D2LEP2>LAPI_Corrected Electron Counts and Flux from Power Supply 2

DE-2, LAPI_Corrected Electron Counts and Flux from Power Supply 2 IDFS format

The DE-2 spacecraft (low-altitude mission) complemented the high-altitude mission DE-1and was placed into an orbit with a perigee sufficiently low to permit measurements of neutral composition, temperature, and wind. The apogee was high enough to permit measurements above the interaction regions of suprathermal ions, and also plasma flow measurements at the feet of the magnetospheric field lines. The general form of the spacecraft was a short polygon 137 cm in diameter and 115 cm high. The triaxial antennas were 23 m tip-to-tip. One 6-m boom was provided for remote measurements. The spacecraft weight was 403 kg. Power was supplied by a solar cell array, which charged two 6-ampere-hour nickel-cadmium batteries. The spacecraft was three-axis stabilized with the yaw axis aligned toward the center of the earth to within 1 deg. The spin axis was normal to the orbit plane within 1 deg with a spin rate of one revolution per orbit. A single-axis scan platform was included in order to mount the low-altitude plasma instrument (81-070B-08). The platform rotated about the spin axis. A pulse code modulation telemetry data system was used that operated in real time or in a tape-recorder mode. Data were acquired on a science-problem-oriented basis, with closely coordinated operations of the various instruments, both satellites, and supportive experiments. Measurements were temporarily stored on tape recorders before transmission at an 8:1 playback-to-record ratio. Since commands were also stored in a command memory unit, spacecraft operations were not real time. Additional details can be found in R. A. Hoffman et al., Space Sci. Instrum., v. 5, n. 4, p. 349, 1981. DE-2 reentered the atmosphere on February 19, 1983. 
The Low-Altitude Plasma Instrument (LAPI) provided high-resolution velocity space measurements of positive ions and electrons from 5 eV to 32 keV. The two Geiger-Mueller counter tubes (0 and 90 deg) measured trapped electrons and precipitating electrons above 35 keV as integral number flux. Pitch angle measurements covered the full 180 deg range. Data from this investigation and supporting measurements were used to study 
(1) the identification and intensities of Birkeland currents, 
(2) auroral particle source regions and acceleration mechanisms, 
(3) the existence and role of E parallel to B, 
(4) sources and effects of polar cap particle fluxes, 
(5) the transport of plasma within and through the magnetospheric cusp, 
(6) dynamic configurations of high-latitude flux tubes, 
(7) loss-cone effects of wave-particle interactions, 
(8) hot-cold plasma interactions, 
(9) ionospheric effects of particle precipitation, and 
(10) plasma convection at high altitudes. 
The instrument contained an array of 15 parabolic electrostatic analyzers of the ISIS 2 type, each with an electron channel and an ion channel, in order to obtain detailed pitch-angle distributions as a function of energy. Two Geiger-Mueller counters were mounted on the scan platform. The basic mode of operation provided a 32-point energy spectrum in the range 5 eV to 32 kev every second. The voltages on the electrostatic analyzers were programmable to allow for greater space/time resolution over limited portions of the energy and angular distributions. The instrument was mounted on a one-axis scan platform controlled by a magnetometer, whose purpose was to maintain the detector array, which spanned 180 deg, at a nearly constant angle to the magnetic field. Additional details are found in J. D. Winningham et al., Space Sci. Instrum., v. 5, n. 4, p. 465, 1981. From March 16, 1982 to April 4, 1982 the instrument was turned off for corrective action. 
The Instrument Data File Set. URL http://www.idfs.org 