|Mission type||Weather Satellite|
|Mission duration||38 days|
|Launch mass||305 kilograms (672 lb)|
|Power||350 W (peak)|
|Start of mission|
|Launch date||August 10, 1968, 22:33:00UTC|
|Rocket||Atlas SLV-3C Centaur-D|
|Launch site||Cape Canaveral LC-36A |
|End of mission|
|Decay date||October 17, 1968|
|Perigee altitude||185.99 kilometres (115.57 mi)|
|Apogee altitude||766.89 kilometres (476.52 mi)|
The objective of ATS-4 was to investigate the possibilities of a gravity gradient stabilization system (the method of stabilizing artificial satellites).
A total of four experiments were conducted during the mission:
The Atlas and Centaur stages performed satisfactorily and placed the Centaur/ATS-4 in an elliptical parking orbit, the Centaur stage, however, failed to re-ignite after a 61 minute coast. The failure was determined to be caused freezing of the hydrogen peroxide supply lines to the Centaur engines. High atmospheric drag due to the low altitude of the achieved orbit precipitated the orbital decay of the spacecraft, yet, still achieved good results in some of the experiments. The primary objective to put a spacecraft stabilized by gravity gradient in orbit was not reached. The satellite reentered the atmosphere on 17 October 1968.
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.