OSO 3
The third Orbiting Solar Observatory, OSO 3, showing its "Sail" (upper), carrying solar experiments pointed at the Sun, and its rotating "Wheel" (lower), carrying two sky-scanning survey instruments: the UCSD hard X-ray experiment, and the MIT gamma-ray telescope | |
| Mission type | Solar physics |
|---|---|
| Operator | NASA |
| COSPAR ID | 1967-020A |
| SATCAT no. | 02703 |
| Mission duration | 2 years, 8 months |
| Spacecraft properties | |
| Manufacturer | BBRC |
| Launch mass | 281 kilograms (619 lb) |
| Start of mission | |
| Launch date | March 8, 1967, 16:19:00 UTC |
| Rocket | Delta C |
| Launch site | Cape Canaveral LC-17A |
| End of mission | |
| Last contact | November 10, 1969 |
| Decay date | April 4, 1982 |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Low Earth |
| Eccentricity | 0.002164 |
| Perigee altitude | 534 kilometers (332 mi) |
| Apogee altitude | 564 kilometers (350 mi) |
| Inclination | 32.87 degrees |
| Period | 95.53 minutes |
| Mean motion | 15.07 |
| Epoch | May 8, 1967, 11:19:00 UTC |
OSO 3 (Orbiting Solar Observatory 3), or Third Orbiting Solar Observatory (known as OSO E2 before launch) was launched on March 8, 1967, into a nearly circular orbit of mean altitude 550 km, inclined at 33° to the equatorial plane. Its on-board tape recorder failed on June 28, 1968, allowing only the acquisition of sparse real-time data during station passes thereafter; the last data were received on November 10, 1969. OSO 3 reentered the Earth's atmosphere and burned up on April 4, 1982.
Like all of the early Orbiting Solar Observatory (OSO) series satellites, it had two major segments: one, the "Sail", was stabilized to face the Sun, and carried both solar panels and Sun-pointing experiments for solar physics. The other, "Wheel" section, rotated to provide overall gyroscopic stability and also carried sky-scanning instruments that swept the sky as the wheel turned, approximately every 2 seconds. OSO-8, the final spacecraft in this series, had 3-axis pointing.