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Abstract and Figures

A Software Defined Radio (SDR) is a flexible technology that enables the design of adaptive communications systems. A generic hardware design can be used to address different communication needs, such as changing frequencies, modulation schemes and data rates. Applied to small satellites, some of the implications are increased data throughput when down-linking or up-linking by varying communications parameters and making use of one hardware design and implementation for communicating for many missions, just by updating the software. Therefore, development time for small satellite communication systems can be reduced in the future. This one of the reason why many universities and other organisations around the world are investing in this type of space technology. The technology can support different kinds of applications, such as Earth observation and communication services. This paper analyses various hardware and software platforms and includes a survey on SDRs that have been designed and developed for satellite communications in the last years. In the survey both ground stations and satellites using SDR have been included. Furthermore, a short discussion on SDR designs have been included.
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Gara Quintana-D´
ıaz(1), Roger Birkeland(1)
(1)Norwegian University of Technology and Science (NTNU), O.S. Bragstad plass 2A, 7491
Trondheim, Norway.,
A Software Defined Radio (SDR) is a flexible technology that enables the design of adaptive
communications systems. A generic hardware design can be used to address different commu-
nication needs, such as changing frequencies, modulation schemes and data rates. Applied to
small satellites, some of the implications are increased data throughput when down-linking or
up-linking by varying communications parameters and making use of one hardware design and
implementation for communicating for many missions, just by updating the software. Therefore,
development time for small satellite communication systems can be reduced in the future. This
one of the reason why many universities and other organisations around the world are investing in
this type of space technology. The technology can support different kinds of applications, such as
Earth observation and communication services. This paper analyses various hardware and soft-
ware platforms and includes a survey on SDRs that have been designed and developed for satellite
communications in the last years. In the survey both ground stations and satellites using SDR have
been included. Furthermore, a short discussion on SDR designs have been included.
The interest in small satellites (or SmallSats) is continuously growing, both in CubeSats and other
customised platforms. Many universities and other organisations around the world are investing
in this type of space technology for various applications, such as space exploration and Earth ob-
servation. When observing our planet there are two especially relevant areas to focus on: oceans,
as 71 % of the Earth is water [1], and Arctic monitoring, because of the dramatic effect of global
warming. In-situ monitoring of these extremely harsh areas is difficult, expensive and they are not
fully covered by communication systems [2]. This is one reason why it is important to research
new solutions in order to improve ocean and Arctic monitoring. One possibility is to deploy a
coordinated infrastructure composed of different types of vehicles and platforms, such as AUVs,
UAVs and small satellites [2].
The Norwegian University of Science and Technology (NTNU) together with the Center for Au-
tonomous Marine Operations and Systems (NTNU-AMOS) have recently launched a new re-
search programme. It has a concerted and unified cross-disciplinary focus on designing, building
and operating small satellites (or SmallSats) as parts of a system of autonomous robots and agents
for maritime sensing, surveillance and communication. These activities should contribute to fun-
damental and interdisciplinary research on autonomous systems in marine applications. The pro-
gramme is associated with the Faculty for Information Technology and Electrical Engineering’s
strategic research area Coastal and Arctic Maritime Operations and Surveillance (CAMOS) and
has planned two missions. The first is to acquire high quality images for oceanographic studies
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using a Hyperspectral Imager (HSI) and the second one to provide Arctic researchers with easier
and faster access to scientific data by using a flexible communications system.
One important aspect to consider when building any type of satellites is communications. Com-
munication systems enable data transfer between sensor systems, satellites and end users. Most
kinds of communications systems are designed for worst-case scenarios, and satellite channel
characteristics are highly variable due to atmospheric and ionospheric effects, especially in Low
Earth Orbits (LEO). Designing for worst-case leaves an expensive and overly designed system
that does not maximise channel capacity. To compensate for this, there is a need to develop en-
hanced communications systems that can adapt to variable characteristics, for instance changing
modulation, power levels or carrier frequency on-the-fly.
Software Defined Radio (SDR) is a flexible technology which enables the design of an adap-
tive communications system. This means that a generic hardware design can be used to address
different communication needs, with varying frequencies, modulation schemes and data rates
[3]. Applying this concept to small satellites can increase data throughput, add the possibility
to perform software updates over-the-air and make it possible to reuse the hardware platform for
multiple missions with different requirements [4]. Therefore, development time for future small
satellite communication systems can be reduced, even though the development time of the first
implementation might be longer than for a traditional radio system.
However, this idea of launching SDR into space is not new. There are many universities, agencies
and companies that are currently addressing this issue and some have already launched their own
designs. Various SDR platforms and designs are analysed for use in small satellites in challenging
scenarios, data retrieval from diverse Arctic sensors or multi-agent communications, for instance.
This paper also studies the state-of-the-art of SDR both for spacecraft and ground stations devel-
oped by different universities and organisations.
In addition to requirements for frequency, bandwidth and regulations found in every communica-
tion system, Software Defined Radios (SDR) are highly dependent on the hardware platform used
to run the software. In small satellites, the main design drivers are size, mass, cost and power
In Figure 1 an overview of some SDR platforms is shown. The vertical axis is cost whereas the
horizontal axis is mass. These are two important aspects to consider when choosing a radio suit-
able for a small satellite mission. Ideally, the best platform would be the one on the lower left
corner of the graph: an inexpensive and light solution. In our comparison, GomSpace SDR is the
most expensive, and it has an average mass. However, it is also the only space-qualified hardware
platform. While decreasing the cost, the next platforms is the different EPIQ and USRP models.
The inexpensive platforms, with a cost of less than 300 C, are the ones from FunCube, Lime and
RTL. All with average to low mass.
Each of the platforms are described briefly below.
2.1 GomSpace SDR
The SDR system is built by combining three standalone components: GomSpace NanoCom TR-
600 (transceiver), NanoMind Z-7000 (processor/FPGA-unit) and the NanoDock SDR [5]. There
is shielding added to the components and the size of the system is 22 x 16 x 5 mm. The RF
capabilities are provided by the AD9361 transceiver that deals with the phase (I) and quadrature
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GomSpace SDR
EPIQ Matchtiq S10-S12
EPIQ Solutions Matchtiq
FunCube Pro
FunCube ProPlus
Space proven
Figure 1: SDR platform overview (cost vs mass).
(Q) samples. Xilinx Zync 7030 SoC (System on Chip), which includes dual core ARM Cortex A9
processors and FPGA logic, performs the processing. However, there is no possibility of using
GNURadio to program the transceiver at this moment. The noise figure of the NanoCom TR-600
receiver ranges from 5.1-7.8 dB and the power consumption is 3 W (idle).
Technical characteristics of AD9361 [6] are shown in table 1. The frequency range of this com-
ponent is what limits the GomSpace SDR to 70 MHz - 6 GHz. In addition, AD9361 has two
channels for MIMO (Multiple Input Multiple Output) and supports TDD (Time Division Duplex)
and FDD (Frequency Division Duplex).
Features AD9361
Transmitter frequency band 47-70 MHz
Receiver frequency band 70 MHz - 6 GHz
Channel bandwidth 200 KHz- 56 MHz
Noise figure 2 dB at 800 MHz LO
Operation modes TDD and FDD
Table 1: AD9361 technical characteristics
2.2 USRP from Ettus Research
USRP E310 is part of the Embedded Series platform, which uses an OpenEmbedded framework
and can be programmed with GNURadio [7]. The transceiver is also AD9361 and the processing
unit is the Xilinx Zynq 7020 SoC (including dual core ARM Cortex A9 processors and a FPGA).
The size of this SDR is 133 x 68 x 26.4 mm. The noise figure of the overall receiver is 8 dB and
power consumption ranges from 2-6 W.
USRP N210 from Networked Series has a higher performance, as the Analogue to Digital Con-
verters (ADCs) and Digital to Analogue Converters (DAC) have higher resolution and sample
frequency, at the expense of increasing its mass and size (220 x 160 x 50 mm) [8]. It can also be
programmed using GNURadio. The RF frontend consists of a daughterboard, and the processing
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unit is based on a Xilinx Spartan3-DSP. The frequency range is from DC to 6 GHz and the receiver
has a noise figure of typically 5 dB.
2.3 EPIQ
EPIQ Solutions Matchstiq has a few SDR models, namely the S10-S12, with similar cost and
characteristics as the USRPs [9]. It uses Xilinx Zynq 7020 SoC and the same transceiver as most
of the SDRs, the AD9361, so it has same RF capabilities. The noise figure of the receiver is also
8 dB. Moreover, the size is 112 x 50.8 x 36.3 mm and the power consumption 2-6 W.
2.4 Lime microsystems
Lime microsystems offers two transceiver chips similar to Analog Devices one, the LMS6002D
and LMS7002M. In Table 2 both transceivers are compared.
Features LMS6002D LMS7002M
Transmitter frequency band 47-70 MHz 30 MHz-3.8 GHz
Receiver frequency band 70 MHz-6 GHz 30 MHz-3.8 GHz
Channel bandwidth 0-28 MHz Up to 481, 96 2, 160 MHz3
Noise figure 3.5-10 dB 2-3.5 dB
Operation modes TDD and FDD TDD and FDD
Table 2: Lime microsystems transceivers technical characteristics
LimeSDR-USB has a smaller frequency band than the previous mentioned SDRs, from 0.1
MHz to 3.8 GHz, and a maximum bandwidth of 61.44 MHz [10]. It uses an Altera Cyclone IV
EP4CE40F23C8N and LMS7002M transceiver chip (noise figure of 2-3.5 dB). The size is 60 x
100 mm. In addition, it can be programmed using GNURadio framework. Compared to the USRP
embedded series and the Matchstiqs, this radio does not come with an integrated processor.
LimeSDR-mini is similar, also programmable with GNURadio, but has fewer features [11].
The frequency range is from 0.01 MHz to 3.5 GHz and the maximum bandwidth is 30.72 MHz.
The RF transceiver is the same chip but the FPGA is Altera MAX 10 (10M16SAU169C8G). The
main advantage is that is smaller, 69 x 31.4 mm and inexpensive.
2.5 FunCube
FunCube Pro is a very small SDR which uses a Silicon tuner as RF frontend and a PIC24FJ32
GB002 as microprocessor. The transmitter frequency range is from 0.64 MHz-1.1 GHz, whereas
from receiving is from 1.27 - 1.7 GHz.
FunCube ProPlus is a similar SDR. It covers from 150 KHz-240 MHz and from 420 MHz
to 1.9 GHz and has a maximum bandwidth of 56 MHz. Both FunCube models where made to
support HAM radio satellite missions.
RTL SDR is also a very small SDR, limited to receiving only. The frequency band covered is
from 0.5 MHz to 1.766 GHz, with a maximum channel bandwidth of 2.4 MHz. It consists of a
Rafael Micro R820T chip, a transceiver chip with 3.5 dB noise figure, and a digital modulator.
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2.7 Others
There are many other SDRs available. BladeRF uses an Altera Cyclone IV and LMS6002D
transceiver [12] and HackRF One uses an NXP microcontroller MAX2837 transceiver [13], both
programmable using GNURadio. SWIFT has several SDR models with ongoing small satellites
designs [14] such as SWIFT-UTX, SWIFT-SLX, SWIFT-WRX. Finally, AstroSDR [15] is a Space
Plug-and-Play CubeSat SDR which uses Xilinx Zynq Z-7045 and the AD9362 transceiver, and
therefore covers similar bands, and has a power consumption of 4-40 W.
In Figure 2 maximum channel bandwidth of the platforms mentioned above is plotted against fre-
quency in a qualitative way. As it can be seen most of the SDRs work in many bands.
GomSpace SDR
FunCube Pro
EPIQ Matchtiq S10-S12
70 MHz
28 MHz
Figure 2: Maximum channel bandwidth vs frequencies covered in SDR platforms.
Another aspect to be considered when choosing an SDR is the software development tools. Some
platforms are GNURadio compatible, like the USRP, Lime SDR, FUNCube, HackRF and others.
This gives the users and developer access to a well-know open source ecosystem to base the
software development on. This can be used both for ground stations and for the space segment.
The USRPs also support the National Instruments LabView, thus a LabVIEW interface could be
used to program them. However, due to the need for extra hardware and software to run LabView,
this interface can reduce the development time but it can only be used in the ground station. One
alternative would be to develop programs from scratch, for example in C for the microcontroller,
or VHDL/Verilog for the FPGA. The programming language required for the SDR platform is
definitely a factor to take into account.
This section showcases a survey of SDRs that all have been designed and developed for satellite
communications over the last years. We present an analysis of various hardware and software
platforms. In the survey both ground stations and satellites using SDR are included.
3.1 Space Segment
The Aerospace Corporation and the University of Michigan-Flint have described a SDR de-
sign for their pipeline of small satellites, the Aerocubes [16]. The purpose of using this flexible
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technology was to increase the data throughput by using Adaptive Coding Modulation (ACM)
technique and changing the error encoding characteristics and modulation depending on the chan-
nel variation. Simulations were carried out for a typical AeroCube pass over a ground station. By
changing modulation (BPSK, QPSK, 16APSK, 32APSK) and code rates (from 1/4 to no encoding
at all) without modifying the symbol rate, the throughput was increased by a factor of two if com-
pared to QPSK at 1/2-rate coding. Looking at the SDR design, they adapted the firmware from an
earlier SDR implementation and used a Zynq7020 board as the processing unit. The LMS6002D
transceiver was used as RF frontend. The carrier frequency of the first generation design is 914
MHz (1 MHz of bandwidth), whilst the second generation transceiver will work on 26.1 GHz.
The power consumption is 1.2 W when receiving and 2.5 W when transmitting 30 dBm.
Istanbul Technical University has also contributed to the development of space SDRs using
Components Off-The-Shelf (COTS). In [17] two SDRs are described: one for the ground station
and one for a CubeSat. The SDR for space is half-duplex and it is implemented in three boards: the
transmitter, the receiver and a FPGA board, containing an Altera EP3C25E144I7N. It uses UHF
Industrial Scientific and Medical (ISM) band, 433.92 MHz, and a 2FSK modulation. In addition,
the power consumption is quite low; 2 W when transmitting and 0.7 W when receiving. The
ground station SDR used two USRPs, a computer, one Low Noise Amplifier (LNA) and a power
amplifier. Even though their project was carried out by undergraduate students, components for
the CubeSat SDR were tested under space conditions. This small satellite is called HavelSat [18]
and was launched in April 2017 [19].
University of Vigo in Spain and University of Porto [20] have been working for several years in
the HumSat project, supported by the United Nations office for outer space affairs (UNOOSA), the
European Space Agency (ESA) and the International Astronautical Federation (IAF). This project
is a collaboration between multiple universities and centres, and its objectives are: to develop a
data communications system for areas where there is not enough infrastructure for humanitarian
purposes and to have sensors in remote areas. The SDR is a transmitter built on a board with a
RF stage, a control stage and a power stage. The frequency ranges used from 440-470 MHz, with
GMSK modulation and the power consumption when transmitting 30 dBm is 3.2 W. In stand-by
mode the power consumption is 0.14 W. The first version of this SDR was launched in 2013 in a
1 unit CubeSat, called Xatcobeo. The next version is planned to be launched in December 2018.
Applied Physics Laboratory from Johns Hopkins University has built a TRL-9 SDR which
has flown in the Van Allen Probes mission from NASA (National Aeronautics and Space Admin-
istration) with an S-band configuration (an X-band and Ka-band link can be possible too) [21],
[22]. This SDR, called Frontier Radio, enables the possibility of changing to multiple modulation
schemes, such as, BPSK, QPSK, PM/subcarrier for reception and up to 64PSK and 16QAM for
transmission. Frontier radio is and FPGA-based design that uses RTAX4000 for the processing
part and has different exciter slices depending on the frequency band used.
NASA has a huge interest in pushing SDR technology forward. Their objective is that an SDR
may provide a flexible transceiver platform that can be tailored to several missions, just by chang-
ing software or hardware logic [3]. This is one of the reasons that can explain why there are
several student satellites in the Educational Launch of Nanosatellites (ELaNa) programme plan-
ning to launch SDRs. For instance, LinkSat from Buffalo University; Space Hauc from University
of Massachusetts; STF1 from West Virginia University and other member of a consortium; VCC
A, B, C from Old Dominion University, Virginia Tech and University of Virginia; and OPEN
from University of North Dakota. In addition, in 2012 NASA launched a Space Communica-
tions and Navigation (SCAN) testbed to provide with an on-orbit SDR facility. Earlier than same
year, NASA published a paper which describes three different SDR developments for CoNNeCT
(Communications, Navigation, and Networking reConfigurable Testbed) project [23]. In the first
two cases the waveform and platform provider were General Dynamics and Harris. In the last
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case, JPL (Jet Propulsion Laboratory) and Cinnati Electronics developed the platform. Regarding
frequency bands, Harris SDR was Ka-band and GD and JPL developed an S-band SDR. All of
them using at least one Xilinx Virtex FPGA for the processing section and some radiofrequency
(RF) converters and power amplifier for the RF frontend.
3.2 Ground Segment
SDRs are not only being utilised in the space segment, but also as part of ground stations.
University of Bologna built an SDR-based ground station suitable for ESA’s European Student
Earth Orbiter (ESEO) project [24]. As previously mentioned, SDRs enable the possibility of
adding new waveforms by updating the software. Therefore, it is easier to update all ground
stations in a network, just by sharing the updated software. In this development, the USRP N210
with an RF daughterboard is used as the SDR platform and the RF frontend. The ground station
uses the UHF band, particularly radio-amateur frequencies (437 MHz for downlink and 435.2
MHz for uplink).
University of Surrey has focused on SDRs for concurrent multi-satellite communications. In
[25] it has been developed a flexible system that can receive different types of signals of dif-
ferent satellites on a ground station using SDR technology. The transceiver board used is AD-
FMCOMMS3-EBZ and for the processing part a Xilinx Zynq 7020 FPGA to achieve parallel
architectures. The frequency band covered is limited by the transceiver, being 70 MHz - 6 GHz.
National Cheng Kung University is another university that has developed an SDR-based ground
station to track small satellites [26]. The hardware used includes a ADLink PXI-3710 system con-
troller and receiver blocks are implemented on Matlab/Simulink. Frequency bands considered are
amateur VHF (140-150 MHz), UHF (430-440 MHz) and ISM band (2.4 GHz). Several bands can
be received at the same time due to the implementation of an interference cancellation approach.
The Norwegian University of Science and Technology is also working on a GENSO-compatible
station [27]. In addition to having developed an SDR-based ground station using a USRP2 and
NGHam [28].
This study of SDR state-of-the-art comes from the need to use this technology to support several
missions at the NTNU Small Satellite programme. In addition to set up a versatile SDR ground
station, the main aim is to support science data collecting missions where there is poor commu-
nications infrastructure, like in the Arctic. To provide Arctic researchers with easier and faster
access to scientific data harvested by sensor nodes, the payload should be flexible, so that phys-
ical retrieval of the data from sensors can be less frequent. In order to make better use of the
resources available (bit rate, power, link properties, timing and delay, and the amount of data), the
payload should be re-configurable and adaptable in-flight. This is where SDR technology comes
into play.
The SDR payload is meant to be an experimental system with two purposes: The first is demon-
strating re-programming of the SDR in-flight, the second is to demonstrate simple Adaptive Cod-
ing and Modulation (ACM) capabilities. Employing ACM, the bit rate and modulation can change
within one pass, or at least between passes, based on the predicted ”quality” of the pass. The re-
programmable features can comprise a selection of frequency bands, channel bandwidths, bit
rates, modulation and power levels. Depending on available frequency bands (for uplink and/or
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downlink), the payload should support at least two frequency bands; for example VHF or UHF,
and L-band or S-band. The SDR alternatives available support two separate RX/TX paths, so each
antenna system can be individually mated to one RXTX interface. If more than a frequency bands
are required, then filter banks/diplexer must be used.
Three main options considered for the payload design are:
1. Buy and integrate space proven hardware platforms, such as GomSpace SDR.
2. Buy and integrate no-space proven COTS hardware (URSPs, LimeSDR, EPIQ Solution
3. Make an in-house design and integration of a custom SDR. Based on the AD9361 transceiver
chip and an FPGA, for example.
On the one hand, the first option is safe for the mission. However, it is very expensive. Also,
buying a complete SDR implies less control of the mission. On the other hand, making a custom
design would increase the team’s knowledge of SDR and enable full control of the SDR. Most
universities in this study have done that, but it is less reliable as the components are not space-
qualified and the system has to be developed from scratch. It seems like the second option is the
best compromise. A trade-off study will be carried out to help decide which design approach is
going to be followed.
Another important aspect is how to design the RF front-end. In order to be able to communicate
using multiple bands, both the SDR hardware platform and also the RF front-end must support
the bands. More than one antenna will be needed to receive both UHF and S-band. This means
that a diplexer is needed between the SDR and the antennas. The SDR platforms usually have an
internal LNA, but an additional one may be needed. In this case, there are two possibilities: to
use a broadband LNA (designed for both bands) or two different LNAs, one for each band. Using
multiple bands can add complexity and cost to the system but enhances communication (enabling
different data rates and providing redundancy, for instance), therefore a trade-off analysis must be
Most of the radios presented in Section 2 can be used as part of a ground station design, as long as
it fits the frequency bands of the mission. Since one usually has access to computers at the ground
station, the fully embedded solutions (USRP E-series, Matchstiq and HackRF) might not be de-
sirable, as it will be easier to work on a regular computer both during development and operations.
For the space segment, the opposite is true. In this case, both size and power are major concerns.
Therefore, highly integrated embedded solutions are preferable. This can point in the direction
for the USRP E-series or the Matchstiqs. The Lime SDR could also be used, however it must be
integrated with a processor running Linux. These radios can be used in a hybrid COTS solution.
The processor is included in the USRP E and Matchstiq. It is important that the radio chosen has
a good quality, is frequency stable and have good RFI (radio frequency interference) and EMC
(ElectroMagnetic Compatibility) properties.
This survey attempts to give insight into SDRs for small satellites and ground stations. It became
clear that it is not an easy task to compare the platforms, because not all of them provide the infor-
mation needed for a coherent analysis. It is also challenging to find information about university
projects and figure out they have launched the satellites described in their papers. Nevertheless,
there is no doubt that a lot of research groups have worked on developing space SDRs. There
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are already a lot of small satellites using this technology for science applications, radio measure-
ments, navigation, communications and technology demonstrators.
Most of the university projects studied seem to use a custom SDR solution based on FPGAs. The
Zynq board and the AD9361 transceiver chip from Analog Devices are very commonly used in
these implementations. The transceiver chips from Lime microsystems has also been utilised a
few cases. This suggests to conclude that the AD9361 can be used to reduce the risk. The com-
ponent has been flown in space several times in different SDRs implementations.
Choosing an SDR platform depends on many factors and the risk of component failure is very
important to consider. GomSpace SDR seems to be the safest choice. Nevertheless, it is the most
expensive one and the team working with would not have so much control over the hardware
nor software. The URSPs can be a reasonable choice, especially for the ground station segment.
There are no requirements for size or weight, and experience with these platforms are available.
EPIQ Solutions Matchtiq and LimeSDR could also be considered both for the space and ground
segments. However the LimeSDR must be integrated with an external processor capable of run-
ning Linux. FunCube and RTL-SDRs can be used for the first time because they are inexpensive,
but may be limiting the performance of a production system. HackRF and BladeRF are interesting
platforms but have not been used in space so far. SWIFT SDRs seem very attractive, but there is
no enough information about them available. Finally, AstroSDR is an SDR designed for CubeSat
but its power consumption may be too much for a 3 unit (3U) or 6U CubeSat.
The need to develop flexible satellite communications systems, particularly for small satellites,
has been described. Different hardware implementations of this technology have been highlighted
and their technical characteristics have been explained. In addition, a survey on SDR technology
developments by several universities was carried out. Their mission or goal was described, as well
as the main components used and the radio parameters of their design. Finally, how to approach
an SDR development for NTNU’s communications mission was briefly discussed.
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... CubeSats 13 are increasingly popular spacecraft platforms for mission-oriented experiments that can be accomplished via quick prototyping and launches [13][14][15]. 11 Hardware abstraction layer (HAL) is a layer of programming that allows a computer operating system to interact with a hardware device at a general or abstract level rather than at a detailed hardware level This short development timeline is due to the use of commercial-off-the-shelf (COTS) technology that typically has limited resilience to the space environment. Therefore, CubeSat usage has largely been limited to experiments or applications where high availability is not the main objective. ...
... Wikipedia]. 12 The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines the application programming interface (API) for software compatibility with variants of Unix and other operating systems [Wikipedia].13 CubeSats are a class of Small Satellites (SmallSats) weighing between 1 kg and 10 kgs that use standard size and form factor of 1 U (one unit) of 10 cm x 10 cm x 10 cm. ...
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The objective of this chapter is to provide a comprehensive end-to-end overview of existing communication subsystems residing on both the satellite bus and payloads. These subsystems include command and mission data handling, telemetry and tracking, and the antenna payloads for both command, telemetry and mission data. The function of each subsystem and the relationships to the others will be described in detail. In addition, the recent application of software defined radio (SDR) to advanced satellite communication system design will be looked at with applications to satellite development, and the impacts on how SDR will affect future satellite missions are briefly discussed.
... A SDR is a flexible system that uses generic processor hardware in conjunction with programmable software to digitally replicate electronic radio receiver circuits [136]. This allows properties such as observation frequencies, bandwidths and modulation to be changed by software command [137]. In the event of persistent, mission-disabling interference experienced by RMCSat within the sampled bandwidths, the use of a software-defined radio, reconfigurable from the ground, will allow satellite operational channels to be adjusted in response, separating sampling frequencies from the sources of disruptive RFI. ...
Full-text available
Extreme Ultraviolet (EUV) radiation from the Sun is a key driver of atmo- spheric conditions on the Earth. It is responsible for the formation of the ionosphere, which affects communications, navigation and radar propagation. Moreover, EUV also heats the neutral atmosphere, increasing the drag force on objects in low-Earth orbit. Due to atmospheric absorption, EUV cannot be measured from the ground. Thus, the solar flux density at a wavelength of 10.7 cm, the F10.7 index, has been used as a principal proxy since 1947. F10.7 provides a critical input to atmospheric and ionospheric models and is a valuable long-term measure of overall solar activity. Despite its importance, the F10.7 index is only measured from a single location on Earth. This results in under-sampling, with no contingency substitute currently available. A space-based F10.7 measurement would provide an increase in tempo- ral coverage and measurement cadence, redundancy for existing systems, and would allow complementary solar flux measurement at all wavelengths. A 3U CubeSat mission, RMCSat, aims to demonstrate the feasibility of mea- suring microwave solar flux from a nanosatellite platform in low-Earth orbit. Ground-based experimental results show that a small antenna with a gain of just 14 dBi has sufficient sensitivity to detect small variations in the F10.7 so- lar flux. A deployable helical antenna with 40 turns, a pitch of 1.7 cm and a diameter of 3.2 cm provides up to 17 dBi of gain when mounted on a 3U CubeSat, satisfying the Dominion Radio Astrophysical Observatory require- ment for F10.7 measurement accuracy. A detailed analysis of the radio frequency noise environment allowed the development of an optimal solar observation scheme for RMCSat. A Sun- synchronous orbit and zenith-pointing orientation provides regular opportu- nity for calibration, and generates 15 additional measurements of F10.7 within a 24 hour period. Furthermore, RMCSat will concurrently monitor two key frequencies from the same sensor, F10.7, at 2800 MHz, and 2695 MHz, which is currently monitored by the United States Radio Solar Telescope Network. The use of the same calibration standard optimises signal comparison, and would allow the existing 2695 MHz dataset to be accurately scaled to F10.7, providing additional redundancy and supplementation of the F10.7 index.
... SDR systems developed by commercial space industries need to guarantee a high level of reliability, and risk acceptance in using non-space qualified electronics is not given in many space missions. On the other hand the survey of SDRs being designed and used for satellite communication, presented in [54], shows an increasing interest from Chapter 3. Software-defined radio systems in space flight 46 universities for SDR technologies in their CubeSat missions. Due to their very limited budgets, the use of space-qualified hardware is not usually considered and thus, the use of commercial electronics is unavoidable but also offers more flexibility and more efficient performance with lower power consumption. ...
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The present thesis deals with the design of a highly integrated and radiation tolerant software-defined radio (SDR) platform for multi-channel radio applications in space systems. The described design addresses the risk-minimized use of non-space qualified electronic components for critical space systems, which is ultimately used for the development and verification of the innovative SDR platform presented in this work.
... A total of 21 SDR platforms have been analyzed and have been part of a high level assessment in [13]. An extra alternative was found after that study, TOTEM SDR from Alén Space. ...
Conference Paper
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Enabling communication to sensor systems in the Arctic is a challenge due to the harsh climate, limited infrastructure and its remote location. In this paper a communication system for Arctic back-haul serving low-power devices to complement existing services is discussed and two small satellite missions are defined. The communication mission objective is to provide Arctic researchers with faster access to scientific data. However, a precursor mission is needed to gather data about the UHF communication channel and interference in the Arctic to design a reliable communication system between Arctic sensors and LEO (Low Earth Orbit) satellites. An SDR (Software Defined Radio) payload is proposed to fly on a small satellite as a secondary payload in order to carry out the radio measurements in a flexible way. The challenges of being a secondary payload are also outlined.
... An alternative is to use an SDR implementation. This is a hot topic in the small satellite community, and several designs and implementation alternatives exist, both for the space segment and the ground segment [182]. ...
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The Arctic and space are concepts that fascinate us. Both places seem remote and hostile, but are at the same time beautiful and exciting. Together, they form a part of the world comprised of daring challenges, but also of endless possibilities for science, recreation, wonder, knowledge and inspiration. Several scientists would like access to more and frequently updated information about the Arctic area. Today, no adequate communication systems allowing this exists. Due to this, access to sensor data is often limited to traveling to the sensor node and retrieve its data. This thesis aims to bridge parts of the Arctic and space. The work in this system study may bring the Arctic nearer to us by proposing a space communication system that can connect assets in the Arctic with people residing in less remote areas. The main research motivation was to investigate if a system of small satellites could be a viable solution to bridge the communication gap in the Arctic. An important use case is to enable access to sensor data from sensors deployed in remote locations without having to physically be at the node to download the data. The main findings show that this can be possible, by establishing a communication system with small satellites. The small satellites have their challenges and limits, but by careful design, a system can be made to compare with other solutions, both in utility and cost. The main contribution from this work is the proposal on how to use a freely flying swarm of small satellites to provide good and frequent coverage, without having to use satellites with propulsion systems. This saves component cost, mass and volume, which in turn contribute to a reduced launch cost. The deployment of a satellite swarm seems feasible both from a technical point of view, as well as from an economical point of view. The coverage property for a swarm is not constant, and on average it is not as good as coverage by a constellation consisting of the same number of satellites. However, for services that do not require to transmit time-critical sensor data, this is of less concern and variations in responsiveness can be accepted. Another contribution is a system study on how a heterogeneous communication architecture can be designed, ensuring interoperability between satellites, sensor nodes and unmanned vehicles. Different networks may be interconnected and joined, providing connectivity between sensor systems and operators through the Internet. This interconnection can be made possible by the use of standard Internet-of-Things protocols. These networks can consist of local networks linking sensor nodes, satellite links between sensor nodes, satellites and gateway stations, as well as other types of unmanned or manned vehicles acting as data mules; ferrying data from one part of the network to another. A central topic of investigation in any radio communication system is the link budget. By carefully evaluating the various contributing factors of the link budget, a feasible budget is presented. However, some assumptions are required. In order to design a system with a usable data rate, the satellite must be designed to compensate for some of the limitations of a typical sensor node. A system supporting an even higher data rate also requires the sensor node to be equipped with a high-gain antenna. This represents an interesting research topic for further study. The cost of the space segment is also evaluated against the use of unmanned aerial vehicles and airplanes. From this analysis, it is shown that a satellite system will provide a more continuous coverage, being able to transmit a comparable amount of data, at a similar or lower cost. The satellites could be based on Cube-Sats. To conclude, the outcome of this study shows that a dedicated satellite system, your mission, your satellite(s), can be a viable solution to the challenge on how to relay sensor data from the Arctic to scientists at home. The work follows the early phases of established space mission analysis and design methods.
Conference Paper
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In recent years, the interest for the Arctic area has been increasing. Harvesting of scientific data and environmental monitoring are key activities. The Arctic has poor communication infrastructure, both by terrestrial and satellite systems. Launching a free-flying constellation of small CubeSats is one proposal to help mitigate this service gap. CubeSats are traditionally built with industrial-grade components, which reduces the development time and hardware cost. Since the cost of one satellite is low, it is possible to launch several together. The CubeSats are generally launched without any station keeping capabilities, as this increases cost and complexity in both the production and operational phase. Without station keeping, the swarm satellites will drift relatively to each other. The governing parameter of the drift is the velocity difference of the satellites at the time of deployment. This paper shows how a freely drifting swarm can improve the coverage for sensor networks in the Arctic, when an effort is made to optimize this velocity difference at deployment. E.g., a free-flying constellation of three satellites will have better coverage properties than a fixed two-satellite constellation for more than 80% of the time.
Conference Paper
Full-text available
The NTNU Test Satellite (NUTS-1) is an educational CubeSat project aiming to launch a student designed and manufactured satellite. The project is one of three participants in the Nor-wegian CubeSat program ANSAT. The current primary goal is to have an engineering model ready by August of 2016. Communication with the ground segment will be in the VHF and UHF bands, allowing for full duplex transmission. The ground segment will be based upon a Software Defined Radio (SDR) to enable an easier and more flexible configuration. The SDR-platform used is the Ettus Research USRP, supported by a GNU Radio implementation on a computer. The link layer packet protocol implemented in the prototype is NGHam, a link protocol partly inspired by AX.25. In order to improve the link reliability, it features Reed Solomon codes for Forward Error Correction (FEC). This makes the data transmission more robust compared to i.e. AX.25, which does not implement FEC on the link layer directly. The required GNU Radio modules have been designed and implemented. An end-to-end communication between the USRP and the NUTS VHF module has been proved. A ground station based on traditional HAM radio equipment requires several bits of hardware, such as a radio, TNC or third part modems in order to enable packet transmission. By replacing this with a SDR setup the ground station will be more flexible; it will be easier to receive data from different satellites that might be using different link protocols and message formats. Utilising open source software, such as GNU Radio, gives radio amateurs around the world the opportunity to receive data from NUTS using cheap SDR hardware such as the RTLSDR USB dongles. Finally, as an SDR system can support a wide range of frequency bands, it will be easy for other project groups to implement support for their satellite mission using such an SDR based system. Support for other link protocols can easily be implemented. Messages received from the satellite(s) can easily be made available online. The 4S Symposium 2016-A Løfaldli 1
Small satellites and autonomous vehicles have greatly evolved in the last few decades. Hundreds of small satellites have been launched with increasing functionalities, in the last few years. Likewise, numerous autonomous vehicles have been built, with decreasing costs and form-factor payloads. Here we focus on combining these two multifaceted assets in an incremental way. The first goal is to create a highly reliable and constantly available communication link for a network of autonomous vehicles, taking advantage of the small satellite lower cost, with respect to conventional spacecraft, and its higher flexibility. We have developed a test platform as a proving ground for this network, by integrating a satellite software defined radio on an unmanned air vehicle, creating a system of systems. Several experiments have been run successfully. After this first step is fully operational, we could, in practice, move on towards a cooperative network of autonomous vehicles and small satellites.
Conference Paper
National Aeronautics and Space Administration (NASA) is developing an on-orbit, adaptable, Software Defined Radios (SDR)/Space Telecommunications Radio System (STRS)-based testbed facility to conduct a suite of experiments to advance technologies, reduce risk, and enable future mission capabilities. The flight system, referred to as the “SCAN Testbed” will be launched on an HTV-3 no earlier than May of 2012 and will operate on an external pallet on the truss of the International Space Station (ISS) for up to five years. The Communications, Navigation, and Networking reConfigurable Testbed (CoNNeCT) Project, developing the SCAN Testbed, will provide NASA, industry, other Government agencies, and academic partners the opportunity to develop and field communications, navigation, and networking applications in the laboratory and space environment based on reconfigurable, software defined radio platforms and the Space Telecommunications Radio System (STRS) Architecture. Three flight qualified SDRs platforms were developed, each with verified waveforms that are compatible with NASA's Tracking and Data Relay Satellite System (TDRSS). The waveforms and the Operating Environment are compliant with NASA's software defined radio standard architecture, STRS. Each of the three flight model (FM) SDRs has a corresponding breadboard and engineering model (EM) with lower fidelity than the corresponding flight unit. Procuring, developing, and testing SDRs differs from the traditional hardware-based radio approach. Methods to develop hardware platforms need to be tailored to accommodate a “software” application that provides functions traditionally performed in hardware. To accommodate upgrades, the platform must be specified with assumptions for broader application but still be testable and not exceed Size, Weight, and Power (SWaP) expectations. Ideally, the applications (waveforms) operating on the platform should be specified separately to accommo- ate portability to other platforms and support multiple entities developing the platform from the application. To support future flight upgrades to the flight SDRs, development and verification platforms are necessary in addition to the flight system. This paper provides details on the approach used to procure and develop the SDR systems for CoNNeCT and provide suggestions for similar developments. Unique development approaches for each SDR were used which provides a rare opportunity to compare approaches and provide recommendations for future space missions considering the use of an SDR. Three case studies were examined. In two cases, the SDR vendor (General Dynamics and Harris) was the integrated platform and waveform provider. In these cases, the platform and waveform requirements were considered together by the vendor using high level analysis to support the division of the requirements. In the Harris SDR case, the platform and waveform specification was then integrated into a single document. This case study was for a first generation platform, which offers significant processing and reconfigurablility, but is not optimized for SWaP. This provides a test bed platform for many investigations of future capabilities, but requires additional SWaP than optimized flight radios. In the GD case, the specifications were provided separately. The GD SDR leverages existing platforms with minor changes to the Radio Frequency (RF) portions. The most significant change to the CoNNeCT GD SDR from previous platforms was the addition of a reconfigurable processor. The capability tests the next generation SDR, but offers limited capacity and reconfigurability. In the case of the JPL SDR, the platform was developed by JPL and Cincinnati Electronics. Goddard Space Flight Center (GSFC) provided a waveform that was developed on a ground-based development platform, and Glenn Research Center (GRC) ported the waveform to the flight platform and performed the integrated test and accepta
High speed, low cost telemetry access from space development update on programmable ultra lightweight system adaptable radio (pulsar)
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