First Results from the Spire GNSS-R Payload CubeSat Missions

Spire Global, Inc. operates the world's largest and rapidly growing constellation of CubeSats performing GNSS-based science and Earth observation. Currently, the Spire constellation consists of 84 3U CubeSats, with 30+ satellites capable of performing a variety of GNSS science, including radio occultation, ionosphere measurements, and precise orbit determination. Beginning in 2018, Spire began an effort to design and build the first of many GNSS-R missions for Earth observations for a variety of applications, including soil moisture measurement, wetlands and flood inundation mapping, sea surface roughness and winds, and sea ice characterization. Following an agile model of rapid, iterative satellite development that has been refined over many years to produce radio occultation payloads optimized for operation on ultra-small 3U CubeSats, we adopted a very aggressive schedule to adapt the current Spire 3U bus and STRATOS GNSS science receiver to perform GNSS-R measurements, with an expected launch in late 2019. We will discuss the goals of the 2019 Spire GNSS-R missions, the design and operational modes of the first batch of Spire GNSS-R satellites, and plans for an iterative design effort for the next batch of Spire GNSS-R satellites. We will highlight the differences between Spire's first GNSS-R mission and other GNSS-R missions, such as TechDemoSat-1 and the CYGNSS constellation of satellites. Depending on launch schedule, we will also present initial on-orbit results of the first Spire GNSS-R mission.