Reference Frames

Coordinate reference frames and ephemeris data.

Supported Frames

Inertial Frames

Abbreviation	Name	Description
ICRF	International Celestial Reference Frame	Primary inertial frame
J2000	J2000 Mean Equator and Equinox	FK5-compatible inertial frame (alias: EME2000)

CIO-Based Frames (IAU2006/IERS2010)

Abbreviation	Name	Description
CIRF	Celestial Intermediate Reference Frame	CIO-based celestial frame
TIRF	Terrestrial Intermediate Reference Frame	CIO-based terrestrial frame
ITRF	International Terrestrial Reference Frame	Earth-fixed

Equinox-Based Frames

Abbreviation	Name	Description
MOD	Mean of Date	Precessed frame (default: IERS1996)
TOD	True of Date	Precessed + nutated frame (default: IERS1996)
PEF	Pseudo-Earth Fixed	Includes Earth rotation (default: IERS1996)
TEME	True Equator Mean Equinox	Used by SGP4/TLE

Equinox-based frames accept an IERS convention suffix, e.g. MOD(IERS2003), TOD(IERS2010). The bare forms (MOD, TOD, PEF) default to IERS1996.

Body-Fixed Frames

Abbreviation	Name	Description
IAU_EARTH	IAU Earth	Earth body-fixed frame
IAU_MOON	IAU Moon	Moon body-fixed frame
IAU_BODY	IAU body-fixed	Available for all bodies with defined rotational elements

Quick Example

import lox_space as lox

# Create a frame
icrf = lox.Frame("ICRF")
itrf = lox.Frame("ITRF")

# Load ephemeris data
spk = lox.SPK("/path/to/de440.bsp")

# Transform states between frames
state_icrf = state.to_frame(itrf, provider=eop_provider)

# Transform between origins
state_moon = state.to_origin(lox.Origin("Moon"), spk)

Frame

Represents a reference frame for positioning and transformations.

Supported frames: - ICRF: International Celestial Reference Frame (inertial) - GCRF: Geocentric Celestial Reference Frame (inertial, Earth-centered) - CIRF: Celestial Intermediate Reference Frame - TIRF: Terrestrial Intermediate Reference Frame - ITRF: International Terrestrial Reference Frame (Earth-fixed) - Body-fixed frames: IAU_EARTH, IAU_MOON, IAU_MARS, etc.

Parameters:

abbreviation
–

Frame abbreviation (e.g., "ICRF", "ITRF", "IAU_MOON").

Raises:

ValueError –

If the frame abbreviation is not recognized.

Examples:

>>> icrf = lox.Frame("ICRF")
>>> itrf = lox.Frame("ITRF")

Methods:

abbreviation –

Return the abbreviation of this reference frame.
name –

Return the full name of this reference frame.

abbreviation

abbreviation() -> str

Return the abbreviation of this reference frame.

name

name() -> str

Return the full name of this reference frame.

SPK

SPICE SPK (Spacecraft and Planet Kernel) ephemeris data.

SPK files contain position and velocity data for celestial bodies and spacecraft. They are used for orbit propagation, frame transformations, and visibility analysis.