Analysis of Proseds bare-tether performance

NASA's tether experiment ProSEDS will be placed in orbit on board a Delta-II rocket in early 2003. ProSEDS will test bare-tether electron collection, deorbiting of the rocket second stage, and the system dynamic stability. ProSEDS performance will vary both because ambient conditions change along the orbit and because tether-circuit parameters follow a step by step sequence in the current operating cycle. In this work we discuss how measurements of tether current and bias, plasma density, and deorbiting rate can be used to check the OML law for current collection. We review circuit bulk elements; characteristic lengths and energies that determine collection (tether radius, electron thermal gyroradius and Debye length, particle temperatures, tether bias, ion ram energy); and lengths determining current and bias profiles along the tether (extent of magnetic self-field, a length gauging ohmic versus collection impedances, tether length). The analysis serves the purpose of estimating ProSEDS behavior in orbit and fostering our ability for extrapolating ProSEDS flight data to different tether and environmental conditions

Simulation of the Dynamics of a Short Tethered Satellite System

This study investigates the dynamics of a short tethered satellite system composed of two satellites joined by a ten-meter tether. Despite the many studies in the literature regarding tethered satellites and their dynamics, none that specifically concern “short” tethers have been located to date. Equations of motion are derived and numerically integrated to produce the tether tension, system attitude, orbit, and libration characteristics. Techniques have been implemented which add corrections to the integrated states and help reduce longterm simulation errors. Also considered are the effects of perturbations due to the Earth\u27s geopotential, solar and lunar gravity, aerodynamic drag and solar radiation pressure