Helios 1

  1974-097A

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The Helios solar probes were a joint project between DFVLR and NASA, which provided the Titan Centaur launch vehicle.  Helios 1 was launched on 1974 Dec 10 by Titan IIIE Centaur from Cape Canaveral's Launch Complex 41. Two Centaur burns placed the Helios probe in solar orbit. The Centaur TC-2 stage then made two retrograde test burns, which happened to leave it in an orbit bound to the Earth - it thus became the first object known to have returned to Earth orbit from a solar orbit trajectory with the possible exception of Apollo lunar spacecraft. NORAD cataloged two objects in a 1765 x 157261 km x 31.8 deg orbit; object D, the second object, may be a duplicate of the first or may represent some kind of debris from the Centaur after venting. However, the name of the object was later changed to 'Helios 1 debris' and with its elements marked in the Satellite Situation Report as 'heliocentric orbit', it may be the Star 37E tumble weight.

Helios 1
Date	Time	Event	Orbit
1974 Dec 10	0711:01	Launch
		T+1:40 Forward bearing reactor sep
		T+1:51 Stage 1 MES
	0713:05	T+2:04 SRM sep
		T+4:18 Stage 1 MECO
	0715	T+4:19 Titan stage 1 sep
	0715	T+4:19 Stage 2 MES
	0716	T+5:18 Fairing
	0718:50	T+7:49 St 2 MECO 165 km 7.01 km/s
	0718:53	T+7:52 Titan stage 2 sep	-1950? x 165 x 29.9
	0719:04	T+8:03 Centaur TC-2 MES1, 100.8s
	0720:42	T+9:44 Centaur TC-2 MECO1, start 21.9 min coast
	0726?	Stage 2 reentry
	0742:40	T+31:39 Centaur TC-2 MES2, 276s,
	0747:14	T+36:13 Centaur MECO-2 255 km?
		T+37:23 Spinup
	0748:26	T+37:25 Centaur TC-2 sep from Helios 1/Star 37
		Clamp band halves separate
	0748:26	T+37:25 TC-2 retro
	0749:06	T+38:05.76 Star 37E burn, 44.90s (action time 43.6s)
	0749:51	T+38:50.66 Star 37E burnout 528 km	289 x -21954 x 29.80
		Payload clamp band
	0751:02	T+40:01 Star 37E sep	Solar orbit 180d, 0.30958 x 1.0 AU x 0.016
	0751:06	T+40:05 Yo deploy
	1156	Helios/Star 37 pass EL1:4
	1654	Centaur clamp pass EL1:4
1974 Dec 12	0330?	Helios/Star 37 exit Earth sphere (L1)
1974 Dec 15	1200?	Centaur clamp band exit Earth sphere
1975 Feb 15	0915	Perihelion, 0.30AU
1976 Mar 29		Perihelion 3
1976 Jul 2		Aphelion 3
1982		Still operating

Payload:

• E1 Solar wind plasma expt (MPE/Rosenbauer)

• E2 Fluxgate magnetometer (TU Braunschweig/Musmann)

• E3 Fluxgate magnetometer (GSFC/Ness)

• E4 Search coil magnetometer (Braunschweig/Dehmei)

• E5 32 m antenna for plasm and radiowave expt, 50 kHz-2 MHz (Iowa/Gurnett)

• E6 Cosmic ray expt (Kiel/Kunow)

• E7 Cosmic ray expt (GSFC/Trainor)

• E8 Electron detector (MPIA-Lindau/Keppler)

• E9 Zodiacal light photometer (LSW-Heidelberg/Leinert)