Plasma diagnostics package measurements of ionospheric ions and shuttle‐induced perturbations

Abstract

The plasma diagnostics package (PDP) on the space shuttle STS‐3 mission in March 1982 carried among its instrument complement a retarding potential analyzer. This instrument measured both the ambient ion plasma density and temperature, and perturbations to the plasma produced by shuttle orbiter effects. Whenever the plasma flow streamline at the instrument was more than a distance of the order of thermal ion gyroradii away from any orbiter surface, the measurements were characteristic of the ambient ionosphere. In several situations, the PDP was positioned so as to scan the wake in the plasma flow produced by orbiter surfaces. The density profile of the major species O+ was consistent with a classic Mach cone. However, strong perturbations extended for several meters outside the Mach cone which resulted in failure of flowing Maxwellian distributions to represent the data. Configurations where the plasma flow impacted orbiter surfaces downstream of the PDP resulted in generation of a suprathermal ion component. The observations are discussed in terms of a recent model of the mechanism for generation of shuttle glow.