Spire, CubeSat, GNSS, POD, Gravity field recovery, ICGEM, HLSST, SLR, Short arc approch
Abstract :
[en] In 2016, Spire Global Inc. began manufacturing commercial CubeSats to
analyze Radio Occultation (RO) data from Global Navigation Satellite Systems
(GNSS). While RO measurements have been used for various applications,
including atmospheric research and ice sheet height estimation, the zenithlooking
Precise Orbit Determination (POD) antenna introduces possibilities for
geodetic applications. Each Spire LEMUR CubeSat is equipped with a dualfrequency
Global Positioning System (GPS) antenna and an Attitude
Determination and Control System (ADCS).
Leveraging the measurements provided by the POD antenna and the ADCS,
Earth’s gravity field recovery emerges as a promising application, offering the
opportunity to use small satellite constellations for increased temporal
resolution. The POD of Spire CubeSats constellation, performed using the raw
observation approach, has been applied to model Earth’s gravity field through
the short arc method.
The Spire CubeSats, with different orbital characteristics, can be used
individually or in combination to analyze the time-variable components of the
Earth’s gravity field. Combining individual gravity field solutions results in
improved accuracy compared to standalone models. This framework provides
the opportunity of combining Spire-based gravity field models with those
obtained from low Earth orbit (LEO) dedicated or non-dedicated gravimetric
missions that offer higher accuracy. In this contribution, monthly gravity field
solutions from 10 Spire CubeSats constellations are combined with the
QuantumFrontiers HLSST_SLR_2023s solutions at the normal equations level
(NEQs) using the variance component estimation (VCE). The quality of the
combined Spire + SST-hl + SLR monthly gravity field solutions is then
compared with the ITSG-GRACE gravity field model for 2020.
