5.1.3 Specific Technology Issues & Rationale Tether Discussion. The concept hinges around the use of a tether deployment system. This is not because future operational Powersats will require tethers, but because such a system reduces the cost and complexity of the initial demonstrator by eliminating the necessity for a rendezvous and orbit control capability. In other words, the tether replaces the function of maintaining the transmitter and receiver within close proximity to each another and at the correct orientation with respect to each other. However, the tether does not eliminate the need for a fine pointing system due to the uncertainties in the rectenna’s actual position. This approach fits in with the needs of the Powersat demonstrator programme. Without the availability of the tether, it would be necessary to equip the transmitter with the capability to free-fly in close formation and at the correct attitude with respect to the rectenna secured on the ASAP. This would require an attitude and translational control propulsion system, together with a rendezvous sensor and appropriate control systems and software. Assuming it was even feasible to build a Powersat demonstrator for under 50 kg, neither rendezvous or attitude and translational orbit control are critical capabilities that need to be proven. More importantly, the cost of developing such a capability would be formidable, and the ground operational costs would also be significant Other concerns that would add to the complexity are the fact that the orientation and stability of the H10 upper stage cannot be controlled. For example, the H10 is unlikely to be able to enter a steady gravity-gradient mode but will probably be tumbling at a slow rate. This would make an untethered Powersat experiment impossible. Even if a gravity gradient mode was achievable, there is no guarantee the H10 would be orientated in the proper direction. Specifically, the rectenna would need to be perpendicular to the
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