# spacepy.pybats.SatOrbit

class `spacepy.pybats.``SatOrbit`(filename=None, *args, **kwargs)

  An class to load, read, write, and handle BATS-R-US satellite orbit input files. These files are used to fly virtual satellites through the MHD domain. Note that the output files should be handled by the `LogFile` and not this satorbit object. The object’s required and always present attributes are:

  Attribute | Description
  --- | ---
  head | A list of header lines for the file that contain comments.
  coor | The three-letter code (see SWMF doc) of the coord system.
  file | Location of the file to read/write.

  The object should always have the following two data keys:

  Key | Description
  --- | ---
  time | A list or numpy vector of datetime objects
  xyz | A 3 x len(time) numpy array of x,y,z coordinates associated with the time vector.

  A “blank” instantiation will create an empty object for the user to fill. This is desired if the user wants to create a new orbit, either from data or from scratch, and save it in a properly formatted file. Here’s an example with a “stationary probe” type orbit where the attributes are filled and then dropped to file:

      >>> from spacepy.pybats import SatOrbit
      >>> import datetime as dt
      >>> import numpy as np
      >>> sat = SatOrbit()
      >>> sat['time'] = [ dt.datetime(2000,1,1), dt.datetime(2000,1,2) ]
      >>> pos = np.zeros( (3,2) )
      >>> pos[:,0]=[6.6, 0, 0]
      >>> pos[:,1]=[6.6, 0, 0]
      >>> sat['xyz'] = pos
      >>> sat.attrs['coor'] = 'SMG'
      >>> sat.attrs['file'] = 'noon_probe.dat'
      >>> sat.write()

  If instantiated with a file name, the name is loaded into the object. For example,

      >>> sat=SatOrbit('a_sat_orbit_file.dat')

  …will populate all fields with the data in a_sat_orbit_file.dat.