Would SpaceX be willing to add extra ISC laser link for communicating to ISS?

[Roy_H]

How many Starlink satellites would have to have an extra ISC laser to provide continuous communication with the International Space Station. This would have the advantage of high bandwidth short response time for the ISS. This system could also be used by SpaceX for communication to their Dragon and future Starship capsules.

[SpunkyEnigma]

Couldn't they just use RF like ground stations?  They are in a lower orbit, so as long as the satellites moving roughly the same speed as them have laser link they would be good.  Though being too close to the shell would probably put them into dead spots a fair bit.

However, I do like the idea of some dedicated hardware for ISS. I'm assuming Nasa would pay for it.  I could see 4 sats in a dedicated ISS servicing setup with interlink to the network, themselves and the ISS.  They would need to be at the same altitude and probably in lead and follow positions of at least 100km separation and a few +- minutes of inclination difference to space them out a bit.

The network engineer in me wants as much redundancy on the first hop to the network as possible.

The close distance would also help with visiting vehicle operations having lower lag than GeoSat comms.  Probably would just use RF for this situation.

[Jim]

there is no justification for it (not even for visiting vehicles) or for NASA to pay for it.  NASA has a system that provides 24 hr coverage.

[alugobi]

Are Dragon and the ISS ever without ground communication currently?

[SpunkyEnigma]

there is no justification for it (not even for visiting vehicles) or for NASA to pay for it.  NASA has a system that provides 24 hr coverage.

The justification I could see for a few million in investment would be much lower latency for remote control of experiments/robotics on station and higher bandwidth always available.  TDRSS maxes out at 300mbps/25mbps.  With the Starlink laser bus being measured in Gbps I could see a quality of life improvement for the astronauts as well.

Nasa is already spending R/D on laser comms, albeit at much greater distances.  They have put laser comms on the ISS in the past and are doing so again with the recent launch.  The distances still have lag issues that a LEO constellation would cut by at least 10x.

Laser terminals are ideal for spacecraft like the International Space Station because they require less size, weight, and power – a key benefit when designing new mission concepts. In 2022, LCRD’s first orbiting experimental user will be the Integrated LCRD Low Earth Orbit User Modem and Amplifier Terminal (ILLUMA-T) aboard the space station. ILLUMA-T will provide 1.2 Gbps data rates to communicate high-resolution images and videos of ongoing experiments down to Earth for investigation and discovery.

https://www.nasa.gov/feature/goddard/2021/nasa-laser-communications-innovations-a-timeline

Note that they will still need to launch on at least two more geosync sats for 24/7 coverage of the ISS, which I believe would be a higher cost than using Starlink.

We're talking about two laser devices, one fore and one aft, and 4 Starlink sats that could also serve their regular ground based customers in addition to having a laser pointing back at the ISS.  These sats are rumored to be in the $500k range of cost.  The biggest cost for NASA would be the need for integration engineering and for a spacewalk to place and wire in the devices.  I believe the sats would have no technical issue being launched in the Dragon trunk so no dedicated launch needed for ISS inclination.

[Tommyboy]

SpaceX already has plans to provide Starlink coverage to Dragon, Starship, or other spacecraft using their Ka parabolic antennas or laser links:
https://twitter.com/elonmusk/status/1439035515517509636
I'd assume the ISS can be part of "other spacecraft", if SpaceX gets a request and/or permission to equip the ISS with a compatible receiver.

[Jim]

Note that they will still need to launch on at least two more geosync sats for 24/7 coverage of the ISS, which I believe would be a higher cost than using Starlink.

And they will.  Because there are other users of TDRSS than ISS

[Jim]

The justification I could see for a few million in investment would be much lower latency for remote control of experiments/robotics on station

that isn't needed,

[Asteroza]

There are various motivations here that need to be separated.

Low lag moderate bandwidth for VR remote ISS ops, which needs something like Starlink. There are I think 2 other startups trying to deploy MEO intersatellite lasercomm-relay-as-a-service, but they haven't deployed production satellites yet. There's the fundamental issue that the lasercomm terminals are functionally 1:1 so servicing ISS means being unable to service other customers during use.

Latency insensitive bulk data at higher speeds sounds like something for the TDRS follow-on (which is increasingly sounding like that will be mixed commercial), which would locate replacement TDRS GEO sats with new ones that might include laser terminals (though the laser terminals sound like they will be outward focused for DSN support, and possibly only one terminal at that).

Now, there is the edge case that starlink sats near their highest latitude get bunched up, such that there is an oversupply of lasercomm terminals in that region of space. There might be enough slack to spin unneeded terminals towards ISS at that point in their orbits, but do they have line of sight to ISS at that moment (worst case ISS crossing the equator)?

[su27k]

Latency insensitive bulk data at higher speeds sounds like something for the TDRS follow-on (which is increasingly sounding like that will be mixed commercial)

This may be relevant: NASA to hand off spacecraft communications to industry

In addition, NASA is seeking industry assistance in replacing the Space Network, which provides communications for more than 40 missions including the International Space Station through government-owned Tracking and Data Relay Satellites (TDRS) and associated ground stations.

“While the TDRS System is a fine investment that the government has made, for the future we are looking at commercial alternatives,” said Ted Sobchak, NASA Space Network project manager.

NASA plans a multistep campaign to encourage development of commercial space-based relay networks before the current TDRS spacecraft reach the end of their lives.

[vsatman]

How many Starlink satellites would have to have an extra ISC laser to provide continuous communication with the International Space Station.

look at the photo of the ISS and think how many ISL  terminals you need to install on ISS body so that at least one is always visible and not obstructed by solar panels. And then we still need to think about how to fix them on the ISS body, pass the cables through it.
 After that, you can probably just forget about it ..