At the Raspberry Pi birthday celebration last week one of the most talked about topics was the Astro Pi project. But with the first results from the two Raspberry Pi boards now on board the International Space Station starting to arrive on the ground, and a new competition for British school children to have their code run in space, it’s understandable.
“We have a Raspberry Pi in space. It was one part engineering, and nine parts paperwork. When the paperwork weighs more than the payload you’re ready for flight.” — Eben Upton
Launched onboard the Orbital ATK Orb-4 resupply mission to the International Space Station in December last year, the two Raspberry Pi boards left the ground from the same pad at Cape Canaveral that saw the launch of both Voyager and Curiosity.
Encased inside specially built aluminium flight cases, the Raspberry Pi boards are being flown to the ISS in support of British ESA Astronaut Tim Peake’s mission to the space station and have been running code written by British school children ever since.
The two Raspberry Pi boards are equipped with a camera as well as a Sense HAT that can measure the environment inside the ISS as well as the Earth’s magnetic field. Each Pi has a different kind of camera; one is a standard visible light camera, the other, one that images in the infrared bands.
The experiments, and in some cases the code itself, running on the boards was were designed by students from British schools. First powered up in February the two AstroPi boards have been running the experiments from the seven winning entries into the AstroPi competition.
Building the AstroPi
At the Raspberry Pi birthday celebrations last week, Dave Honess talked about the long drawn out process of getting the two boards ready for space. Any hardware intended to fly into space must receive a Flight Safety Certificate, and getting one isn’t easy.
You can’t just take a bare PCB into space, so a specially designed aluminium flight case was needed, the case not only had to be designed for thermal dissipation, but also to get rid of sharp edges.
The final test before flight is a snag test.
“…they have special gloves and they pick it up and feel it all over, if they snag, you fail.” — Dave Honess
The STL files for the AstroPi flight case are available, so if you want you can 3D print a copy of case and build a replica AstroPi unit. Being able to experience how the astronauts would interact with their experiments was something that was no doubt invaluable to the students competing to have their code flow in space.
However, the case isn’t the only issue. The boards themselves have to be tested for electromagnetic emissions at the micro-volt level using sensitive antennas in specially built chambers, and tested for off-gassing to ensure the payload does not give off any fumes that might be harmful to the crew.
Now in the EMC chamber! pic.twitter.com/hjeMfozUSn
— Astro Pi (@astro_pi) May 28, 2015
They boards, inside the flight case, also needed to be vibration tested to make sure they would survive launch.
Flight hardware about to go through Soyuz launch conditions vibration testing at @AirbusDS @JohnChinner @dave_spice pic.twitter.com/zphG5kpSuR
— Astro Pi (@astro_pi) May 28, 2015
Finally, after all the testing, the AstroPi units were taken to the ESA’s European Astronaut Centre in Cologne, Germany, for a full end-to-end reproduction of everything that Tim Peake would do on orbit.
The Astro Pi looks very much at home in the Columbus mock up! Testing all going well so far. pic.twitter.com/M3emHTC8JO
— Astro Pi (@astro_pi) August 10, 2015
There, the step-by-step procedures that need to be followed in space were all worked through and refined in a full-scale mock up of the Columbus laboratory module.
At the Big Birthday Weekend teacher Richard Hayler and pupils from Cranmere Primary School presented the initial results from their experiment. It used the environmental sensors of the Astro Pi, particularly the humidity sensor, to try and detect the presence of a crew member. If a fluctuation is detected, a picture was taken using the camera to test to see whether it was caused by an astronaut.
So far the pupils’ hypothesis has proved correct, with large spikes in humidity correlating well with pictures of astronauts moving around the space station.
Mini-computer @astro_pi looking out the window. 30 days left to get your code in space! https://t.co/Vdnyf7nAD8 pic.twitter.com/k3uhkdKAIK
— Tim Peake (@astro_timpeake) March 2, 2016
Results from the experiment from Westminster School are also starting to appear. This made use of the Astro Pi infrared camera pointing out of a window and taking pictures of the ground which would be later analysed using false colour image processing to produce a Normalised Difference Vegetation Index (NDVI) and a measure of plant health.
1st pictures from the ISS for Oliver Turnbull's EnviroPi taken by @astro_timpeake @astro_pi https://t.co/0t7mN3bP7U pic.twitter.com/bc3yBVUZhJ
— Westminster CompSci (@WSchoolCompSci) March 10, 2016
Results from other competition winners, such as the team from Magdalen College School who repurposed the AstroPi camera as a Cosmic Ray detector, should hopefully start appearing soon.
Your Code in Space?
You can follow Izzy and Ed, the two AstroPi boards currently onboard the International Space Station on Twitter, and there’s still time to get your code into space. If you’re aged 18 or under and in the UK, submit your entry via the Astro Pi website by 31 March!