> When the satellite is in orbit around the moon and visible from Earth, one of three ground stations will shoot a laser towards its approximate location. The laser beam from Earth will scan a patch of sky and should illuminate the spacecraft at some point. When that happens, the spacecraft will begin transmitting its own laser towards the ground station and the two will lock on to each other. Once that happens, communications can begin.
Cool handshake.
I'm now imagining a science-fair / makerfaire type demo project – some Arduino and RaspberryPi pairs with a few RC servos, modulated laserpointers, and webcams – with a "ground station" searching for a "satellite" which might be a quadcopter or a kite or a helium balloon…
(And there's a Maker Faire here in Sydney later this year…)
I wonder how long the handshake takes. I imagine that the scan looks something like how CRTs work. But the triangulation back to the origin and whatnot seems like it'd take a certain amount of samples, or a pair of sufficiently-displaced sensors working in concert.
Does this technology require clear skies/do clouds block the laser?
>The ground stations are at White Sands in New Mexico, at a NASA Jet Propulsion Laboratory site in Wrightwood, California, and a European Space Agency site in Tenerife, Spain.
At least two of these stations are located in mostly-dry climate.
The laser uses infrared light with a wavelength of 1550 nm, where the atmosphere is typically transparent even with clouds or rain.