Calibration and Initial Results of Space Radiation Dosimetry Using the Imesa‐r

The integrated Miniaturized Electrostatic Analyzer‐Reflight (iMESA‐R) is a space weather instrument designed to measure plasma density, temperature, and spacecraft charging, along with total ionizing dose and dose rate. A constellation consisting of five nearly identical instruments has been designed and developed to act as science payloads hosted on‐board Department of Defense satellites operating in low‐Earth orbit. To validate the dosimetry component of the iMESA‐R, a radiation test study was performed to calibrate the dosimeter and ascertain the attenuation due to the instrument aluminum housing. An 80 curie Cobalt‐60 radioisotope source emitting beta, X‐ray, and gamma ray radiation decay products was used to calibrate the dosimeter response as a function of distance and instrument shielding. We present results of the calibration study along with initial on‐orbit data presented from the first operational iMESA‐R hosted on‐board Space Test Program Satellite 5 in a polar Earth orbit. The initial on‐orbit data demonstrate the ability to map the radiation environment, particularly the South Atlantic Anomaly and the auroral regions using total ionizing dose rate due to electrons of E > 1.5 MeV and protons of E > 25 MeV.