s00¶
- erfa.s00(date1, date2, x, y)[source]¶
The CIO locator s, positioning the Celestial Intermediate Origin on the equator of the Celestial Intermediate Pole, given the CIP’s X,Y coordinates.
- Parameters:
- date1double array
- date2double array
- xdouble array
- ydouble array
- Returns:
- c_retvaldouble array
Notes
Wraps ERFA function
eraS00
. The ERFA documentation is:- - - - - - - e r a S 0 0 - - - - - - - The CIO locator s, positioning the Celestial Intermediate Origin on the equator of the Celestial Intermediate Pole, given the CIP's X,Y coordinates. Compatible with IAU 2000A precession-nutation. Given: date1,date2 double TT as a 2-part Julian Date (Note 1) x,y double CIP coordinates (Note 3) Returned (function value): double the CIO locator s in radians (Note 2) Notes: 1) The TT date date1+date2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TT)=2450123.7 could be expressed in any of these ways, among others: date1 date2 2450123.7 0.0 (JD method) 2451545.0 -1421.3 (J2000 method) 2400000.5 50123.2 (MJD method) 2450123.5 0.2 (date & time method) The JD method is the most natural and convenient to use in cases where the loss of several decimal digits of resolution is acceptable. The J2000 method is best matched to the way the argument is handled internally and will deliver the optimum resolution. The MJD method and the date & time methods are both good compromises between resolution and convenience. 2) The CIO locator s is the difference between the right ascensions of the same point in two systems: the two systems are the GCRS and the CIP,CIO, and the point is the ascending node of the CIP equator. The quantity s remains below 0.1 arcsecond throughout 1900-2100. 3) The series used to compute s is in fact for s+XY/2, where X and Y are the x and y components of the CIP unit vector; this series is more compact than a direct series for s would be. This function requires X,Y to be supplied by the caller, who is responsible for providing values that are consistent with the supplied date. 4) The model is consistent with the IAU 2000A precession-nutation. Called: eraFal03 mean anomaly of the Moon eraFalp03 mean anomaly of the Sun eraFaf03 mean argument of the latitude of the Moon eraFad03 mean elongation of the Moon from the Sun eraFaom03 mean longitude of the Moon's ascending node eraFave03 mean longitude of Venus eraFae03 mean longitude of Earth eraFapa03 general accumulated precession in longitude References: Capitaine, N., Chapront, J., Lambert, S. and Wallace, P., "Expressions for the Celestial Intermediate Pole and Celestial Ephemeris Origin consistent with the IAU 2000A precession- nutation model", Astron.Astrophys. 400, 1145-1154 (2003) n.b. The celestial ephemeris origin (CEO) was renamed "celestial intermediate origin" (CIO) by IAU 2006 Resolution 2. McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), IERS Technical Note No. 32, BKG (2004) This revision: 2021 May 11 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.