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I'm starting to implement formulas from the IAU 2015 report: https://astropedia.astrogeology.usgs.gov/download/Docs/WGCCRE/WGCCRE2015reprint.pdf This is a work in progress. The unit test is partially finished. The C function Astronomy_RotationAxis() works only for the Sun and Mercury. I want to also return a rotation matrix that reports the rotating frame in a way more suited to graphics work. I will add this to the type astro_axis_t later.
24 lines
1.2 KiB
Markdown
24 lines
1.2 KiB
Markdown
# Document
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The file `iau_rotation_elements_2015.pdf` is a copy of the source document [Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015](https://astropedia.astrogeology.usgs.gov/download/Docs/WGCCRE/WGCCRE2015reprint.pdf), stored here as an archival reference. It shows where I got the formulas for calculating planetary rotation axes as a function of time.
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# Planetary Rotation Axis Data
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The `*.txt` data files were generated using the [JPL Horizons](https://ssd.jpl.nasa.gov/horizons/app.html#/) online ephemeris tool.
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Here are the settings I used to generate these data files:
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- Ephemeris Type = Observer Table
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- Target Body = *whichever planet the file is named for*
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- Observer Location = Geocentric (but must use the Sun for generating Earth)
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- Time Specification = 1970-01-01 to 2050-01-01, step = 30 days
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- Table Settings:
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- check 32. "North Pole RA / DEC"
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- Reference Frame = ICRF
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- Date/Time format = calendar and Julian Day number
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- Time digits = HH:MM
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- Angle format = decimal degrees
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- Refraction model = no refraction (airless)
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- Range units = astronomical units
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- RTS flag = disabled
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- Object summary = checked
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