Add ephemeris, docs for rotation; but, untested?
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@ -43,9 +43,9 @@ Command Line Tool
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If you have downloaded a ``.bsp`` file, you can run ``jplephem`` from
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the command line to display the data inside of it::
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python -m jplephem comment de430.bsp
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python -m jplephem dap de430.bsp
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python -m jplephem spk de430.bsp
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python -m jplephem comment de430t.bsp
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python -m jplephem dap de430t.bsp
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python -m jplephem spk de430t.bsp
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You can also take a large ephemeris and produce a smaller excerpt by
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limiting the range of dates that it covers::
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@ -75,7 +75,7 @@ The recent DE430 ephemeris is a useful starting point. It weighs in at
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115 MB, but provides predictions across the generous range of years
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1550–2650:
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http://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/planets/de430.bsp
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https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/planets/de430.bsp
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After the kernel has downloaded, you can use ``jplephem`` to load this
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SPK file and learn about the segments it offers:
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@ -256,6 +256,32 @@ time of day. Nearly all ``jplephem`` routines accept this optional
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``tdb2`` argument if you wish to provide it, thanks to the work of
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Marten van Kerkwijk!
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Support for Binary PCKs
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-----------------------
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You can also load and produce rotation matrices from a binary PCK file.
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Its segments are available through the ``segments`` attributes of the
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returned object.
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>>> from jplephem.pck import PCK
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>>> p = PCK.open('moon_pa_de421_1900-2050.bpc')
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>>> p.segments[0].body
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31006
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>>> p.segments[0].frame
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1
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>>> p.segments[0].data_type
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2
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Given a solary system barycenter Julian date, the segment will return
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the three angles necessary to build a rotation matrix: right ascension
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of the pole, declination of the pole, and cumulative rotation of the
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body’s axis. Typically these will all be in radians.
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>>> np.set_printoptions(precision=6, suppress=True)
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>>> tdb = 2454540.34103
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>>> print(p.segments[0].compute(tdb, 0.0, False))
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[ 0.039279 0.387836 3253.013946]
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Legacy Ephemeris Packages
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-------------------------
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