GEOS-5 is not a satellite. It is a computer-based global atmospheric modeling system, maintained by NASA's Goddard research facility.
https://gmao.gsfc.nasa.gov/GEOS_systems/

GEOS-5 can generate SO2 (and other chemical) data by a kind of simulation (called 'reanalysis') from computed estimates of SO2 concentrations, which are initialized and then consistently updated by interpolating satellite and meteorological observations (e.g. winds) using the GEOS-5 atmospheric circulation model to make geospatial 'forecasts' of SO2 concentrations between actual observations.
https://acd-ext.gsfc.nasa.gov/People/Colarco/Mission_Support/
There are several satellites which carry SO2 sensors and can be used to initialize and update the GEOS-5 forecasts:
https://so2.gsfc.nasa.gov/

1. NASA's AURA OMI (Ozone Measuring Instrument) which has been in operation for more than a decade.
   https://www.atmos-chem-phys.net/16/4605/2016/
2. ESA's Copernicus Sentinel-5P TROPOMI (Tropospheric Monitoring Instrument)
   https://developers.google.com/earth-engine/datasets/catalog/COPERNICUS_S5P_NRTI_L3_SO2