The integrated Miniaturized Electrostatic Analyzer (iMESA) was a satellite-based ionospheric sensor that operated on NASA’s Space Test Program Satellite (STPSat-3) from December 2013 to July 2019. The instrument’s scientific objective was to (1) measure the plasma density in low Earth orbit, (2) measure the plasma temperature in low Earth orbit, and (3) quantify the spacecraft potential with respect to the ambient plasma potential in the ionosphere. iMESA sampled the ionosphere every 10 s by measuring the ion current density through the ESA as a result of the motion of the spacecraft through the plasma. Current density spectra were transmitted to the ground where they were post-processed into ion density spectra and then analyzed numerically to determine the ion density, ion temperature, and spacecraft potential. This article discusses the instrument design and simulation, the determination of a geometric factor, and data processing procedures and evaluates the final data product with regard to the mission success criteria. The ion density and ion temperature captured by the iMESA instrument are on the same order and range as the values predicted in the literature. The spacecraft potential was also quantified. The conclusion after the evaluation of the instrument’s data product is that the scientific mission is successful on all three points.
A compact electrostatic energy bandpass filter based on a laminated analyzer design has been developed to measure charged particle fluxes at energies ranging from 0 to 5 keV. The sensor head has been successfully tested against a low energy magnetically filtered plasma source and an ion beam source capable of producing energetic ions in the range of 100–1250 eV. Additionally, the instrument has demonstrated the ability to accurately measure negative spacecraft frame charging using a low Earth orbit plasma simulator. The effects of the spacecraft frame charging on the measured energy distribution measurements and the impact regarding the derived charged particle density and temperature parameters are also examined.
Key Points
Air Force Academy cadets design and build a space weather constellation
Instruments measure plasma density and temperature, spacecraft charging, total dose, and dose rate
Increasing density of in situ measurements improves space weather forecast
Contamination from outgassed materials, venting, leaks, and impinging thruster plumes can cause deleterious effects to sensitive experiments on the International Space Station. In low Earth orbit, intermolecular collisions between neutral contaminants and ions in the ambient ionospheric environment result in an elevation in the local charged particle density through a process called charge exchange (CEX). Of particular concern to spacecraft engineers is the acceleration of these ionized neutrals to sensitive negatively charged spacecraft surfaces. The increase in plasma density due to CEX can be readily measured using plasma diagnostics such as electrostatic energy analyzers. These instruments are capable of monitoring charged particle flux and are sensitive enough to measure small changes in local density, thus allowing for the detection of CEX contaminants. The automated plume sentry (APS) is one such instrument, and it has successfully detected CEX plasma generated by the planned ammonia venting of the external active thermal control system. The data collected by the APS will support the development of improved computational models to predict the propagation of outgassed materials and plumes in the ionosphere and complex gas–surface interactions resulting in spacecraft surface contamination.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.