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I remember there was a test of optical communication and some data transfer from lunar orbit to earth, and I think the ISS uploaded (or downloaded-up? which is correct here?) a movie from earth.

In order to have the internet on Mars not end up to be too expensive and to extend the Deep Space Network (and here and DSNnow here) capability, optical seems to be a very important technology for the not-so-distant future.

Free space optical communications (no optical fiber) seems to be just made for space. With a wavelength of the order of 1 micron instead of 10 centimeters, transmission antenna can be smaller in diameter for the same gain. Receiving antennae can possibly be smaller - basically something like the kind of optical telescopes they use now for astrophotography - but that depends on nearby bright sources of light and data rate.

Were these tests successful? Have there been other tests? What's coming next?

Screenshot(s) of Deep Space Network Now

enter image description here

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The European Data Relay System has recently begun testing. It's for getting data from Earth orbiting satellites down to the ground quickly, without waiting for the satellite to pass over a base station.

Claimed data rate: "Up to 1800 Mbit/s" and "At least 50 TBytes/day". (Note: I don't see how these two figures equate.)

Here is the first big test: an image taken by Sentinel 1A, sent by laser to an EDRS satellite (in geostationary orbit) and beamed down direct to the base station in Germany. (Hi-res version)

The biggest advantage of all this is a Sentinel satellite in low earth orbit can pass its information to base with the minimum of delay, even when out of sight of a base station.

Here's a picture of one of the satellite-mounted laser communication terminals:

enter image description here

(Bigger version of the picture available here.)

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    $\begingroup$ There are two good answers, I chose this one because it describes what's being demonstrated right now. Don't worry about the data rates - maybe they will use multiple wavelengths (fibers can use 100 or more) and certainly some fancy modulation techniques 10 bits/sec per Hz has been demonstrated last year. The beauty of truly free space is that there won't be the same non-linearity and dispersion that even the best silica fiber has. Then there is linear polarization and circular and optical vortices- there are ways to pack packets! $\endgroup$ – uhoh Jun 4 '16 at 11:14
  • $\begingroup$ ...I'm not saying it's all easy, I just mean don't worry about the math right now. $\endgroup$ – uhoh Jun 4 '16 at 11:15
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The lunar mission which tested optical communication was LADEE. The ISS program you're thinking of is OPALS. Both tests succeeded, but neither was meant for ongoing operation. LADEE intentionally impacted the moon, and the US orbital segment of ISS currently uses S and Ku band radio communication through TDRSS.

The next proposed study on laser communication is LCRD, which hopes to fly on a commercial payload in 2019.

There is also a high probability that the next Mars orbiter will use optical communication. NASA has been interested in optical communications for Mars since at least 2008, as shown in this presentation from Jim Schier, Chief Architect for NASA’s Space Communications and Navigation Program at NASA Headquarters. Most recently, in April 2016 a request for information went out concerning this upcoming Mars orbiter, and the awards are due to come out this June, so stay tuned. Look for lasercomm, solar electric propulsion, a high-res camera, and ground-penetrating radar in the winning proposals.

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  • $\begingroup$ Great! Thanks for identifying the two previous demonstrations. It looks like you are focused mainly on NASA, there seems to be a few more space agencies "out there", just counting the terrestrial ones :) Are you releasing the results formally here, or just speculating? $\endgroup$ – uhoh Jun 4 '16 at 11:17

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