Iridium Satellite Flares

The Iridium satellite series was originally conceived to be a series of 77 (The atomic number for Iridium!) communications satellites, providing a mobile phone communication systems using the satellites rather than ground based relay systems.  The program and phone service was expensive, and eventually only 49 satellites were launched.  In 2000 the whole service was scrapped, and the satellites faced the fate of being burned up in controlled re-entries. However, they have now been utilised for a new role in ground mapping and imaging.

Since their inception, the Iridium satellites have been the bane of astronomers, and they continue to be a nuisance, especially to those astronomers who undertake astrophotography in the hope of finding comets and novas, as they reflect the Sun with their large (188 cm wide x 86 cm long ) antennae panels, and act as orbiting heliographs!

The Iridium’s are also an increasing cause of UFO reports, especially in the summer evenings when people tend to be outside enjoying the evening air as darkness falls. Iridium satellites can easily cause confusion and be misidentified.
The Iridium satellite is itself fairly small, and so is not very bright, being somewhere around +6 magnitude, so would be well beyond naked eye visibility in any built up area with its associated light pollution.  However, due to the antennae panels reflecting sunlight, they can produce a short lived 'flare' lasting between 5 - 15 seconds, and at up to -8 magnitude - twice the brightness of Venus (and we know how that causes misidentifications!), and can even be seen in daylight.   Due to the nature of the satellites themselves, and their orbits, each Iridium has a fairly small area on the ground from which each flare can be seen (approximately 80km across) - at the edge of this 'footprint', the flare is faint, and towards the center the flare is at its brightest.

If the UFO that you saw resembled the bright flaring object in the animation, then you've probably seen one of the Iridium satellites....

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Watching the ISS - Freedom

In some recent times, we have mentioned the possibility of the International Space Station Alpha (ISS or SSA—whichever you prefer) being mistaken as a UFO by an inexperienced/casual  observer.  So just what does the ISS look like when passing over.

This photo will hopefully give you some clue as to the potential magnitude, even while still under construction.  The two photos are 20 second exposures, so the ISS trails as it traverses the sky, and were taken on one of its higher-elevation passes over my home in Oxfordshire in February of this year.

The photo also shows Venus to the middle left, and the second trail below Venus is of one of the regular commercial flights out of Heathrow on its way to America.  This clearly illustrates just how bright the ISS is compared to conventional aircraft lighting.

The photo right shows the ISS as it climbed higher into the sky, eventually passing almost overhead—although it soon eclipsed and was lost to the naked eye.

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Auroral Displays

As you will hopefully know, the night of April 6th 2000 saw an interesting triple conjunction of Mars, Jupiter and Saturm, along with a thin crescent moon.  Many stargazers were out to make the most of the first clear night for nearly two weeks, and saw a lovely sunset, and then emergence of the planets as the sky darkened, and their eventual setting in the southwest.  I made the trip to Avebury - to be in a good setting for the evening.  Mind you, my efforts to photograph the event were hampered by 3 camera failures!

Those stargazers who stayed out just a little while longer will have seen the start of what was perhaps a once in a lifetime auroral display in his country, and certainly the best for well over a decade.  (I tried phoning people that were in my mobile's phone book - just in case).  The display lasted from 9.00pm on the 6th till at least 3.00am on the morning of the 7th.  It was certainly visible from Wiltshire through to Oxfordshire in the early hours.

From my position at Avebury, the skyline over Swindon took on a very strange look, with a very distinct arc of white/green light, that looked like a defence shield out of sci-fi. Various long white/green rays emerged from this arc.  Large expanses of cherry-red glows began to emerge to the northeast, reaching high up towards the zenith.  For the next two and half hours, there were very bright white, green and cherry-red glows, rays, ribbons and streamers. At this point I thought the display was ending, and made the journey home.

However, as I neared Blewbury in Oxfordshire at 12:30am, I noticed the red glows starting to appear again, and as I turned off the main road, and so was facing north, I was amazed as the sky literally lit up with white, green and red glows - it was starting again!  For the next hour and half, most of the sky was lit up with the green arc, and rays and ribbons, with the intense cherry-red glows over huge areas of the sky.  It was difficult to know just where to look for the best 'action'!  At times there was a bright blue/white lightning-like flashing from the arc to the north.

Until one observes an aurora of this intensity, it is difficult to appreciate the scale and speed of the constant changes in patterns.

There was a much feinter display on the night of the 7th, with feint green and red glows, that were not highly visible, it was more of a case of knowing what looked different about a familiar piece of sky. 

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