Initial on-Orbit Results from the GOES-18 Spacecraft Science Magnetometer

Abstract

AbstractThe Geostationary Operational Environmental Satellite (GOES)-18, the latest spacecraft from the NOAA GOES-R satellite series, was launched March 1, 2022. As with the previous GOES-16 and GOES-17 satellites, GOES-18 monitors sources of space weather on the Sun and its effects at Earth. NOAA uses GOES data as part of the national space weather forecasts, warnings and alerts to many customers. GOES-18 hosts new magnetometers called the Goddard magnetometers (GMAG) that replace those (called MAG) built by a different vendor on GOES-16 and GOES-17. Like the other GOES satellites, the GOES-18 GMAG provides observations of the geomagnetic field at geostationary orbit (35,786 km), a location that often provides early indication of enhanced space weather activity. In this paper, we review the capabilities of the GOES-18 GMAG along with lessons learned from the GOES-16/17 MAGs. The GOES-R series magnetometer instrument includes two magnetometer sensors (inboard and outboard) mounted along a boom extended from the spacecraft. As with the previous magnetometers, the GMAG sensors are three-axis fluxgates sampling the geomagnetic field at 10 samples/second, with the data low-pass filtered with a 2.5 Hz cutoff. On-orbit analysis demonstrates that the GOES-18 GMAG is a highly stable instrument showing little variations between the inboard and outboard sensors either diurnally or over multiple days. A nearly 2.5 months collocation between GOES-18 and GOES-17 (136.8°W and 137.2°W) allowed direct cross-satellite comparisons that was unprecedented for GOES satellites. Differences between the on orbit performance of the GMAG and MAG sensors are attributed to thermal stability issues observed on the GOES-17 MAG (also observed on the GOES-16 MAG). The cross-satellite analysis during the collocation interval, along with inboard/outboard sensor comparisons and comparisons to models, suggests that the GOES-18 GMAG meets the NOAA mission requirement of $\pm 1$ ± 1 nT accuracy, excluding arcjet firing periods. Arcjet firing periods were also excluded in performance analysis for GOES-16/17.