NASA is exploring its communications options with Mars.
The space agency this week issued a Request For Information that looks to explore options where it would buy commercial communications services to support users at Mars, including landers and rovers and, potentially, aerobots and orbiters.
From NASA: “ In this model, the commercial provider would own and operate relay orbiter(s), and NASA would contract to purchase services over some period of time. In exploring this model, NASA encourages innovative ideas for cost-effective approaches that provide backward-compatible UHF relay services for existing landers, as well as significantly improved performance for future exploration activities. One example is deploying optical communications for Mars proximity operations and/or deep-space communications.”
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NASA noted that it recently demonstrated optical communications from the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft at the Moon to Earth, with download rates of 622Mb/sec. It also demonstrated an error-free data upload rate of 20Mb/sec transmitted from the primary ground station in New Mexico to the spacecraft orbiting the Moon. NASA said it also “welcomes interactions with relay infrastructure that might be deployed in support of other Mars commercial objectives.”
NASA said its current Mars relay infrastructure is aging, and there is a potential communications gap in the 2020s. That’s why NASA is interested in exploring alternative models to sustain and evolve the Mars relay infrastructure. The current strategy has been cost effective to date, because NASA has launched science orbiters to Mars on a steady cadence; the cost of the relay infrastructure has effectively been limited to the incremental cost of adding a relay payload to them.
Such efficiency is expected to continue with the arrival of the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft at the red planet on September 21, 2014, and the European Space Agency’s ExoMars/Trace Gas Orbiter in 2016. Each orbiter carries a NASA-provided Electra relay payload.
According to NASA, Mars landers and rovers are highly constrained in mass, volume, and power. One consequence of these constraints is a substantial restriction in the data rates and volumes that can be communicated on the direct link between the Mars surface spacecraft and Earth. For instance, at large Earth-Mars distances, the Curiosity rovers X-band direct-to-Earth (DTE) link operates at data rates of less than 500b/sec when communicating to a Deep Space Network 34m antenna. Such data rates are not sufficient to support typical surface exploration needs, NASA says.
To address this limitation in DTE bandwidth, the Mars Exploration Program (MEP) has employed a strategy of including a proximity-link telecommunication relay payload on each of its Mars science orbiters, NASA stated. Currently, operating in the UHF band (390-450 MHz), these relay payloads establish links with landers and rovers on the surface as they fly overhead, supporting very high-rate, energy-efficient links between orbiter and lander. The orbiters, with much larger high-gain antennas and higher power transmitters, can then take on the job of communicating on the long-haul link back to Earth, the space agency said.
For now, NASA has two relay orbiters in operations at Mars: the Odyssey spacecraft, launched in 2001, and the Mars Reconnaissance Orbiter (MRO) spacecraft, launched in 2005. These orbiters enable communication links from the Curiosity rover operating at rates of up to 2 Mb/sec Similar relay support has been provided to the prior Spirit rover and Phoenix lander missions and continues to be provided to the Opportunity rover.
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