This function writes in sequential mode a type 12 segment (discrete states of the positions and velocities, Hermite interpolation with equal timesteps) to the SPK file associated to the ephemeris descriptor eph.

The states array must be of size record_count*6 and have the following structure :

X coord 1st record	Y coord 1st record	Z coord 1st record	dX 1st record	dY 1st record	dZ 1st record
...	...	...	...	...	...
X coord (record_count)th record	Y coord (record_count)th record	Z coord (record_count)th record	dX (record_count)th record	dY (record_count)th record	dZ (record_count)th record

The following example creates a new ephemeris file ephemeris.bsp with segment of type 12 for the heliocentric coordinates of Venus.

USE, INTRINSIC :: ISO_C_BINDING
use calceph
TYPE(C_PTR) :: weph
INTEGER len_timespan
REAL(8) :: jd_start, jd_end, jd
INTEGER frame, record_count, interpolation_degree, k, ret
REAL(8), dimension(600) :: pos_vel !  size = 600 = record_count * 6 components

len_timespan = 32 ! days
frame = 1 ! ICRF
record_count = 100
interpolation_degree = 7
jd_start = 2460000
jd_end = jd_start+record_count*len_timespan

weph = writeph_spk_create("ephemeris.bsp"//C_NULL_CHAR, "planet_2"//C_NULL_CHAR,0)
if (C_ASSOCIATED(weph)) then

     do k=0, record_count-1
          jd = jd_start+k*len_timespan;
          ! ... fill the array pos_vel with the positions and velocities at the date jd  ...
          ! pos_vel(...) =...
     enddo
     ret = writeph_spk12_seq_write(weph, NAIFID_VENUS, NAIFID_SUN, frame, jd_start, 0.0, jd_end, 0.0,
                    len_timespan, pos_vel, record_count, interpolation_degree, "seg_planet"//C_NULL_CHAR)

     call writeph_close(weph)
endif