SPACECRAFT POTENTIAL EFFECTS ON THE DYNAMICS EXPLORER 2 SATELLITE

The relationship between the plasma environment and spacecraft potenti al is examined for the Dynamics Explorer 2 (DE 2) spacecraft in an att empt to improve the accuracy of ion drift measurements by the retardin g potential analyzer (RPA). Because of the DE 2 orbit characteristics (apogee near 1000 km and perigee near 300 km) and the configuration of conducting surfaces on the spacecraft, thermal electrons and ions con stituted the only significant contributions to the charging currents t o the spacecraft surface for the majority of geophysical conditions en countered. The geomagnetic field had considerable effect on the spacec raft potential due to magnetic field confinement of the electrons as w ell as to the V x B electric field resulting from the movement of the spacecraft across magnetic field lines. Using a database of inferred s pacecraft potentials from the RPA, measured electron temperatures from the Langmuir probe (LANG), and calculated V x B electric fields, we d erive an algorithm for determining the spacecraft potential (at the lo cation of the RPA on the spacecraft) for any point of the DE 2 orbit. Knowledge of the spacecraft potential subsequently allows us to retrie ve relatively accurate ion drifts from the RPA data.