**Previous message:**Edward S Light: "Re: Simultaneous Iridium flares"**In reply to:**Robert Holdsworth: "Re: Simultaneous Iridium flares"**Next in thread:**Robert Holdsworth: "Re: Simultaneous Iridium flares"**Next in thread:**Edward S Light: "Re: Simultaneous Iridium flares"**Reply:**Robert Holdsworth: "Re: Simultaneous Iridium flares"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

Using IridFlar and the current elset at Mike's site, I get the range difference as 1665.6-1391.3 = 274.3 km and a flare center diff of 3.8 seconds. Using SkyMap, their vertical separation was 800.0-693.3 = 106.7 km. There are 17 satellites marked ? (engineering "spare" orbits - I am surprised that HA predicted one of them) in iridium.tle. Their Mean Motions are 14.36-14.93, vs the operational 14.34215. This means that each one of those 17 will overtake one of the 11 in the same plane 0.24-6.49 times per day, in total 47.6 encounters per day. Actually, the higher the frequency, the shorter the duration of each encounter. "Your" Iridium 94 ? flare ground speed differs from the Iridium 28 ground speed by about 0.27 km/s. If the definition of "close" is +- 1 s, this is about 15 km, or 56 seconds. Since Iridium 94 ? passes an operational one 3.56 times per day, there is a close pass 3.3 minutes/day somewhere on Earth. This duration (longer but less frequent, or in one case shorter but more frequent) times 17 is almost one hour out of 24, or about 24000 km in total. The width of a good/visible flare depends on the elevation, say 150 km at night, 10 km in daytime. The length of the flare track may be almost the full orbit for twilight orbits, a half orbit for "noon orbits" at 10 km width, and perhaps 1/10 orbit at 150 km width. At any time, there may be nearly two MMA flares hitting the ground, on the average ?? Assuming an average (150,5,15 km) of 25 km, I get 600 000 square km covered by double flares each day. The Earth is 510 000 000 km, so each should have a one-second coincidence in three years. Please prove my math wrong ! One way is to run a large number of two-month runs with IridFlar, covering one or more years and a number of latitudes, and let a program count the number of coincidences (or coincidences within a minute and divide by 60). > 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 ... > > This evening 25 March at 20:15 local (UTC plus 12) I observed with the > naked > > 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 > > ... > > > > I would be interested to know how rare or otherwise sightings of > > simultaneous flares are. > > ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html

**Next message:**Robert Holdsworth: "Re: Simultaneous Iridium flares"**Previous message:**Edward S Light: "Re: Simultaneous Iridium flares"**In reply to:**Robert Holdsworth: "Re: Simultaneous Iridium flares"**Next in thread:**Robert Holdsworth: "Re: Simultaneous Iridium flares"**Next in thread:**Edward S Light: "Re: Simultaneous Iridium flares"**Reply:**Robert Holdsworth: "Re: Simultaneous Iridium flares"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

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