Re: Simultaneous Iridium flares

From: Robert Holdsworth (
Date: Wed Mar 26 2003 - 02:07:01 EST

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    I have not had any response to my query so far.  However I have done a web
    search and can find no mention of any flares in such close proximity since
    1999!  There are a few reports of double flares but these have been much
    greater than 1 second apart.
    I would also appreciate it if someone could calculate the separation in km
    or miles - it seems from the respective orbits that it may have been less
    than 100 km.  I guess I should have stated my elevation in feet or metres
    but as it was zero it makes no difference.  It was definitely zero as I was
    standing on the waterfront a few feet from the water and had to be careful
    while skywatching that I did not fall in!
    Robert Holdsworth
    (coordinates below.)
    ----- Original Message -----
    From: "Robert Holdsworth" <>
    To: "Seesat Explosive Address" <>
    Sent: Tuesday, March 25, 2003 10:19 PM
    Subject: Simultaneous Iridium flares
    > This evening 25 March at 20:15 local (UTC plus 12) I observed with the
    > eye simultaneous Iridium flares from a location at Wellington waterfront
    > (41.2861 S; 174.779 E at 0 degrees elevation.)
    > These were from Iridium 28 1997-051-E  and Iridium 94 2002-005-C
    > Although I did not have an accurate means of timekeeping, the  flare times
    > according to Heavens Above were 20:18:38 for I.94 and 20:18:39 for I.28
    > respectively.  To the naked eye they appeared to brighten and diminish at
    > exactly the same time.
    > Azimuth of both was 174 degrees-  predicted magnitude of I.94 was -7 as
    > against -3 for I.28, and respective altitudes were predicted as 25 degrees
    > and 22 degrees.  Ground tracks were very similar.
    > I was only 2.6 km from the flare centre for Iridium 94, as against 17.8 km
    > for Iridium 28.  I did notice that the higher flare was brighter, though I
    > would not have said it was such a marked difference in magnitude as that
    > predicted.  The sky was clear but being very close to  the central city
    > there was considerable background light though it caused little difficulty
    > with the observation.
    > I would be interested to know how rare or otherwise sightings of
    > simultaneous flares are.
    > (Flares were predicted here at 20:31 and 20:32 on 23 March local from
    > Iridium 33 and 91 respectively but unfortunately I was not able to attempt
    > an observation at that time.)
    > Robert Holdsworth
    > Wainuiomata
    > New Zealand
    > 41.26100S, 174.94700E
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