jplephem for Debian
===================

Project description
-------------------

From: https://pypi.org/project/jplephem/

Cite as: Astrophysics Source Code Library, record ascl:1112.014
(https://ascl.net/1112.014).

The jplephem package can load and use a Jet Propulsion Laboratory (JPL)
ephemeris for predicting the position and velocity of a planet or other
Solar System body. It currently supports binary SPK files (extension
.bsp) like those distributed by the Jet Propulsion Laboratory (
https://ssd.jpl.nasa.gov/ftp/eph/planets/bsp) that are:

* Type 2 - positions stored as Chebyshev polynomials, with velocity
  derived by computing their derivative.
* Type 3 - positions and velocities both stored explicitly as Chebyshev
  polynomials.
* Type 9 - a series of discrete positions and velocities, with separate
  timestamps that do not need to be equally spaced. Currently there is
  only support for linear interpolation: for Type 9 ephemerides of
  polynomial degree 1, not of any higher degrees.

Note that even if an ephemeris isn't one of the above types, you can
still use jplephem to read its text comment and list the segments
inside, using the subcommands comment and daf described below.

Note that jplephem offers only the logic necessary to produce plain
three-dimensional vectors. Most programmers interested in astronomy
will want to look at Skyfield (http://rhodesmill.org/skyfield) instead,
which uses jplephem but converts the numbers into more traditional
measurements like right ascension and declination.

Most users will use jplephem with the Satellite Planet Kernel (SPK)
files that the NAIF facility at NASA JPL offers for use with their own
SPICE toolkit. They have collected their most useful kernels beneath
the directory:

http://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/

To learn more about SPK files, the official SPK Required Reading
(http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/spk.html)
document is available from the NAIF facility's web site under the NASA
JPL domain.


JPL Ephemieris files in Debian
------------------------------

Currently Debian do not have a database of ephemeris files or a
standard mechanism to retireve and store them.

The user is in charge of downloading JPL ephemeris files needed by
jplephem and save them in a place where jplepem can access them.

Please refer, e.g., to the links provided above for a possible source
of JPL ephemeris files.

Some packages like e.g. Skyfield (https://rhodesmill.org/skyfield/)
provide utilities to download (among others) ephemeris files and high
level functions to use them.

-- Antonio Valentino <antonio.valentino@tiscali.it>  Sun, 14 Aug 2022 17:04:52 +0000
