$LastChangedDate: 27-Juil-2011 $

# CL_mod_sidTime

Greenwich mean sideral time (IERS 1996)

## Calling Sequence

       [gmst,[gmstp]]=CL_mod_sidTime(cjd_ut1)

## Description

- Computes the Greenwich mean sideral time gmst (IERS standard 1996).

  It also optionally computes the first derivative of the sideral time : gmstp. (this value is not a constant)

## Parameters

cjd_ut1:

  Modified (1950.0) Julian day, in UT1 time scale (1xN)

gmst :

  Greenwich mean sideral time [rad]

gmstp :

  Greenwich mean sideral time first derivative [rad/s]

## Authors

- CNES - DCT/SB

## Bibliography

- 1) IERS Conventions (1996), Dennis D. McCarthy

## See also

- CL_mod_sidTimeG50

## Examples

    cjd_utc = CL_dat_cal2cjd(2008,10,25,15,30,25)  // 25 oct 2008 at 15h30min25s
    sec_ut1_minus_utc = 0.2;
    cjd_ut1 = cjd_utc + sec_ut1_minus_utc/86400.;  // ut1 time
    gmst = CL_mod_sidTime(cjd_ut1);
    [gmst,gmstp] = CL_mod_sidTime(cjd_ut1);

    // With first time derivative :
    [gmst,gmstp] = CL_mod_sidTime(21915.121212)