NASA has a communications problem: The radio frequencies used by spacecraft for communications are getting too busy. As more missions are sent into outer space, and as these missions carry increasingly sophisticated instruments, the amount of data that needs to be sent back to Earth is growing beyond the capacity of current radio communications systems.
The solution to this problem is to use higher frequencies, which can carry more data. But before any new communication system can be put into widespread use, it has to be tested.
That’s the aim of the Deep Space Optical Communications test, which has hitched a ride on the Psyche mission headed to the solar system’s main asteroid belt to test whether it’s possible to use lasers for more efficient communications. The experiment sent back its first test data last year, and earlier this year, it was able to send back actual spacecraft data successfully.
Now, DSOC has hit a new milestone, as it has completed its first phase of operations and has sent data from 290 million miles away — which is the same maximum distance that exists between Earth and Mars at their farthest apart.
“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,” said DSOC’s operations lead, Meera Srinivasan, 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.”
Before launching DSOC, the engineers were confident that laser communications were possible, and they had estimates for how accurate they would be over very long distances. But in any space technology, it is always important to check that things work in practice as well as in theory. One of the main challenges for DSOC was ensuring that the antennae on the ground and the spacecraft could be pointed toward each other accurately enough to send data over tremendous distances.
The team also wanted to test what data rates they could expect to see using laser communications from different distances. At 33 million miles away, comparable to Mars at its closest to Earth, DSOC achieved a bit rate of 267 megabits per second, which is similar to broadband internet speeds. At a much farther distance of 240 million miles, it still managed 6.25 megabits per second. You can see how much the distance causes the bit rate to drop, but the new rate is still much faster than is possible with current radio communication systems.
Now that the first part of the test is completed, the transceiver has been powered down. But the experiment isn’t over yet, as it will be powered on again next month to check that the hardware can survive a full year in space and continue to operate well.
“We’ll power on the flight laser transceiver and do a short checkout of its functionality,” said Ken Andrews, project flight operations lead. “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.”