Arcjet Thruster Influence on Local Magnetic Field Measurements from a Geostationary Satellite

Abstract

The 16th Geostationary Operational Environmental Satellite(GOES-16) is the first satellite launched fromNational Oceanic and Atmospheric Administration's (NOAA's) next-generation Geostationary Operational Environmental Satellite-R series. Observations from GOES-16 are used by the NOAA to provide terrestrial and space weather forecasts, warnings, and alerts. The magnetometer (referred to as MAG) on GOES-16, which monitors the geomagnetic field, consists of two triaxial fluxgate magnetometers mounted on an 8.5 m boom. The spacecraft uses hydrazine arcjet thrusters for station keeping; when the arcjets are fired, a large magnetic field disturbance contaminates the MAG data. Here, the characteristics of the arcjet contamination are described and possible physical mechanisms for the magnetic field disturbance are discussed. The arcjets operate for ∼90 min approximately every four days, and the contamination significantly impacts the utility of the MAG data for space weather operations. The arcjets create step changes in the geomagnetic field observations of up to about 20 nT (∼20% of the nominal field strength). Two separate physical mechanisms are suggested: a large-scale diamagnetic effect caused by the dense plasma in the thruster plume, and a local current source caused by plasma pressure gradients near the thruster.