We had an exciting year last year with the launch and successful deployment of Binar-1, our first CubeSat. We’ve got even more to come this year – but we’ve got a bit of a story to tell about Binar-1 first.
So for our first post, we’re catching up with Daniel Cristian-Busan, our radio operator and engineer, to hear how the Binar-1 story went down behind the scenes.
Getting off the ground
Binar-1 had plenty of help on its ride to space. Our launch partners SpaceBD took it to Japan. NASA and SpaceX took it to orbit, on board the CRS-23 Dragon. Astronauts on the International Space Station carefully loaded it into its deployment mechanism.
But once it was deployed from the station, Binar-1 would be on its own. It’d be 400km up, moving at 27,000 km/h.
We don’t have a strong enough telescope to look at it and figure out what’s going on, or a long enough screwdriver to fix it.
All we’d have to work with was what the spacecraft could tell us, and what we could tell it to do back – and both of those things turned out to be much harder than we thought.
This is the story of how we found Binar-1.
The First Night
Binar’s orbit brings it over any given part of the Earth every few hours. For our first night, we had ground stations listening in from Perth (At Curtin in Bentley, and at Fugro’s site in Gnangarra) and at ESA in Darmstadt, Germany. Between the two, our first chance to hear from the spacecraft was that same night at midnight, and then again at 5am.
“That first night we thought, let’s just listen to see what’s going on,” says Dan.
To understand what we were listening for, it helps to understand a little bit about how Binar boots up. When the satellite is deployed, it waits 30 minutes before doing anything. Once those 30 minutes are up, it knows it’s reached a safe distance from the Space Station. It’ll check its battery levels, and if it’s got enough juice, it deploys its antennas and starts sending down a signal.
That signal is called a ‘beacon’ – it has a little bit of information about how the satellite is faring, and some instructions about how to contact us if it’s picked up by someone else.
“We quickly started seeing the signals from Maya-3 and Maya-4 – the two satellites that deployed alongside us,” says Dan.
“But we didn’t see ours.”
Have you tried turning it off and on again?
Binar-1 has 4 antennas, but to fit into the deployment rack on the ISS, they have to be stowed at launch. The antennas are spring loaded, and they’re released by using electrical heating elements to melt through the ties holding them in place.
This is a pretty power intensive process – imagine running a toaster off a phone battery. If the batteries were too low to release the antennas, Binar was programmed to wait 24 hours for the batteries to charge, and try again.
“So we listened for the first night or two and then we started to think okay, it’s still not speaking to us.”
“What can we do? Let’s try to tell it to reboot.”
At this point, we thought the most likely scenario is that the antennas hadn’t deployed. Rebooting would cause the spacecraft to think it had just been deployed from the space station. It’d start its program from scratch, and attempt to deploy the antennas again.
We sent reboot commands from Perth and Darmstadt, each time Binar-1 passed overhead – but still no signal.
From there we moved into full troubleshooting mode.
If anything went wrong during deployment – for example, if one or more of the antennas indeed didn’t deploy – the spacecraft would put itself into “safe mode”. In safe mode, Binar-1 doesn’t try to do anything that could damage the spacecraft (or anything else in orbit), instead waiting for instructions from the ground.
“Fergus and Stuart sat down and ran through the boot process, read through the code and did a big flowchart,” says Dan
“They caught a logic issue in our code, which meant that if for any reason at all, it doesn’t matter what it is, we end up in safe mode after initially booting, we actually wouldn’t be transmitting anything.”
One of the computer’s first jobs is to switch the radio into the mode used to relay data to and from the ground, called “transparent” or “pipe” mode. The error meant the radio had never changed mode. Even if Binar’s computer was trying to send signals, the radio chip wasn’t passing them on.
While we couldn’t communicate with Binar’s computer, Binar’s radio was pretty smart on its own. With the right commands, we could enable it from the ground – but it would take a little bit of time.
“We were expecting to be able to fully communicate with the bus and not have to command the communications module,” says Dan. “We actually had to do some quick programming on our ground station software to get it to do this because it’s not part of the standard operating procedures.