration testing was done in December 2014 at
Ball Aerospace in Boulder.
Synchrotron Ultraviolet Radiation Facility
was used to calibrate science instruments.
Amptek’s COTS part, the X123, is the
primary science instrument on MinXSS.
Azur Space provided the 30% efficient
triple-junction solar cells used on MinXSS.
Astronautical Development LLC provided
the Li-1 radio used on MinXSS.
M i n X S S a n d C A D R E
CubeSats are deployed
from NanoRacks dispenser
on ISS on May 16, 2016.
ResearchGate has not been able to resolve any references for this publication.