Re: IOD Format - Please, some help with a few questions (applied to Starlink observations)

From: Andreas Hornig via Seesat-l <seesat-l_at_satobs.org>
Date: Fri, 22 May 2020 22:13:11 +0200
Hey Cees,

thanks for your fast reply :). That is much appreciated.
I will answer below in between your text

On Fri, May 22, 2020 at 9:09 PM C. Bassa <cgbsat_at_gmail.com> wrote:

> This is always tricky. Some of us use a 99XXX code for the object
> number, i.e. 99123, to signify an object that has not been identified
> yet. For the international designations of unknowns we use a format
> like 20501ABC, where the first two digits indicate the year of the
> observation, the next three the day of year + 500 of the observations,
> with the letters indicating which unknown you saw, A for the first, B
> for the second unknown etc. The crucial bit is to keep the object
> number and international designation of measurements of the same
> object the same. In otherwords, if you saw two unknown Starlink
> objects today (day of year 143), you'd use, e.g. 99123 20 643A for the
> first, and 99124 20 643B for the second.
>

so in your example, the satellite counter is the 123 and the A in 99123 20
643A?


>
> However, in this case you are specifically targeting Starlink
> satellites, which frequently maneuver. So while it may be unclear
> which satellite you observed at the time of the observation, new TLEs
> may help you identify it.
>

THAT will be another qustion later on how to find quickly the right
satellite by my measurements and hopefully set of kepler parameters in
those many TLEs of existing satellites. :)



>
> > 2) Is there a way to quantify the "Sky condition codes", because maybe my
> > poor will your bad condition.
>
> Use what ever describes your conditions.
>

Okay, in those photos it was clear sky, no moon and bright venus. si I
would stay with Fair because venus was bright and shining into the FOV of
the camera at that point.


>
> This is indeed the accuracy of the timestamp you provide. I think 1
> second should be used in your case, but it can be checked against
> other satellites in your images.
>

What do you mean with "checked against"?


>
> > 4) the "Angle format code" I use 2 because I saw a few more of you using
> > it. Does it make a difference?
>
> No, this does not really make a difference. If you are referencing
> positions with astrometry.net, use the RA/Dec formats, so either 1, 2,
> 3 or 7.
>

Okay, so I keep it as it is.


>
> > 5) Is the "Epoch code" related to J2000?
>
> Yes, code 5 is J2000 to reference the positions. This is what
> astrometry.net would reference to.
>

super.


>
> > 6) I am not sure yet how precise my way in determinatig the RA/DEC is,
> so I
> > used MX = 56: 5*10E(6-8) =  0.05   deg/min/sec of arc as the "Positional
> > uncertainty", good idea?
>
> Note the unit of the positional uncertainty is linked to the position
> format. I.e. format 1 has uncertainty in seconds of arc, while format
> 2 has it in minutes of arc. What is your positional accuracy in
> degrees?
>

I don't really know this now. It depends on the visibility of satellite
trail and the timestamp.
So I decided by eye to select a point in on the streak. The streaks ia
about 3-6 pixels wide and I aimed for the middle line and for the end
points. I will explain that in the next how to I want to write. Some
streaks are really obvious and for them it is more a matter of the
timestamp, so that the RA/DEC is really on that time the timestamp says.
for other fainter streaks I hope I found the end and beginning of the
streak. For them it is more than a few arc seconds.


>
> > 7) Where do I find an explanation of how I can determine the "Optical
> > behavior code"? As before, I would like to able to help, but I don't know
> > how to rate that. This is also for the related code sthat follow.
>
> The majority of the satellites will be steady so have code S. Some
> will regular flashing during one or more images, indicating R, while
> others only flash or flare once, so you can use I.
>

Okay, so the one solo flyer in this photo
https://twitter.com/andreashornig/status/1260654918672633856 is a flare. it
was only once during the pass. and it was increasing and decreasing for
about 4-6 seconds.

The one I measured is more like the ones above flying in line. So I did not
see any change. Maybe the magnitude went lower a bit.


>
> > 8) And last but not least, the "Flash period in seconds". Is that from
> the
> > observed satellite?
>
> Yes.
>

In the one from the linked photo, that would be like the 4-6 seconds? that
would only be one period and nothing more.

Best regards,

Andreas
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Received on Fri May 22 2020 - 15:15:00 UTC

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