EIRMA-An Energetic Ion Retarding Mass Analyzer for the BERT-1 Beam Emission Rocket Test-One.

The AFGL Beam Emission Rocket Test-One (BERT-1) launched in June 1985, included in its instrumentation an Energetic Ion Retarding Mass Analyzer (EIRMA) to study the mass and energy distribution of positive ions in the return current to the spacecraft from which energetic ion and electron beams are emitted. The EIRMA is a quadrupole mass filter scannable over the 1 to 100 amu range with programmable resolution delta m/m to less than 1/15. The filter was biased by programs over a -100v to +4.5 kv range, allowing a retarding analysis of individual ion species in the return current. The report is a summary description of the instrument design, performance testing results and flight performance. Keywords: Retarding analyzer, Ion mass analyzer, Quadrupole mass filter, Energetic beams, Spacecraft charging.