> hello,I have just completed my predictions for UARS and the following
satellites:
> UARS which by the way I predicted perfectly tonight at -1, any of the NOAA
> satellites,DMPS satellites,Telstar, and Orbcomm satellites. Even A TRMM
> pass will be a predicted flare.
I don't want to discourage you, Kevin, but two necessary assumptions
for glint prediction are an accurate 3-dimensional model of the
candidate satellite's specular surfaces, and accurate knowledge
of that satellite's orientation at any time. While the first
is usually possible, at least to some degree of fidelity, the
second almost never is.
Take UARS for instance. This satellite has an extremely complicated
3-D structure, so your work is already cut out for you just doing
the geometrical modeling. But don't bother. UARS' orientation is
always changing depending on mission operations. It would be a
pointless exercise (no pun intended!) to attempt prediction of
UARS glints since you won't have any information about which way
the satellite bus is pointing.
Even if you could do both of these things, magnitude predictions
would still be very inaccurate. You don't know the reflectivities
of all the satellite surfaces, nor their bidirectional reflectance
distribution functions (BRDFs), so you won't be able to predict
the peak magnitude or the brightness function with angle.
I know you'd like to predict "flares" from satellites other than
Iridium, but you have to appreciate that the Iridium constellation
is a VERY SPECIAL case. The satellite pointing is accurately
maintained and predictable apriori; this allows the BRDF to be
crudely estimated after many dozens of observations. But accurate
glint prediction for these satellites was no small undertaking.
I used hundreds of observations by over a dozen observers in the
"early days" to create the Iridium MMA BRDF. This BRDF has to be
convolved with the radiance distribution profile for the sun
(since the center of the solar disk is quite a bit brighter
than the limb). There are other factors like refraction and the
earth's non-spherical shape that affect predictions, but these
are minor problems to solve.
Of course, the accuracy of the results made the whole exercise
very rewarding for me, as tens of thousands of people worldwide
have now enjoyed predicting and seeing their own flares, either
through Chris's Heavens-Above site, my program, or Randy John's.
Like I said, I don't mean to discourage you, but you're going to
first want to stick to satellites that maintain specific
orientations. UARS and Hubble do not. Orbcomm does, but not
to the degree of accuracy that Iridium does. From the Orbcomm
site:
Attitude Control:
- Nadir Pointed +/-5 degrees using active magnetic
controls, reaction wheel and gravity gradient
- New generation lightweight Earth sensors and magnetometer
+/- 5 degrees makes a huge difference in both the timing of a
glint, and its maximum brightness. This fact alone would be
a pretty big deterrent for me. But when I look at the satellite
geometry relative to its deployed orientation, I see that no
glints are even possible except during the daytime. There are
two circular solar panels, apparently deployed "clam-shell"
fashion from either side of the disk-shaped satellite, and
these are the only "large" specular surfaces you have to work
with. Since they're supposed to be pointing at the sun at all
times, you can only receive glints on the ground during the
daytime.
I haven't checked TRMM, NOAA, Telstar or DMSP, by I suspect
if I did I would find problems for glint predictions with all
of them. (TRMM is a bad choice anyway, since it is constantly
being maneuvered).
If you find a satellite that "behaves" properly, let me know,
and I'll be happy to assist you in your efforts.
Best wishes,
Rob
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