The space around the world is covered by more than 300000 particle of space debris, whose diameter is larger than 1 cm. This population is similar to the asteroidal one, because its long term evolution has been affected by mutual collisions in high speed and the orbits are highly chaotic. The area covered by space debris can be divided in three main areas LEO – Low Earth Orbit under 2000 km; Medium Earth Orbit – MEO, which is between 2000 and 36000 km; and the GEO one (Geosynchronous Earth Orbit – GEO) which is at about 36000 Km.
As highlighted in the dramatic impact of two satellites Iridium 33 and Cosmos 2251 occurred on 10th February 2009, the impact probability is a real risk for all space activities. After the impact of Iridium, all the space specialist were aware it was necessary to introduce some prevention activities such as the validation of impact mitigation, the coordination of the space traffic and the efficient mitigation measurements.
All the alien space probe present in the orbit has been classified by “United States Strategic Command” (USSTRATCOM) in the TLE (Two–Line Element – TLE) catalogue. There are listed at about 15000 objects, representing their current orbital parameter. The size limit of the objects present in the catalogue is between 5 till 10 cm under some miles km in altitude and between 0,5 and 1 Mt for higher orbits (till GEOs). At about 6% of the objects in the catalogue of TLE are operative satellites. Almost 24% of the objects in the catalogue is made up by not operative satellites, while 17% is made up by missiles in a superior phase and 13 % is made up by mission’s debris. At about 40% are fragments. “United States Space Surveillance Network” provides frequently a huge number of radar and optics observations. In 2008 Europe began its SSA Program, segment SST, with the aim to increase the know-how of the circumterrestrial environment. In this context is extremely important the availability of efficient methods and algorithms for an accurate orbit determination.
The team and partners of SpaceDyS have a long experience and a strong back-ground in the field of space debris. They took part at the beginning of the 90’s to the development of the first European models for a long term evolution’s study of the space debris population, by shedding light on the risk of the impact’s proliferation and on the need to undertake mitigation measurements. In 1999 for example, ten years before the effective event, they highlighted in an article published on Nature magazine the risk’s effects due to the fragmentation of the Iridium Constellation.
From that moment, the team continued to develop theories and instruments in this field, by achieving important results in the orbit determination and the correlation of space objects. The interest of the team on this research field is shown by many publications in international journals and conferences.
SpaceDyS achieved a project dedicated to the orbit determination and the re-entry prediction of the satellite Goce, according to radar measurements and GPS. In particular the team focused on the characterisation of significant dynamics and observative uncertainties, related the position prediction and re-entry location.