TheOrbiting Solar Observatory (abbreviatedOSO) Program was the name of a series of Americanspace telescopes primarily intended to study theSun, though they also included important non-solar experiments. Eight were launched successfully intolow Earth orbit byNASA between 1962 and 1975 usingDelta rockets. Their primary mission was to observe an 11-yearsun spot cycle inUV andX-ray spectra.
The initial seven (OSO 1–7) were built byBall Aerospace, then known as Ball Brothers Research Corporation (BBRC), inBoulder, Colorado.[1] OSO 8 was built by Hughes Space and Communications Company, inCulver City, California.
Nancy Roman oversaw the development of the Orbiting Solar Observatory program from 1961 to 1963.[2]
The basic design of the entire series featured a rotating section, the "Wheel", to provide gyroscopic stability. A second section, the "Sail", was driven electrically against the Wheel's rotation, and stabilized to point at the Sun. The Sail carried pointed solar instruments, and also the array of solar photovoltaic cells which powered the spacecraft.The critical bearing between the Wheel and the Sail was a major feature of the design, as it had to operate smoothly for months in the hard vacuum of space without normal lubrication. It also carried both the power from the Sail and the data from the pointed solar instruments to the Wheel, where most of the spacecraft functions were located.Additional science instruments could also be located in the Wheel, generally looking out on a rotating radius vector which scanned the sky, and also across the Sun, every few seconds.
OSO 1 (OSO A) was launched on March 7, 1962.[3]
OSO B suffered an incident during integration and checkout activities on April 14, 1964. The satellite was inside the Spin Test Facility atCape Canaveral attached to the third stage of itsDelta C booster when a technician accidentally ignited the booster through static electricity. The third-stage motor activated, launched itself and the satellite into the roof, and ricocheted into a corner of the facility until burning out. Three technicians were burned to death. The satellite, although damaged, was able to be repaired using a combination of prototype parts, spare flight parts and new components. It was launched ten months later on February 3, 1965 and was designatedOSO 2 (OSO B2) on orbit.[4][3]
OSO C never made it to orbit. Liftoff took place on August 25, 1965 and all went well through the second stage burn.[3] During the coasting phase prior to third stage separation, its rocket motor ignited prematurely. This registered on ground readouts as an attitude disturbance followed by loss of second stagetelemetry, and although the third stage managed to separate itself, it suffered from an 18% drop in thrust. The OSO spacecraft could not attain orbital velocity and instead fell back into the atmosphere and burned up. The failure was suspected to have been caused by a modification to the igniter mechanism in the third stage after some minor technical difficulties experienced on the previous Delta C launch (TIROS 10 on July 2).[5]
OSO 3 (OSO E1) was launched on March 8, 1967.[3]
Eight OSO telescopes were launched from 1962 to 1975.
| Designation | Launch Date | Re-entry date | Notable results |
|---|---|---|---|
| OSO 1 (OSO A) | 7 March 1962 | 7 October 1981[6] | |
| OSO 2 (OSO B2) | 3 February 1965 | 8 August 1989[7] | |
| OSO 3 (OSO E1) | 8 March 1967 | 4 April 1982[8] | Observedsolar flares from the Sun, as well as a flare fromScorpius X-1[9][10] |
| OSO 4 (OSO D) | 18 October 1967 | 14 June 1982[11] | |
| OSO 5 (OSO F) | 22 January 1969 | 2 April 1984[12] | Measured diffuse backgroundX-ray radiation from 14-200 keV[13][14] |
| OSO 6 (OSO G) | 9 August 1969 | 7 March 1981[15] | Observed three instances of hard X-ray coincidences withgamma ray bursts.[16] |
| OSO 7 (OSO H) | 29 September 1971 | 8 July 1974[17] | Observed solar flares in the gamma ray spectrum. Collected data allowed for identification ofVela X-1 as aHigh-mass X-ray binary.[18][19] |
| OSO 8 (OSO I) | 21 June 1975 | 8 July 1986[20] | Found an ironemission line in the X-rayspectrum of agalaxy cluster.[21] |
TheAdvanced Orbiting Solar Observatory (AOSO) program was developed in the mid 1960s as a more advanced version of the OSO series. Conceived as a polar-orbiting satellite system, these spacecraft would continuously monitor the Sun and surrounding environment with detectors and electronic imaging ranging from x-rays to visual light. Due to budget constraints, the AOSO program was cancelled in 1965. Instead, it was replaced by the OSO-I,OSO-J andOSO-K satellites. Only OSO-I, which became OSO 8, was ever launched.[22]
Another satellite using the Orbiting Solar Observatory platform was developed and launched: theSolwind satellite. It was launched February 24, 1979. It was operated by theDoDSpace Test Program. It was destroyed September 13, 1985 on anASAT missile test.
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