[graham.d (OP)]

Whilst having a few drinks in my neighbours garden (with my neighbours, I should add) we observed a very bright, large (and slightly diffuse) red light moving fast and silently across the sky. As it was an hour or so after sunset I assumed it was a Low Earth Orbit satellite reflecting the sun. As it was so bright, I thought it may be the ISS however it was moving from East to West and the ISS does not go this way.

It was on 17th August 2012 and more or less overhead over Orpington, Kent, UK. There seems to be a few websights that will predict satellite positions or even give you the current position of lots of LEO satellites but I could not find any that will do this retrospectively, i.e. where I can put a location and time (in the past) and ask what satellites were overhead. Has anyone got any ideas?

[SeanB]

heavens-above.com is one to try.

[graham.d (OP)]

Thanks Sean. Good site and did allow a search on my location and for 17th August for all satellites brighter than magnitude 4.5 (for example). Unfortunately it did not find anything that would have taken a path east to west over my location. As the site seems to have data on every bright object in earth orbit, I have a puzzle as to what this was. It was between 22:00 and 22:15 (BST) and took a perfectly straight path with the speed that resembled that of a LEO satellite. I don't think it was a low flying plane as it was too silent (there were plenty of aircraft about, for comparison, as it is on a flight path close to London). 

[CliffordK]

Perhaps you were being buzzed by Aliens  [)]

[graham.d (OP)]

Aliens would not be so obvious. Or if they had been as portrayed by Douglas Adams, they would have waited until I alone and remote and made beep-beep noises just to ensure that nobody would believe me :-).

I'm 90% certain that it was a LEO satellite. The website that Sean suggested was very good but there are 100s of thousands of satellites in all sorts of orbits and I may have missed finding this one. What is unusual is the East to West trajectory near London. If only I could search the data more flexibly I suspect I would have a chance of identifying it given the time, position and trajectory - not to mention its brightness.

[damocles]

How long did the observation last? Some of the details are consistent with an iridium flare, but that would typically be over in a matter of 5-10 seconds, and unless the air is rather polluted it would not appear red.

http://en.wikipedia.org/wiki/Satellite_flare#Iridium_satellite_flare

Iridium flares are extremely locality sensitive. At any particular place there are about 2 really bright ones per week. There is a calculator/predictor for your locality on the heavens above website.

[syhprum]

May I suggest you download WxTrack that will enable you to go back to 17/08/12 with no problem

[graham.d (OP)]

Damocles, it wasn't an Iridium flare. I'm not sure that it was an Iridium satellite at all as it seemed too bright and was visible for a considerable time - the whole period of its transit from when I noticed it coming from the east until it was getting low on the horizon in the west. I did not have the presence of mind to time it, but it was minutes rather than seconds.

Syphrum, thanks, I will try WxTrack.

[imatfaal]

just went to heavens-above.com - top site - good find SeanB

[graham.d (OP)]

Regrettably, neither WxTrack nor Heavens-Above identified my UFO. WxTrack is good in that it can try to identify a satellite visible from any specific locaction at any day/time but it's database is not comprehensive unless downloading the Kepler data from other websites; but it is also not very easy to use. Heavens-Above is very comprehensive but cannot do a search on satellites overhead for a particular time/location (at least, I have not found a way) and it would take an age to go through the database of orbiting things one by one. I fear the object must remain as a UFO :-(

[damocles]

Regrettably, neither WxTrack nor Heavens-Above identified my UFO. WxTrack is good in that it can try to identify a satellite visible from any specific locaction at any day/time but it's database is not comprehensive unless downloading the Kepler data from other websites; but it is also not very easy to use. Heavens-Above is very comprehensive but cannot do a search on satellites overhead for a particular time/location (at least, I have not found a way) and it would take an age to go through the database of orbiting things one by one. I fear the object must remain as a UFO :-(

A last fling, as far as I am concerned. Your location in England is, as you say, busy with aircraft.

It was between 22:00 and 22:15 (BST) and took a perfectly straight path with the speed that resembled that of a LEO satellite. I don't think it was a low flying plane as it was too silent (there were plenty of aircraft about, for comparison, as it is on a flight path close to London).

But these would be mostly aircraft operating between Heathrow/Gatwick and Southern/Central European destinations, and at fairly low altitudes. Is there any chance at all that you could have been seeing a very high flying large plane on a long haul leg -- e.g. Strasbourg to Montréal?

[graham.d (OP)]

I live just SE of London so there are plenty of aircraft about and I'm used to seeing them day and night. Because its angular velocity (relative to my position) was much larger than all other aircraft (many of which are in a holding pattern for Heathrow and around 10,000 to 15,000 feet or so) it was either of aircraft speed but much lower (but silent) or very much faster and higher. The diffuse red colour looked like it could be reflected sunlight although it was quite sometime after sunset and a clear starlit night. It was close to being directly overhead though was slightly north and moving east to west so, if an aircraft,  it is possible that I could see his port (red) light as it was approaching but it would not be visible once going away from me. However it was red until a considerable distance away. Also there were no other lights or strobes.

It looked to me like a satellite which I don't get too excited about, so I did not pay too much attention to noting the transit time or exact time it was overhead. It was only after that I realised that its east-west path makes it less common for a satellite so bright. I still think it is probably a LEO satellite or maybe some space garbage (used rocket etc) however I have not been able to identify it.

[imatfaal]

Graham - could it have been burn upon entering atmosphere.  That would explain the speed and colour, if not the direction and definitely not the fact that it was happening near one of the largest groups of people and aeroplanes on the planet

[graham.d (OP)]

I don't think so. Actually I am coming around to thinking it was as Damocles suggested: it was just a long haul aircraft. I did a few calculations: a LEO satellite at 15,000mph and an altitude of about 500 miles would have moved across my estimated field of view in about 7 minutes, an aircraft at 38,000ft and travelling at 550mph would do it in about 2.7 minutes. I'm sorry I made no timings but I would guess it was closer to 2.7 minutes than 7 minutes. I was slightly on its port side (though almost under the flightpath) but that could explain only seeing a red light. Strobe lights are sometimes switched off if overflying major airports. The light may have been diffuse because I may have been seeing reflections of the port navigation light from the fuselage, an engine nacelle or from the underside of a wing. This may also explain why I could see it long after I would have expected it to vanish (to be replaced by a white light) as per the rules for nav lights. I cannot explain its unusual brightness.

Anyway, I now have access to some good satellite finder sites which I can play with. Did I mention the visit from some green pointy eared blokes the next day?

[imatfaal]

Anyway, I now have access to some good satellite finder sites which I can play with. Did I mention the visit from some green pointy eared blokes the next day?

No but now you have - Run! Run Hard! Don't look back! Don't Hesitate Just Run!

[CliffordK]

If it was a plane, they often have set routes, and you might see it again.

Was it heading northward, or southward, or directly west?  Many flight paths take the planes somewhat northward towards the poles, so a flight originating in Eastern Europe and heading to the USA or Canada might fly over the UK.

[graham.d (OP)]

It was going almost due west. This would be a great circle route from Northern Germany or the Netherlands to anywhere down the Eastern seaboard of the USA for example.