Enabling Robotic and Human Exploration: A Relay Network for the Future of Mars Exploration
Roy E. Gladden, Charles H. Lee, Charles D. Edwards, Michelle A. Viotti, Richard M. Davis · 2021
Rationale: Why a Relay Network?A mission-enabling, next-generation relay capability at Mars is critical for supporting high-priority science and reconnaissance goals in the next decade and beyond.It would reduce the cost and risk of future Mars missions, relieving them of the need to carry their own direct-to-Earth communications systems (with attending mass and power requirements), and ensure an increased return on investment with greater data return from each mission.It would provide breakthrough increases in Mars telecommunication capabilities across a wide range of user spacecraft, with strategic benefits that include: 1. Continuous/near-continuous support to landers, rovers, and orbiters, with greatly increased instantaneous data rates and total data return.Currently, relay support to all surface assets returns a combined ~1.4 Gb/sol (via UHF), achieved via ~6 sporadic 10-30 minute relay sessions/sol; no relay services are available to low-altitude Mars orbiters.By contrast, a next-gen relay capability would provide continuous relay services at 200 Gb/sol in the same time (via X-band) for most of the surface of Mars (±40 deg latitude).In addition, for the first time, high-rate relay services for low-altitude Mars orbiters could also be continuously provided.Aggregate data return for all Mars missions is currently ~40 Tb/year, but this could be increased to over 1000 Tb/year in service to both science and reconnaissance for human precursor missions.2. Support to next-generation, data-intensive sensors.A next-gen relay capability would enable data-intensive investigations that have been unachievable to date.For example, mapping the spatial extent and depth of water ice in the near subsurface of Mars is a NASA goal for the next decade.This would require a synthetic aperture radar (SAR) and raw radar data returns that exceed present-day designs for directto-Earth communication systems.In addition, since late 2006, only a tiny fraction of Mars (~4%) has been mapped at HiRISE's 30 cm/pixel resolution at visible wavelengths.A next-gen relay network would enable both of these data-intensive objectives. Support for high-resolution mapping of Mars at increased temporal resolution.Periodic imaging of the same surface features at high resolution would revolutionize the detection of changes on the surface of Mars (e.g., new impact craters, gullies/recurring slope lineae, dust devil tracks, ice caps, shifting dunes, etc.).A next-gen relay network would enable these science and reconnaissance investigations.4. Support to orbital users, allowing low-cost "smallsat" orbiters to achieve "bigsat" science return.Currently, relay support for orbiter missions does not exist.As opportunities for low-cost and frequent access to Mars grows for NASA, other space agencies, and commercial partners, decadal-class science and reconnaissance capabilities become both affordable and achievable.Study results show that orbiters with an exceptionally modest telecom system would be able to achieve data returns more than twice that of the existing MRO downlink capability (see §2.1).This new class of relay service would enable emerging small orbital mission concepts freed of the need for high mass/power direct-to-Earth communication payloads and capable of decadal-class science at a fraction of the cost of today's large, complex orbiters.