Juggling Spacecraft: Similarities and differences of eight microsatellites for the CYGNSS mission

Abstract

The goal of any system in which there is a large set of components that are mostly similar, but have a non-negligible set of differences, is to find the balance between a “one-size-fits-all” approach, and a “unique-per-system-and-customizable” approach. This paper discusses how the balance between these two extremes is achieved as part of the ground segment and flight segment that will support the eight microsatellites of the National Aeronautics and Space Administration (NASA) Cyclone Global Navigation Satellite System (CYGNSS) mission. The NASA CYGNSS mission aims to understand the coupling between ocean surface properties, moist atmospheric thermodynamics, radiation, and convective dynamics in the inner core of Tropical Cyclones (TCs). The mission is comprised of eight microsatellites in Low-Earth Orbit (LEO) at an inclination of 35 degrees. As discussed in “The CYGNSS Ground Segment: Innovative Missions Operations Concepts to Support a Micro-Satellite Constellation” [1], previously presented at IEEE Aerospace 2013, the ground segment system must take into account the unique aspects of each microsatellite, including unique Spacecraft Identification (SCID) schemes, setup of multiple ground system consoles, definition of telemetry limits unique to a microsatellite, and any unique table or command loads. This paper expands upon the previously presented paper on the ground segment, and discusses how each of these details has been addressed in the implementation of the CYGNSS mission. This includes discussion of how Spacecraft I/Ds are defined onboard via the avionics, how the FSW table configurations vary between microsatellites, and whether or not a “one-size-fits-all” approach of FSW images is necessary for each microsatellite. The CYGNSS mission completed Preliminary Design Review (PDR) in 2014, Critical Design Review (CDR) in 2015, and is expected to launch in late 2016.