Mittwoch, 24. Juni 2015 - 15:45 Uhr
NOT A UFO: Many people who went outdoors to look for auroras on June 22nd saw auroras -- and something more. "We noticed a ghostly cloud-like object moving in an arc from the southeast to the northeast," says Lauri Kangas of Fort Frances, Ontario (Canada). "My wife commented that it was the closest thing she has seen to a UFO!" Kangas took this picture of the apparition:
David Jones of Lawrenceville, Georgia saw it, too. "At first I thought it was an airplane traveling south to north very slowly, but then I noticed it looked kind of fuzzy," he says. "As it continued traveling north, the star-like object clearly had a circle of mist or fog around it. I could also see smaller lights around the main one that appeared to twinkle."
This was not a UFO. Satellite expert Marco Langbroek explains: "On June 23 at 01:51:58 UT, the European Space Agency launched a Vega rocket with the Sentinel-2A satellite from Kourou, French Guyana. What [Kangas and others saw] is probably gases from the rocket's last engine burn."
Aurora hunter images the last moments of the AVUM (4th stage) from the Sentinel-2A launch
image (c) David Murr, used with permission
On June 23 at 01:51:58 UT, ESA launched a Vega rocket with the Sentinel-2A satellite from Kourou, French Guyana.
About two hours later, US astrophotographer David Murr was watching the sky as part of an aurora watch in Louisa, Virginia. Just after he had set up, he saw and imaged a "cloudy blob" moving from SE to NW through Ursa major (just above the trees in the image):
After Murr's tweet and image were brough to my attention through a retweet by David Dickinson, I could quickly confirm this was related to the Sentinel-2A launch two hours earlier.
What is visible is probably fuel venting [but: see update below: it could actually be gasses from the actual last engine burn] by AVUM, the Attitude and Vernier Upper Module that assists in putting the payload into its intended orbit after separation from the third stage. The AVUM has liquid fuel engines (the Zefiro third stage has solid fuel engines) and did a final burn, aiming at de-orbiting it lowering its orbit, just 10 minutes before the observation
The map above shows the predicted track for Murr's Virginia location for Sentinel-2A and the Sentinel Zefiro 3rd stage : it matches the sky track and direction of movement of the "fuzzy blob" on his image extremely well. There is a small time difference of only a few minutes, but all taken it is very clear this object was connected to the Sentinel-2A launch (the plot is based on orbital elements for the Vega 3rd stage and Sentinel-2A from some hours later: there are no orbital elements for the AVUM).
Murr was not the only one spotting and photographing the object: more photographs by several other US observers.