Explorer 39

 1968-066A

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The AD-C (Air Density Explorer C, Explorer XXXIX) satellite was launched from Vandenberg on 1968 Aug 8. The Scout delivered it into a 670 x 2538 km x 80.7 deg orbit, together with Explorer XL. Explorer XXXIX's beacon transmitted until 1971 Jun; it was reactivated on 1976 Feb 20. The satellite reentered on 1981 Jun 22.

The Injun satellite had a mass of 63 kg not counting the ADE. The ADE hardware had a total mass of 16 kg, 9.4 kg of which was the 3.66-m dia balloon satellite, made of Al foil and polyethylene-terephthalate plastic film. Attached to the balloon surface was a battery unit, a solar cell package, and a transmitter. The Al foil sphere had a small 0.01m equatorial gap turning the Al into an antenna.

The AD deployer consists of a container, a spearation mechanism, ejection bellows and an inflation bottle, for a total mass of 7 kg; this remained with the Injun satellite, giving it an orbital mass of 70 kg.

The AD/Injun pair was launched near solar max, to complement the earlier IQSY mission.

The Scout E-section payload adapter had a mass of 4.5 kg.

Debris detected in orbit had a slower decay rate than the balloon, and may be associated with Injun. Debris cataloged starting in 1994 was at an altitude consistent with some of the rest of the debris, suggesting that it separated from Injun in the 1960s or 1970s.

AD-C
Date	Time	Event	Orbit
1968 Aug 8	2012:00	Launch by Scout B S165C	V SLC5
	2013	Algol burnout T+1:16
	2013	Castor burn T+1:18
		T+1:56 Castor burnout
	2014	Antares burn T+2:00
	2014	Coast T+2:35
		T+10:03 Spinup
		T+10:04 Antares sep
	2022:08	T+10:08 FW4S burn
	2022:40	T+10:40 FW4S burnout
	2040:04	T+28:04 AD inflation and sep from Injun
	2110:03	T+58:03 Injun sep from FW4S
		Injun despin
		VLF antenna out
		Loop antenna out
			670 x 2538 x 80.7 (RAE)
1971 Jun		Deactivated
1976 Feb 20		Reactivated
1981 Jun 22		Reentered

Payload:

• Air density balloon (LaRC/Keating, SAO/Jacchia)

• Radio beacon

• Internal temperature sensor