GNSS Altimetry in the Gulf of Mexico Based on Spire Cubesat Carrier-Phase Data

This paper evaluates the ocean altimetry retrievals derived from grazing-angle GNSS reflections collected on Spire Low-Earth-Orbit (LEO) and low-cost CubeSats. Carrier-phase altimetry requires coherent GPS signal reflections, which happens mainly at grazing angles and over calm ocean surfaces. These conditions are found primarily in the Indonesian Seas and several weeks in the gulf-of Mexico (GoM) during 2020 and offer the possibility for sea level cross-validations. This investigation confirms the consistency of the carrier-phase Spire observations among platforms. A preliminary assessment of the Spire altimetry retrievals against conventional altimetry products over the GoM characterized by its strong loop-current show the potential for Spire altimetry to capture sea level features but there is a scaling issue which increases at low elevations.