The Psyche mission is on its way to study the metallic asteroid of the same name, and on its journey, continues to test the communication system of the future. Laser light was sent from Earth to Psyche on July 29, when the spacecraft was located 460 million kilometers (290 million miles) from our planet.
This is not the first transmission using a laser to or from Psyche – the spacecraft has, in the past, sent data, images, and even a cat video – but this is the farthest yet. The distance is actually the farthest possible distance between Earth and Mars, giving us an idea of what might be possible in the future.
“The milestone is significant. Laser communication requires a very high level of precision, and before we launched with Psyche, we didn’t know how much performance degradation we would see at our farthest distances,” Meera Srinivasan, the project’s operations lead at NASA’s Jet Propulsion Laboratory (JPL) in Southern California, said in a statement. “Now the techniques we use to track and point have been verified, confirming that optical communications can be a robust and transformative way to explore the Solar System.”
The whole Deep Space Optical Communications setup is experimental, looking at what might be possible with current tech and informing what could be built in the future. The team conducted experiments at several different distances to establish how much data could be transmitted depending on the distance.
At 53 million kilometers (33 million miles) from us — which is around the closest possible distance between Mars and Earth — the maximum data rate was 267 megabits per second. That’s like a good broadband download speed – and it is coming from one-fifth of the distance between the Earth and the Sun.
Psyche was quite a distance away.
Image Credit: NASA/JPL-Caltech
On June 24, when Psyche was about 390 million kilometers (240 million miles) away, the sustained downlink rate was 6.25 megabits per second with a peak of 8.3 megabits per second. It’s a dramatic reduction for sure, but still 100 times faster than communications using radio waves. The team was able to download almost 11 terabits of data in this first demo phase.
“A key goal for the system was to prove that the data-rate reduction was proportional to the inverse square of distance,” said Abi Biswas, the technology demonstration’s project technologist at JPL. “We met that goal and transferred huge quantities of test data to and from the Psyche spacecraft via laser.”
The next step for the mission is technically an easy one: It needs to turn on again. It is currently powered down and will be powered up on November 4 to demonstrate that it can operate for at least one year.
“We’ll power on the flight laser transceiver and do a short checkout of its functionality,” said Ken Andrews, project flight operations lead at JPL. “Once that’s achieved, we can look forward to operating the transceiver at its full design capabilities during our post-conjunction phase that starts later in the year.”
Psyche will continue to orbit in the inner Solar System for the next several years. In 2029, the spacecraft will reach asteroid 16 Psyche and begin orbiting until at least late 2031.
