alt Hacker NewsWell, I might have been the first to put OCaml in space, specifically on low-Earth orbit aboard GHGSat-D in 2016. I designed the payload software as a collection of SystemD services talking over DBus, and it included a CCSDS-to-DBus bridge to talk to the platform (the thing that hosts the payload, controls and steers the satellite). The payload also did perform symmetric-key encryption of the resulting data, as per regulations.
I gave a talk about the payload software at the Paris OCaml users group.
The reason for selecting that archicture was that I didn't expect to write the whole payload software by myself, and I assumed that when some other developers join in they would, obviously, not want to use a weird language like OCaml, and so they could write their portion in C/C++/whatever and the system could still work. Of course that didn't happen.
I'd be surprised if the company still uses OCaml, as the standad tendency is to revert to "industry-standard" languages to get industry-standard problems. The whole processing and simulation toolchain was also written in OCaml.
Today there is little reason not to use Rust and it can cover both the processing side and the payload software. But people still insist on using C/C++. I'm OK with that as long as I can invoice them.
EDIT: Found my slides https://lambda-diode.com/static/data/GHGSat_OCaml.pdf
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(author of the post here)
Hey Berké! I remember your talk very well (I was in the room), super interesting and it really got me thinking about this area!
Since then, the more I look into it, the more I see a fit with our MirageOS unikernel work. On the ground, you can paper over security and specialisation by throwing more machines (or money) at the problem. In orbit you cannot, so both the compile-time and the runtime guarantees have to be right!
> Today there is little reason not to use Rust and it can cover both the processing side and the payload software. But people still insist on using C/C++. I'm OK with that as long as I can invoice them.
Any reason _not_ to continue using ocaml besides being less popular?
If popularity/mindshare wasn't an issue, I find the development cycle with ocaml to be nicer in several ways compared to rust on a platform where stuff like python is already allowed (I wouldn't call a full-blown linux system, even with limited memory, "embedded").
Besides certification issues, it is a matter of culture.
That is why I say I see Rust main domains, environments where any form of automated resource management is not possible due to technical reasons, or (your point) it is a waste of time trying to convince people out of their beliefs.
Thanks for the presentation.
Do you have a link to your talk? I'm also curious if you did any GHG measurements, or it was part of the control stack. We wrote the XenServer stack in OCaml back in 2004, and that made it into orbit in 2017 (I think it did, anyway: https://www.theregister.com/offbeat/2017/05/12/space-upstart...)
Oh, hey Berké,
The GHGSat constellation's payload software is still mostly OCaml, although a limited amount of newer from scratch components are indeed in Rust. It's been working well and on 16 satellites now - but as you said the main challenge has been training developers to Ocaml and I doubt they would write new code in it now.