The Orbiting Geophysical Observatory 6 (OGO 6) was a large observatory
instrumented with 26 experiments designed to study the various
interrelationships between, and latitudinal distributions of,
... high-altitude
atmospheric parameters during a period of increased solar activity. The main
body of the spacecraft was attitude controlled by means of horizon scanners and
gas jets so that its orientation was maintained constant with respect to the
earth and the sun. The solar panels rotated on a horizontal axis extending
transversely through the main body of the spacecraft. The rotation of the
panels was activated by sun sensors so that the panels received maximum
sunlight. Seven experiments were mounted on the solar panels (the SOEP
package). An additional axis, oriented vertically across the front of the main
body, carried seven experiments (the OPEP package). Nominally, these sensors
observed in a forward direction in the orbital plane of the satellite. The
sensors could be rotated more than 90 deg relative to the nominal observing
position and more than 90 deg between the upper and lower OPEP groups mounted
on either end of this axis. On June 22, 1969, the spacecraft potential dropped
significantly during sunlight operation and remained so during subsequent
sunlight operation. This unexplained shift affected seven experiments which
made measurements dependent upon knowledge of the spacecraft plasma sheath.
During October 1969, a string of solar cells failed, but the only effect of the
decreased power was to cause two experiments to change their mode of operation.
Also during October 1969, a combination of manual and automatic attitude
control was initiated, which extended the control gas lifetime of the attitude
control system. In August 1970, tape recorder (TR) no. 1 operation degraded, so
all recorded data were subsequently taken with TR no. 2. By September 1970,
power and equipment degradation left 14 experiments operating normally, 3
partially, and 9 off. From October 14, 1970, TR no. 2 was used only on
Wednesdays (world days) to conserve power and extend TR operation. In June
1971, the number of 'on' experiments decreased from 13 to 7, and on June 28,
1971, the spacecraft was placed in a spin-stabilized mode about the yaw (Z)
axis and turned off due to difficulties with spacecraft power. OGO 6 was turned
on again from October 10, 1971, through March 1972, for operation of experiment
25 by The Radio Research Laboratory, Japan.
[Summary provided by NASA.] 
