Table 10.3.3 Orbital Selection Trade-Off Analysis Launcher For this mission, the largest launchers will be considered (HII, Ariane V, Titan IV, Energia) with the basic assumption that no other launcher will be available within the next ten years. The preferred one is Energia because of its volume and mass into orbit capabilities. Power Generation and Beaming Analysis Power Generation The baseline solar generation system for this mission is the use of classical flight proven solar panels covered with silicon cells. An alternative using solar concentrators focusing sunlight on gyroreactors is proposed as an option (see space segment section). Due to the fairing constraints (Energia), the solar array size is limited to 1000 m^. This gives a power output in the range of 100 kW after 5 years in orbit. Since the useful transmitting part of the orbit is in the order of only 5% only, batteries can be used on board to store energy during the non visibility periods. This typically increases the power up to 200 kW at the power subsystem output. Power Conversion and Transmission Here again, for fairing and cost constraints, the size of the transmitting antenna is limited (practically lower than 100 m^). In addition, in order not to have the whole power concentrated on one point, an active phased array antenna is proposed as a baseline. Taking into account the conversion efficiency, the power which actually leaves the satellite is in the order of 150 kW. Another point concerns the selected frequency, which has to be compatible with the state of the art extrapolated to the next ten years. Two frequencies are possible here: 2.45 GHz which is well known but leads to a very spread out beam, and 35 GHz for which the technology is only now under development but with a more concentrated beam. Both take advantage of atmospheric windows, with less rain losses for 2.45 GHz. The proposed baseline however is 35 GHz for ground power flux density reasons. This is reflected in the Table 10.3.4: Item SSO orbit (6:00- 18:00) near equatorial orbit Solar array efficiency + (Angle between SA and sun constant at first order) (Orbit plane drift) Eclipses + (Very few, possibly none around 1400 km) Every orbit Access + (Potentially any) (only equatorial belt) Rectenna visibility (A few minutes per orbit) (A few minutes per orbit) Mass into orbit - + Beam pointing (pointing needed because rectenna seen with various angles) (pointing needed because rectenna seen with various angles) Losses -, for polar regions (Snow, ice) + Maintenance + (In principle possible with the shuttle)
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