orbitpy-revised

A Python package (with a C++ base) for computing satellite remote-sensing orbit data. (This is a revision of the package in the orbitpy repository.)

The purpose of OrbitPy is to offer a comprehensive set of classes and functions tailored for Earth Observation mission simulations. Wherever feasible, third-party library classes and functions are leveraged to avoid redundancy. In certain cases, OrbitPy classes act as wrappers around these third-party implementations.

Currently under active development.

Installation

Requires: Unix-like operating system, python 3.13, pip

Create a conda environment and install the dependencies:

conda create -n eosim-revised python=3.13
conda activate eosim-revised
conda install sphinx
pip install sphinx-rtd-theme
pip install pylint
pip install black
pip install coverage
pip install skyfield
pip install astropy

Install the eosimutils package: first download the repository and follow the instructions provided in its README file. This package installs the core utilities required by orbitpy.

Once the repository is set up, run the following command in the terminal to complete the installation of orbitpy:

make install

Developer Notes

This repository is a revamp of the OrbitPy codebase, primarily aimed at removing the dependency on the propcov library. Instead, we will:

• Use the CoverageKinematics library for coverage calculations (added as a submodule).
• Integrate orbit propagators from third-party libraries such as Skyfield and Orekit.
• Use PyBind11 to create Python bindings for C++ implementations in CoverageKinematics.

Challenges & Opportunities

The transition away from propcov presents a challenge because several core OrbitPy utility classes rely on wrapped propcov C++ objects (e.g., propcov.OrbitState, propcov.AbsoluteDate). However, this provides an opportunity to:

• Redesign these classes with a cleaner API.
• Incorporate lessons learned from prior development and use of OrbitPy.
• Improve efficiency and maintainability.

API & Design References

For API design, we will reference the following sources:

• OrbitPy library
  • Key reference: docs/api_reference.rst for high-level descriptions of modules and classes.
• EOSE-API library
• TAT-C schemas
• InstruPy
  • Supports instrument object imports and data metric calculations, while providing default instrument objects.
• SPICE Toolkit
• Cesium CZML
• STK

Coding Guidelines

Each class/function must adhere to the following:

1. Documentation

   • Use Sphinx-style inline comments
   • Provide descriptive documentation and examples. (similar to SPICE).

2. Testing

   • Write unit tests and validation tests.
   • Validation data is sourced from other mission simulators (e.g., GMAT or STK) or real-world datasets (e.g., CYGNSS data).

3. Code Style & Standards

   • Follow a well-defined Styling README.
   • Use Python type hints and follow PEP 8/PEP 257 where applicable.

4. File Handling & Data Structures

   • Favor NumPy arrays for representing trajectories.
   • Use Python dictionaries for data structures instead of niche objects (AstroPy, SpiceyPy).
   • Consider Xarray or Pandas for data indexing.

Major Dependencies

• AstroPy, datetime → Handling time conversions.
• Skyfield → SGP4 propagation, TEME frame transformations, Keplerian elements.
• SPICE (SpiceyPy) → Time and coordinate transformations (preferred over AstroPy for speed).
• Orekit → Numerical orbit propagation.
• SciPy → Rotations and interpolation.
• PyBind11 → Python bindings for C++ code.
• Pydantic? → For enforcing data validation in API.

General Guidelines

• Leverage existing open-source tools whenever possible instead of reinventing functionality.
• Standardize frame and time representations:
  • Frames: ITRF (ECEF), GCRF (ECI).
  • Time systems: UTC, UT1.
• Use the latest stable Python version (currently Python 3.13.2).
• Sphinx will be used for documentation.

Revamping Strategy

1. Catalog Existing Codebase
   • List all classes, functions, and modules in OrbitPy.
   • Identify propcov dependencies that need replacements.

Count:

• Modules: 9
• Classes: 9 + 3 + 4 + 2 + 6 + 2 + 2 + 2 + 2 = 33
• Functions: 7 + 0 + 1 + 2 + 4 + 1 + 0 + 1 + 0 = 16
• Examples: ~10

Total: 58 + 10

2. Establish Development Standards

   • Create a Styling README for code and documentation.

3. Collaborative Review Process

   • Open GitHub discussions for each module/class/function revision.

4. Prototyping & Validation

   • Develop prototypes with unit tests and validation cases.
   • Get reviews before finalizing implementations.

5. Documentation & Examples

   • Generate high-level Sphinx API documentation for each class.
   • Update examples to reflect 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.