Calibration and Initial Results of Space Radiation Dosimetry Using the iMESA‐R

Abstract

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.

Toward the Use of Electronic Commercial Off-the-Shelf Devices in Space: Assessment of the True Radiation Environment in Low Earth Orbit (LEO)

“…The results are comparable to the ones obtained in the ISS, with similar differences between measurements and models for the same orbit and duration. Some experiments have been carried out on nanosats such as Timepix [37] or iMERSA-R [38], and on cubesats with experiments such as Lucky7 [39], where active radiation sensors were installed. These missions have demonstrated their ability to detect and accurately determine the flow of protons and electrons.…”

Review of in-space plasma diagnostics for studying the Earth’s ionosphere

“…GPIM (158 kg, ∼715 km altitude, launched in 2019), OTB-1 (∼720 km altitude, launched in 2019), STPSat-4 (∼420 km altitude, launched in 2019), STPSat-5 (115 kg, planned), and STPSat-6 (geosynchronous orbit, planned) have or will have onboard an improved version of the iMESA called integrated miniaturized ESA-reflight (iMESA-R). The iMESA-R was developed to act as simultaneous multi-point sensors to measure plasma density, temperature, spacecraft charging, and total ionizing dose (TID), which was not included in the original iMESA [76]. The design of the iMESA-R used in the five satellites is very similar to ensure consistency across their data.…”

“…Besides demonstrating that the sensors were accurate, the ground tests of the iMESA-R also showed that the Al housing encasing the sensor effectively filters out lowenergy electrons and protons, and it only mildly attenuates gamma rays. The initial data from iMESA-R on STPSat-5 is available in [76], and future integration of data from all five iMESA-R sensors is expected to make the measurements more accurate.…”

“…The electron density at 500 km is an order of magnitude lower than at 350 km, so the signal-to-noise ratio was relatively low given that the electronics were not modified to work well at 500 km, which required the data to be aggressively selected. Nonetheless, for the next iMESA-R sensors, the electronics were designed for their orbital altitude and could cover an altitude range between 300 km to 720 km [76]. The electronics for iMESA-R were fully integrated to the instrument of size 118.75 mm × 101.60 mm × 34.42 mm with energy consumption between 2.1 W (when dosimetry is inactive) and 2.5 W (when dosimetry is active) [73].…”

“…In addition, data integration from multiple sensors probing the same plasma will increase the accuracy of the measurements [76] and make possible to conduct more consistent, accurate, and useful assessments via data fusion. For example, in 2000, the Ukrainian satellite SICH-1M was launched as part of the VARIANT space experiment project [70].…”