Re: Iridium Format...Final Version

Bram Dorreman (
Tue, 23 Sep 1997 08:41:08 GMT

I can live with the Iridium flare observation report format as
it has now been defined by Ron Lee. Yet I have some remarks on
1. Some space is saved if the dashes and colons in date and time
   are not used, The results are still readable.
2. For direction I normally use: A = ascending (to northern apex),
   D = descending (to southern apex), E = (parallel to the equator).
   But 'N' and 'S' is also clear to me.
3. I always try to determine the Right ascension and declination
   of the middle of the flare as I am accustomed to refer to the
   starry sky (using 7x50 binoculars). From these coordinates I
   have to convert into Azimuth and declination. I use Redshift 2
   for that. Elaborate.
   If a flare occurs I do not use my binoculars, I would destroy
   my eyes.
4. Azimuth and elevation can be calculated from observer's
   location and recent TLE. So in fact it needs not be reported.
   Fortunately my prediction program (written by Patrick Wils, also
   from Belgium) outputs the Right Ascension and declination and
   Azimuth and elevation of the culmination point.
5. The same is true for Sun's location: it can be calculated.
   I use Redshift 2 for it. But it takes some time.
6. My prediction program uses the angle Sun-Satellite-observer.
   My reports (until now) give the interpolation from observed
   flare location w.r.t. predicted locations at the sky.
   The Skymap convention looks more logical to me.
7. I agree with magnitude estimate without fraction of magnitude.
8. In reporting postional observations of satellites, which I
   started in 1965, the "observers name" was not used, except for
   reports to Smithsonian Astrophysical Observatory (SAO).
   SAO used the site number as primary indication. Always
   we had to report our "Station or Site number". This is a 4 digit
   number, known to COSPAR and registered with the exact geographical
   location (within 300 feet). It is the observers location that
   counts, not the observer. I can imagine that older observers like
   to report their COSPAR site as this defines their observing place.
   Therefore it might be of interest to have 4 positions for observer.
   Anyway there should be a list of all participating PPAS- and
   Iridium flare observers to avoid double use of initials.
   For example: JR might let you think of Jay Respler, a very helpful
   observer and communicator, but JR was already in use in PPAS-
   observations, so Jay is known as JHR. I had to change my initials
   from AD (which I used in the period 1970-1985) into BD when the
   PPAS was defined and initially loaded with previously handwritten
   observation reports.
9. I am very pleased that you have accepted the COSPAR-id of the
   satellites. It has always been used by all sources of predictions
   (USA, Europe, former Soviet Union) and was officially agreed upon
   in the early days of the space era. It has been defined to avoid
   confusion about a satellite's name. I was "educated" with COSPAR-
   id's. All positional observations were always sent in with the
   COSPAR-id as the indication of which satellite the observation
   concerned. If you frequently use them, you don't know better.
   I can tell you the COSPAR-id's of most bright satellites by heart.
   I don't know any NORAD number of them except Mir: 16609. Just as
   with KJ (Kurt Jonckheere).
   The advantage of Iridium's is that the COSPAR-id of them looks
   the same for the same launch:
       97- 20 A..E, 97-30 A..G, 97-34 A..E, 97-43 A..E, 97-51 A..G
   A side effect is that you know which have been launched by Delta
   and which by Proton. You even can guess the COSPAR-id's of these
   rockets, if they were catalogued.
   I must admit that 5-digit-numbers can be processed easier than
   those complicated COSPAR-id's.
A last note: I am happy you have taken the time to figure it out
   and want to receive and hopefully process our flare observations.
About your last question. I am not strong in mathematics, but I feel
there must be a way to predict the places at the sky where a flare
might occur. If there is an Iridium close to it, it should flare.
However I think the orientation of the reflection surface should be
about the same w.r.t. the underlying earth surface. Therefore I was
surprised that flares started to occur low in the South East, while
I was accustomed to expect them middle high in the East. May be
not all Iridiums have the same "attitude".
I don't know much about the Iridium's as body, my son Chris and I
just started to collect some data to be able to create a nice story
about Iridium's visual, or is it optical, behaviour. Yet when I
traveled from home to my office (by bus) I think I was able to
calculate the size of the reflecting surface from our brightest
observations. The result is: at least 4 square meters. I am anxious
to know how large it really is.
Must stop now, start working again. Thanks Ron for your effort
and GO AHEAD. I continue sending in my observations. We have a
rather good time here, more than a fortnight of clear skies. I am
afraid it will be followed by several months of cloud covered skies.
According to a professional Dutch astronomer (in 1958) there is one
clear sky per 6 six days in our part of the world.
 -- Kind regards, Bram Dorreman
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