Celestia Forums

Hi there,

I was 'calibrating' Celestia with the the clear sky outside the other night. According to Celestia I would have to see the ISS space station pass right above Rigel at a specific time. After trying for a couple of days, there seems to be no sign of the ISS out in the real sky at that time spot.

Does anyone know if Celestia's location and rotation of the ISS (or any other earth orbiting spacecraft for that matter) is accurate?

Thanks,

EH

Unfortunately, Celestia's display of the ISS as seen from the ground cannot be accurate, for two different reasons.

One is that the orbit of the ISS changes frequently. You have to use current orbital parameters (which have been available in the form of TLEs). The parameters included with Celestia are ancient. The ISS' orbit is scheduled to be boosted on November 11th, for example. Forces due to atmospheric drag and spacecraft docking also cause orbit changes.

The other is that the spherical model of the Earth that Celestia uses does not match the irregular shape of the real Earth. As a result, the line-of-sight toward a satellite in LEO from a specific longitude and lattitude is quite different in Celestia from what you'd actually see.

Very informative reply, selden. Thanks a lot!

Do you know of any other references online to find satellites, with up to date orbital parameters and compensating for the line-of-sight?

Or another way to do so?

If at all possible, of course.

EH

TLEs for many satellites are available at
http://celestrak.com/NORAD/elements/

Grant Hutchison's spreadsheet to convert TLEs to Celestia SSC catalog entries is available at
http://www.lepp.cornell.edu/~seb/celest ... ets.html#3

Unfortunately, there's nothing that really can be done for the line-of-sight problem. I suppose someone could generate a model of a local area from DEM data, but Celestia wouldn't be able to place you on its surface automatically.

Thank you selden.

EH

Event Horizon...If you're using one of the models off my site then the ssc's are quite out of date....Grant was the man...although TERRIER got the ones I used for these models.

Good luck.

An excellent resource for satellite spotting is heavens-above.

http://www.heavens-above.com/