Tuesday, 23 June 2015

[updated] 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 (see timeline here).

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 are here.

UPDATE 20:35 UT: Jim Cook from Germantown, Maryland, describes what appears to be the actual last burn of AVUM in a post on the Seesat list. Putting all information together, I have come to the conclusion that the fuzzy cloud is not so much a fuel vent, but gasses from the actual AVUM burn.
Also: the press kit talks about a "de-orbit burn" for AVUM, but as AVUM has been catalogued as still in orbit (as in previous cases), it is a burn to lower the orbit rather than a true de-orbit burn.

(many thanks to David Murr for his permission to feature his photograph)


bloggy said...

Had it been the visible trail of a rocket firing the line would have been oriented the other way (H flip). More like a fuel vent from AVUM.

Austin Smith said...

I saw this in central Wisconsin. Along with the Auroras, basically the neatest things I've ever seen in the sky! I had to look SOUTH for the auroras at times! I am really glad I caught this rocket too and was hoping it would be explained/observed by others.
It truly seemed like the rocket(I thought it was a satellite) was plowing through the auroas! The northern lights were almost entirely white from my locale so they matched the gas/fuel "wake" from the rocket.

Robert Kelly said...

I saw this at the time I was trying to observe the aurora in a hazy humid sky with a weather system on the way. I noticed this and had never seen anything like it despite a lifetime of natural and man made sky observations.

Samuel Hartman said...

Is this the Sentinel-2?

SatTrackCam Leiden said...

Samuel: it looks very similar so probably it is the AVUm from the Sentinel-2A launch. To really check, I would need your geographic location and the time of the photograph

Samuel Hartman said...

It was approximately 11:43pm in State College, PA.

SatTrackCam Leiden said...

Samuel: sky track and position match well with your image: this was indeed the Sentinel-2A AVUM which you imaged.

Samuel Hartman said...

Awesome, thank you for the help!

Ricardo Rodriguez said...

Echa un vistazo al Tweet de @RichiRod: https://twitter.com/RichiRod/status/614306573813448704?s=09

Ricardo Rodriguez said...

Echa un vistazo al Tweet de @RichiRod: https://twitter.com/RichiRod/status/614306573813448704?s=09