Predict Local Circumstances of Transits of Mercury & Venus

Predicting local circumstances (topocentric azimuth and elevation) of solar transits of the planets Mercury and Venus.

This submission is a MATLAB script named transit which can be used to predict the local circumstances of transits of Mercury and Venus across the Sun. This software provides the universal times and topocentric coordinates of the Sun at the beginning (ingress - exterior contact) and end (egress - exterior contact) of the solar transit, and the time and coordinates at least distance. The source ephemeris for this routine is a JPL ephemeris file.

This application uses several functions ported to MATLAB from the Fortran version of the NOVAS (Naval Observatory Vector Astrometry Subroutines) source code developed at the United States Naval Observatory. Information about the NOVAS software suite can be found at https://aa.usno.navy.mil/software/novas_info.

The transit MATLAB script also uses routines from the MICE software suite to read and evaluate the DE430 ephemeris data. Ephemeris files, platform dependent versions of the MICE mex file and other useful MATLAB functions are available at naif.jpl.nasa.gov/naif/toolkit_MATLAB.html. MICE is a MATLAB implementation of the SPICE library created by JPL.

This script uses a combination of one-dimensional minimization and root-finding to solve this problem. The objective function used in these calculations is the topocentric separation angle between the center of the Sun and the planet in transit.