[BAA 00444] UNUSUAL ROCKET FUEL DUMP SIGHTED

[Rick]

BAA electronic bulletin No. 00444 -- http://www.britastro.org/
Bulletin transmitted on  Mon Oct 19 19:17:38 BST 2009
(c) 2009 British Astronomical Association

UNUSUAL ROCKET FUEL DUMP SIGHTED

A Centaur rocket caused a minor sensation on Sunday night, October 18, when it flew over Europe and dumped a load of surplus propellant. On its second orbit of Earth following launch earlier on Sunday afternoon, the Centaur rocket had fired itself out of Earth orbit into a heliocentric orbit as it travelled northwards over Europe shortly before 19:15 UT.  A couple of minutes later it began to dump surplus fuel, a process that continued for around 13 minutes. This led to the appearance of an unusual, cloud-like structure that was easily visible to the naked eye.

When first sighted from the UK, soon after 19:15 UT, the cloud of propellant looked like a comet with a slightly fan-shaped tail travelling from south to north. About 20 seconds later, a second object appeared.  This was the US military weather satellite (DMSP F-18), which the Centaur booster had helped launch some three hours' earlier from Vandenberg Air Force Base (AFB) in California. This was in turn followed by a quite remarkable large circular halo which trailed the two previous objects in formation across the sky. This large circular halo was probably an expanding puff of gas emitted during an earlier firing of the Centaur.

The events were witnessed by John Fulcher from Cransford in Suffolk, who described what he saw as follows:

".outside with telescope looking at various astronomical sights, looked up, and saw an odd small cloud, but no cloud cover in sight, (sky) quite clear. Then another, very similar, if not exact, cloud-like shape following on behind, keeping formation. Tried to follow with telescope but travelling too fast, so used binoculars, and followed them north to south; disappeared near Dubhe in the Plough.  Surrounded by large double halo, oval in shape (covering about 30 degrees, I suppose), as they disappeared from sight, travelling quite fast and still in shape and formation."

There is a fine movie of the clouds and large halo recorded by Jonas Förste of Jakobstad, Finland, available at www.spaceweather.com, together with a selection of images of the event from locations all over Europe.

The Atlas V rocket carrying the Air Force's DMSP F-18 satellite lifted off from Vandenburg AFB at 16:12 UT on 18 October 2009.  Despite a foggy day, the Atlas V flawlessly delivered the satellite to its assigned 838 km x 853 km orbit after an 18-minute flight. This mission marked the 600th launch of an Atlas vehicle, carrying on a tradition that began with the first Atlas A rocket launched from Cape Canaveral Air Force Station (CCAFS), Florida, in 1957. For the Atlas V, Sunday's success was the 18th for the program, with a 100 percent mission success rate. The inaugural launch for the latest Atlas V configuration occurred from CCAFS on 2002 August 21.

Anyone who witnessed the Centaur fuel dump, or who has images or video of the unusual clouds and/or halo is invited to send these to the undersigned at docjohn at dircon.co.uk.

John W. Mason
19 October 2009