High Energy Astrophysics Group

OSO-7

Orbiting Solar Observatory-7

Cosmic X-ray Experiment

Detector | Electronics | Particle Monitors | Response | Background

The 7-bit PHA and 12-bit clock gave energy and time of arrival of each x-ray event to hit the central detector. The arrival direction of each event was calculated from the time and the spacecraft orientation data. The energy information was pseudo-logrithmically compressed into single channels of 4 keV width from 0--100 keV, double channels of 8 keV width from 100--200 keV and quintuple channels of 20 keV width from 200--500 keV.

Besides the sequence of x-ray events, the electronics sub-commutated counting rates and housekeeping information. The central detector and shield counter rates were also output every 15.36 s. Finally, the central detector and shield counter upper and lower threshold rates were sampled each for about 1/4 of the 15.36 s time intervals. From these rates one could determine the overall performance of the instrument and could properly normalize the intensity of fluxes from x-ray sources, since the telemetry limits did not permit full information on all events to be preserved.

Five commands gave control over the instrument. The central detector high voltage could be stepped to any of eight levels or reset to the first level. The signal used to determine aspect could be selected in three ways: solar eye during orbit day and gyro during orbit night; solar eye during the day and magnetometer during the night; or gyro for both. Finally, the shield counter high voltage could be stepped once and was reset by the aspect mode reset.

OSO-7 Information

Mission Objectives
Spacecraft
Cosmic X--ray Experiment
Solar X--ray Experiment
Results
Publication