LuNet

Integrated Network Architecture forSustained Human and Robotic Exploration

Gary NoreenTelecommunications ArchitectCommunications Architecture and Research SectionJet Propulsion Laboratory(818) 354-6048gary.k.noreen@jpl.nasa.gov

GKN-2March 11, 2005 LuMarsNet

Agenda

• Lunar Telecommunications Network

– Presumed Requirements– Strawman Architecture

· Ground Segment· Space Segment

› Orbit Design› RF Payload

· Frequency Plan

• Mars Telecommunications Network

– Presumed Requirements– Strawman Architecture

· Ground Segment· Space Segment

› Orbit Design› RF Payload

· Frequency Plan– Emergency Communications

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GKN-3March 11, 2005 LuMarsNet

Strawman Return Link Requirements

User Channel Content # of Channels

Channel Rate Total Rate

Operational

BaseSpeech 2 10 kbps 20 kbps

Engineering 1 100 kbps 100 kbps

Astronauts

Speech 4 10 kbps 40 kbps

Helmet camera 4 100 kbps 400 kbps

Engineering 4 20 kbps 80 kbps

Human Transports

Video 2 1.5 Mbps 3 Mbps

Engineering 2 20 kbps 40 kbps

Robotic Rovers

Video 4 1.5 Mbps 6 Mbps

Engineering 4 20 kbps 80 kbps

Aggregate 10 Mbps

High Rate

Base HDTV 1 20 Mbps 20 Mbps

Human Transports

HDTV 1 20 Mbps 20 Mbps

Hyperspectral Imaging 1 150 Mbps 150 Mbps

Robotic Rovers

Radar 1 100 Mbps 100 Mbps

Hyperspectral Imaging 1 150 Mbps 150 Mbps

Aggregate 440 Mbps

GKN-4March 11, 2005 LuMarsNet

Strawman Lunar Network Architecture

• Terrestrial ground network to support lunar exploration– Spacecraft en route to and

near the moon– Earth connection to lunar

relay orbiters, lunar stations• Lunar relay constellation

– 3 Lunar Telecom Orbiters– South Pole base– Limited far side coverage

• Malapert Station– Repeater on summit of

Malapert Mountain near lunar South Pole

GKN-5March 11, 2005 LuMarsNet

Terrestrial Ground Network• 3 Earth complexes ~120° apart (DSN)• Eight 12 m antennas at each complex

– 1 for each LTO – 3 total– 1 for Malapert Station– 2 for spacecraft en route & on near side

of moon– 2 backup

Potential Terrestrial Ground Network Data Rates

*Assumes the moon is within the beamwidth of the ground antenna.

Spacecraft Antenna

Frequency Band

Return* (10 W) Forward (200W)

Allocation Rate Allocation Rate

1 m HGA

S-band 2.2-2.29 GHz 5.2 Mbps 2.025-2.11 GHz 1 Mbps

X-band 8.45-8.5 GHz 70 Mbps 7.19-7.235 GHz 13 Mbps

Ka-band 25.5-27 GHz 530 Mbps N/A N/A

Omni S-band 2.2-2.29 GHz 12.5 kbps 2.025-2.11 GHz 5 kbps

GKN-6March 11, 2005 LuMarsNet

Strawman Lunar Relay Constellation

• 3 Lunar Telecom Orbiters (LTO)• Communications payload

– 15 dB UHF relay MGA– 1 m diameter relay HGA– 1 m diameter Earth HGA

• Inclined elliptical orbits– Quasi-stable– Apoapses stay in southern hemisphere– Presumed requirements: at least 2

orbiters in view of base near lunar pole all the time

GKN-7March 11, 2005 LuMarsNet

Quasi-Stable Lunar Relay Orbits• Perilune altitude 125 km to 1150 km; maximum range to pole is 11,600 km• Mean pass length over pole is 10.6 hours; mean gap time 3.5 hours.• Inclination between 46º and 63º• Eccentricity between 0.56 and 0.72• At least two orbiters 10° or higher elevation all the time from polar base

GKN-8March 11, 2005 LuMarsNet

• 1 m relay antenna used in calculations• 1.5 m relay antenna would provide

performance comparable to TDRS– TDRS 4.5 m Single Access antenna– Geostationary altitude (earth): 35,000 km– Maximum LTO altitude: 11,600 km

1 m Orbiter Antenna Return (User-to-Orbiter) Forward (Orbiter-to-User)

User Antenna Band Frequency Power Rate Frequency Power Rate

-3 dBS-band 2.2-2.29 GHz

4 W 10 kbps2.025-2.11 GHz

4 W 10 kbps

0.25 m15 W 1.5 Mbps 25 W 1.5 Mbps

Ka-band 37-37.5 GHz 35 W 1 Gbps

Relay Data Rates

GKN-9March 11, 2005 LuMarsNet

• One sustained human base– Mid-latitude location

• Other requirements assumed similar to lunar case, including customer set

• Big differences– Two-way light time 6.3 to 44.5

minutes– Mars-Earth range extremely

high (up to 2.67 AU) – must cope with incredibly low signal levels

Mars Network Strawman Requirements

GKN-10March 11, 2005 LuMarsNet

Strawman Mars Network Architecture

• Terrestrial ground network to support Mars exploration– Spacecraft en route to and

near Mars– Earth connection to Mars

relay orbiters, Mars stations• Mars relay constellation

– 2 Mars Communication Satellites (Comsats)

– Areostationary orbits· Partially overlapping

footprints· Human base in view of both

GKN-11March 11, 2005 LuMarsNet

Terrestrial Ground Network for Mars Exploration

• 3 Earth complexes ~120° apart (DSN)• Arrays of 12 m antennas at each complex

– The DSN is planning arrays of 400 12 m antennas at each complex

– Array of 10 12 m antennas = one 34 m– Array of 40 12 m antennas = one 70 m

• A spacecraft with a 6 m HGA and a 1 kW transmitter at maximum Mars range can send 500 Mbps to an array of 180 12 m antennas

• Optical may be deployed if proven viable by Mars Telecommunications Orbiter

GKN-12March 11, 2005 LuMarsNet

Strawman Mars Comsat Constellation

Mars Base

• Sacagawea & Pocahontas Mars communication satellites• Areostationary orbits (akin to geostationary)

– 17,033 km altitude– Overlapping footprints at human base– Extended coverage for robotic exploration

• Communications payload– 6 m High Gain Antenna for deep space link (Earth) – optical optional– 2.2 m High Gain Antenna for proximity link (Mars)

GKN-13March 11, 2005 LuMarsNet

• Areostationary altitude: 17,033 km• Geostationary altitude: 35,000 km• Proximity link performance

– 2.2 m antenna → comparable to TDRS– 7 m antenna → comparable to Thuraya

Relay Data Rates

THURAYA SATELLITE PHONE

AntennaBand

Return ForwardOrbiter User Power Rate Power Rate

2.2 m-3 dB X 35 W 110 kbps 10 W 25 kbps

0.25 mX 90 W 130 Mbps 30 W 31 MbpsKa 35 W 800 Mbps 8 W 210 Mbps

GKN-14March 11, 2005 LuMarsNet

Emergency Deep Space Communications

• Robotic deep space experience– Sun-point mode in the event of an anomaly– Accept very low data rates (10 bps)

• More robust communications may be necessary for humans– Gemini 8: spacecraft may spin uncontrollably– Humans are likely to demand voice communications

· At least 1 kbps· Additional engineering data to monitor humans as well as CEV

• Sending back 1 kbps from a spinning spacecraft near maximum Mars range is very challenging– Inadequate margin even assuming array of 400 12 m antennas on the

ground and 1 kW transmitter on the spacecraft

GKN-15March 11, 2005 LuMarsNet

Conclusions

• A modest network of 3 LTOs and 24 12 m ground antennas could provide continuous redundant links to human and robotic missions to the near side of the moon and to one of the poles. JPL has identified a stable orbit for the LTOs that maintains near-ideal phasing.

• A network of two areostationary Mars communications satellites in conjunction with large arrays of small ground antennas at Earth could provide continuous redundant links to human and robotic missions in the vicinity of a mid-latitude Martian base and receive high rate data (500 Mbps).

• The greatest challenge may be the provision of emergency communications services to human missions en route to Mars.