Prototype for Nanosatellite Optical Downlinks
Recommended reading in Optical Engineering.
As constellations of small satellites are becoming an area of growing commercial interest to support demands for global information and remote Internet connectivity, innovative approaches are needed for affordable and power-efficient, high-data-rate communications.
This is typically the realm of radio-frequency data links. However, the cost, size, weight, and power constraints of nanosatellites are making this approach impractical.
A recent Optical Engineering paper by Emily Clements and her colleagues at the Massachusetts Institute of Technology (USA) details a nanosatellite optical downlink experiment (NODE) that takes a free-space optical approach to this problem. The design is based on commercially available erbium-doped fiber amplifier transmitters, linear-mode avalanche photodiode detectors, and reasonably sized ground receiver optics in order to make it commercially viable.
To resolve the key tradeoff between required laser power and transmitter beamwidth, both the onboard and ground elements of the data link employ fast-steering mirrors to maintain fine beam pointing and link margin.
The authors of “Nanosatellite optical downlink experiment: design, simulation, and prototyping” anticipate maintaining data rates over 10 Mbps from 400 km low-Earth orbits with 30-cm-diameter ground receiver optics, and 50 Mbps out to the horizon with 1-meter-diameter optics.
If you have any interest in satellite communications, I encourage you to review their thorough engineering design.
Clements’ coauthors are Raichelle Aniceto, Derek Barnes, David Caplan, James Clark, Iñigo del Portillo, Christian Haughwout, Maxim Khatsenko, Myron Lee, Rachel Morgan, Kathleen Riesing, Hyosang Yoon, Caleb Ziegler, and SPIE members Kerri Cahoy, Ryan Kingsbury, and Jonathan Twichell.
Source: dx.doi.org/10.1117/1.OE.55.11.111610
–SPIE Fellow Michael T. Eismann is editor-in-chief of Optical Engineering and a member of the SPIE Publications Committee.
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