Environmental Research Satellite

33 ERS satellites in six different series were launched between 1962 and 1971,[1] conducting scientific research and serving as test beds to investigate the reliability of new spacecraft components.

1 was developed by Space Technology Laboratories, a subdivision of TRW Inc., as an inexpensive, miniaturized "off-the-shelf" satellite that customers could use to perform simple experiments in orbit.

1 was a regular tetrahedron measuring 16 cm (6.3 in) on a side, each face mounted with sufficient solar cells to operate the experiments and the telemetry system when the satellite was in the sun.

Transmission of data was constant at that time as the spacecraft included neither internal battery nor command system.

[3] A transistor-based system provided eight channels of data: five for experiments, two for telemetry calibration, and one for the spacecraft temperature.

1 satellites were ultimately produced, designed to research radiation and micrometeoroid flux in Earth orbit.

While protective covers did not affect n-on-p degradation, they were shown to be helpful for the more sensitive p-on-n cells.

Spinning once every six seconds, the satellite measured electron and proton levels in the Van Allen Belts with omni-directional radiation detectors—a scintillation counter and a solid-state detector.

[17][14][a] The onboard transmitter, with a power of 100 mW could only reach ground stations when ERS 13 was within 40,280 km (25,030 mi) of Earth.

Five were produced: ORS-1 and ORS-2 (ERS-15 through ERS-16), which carried out cold welding experiments in space on a variety of metal samples, and ERS-23 through ERS-25, classified satellites whose flights may have been cancelled.

Approximately 1500 hours of data were collected by the ERS 17's five radiation detectors until November 3, 1965, when the transmitter ceased.

[24][26] Though this was much shorter than the planned lifespan of one year,[27] the satellite had collected a useful data set within the first four weeks of operation.

[24] In addition to returning basic scientific data, as well as helping to refine the Vela design by a better understanding of the radiation hazard the satellite series would endure, ERS 17 also monitored for the telltale increase of electron fluxes in the event of nuclear detonations in near space.

[30] These were very small satellites launched pick-a-back with primary payloads since 1962—a natural fit under the Orbiting Vehicle umbrella.