Mission Overview

The Space Test Program (STP) P78-1 mission was designed to obtain scientific data from earth and sun-oriented experiments. The spacecraft was sun-oriented and had its spin axis perpendicular to both the orbital plane and the satellite-sun line. The instrumentation consisted of (1) a gamma-ray spectrometer and particle detectors, (2) a white-light coronagraph and an extreme-ultraviolet heliograph, (3) a solar X-ray spectrometer and spectroheliograph, (4) an extreme-ultraviolet spectrometer, (5) a high-latitude particle spectrometer, (6) an X-ray monitor, and (7) a preliminary aerosol monitor.

Launch Date: 1979-02-24 at 08:20:00 UTC
Launch Vehicle: Atlas
Launch Site: Vandenberg AFB, United States
Decay Date: 1992-07-20
Trajectory Details
Type: Orbiter
Central Body: Earth
Epoch start: 1979-02-24 08:20:00 UTC
Orbital Parameters
Periapsis 560.0 km
Apoapsis 600.0 km
Period 96.30000305175781 minutes
Inclination 97.9000015258789°
Eccentricity 0.0028719999827444553


Gamma-Ray Spectrometer

This investigation used gamma-ray spectrometers to measure the distribution of gamma-ray sources and the characteristics of energetic particle fluxes at low altitudes. The instrument consisted of twelve independent spectrometers of three different types. There were two germanium spectrometers, two CsI/plastic Phoswich spectrometers, and an array of eight CdTe spectrometers. Each germanium spectrometer consisted of a large (85-cc) high-purity intrinsic germanium detector which was shielded with a NaI anticoincidence scintillator and cooled by a mechanical refrigerator. Each germanium detector had a conical FOV of 45-deg half-angle and a 15-sq-cm front area, and it measured energy loss from 40 keV to 2.5 MeV in 4096 channels. A factor-of-3 gain change allowed the range to change to 0.12 to 7.5 MeV. The initial energy resolution was 3.5 keV at 1 MeV, but due to radiation damage and temperature cycling caused by the necessity to turn off the refrigerator for power conservation, the resolution degraded to about 40 keV at the 0.511-MeV line. The Phoswich spectrometers were 10.16-cm diameter disks of 1.27-cm thickness; they measured energy loss from 40 keV to 2.5 MeV in 256 channels. The FOVs of the CdTe spectrometers were fan-shaped in two dimensions with opening angles of 90 deg and 10 deg and had the 10-deg openings equally spaced in the S/C plane of rotation. The energy loss range was 20 to 200 keV in six channels.

Solar Wind Monitor

This investigation used a white-light coronagraph and an extreme ultraviolet heliograph to monitor the sun's inner and outer corona. The purpose of the investigation was to determine the character of the plasma outflow at the source of the solar wind. The investigation also measured the form and structure of solar flares, coronal holes, and Alfven waves. Due to background light problems, the EUV heliograph data were completely compromised.

Solar X-Ray Spectrometer

This investigation was composed of four parts: Solex, Solflex, Monex, and Magmap. The objective of these four experiments was the study of solar flares and active regions. Solex obtained spectra in the 3- to 25-A wavelength interval while pointed at a specific solar region, as well as maps of the sun in individual X-ray spectral lines using multigrid collimators and Bragg crystal spectrometers. Solflex obtained flare spectra in four narrow-wavelength bands between 1.8 and 8.6 A using uncollimated Bragg crystal spectrometers. Monex recorded full solar-disk intensity with 32-ms time resolution from 0.1 to 12 A using uncollimated proportional counters. Magmap obtained full-disk solar maps from 8 to 12 A using filtered collimated proportional counters.

Extreme Ultraviolet Spectrometer

This investigation used an extreme-ultraviolet spectrometer to measure airglow radiation in the upper atmosphere. The instrument had a 6- by 6-deg field of view and measured spectra in a selected 600-A bandwidth, with 5-A resolution, within the 200- to 1400-A range.

High Latitude Particle Spectrometer

This investigation used two sets of dual electrostatic analyzers at right angles to acquire electron data in high-latitude auroral zones, primarily during magnetic storm and substorm periods. One analyzer in each set swept through the energy range 50 to 1000 eV, while the other analyzer swept from 1 to 20 keV simultaneously. The total energy range, 0.05 to 20 keV, was divided into 16 channels.

X-Ray Monitor

This investigation used an X-ray monitor to determine the frequency and location of short-lived X-ray bursts from space. It provided a low-resolution mapping capability for auroral X-ray emission.

Preliminary Aerosol Monitor

This investigation used an aerosol-monitoring instrument to measure the concentration and vertical distribution of aerosols and ozone in the earth's stratosphere.