Re: PPAS Considerations

From: Brad Young (brad.young@domain-engineering.com)
Date: Mon Jul 28 2008 - 20:05:13 UTC

  • Next message: Scott and Becky Campbell: "Satobs 28 Jul 2008"

    I did not receive all the text via one of my emails (too long), so I have
    tried to keep this short. Obviously, this is all IMHO only.
    
    >Priority system
    
    I agree with this section completely.
    
    >Variable brightness
    >The PPAS is about these tumbling spacecraft. What we care about is the
    tumble period regardless of the nature of the >variation.
    
    This statement may represent a fundamental difference in why I observe vs.
    what PPAS is intending to achieve. My observational reports also try to
    describe interesting objects that may be worth a look, if only for enjoyment
    or curiosity.
    
    >Sometimes I get observations within which a variation is reported while
    there is only one maximum stated. Then I do not >know whether this is the
    normal brightness variation of steady objects or variations due to rotation.
    
    I try to excise any observations that are obviously phase angle related
    only. Therefore, if the maximum occurs late or early relative to
    culmination, it is reported, but not if there is only one maximum and it is
    near culmination. This is by its nature a tricky call.
    
    >Processing of the observations
    
    I elaborate on editing of the observations and distribution below.
    
    >Format of PPAS-observations.
    
    I will review the referenced web page and see if have adhered to convention.
    
    >Note references
    
    No comments.
    
    >Reporting of the end time
    
    No comments.
    
    >Reporting of individual timings
    >My conclusion: You need not to include them if regular. With irregularities
    they can be very useful when determining a >period.
    
    Agreed. I rarely do this, but have records on many if the need ever arises.
    
    >Detection of a flash period...I now follow a satellite with variable
    brightness as long as possible during a transit.
    
    Agreed, although at my site I have some spots with trees, etc. as I'm sure
    others do.
    
    >There are also many small satellites with flat surfaces causing faint
    flashes. Such satellites can be seen steady, show >some flashes times and
    then become steady again. These are not really PPAS objects.
    
    Is there an "official" definition of a PPAS object?
    
    >Observations per satellite
    
    We need more observations of faint objects - agreed.
    
    >Flashes and flares
    >Operational Iridium cause "flares", tumbling Iridiums cause flashes.
    Iridium flares are predictable, flashes are not. I >suppose that flares
    caused by Skymeds, Key Holes and Lacrosses can be predicted as long their
    attitudes can be >predicted. Almost always such a satellite will flare under
    the same conditions in the same area of the sky (at nearly >the same
    elevation and Azimuth).
    
    I'm not sure if this means I should continue reporting these flares or not.
    I cannot (yet) agree that all these objects flare at the same attitudes, and
    would propose that reported observations are the only way to verify any
    predictability.
    
    >In summary:
    
    No comments.
    
    >Last Note
    >All observations are scanned, but not all will be written to the PPAS
    database. The less suitable observations are kept >in a separate file.
    Possibly this file will be made available to other observers.
    
    This is probably the only real issue I have with the entire note. If I take
    the time to post the observations, I would like to think they are not
    discarded. If they are unsuitable for PPAS (flares and flaring geosats
    spring to mind) then I hope there will be a publicly available database
    where these reports are kept, else, what's the point of posting them? I can
    just keep them to myself and not worry about them being discarded.
    
    This hobby, perhaps as much as any other, is completely dependent on
    symbiotic relationships not only due to geographic limitations, but due to
    lack of public data (classified objects) and a dearth of data (optically
    active objects). I hope that any data that's received is at least kept,
    perhaps summarized, as it is now. I know not all of my postings are useful -
    either positional or PPAS data. But unilaterally disposing of data is not
    the answer.
    
    I rely on classfd.tle for positional predictions of classified objects and
    PPAS assignments (plus my own notes and Mike's) to determine what to look
    at. If PPAS data becomes less inclusive, it will become less useful. The
    PPAS database and priorities do not predict optical behavior in every
    situation per se, but it is a place to start.
    
    Brad Young
    TULSA 1
    COSPAR 8336
    36.1397N, 95.9838W, 205m ASL
    
    
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