MARVEL mission proposal: The latest update

Following the recommendations of the 2019 CNES scientific prospective seminar, a pre-Phase-A study was launched in January 2020 at CNES on the concept of the MARVEL mission. MARVEL proposed to carry out in a single mission the survey of earth mass transfers with increased precision and the determination of the terrestrial reference system, thanks to two constellations of satellites at 500 and 7000 km altitude equipped with "radial" measurement links between the constellations. The results of the first six months of this pre-Phase-A will be presented.

Our work has mainly focused on two axes:
- a closed-loop numerical simulation to assess the scientific performance of a large number of orbital configurations, including radial links but also "Bender" and "Pendulum" configurations;
- a technological study to bring the precision of a laser inter-satellites chronometry link to the micrometric level.

This work has, so far, highlighted:
1 / the poorer performance for the determination of the gravity field of the "radial" type measurements compared to a "pendular" configuration in which the satellites are at the same low altitude with the ascending nodes of their orbits slightly offset so that the measurements between the spacecraft are alternatively oriented to the right and to the left of the track, thus improving the geometric configuration compared to an in-line pair of satellites;
2 / the technological possibility of achieving by chronometric laser link, over a few hundred or even a few thousand km, the precision of 1 micrometer in distance and 0.1 micrometer/s in relative velocity (which is necessary for the achievement of the scientific objectives).

The pre-Phase-A MARVEL, taking into account the "Mass Change" studies on the NASA side and "NGGM" on the ESA side, is therefore reoriented towards a "pendulum" type mission, abandoning the objective of determining jointly the terrestrial reference system.