Astro Pi: Launch is tonight!


Tonight, two specially augmented Raspberry Pi computers, called Astro Pis, will launch into SPAAAAACE! The Astro Pis will be running experimental Python programs written by school-age students, where the results will be downloaded back to Earth and made available online for all to see.

  • When: 22:55:41 GMT (first launch window opens)
  • Where: Cape Canaveral, Florida, USA
  • Coverage: NASA TV live stream (below, and keep an eye out – Astro Pi may get a mention in the launch commentary)

NASA Public

NASA TV airs a variety of regularly scheduled, pre-recorded educational and public relations programming 24 hours a day on its various channels.

If you’ve been following the Astro Pi project, you’ll know that we were bumped from Tim Peake’s launch vehicle due to a cargo overbooking back in October.


The OA-4 Cygnus Spacecraft, image credit: Orbital ATK

We’re now going to launch on Orbital Sciences’ Cygnus cargo freighter (an unmanned spacecraft, above) on its fourth supply mission to the ISS. Orbital Sciences have contracted ULA to launch it into space on an Atlas V rocket (below).


The Atlas V rocket, image credit: United Launch Alliance

When you need to rendezvous with an object in orbit, the timing of the launch is often critical to ensure that you get into the right orbital trajectory. This is often achieved with an instantaneous launch window where the rocket has to lift off at a precisely calculated time, otherwise the two objects will never meet in space.

Obviously, this approach can significantly limit the probability of an on-time launch. For instance, you may need to wait for a rain shower to pass by, a technical problem to be resolved or a boat in restricted waters to be chased away.

However, this is not the case for our launch! The Atlas V has so much performance capability that it provides a 30-minute launch window each day, and it’s all thanks to energy. The Atlas V has so much available energy that it can accommodate a very large off-nominal time of launch: 15 minutes early or 15 minutes late. The extra power is then used by clever steering algorithms to compensate for the rotation of the Earth, relative to the orbital target.

Below is the final configuration of the rocket. It will fly in the 401 vehicle configuration with a four-metre fairing, no solid rocket boosters, and a single-engine Centaur upper stage. The Astro Pis are sitting inside a small cargo transfer bag within the Cygnus spacecraft at the top.


OA-4 Launch Configuration, image credit: United Launch Alliance

And here is the ascent profile, with the main events numbered.


OA-4 Ascent Profile, image credit: United Launch Alliance

These are the event descriptions, with their times relative to lift-off.


OA-4 Main Events, image credit: United Launch Alliance

And finally, this is the ground trace; note that it will pass over the UK around 23 minutes into the mission. However, it will be in the Earth’s shadow and so almost impossible to spot with the naked eye.


OA-4 Ground Trace, image credit: United Launch Alliance

If everything goes according to plan, the Cygnus spacecraft will arrive at the ISS on the 6th of December at 9:00 GMT. The docking is a fascinating process and really worth watching if you’re interested; NASA TV will show it. It involves one of the crew operating the Canadarm2 to grab onto the incoming spacecraft before pulling it in.


Cygnus being moved onto the pad yesterday – the two Raspberry Pis are in the cone at the top.

Should the launch be delayed for any reason, here is a list of subsequent launch windows that occur over the next few days:

  • December 4
    Launch: 22:33 GMT
    ISS arrival: Dec 7 or 8
  • December 5
    Launch: 22:10 GMT
    ISS arrival: Dec 9
  • December 6
    Launch: 21:44 GMT
    ISS arrival: Dec 19

If it’s delayed to the 6th, it will have to loiter in orbit for a few weeks before it can dock with the ISS. This is because of other visiting vehicle traffic, such as the Soyuz 45S launching on December 15th, carrying Tim Peake and his crew mates.

I will be attending the launch at Kennedy Space Center, along with Matt Richardson and Jonathan Bell (AKA jdb on the forums). We will be live-tweeting from our personal Twitter accounts (@Dave_Spice and @MattRichardson), from the Raspberry Pi account and also from the main Astro Pi account.

Please follow the official Twitter account below for the very latest updates on the launch.

Astro Pi (@astro_pi) | Twitter

The latest Tweets from Astro Pi (@astro_pi). British @esa astronaut @astro_timpeake is taking two augmented @Raspberry_Pi computers to the @Space_Station as part of mission #Principia Get your code on them

This has been a long road for us and our partners, so please keep fingers and toes crossed!