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New Kind of Orbit Could Ease Mars Communications

Posted by kdawson on from the crossing-gravitational-gradients dept.

japan_dan writes "An interesting way to enable Earth-Mars communication when the Sun occludes the direct radio line-of-sight: ESA proposes placing a pair of continuous-thrusting relay satellites, using a solar electric propulsion system — one in front and ahead of Mars, the other behind and below — with both following non-Keplerian, so-called 'B-orbits'. This means the direction of thrust is perpendicular to the satellites' direction of flight, allowing them to 'hover' with both Earth and Mars in view. Quoting from the Q&A: 'We found that a pair of relay satellites would only have to switch on their thrusters for about 90 days out of every 2.13-year period, and this solution would only increase the one-way signal travel time by one minute, so it could be effective.'" Here is the paper describing non-Keplerian orbits (PDF).

6 of 127 comments (clear)

  1. Wouldn't it make more sense.... by mark-t · · Score: 4, Interesting

    ... to park such a device at L4 or L5, where you wouldn't require *ANY* fuel to keep it in position?

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    1. Re:Wouldn't it make more sense.... by techno-vampire · · Score: 2, Interesting
      The only case where you need these relays is if the Sun is between Mars and Earth (or close enough to a direct line to make a hash of radio communications between Mars and Earth)

      The idea isn't exactly new, you know. George O. Smith wrote a series of stories about a relay station in the L4 point of Venus, The Venus Equilateral series, back in the '40s. It was a communications hub for the entire Solar System, and a hotbed of technological innovation. Great stories, still worth reading.

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    2. Re:Wouldn't it make more sense.... by BenSchuarmer · · Score: 2, Interesting

      I think the issue is better coverage on Mars.

      As I read it, the spacecraft would be positioned so that they each cover half Mars with no overlap or gaps.

      If the spacecraft were at the Legrange points, then the near/day side of Mars would have a large area that could see both spacecraft and far/night side of Mars would have a large area couldn't see either of them.

  2. Re:Not quite by Nadaka · · Score: 3, Interesting

    The original article was mentioning satellites following/leading mars. With the satellites in mars Lagrange points, the distance would be longer, though not entirely double.

    What the hell, I'll bother to do the math this time, using your figures of 150 Gm and 25 Gm that would result in a maximum distance from earth the a mars Lagrange point at about 350 Gm, plus the 250 Gm to mars gives a distance of ~600 Gm vs the strait line of 400 Gm. so its a ~50% increase in time.

    Of course I could get pedantic and claim I was talking about the difference in time. But that would be fudging to cover my my lazy ass failing to math.

  3. What about a Stationary Position about the Sun? by KJSwartz · · Score: 2, Interesting

    First: What is the purpose of 24 hour communications? If you need SOS messaging, signal recovery, or a simple heartbeat, use the sun as the point-of-reference.
    Second: A fleet of solar communications satellites could provide a solar GPS system.
    Third: These satellites could use Solar Propulsion and "hover" at a fixed distance from adjacent satellites. Solar sails could serve as a foundation for power generation (focused beam) and for data reception.

    Downsides: the sun is a noisy place for communications, as well as a dirty place to park objects with large surface areas.

  4. Use Solar Propulsion instead of propellants by KJSwartz · · Score: 2, Interesting

    If we're THAT CLOSE to the sun, it would be interesting to see how big a solar sail would need to be for a 364.245 day parking orbit. Use the dark side of Mercury as Network Control.