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

From: Andreas Hornig via Seesat-l <>
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 <> 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

> 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, 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
> would reference to.


> > 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 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,

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

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