Tuesday, February 20, 2024

NASA’s new hybrid antenna tracks deep space laser

NASA has achieved a major milestone in space communication by using a new antenna that can receive radio and laser signals from its Psyche spacecraft.

The spacecraft is on a mission to explore a unique asteroid, and the new antenna is part of NASA’s Deep Space Network (DSN). The giant dish antennas of NASA’s DSN, which communicate with spacecraft via radio waves, can be retrofitted for optical or laser communications. This new antenna can also receive near-infrared laser signals, which can carry more data and open up new opportunities for space exploration.

Optical communication can enable new space exploration capabilities while supporting the Deep Space Network (DSN) as demand for the network grows. The new 34-meter (112-foot) radio-frequency-optical-hybrid antenna, named Deep Space Station 13, has been able to track the downlink laser from NASA’s Deep Space Optical Communications (DSOC) technology demonstration since November 2023. The DSOC tech demo’s flight laser transceiver is traveling with NASA’s Psyche spacecraft, which was launched on October 13, 2023.

The hybrid antenna used for downlinking data isn’t a part of the DSOC experiment, and it is located at the DSN’s Goldstone Deep Space Communications Complex near Barstow, California. The DSN, DSOC, and Psyche are managed by NASA’s Jet Propulsion Laboratory in Southern California.

A close-up of the optical terminal on Deep Space Station 13 shows seven hexagonal mirrors that collect signals from DSOC’s downlink laser.
A close-up of the optical terminal on Deep Space Station 13 shows seven hexagonal mirrors that collect signals from DSOC’s downlink laser. Credit: NASA/JPL-Caltech

The hybrid antenna successfully downlinked data from 20 million miles away at a speed of 15.63 megabits per second, which is about 40 times faster than radio frequency communications at that distance. Additionally, the antenna downlinked a team photograph that was uploaded to DSOC before Psyche’s launch on January 1, 2024.

“Our hybrid antenna has been able to successfully and reliably lock onto and track the DSOC downlink since shortly after the tech demo launched,” said Amy Smith, DSN deputy manager at JPL. “It also received Psyche’s radio frequency signal, so we have demonstrated synchronous radio and optical frequency deep space communications for the first time.”

To detect the laser‘s photons (quantum particles of light), the hybrid antenna has seven ultra-precise segmented mirrors attached to its curved surface, resembling those of NASA’s James Webb Space Telescope. These mirrors are used to reflect and redirect the photons into a high-exposure camera attached to the antenna’s sub-reflector, which is suspended above the dish’s center.

The laser signal collected by the camera then goes through an optical fiber that feeds into a semiconducting nanowire single photon detector that is cryogenically cooled. This detector is identical to the one used at Caltech’s Palomar Observatory in San Diego County, California, which acts as the DSOC’s downlink ground station. The detector was designed and built by JPL’s Microdevices Laboratory.

This artist's concept shows what Deep Space Station-23, a new antenna dish at the Deep Space Network's complex in Goldstone, California, will look like when complete in several years.
This artist’s concept shows what Deep Space Station-23, a new antenna dish at the Deep Space Network’s complex in Goldstone, California, will look like when complete in several years. Credit: NASA/JPL-Caltech

“It’s a high-tolerance optical system built on a 34-meter flexible structure,” said Barzia Tehrani, communications ground systems deputy manager and delivery manager for the hybrid antenna at JPL. “We use a system of mirrors, precise sensors, and cameras to actively align and direct laser from deep space into a fiber reaching the detector.”

Tehrani hopes that the hybrid antenna will be sensitive enough to detect the laser signal sent from Mars at its farthest point from Earth, which is 2 ½ times the distance from the Sun to Earth.

In June, Psyche will be at that distance on its way to investigate the metal-rich asteroid Psyche, located in the main asteroid belt between Mars and Jupiter. The antenna features a seven-segment reflector, which is a proof of concept for a more powerful version with 64 segments. This scaled-up version will have the equivalent of a 26-foot (8-meter) aperture telescope and could be used in the future.

DSOC is paving the way for higher-data-rate communications that can transmit complex scientific information, video, and high-definition imagery. This will be incredibly useful in supporting humanity’s next giant leap – sending humans to Mars. The tech demo recently streamed the first ultra-high-definition video from deep space at record-setting bitrates.

One possible solution to the current lack of a dedicated optical ground infrastructure could be retrofitting radio frequency antennas with optical terminals and constructing purpose-built hybrid antennas. The DSN currently has 14 dishes across facilities in California, Madrid, and Canberra, Australia. Hybrid antennas could rely on optical communications to receive high volumes of data and use radio frequencies for less bandwidth-intensive data such as telemetry.

“For decades, we have been adding new radio frequencies to the DSN’s giant antennas located around the globe, so the most feasible next step is to include optical frequencies,” said Tehrani in the press release. “We can have one asset doing two things at the same time: converting our communication roads into highways and saving time, money, and resources.”