ESRO-4

 1972-092A

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The ESRO IV satellite was built by the UK firm Hawker Siddeley Dynamics (later part of British Aerospace) to study the ionosphere and solar particles. It carried experiments originally intended for the cancelled TD-2 program, and used the ESRO II structure. It was placed in a 254 x 1173 km orbit in Nov 1972.

Mass 115 kg. Cylinder with 4 deployable booms. Size is 0.76 m dia and 0.90m high. A cable restrains the booms and is severed after stage 4 separation. No yo-yo system is carried as the boom deploy reduces the spin rate to 70 rpm. Stage 4 empty is 47 kg, with 277 kg prop. (25 kg stage plus 7 kg Upper D section plus 14 kg E section). A 17 kg spin table remains with the third stage.

Some time zone confusion in different sources leads to launch dates of Nov 22 or Nov 23; analysis of TLE data confirms the Nov 22 date. Stage trajectories here are prelaunch; actual trajectory was lower.

ESRO IV
Date	Time	Event	Orbit
1972 Nov 22	0017:01	Launch by Scout D-1 S185C	V SLC 5
	0018:21	Algol burnout T+1:20 41.6 km 39.6 deg 1.400 km/s
	0018:24	Castor burn T+1:23 44.4 km 38.6 deg 1.379 km/s
	0019:04	Castor burnout T+2:03 93.7 km 31.4 deg 3.327 km/s
	0020:03	Heatshield eject T+3:02
	0020:04	Antares burn T+3:03 182.5 km 23.9 deg 3.065 km/s
	0020:38	Antares burnout T+3:37 219.8 km 8.2 deg 5.302 km/s
	0020:46	Coast T+3:45
	0023:01	Altair burn T+6:01 275.4 km 0.6 deg 5.204 km/s
	0023:36	Altair burnout T+6:35 275.0 km 0.0 deg 7.963 km/s
	0028:07	Stage 4 sep	99.0 254 x 1173 x 99.1
	0028:07	ESRO IV radial booms deploy T+11:06
	0028:15	T+11:14 axial booms deply and S80 NMS cover jettison (92C?)
1974 Apr 15		End of ops
1977 Nov 26	0900	Reentered

Payload:

• S80 Neutral mass spectrometer

• S103 Auroral and solar particles (MPE)

• S99 High energy proton and anlpha (SRON)

• S45 Ion probe; Langmuir probe (ne,Te) on one of three booms

• S94 Auroral electron pitch angle distribution