Disappearences

 

Lacrosse 5 has a habit of mysteriously fading during a pass. Here are 2 example light curves. 

These light curves are calibrated using the method describe here 

On 26/03/2007 Mike Tyrrell and I jointly observed a really interesting pass of Lacrosse 5. Mike managed to resolve the satellite in various images which will soon be processed. During the pass Lacrosse 5 performed all its brightness tricks. At the beginning there was a double flare. Clearly we did not observe that event simultaneously. The ground track of the flare was sweeping from West to East which meant I saw it at 20:04:20, 5 seconds after Mike.

This flare is consistent with flight mode YVV and a panel angle of 32.4 (although I now think a curved panel is most likely). 

At 20:04:54 a sudden 3 magnitude fade occurs. This event was observed simultaneously by Mike and me and also Gerhard Holtkamp in Germany. This proves the fade is inherent to the satellite and not a function of viewing angle. 

 

Another sudden fade after a corresponding brightening. This was very similar to 19/03/07 when the satellite flared slightly before eclipse but seemingly entered eclipse rather early so maybe it had actually started to fade.

 

A half magnitude fade of Lacrosse 3. Much smaller than Lacrosse 5 but proves a fade event is not unique to L5.
Here Lacrosse 5 faded by about 2.5 magnitudes in 14 seconds. 

The y-scale is inverted so that bright magnitudes are at the top making it more intuitive to view.

 

A sudden brightening, then a drop of 5 magnitudes then a final flare. A tough light curve to explain!

This data is from an observation by Mike Tyrrell. I have a video of the event but I bungled the software so I have no brightness curve. 

 

 

 

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