LISA Pathfinder Payload
The sensor complement of the LISA Pathfinder mission consists of two major components – the LISA Technology Package (LTP) with its Cold Gas Micro Propulsion Subsystem and the Disturbance Reduction System (DRS) provided by NASA. Both systems will test the key technologies for drag-free control in a system that is comprised of three orbiting bodies, essentially a small formation flying exercise of three parts – the LISA Pathfinder spacecraft and the two proof masses within it.
The metrology concept for the mission calls for one of the masses to be in ‘perfect’ free fall in all translational degrees of freedom, no force is purposely applied to this particular mass. The spacecraft follows the first test mass by using its drag-free control system that enables it to ‘free fall’ along with the mass with sufficient accuracy. The second mass is free along the y and z axes and the spacecraft can follow this by using rotation around these two axes.
The high-precision measurement system will track the motion of the test masses relative to the spacecraft to allow for test-mass to test-mass tracking with an accuracy unaffected by spacecraft motion – even for test masses in different spacecraft which will be the case for eLISA.
Test-mass to test-mass tracking in eLISA will need three measurements – the test mass to its respective spacecraft and the two spacecraft relative to each other. A reconstruction of the pure test-mass motion can be made from these three measurements which are also being made in the LISA Pathfinder mission, just within a single spacecraft.
LISA Pathfinder Payloads: