Traffic build-up in orbit

The Swedish Prisma satellite was blasted into orbit by a Russian-Ukrainian Dnepr launch vehicle on 15 June 2010. The launch was a success and the satellite - composed of two elements which are subsequently to be separated in order to practice flying in formation - was put to sleep for several weeks. The teams were therefore able to go away on holiday for a well earned rest.

However, the traffic on the roads at the beginning of the summer is just as heavy in orbit as elsewhere. On Monday 5 July, the Swedish Space Corporation, the Swedish agency responsible for managing the Prisma programme, received an urgent message from the US Joint Space Operations Center in Vandenberg which analyses the orbits of more than 19,000 satellites and pieces of orbital debris followed by NORAD: on Wednesday 7 July at 00:59 (Tuesday 6 July at 22:59 GMT), one of the pieces of debris from the 2009 collision between an Iridium satellite and one abandoned by the Russians was to be crossing Prisma’s path at a distance of 144 m. For an ordinary mortal, this seems a lot, but for a satellite operator it is extremely close. Given the margins of error as regards measurements and estimations in the permanent degradation of the orbits, a crossing at less than 1 km meant that the risk of collision could not be excluded.




In just a few hours, the essential team members had to rush back off holiday in order to be ready on Tuesday evening at 21:00 to perform an avoidance manoeuvre: 10 seconds of thrust at the right time and in the right direction so that Prisma could move safely past the debris at a distance of 2 km.

The Prisma mission website