OPERATIONAL IMPACTS AND ENVIRONMENTAL-EFFECTS ON LOW-THRUST TRANSFER-MISSIONS OF TELECOMMUNICATION SATELLITES

The paper addresses the evaluation of the performance of electric arcj et systems used onboard of modern telecommunication satellites, for bo th the transfer mission to the operational orbit and the north-south s tation keeping. A major objective of the paper is to identify beside t he optimal thrusting strategy in particular the mission requirements a nd adjustments of the spacecraft's propulsion subsystem due to the imp lementation of the electric thrusters. The paper describes in detail t he radiation effects on solar arrays and electronic devices which are imposed on the spacecraft during its passage through the Van-Alien bel ts. Dose calculations are performed to evaluate lifetime limitation an d reliability reduction of the electronic components as well as perfor mance degradation of solar arrays. Following the rules of radiation ha rdening, the effects of thicker shielding of electronic component boxe s as well as solar array's cover glass adding with adverse effects on dry mass are demonstrated.It can be shown that in spite of all additio nal mass contributions the hydrazine arcjets combined with chemical mo no-propellant thrusters seem to be a favourable, attractive option. Co mpared to the conventional bi-propellant or dual-mode concepts the use of arcjets yields to a fuel reduction of 21% and a cost reduction of about 11%, respectively, at transfer times between 100 and 120 days fr om GTO to GEO.