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Explorer 36
Explorer 36 (also called GEOS 2 or GEOS B, acronym for Geodetic Earth Orbiting Satellite) was a NASA satellite launched as part of the Explorer program, being the second of the two satellites GEOS. Explorer 36 was launched on 11 January 1968 from Vandenberg Air Force Base, with Thor-Delta E1 launch vehicle.
Explorer 36 was a gravity-gradient stabilized, solar cell powered spacecraft that carried electronic and geodetic instrumentation. The spacecraft's thermal control system was notable for the first non-experimental use of a heat pipe in a spacecraft.
The geodetic instrumentation systems included:
Non-geodetic systems included a laser detector and a Minitrack interferometer beacon. The objectives of the spacecraft were to optimize optical station visibility periods and to provide complementary data for inclination-dependent terms established by the Explorer 29 (GEOS 1) gravimetric studies. The spacecraft was placed into a retrograde orbit to accomplish these objectives. Operational problems occurred in the main power system, optical beacon flash system, and the spacecraft clock, and adjustments in scheduling resulted in nominal operations.
The C-band radar system was used for experimental range radar calibration and data recording to determine the accuracy of the system for geometric and gravimetric investigations. For redundancy, two transponders, each operating on 5690-MHz (RCVR) and 765-MHz (XMTR) were carried on the spacecraft. One transponder had a 5-ms interval time delay, and the other had a near-zero internal delay that allowed for real-time identification by the C-band participants. The transponders were operated on a select-call basis to conserve spacecraft power. A C-band passive reflector was used in conjunction with the transponders for precise calibration of the internal time delay and to provide passive C-band tracking capabilities.
Laser corner reflectors, composed of 322 fused quartz cubes with silvered reflecting surfaces, were used for determining the spacecraft range and angle. The cubes, which were mounted on fiberglass panels on the bottom rim of the spacecraft, provided a total reflecting area of 0.18 m2. The reflectors conserved the narrow beamwidth of incoming light and provided a maximum signal to the ground almost exactly to where it originated. Fifty percent of the light that struck the prism area at a 90° angle was reflected within a beam of 20-arc-seconds. Reflected light received by ground telescopes was amplified by a photomultiplier tube that converted the optical impulse to an electrical signal. The time required for the beam to return to Earth was recorded by a digital counter. The reflected laser pulse was also photographed against the stellar background, and the total time traveled by the light pulses was considered in the optical laser tracking system. Laser tracking was the responsibility of Air Force Research Laboratory (AFCRL), Smithsonian Astrophysical Observatory (SAO), GSFC Optical Research, and international laser stations.
This instrument consisted of an uniaxial fluxgate magnetometer oriented perpendicular to the spacecraft orbit plane. Although the principal function of the magnetometer was to serve as an attitude sensor, a very limited amount of scientifically useful data on fluctuations in the range 0.03 to 3.0 cps were obtained through use of a filter.
The Minitrack beacon radiated on 136-MHz and was modulated with telemetry data. The minitrack interferometer tracking system data were used in combination with the Goddard Range and Range Rate (GRARR) system data to establish the Explorer 36 orbit and to compute operational predictions. The minitrack stations also participated with other stations in mutual visibility events for tracking systems comparison experiments.
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Explorer 36 AI simulator
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Explorer 36
Explorer 36 (also called GEOS 2 or GEOS B, acronym for Geodetic Earth Orbiting Satellite) was a NASA satellite launched as part of the Explorer program, being the second of the two satellites GEOS. Explorer 36 was launched on 11 January 1968 from Vandenberg Air Force Base, with Thor-Delta E1 launch vehicle.
Explorer 36 was a gravity-gradient stabilized, solar cell powered spacecraft that carried electronic and geodetic instrumentation. The spacecraft's thermal control system was notable for the first non-experimental use of a heat pipe in a spacecraft.
The geodetic instrumentation systems included:
Non-geodetic systems included a laser detector and a Minitrack interferometer beacon. The objectives of the spacecraft were to optimize optical station visibility periods and to provide complementary data for inclination-dependent terms established by the Explorer 29 (GEOS 1) gravimetric studies. The spacecraft was placed into a retrograde orbit to accomplish these objectives. Operational problems occurred in the main power system, optical beacon flash system, and the spacecraft clock, and adjustments in scheduling resulted in nominal operations.
The C-band radar system was used for experimental range radar calibration and data recording to determine the accuracy of the system for geometric and gravimetric investigations. For redundancy, two transponders, each operating on 5690-MHz (RCVR) and 765-MHz (XMTR) were carried on the spacecraft. One transponder had a 5-ms interval time delay, and the other had a near-zero internal delay that allowed for real-time identification by the C-band participants. The transponders were operated on a select-call basis to conserve spacecraft power. A C-band passive reflector was used in conjunction with the transponders for precise calibration of the internal time delay and to provide passive C-band tracking capabilities.
Laser corner reflectors, composed of 322 fused quartz cubes with silvered reflecting surfaces, were used for determining the spacecraft range and angle. The cubes, which were mounted on fiberglass panels on the bottom rim of the spacecraft, provided a total reflecting area of 0.18 m2. The reflectors conserved the narrow beamwidth of incoming light and provided a maximum signal to the ground almost exactly to where it originated. Fifty percent of the light that struck the prism area at a 90° angle was reflected within a beam of 20-arc-seconds. Reflected light received by ground telescopes was amplified by a photomultiplier tube that converted the optical impulse to an electrical signal. The time required for the beam to return to Earth was recorded by a digital counter. The reflected laser pulse was also photographed against the stellar background, and the total time traveled by the light pulses was considered in the optical laser tracking system. Laser tracking was the responsibility of Air Force Research Laboratory (AFCRL), Smithsonian Astrophysical Observatory (SAO), GSFC Optical Research, and international laser stations.
This instrument consisted of an uniaxial fluxgate magnetometer oriented perpendicular to the spacecraft orbit plane. Although the principal function of the magnetometer was to serve as an attitude sensor, a very limited amount of scientifically useful data on fluctuations in the range 0.03 to 3.0 cps were obtained through use of a filter.
The Minitrack beacon radiated on 136-MHz and was modulated with telemetry data. The minitrack interferometer tracking system data were used in combination with the Goddard Range and Range Rate (GRARR) system data to establish the Explorer 36 orbit and to compute operational predictions. The minitrack stations also participated with other stations in mutual visibility events for tracking systems comparison experiments.