The First Solar Observatories in Orbit

NASA missions to study Earth's closest star will join its most ambitious mission to study the sun. The importance of the Sun for all life on Earth makes the task even more important.

NASA'S Orbiting Solar Observatories(OSO) were a series of eight spacecraft launched by NASA between 1962 and 1975. The Ball Brothers Research Corporation (now Ball Aerospace) manufactured the first seven OSO spacecraft, and Hughes Space and Communications Company constructed OSO 8. The OSO series had two distinct sections, the wheel, and sail section. In the wheel section, the central mass of the spacecraft consisted of a single nine-sided “wheel” and three radial arms. The sail section was a semicircular “sail” over the hub of the wheel section. When the spacecraft was in orbit and operational, a first motor would torque against the spinning wheel section, allowing two instruments that are mounted in the bottom of the sail section and the solar panels installed on the face of the sail to keep it directed toward the Sun. It also contained the pitch control jets and the gas that powered them.

The OSO-1was launched on March 7, 1962 and added enormous amounts of data about the Sun that could not be observed from Earth. The second OSO spacecraft encountered a serious of issues when its solid-fueled Altair-2 third stage ignited. The third OSO also dealt the program a serious setback when the Delta rocket carrying it exploded shortly after the second stage burn on August 25, 1965. The replacement OSO-3 launched on a Delta Rocket from CCAFS LC-17A on March 8, 1967, and it stopped data transmission on November 10, 1969, and re-entered Earth’s atmosphere on April 4, 1982. OSO-4 (OSO D) was launched on a Delta Rocket on October 18, 1967, and began to suffer problems and was placed into standby mode in November of 1969. It failed permanently on December 7, 1971. OSO-5 (OSO F) was launched on a Delta C1 rocket on January 22, 1969 and operated until July of 1975. OSO-6 (OSO G) was launched on a Delta N rocket on August 9, 1969 and operated until January of 1972. OSO-7 (OSO H) was also manufactured by Ball Brothers. Its tape recorder failed in May 1973 and it re-entered on July 9, 1974. OSO-8 (OSO I) was manufactured by Hughes Space and Communications Company, based on a canceled follow-on to the Orbiting Solar Observatory program called the Advanced Orbiting Solar Observatory. Its wheel section was cylindrical, while the three radial arms remained. The sail section became much tall and more rectangular.

Sun is the source of almost all of the energy used by Earth’s surface to live, but the power within the Sun is billions of times greater. More distant stars bathe their planets in deadly radiation making it more critical for us to discover what distinguishes our Sun from these other stars, and to understand its evolution. It could also help us unlock the secrets of these other shining celestial bodies – and the worlds that orbit them. There are countless reasons for which NASA is sending the Parker Solar Probe to study the Sun and adding to the wealth of knowledge gained from the missions of its predecessors.