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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.
1.2 KiB
1.2 KiB
Document
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, stored here as an archival reference. It shows where I got the formulas for calculating planetary rotation axes as a function of time.
Planetary Rotation Axis Data
The *.txt data files were generated using the JPL Horizons online ephemeris tool.
Here are the settings I used to generate these data files:
- Ephemeris Type = Observer Table
- Target Body = whichever planet the file is named for
- Observer Location = Geocentric (but must use the Sun for generating Earth)
- Time Specification = 1970-01-01 to 2050-01-01, step = 30 days
- Table Settings:
- check 32. "North Pole RA / DEC"
- Reference Frame = ICRF
- Date/Time format = calendar and Julian Day number
- Time digits = HH:MM
- Angle format = decimal degrees
- Refraction model = no refraction (airless)
- Range units = astronomical units
- RTS flag = disabled
- Object summary = checked