The tests to be conducted with STE-QUEST require a highly elliptic orbit with the following characteristics:
An orbit with a 16-hour period, a minimum perigee altitude of ~600 kilometres, and an apogee altitude of ~51 000 kilometre is being studied for the mission. The orbit would evolve freely and would have the following characteristics:
The ground track can be optimised to maximise visibility at the STE-QUEST ground stations, which may be located in Boulder (USA), Turin (Italy), and Tokyo (Japan). These locations are particularly favourable because of their geographical distributions and vicinity to research laboratories operating highly stable and accurate atomic clocks.
The primary data product of the STE-QUEST mission will be:
Space-to-ground clock comparisons will be performed all along the orbit, and in particular, while the spacecraft is at apogee and perigee. In this way, Einstein's prediction of the gravitational frequency shift will be verified both by an absolute measurement between space and ground clocks and by examining the modulation of the redshift effect on the STE-QUEST clock between perigee and apogee.
STE-QUEST will also allow common-view comparison of terrestrial clocks, which can be used to measure the periodic effect of the gravitational frequency shift induced by the Sun.
The atom interferometer will primarily perform differential acceleration measurements while the spacecraft is around perigee (spacecraft altitude below 3000 kilometres), thus maximising the signal-to-noise ratio of a possible violation of the Weak Equivalence Principle.
The STE-QUEST ground segment is composed of:
Close monitoring of the spacecraft will be necessary during the on-orbit characterisation phase which is expected to last for the first 6 months of the mission.
The payload will be operated on the basis of scheduled sequences of commands which will be uploaded to the spacecraft and executed on board
The estimated data volume is compatible with small ESOC ground stations.