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Laser for Satellite to Satellite Communications

Posted by michael on from the doubles-as-death-ray dept.

heby writes: "Last night ESA successfully tested the first laser link between two satellites (SPOT 4 and Artemis). SPOT 4 is supposed to serve as a data communications relay between Artemis and the receiving station in Toulouse. The link is running at 50Mbps and the two satellites are currently orbiting at 832km and 31000km respectively.
According to ESA "The main challenge in establishing an optical link between satellites is to point a very narrow beam with extreme accuracy to illuminate the partner spacecraft flying at a speed of 7000 m/s." Way to go, ESA!"

4 of 170 comments (clear)

  1. Re:Line of Sight by Yazeran · · Score: 4, Interesting
    Well it would only be a problem if a large object (like another satelite) came to be in-between. Even laser light diverge at these distances, so you only point the beam at the other satelite. The beam-diameter would be more than 1 meter, and if a small dust-grain was to come in-between, it would be impossible to detect it. Remember, that light do bend arround corners (quantum mechanics; slit experiments) so even if the dust grain vas directly between the laser and the sensor on the other satelite, it would not 'turn off' the beam. You vould only notice (if at all) a small decrease in light intensity.

    Besides, i think they would have included some error-recovery system in their data link, this is standard for all data-transmission links (even home networks on ne2000 compliant netcards).


    The real feat here is that they could point a narro beam at a mowing target and keep it there (autonomously that is).


    The trick could be to use the gradual decrease in beam intensity as you move to the outer portions of the beam, and send this information back to the other satelite to re-adjust. If you used several sensors spaced some distance apart, you could determine the direction the beam has to be moved (Theoretically that is). I do not know if this could be done in real life as i'm no laser specialist or space engineer.


    Yours Yazeran


    Plan: To go to Mars one day with a hammer.

  2. Re:Can you imagine... by Anonymous Coward · · Score: 0, Interesting

    ...my cock tearing appeart you mothers ass while your sista is licking my ballz?

  3. Re:Side effects of lasers? by abrett · · Score: 2, Interesting

    According to the specs, the link laser will operate at a mean power of 60mW. Using F = P/c, we get a force of roughly 200fN (200 femto Newtons!). Just to give you some idea of the effect that would have, Artemis' mass at launch is 3100kg, so this means that if it was to emit a 60mW beam in the same direction for 10 years, its speed would change by approximately .01 mm per sec.

  4. Re:Sat2Sat communications evolution by blair1q · · Score: 3, Interesting

    > With RF systems, you would need some tracking for any long term communications, but you could base that purely on satellite ephemeris, a much simpler problem.

    You'd start the beam search using ephemerides, but RF crosslinks do use signal-strength components for feedback-based antenna steering control.

    You're dead right that getting it done with lasers is several orders of magnitude more cool.

    This also has the potential to tack a few more zeroes onto the accuracy of orbital position determination. Interferometry could get you sub-nanometer resolution. I can't imagine why you'd want that, but I can imagine someone else can.

    --Blair