Help with Earth orbiting satellites elements ID

[Alan Snook]

As I don’t seem to be able to avoid the ‘sputniks’ lately I thought I might work my way through the (USA) Astronomical League’s “Earth Orbiting Satellite Observing Program”.  The standard observing form requires me to note down something called “Element Set Satellite ID”.  I’ve read their explanatory notes but I’m still in the dark about how and where I can get this information. I’m also a bit doubtful about the AL’s documentation, which gives MIR as an example, suggesting it’s not been dusted off and updated for >20 years. Can anyone help me out please?

May I present two practical examples –

1) the Starlink L5 train of 60-odd 1st magnitude satellites seen from about 20:30UT on April 19, 2020.

2) A bright ISS pass on July 20, 2020 at 22:31

Many thanks in anticipation.

[Dominic Ford]

Alan,

Satellites are normally referred to by their NORAD ID numbers, which are assigned by the US military. There are various websites which will list these. Here’s a table from my own website…

https://in-the-sky.org/search.php?searchtype=Spacecraft

The UN have their own separate satellite numbering system, which is the COSPAR ID you see in the second column. Not many people seem to use it, though.

I think when somebody refers to “element set satellite ID”, they’re refering to the “two-line elements” format used by websites such as Celestrak when publishing the current orbits of spacecraft. For example, their current data for the ISS is as follows…

ISS (ZARYA)
1 25544U 98067A 20208.81898250 -.00001223 00000-0 -13780-4 0 9996
2 25544 51.6445 152.3082 0000916 163.1489 218.7089 15.49504233238167<

There’s full documentation on the Celestrak website about what all the numbers mean, but the second number on each line is the NORAD ID number of the spacecraft in question. The ISS has a NORAD ID of 25544.

Hope that helps,

Dominic

[Alan Snook]

Thanks Dominic, with your pointers and a couple of sessions with a wet towel I’ve got up to speed with how it all works. It’s a bit of an eye-opener to discover that the format of these 2-line-elements harks back to the 80-line punched cards of the 1960’s including only two digits for the year!

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