THE SHUTTLE POTENTIAL AND RETURN ELECTRON EXPERIMENT (SPREE)

The Shuttle Potential and Return Electron Experiment (SPREE) was desig ned and fabricated for flight as part of the joint NASA/Agenzia Spazia le Italiana Tethered Satellite System (TSS-1) mission. The SPREE is a complex instrument package designed to measure ion and electron partic le flux and wave-particle interactions. The SPREE flight hardware cons ists of two multiangular electrostatic analyzer units, two rotary tabl es, a data processing unit, a particle correlator experiment, and two data recording units. The electrostatic analyzers measure both electro ns and ions, in an energy range from 10 eV to 10 keV and simultaneousl y over an angular fan of (100 x 10) degrees. These units are mounted o n the rotary tables to provide a 2pi steradian field of view out of th e Orbiter's payload bay. To assess negative charging of the Orbiter wi th respect to the ambient plasma, ion data from the analyzers are proc essed real time by an on-board algorithm operating within the data pro cessing unit. The particle correlator experiment determines wave-parti cle interactions in the frequency range 0-10 MHz for electrons and fro m 0-10 kHz for ions. SPREE operated successfully throughout the TSS-1 mission. Examples of the data returned by the SPREE are shown.