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The ROPE investigation is designed to study the behavior of the ambient ionospheric charged particle populations and of ionized neutral particles around the TSS-1 satellite under a variety of conditions. Since the collection of free electrons from the surrounding plasma produces current in the tether, knowledge of the behavior of charged particles is essential to understanding the physics of tether current production.
From its location on the 1-m fixed boom, the Differential Ion Flux Probe measures the energy, temperature, density, and direction of ambient ions that flow around the satellite and neutral particles that have been ionized in the satellite's plasma sheath and accelerated radially outward. In this instrument, an electrostatic deflection system, which determines the charged particle direction of motion over a range of 100 degrees, routes particles to a retarding potential analyzer, which determines the energy of the ion stream, measuring particle energies from 0- to 100-electronvolts (eV). The directional discrimination of the Differential Ion Flux Probe will allow scientists to differentiate between the ionospheric ions flowing around the satellite from ions that are created in the satellite's plasma sheath and accelerated outward by the sheath's electric field.
The Soft Particle Energy Spectrometer instrument is a collection of five electrostatic analyzers that measure electron and ion energies from 1- to 10,000-eV. Three analyzer modules provide measurements at different locations on the surface of the satellite's hemispherical payload module. These sensors determine the potential of the satellite and the distribution of charged particles flowing to its surface. Two other Soft Particle Energy Spectrometer sensors, mounted with the Differential Ion Flux Probe on the end of the boom, measure ions and electrons flowing both inward and outward from the satellite. These measurements can be used to calculate the local potential of the plasma sheath.
This page contains excerpts from the brochure: "The First Mission of the Tethered Satellite System" developed by the Tethered Satellite System Project Office, NASA/Marshall Space Flight Center (MSFC), Huntsville, Alabama. Authors are C. Blake Powers, Charlotte Shea, and Tracy McMahan, all of the Essex Corporation.