Day 4

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Paper title Networks of CubeSats and their potential for gravity field retrieval in the frame of the CubeGrav Project
  1. Nikolas Pfaffenzeller Technical University of Munich Speaker
  2. Roland Pail Technical University of Munich
  3. Klaus Schilling Zentrum für Telematik
  4. Panagiotis D. Kremmydas Zentrum für Telematik e. V.
Form of presentation Poster
  • B7. NewSpace missions
    • B7.03 New Space missions with small and nanosatellites
Abstract text In the frame of the CubeGrav project, funded by the German Research Foundation, Cube-satellite networks for geodetic Earth observation are investigated on the example of the monitoring of Earth’s gravity field. Satellite gravity missions are an important element of Earth observation from space, because geodynamic processes are frequently related to mass variations and mass transport in the Earth system. As changes in gravity are directly related to mass variability, satellite missions observing the Earth’s time-varying gravity field are a unique tool for observing mass redistribution among the Earth’s system components, including global changes in the water cycle, the cryosphere, and the oceans. The basis for next generation gravity missions (NGGMs) is based on the success of the single satellite missions CHAMP and GOCE as well as the dual-satellite missions GRACE and GRACE-FO launched so far, which are all conventional satellites.
In particular, feasibility as well as economic efficiency play a significant role for future missions, with a focus on increasing spatio-temporal resolution while reducing error effects. The latter include the aliasing of the time-varying gravity fields due to the under-sampling of the geophysical signals and the uncertainties in geophysical background models. The most promising concept for a future gravity field mission from the studies investigated is a dual-pair mission consisting of a polar satellite pair and an inclined (approx. 70°) satellite pair. Since the costs of realizing a double-pair mission with conventional satellites are very high, alternative mission concepts with smaller satellites in the area of New Space are coming into focus. Due to the ongoing miniaturization of satellite buses and potential payload components, the CubeSat platform can be exploited.
The main objective of the CubeGrav project is to derive and investigate for the first time optimized cube-satellite networks for Earth’s gravity field recovery, with special focus on achievable temporal and spatial resolution and reduction of temporal aliasing effects. In order to achieve the overall mission scope the formation of interacting satellites including the inter-satellite ranging measurements, relative navigation of the satellites and networked control of the multi-satellite system are also analyzed in a second step. A prerequisite for the realization of a CubeSat gravity mission is the miniaturization of the key payload, such as the accelerometer, which measure the non-gravitational forces such as the drag of the residual atmosphere, and the instrument for highly accurate determination of the ranges or ranges rates between the satellites.

This contribution presents recent results of the CubeGrav project and a preliminary mission concept and focuses on the scientific added value compared to existing satellite gravity missions. A set of miniaturized gravity-relevant instruments, including accelerometer and the inter-satellite ranging instrument, with realistic error assumptions are identified for a usage in CubeSats, and their capabilities and limits on determining gravity field are investigated in the frame of numerical closed loop simulations. The applicability of the above is further translated into potential preliminary satellite bus compositions and achievable orbital baselines. By this approach we can identify the minimum requirements regarding instrument performances and satellite system design. Additionally, different satellite formations and constellations will be analysed regarding their potential of retrieving the temporal gravity field.