NASA’s Deep Space Optical Communication (DSOC) technology demonstration has notched up another performance milestone as it approaches a year in space.
The laser communications demo, which is riding on board NASA’s Psyche spacecraft, has been breaking records as Psyche speeds toward its destination. In April, from 140 million miles (225 million kilometres) away from Earth it managed data transfer rates of 25 Mbps. On June 24, at 240 million miles (386 million kilometres), the demonstration achieved a sustained downlink data rate of 6.25 Mbps, peaking at 8.3 Mbps.
Although the figures are no longer high enough to merit sarcastic comparisons with Earthly broadband, they are considerably better than what could be achieved by a radio system using comparable power.
In the latest metric, recorded at the end of July when Psyche was 290 million miles (460 million km) from Earth, approximately the farthest Earth and Mars can be apart, the team managed to communicate with the experiment again. The feat was made all the more impressive by the fact Psyche had entered the daytime sky by then, and so only the one-metre telescope of the Optical Communications Telescope Laboratory (OCTL) at JPL’s Table Mountain facility, in California’s San Gabriel mountains, could be used.
The five-metre Hale Telescope at Palomar Observatory, used by the DSOC transceiver laser downlink, is an astronomical observatory, and could not be used for tracking and receiving data.
A spokesperson at the Jet Propulsion Laboratory (JPL) told The Register: “So the team used a smaller one-metre telescope at OCTL to track the DSOC transceiver’s downlink ‘beacon’ even though the skies were brightening.
“While tracking the DSOC transceiver on Psyche, the powerful uplink laser at OCTL was able to send a signal from Table Mountain to Psyche. When received at the transceiver, that proved the system’s pointing precision over 290 million miles – something that’s never been done before.”
Since a large quantity of data was not transferred, engineers could not measure the bandwidth. Instead, the demonstration was more of a stretch goal; the ideal conditions for DSOC are dark skies, rather than daytime. That the downlink laser (acting as a beacon) could still be locked on to and a command uplinked is, as the JPL spokesperson put it, “incredible.”
Meera Srinivasan, the project’s operations lead at JPL, said: “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.
“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 flight transceiver was powered down after the test and is due to be powered back up on November 4 to prove that the flight hardware can operate for at least a year.
Ken Andrews, project flight operations lead at JPL, said, “We’ll power on the flight laser transceiver and do a short checkout of its functionality.
“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.”
The Psyche spacecraft began its journey in October last year and is scheduled to reach its destination – a metal-rich asteroid called Psyche located between Mars and Jupiter – in October 2029. ®
PS: The suggestion that you could use this link to watch Netflix as-is on Mars, as the headline suggests, is just a gag. The site’s TCP-based connections wouldn’t be practically possible due to the time taken to send data to and from the Red Planet. You’d need another protocol that’s inter-planetary friendly.
