# Data sources and terms

The Apache License 2.0 applies to project-owned software only. It does not
relicense astronomical kernels, downloaded ephemerides or generated data.

## JPL DE440s

The calculation-core distribution contains an unmodified `de440s.bsp` obtained
from the NASA/JPL Navigation and Ancillary Information Facility:

https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/planets/de440s.bsp

Expected SHA-256:

`C1C7FEEAB882263FC493A9D5A5B2DDD71B54826CDF65D8D17A76126B260A49F2`

NAIF permits redistribution of kernels distributed by NAIF when they are not
modified. Commercial use of SPICE components is permitted subject to the NAIF
rules:

https://naif.jpl.nasa.gov/naif/rules.html

NASA, JPL, Caltech and NAIF provide the kernel and related material without
warranty. Users bear the risk of selecting and using suitable kernels.

## Horizons N16 asteroid data

The public calculation-core package does not contain a precomputed N16 state
table or object-specific Horizons SPKs.

The optional N16 generator retrieves object-specific SPK data directly from the
JPL Horizons API at the user's explicit request and creates a local
`n16-states-f64.bin` table:

https://ssd-api.jpl.nasa.gov/doc/horizons.html

The generated manifest records the source endpoint, object identifiers,
coverage, units, checksums and generator version.

Downloaded SPKs and the locally generated N16 table are not relicensed under
Apache License 2.0 by this project. Users are responsible for checking and
complying with the applicable JPL/Horizons terms before redistributing those
files or derived data.

## Validation material

Project validation reports may contain numerical comparisons against public
JPL Horizons or other astronomical services. They are not runtime data and are
identified by source and generation date in the corresponding report.
