The communication systems is an essential component of a mission and its role on scientific instruments. The evolution of the type of data, their usage since the first Mars missions and their roles on these missions have evolved and will be described during this presentation The data communication usage, evolution will be presented from a technical and utilization point of view, and what are the advantages and limits of the current systems confronted to the current technological limits and its usage in a space environments.

1. Image Credit: IPNSIG
Data communication
and
Mars missions
Stephan Gerard
Association Planète Mars (APM)
stephan.gerard@laposte.net
12th European Mars Conference
EMC12 – Munich - 13 Oct 2012

2. Summary
1) Introduction
2) Data Communication
3) Communication infrastructure
4) Mars missions
5) Mission data
6) Future communication technologies
7) Conclusion
8) Questions
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3. Introduction
If no communication:
=> no data transmitted to Earth
=> no scientific data
=> we have a problem !!!
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4. Data Communication
Mars communication challenges
● Large transmission delays
RTT between Earth and Mars varies between:
● 7min and 46min
● Great distance
● between 55.7 and 401.3 million km
● Limited bandwidth available
● Disrupted links (orbital visibility)
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5. Data Communication
Mars communication challenges
● Error rates
● Noisy communication links
● Limited time frame
● Power available on lander or rover
● Buffer capacity
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6. Data Communication
Communication systems
2 types of communications:
➢ “Long Haul” between Mars and Earth
➢ “Short Haul” or “Proximity” between the orbiter
and Mars surface
Antennas:
● Low gain antenna is omni-directionnal used as a
backup to high gain antenna
● High gain antenna is directionnal
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7. Data Communication
CCSDS
● CCSDS = Consultative Commitee for Space Data
Systems
● Multi-national forum since 1982.
● CCSDS has its 30th anniversary this year.
● Develop standards for space data communications.
● CCSDS has been founded by 11 space agencies.
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8. Data Communication
CCSDS
● CCSDS standards independent of the underlaying bus
architecture.
● ESA mandates that all missions to be CCSDS
compatible.
● Proximity-1 Space Link protocol (UHF1) is the
standard used for relay communications by all the
missions currently at Mars since Mars Odyssey and
is designed to ensure error-free delivery of data.
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9. Data Communication
Radio frequencies
X-band:
● microwave frequency
Transmit: 7145MHz-7190Mhz
Receive: 8400MHz-8450Mhz
● current standard in communications
● is used for long range communications
● used between rovers and Earth
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10. Data Communication
Radio frequencies
UHF band:
● Ultra High Frequency (300 to 3 000 MHz)
from 390 to 450MHz on Mars missions
● used between landers, rovers and orbiting
spacecrafts
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11. Data Communication
Radio frequencies
Ka-band:
● microwave frequency
Transmit: 34200MHz-34700MHz
Receive: 31800MHz-32300MHz
● used as a secondary link between landers and
orbiters
● previously untested radio frequency
● Frequency x 4 allow an higher data rate than using
X-band
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12. Image Credit: NASA / JPL
Telecommunications for Mars Rovers and Robotic Missions
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13. Communication infrastructure
DSN - Deep Space Network
NASA / JPL
● DSN is present in 3 locations (Goldstone, Madrid,
Canberra) to have full day coverage.
● DSN has extremely large antennas:
- 70 meter
- 34 meter HEF (High Efficiency)
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14. Communication infrastructure
DSN Deep Space Network
NASA / JPL
Mars missions are not the only mission using
interplanetary communications infrastructure.
Communication time frame windows must be shared
with the other missions.
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15. Communication infrastructure
ESTRACK
ESA Tracking Station Network
● Only New Norcia, Cebreros and Malargüe have or
will have 35 meter deep-space antennas
● 35m Deep Space Antenna stations primarily use the
X-band
● S-band (2025-2300 Mhz), Ka (18.1-32.3 GHz) and
X-Band (7145-8500 Mhz)
● Data rates vary depending on the mission but
typically range from 256 Kbit/s to 8 Mbit/s
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16. S. Gerard - EMC12 Munich - 13 Oct 2012 16 1

17. Mars missions
Current active missions
Mars Odyssey (ODY) (2001 – USA)
Mars Express (MEX) (2003 – EU)
Opportunity (MER-B) (2003 – USA)
Mars Reconnaissance Orbiter (MRO) (2005 – USA)
Mars Science Laboratory (MSL) (2011 – USA)
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18. Mars missions
Viking 1 & 2
➢ Sent data directly back to
Earth using UHF relay radio
but most often via the
Viking orbiter
➢ Science data rate via relay
orbiter at 250, 500, and
1000 bits/s
Image Credit: NASA
➢ Science data rate via direct
link at 250, 500, and 1000
bits/s
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19. Mars missions
Pathfinder rover
“Sojourner”
➢ UHF radio systems
➢ Direct communication from
Mars surface to Earth
➢ Limited transmitter
➢ Communication weak and
data reliability limited
➢ Limited data rate
Image Credit: NASA
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20. Mars missions
Mars Odyssey Orbiter
➢ Odyssey is used as a data
relay
➢ UHF and X-band frequencies
➢ X-band transfer rates of up to
128 kb/s
➢ Has approx. 260Mbit of
memory allocated for surface
vehicule.
Image Credit: NASA/JPL-Caltech
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21. Mars missions
MER rover
“Opportunity & Spirit”
➢ X-band & UHF systems
➢ Use Proximity-1 (Prox-1)
protocol for relay
communications
➢ 120 Mbits allocated onboard
memory of Mars Odyssey
➢ Data rate using UHF: 8, 32,
Image Credit: NASA/JPL/Cornell University
128, 256 kbps
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22. Mars missions
Mars Express
➢ MEX is used as a data relay
➢ UHF and X-band frequencies
➢ Use Proximity-1 protocol
Image Credit: ESA
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23. Mars missions
Phoenix Mars Lander
➢X-band & UHF system
➢ Use Proximity-1 (Prox-1)
protocol
➢ Data rate UHF: 8, 32, 128,
256 kbps
➢ Can use MEX orbiter as
backup data relay
Image Credit: NASA/JPL
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24. Mars missions
Mars Science Laboratory rover
“Curiosity”
1st rover to have an Electra
transceiver
➢ X-band & UHF system
➢ Use MRO and ODY as data
relay
➢ Cross support with MEX
➢Use Proximity-1 Space Link
Protocol (Prox-1)
Image Credit: NASA/JPL-Caltech
➢ Use “store-and-forward” mode
of communications
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25. Mars missions
Mars Reconnaissance Orbiter
➢ MRO is used as a data relay
➢ Use X-band and Ka-band
➢ can send data back to Earth
> X 10 than previous
missions.
➢ sends data to Earth for 10
to 11 hours per day
➢ Data rates: from 0.5Mbits/s
Image Credit: NASA/JPL
to 4 Mbits/s
➢ Predicted total amount of
data: 34 terabits
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26. MER telecommunication
architecture
Image Credit: NASA / JPL
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27. Mars missions
Orbiters as data relay
with Earth
● Mars Odyssey acts as a data relay for MER.
● Currently, ODY, MEX and MRO are used as data
relay for Mars missions.
● MRO is able to send data back to Earth more than
10 times faster than previous missions.
● Future ExoMars orbiter will also act as a data relay
in jan 2019
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28. Mars missions
Data transferred from Mars
Amount of data received from Mars via MRO
177 223 Terabits
1 Terabits = 10 power 12 bits
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29. Missions data
Data rates
MRO
● A 3 meter long high gain antenna and 100 watt.
● 160 gigabits of solid-state memory
● Data rate at a maximum of around 6 Mbit/s when the
distance between Earth and Mars is minimum (55.7
million km)
● Data rate at a minimum of 0.6 Mbit/s when the distance
between Earth and Mars is maximum (401.3 million km)
● Time of transmission during science phase: 8h/day
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30. Missions data
Data rates
Martian rovers can send data Direct To Earth (DTE) at
a rate from 3.5kb/s to 12kb/s.
Data rate to an orbiter is at constant rate of 128kbit/s
but varies between 128kb/s or 256kb/s
The rover can only transmit direct to Earth for around
3h/day due to power and thermal limitations.
Odyssey can also operate in bent-pipe mode: downlink
to Earth while at the same time receiving data from
landers using UHF system.
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31. Missions data
Data rates
A rover communicate with an orbiter during 8min/sol
For comparison, in 8min, 60Mb could be transmitted
during a sol.
The same 60Mb would take between 1.5h and 5h to
transmitted direct to Earth.
InSight mission is planned to send more than 29Gb in
1 Martian year.
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32. Future communication technologies
Mars communications projects
● The purpose of these new projects are:
➢ to reduce time latency between Earth and the
remote mission spacecraft
➢ to improve reliability and reduce errors code
transmission
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33. Future communication technologies
Mars communications projects
To improve data bandwidth which increase with
better onboard instruments and new needs.
Test new technologies like Laser Communication and
new protocols (DTN)
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34. Future communication technologies
Optical space communications
Optical space communication also know as laser
communication or lasercom
● A demonstrator is currently done with Laser
Communications Relay Demonstration (LCRD).
● The lasercom system would increase the data rate to
100Mbps.
● A high resolution image would arrive on Earth in 5
minutes rather than in 90 minutes using MRO.
● MAVEN mission will use optical communications
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35. Future communication technologies
Optical space communications
Image Credit: JPL/CalTech
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36. Future communication technologies
Delay Tolerant Network (DTN)
● The InterPlanetary Network (IPN) is also associated
in DTN project.
● Demonstrators are currently running on ISS
● Store and forward method
Factsheet - Disruption Tolerant Networking for Space Operations (DTN)
http://www.nasa.gov/mission_pages/station/research/experiments/DTN.html
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37. Future communication technologies
IPNSIG
● IPNSIG (InterPlanetary Networking Interest Group)
● A communication system with networking protocols to
handle signal delay and connectivity disruption
● The Space Internetworking Strategy Group has
published a document the document “Operations
Concept for a Solar System Internetwork (SSI)” in
October 2010 ( IOAG.T.RC.001.V1 )
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38. Future communication technologies
IPNSIG
Image Credit: IPNSIG
The red-dotted data flows use DTN protocols.TCP/IP or other low latency protocols are the yellow and
blue-dotted data flows.
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39. Conclusion
Since the 1st missions to Mars, the amount of data
transmitted to Earth has increased a lot.
More bandwidth are needed
Data communications are an important part of the
mission.
Data are used by the scientific communities
and also for public outreach.
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40. Conclusion
Usage of CCSDS communication standards.
New technologies and standards are currently
tested to allow more and more data to be send
back to Earth with a minimum of disruption.
Communication is a key element
for future missions on Mars.
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41. Questions
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42. Image Credit: NASA / JPL / Caltech
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43. References
Mars missions – JPL / NASA
http://mars.jpl.nasa.gov/
NASA – Space Communications and Navigation
https://www.spacecomm.nasa.gov/
CCSDS
Consultative Committee for Space Data Systems
http://public.ccsds.org
IPNSIG
InterPlanetary Networking Special Interest Group
http://ipnsig.org
DTNRG
Delay-Tolerant Networking Research Group
http://www.dtnrg.org
DESCANSO
Deep Space Communications and Navigation Systems Center of Excellence
http://descanso.jpl.nasa.gov
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