This LEMNOS page on NASA's Explorations and Space Communications site says:

The Integrated Laser Communication Relay Demonstration (LCRD) Low-Earth Orbit (LEO) User Modem and Amplifier Terminal (ILLUMA-T) will fly aboard the International Space Station as the first demonstration of a fully operational, end-to-end optical communications system.

If I understand correctly, in this demonstration one end would be the ISS, and the other would be on Earth. The paragraph continues:

ILLUMA-T will provide the space station a state-of-the-art optical communications terminal with improved size, weight and power over comparable radio-frequency communications systems. It will communicate data from low-Earth orbit to the ground through a relay satellite in geosynchronous orbit, leveraging optical communications technologies from the upcoming LCRD mission and the Lunar Laser Communication Demonstration (LLCD) that orbited the moon from 2013 to 2014. Optical technologies have the potential to greatly increase the amount of scientific data transferred from space to ground, supporting multiple channels of ultra-high-definition video from space.

Question: Has a mission or specific satellite been named to be this relay satellite in GEO that the ISS will use for its end-to-end optical communication with a ground station? Is there a description and/or an estimated launch date for this satellite?

  • $\begingroup$ I must admit that the name is great! Makes me wonder whether the whole mission isn't a huge conspiracy ;-) $\endgroup$
    – ChrisR
    Jun 7, 2018 at 5:38

1 Answer 1


ILLUMA-T will work with the LCRD flight segment payload on Space Test Program Satellite-6 (STPSat-6); see page 4 of this document from SCAN.

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LCRD’s dual optical link system will allow it to serve as the first step in demonstrating optical communications for use in a next-generation space-based relay system and potentially provide early operational support for low Earth orbit (LEO) terminals. LCRD will also enable experimenters to characterize atmospheric effects on optical communications and validate atmospheric models. LCRD will advance optical communications technology toward infusion into both deep space and near-Earth operational systems, while growing the capabilities of industry sources to produce affordable optical communications systems and components for use on the ground and in space.

STPSat-6 is intended to carry a bunch of different payloads as part of the Space Test Program (STP-3) launch "no earlier than June 2019" on an Atlas V.

Basically, multiple test programs are working together to get the various parts into place when they can. It's probably a nightmare of project management.

  • $\begingroup$ I'm having difficulty asking questions as fast as you can answer them, thanks! ;-) $\endgroup$
    – uhoh
    Jun 7, 2018 at 5:53

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