Flares 2

 

Lacrosse Event Log

Date Lacrosse  UTC Observer Event Mode SARx SARy SunAlt SunAz Comments
24/12/2005 4 18:42:49 PWM Flare XVV -0.3 25.4 19 -144  
25/02/2006 5 03:47:35 ML Flare YVV 0.23 34.7 25 -140  
04/03/2006 5 20:26:50 ML Flare YVV 0.62 29.88 25 -144  
06/03/2006 5 20:19:11 PWM Flare YVV -0.45 35.92 18 137  
11/03/2006 5 19:15:05 ML Disappear       15 121 For ML disappear means mag>3.5
12/03/2006 5 20:02:30 ML Disappear       18 118 Time +/-10s
13/03/2006 5 19:09:41 ML Disappear       17 114 Time +/-3s
22/03/2006 4 19:50:00 ML Flare YVV -0.07 49.48 21 173  
23/04/2006 4 20:58:45 PWM Flare XVV -1.53 24.97 9 170  
29/04/2006 3 20:43:50 PWM Flare YVV 0.079 44.65 9.5 158  
25/05/2006 5 22:02:16 ML Flare YVV 1.13 27.49 7 141 Observed 22:02:01
10/06/2006 2 21:54:46 ML Flare XVV 4.95 32.46 10 166 Magnitude -1.5. Observed 21:54:48
11/07/2006 3 21:40:21 PWM Flare YVV -0.04 37.75 7 166  
14/07/2006 3 00:22:26 ML Flare YVV 0.009 33.87 15 162 Observed 00:22:27 +/-1s, magnitude 0
26/07/2006 5 22:58:37 ML Disappear       18 -164  
31/07/2006 5   ML Disappear           Time uncertain
31/07/2006 5 21:50:56 BD Disappear       14 174  
01/08/2006 5 20:56:50 GH Flare YVV 0.6 29.65 12 169  
03/08/2006 5 22:32:02 PWM None YVV 0.17 25.14 12 162 Bright as Plough stars. No flare so panel not 25
06/08/2006 5 21:39:02 NO Disappear       21 157 Bright as Vega beforehand. Did not reappear
06/08/2006 5 23:15:25 ML Flare YVV -2.58 22.64 17 153 SAR at 33 gives 17 mis-angle 
07/08/2006 5 20:38:13 GH Flare YVV 8.57 -26 7 146 Sharp peak to mag 1.5 for 10 secs then mag 4. Not SAR panel?
11/01/2007 5 18:08:27 ML Flare XVV 2.24 32.76 19 -165 Brief flare from mag +2 to +0.5. Time +/-5secs. Note XVV
20/01/2007 4 18:53:00 ML Flare YVV -0.06 42.84 25 143 To mag +0.5
20/01/2007 5 18:31:27 ML Disappear            
21/01/2007 4 19:29:41 ML Flare YVV -0.28 16.77 25 142 To mag 0.0 with rapid decay
22/01/2007 5 18:25:30 ML/PWM Disappear       20 62 Calibrated curve
23/01/2007 5 17:30:44 ML Disappear       12 60  
23/01/2007 5 19:13:15 ML Disappear       23 57  
24/01/2007 5 18:18:18 ML Disappear       15 54  
25/01/2007 5 17:23:23 ML Disappear       8 52  
09/03/2007 2 20:37:33 PWM Flare YVV -0.3 30.23 22 166 Calibrated curve. NB not XVV as on 10/06/06. Flare from mag 2.0 to 0.22 

 

Notes

  • q and qy are the rotation angles required to give a flare at the time stated. If qx is close to zero then this is encouraging because it is unlikely that the panel is rotated about the satellite x-axis 
  • Sun altitude and azimuth are the position of the Sun in the local satellite co-ordinate system. 
  • Limiting magnitude for ML is about 3.5

This graph shows the variation of q and qy for the Lacrosse 5 flare passes. To add some confusion I have assumed XVV flight mode so X and Y are reversed. So it is encouraging that in most cases  qy passes near to zero at the time of the flare. qx always lies between 20 and 40 degrees so the panel rotation is somewhere in that range. 7th August is an obvious anomaly. 

Observers

Latitude Longitude
ML 52.15412N 4.49081E
PWM 53.4N 2.4W
BD 51.2793N 5.4768E
NO 55.8341N 37.2083 E
GH 49.8866N 8.6558 E

 

Flare July 14th 2006

The first independent verification of my flare predictions came from Marco Langbroek, observing from Leiden, the Netherlands. 52.15412 N, 4.49081E. based on a panel angle of 33 degrees and a flight mode of YVV, I predicted a flare at 00:22:26UTC on 14 July 2006. The satellite was at a good altitude of 69.6 and the mis-angle was 1.5

Marco recorded the flare as peaking at magnitude 0 at 00:22:27UTC +/-1 second! Unfortunately this result does not prove the panel angle is 33 degrees because other angles (certainly between 30 and 36 degrees) also give a minimum mis-angle at the same time. However the angle giving the closest to a direct hit (bright flare) is 33.87. 

A simulator screen shot shows how the incoming sunlight (blue) is reflected off the radar panel and the reflected ray (red) almost directly hits the observers location (blue marker). The mis-angle is the angle between a line linking the observer to the satellite and the reflected ray. The ground track of the flare is in white. I might have seen it myself but it was cloudy.

 

 

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