/* utc_tai.c
********************************************************************************
* utc_tai.c
*
* This set of Julian routines converts between days UTC (Universal time) and
* seconds TAI (Atomic time). The time J2000 refers to noon on January 1, 2000.
*
* RL_FLT8 Jul_TAIofDUTC(dutc)
* converts from days since J2000 UTC to seconds since J2000 TAI.
* RL_INT4 Jul_DUTCofTAI(tai, secs)
* converts from seconds since J2000 TAI to days and seconds since
* J2000 UTC.
*
* Mark R. Showalter, PDS Ring-Moon Systems Node, November 1995
*******************************************************************************/
#include <stdlib.h>
#include <math.h>
#include "julian.h"
#include "fortran.h"
/*
********************************************************************************
* EXPORTED USER ROUTINES
********************************************************************************
*$ Component_name:
* Jul_TAIofDUTC
*$ Abstract:
* Converts a number of days relative to J2000 UTC to a number of seconds
* relative to J2000 TAI.
*$ Keywords:
* JULIAN, TIME, ATOMIC_TIME, UNIVERSAL_TIME
* C, PUBLIC
*$ Declarations:
* RL_FLT8 Jul_TAIofDUTC(dutc)
* RL_INT4 dutc;
*$ Inputs:
* dutc number of days relative to January 1, 2000.
*$ Outputs:
* none
*$ Returns:
* number of seconds since noon J2000 TAI at beginning of day.
*$ Side_effects:
* none
*$ Detailed_description:
* This function converts a number of days relative to J2000 UTC to a
* number of seconds relative to J2000 TAI.
*$ External_references:
* Jul_LeapSecs()
*$ Examples:
* none
*$ Error_handling:
* none
*$ Limitations:
* none
*$ Author_and_institution:
* Mark R. Showalter
* PDS Ring-Moon Systems Node
* NASA/Ames Research Center
*$ Version_and_date:
* 1.0: November 1995
*$ Change_history:
* none
*******************************************************************************/
#define Jul_TAIofDUTC_midnight(dutc) (86400.*(dutc) + Jul_LeapSecs(dutc))
RL_FLT8 Jul_TAIofDUTC(dutc)
RL_INT4 dutc;
{
return Jul_TAIofDUTC_midnight(dutc) - 43200.;
}
/*
********************************************************************************
*$ Component_name:
* Jul_DUTCofTAI
*$ Abstract:
* Returns the day UTC on which a given second TAI falls.
*$ Keywords:
* JULIAN, TIME, ATOMIC_TIME, UNIVERSAL_TIME
* C, PUBLIC
*$ Declarations:
* RL_INT4 Jul_DUTCofTAI(tai, secs)
* RL_FLT8 tai, *secs;
*$ Inputs:
* tai number of seconds relative to J2000 TAI.
*$ Outputs:
* *secs if secs != NULL, the number of seconds into the day
* (0 <= *secs < 86401).
*$ Returns:
* number of days relative to January 1, 2000 on which the second falls.
*$ Side_effects:
* none
*$ Detailed_description:
* This function returns the day UTC on which a given second relative to
* J2000 TAI falls. Optionally, it also returns the number of seconds into
* the given day.
*$ External_references:
* Jul_LeapSecs()
*$ Examples:
* none
*$ Error_handling:
* none
*$ Limitations:
* none
*$ Author_and_institution:
* Mark R. Showalter
* PDS Ring-Moon Systems Node
* NASA/Ames Research Center
*$ Version_and_date:
* 1.0: November 1995
*$ Change_history:
* none
*******************************************************************************/
RL_INT4 Jul_DUTCofTAI(tai, secs)
RL_FLT8 tai, *secs;
{
RL_INT4 dlo, dhi;
RL_FLT8 tlo, thi;
/* Shift time from noon to midnight */
tai += 43200.;
/* Make a guess at the day */
dhi = tai / 86400.;
thi = Jul_TAIofDUTC_midnight(dhi);
/* If it's too low, search upward */
if (thi < tai)
do {
tlo = thi;
dlo = dhi;
dhi = dlo + 1;
thi = Jul_TAIofDUTC_midnight(dhi);
} while (thi <= tai);
/* Otherwise, search downward */
else {
tlo = thi;
dlo = dhi;
while (tlo > tai) {
dlo--;
tlo = Jul_TAIofDUTC_midnight(dlo);
}
}
/* Return the remaining seconds if necessary */
if (secs != NULL) {
*secs = tai - tlo;
}
/* Return the number of days */
return dlo;
}
/*
********************************************************************************
* FORTRAN INTERFACE ROUTINES
********************************************************************************
*$ Component_name:
* FJul_TAIofDUTC
*$ Abstract:
* Converts a number of days relative to J2000 UTC to a number of seconds
* relative to J2000 TAI.
*$ Keywords:
* JULIAN, TIME, ATOMIC_TIME, UNIVERSAL_TIME
* FORTRAN, PUBLIC
*$ Declarations:
* real*8 function FJul_TAIofDUTC(dutc)
* integer*4 dutc
*$ Inputs:
* dutc number of days relative to January 1, 2000.
*$ Outputs:
* none
*$ Returns:
* number of seconds since noon J2000 TAI at beginning of day.
*$ Side_effects:
* none
*$ Detailed_description:
* This function converts a number of days relative to J2000 UTC to a
* number of seconds relative to J2000 TAI.
*$ External_references:
* none
*$ Examples:
* none
*$ Error_handling:
* none
*$ Limitations:
* none
*$ Author_and_institution:
* Mark R. Showalter
* PDS Ring-Moon Systems Node
* NASA/Ames Research Center
*$ Version_and_date:
* 1.0: November 1995
*$ Change_history:
* none
*******************************************************************************/
RL_FLT8 FORTRAN_NAME(fjul_taiofdutc) (dutc)
RL_INT4 *dutc;
{
return Jul_TAIofDUTC(*dutc);
}
/*
********************************************************************************
*$ Component_name:
* FJul_DUTCofTAI
*$ Abstract:
* Returns the day UTC on which a given second TAI falls.
*$ Keywords:
* JULIAN, TIME, ATOMIC_TIME, UNIVERSAL_TIME
* FORTRAN, PUBLIC
*$ Declarations:
* integer*4 function FJul_DUTCofTAI(tai, secs)
* real*8 tai, secs
*$ Inputs:
* tai number of seconds relative to J2000 TAI.
*$ Outputs:
* secs the number of seconds into the day (0 <= secs < 86401).
*$ Returns:
* number of days relative to January 1, 2000 on which the second falls.
*$ Side_effects:
* none
*$ Detailed_description:
* This function returns the day UTC on which a given second relative to
* J2000 TAI falls. It also returns the number of seconds into the given
* day.
*$ External_references:
* none
*$ Examples:
* none
*$ Error_handling:
* none
*$ Limitations:
* none
*$ Author_and_institution:
* Mark R. Showalter
* PDS Ring-Moon Systems Node
* NASA/Ames Research Center
*$ Version_and_date:
* 1.0: November 1995
*$ Change_history:
* none
*******************************************************************************/
RL_INT4 FORTRAN_NAME(fjul_dutcoftai) (tai, secs)
RL_FLT8 *tai, *secs;
{
return Jul_DUTCofTAI(*tai, secs);
}
/*******************************************************************************
*/