Friday, November 20, 2009

Yesterday's GOCE flare modelled

After measuring the image I obtained of yesterday's GOCE flare, I determined the flare time to be 17:40:34.9 UTC (Nov 19).

Using Simone Corbellini's excellent Visual SAT-flare Tracker 3D software I found the following observational geometry:

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SAT ID #34602 (09013A) GOCE
ORIENTATION TYPE #4: V-Sun
ROTAX-DEC: 0 ROTAX-RA: 0
NUMBER OF SURFACES: 1
M#01 - 19/11/2009 17h40'34" - UM1 >>> .8839;77.1618;1

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Note that the angle sun-craft-observer is close to zero (0.9 degree): sun, observer and craft are on one line.

In below graphic representation from Simone's software, the green line is the observed flare path over Earth's surface:

click image to enlarge



Knowing that the spacecraft has a fixed attitude towards the sun (see the ESA website), and Octagonal shape (meaning reflective surfaces at angles 22.5 and 67.5 degrees available), I find the following theoretical flare model:

SATELLITE SURFACE MODEL
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SAT ID #34602 (09013A) GOCE
ORIENTATION TYPE #4: V-Sun
ROTAX-DEC: 0 ROTAX-RA: 0
NUMBER OF SURFACES: 2

M#01 - 19/11/2009 17h40'34" - UM1 >>> 0;67.5;1

M#02 - 19/11/2009 17h40'35" - UM2 >>> 0;22.5;1

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click image to enlarge


This suggests the tilt of my observation is 10 degrees off from the nominal theoretical tilt: either the true tilt is 10 degrees different, or (and I favour that, as it is most likely) modest flaring is still visible 10 degrees on either side of the tilt axis.

In the latter case, closer approaches to the central flare path potentially might result in much brighter flares compared to yesterday's. I'll have opportunities to check that the next 3-4 days, if weather cooperates...especially the evening of 21 November might then see a potentially very nice flare for me.

Yesterday's image of the flare/glint I posted came out a bit dark after conversion to jpg. Below is a lighter version and a larger detail image.

click image to enlarge


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