Satellite CZML

Creates a CZML string based on TLE (Two Line Element set) data for plotting satellites on the open source CesiumJS JavaScript library.

Background

CesiumJS is a WebGL earth modeling engine which allows for time annimated displays of satellites using 3D and 2D interactive maps in the web browser. A CZML file/string is used by CesiumJS to show a time animation such as in this example. Each Two-Line Element set (TLE) contains orbit information for a single satellite. Since satellites drift and maneuver, these become out-of-date and new TLEs must be published. Space-Track.org is an excellent resource for getting up-to-date and historic TLE data via their free API. There is also a spacetrack python package which interfaces with this API for you.

Installation

pip install satellite-czml

Usage

This library contains two classes to aid in the generation of CZML strings.

• satellite_czml - Takes either TLE data or satellite objects and builds CZML string
• satellite - Contains the satellite object that will be used in the CZML generation

For a Jupyter notebook example, please look at example_usage.ipynb. The notebook also contains an example how to use Plotly Dash with Cesium.

Simple Example (one satellite)

tle_list must be a list of lists. Each element is a TLE entry and each TLE entry is broken up into either two or three elements. If the TLE entry is only two elements, a separate name_list must also be provided.

from satellite_czml import satellite_czml

single_tle = [['ISS (ZARYA)',
               '1 25544U 98067A   21016.23305200  .00001366  00000-0  32598-4 0  9992',
               '2 25544  51.6457  14.3113 0000235 231.0982 239.8264 15.49297436265049']]

czml_string = satellite_czml(tle_list=single_tle).get_czml()

Multiple Satellite Example

The same method works with multiple TLE entries

from satellite_czml import satellite_czml

czml_string = satellite_czml(tle_list=multiple_tle).get_czml()

Specifying Argument Lists

from satellite_czml import satellite_czml
from datetime import datetime, timedelta
import random

name_list = [t[0] for t in multiple_tle] 
description_list = ['Station: ' + t[0] for t in multiple_tle]
color_list = [[random.randrange(256) for x in range(3)] for x in range(len(multiple_tle))]
size_list = [7] * len(multiple_tle)

czml_obj = satellite_czml(tle_list=multiple_tle, name_list=name_list, description_list=description_list,
                          color_list=color_list, speed_multiplier=1, use_default_image=False,
                          marker_scale_list=size_list, show_label=False, show_path=False,
                          ignore_bad_tles=True)
czml_string = czml_obj.get_czml()

Create Satellites One-by-One

from satellite_czml import satellite_czml
from satellite_czml import satellite

multiple_sats=[]
for tle in small_tle_list:
    sat = satellite(tle,
                    description='Station: ' + tle[0],
                    color = [random.randrange(256) for x in range(3)],
                    marker_scale=12,
                    use_default_image=False,
                    start_time=datetime.strptime('2020-01-01 00:00:00','%Y-%m-%d %H:%M:%S'),
                    end_time=datetime.strptime('2020-01-01 01:00:00','%Y-%m-%d %H:%M:%S'),
                    show_label=True,
                    show_path=True,
                   )
    multiple_sats.append(sat)

czml_obj = satellite_czml(satellite_list=multiple_sats)
czml_string = czml_obj.get_czml()

Modifying a Satellite

build_* methods, by default, don't rebuild for performance reasons. If you've run get_czml() and need to modify satellites, be sure to pass in the rebuild=true parameter like in the below example.

# czml_obj from above
last_sat_key = list(czml_obj.satellites.keys())[-1]
last_sat = czml_obj.satellites[last_sat_key]

# Change the path to display the orbit path
last_sat.build_path(rebuild=True,
                    show=True,
                    color=[255, 255, 0, 127],
                    width=3
                   )

# Change the label look
last_sat.build_label(rebuild=True,
                     show=True,
                     font='12pt Arial',
                     color=[255, 255, 0, 200],
                     outlineColor=[0, 0, 0, 127],
                     outlineWidth=3,
                    )

# Change the marker (billboard)
last_sat.build_marker(rebuild=True,
                      size=18,
                      outlineColor=[0, 0, 0, 128],
                     )

czml_string = czml_obj.get_czml()

Thank You

Special thanks to Shane Carty, Christian Ledermann and Brandon Rhodes for your work which made this package possible.

This is initially based on Shane Carty's tle2czml python package and uses his motified version of czml.py from Christian Ledermann.

Thanks to Christian Ledermann for his czml python package and for doing the heavy lifting on the CZML creation.

Thanks to Brandon Rhodes for his sgp4 python package and for doing all the complicated orbital calculations so we don't have to.