FUNCTION c_daynite (jdate, year, tsec, plat, plong, sunzen, dayn)
long *jdate; long *year; double *tsec; double *plat; double *plong; double *sunzen; long *dayn;
The julian date of the pass.
The year of the pass (ie. 94 for 1994).
The time at the point specified by plat and plong. This time specifies total seconds since midnight GMT.
The latitude of the point within the scene.
The longitude of the point within the scene.
The computed solar zenith angle.
= 1: Day pass = -1: Night pass
Given the date, time, and location within a scene, c_daynite() calculates the solar zenith angle at this location and determines if the image is a day or night pass (a solar zenith angle between zero and ninety degrees constitutes a day pass).
c_daynite() has no return value.