The end-of-life disposal of the italian geostationary satellites

To date, four Italian satellites have been launched in geostationary orbit: SIRIO, Italsat 1, Italsat 2, and SICRAL. Of these, only the latter is still operational: SIRIO was abandoned close to the geopotential equilibrium point at 75? E in 1985; Italsat 1 was re-orbited above the geosynchronous altitude at the beginning of 2001; and Italsat 2 was moved, due to a malfunction, in July 2002, below the geosynchronous altitude. This paper reviews how the strategy for the end-of-life disposal has evolved over the last twenty years, due to the growing concern regarding the possible overcrowding of the geostationary ring. The Italian experience is revisited, in order to show the lessons learned in the context of the new international awareness of the space debris problem at the geosynchronous altitude, which has led to the endorsement of a specific disposal strategy by the Inter-Agency Space Debris Coordination Committee (IADC). Long-term orbital propagation is used to assess the impact and relative effectiveness of different disposal scenarios, employing the Italian geostationary satellites as test cases.