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Fix tt2tdb() period and improve precision #35

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merged 2 commits into from
Jun 29, 2024
Merged

Fix tt2tdb() period and improve precision #35

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b868ae4
tt2tdb() had a wrong scaling in the period
attipaci Jun 29, 2024
212abc8
Adjust reference data
attipaci Jun 29, 2024
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18 changes: 15 additions & 3 deletions src/novas.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5178,9 +5178,14 @@ int tdb2tt(double jd_tdb, double *jd_tt, double *secdiff) {
* Returns the TDB - TT time difference in seconds for a given TT date.
*
*
* Note, as of version 1.1, it uses the same calculation as the more precise original tdb2tt().
*
*
* REFERENCES
* <ol>
* <li><a><href="https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems">
* <li><a href="https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html#The%20Relationship%20between%20TT%20and%20TDB">
* https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html</a>
* <li><a href="https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems">
* https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems</a>
* </li>
* </ol>
Expand All @@ -5194,9 +5199,16 @@ int tdb2tt(double jd_tdb, double *jd_tt, double *secdiff) {
* @author Attila Kovacs
*/
double tt2tdb(double jd_tt) {
double dt;

tdb2tt(jd_tt, NULL, &dt);
return dt;

/*
const double t = (jd_tt - JD_J2000) / JULIAN_CENTURY_DAYS;
const double g = TWOPI * (357.528 + 35999.050 * t) * DEGREE;
return 0.001658 * sin(g + 0.0167 * sin(g));
const double g = 6.239996 + 630.0221385924 * t;
return 0.001657 * sin(g + 0.01671 * sin(g));
*/
}

/**
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2 changes: 1 addition & 1 deletion test/reference/rad_vel.out
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Expand Up @@ -135,7 +135,7 @@

-10000.0 SUN S0 O1 A1: -23.440742

-10000.0 SUN S0 O2 A1: 14.828582
-10000.0 SUN S0 O2 A1: 14.828581

-10000.0 EARTH S0 O0 A1: -0.246770

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