Accelerometer development at Stanford

Abstract

Preflight prototype differential accelerometers for STEP are being developed at Stanford under NASA funding. Subsystem development in progress includes work on thin-film superconducting circuits deposited on cylinders, SQUID-based superconducting position measurement and electrostatic positioning and charge control. A thorough programme of testing and qualification of the subsystems is an essential part of the experiment. We have built a flux microscope and magnetometer probe to study magnetic flux motion, one of the limiting factors in the accelerometers; a position sensor study facility; a tipper table for testing and qualification of bearings in three degrees of freedom and a `mechatronics' lab for the manufacture of critical circuits on cylinders. A rigorous testing programme is a necessary part of any space experiment because it is presently impossible, or prohibitively expensive, to repair any failure after the experiment is in orbit. This is particularly true of fundamental physics experiments such as STEP and GP-B in which the sensitivity of the apparatus depends directly on the absence of gravity. Thus the apparatus cannot be tested at full sensitivity until it is in orbit. The STEP development work at Stanford is directed toward a partial answer to this problem, which guarantees that the instrument will at least function and tests it to the extent possible on the ground.

The MICROSCOPE space mission

“…Many space experiments have also been studied and proposed over the past years, but these missions have not yet been selected because they have been considered by the space agencies to be too complex, difficult to implement and expensive [8][9][10][11].…”