 ATS-4 | |
| Mission type | Weather Satellite |
|---|---|
| Operator | NASA |
| COSPAR ID | 1968-068A |
| SATCATno. | 03344 |
| Mission duration | 38 days |
| Spacecraft properties | |
| Bus | HS-306 |
| Manufacturer | Hughes Aircraft |
| Launch mass | 305 kilograms (672 lb)[1] |
| Power | 350 W (peak) |
| Start of mission | |
| Launch date | August 10, 1968, 22:33:00 (1968-08-10UTC22:33Z) UTC |
| Rocket | Atlas SLV-3C Centaur-D (AC-17) |
| Launch site | Cape Canaveral[1]LC-36A[2] |
| End of mission | |
| Disposal | August 10, 1968 |
| Decay date | October 17, 1968 (1968-10-18)[3] |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | LEO |
| Eccentricity | 0.042372[2] |
| Perigee altitude | 185.99 kilometres (115.57 mi)[2] |
| Apogee altitude | 766.89 kilometres (476.52 mi)[2] |
| Inclination | 29.141º[2] |
| Period | 94.131 minutes[2] |
ATS-4 (Applications Technology Satellite) also known asATS-D was acommunications satellite launched byNASA on August 10, 1968[3] fromCape Canaveral through anAtlas-Centaur (AC-17) rocket.[1][2]
The objective of ATS-4 was to investigate the possibilities of agravity gradient stabilization system (the method of stabilizing artificial satellites).[3]
The satellite has a cylindrical shape with a 142-centimetre (56 in) diameter and 183-centimetre (72 in) height (about 360 centimetres (140 in) considering the motor cover) with the surface covered bysolar panels that generated a maximum of 350 W of power,[4] and stabilized bygravity gradient. It was based on theHughes Aircraft HS-306bus.[5]
A total of four experiments were conducted during the mission:
The Atlas and Centaur stages performed satisfactorily and placed theCentaur/ATS-4 in anellipticalparking orbit. However the Centaur stage failed to re-ignite after a 61-minute coast. The failure was determined to be freezing of thehydrogen peroxide supply lines to the Centaur engines.[2]
Highatmospheric drag due to the low altitude of the achieved orbit (186 kmperigee) precipitated theorbital decay of the spacecraft. ATS-4 still achieved good results in some of the experiments, but the primary objective of achieving gravity gradient stabilization of a satellite was not reached.
ATS-4 reentered the atmosphere on 17 October 1968.[3]
ATS-4 was to investigate the possibilities of a gravity gradient stabilization system. A launch vehicle failure stranded ATS-4 in a much lower than planned orbit, making the satellite nearly useless. Despite this, NASA engineers successfully turned on several of the experiments to collect as much information as possible during the craft's short life. The low orbit and resulting atmospheric drag caused ATS-4 to re-enter Earth's atmosphere and break apart on Oct. 17, 1968.