Integrated Inertial Sensors and Laser Ranging Instruments for Small Satellite Earth Geodesy Constellations (ILaRIS)

We plan to develop a compact inertial sensor and integrated laser interferometer for low-cost small satellite Earth geodesy constellations. Our concept has the potential to be disruptive, enabling dozens of satellite pairs at a cost that is comparable to previous Earth geodesy missions. The potential science return from the higher accuracy instruments and increased satellite constellation size would help resolve questions about how the global Earth system is changing. It would improve the accuracy and resolution of gravity field measurements, increasing our understanding of climate variability and change, including critically important temporal and spatial changes in the mass of Earth's ice cover and water. The instrument and satellite platform will take advantage of NASA and European Space Agency investments in technology for Earth geodesy and space gravitational wave detection. The inertial sensors (IS) will have an improved acceleration noise performance relative to the ONERA sensors employed in the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow On (GRACE-FO) missions, achieving an acceleration noise of <10^–12 m/s^2Hz^1/2, a factor of 100 improvement over the ONERA sensors. To do so, the IS design will capitalize on technologies developed for LISA Pathfinder and performance models that were validated by flight data from that mission. With these models, we will tailor the design to meet the desired performance of next-generation geodesy missions, while minimizing the size, weight, and power of the sensor. The inertial sensor will incorporate a laser interferometer port for direct interrogation, and we will develop a strategy to modify the GRACE-FO laser ranging interferometer (LRI) to allow direct integration with the IS. An inertial sensor and spacecraft designed from the start with laser interferometry in mind will allow an LRI with a smaller mass and volume than that used on GRACE FO, for example, by eliminating components that were only needed to allow GRACE-FO to use the GRACE spacecraft and microwave ranging instrument. By integrating a compact inertial sensor and laser ranging interferometer, and eliminating the microwave ranging system used on GRACE and GRACE FO, a low-low satellite-to-satellite tracking geodesy mission could be realized on a small satellite, for example an ESPA-class platform or smaller. The reduced cost to develop and launch this small satellite and instrument would enable a larger number of pairs of satellites to be employed in future geodesy missions. Because of the higher frequency with which they observe any given location on the Earth, multi-satellite systems can increase the temporal resolution of gravity field maps. Mixed-orbit constellations can also markedly enhance observational strength, decorrelate gravity coefficient estimates, and help address the fundamental aliasing/modeling problem that exists with previous missions. The constellation approach is also scalable and could take advantage of improved technologies when they become available. We will develop the conceptual design of the inertial sensor and laser ranging interferometer considering the size, mass, and power constraints of small satellite platforms. The performance of the inertial sensor will be based on analytical models developed for the LISA and LISA Pathfinder missions and validated using noise measurements made with the University of Florida torsion pendulum, which is capable of measuring the performance of inertial sensors down to ~10^–13 m/s^2Hz^1/2 around a few mHz. We will also evaluate the science return for an optimized set of orbits for small satellite pairs in terms of the spatial, temporal resolution and accuracy of the recovered geopotential. In this analysis, we will consider both rideshare opportunities and Venture class launches that enable launches into desired orbits for each pair of satellites at relatively low cost.

Increase scientific understanding of natural phenomena using remote sensing

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