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Now the C version of Astronomy Engine supports calculating the Earth/Moon Barycenter (EMB) state vector (position and velocity) relative to the Earth's center (geocentric) or relative to the Solar System Barycenter (SSB). Astronomy_BaryState() now supports body == BODY_EMB. Added a new function Astronomy_GeoEmbState() to calculate the geocentric state for the EMB. Both have been verified using test data generated by JPL Horizons.
Data for testing barycentric state calculation.
This JPL Horizons data is for testing calculation of the barycentric state
(position and velocity vectors) using the Astronomy Engine BaryState function.
There are test files for all the supported bodies.
The files use varying start time, stop time, and time step values,
but they are otherwise configured the same.
As an example, here is the batch data for generating Sun.txt:
!$$SOF
COMMAND= '10'
CENTER= '500@0'
MAKE_EPHEM= 'YES'
TABLE_TYPE= 'VECTORS'
START_TIME= '1900-01-01'
STOP_TIME= '2100-01-01'
STEP_SIZE= '20 d'
OUT_UNITS= 'AU-D'
REF_PLANE= 'FRAME'
REF_SYSTEM= 'J2000'
VECT_CORR= 'NONE'
VEC_LABELS= 'YES'
VEC_DELTA_T= 'NO'
CSV_FORMAT= 'NO'
OBJ_DATA= 'YES'
VEC_TABLE= '2'
!$$EOF