Peter Roberts

Drag Sail for End-of-Life Disposal from Low Earth Orbit

International standards are moving toward the requirement that spacecraft should be removed from orbit at the end of their operational lives. The feasibility of a deployable aerodynamically stable drag-enhancement structure is considered for the end-of-life disposal of low-Earth-orbit spacecraft, and how this structure could fulfil NASA deorbit guidelines is demonstrated. The concept is a thin membrane supported by deployed struts. A shuttlecock like geometry is chosen to take advantage of the small stabilising effect caused by oscillatory motion in, and descent through, the free molecular flow during deorbit. The shuttlecock is approximated to a cone, and the aerodynamic loads due to orbital and rotational motion are calculated and used to model the stabilisation and descent of a deployed system toward final reentry. Finally it is is shown that this system can provide an effective and mass-efficient deorbit solution for future missions.

Science Operations Planning Optimization for Spacecraft Formation Flying Maneuvers

The use of formation flying of distributed space systems, especially for space-based interferometry, is receiving much attention by mission designers. Optimal manoeuvre planning for these missions is critical to ensure the safe operation of the spacecraft and to maximise the mission science returns. One such mission, Darwin, requires complex observation scheduling complicated by a number of interconnected temporal constraints placed not he mission. Following a defined manoeuvre planning architecture this paper introduces a science operations planner that helps maximise observation time through science operations schedule optimisation. Comparison of this method with a simple benchmark planner is given and shows that schedule performance increases of up to 12% can be achieved. Though these increases can only be achieved using significantly more computation resources than the benchmark planner, they are found using constraints that would allow the planner to be able to operate autonomously onboard one of the formation spacecraft.

Maneuver planning optimization for spacecraft formation flying missions

Formation flying of spacecraft in orbit around the Earth and in deep space is becoming an enabling technology for a number of space mission concepts. One such concept is separated spacecraft interferometry, a technique to be used by ESA’s Darwin planet finding mission. In this paper, a maneuver planning algorithm is introduced designed to find the post-maneuver spacecraft positions that satisfy interferometry science goals whilst optimizing for fuel use or fuel balancing considerations. Compared to a benchmark planning algorithm gains of up to 23% less fuel for fuel minimizing maneuvers and a significant increase in fuel balancing for fuel balancing maneuvers are observed using Darwin-like mission parameters.