Time (sbpy.time)

Ephemeris time

References to times in sbpy use the astropy.time.Time class. For consistency with other tools, especially JPL Horizons and NAIF SPICE, sbpy defines an “Ephemeris Time” format as the number of seconds from the J2000 epoch in the TDB scale. To use this enhancement, simply import the sbpy.time sub-module, and pass the format “et” when initializing a Time object:

>>> from astropy.time import Time
>>> import sbpy.time
>>>
>>> j2000 = Time(0, format="et")
>>> j2000.iso
'2000-01-01 12:00:00.000'
>>> Time(759307746.954761, format="et")
<Time object: scale='tdb' format='et' value=759307746.954761>

Or, use the et property to transform dates to ephemeris time:

>>> Time("2010-11-04 13:59:47.31", scale="utc").et
342151253.4925505

The conversion from UTC is thought to be good to the 0.1 ms level. See the sbpy tests for more information.

Reference/API

sbpy.time Module

Classes

SpiceEphemerisTime(val1, val2, scale, ...[, ...])

Number of seconds since J2000.0 epoch.

Class Inheritance Diagram