Intersatellite Comparisons of GOES Magnetic Field Measurements

GOES‐16 and GOES‐17 are the first of NOAA's Geostationary Operational Environmental Satellite (GOES)‐R series of satellites. Each GOES‐R satellite has a magnetometer mounted on the end (outboard) and one part‐way down a long boom (inboard). This paper demonstrates the relative accuracy and stability of the measurements on a daily and long‐term basis. The GOES‐16 and GOES‐17 magnetic field observations from 2017 to 2020 have been compared to simultaneous magnetic field observations from each other and from the previous GOES‐NOP series satellites (GOES‐13, GOES‐14 and GOES‐15). These comparisons provide assessments of relative accuracy and stability. We use a field model to facilitate the inter‐satellite comparisons at different longitudes. GOES‐16 inboard and outboard magnetometers data suffer daily variations which cannot be explained by natural phenomena. Long‐term‐averaged GOES‐16 outboard (OB) data has daily variations of ±3 nT from average values with one‐sigma uncertainty of ±1.5 nT. Long‐term averaged GOES‐17OB magnetometer data have minimal daily variations. Daily average of the difference between the GOES‐16 outboard or GOES‐17 outboard measurements and the measurements made by another GOES satellite are computed. The long‐term averaged results show the GOES‐16OB and GOES‐17OB measurements have long‐term stability (±2 nT or less) and match measurements from magnetometers on other GOES within limits stated herein. The GOES‐17OB operational offset (zero field value) was refined using the GOES‐17 satellite rotated 180° about the Earth pointing axis (known as a yaw flip). Plain Language Summary GOES‐16 and GOES‐17 are the first two of the R‐series of the NOAA's Geostationary Operational Environmental Satellite (GOES). Like previous GOES satellites, they carry two magnetometers (inboard and outboard on a long boom) to measure the magnetic field at geosynchronous orbit (an altitude of approximately 35,786 km above mean sea level). Because these data are used to provide users of space‐based assets with the knowledge of the space environment and to provide input for research, the accuracy and stability of the new data sets relative to previous data sets are important. There are known variations in the data from the station‐keeping thrusters which are removed from the data studied. Previous studies showed that the GOES‐16 measurements contain artificial diurnal variations. This study shows that the diurnal variations of the outboard magnetometer data are us