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1974 February 5


Image: SL1203 is fired from Woomera at 01:10 hours local time, Tuesday 5 January 1974
(WRE\ Rapley)

Summary: SL1203 was an astronomy mission, launched from Woomera to study the southern skies. It carried (i) An MSSL soft X-ray detector system to search for background radiation and (ii) a University of California (Berkeley) instrument to carry out the first systematic search for EUV (Extreme Ultraviolet) objects in the southern sky. Good scientific results were obtained.

Testing at Woomera began in November 1973, but rare rainstorms and flash floods combined with technical issues delayed launch until well after Christmas.

The ten minute flight went to schedule, the vehicle reaching space after one and a half minutes:
Goldfinch ignition: 0 secs
Raven ignition: 6 secs             1.4 km
Despin: 1 min 17 secs   85 km
Nose cone jettison: 1 min 20 secs   95 km
Head release: 1 min 22 secs   98 km
ACU gas on: 1 min 26 secs  103 km
Apogee: 3 min 49 secs  197 km
Pneumatic bay jettison: 6 min 19 secs    93 km
Parachute bay deployment: 9 min 30 secs   3.5 km

Things started well, the new form of ACU (Attitude Control Unit) aligning itself with the Earth’s magnetic field in only nine seconds, and then carrying out four controlled rolls at about 1º per second, so the experiments scanned the chosen area of the sky. However, at +17 seconds MSSL detector 1 started to leak gas, and after 86 seconds the supply ran out and it stopped working. In addition, the detector 3 door failed to open, and the star- field camera film jammed because of a fault in the construction of the armoured take-up cassette.

On landing, the parachute system did not deploy correctly, the payload was badly damaged and the parachute torn. In addition, the dispersion of SL1203 was much greater than expected; the aiming point was 152 km (94 miles) down range, but the payload landed 49 km (30 miles) further away.

Results:  Overall, the flight was extremely successful, despite the complicated experiments and new technology being used. At least two scientific papers resulted.

The MSSL experiment produced state of the art X-ray astronomy results. It discovered an enhancement associated with Radio Loop IV and confirmed the existence of soft X-ray emission from Loop I. In addition, soft X-ray absorption by a dense ridge of neutral hydrogen lying approximately 200 parsec (61 light years) away in Hydra was observed. This latter result was of great importance since it provided the first positive evidence for the existence of strong soft X-ray emission from beyond the bulk of the galactic absorbing gas.

The NASA/Berkeley EUV experiment also produced good results, and discovered a new stellar EUV source near the South Equatorial Pole, only the fifth such source to be found, although the first by a systematic search rather than the observation of known soft X-ray sources*. It also appears to have been the first discovered in the southern hemisphere.

* Curiously, the first is also reported (Lampton 1976) to have been discovered with a grazing-incidence telescope during the Apollo-Soyuz mission in July 1975, a year later than SL1203!



launch site


Apogee km





05 Feb. 1974


Mag, Rav.6



Astronomy - X-ray background & EUV survey southern skies (proportional counters, EUV telescopes


(i)  'Britain's First Space Rocket' book: pages 474-478
(ii)  Rapley, Bell Burnell & Culhane (1976), ‘Observations of the Soft X-ray Diffuse Background’, also Henry, Bowyer, Rapley & Culhane (1976), ‘Direction of an Extreme-Ultraviolet Source in the Southern Sky’
(iii) Henry, Bowyer, Rapley & Culhane (1976), ‘Direction of an Extreme-Ultraviolet Source in the Southern Sky’, p.L29

                       © New Forest Electronics Tel. +44 (0) 1425 650089                 Issue 3.62    20 September 2017