scepter

Third-Party Notices for SCEPTer

This file summarises third-party software and data notices relevant to SCEPTer source distributions and related packaged artefacts.

It is provided for compliance and transparency. It is not legal advice.

Project licence

SCEPTer is distributed under the GNU General Public License v3.0 or later (GPL-3.0-or-later). See LICENSE for the project notice and LICENSES/ for bundled licence texts.

Core runtime dependencies

Package	Licence	Notes
numpy	BSD-3-Clause
scipy	BSD-3-Clause
astropy	BSD-3-Clause
matplotlib	Matplotlib licence (BSD-compatible)
pandas	BSD-3-Clause
h5py	BSD-3-Clause
shapely	BSD-3-Clause
psutil	BSD-3-Clause
pycraf	GPL-3.0	Some pycraf functionality relies on ITU-derived reference data that may be subject to additional terms, including non-commercial-use restrictions. If you redistribute bundled environments or artefacts that ship pycraf and its data payloads, review those terms explicitly.
cysgp4	GPL-3.0	cysgp4 documents upstream Apache-2.0 and BSD-3-Clause attributions in its own packaged notices.

Optional / full-environment dependencies

The full GUI and notebook environment can also include:

Package	Licence	Category
numba	BSD-2-Clause	GPU acceleration
cupy	MIT	GPU acceleration
PySide6	LGPL-3.0 / GPL-3.0	Desktop GUI
pyvista	MIT	3D visualization (wraps VTK)
pyvistaqt	MIT	3D visualization
vtk (Visualization Toolkit)	BSD-3-Clause	3D rendering engine underlying pyvista / pyvistaqt. See https://vtk.org and the Copyright.txt shipped with the VTK Python wheel for the full upstream notice.
plotly	MIT	Interactive plots
python-kaleido	MIT	Plotly image export
cartopy	BSD-3-Clause	Map projections
tqdm	MPL-2.0 / MIT	Progress bars
ipywidgets	BSD-3-Clause	Notebook widgets
ipykernel	BSD-3-Clause	Jupyter kernel
seaborn	BSD-3-Clause	Statistical plots
ipympl	BSD-3-Clause	Matplotlib in notebooks
trame	Apache-2.0	Remote 3D rendering
trame-vtk	Apache-2.0	VTK backend for Trame
trame-vuetify	Apache-2.0	UI framework for Trame

Before redistributing bundled environments or appliance-style builds, verify the exact licence obligations for the optional dependency set you ship.

Bundled data files

File	Source	Notes
scepter/data/ne_10m_coastline.geojson	Natural Earth	Public domain. Derived from naturalearth.com 1:10m coastline dataset.
scepter/data/ne_10m_land.geojson	Natural Earth	Public domain. Derived from naturalearth.com 1:10m land polygon dataset.
scepter/data/earth_texture_nasa_flat_earth_8192.jpg	NASA/GSFC	See below.
scepter/data/satellite_app_icon.svg	SCEPTer project	GPL-3.0-or-later.
scepter/data/scepter_brand_mark.svg	SCEPTer project	GPL-3.0-or-later.
scepter/data/satellite_app_icon.ico	SCEPTer project	GPL-3.0-or-later.

NASA Earth texture

• File: scepter/data/earth_texture_nasa_flat_earth_8192.jpg
• Source: NASA Goddard Space Flight Center Scientific Visualization Studio (flat_earth_Largest_still.0330.jpg, equirectangular Earth texture).
• Credit: NASA/GSFC Scientific Visualization Studio; Blue Marble Next Generation imagery courtesy of Reto Stockli (NASA/GSFC) and NASA’s Earth Observatory.
• Usage note: Use remains subject to NASA media usage guidance, source-credit expectations, and no-endorsement restrictions. Downstream redistributors should verify how NASA material is treated in the jurisdictions where they distribute or commercialise the software and its bundled assets.

SGP4 propagation — algorithmic and implementation references

SCEPTer’s orbit propagation is carried out by the GPU kernels in scepter/gpu_accel.py and, on the CPU path, by the cysgp4 wrapper around Dan Warner’s C++ SGP4 library. Both paths expose two selectable backends, "vallado" and "dwarner", and both ultimately derive from the same publicly documented SGP4 analytical model.

The SCEPTer source files that implement these kernels are GPL-3.0-or-later (as SCEPTer itself), but the algorithms they implement and the C/C++ reference code against which they are validated come from the upstream works listed below. When you publish scientific results, build validation comparisons, or redistribute SCEPTer-derived binaries, please cite and (where applicable) preserve the upstream attributions.

Original analytical model

Hoots, F. R., & Roehrich, R. L. (December 1980). Models for Propagation of NORAD Element Sets. Project Spacetrack Report No. 3, Aerospace Defense Command (ADC/DO), United States Air Force. Later compiled, redistributed, and corrected by T. S. Kelso (CelesTrak).

• Public archival copy: https://celestrak.org/NORAD/documentation/spacetrk.pdf
• Status: U.S. Government work; effectively public domain. The TLE data format and the SGP4 / SDP4 analytical propagators described here are the foundation for every SGP4 implementation SCEPTer uses.

Modern, corrected reference implementation (the "vallado" backend)

Vallado, D. A., Crawford, P., Hujsak, R., & Kelso, T. S. (2006, with 2012 errata updates). Revisiting Spacetrack Report #3. AIAA/AAS Astrodynamics Specialist Conference, Keystone, Colorado, 21-24 August 2006. Paper AIAA 2006-6753.

• Paper and reference code (C++ / FORTRAN / MATLAB / Pascal): https://celestrak.org/publications/AIAA/2006-6753/
• Mirror / author page: https://www.centerforspace.com/ (David Vallado, CSSI / Kayhan Space) and https://celestrak.org/software/vallado-sw.php.
• Distribution terms: Vallado’s reference code is released for free reuse with attribution; consult the headers in the distributed source files for the exact author statement.
• SCEPTer usage: the GPU "vallado" backend is a numerical re- expression of Vallado’s sgp4.cpp / sgp4unit.cpp arithmetic targeted at CuPy / Numba. The SCEPTer GPU kernels are validated against the CPU output of this reference code.

C++ port used by cysgp4 (the "dwarner" backend)

Warner, Daniel J. — SGP4 C++ library (“dnwrnr/sgp4”).

• Upstream source: https://github.com/dnwrnr/sgp4
• Licence: Apache License 2.0 (see LICENSE in the upstream repository). The Apache-2.0 NOTICE requirements apply when redistributing binaries derived from this source — including the cysgp4 wheels that SCEPTer depends on.
• SCEPTer usage: the CPU propagation path goes through cysgp4, which Cython-wraps Dan Warner’s C++ library. The "dwarner" method name in gpu_accel.py / cysgp4.propagate_many refers to this upstream. The SCEPTer GPU "dwarner" backend mirrors Warner’s arithmetic on the device and is validated against the CPU cysgp4/dnwrnr output.

cysgp4 — the Cython wrapper

Winkel, Benjamin. — cysgp4: a wrapper of Daniel Warner’s SGP4 implementation.

• Upstream source: https://github.com/bwinkel/cysgp4
• Licence: GPL-3.0-or-later. The cysgp4 package ships its own LICENSES/ directory documenting the Apache-2.0 / BSD-3-Clause attributions inherited from the vendored Warner C++ code.
• SCEPTer usage: imported as cysgp4 in scepter/scepter_GUI.py (preview builder, constellation wizard) and scepter/gpu_accel.py (CPU fallback and validation path).

TLE conventions, errata, and reference archive

Kelso, T. S. — CelesTrak.

• https://celestrak.org/
• https://celestrak.org/publications/AIAA/2006-6753/ — co-authored code and errata for the Vallado reference implementation.
• https://celestrak.org/NORAD/documentation/ — SGP4 / TLE documentation archive.
• SCEPTer usage: CelesTrak is the authoritative public reference for TLE field semantics and SGP4 numerical constants; the TLE strings forged by scepter.tleforger follow CelesTrak’s published conventions (2-digit year + day-of-year epoch, column-level field layout, checksum algorithm).

How to cite SCEPTer propagation output

When reporting results that depend on the SCEPTer propagation pipeline, please credit both the analytical model authors (Hoots & Roehrich) and the implementation authors (Vallado et al. for the "vallado" backend, Warner for the "dwarner" backend), together with CelesTrak / Kelso for the reference code and errata. A representative citation block for a SCEPTer-based paper might read:

Satellite ephemerides were propagated with SCEPTer vX.Y.Z using its GPU SGP4 backend (method=”dwarner”), which is a CuPy/Numba re- expression of Daniel Warner’s dnwrnr/sgp4 C++ implementation (Apache-2.0; https://github.com/dnwrnr/sgp4) and is validated against the CPU reference. The underlying analytical model is Hoots & Roehrich (1980), Spacetrack Report #3; the corrected modern reference is Vallado, Crawford, Hujsak & Kelso (2006), AIAA 2006-6753, with CelesTrak-hosted reference code.

Bundled licence texts

The LICENSES/ directory includes reference copies of the main licence texts:

• GPL-3.0-or-later.txt
• BSD-3-Clause.txt
• BSD-2-Clause.txt
• MIT.txt
• MPL-2.0.txt
• Apache-2.0.txt

An ITU-specific licence text is not bundled. Handle any ITU-derived data notices separately, based on the exact data you redistribute.

User-supplied custom antenna patterns

Starting with the custom-antenna-pattern feature (schema scepter_antenna_pattern_format=v1), SCEPTer accepts user-supplied antenna pattern LUTs loaded from JSON files. These files are user data; no licence obligations attach to SCEPTer from the act of loading them.

However, users are responsible for the provenance of LUTs they load. Regulatory masks and vendor datasheets are frequently redistribution-restricted — check the source’s own terms before embedding a pattern in a project JSON you publish or share. ITU-R reference patterns that SCEPTer samples internally (via scepter.analytical_fixtures) come from pycraf and SCEPTer’s own scepter.antenna module and inherit those upstream terms.

Example pattern files bundled under scepter/data/custom_patterns/ are synthetic fixtures generated on the fly from the analytical ITU formulations; they are distributed under the SCEPTer project licence (GPL-3.0-or-later) as fixture data, not as a redistribution of any protected regulatory dataset.

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