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The Field of Optical Communications (view source)
Revision as of 19:50, 22 March 2016
, 19:50, 22 March 2016→MIT Lincoln Labs LLCD/LADEE
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==MIT Lincoln Labs LLCD/LADEE==
== MIT Lincoln Labs LLCD/LADEE ==
Nasa's Lunar Laser Communication Demonstration (LLCD) was a rousing success that demonstrated duplex laser communications at previously unheard-of speeds between lunar orbit and ground stations on Earth.
Nasa's Lunar Laser Communication Demonstration (LLCD) was a rousing success that demonstrated duplex laser communications at previously unheard-of speeds between lunar orbit and ground stations on Earth (These download speeds were at times faster than the ground lines on Earth when distributing downloaded scientific data). The LLCD's space component was attached as an optical payload to the larger scientific satellite LADEE.
The LLCD project operated on the 1.5-micron band with maximum downlink speeds of 622Mbs. The project featured a 1kHz squarewave acquisition signal and could measure its round-trip Time of Flight (TOF) to within 200 psec.
=== Mission Success and Demonstrations ===
The LLCD experiment is regarded as a great success. All systems operated at or above expected levels, and it was demonstrated that an optical link could be established without human-in-the-loop interaction.
==== High Speed Telemetry ====
The typical 50kbps telecommunications via RF were replaced during a lock-on window by a 2.7Mbps optical telemetry transmission. This information was then plotted graphically in real time against the slower RF data.
==== High Volume Download ====
During one experiment, test data from another LADEE experiment was transmitted via the optical link. The 1GB of data was transmitted in under five minutes (error -free). The same amount of data would have consumed every RF window for three days to transmit.
The information was then relayed to scientist on the ground using existing infrastructure that was often slower than the optical link itself. This process was executed several times at the request of LADEE scientists and gave them an unprecedented amount of data to process.
==== Webcam Livestream ====
==== Ground Station Handover ====
=== The Ground and Space terminals (LLGT and LLST) ===
The Lunar Lasercom Space Terminal (LLST) optics consisted of a 10cm reflective telescope capable of ~15uRad beam width. It was connected via fiber to the modem where transmissions up to .5W were processed. This module was used for uplinks as well. LADEE was the host satellite to this experiment, and LLST's optics were gimballed on a side-mount of the satellite.
The ground stations for the LLCD project consisted of the primary Lunar Lasercom Ground Terminal (LLGT), and the two backup terminals, the Lunar Lasercom OCTL Terminal (LLOT) and the Lunar Lasercom Optical Ground System (LLOGS).
The LLGT contained four 15cm 10W transmit telescopes and four 40cm Downlink telescopes. Its downlink telescopes were linked by fiber to an array of superconducting nanowire single photon detectors. All eight of these telescopes were then contained within an environmentally controlled enclosure. The entire LLGT device was transportable, and was thoroughly tested near MIT Lincoln Labs before being transported to White Sands where it stayed for the tests.
==JPL 1U Optical Comms Terminal==
==JPL 1U Optical Comms Terminal==