NASA's Psyche Spacecraft, Optical Comms Demo En Route to Asteroid
nasa.gov
nasa.gov
More information about the receivers and transceivers can be found here: https://www.nasa.gov/wp-content/uploads/2023/07/dsoc-fact-sh...
The mission website is here: https://www.nasa.gov/mission/deep-space-optical-communicatio...
Not only do they have to point very accurately, both terminals will have to simultaneously point at where the opposite terminal was (for receiving) and will be (for transmitting) because of the light time delay. The distances will be so vast and so little light will arrive at Palomar that they will have to employ a superconducting (cooled to a fraction of a Kelvin) nanowire single photon detector. The modulation format is orders of magnitude more efficient (from an energy per bit perspective) than Kuiper or Starlink even though the data rate is (necessarily) lower.
Artemis II is scheduled to use the same modulation format and could use the same uplink and downlink terminals. JPL is building a "hybrid" Ka/X-band/optical terminal in the desert in Goldstone that may be able to let Palomar spend more time on astronomy.
It's one thing building (a pair of) working optical communications terminals. Designing it so you can build tens of thousands of them is a totally different game.
In particular:
> Optical to Orion (O2O) is a plan to do a lasercomm demo on one of the future Orion moon missions.
> When the Psyche spacecraft launches and heads to the asteroid belt (was supposed to launch in august) it will do the farthest (by far) lasercomm demo. I work in the group that made the SNSPD ground receiver. As my boss says, with a distance 1000x farther than previous space laser comm demos, closing the link is 1 million times harder...
> Fun fact: when the Phyche comm laser is pointed at earth, the size of the spot will be roughly as large as California. Even with the largest optical telescopes, the loss in this link will be insane. That's why you need single photon detectors.
> As you get to farther and father distances, one thing you can do is shift from on/off keying to large-M Pulse Position Modulation. This way you can save up the power on your satellite to send fewer but higher power laser pulses, each of which carries more bits of data. I believe the DSOC mission will go up to M=256. Meaning each pulse of photons received on earth will carry 8 bits of information based on when it arrives within an alphabet of 256 time bins.
https://www.youtube.com/watch?v=npIDMxrzm_o&t=3051s
Boosters landing:
Amazing how long the sound takes to reach you. ~35 seconds. Rocket is well off the pad visually before you hear the engines throttle up to full.
Makes for a surprise when you see the boosters landing... then later get the sonic boom cracks.
The reason is that 16 Psyche is hypothesized to be a very, very rich ball of metal. A million times the material wealth we have here on Earth, in fact. More gold, silver, platinum, iron, zinc, etc. than we can even fathom exists, accessible on our surface here on Earth.
If we arrive and find it full of gold and other valuable metals, I'd imagine the following 10 years afterwards, humans are going to be on a race to get there, set up shop, and start 3D-printing Starships.
Its far-fetched and fantastic, but I could imagine a scenario where this race really takes off. 10 years from now, we might very well have the technology to exploit this gigantic ball of materials in super interesting ways. (Assuming we don't nuke ourselves into oblivion, obviously. Lets just put that aside.)
Imagine, we start moving heavy-metal industries to space. 3D Printers set up shop on the 16 Psyche surface, and starts churning out Starships (which by then should be perfected for human-rated travel around our star system, hopefully).
One can dream. I sure hope I'm alive to see the first pictures of arrival.
A single SpaceX Starship claims to have a reusable payload of 150 tons. Current annual mining operations extract 21 million tons of copper, 3,000 tons of gold, and 300 tons of platinum. So let's focus on platinum. You'd need two starships per year to match current platinum production. But it's a 12-year round trip, so you'd need 24 starships in continuous operation just to haul the metals (let's ignore where they're getting their fuel from for the return trip). And that's before you get to the actual costs of the mining operation itself; bootstrapping fully autonomous robotic space mining on a rock 200 million miles away is going to take more money that anyone has lying around. And the final result of this is that you've spent a trillion dollars just to crash the market for platinum.
It might only be useful for in-orbit manufacturing, which is also a near complete unknown at this point. Pretty exciting for anybody contemplating building massive orbital stations.
Why call a metal world 'psyche'? (Where psyche is the Greek word for heart.)
I don't know why I find it interesting but Psyche asteroid is 31 minutes and 33 light seconds from Earth. Assuming my math is correct, at 400 Mbps, there would be roughly 94 GB of data "in flight" through space between the satellite and the Earth.
However, most of that data will be redundant. "Hi! I'm still here! I'm currently at blahblahblah position, and my status is nominal" over and over and over
Seems like earth satellites might have huge pipes, but the data arrives too quickly to build up.
Maybe 94GB would do it.
And while it was very much not a high-capacity technique, you might find the mercury delay-line memory used by early computers interesting if you haven't heard of it before.
Vaguely reminds me of the spool with 38 miles of fiber used to thwart high frequency traders. https://www.iexexchange.io/technology
After reading the story it makes me think of a quote from a Bujold book, where one fantasy character talks about how it was a godly miracle that 300 heathen invaders were completely eradicated after their grave sin of murdering one local saint, and another character retorts.
Adjusting that response to fit:
"I would be considerably more impressed with your global nanotech overlord AI," said Ista through her teeth, "if He could have arranged a few satellites worth of simple detection in advance, rather than several billion lives' worth of gaudy evacuation afterward."
Aug 2029 is 5 years and 9 months from now. So how does it go? Do they just hand it over to the interns at JPL until then?