This is cross-posted from a Physics SE question in case people there do not use poliastro very often/much. Please check there prior to answering here in case it has already been overcome by events.
The Python poliastro package documentation states that, when propagating from position and velocity vectors, the orbit's reference frame will be "one pseudo-inertial frame around the attractor," which means a form of ECI when Earth is the attractor. However, I want to make sure its epoch is the same as that specified by the IERS.
I have already checked answers to a similar post and found the clarity to be lacking. I want a specific answer in this case from someone who has used poliastro in the following form:
from astropy import units
from poliastro.bodies import Earth
from poliastro.twobody import Orbit
from poliastro.twobody.propagation import kepler
ephemerisPosition = (ephemerisPosition * units.earthRad).to(units.meter)
ephemerisVelocity = (ephemerisVelocity *units.earthRad / units.day).to(units.meter / units/second)
seconds = ephememerisStart + secondsOffset
for i, time in enumerate(seconds):
ss = Orbit.from_vectors(Earth, ephemerisPosition, ephemerisVelocity).propagate(time * units.second, method=kepler)
There are several open issues at GitHub/poliastro related to how poliastro treated reference frames. It appears that poliastro is trying to use a Geocentric Celestial Reference System (GCRS) as its Earth Centered Inertial frame of reference. From looking at the code in the poliastro master branch and from looking at the many open issues related to reference frames, I would call what they use is pseudo-GCRS frame.
GCRS is, by definition, a relativistically correct frame of reference. Poliastro is fully Newtonian. It ignores speed of light issues. It ignores the difference between Terrestrial Time (TT) and Barycentric Dynamical Time (TDB). It ignores geodesic precession. It ignores lots of things. The combination of the above is why I wrote that poliastro uses a pseudo-GCRS frame for its Earth Centered Inertial frame.