The goal of this challenge is to study the ability of the different gravity field recovery methods to reproduce the underlying mass distributions (e.g. ice mass loss in Greenland) in a set of simulated GRACE Follow-On data. The challenge will be set up according to a realistic GRACE Follow-On configuration, and a known set of mass distributions will be input into the simulation. The resulting simulated data streams from the spacecraft are then published and analysed by the community with the aim of recovering the underlying, known mass signals.