You want your Moon landings in HDTV? So does NASA—here's how it's happening. - Ars Technica

Overview

You want your Moon landings in HDTV? So does NASA—here’s how it’s happening.

“You just push this button, and in three hours, you’re counting photons.”

Details

During most of the Artemis II mission, the crew of four astronauts beamed back low-definition video, both from inside the spacecraft and from exterior views of the Moon. It was exhilarating stuff, but in a world in which we’re all watching HDTVs, it also felt a little flat.

This is because Orion largely communicated with Earth via radio waves, picked up by large dishes sprinkled around the world. This is pretty much the same way the Apollo spacecraft talked to Earth more than half a century ago.

However, unlike Apollo, the astronauts on Orion would periodically send batches of much higher-resolution data, including the stunning photographs of the far side of the Moon and the Solar eclipse observed from there. This was made possible by optical laser communications, and not just those built by NASA. The mission included a commercial component that could pave the way for vastly more data returning to Earth from space than ever before.

Apollo returned data to Earth at about 50KB per second using radio frequencies. Similarly, Orion used S-band for a slightly higher communication rate most of the time, at 3MB to 5MB per second. But when the spacecraft turned on its optical communications terminal and connected to ground stations, the data rate increased to 260 Mbps. At those speeds, the crew could have transmitted a full high-definition movie to Earth in seconds.

But that did not happen for a couple of reasons. The first is that the optical communications system was experimental, and the second is that NASA had only three ground stations capable of receiving and processing these laser signals back on Earth: two in the United States and one in Australia.

NASA has previously experimented with laser communications from the Moon with the Lunar Atmosphere Dust Environment Explorer mission a little more than a decade ago, and later a demonstration from the International Space Station as well as the Psyche spacecraft from deep space.

Yet these were tentative efforts. Bolting an optical communications system onto Orion represented an important final test for the technology, which is now likely to become a bedrock for future Artemis missions to the Moon. Its successful use should allow NASA’s Artemis IV landing on the lunar surface and future missions to be broadcast live in high definition and possibly even 4K.

There is one major drawback with optical laser communications. The photons in the laser, at 1550 nm, are easily scattered by clouds. A single ground station must have clear skies to receive a steady signal,

That’s a major reason why, although Space X’s Starlink constellation has implemented space-to-space laser links, space-to-ground laser links have remained experimental to date.

But laser communications are clearly the future as the amount of data generated and stored in space grows exponentially. Not only is the bandwidth about 100 times greater, but the transmitters required are also smaller and need less power. For example, on Orion, the S-band transmitter required 5 to 20 watts of power, compared to the laser communications transmitter, which used just a single watt.

How do you address the cloudy skies problem? For always-on laser communications with future Artemis missions, to protect against clouded-in locations, it’s estimated that there would need to be about 40 ground stations around the world. Fortunately, there was an experiment-within-the-experiment on Artemis II that could help solve this issue.

NASA’s primary ground stations for optical communications on Artemis II were telescopes at the White Sands Complex in Las Cruces, New Mexico, and the Table Mountain Facility in California. However, the space agency also decided to test whether it would be feasible to deploy a lower-cost optical terminal on the ground to receive lasers from space.

Engineers from NASA field centers in Ohio and Maryland purchased an off-the-shelf 70 cm telescope from Observable Space and a backend to process the lasers from Quantum Opus. Within months, the telescope and detector were deployed at Mount Stromlo in southeastern Australia, near Canberra.

During Artemis II, the off-the-shelf optical terminal reached the system-designed maximum rate of 260MB per second, downloading much of the data NASA received during the mission.

“Advancing US leadership in space- and ground-based optics is core to our mission, and turn-key laser communication ground stations are a critical component of that future,” Dan Roelker, co-founder and CEO of Observable Space, said in a statement.

The technology for receiving and processing laser signals from the Moon, Mars, or beyond is not simple. The “Opus One” detection system, for example, uses superconducting nanowire single-photon detectors. That’s why reducing the cost of building and deploying these systems is critical for widespread adoption of space-to-ground laser communications.

Quantum Opus was co-founded by physicist Josh Cassada, who became a NASA astronaut in 2013 and then retired more than a decade later to rejoin Quantum Opus. He led the fabrication of the company’s photon-detection products.

In an interview, Cassada said the technology is important not just for getting massive amounts of data down from space, but also for applications such as quantum computing. “If you want to detect photons at the single photon level, and you don’t know anything about cryogenics, that’s fine,” he said. “You just push this button, and in three hours, you’re counting photons.”

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Key Takeaways

You want your Moon landings in HDTV
“You just push this button, and in three hours, you’re counting photons
During most of the Artemis II mission, the crew of four astronauts beamed back low-definition video, both from inside the spacecraft and from exterior views of the Moon
This is because Orion largely communicated with Earth via radio waves, picked up by large dishes sprinkled around the world
However, unlike Apollo, the astronauts on Orion would periodically send batches of much higher-resolution data, including the stunning photographs of the far side of the Moon and the Solar eclipse observed from there