The optical communication experiment is a very exciting piggyback, but it's disappointing that the press release is 95% background on the Psyche missing and only a tiny blurb about that experiment. Where are the receivers? How far away do they expect to be able to pick up communication? How do they get the angle of the laser to the incredible accuracy they need?
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.
Do you have specs on the starlink or kuiper laser terminals? SpaceX has been hush hush about the former and I didn’t even think kuiper had anything for laser comms yet.
This system probably isn't very comparable to the Starlink space lasers. Because of scale, Starlink is very heavily optimized for cost, while a bespoke deep space terminal probably doesn't even have cost as a factor.
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.
> 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.
They are using ground based telescope observatories. "...To receive the downlinked high-rate data sent from the probe, NASA is relying on the 200-inch Hale Telescope at Caltech’s Palomar Observatory in San Diego County, which sits atop a mountain south of JPL."
