Re: Unexpected Iridium monster flare
Tony Beresford (starman@camtech.net.au)
Tue, 19 May 1998 13:34:19 +0900
At 16:34 18/05/98 -0700, Frank Reed wrote:
>My wife and I were watching for a mag. -7 flare from Iridium 4 predicted by
>the GSOC web page for 17 May 1998, 19:49:09 local Arizona (mountain
>standard) time (02:49:09 18 May 1998 UTC) at 111.898 W, 33.484 N.
>
>We saw a flare of the expected brightness that peaked about 10 seconds
>before the prediction. Then, as I had my head down looking at my stopwatch
>and notes, my wife said "Oh, there's another one!" I looked up and saw
>another flare at about the same magnitude, this one at the predicted time.
Frank, using iridflar 1.5.2 I predicted iridiums 4 & 5 from your site
for May 17, using the lelements you gave. I then reran the predictions using
elements from alan Pickup's iridiums.tle file. The combined out was:-
Iridflar prediction using element set provided by Frank Reed
IRIDIUM 5
1 24795U 97020D 98126.11093299 -.00000045 +00000-0 -21871-4 0 01913
2 24795 086.4138 356.0696 0003321 030.4032 329.7335 14.36937212052507
IRIDIUM 4
1 24796U 97020E 98126.08880101 +.00000023 +00000-0 +10146-5 0 01879
2 24796 086.4010 356.1387 0003620 111.3746 248.7827 14.34219133052462
Latitude: 33.48400 Longitude: -111.89800 Altitude: 1000.0 m
Time Zone: UTC -7.0 h
Local Iridium Sun Flare Maximum Flare Ir
Date Time Azm El Rnge N I Azm Elv Ang Mg MMA Latit. Longit. #
------------------------------------------------------------------------------
98- 5-17 19:48:16 102 67 830 D L 298 -5 1.4 -2 R 33.4776-111.658 5
98- 5-17 19:49:06 102 69 831 D L 298 -5 0.3 -6 R 33.4826-111.844 4
Iridflar predictions using element set closer to date (Alan Pickup)
Iridium 5 3.0 0.0 0.0 6.0 d 770 x 768 km
1 24795U 97020D 98136.62634326 -.00003383 00000-0 -11531-2 0 1954
2 24795 86.4209 351.6788 0001958 39.3552 320.7761 14.36865442 54015
Iridium 4 3.0 0.0 0.0 6.0 d 781 x 775 km
1 24796U 97020E 98136.62386236 -.00000041 00000-0 -21777-4 0 1873
2 24796 86.3986 351.7356 0004337 88.5852 271.5859 14.34215003 53977
Local Iridium Sun Flare Maximum Flare Ir
Date Time Azm El Rnge N I Azm Elv Ang Mg MMA Latit. Longit. #
------------------------------------------------------------------------------
98- 5-17 19:48:46 102 68 825 D L 298 -5 0.7 -4 R 33.4807-111.774 5
98- 5-17 19:49:08 102 69 829 D L 298 -5 0.2 -7 R 33.4829-111.857 4
I think Chris Peat can confirm the GSOC predictions filter out all satellites
which dont have MM=14.342, so it wouldnt have considered iridium 5.
However it is apparently still orientated correctly. Since its prediction changed
some 30 seconds between element sets it seems the orbit is being tuned.
Tony Beresford