Design of control electronics for the Ram Energy Distribution Detector

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Virginia Tech

The bulk motion of the neutral gas at altitudes between about 200 and 600 km is an important factor in predicting the onset of plasma instabilities that are known to distort and/or disrupt high frequency radio communications. A ram wind sensor is a space science instrument that, when mounted on a satellite in low-Earth orbit, makes in-situ measurements of the component of the neutral gas velocity that lies along the orbit track of the satellite. The instrument works by changing the voltage on one of a set of grids and measuring a corresponding electron current generated by ions flowing through the grid stack and detected by the microchannel plate, generating a function of current vs. voltage called an I-V curve. Traditionally, the size and power requirements of ram wind sensors has limited their use to larger satellites. In this thesis, the electrical design and basic testing of a cubesat compatible RWS known as the ram energy distribution detector (REDD) are described.

The mechanical design of the REDD sensor is first described, and the requirements of the electrical design are presented. The electrical requirements are based on both the characteristics of the ionosphereic flight environment, and on the size and power requirements typical of the small cubesat platforms for which the instrument is intended.

The electrical hardware is then described in detail. The microcontroller design is reviewed as well, including the instrument's operating mode, and timing scheme.

Test data showing the basic functionality of the instrument are then presented. Bench tests validate the design by confirming its ability to control voltages and measure small electron currents. End-to-end tests were also performed in a vacuum chamber to mimic the ionospheric environment. These data are presented to show the ability of the REDD sensor to meet or exceed its design specifications.

ram wind sensor, cubesat, instrument electrical design