oacmpy 0.0.3

Parse CCSDS Data Message, including OEM, AEM and CDM, and convert them to a CZML scenario file.

oacmpy

Description

The object of oacmpy is currently two-fold:

• to parse CCSDS Data Message files and,
• to convert them to CZML file for cesium 3d mapping framework.

CCSDS is a standard for communicating satellite data between operators, but it is generally widely used for any flight dynamics software, and library orekit. (see also odmpy and orekit for python). Here, Data Messages include broadly the Navigation Data Messages but also Conjunction Data Message (CDM). Tracking Data Message (TDM) will not be implemented.

The idea behind oacmpy is to keep current tools interfaces. Rather than updating tools with specific CZML features, this module creates the files for Cesium, from your standardized output files. The generated CZML file is customizable and allow showing:

• display trajectory (through OEM)
• illustrating spacecraft attitude motion (through AEM)
• showing close encounter (through CDM)

The approach is different than the use of TLE as no propagation is performed here. The propagation (and hence its accuracy and fidelity) is down to the tool used to generate the initial ephemeris file.

Usage

Extracting data from Data Messages

OEM

from oacmpy import ccsds

oem = cc.Oem.Oem("oem.xml", "xml")
oem.get_satellite_list()
oem.get_ephemeris("SATELLITE NAME")  # array list of epoch - position/velocity vectors
oem.get_covariances("SATELLITE NAME")  # array list of covariance parameter

Covariance data can be extracted like,

cov_data = oem.get_covariances("SATELLITE NAME")[0]
cov_data.get_epoch()  # covariance epoch
cov_data.get_reference_frame() # covariance reference frame
cov_date.get_covariance_matrix()  # covariance matrix

AEM (Attitude file)

aem = ccsds.Aem.Aem("aem.txt", "kvn")
aem.get_satellite_list()
aem.get_attitudes("SATELLITE NAME")  # array list of epoch - quaternions 

CMD (Conjunction file)

cdm = ccsds.Cdm.Cdm("cdm.xml", "xml") # conjunction event    
cdm.get_satellite_list()
cdm.get_tca()
cdm.get_miss_distance()
cdm.get_probability()

Generation of CZML

The generation of CZML script for use with Cesium is the main purpose of this lib. You can ingest different CCSDS data file (e.g., OEM, AEM or CDM) and create a Cesium scene description. This can be helpful to illustrate satellite trajectory or satellite conjunctions.

From Python Console

Create the CZML from OEM and AEM:

from oacmpy.czml import CdmToCzml, OemToCzml, ScenarioCzml 
oem1_czml = OemToCzml.OemAemToCzml(oem1, aem1)  # aem1 is optional

Add conjunction event with CDM:

cdm_czml = CdmToCzml.CdmToCzml(cdm)

Generate CZML file:

start = oem1.get_start_time("SATELLITE NAME").datetime
end = oem1.get_stop_time("SATELLITE NAME").datetime

scenario = ScenarioCzml.ScenarioCzml(start, end)
scenario.add_content(oem1_czml.dump())
scenario.add_content(oem2_czml.dump())
scenario.add_content(cdm_czml.dump())
scenario.create_document([], "scenario.czml")

Plotting attributes are customizable, e.g., changing color, material, line with, etc.

Command line tool

If you have an OEM file and you do not bother about attitude, or configuring the graphics, you can simply run:

python -m aocmpy -i [your-oem-file] -o [output-file.czml]   

[your-oem-file] can include wildcard to process several OEM into a single CZML file. The file format (KVN or XML) of the OEM file will be guessed with the file extension.

.. image:: ./example/screenshot.png

Testing

Run unit tests with

python -m unittest discover --start-directory ../tests

References

• Orbit Data Messages, CCSDS 502.0-B-2, Nov 2009
• Attitude Data Messages, CCSDS 504.0-B-1, May 2008
• Conjunction Data Messages, CCSDS 508.0-B-1, June 2013
• XML SPECIFICATION FOR NAVIGATION DATA MESSAGES, CSDS 505.0-B-1, December 2010