MAGIC investigating a solution for a worst-case scenario

The Mass-Change and Geosciences International Constellation (MAGIC) is planned to consist of two satellite pairs measuring the variations in the Earths gravitational field. The first pair launched into a near-polar orbit is planned to be launched in 2028 followed by a second pair to be launched in an inclined orbit no later than 2032. Considering the planned lifetime of seven year, an overlap of 3 years is anticipated. However, it is possible that the first pair is failing due to unforeseen circumstances before the launch or during the early phase of the second pair. The second pair will thus the only source for gravity field recovery resulting in an incomplete coverage of the Earth.The usual approach is to constrain the solutions, e.g. by Tikhonov or using a Kaula rule. This study investigates such a worst-case scenario but with a different approach. We consider a single GNSS-equipped satellite in a near-polar orbit that will contribute high-low satellite-to-satellite observations from GNSS to a common gravity field solution. We present the contribution of this observation type to the solution and quantify the degradation compared to the double pair and the improvement compared to a constrained solution.