Cube-satellite networks for geodetic Earth observation on the example of gravity field retrieval (CubeGrav)

• Applicants: Professor Dr. Roland Pail; Professor Dr. Klaus Schilling
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Automation, Mechatronics, Control Systems, Intelligent Technical Systems, Robotics
• Term: from 2020 to 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 440392851

• Final Report Year: 2024

Final Report Abstract

A feasibility study (Phase A) of a potential cube-satellite (CubeSats) gravimetry mission for monitoring the Earth’s gravity field was performed. We analyse scientific requirements based on user needs, and identify and assess potential candidate instruments. In order to reduce the main error source of current gravity field missions, i.e. temporal aliasing resulting from under-sampling of high-frequency mass signals, CubeSat constellations of multiple satellite pairs are investigated. We select the constellation of 4 polar and 4 inclined satellite pairs, distributed on several orbital planes, as the most promising candidate. The system design focuses on developing a satellite platform that fulfills the scientific precision requirements while preserving the CubeSat structure and meeting the resulting budget constraints. By integrating flight-proven technologies from missions like NetSat and QUBE, the design ensures reliability. The propulsion system, using a standard chemical module with nitrous oxide and propene, balances performance and simplicity. Detailed analysis of Delta-V capabilities and propellant slosh will ensure mission stability. The power system, with deployable solar panels, maximizes energy generation. A preliminary power budget indicates optimal energy restoration with stable pointing. However, several remaining challenges have been identified: The current bottleneck of the mission is the availability of scientific payload fulfilling the performance requirements and simultaneously the size, weight and power requirements. Based on the provided volume numbers, a reduction of at least 35% is necessary for the ranging instrument and the accelerometer to be fitted into the selected 6U CubeSat design. Since the satellite pairs are distributed on multiple orbital planes, an appropriate rideshare needs to be identified or own launch vehicles have to be used. In summary, we can conclude that a constellation of multiple CubeSats can provide significant added value for temporal gravity field retrieval and the monitoring of several climate-relevant processes with increased temporal resolution, and should be investigated in a phase B study in more detail.

Publications

• Multi-satellite formations and constellations of CubeSats and their potential in NGGMs. Scientific Assembly of the International Association of Geodesy, 2021
  Pfaffenzeller, N. & Pail, R.
  
• Observing the Earth´s Gravity Field with CubeSats – Constellation Design Study. 12th European CubeSat Symposium, 2021
  Pfaffenzeller, N. & Pail, R.
  
• Simulation study on gravity field determination with small satellites in NGGM. European Geosciences Union General Assembly, 2021
  Pfaffenzeller, N. & Pail, R.
  
• Capabilities and limits of Multi-satellite constellations and formations for temporal gravity field retrieval. ESA Living Planet Symposium, 2022
  Pfaffenzeller, N. & Pail, R.
  
• Gas-Surface performance indicators in a Very Low Earth Orbit CubeSat mission. 44th COSPAR Scientific Assembly, 2022
  Kremmydas, P. D., Nazlidou, P. & Schilling, K.
  
• Networks of CubeSats and their potential for gravity field retrieval in the frame of the CubeGrav Project. Deutscher Luft- und Raumfahrtkongress, 2022
  Pfaffenzeller, N., Pail, R., Schilling, K. & Kremmydas, P. D.
  
• Networks of CubeSats and their potential for gravity field retrieval in the frame of the CubeGrav Project. ESA Living Planet Symposium, 2022
  Pfaffenzeller, N., Pail, R., Schilling, K. & Kremmydas, P. D.
  
• Potential and limits of small satellite networks for temporal gravity field retrieval in the frame of the CubeGrav Project. European Geosciences Union General Assembly, 2022
  Pfaffenzeller, N. & Pail, R.
  
• Capabilities of multi-satellite constellations for the co-estimation of ocean tide constituents on different time scales. MAGIC Science and Applications Workshop 2023
  Pfaffenzeller, N. & Pail, R.
  
• Potential and limits of small satellite missions for determining ocean tide constituents on different time scales. 28th International Union of Geodesy and Geophysics General Assembly, 2023
  Pfaffenzeller, N. & Pail, R.
  
• Small satellite formations and constellations for observing sub-daily mass changes in the Earth system. Geophysical Journal International, 234(3), 1550-1567.
  Pfaffenzeller, Nikolas & Pail, Roland
  
• Capabilities of ocean tide aliasing reduction by co-estimation of major constituents with future satellite constellations. Symposium on Gravity, Geoid and Height Systems 2024
  Pfaffenzeller, N. & Pail, R.
  
• Future satellite gravimetry with a network of miniaturized satellites. Gravity, Geoid and Height Systems Symposium 2024
  Pfaffenzeller, N., Pail, R., Jesen, J., Kamble, P. V., Datar, T., Kleinschrodt, A. & Schilling, K.