Tuesday 1 September 2020

Orbiting Geophysical Observatory 1 satellite re-enters Earth's atmosphere.

The Orbiting Geophysical Observatory 1 satellite re-entered Earth's atmosphere on Saturday 29 August 2020, burning up in the atmosphere high above French Polynesia after 56 years in orbit about the Earth. The satellite, launched by NASA on 4 September 1964, was part of the Orbiting Geophysical Observatory Program, a group of six satellites designed to study the Earth's magnetosphere. It was intended to circle the Earth on a roughly equatorial orbit, with a perigee (closest point on its orbit to the Earth) of 281 km, and an apogee (furthest point of its orbit from the Earth) of 149 385 km, tilted at an angle of 31.2° to the Earth's equatorial plane. However over the course of its working life both it's altitude and its inclination grew, so that by April 1970 the satellite's orbit was tilted at an angle of 58.8° to the Earth's equatorial plane, and its perigee to 46 000. This causes a steady decrease in the quality of the data being recovered from the satellite, so that the last usable data was recieved in November 1969, and the satellite was completely abandoned in November 1971.

The Orbiting Geophysical Observatory 1 satellite, on 29 August 2020, a few hours before it re-entered the Earth's atmosphere. 30 second image of 2020 MF1 taken with the Elena Planetwave 17" Telescope at Ceccano in Italy. The satellite is the small point at the centre of the image, indicated by the white arrow, the longer lines are stars, their elongation being caused by the telescope tracking the asteroid over the length of the exposure. Gianluca Masi/Virtual Telescope.

Despite (or possibly due to) the problems the Orbiting Geophysical Observatory 1 satellite had with its orbit, it far outlived the other satellites in the program. The Orbiting Geophysical Observatory 3 and 5 satellites were launched on 7 June 1966 and March 1968, respectively, and were designed to follow similar orbits to Orbiting Geophysical Observatory 1; they fell back to Earth on 14 September 1981 and 2 July 2011. The Orbiting Geophysical Observatory 2, 4, and 6 satellites were launched onto lower, pole-crossing orbits on 14 October 1965, 28 July 1967, and 5 June 1969, and fell back to Earth on 17 September 1981, 16 August 1972, and 12 October 1979.

The Orbiting Geophysical Observatory 1 satellite. NASA.

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