CubeSats Could Use Laser Pointers to Transmit Data to Earth
Matthew Greenwood posted on December 21, 2018 |
(Image courtesy of MIT.)
(Image courtesy of MIT.)

Shoebox-sized CubeSats are much cheaper and quicker to build than conventional satellites. But their small size and low power means they transmit data at a slow trickle down to the ground.

Engineers at MIT may have a solution: a laser-pointing platform that enables CubeSats to transmit more data while using less power.

Most satellites typically send data using radio waves. Bigger satellites use larger antenna dishes or arrays to support sending massive amounts of data quickly—but CubeSats must rely on miniaturized transmitters that transmit at a much slower rate.

The new platform could potentially allow miniature satellites to send thousands of high-resolution images each time they fly over a receiver. Lasers use less power and are more compact than radio transmitters—and can transmit much more data in their tightly-focused beams. This would allow the small satellites to rapidly transmit terabytes of information.

But laser communications also have a significant drawback: because laser beams are much more focused than radio waves, they need to be pointed with much greater precision at receivers on the ground.

The MIT team developed a laser-pointing platform about the size of a coffee mug that uses a mirror, smaller than a fingernail, to bounce the laser down toward a ground receiver. The platform can adjust the angle of the mirror to change the laser’s direction.

The platform’s optical system uses two laser colors, or wavelengths: one beam to transmit data and the other to calibrate the laser’s aim. The beams bounce off the mirror and pass through a beam splitter that sends the data beam to its receiver and redirects the calibration beam to an onboard camera.

That camera also receives a calibration laser beam from the ground station. The system compares where on the camera lens the two beams land, using an algorithm developed by the researchers, and uses that data to tilt the mirror so the two beams arrive at the same spot—allowing the data beam to hit its target.

“It’s like the cat and mouse of two spots coming into the camera, and you want to tip the mirror so that one spot is on top of the other,” said Kerri Cahoy, associate professor of aeronautics and astronautics at MIT and co-author of the paper detailing the system.

The researchers verified the technique’s accuracy in the lab and are working with NASA to potentially test the entire system in orbit.

“I think this capability will make the whole CubeSat approach, using a lot of satellites in orbit so you can get global and real-time coverage, more of a reality,” said Cahoy.

Check out more developments in CubeSat technology at CubeSat to Attempt Solar Sail in Orbit.

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