This function opens an existing PCK ephemeris file in order to append ephemeris data to it, whose pathname is the string pointed to by filename, and returns an ephemeris descriptor associated to it. If the file doesn't exist, or if it isn't a PCK file, the function fails and returns NULL. This file must be compliant to the format specified by the 'SPICE' PCK ephemeris file.

The function writeph_close() must be called to free memory allocated by this function.

The following example appends data to the ephemeris file ephemeris.bpc

t_writephbin *weph;

weph = writeph_pck_open("ephemeris.bpc");
if (weph)
{
  /*
    ...  computation and writing to weph ...
  */
  writeph_close(weph);
}