Re: seesat-d Digest V96 #245

Bart De Pontieu (BDP@MPEPL)
Wed, 14 Aug 1996 19:35:32 +0100 (CET) 

Lew Gramer wrote (last week):

>With regard to flash timings, I'm wondering if there is value in simply 
>calculating averaged periods? I.e., "AA 10 maxima achieved in 38.5 seconds". 
>Recording such a long-sample observation would be less subject to individual 
>timing errors, and much easier for newbies like me to master. 

This is exactly the method everyone used to use before the advent of multiple
split stopwatches. And it is the method many people still use when reporting
observations to the BWGS. It is also the method advertised on our Web-pages
(http://www.rzg.mpg.de/~bdp/vsohp). Like Lew says, just counting several
dozen flashes and timing the period between flash 0 and flash n, is much easier
than timing every single flash. The timing error is also much smaller on the
calculated flash period, than the one found by just timing *one* flash period.

>Is there value 
>in such long-sample flash times? 

There certainly is. The accuracy obtained in this way is sufficient to study
the temporal evolution of flash periods. See also our pages for some of the
research being done on this. I gave a talk at the COSPAR-meeting on Space
Debris studies last month in Birmingham about the possible uses of the PPAS-
database of photometric periods that the BWGS maintains.

>Is there significant likelihood of catching 
>small time-horizon variations with the standard method. A curious newcomer's 
>question,

The likelihood of you catching small synodic effect variations of the flash
period during one pass is not extremely high. However, combining observations
of one satellite observed during passes within say 24 hours of the other
observations, it is possible to boost that likelihood. This is done in the
DRA project, which aims at determining the rotation axis of tumbling rockets
this way. Contact me for more details.

>PS: A hearty welcome to Vince Gardiner, BTW! It's nice to have fellow beginners 
>contributing to this list... -L

And there's many more than just Vince. He's just one of the few who wrote an
introduction. My estimate is that about 10% of the new subscribers actually 
send in an 'introduction'.

Cheers,
     Bart
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Bart De Pontieu --  Max-Planck-Institute for extraterrestrial Physics, Garching
bdp@mpe-garching.mpg.de  --      http://www.rzg.mpg.de/~bdp/satintro.html
Join us at Eurosom 2, Oct 19/20 1996 -- http://www.rzg.mpg.de/~bdp/eurosom.html
BWGS-coordinator -- Flash editor -- SeeSat-L administrator -- would-be-observer
   "Life is like a jigsaw. You get the straight bits, but there's something"
       "missing in the middle." -- XTC, "All Of A Sudden (It's Too Late)"
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