Satellite Situation Center (SSCWeb)

SSCWeb provides trajectories for solar system objects such as planets, moons, and spacecraft in different coordinate systems. Its integration into Speasy makes it easy to get any available trajectory for any time range.

Basics: Getting data from SSCWeb module

First, check that the trajectory you want is available. The easiest way is to browse Speasy’s dynamic inventory, which is always up to date:

>>> import speasy as spz
>>> ssc_trajectories = spz.inventories.flat_inventories.ssc.parameters
>>> # hundreds of spacecraft are available, keyed by their id
>>> 'ace' in ssc_trajectories
True
>>> len(ssc_trajectories) > 100
True

Note that you can also use your python terminal completion and browse spz.inventories.data_tree.ssc.Trajectories to find your trajectory. Once you have found your trajectory, you can choose the coordinate system for the download. The default is gse.

>>> import speasy as spz
>>> # Let's assume you wanted to get MMS1 trajectory
>>> mms1_traj = spz.ssc.get_data(spz.inventories.data_tree.ssc.Trajectories.mms1, "2018-01-01", "2018-02-01", 'gsm')
>>> mms1_traj.columns
['X', 'Y', 'Z']
>>> mms1_traj.values
array([[57765.7789, 39928.6469, 36127.6976],
       [57636.7873, 39912.6769, 36075.1812],
       [57507.6709, 39896.6512, 36022.4395],
       ...,
       [74135.0437,   741.7233, 27240.7339],
       [74007.2467,   795.057 , 27220.3705],
       [73879.1839,   848.3518, 27199.876 ]], shape=(44640, 3))

Coordinate systems

Pass one of these as the coordinate_system argument. The frame the service actually returned is also echoed back in the variable’s metadata, which is the reliable way to check what you got:

>>> mms1_traj.meta['CoordinateSystem']
'GSM'

Value	Coordinate system
`geo`	Geographic: Z along the Earth’s rotation axis, X in the equatorial plane through the Greenwich meridian. Rotates with the Earth.
`gm`	Geomagnetic: Z along the Earth’s magnetic dipole axis, X in the plane containing the dipole and rotation axes.
`gse`	Geocentric Solar Ecliptic: X towards the Sun, Z normal to the ecliptic plane (default).
`gsm`	Geocentric Solar Magnetospheric: X towards the Sun, the X-Z plane containing the magnetic dipole axis.
`sm`	Solar Magnetic: Z along the magnetic dipole axis, Y perpendicular to the plane containing the dipole axis and the Earth-Sun line.
`geitod`	Geocentric Equatorial Inertial, true of date: X towards the vernal equinox and Z along the rotation axis, both at the date of the data.
`geij2000`	Geocentric Equatorial Inertial, referred to the mean equator and equinox of epoch J2000.0.

Note

This list reflects what SSCWeb offered at the time of writing and may not be up to date. See the SSCWeb documentation for the authoritative list and the precise definitions.