Expand description
Form the matrix of bias-precession-nutation (IAU 2006/2000A)
Arguments
epoch = double (Returned) Julian epoch for mean coordinates. date = double (Returned) Modified Julian Date (JD-2400000.5) for true coordinates. rmatpn = double[3][3] (Returned) combined NPB matrix
Description
Form the matrix of bias-precession-nutation (IAU 2006/2000A). The epoch and date are TT (but TDB is usually close enough). The matrix is in the sense v(true) = rmatpn * v(mean).
Original: https://github.com/Starlink/pal/blob/master/palPrenut.c
Safety
epoch, date, and rmatpn will be modified.