orbitpy-revised

Python package (with C++ base) to compute satellite remote-sensing related orbit data. Revision of the OrbitPy package.

Currently under active development.

Developer Notes

This repository is a revamp of the OrbitPy codebase, with the primary objective of removing the dependency on the propcov library. Instead, we will use the CoverageKinematics library for coverage calculations and integrate orbit propagators from third-party libraries, such as Skyfield and Orekit. The CoverageKinematics library will be added as a submodule, and is based on C++, with python bindings using PyBind11.

One challenge in removing the propcov dependency lies in the use of (wrapped) propcov C++ objects by some core utility classes in OrbitPy. For example, classes like propcov.OrbitState and propcov.AbsoluteDate are integral to existing functionality. However, this transition offers an opportunity to redesign and improve these classes (their API), incorporating lessons learned from the development and use of the OrbitPy library.

Guidelines:

We can use the following sources as reference for reformulating the API:

• OrbitPy library
  • Refer to the docs/api_reference.rst (and sub-links within the file) for high-level description of the modules and classes.
• EOSE-API library
• TAT-C schemas
• InstruPy: Support import of instrument objects and datametrics calculation with the InstruPy library, while providing a default instrument object.
• SPICE
• Cesium CZML
• STK

Coding style

Each class/ function is supported with the following:

• Sphinx style inline commenting. Make the comments descriptive and provide examples of implementations. (Check out SPICE documentation.)

• Unit tests, validation.

• Descriptive documentation if required in Sphinx style documentation.

List of major 3rd party dependencies under consideration:

• AstroPy, python datetime for handling time
• Skyfield for SGP4 propagation, coordinate transformations to the TEME frame, conversations of Inertial from/to Keplerian elements.
• SPICE (SpiceyPy) for time, coordinate transformations (favored for its computational speed over AstroPy)
• Orekit for numerical orbit propagation
• SciPy for rotations, interpolation.

Other general guidelines

• We will rely on tested, and well maintained open-source 3rd party software whenever available, instead of trying to recreate the functionality in-house. For example, we can use AstroPy for time related operations, instead of coding in transformations from one time system to another.

• Use and support particular frame, time representations, which are commonly used another third party software, real-world data representation (e.g., CYNGSS data). ITRF for ECEF, J2000 or ICRF for ECI. UTC and UT1 for time.

• Use basic objects for API (python dicitonaries, numpy, and not niche objects such as AstroPy, SpicePY)

• Use the latest stable version of Python at the time of writing (Python 3.13.2).

• Sphinx will be used for documentation.

• Handle file writing by ....

• Use pydantic?

• Favor use of numpy (for representing trajectories). python dictionaries for data sets. numpy for file reading. xarray or pandas for data indexing.

Revamping strategy

• List all the classes and functions in OrbitPy.
• Make a GitHub discussion post for each (revised/ revised) module, class, function.
• Make a prototype of the class/function with a unittest/ validation-test after the discussion and get it reviewed.
• Make a corresponding high-level Sphinx API doc for the class (along with inline Sphinx type documentation).
• Update examples with the revised codebase.

List of classes, functions to be revamped/ developed

orbitpy.util

Classes

• orbitpy.util.StateType
• orbitpy.util.DateType
• orbitpy.util.OrbitState
• orbitpy.util.SpacecraftBus
• orbitpy.util.Spacecraft
• orbitpy.util.GroundStation
• orbitpy.util.SpaceTrackAPI
• orbitpy.util.OrbitPyDefaults
• orbitpy.util.OutputInfoUtility

Functions

• orbitpy.util.helper_extract_spacecraft_params
• orbitpy.util.extract_auxillary_info_from_state_file
• orbitpy.util.dictionary_list_to_object_list
• orbitpy.util.object_list_to_dictionary_list
• orbitpy.util.initialize_object_list
• orbitpy.util.add_to_list
• orbitpy.util.calculate_inclination_circular_SSO

orbitpy.constellation

Classes

• orbitpy.constellation.ConstellationFactory
• orbitpy.constellation.WalkerDeltaConstellation
• orbitpy.constellation.TrainConstellation

orbitpy.propagator

Classes

• orbitpy.propagator.PropagatorFactory
• orbitpy.propagator.J2AnalyticalPropagator
• orbitpy.propagator.SGP4Propagator
• orbitpy.propagator.PropagatorOutputInfo

Functions

• orbitpy.propagator.compute_time_step

orbitpy.grid

Classes

• orbitpy.grid.Grid
• orbitpy.grid.GridOutputInfo

Functions

• orbitpy.grid.GridPoint
• orbitpy.grid.compute_grid_res

orbitpy.coveragecalculator

Classes

• orbitpy.coveragecalculator.CoverageCalculatorFactory
• orbitpy.coveragecalculator.GridCoverage
• orbitpy.coveragecalculator.PointingOptionsCoverage
• orbitpy.coveragecalculator.PointingOptionsWithGridCoverage
• orbitpy.coveragecalculator.SpecularCoverage
• orbitpy.coveragecalculator.CoverageOutputInfo

Functions

• orbitpy.coveragecalculator.helper_extract_coverage_parameters_of_spacecraft
• orbitpy.coveragecalculator.find_in_cov_params_list
• orbitpy.coveragecalculator.filter_mid_interval_access
• orbitpy.coveragecalculator.find_access_intervals

orbitpy.contactfinder

Classes

• orbitpy.contactfinder.ContactFinder
• orbitpy.contactfinder.ContactFinderOutputInfo

Functions

• orbitpy.contactfinder.ContactPairs

orbitpy.eclipsefinder

Classes

• orbitpy.eclipsefinder.EclipseFinder
• orbitpy.eclipsefinder.EclipseFinderOutputInfo

orbitpy.datametricscalculator

Classes

• orbitpy.datametricscalculator.DataMetricsCalculator
• orbitpy.datametricscalculator.DataMetricsOutputInfo

Functions

• orbitpy.datametricscalculator.AccessFileInfo

orbitpy.mission

Classes

• orbitpy.mission.Settings
• orbitpy.mission.Mission

orbitpy.sensorpixelprojection

TBD if time permits.