STEP mission and system design

Abstract

STEP (satellite test of the equivalence principle) is a candidate mission, in the discipline area of `fundamental physics', for the third medium-size project (M3) of ESA's long-term science programme `Horizon 2000'. A phase A study of the spacecraft and mission has been carried out by an industrial consortium led by Alenia Spazio, with Matra Marconi Space and Dornier Satellitensysteme as subcontractors. The concept that was studied was for an autonomous ESA mission with a payload provided by principal investigators. The model payload includes four equivalence principle accelerometers, a spin-coupling accelerometer and a gradiometer. A helium cryostat provides the required cryogenic temperatures for the payload. Spacecraft and warm payload equipment are accommodated on two platforms surrounding the cryostat. STEP will be launched with a Lockheed Martin LMLV-2 launch vehicle directly into its Sun-synchronous operational orbit at 400 km.