# 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 20:47:14 +0200
```Hey everyone,

during corona time, being alone under a stary night on a field somewhere
remote is really nice and still possible under the not soo cool situation
we are all in. So I hope you are all still fine, too!

I am currently preparing the next step of my GoPro tests[0] with the
feedback I got for my previous email to this list[1], thank you.
I hav some Starlink observations and extracted the RA/DEC/Time from it.

Now I am putting everything to the IOD format, so I can send it to this
list.
I have some questions and it would be really nice if you could answer them
to me.

So all questions will concern the observations from the following google
spreadsheet, so you can see what I did.

1) What is a good way to fill the "Object number and international
designation" when you do not know the satellite that you observed?

2) Is there a way to quantify the "Sky condition codes", because maybe my

3) What does "Time uncertainty" mean?
This is one of te more interesting questions for me, because I have a few
time uncertainties in a range of seconds.
The GPS of the gopro is only used by the second, not sub second.
So +-0.5sec could be possible.
The storing itself seems to variying. I set the integration time to 10
seconds and that I can see n the data, but the time gaps between the photos
seems to jitter between 2 and 4 seconds. So I would use MX = 18: 1*10E(8-8)
=   1     sec but I am not sure.
For what will this be important?

4) the "Angle format code" I use 2 because I saw a few more of you using
it. Does it make a difference?

5) Is the "Epoch code" related to J2000?

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?

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.

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

I try to find some examples on http://www.satobs.org/ but I would like to
compare what I understood with some sample to be sure.

I know these are a few questions, but I really wouuld like to understand
better how to create the IOD better.

So I hope I will hear from some of you here. As soon as I get a better
feeling of this, I will also try to determinate the orbit parameters of my
observations.

Best regards,

Andreas

[0] https://aerospaceresearch.net/?page_id=1874
[1] [Astrometry] [HowTo] Attitude determination of GoPro camera with
Nova.Astrometry.net to finally track satellites whooshing by in the photos.