Something above my abilities and Fortran experience. I found SOFA (Standards of Fundamental Astronomy) there are 250 Fortran 77 programs.
The web page says…
The SOFA Collection consists of two libraries of routines, one coded in Fortran 77 (the one I downloaded) the other in ANSI C. There is a suite of vector/matrix routines and various utilities that underpin the astronomy algorithms, which include routines for the following:
- Astrometry
- Calendars
- Time Scales
- Ecliptic Coordinates
- Earth Rotation and Sidereal Time
- Ephemerides (medium precision)
- Fundamental Arguments
- Galactic Coordinates
- Geocentric/Geodetic Transformations
- Precession, Nutation and Polar Motion
- Star Catalog Conversion
After running Make. I ran…
bill@bill-MS-7B79:/Fortran/Programs/sofa/20210512/f77/src$ make test
mkdir -p /home/bill/lib/
cp libsofa.a /home/bill/lib/libsofa.a
gfortran -O -Wall t_sofa_f.for -L/home/bill/lib/ -lsofa -o t_sofa_f
./t_sofa_f
T_SOFA_F validation successful
bill@bill-MS-7B79:/Fortran/Programs/sofa/20210512/f77/src$