36 lines
1.5 KiB
Python
36 lines
1.5 KiB
Python
"""JPL Planetary and Lunar Ephemeris DE421 for the jplephem package.
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This is a recent short-period ephemeris published by the Jet Propulsion
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Laboratory. It requires only 27 MB of storage and is specially accurate
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with respect to the position of Earth's Moon.
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:Name: DE421 (February 2008)
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:Years: 1900 through 2050
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:Planets: Yes
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:Sun/Moon: Yes
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:Nutations: Yes
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:Librations: Yes
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:Report: `Folkner, Williams, Boggs (2009) [PDF] <http://ipnpr.jpl.nasa.gov/progress_report/42-178/178C.pdf>`_
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:Size: 27 MB
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The JPL called this ephemeris is a "significant advance" over
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predecessors like `DE405 <http://pypi.python.org/pypi/de405>`_ / `DE406
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<http://pypi.python.org/pypi/de406>`_ and cited accuracies that are in
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many cases ten times greater, such as giving the position of Venus
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within 200m and the positions of Earth and Mars within 300m over the
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last decade. Note that even greater accuracies are achieved, for
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Mercury and Venus in particular (but not for the Moon), by `DE423
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<http://pypi.python.org/pypi/de423>`_ which also has the advantage of
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covering a 400-year period instead of only 150 years.
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Greater accuracy can also be expected from the long-term ephemeris
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`DE422 <http://pypi.python.org/pypi/de422>`_ since it incorporates more
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spacecraft observations than DE421. It also covers a period of 6000
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years, making it useful to astronomy historians. But as it requires a
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half-gigabyte of disk space, some users may prefer DE421.
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To compute using this ephemeris in Python, see the `jplephem
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<http://pypi.python.org/pypi/jplephem>`_ package.
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"""
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