celestia-gnss/README.md

# Spacecruft Celestia GNSS
Celestia is a "real-time space simulation that lets you experience our
universe in three dimensions".

It contains many celestial objects, but few that are man made, just
as Hubble. It has a TLE for the ISS, but it doesn't update it.

There is a spreadsheet that you can enter a TLE into it and it
generates an `.ssc` file that Celestia can read. Using a spreadsheet
is a bit awkward, and hard to automate.

It would be real swell to be able to add TLEs to Celestia more easily.
Then all the GNSS satellites could be added. Or SatNOGS...

It will take the data that generates this:

![spacecruft-galileo](pics/galileo.png)

And render it in this application:
![celestia-screenshot](pics/celestia-screenshot.png)


# See Also

## Spacecruft
Spacecruft:

* https://spacecruft.org/spacecruft/gnss-earth

* https://spacecruft.org/spacecruft/celestia

## Celestia
Upstream Celestia:

* https://celestia.space/

* https://github.com/CelestiaProject/Celestia

## TLE Conversion

TLE Conversion Spreadsheet:

* https://www.classe.cornell.edu/~seb/celestia/hutchison/spreadsheets.html

* https://www.classe.cornell.edu/~seb/celestia/hutchison/tle-xls.zip

## Solar System Catalog
*"Solar System Catalog" files are primarily used to define the objects which
can be found in a stellar system, such as planets, moons, asteroids, comets,
and spacecraft. They also have four other uses: they can define alternative
surface textures, locations on or near an object, and orbital reference points.
An SSC file can also edit objects which have been defined in other SSC catalog files.*


Info on `.ssc` files:

* https://www.classe.cornell.edu/~seb/celestia/creating-ssc-files.html

* https://en.wikibooks.org/wiki/Celestia/SSC_File


In Celestia name "Galileo" is used for the *other* spacecraft, not
for the EU GNSS. So the name used in development here adds `-gnss`,
ala, `galileo-gnss.ssc`, whereas the other GNSS don't.


## TLE Sources

Beidou (China)
* https://celestrak.com/NORAD/elements/beidou.txt

Galileo (Europe)
* https://celestrak.com/NORAD/elements/galileo.txt

Glonass (Russia)
* https://celestrak.com/NORAD/elements/glo-ops.txt

GNSS (All)
* https://celestrak.com/NORAD/elements/gnss.txt

GPS (USA)
* https://celestrak.com/NORAD/elements/gps-ops.txt


## Spice
Spice TLE:
"Evaluate NORAD two-line element data for earth orbiting spacecraft."

* https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/spicelib/evsgp4.html

## pyorbital
Orbital and astronomy computations in python.

* https://github.com/pytroll/pyorbital/

* https://pyorbital.readthedocs.io/


## 3D Models

Galileo 3D models are from the ESA:

* https://gssc.esa.int/education/galileo3d/


# License / Copyright
Upstream sources under their respective copyrights.

Copyright (C) 2022 Jeff Moe.

License: GPLv2 or any later version.