Note 2 – Free formation flying Sample Clauses

Note 2 – Free formation flying. Largely from considerations which occurred in . There are two main categories of 3F satellites. Those for which knowledge of the position is required but no actual high precision control is required (ESPRIT) and those for which the high precision is required in actual relative positioning of the satellite. For the latter category of interest here, and similarly to a length dependence of the TRL for the booms, free-formation flying TRL can be argued to decrease almost proportionally to the tolerance with which the inter- satellite distance must be kept. At present, PRISMA results obtained cm-accuracy on large scale distances. Whilst current work on PROBA3 (to be launched in 2018) is aiming at mm-accuracy for most positioning tolerances. In addition, mass and overall size of the satellite is likely to also impact statements of TRL. As such FFF TRL is arguably at the lowest given that for 3 satellites (2 telescope and 1 hub) of masses ~ 5 to 10x that of PROBA3, a control requirement along the satellite axis of the order of a fraction (1/10th) of the shortest wavelengths brings this to 3 order of magnitudes smaller than what can be achieved with the launch of PROBA3. One alternative is to consider dynamic compensation of such a distance through accurate and redundant metrology, with a fast variable delay stage which compensates most axial displacements in real time. This would allow requirements to relax to the order of mm while introducing an additional subsystem, the TRL of which is much less complex to advance. With these considerations a TRL of 6 (7 post PROBA3) could be assumed, otherwise the gap between 2 (current), 3 with lessons learned from PROBA3 to increment model accuracy and 4 is too wide to expect to be bridged during the rest of this decade.