Trajectory¶

class heliopy.spice.Trajectory(target)¶

Bases: object

A class for the trajectory of a single body.

Objects are initially created using only the body. To perform the actual trajectory calculation run generate_positions(). The generated positions are then available via. the attributes times, x, y, and z.

Parameters: target (str) – Name of the target. The name must be present in the loaded kernels.

Notes

When an instance of this class is created, a leapseconds kernel and a planets kernel are both automatically loaded.

Attributes Summary

`coords`	A `SkyCoord` object.
`generated`	`True` if positions have been generated, `False` otherwise.
`observing_body`	Observing `Body`.
`r`	Magnitude of position vectors.
`speed`	Speed (magnitude of velocity vectors).
`spice_frame`	The coordinate frame used by SPICE.
`target`	The `Body` whose coordinates are being calculated.
`times`	A `Time` object containing the times sampled.
`velocity`	Velocity.
`vx`	x component of velocity.
`vy`	y component of velocity.
`vz`	z component of velocity.
`x`	x coordinates of position.
`y`	y coordinates of position.
`z`	z coordinates of position.

Methods Summary

`change_units`(unit)	Convert the positions to different units.
`generate_positions`(times, observing_body, frame)	Generate positions from a spice kernel.

Attributes Documentation

coords¶

A SkyCoord object.

Notes

The following frames are supported:

Spice name	SkyCoord class
IAU_SUN	`HeliographicCarrington`

If you need the coordinates in another frame, generate them using the ‘IAU_SUN’ frame and then use transform_to() to transform them into the desired coordinate frame.

generated¶: True if positions have been generated, False otherwise.

observing_body¶: Observing Body. The position vectors are all specified relative to this body.

r¶: Magnitude of position vectors.

speed¶: Speed (magnitude of velocity vectors).

spice_frame¶: The coordinate frame used by SPICE.

target¶: The Body whose coordinates are being calculated.

times¶: A Time object containing the times sampled.

velocity¶

Velocity.

Returned as a shape (n, 3) array, where the n axis is the time axis.

vx¶: x component of velocity.

vy¶: y component of velocity.

vz¶: z component of velocity.

x¶: x coordinates of position.

y¶: y coordinates of position.

z¶: z coordinates of position.

Methods Documentation

change_units(unit)¶

Convert the positions to different units.

Parameters: unit (astropy.units.Quantity) – Must be a unit of length (e.g. km, m, AU).

generate_positions(times, observing_body, frame, abcorr=None)¶

Generate positions from a spice kernel.

Parameters

times (time like) – An object that can be parsed by Time.
observing_body (str or int) – The observing body. Output position vectors are given relative to the position of this body. See https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html for a list of bodies.
frame (str) – The coordinate system to return the positions in. See https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/frames.html for a list of frames.
abcorr (str, optional) – By default no aberration correciton is performed. See the documentaiton at https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/spkezr_c.html for allowable values and their effects.