    +-----------------------------------------------------------------------------+
    |  __   __   __      __   __     __   ___     __   ___  __          __   ___  |
    | /__\ /__` '__\    /__` |__) | /  ` |__     /__` |__  |__) \  / | /  ` |__   |
    | \__, .__/ \__/    .__/ |    | \__, |___    .__/ |___ |  \  \/  | \__, |___  |
    |                                                                             |
    | The GNSS SPICE Kernel Dataset                                               |
    +-----------------------------------------------------------------------------+

       Last update: February 24, 2023

    Introduction
    ============

       This document describes the GNSS SPICE kernel dataset (SKD)
       containing observation geometry and other ancillary data in the form of
       SPICE System kernel files for the GNSS spacecraft, its instruments
       and targets. It describes the dataset directory structure,
       kernels included in the dataset, their naming conventions, and provides
       pointers to the SPICE software and documentation.

    Table of Contents
    =================

       Introduction
       Table of Contents
       Overview
       Errata
       Archive Contents
       Kernel Types
       Kernel Details
          SPK Files
          PCK Files
          IK Files
          CK Files
          DSK Files
          LSK Files
          SCLK Files
          FK Files
          MK Files
          ORBNUM Files
       SKD Latest Release Notes
       SPICE Software and Documentation
       Contact Information

    Overview
    ========

       This archive includes the complete set of GNSS SPICE data files
       (kernel files), which can be accessed using SPICE software. The
       SPICE data contain geometric and other ancillary information needed
       to recover the full value of science instrument data. In particular
       SPICE kernels provide spacecraft and planetary ephemeris,
       spacecraft and instrument orientation, instrument mounting
       alignments, and data needed for relevant time conversions. Data in
       the SPICE kernel files must be accessed using the software called
       the SPICE Toolkit produced and distributed by the Navigation and
       Ancillary Information Facility (NAIF) Node of the Planetary Data
       System.

       This archive includes data covering from GNSS launch,
       through the end time of the latest spacecraft orientation file
       supplied in the archive. Until the end of the spacecraft lifespan
       this archive will be accumulating with new data added according to
       the project archiving plan.

    Back to Table of Contents

    Errata
    ======

       None.

    Back to Table of Contents

    SPICE Kernel Dataset Contents
    =============================

       Files in this archive are organized into a set of subdirectories
       below the top-level directory. The following diagram shows the
       structure and content of these directories. The directory names are
       enclosed in square brackets ([]).

       [gnss]                        Top-level directory
       |
       |-[kernels]                           Directory containing SPICE kernels.
       | |
       | |- aareadme.txt                     SPICE Kernel Dataset top-level readme file.
       | |
       | |-[ck]                              Directory containing CK files.
       | | |
       | | |-- *.BC                          Binary CK files.
       | | +-- *.txt                         CK readme file.
       | |
       | |-[dsk]                             Directory containing DSK files.
       | | |
       | | |-- *.BDS                         Binary DSK files.
       | | |-- *.OBJ                         Geometry definition file generated from a DSK.
       | | |-- *.PNG                         Graphic file from an OBJ file.
       | | +-- *.txt                         DSK readme file.
       | |
       | |-[fk]                              Directory containing FK files.
       | | |
       | | |-- *.TF                          Text FK files.
       | | +-- *.txt                         FK readme file.
       | |
       | |-[ik]                              Directory containing IK files.
       | | |
       | | |-- *.TI                          Text IK files.
       | | +-- *.txt                         IK readme file.
       | |
       | |-[lsk]                             Directory containing LSK files.
       | | |
       | | |-- *.TLS                         Text LSK files.
       | | +-- *.txt                         LSK readme file.
       | |
       | |--[mk]                             Directory containing MK files.
       | | |
       | | |-- *.TM                          Text Meta-kernel files.
       | | +-- *.txt                         MK readme file.
       | |
       | |--[orbnum]                         Directory containing ORBNUM files.
       | | |
       | | |-- *.ORBNUM                      Text ORBNUM files.
       | | +-- *.txt                         ORBNUM readme file.
       | |
       | |-[pck]                             Directory containing PCK files.
       | | |
       | | |-- *.TPC                         Text PCK files.
       | | |-- *.BPC                         Binary PCK files.
       | | +-- *.txt                         PCK readme file.
       | |
       | |-[sclk]                            Directory containing SCLK files.
       | | |
       | | |-- *.TSC                         Text SCLK files.
       | | +-- *.txt                         SCLK readme file.
       | |
       | +-[spk]                             Directory containing SPK files.
       |   |
       |   |-- *.BSP                         Binary SPK files.
       |   +-- *.txt                         SPK readme file.
       |
       +-[misc]                              Directory containing miscellaneous documents.
         |
         |-[release_notes]                   Directory containing release notes.
         |   |
         |   +-- *.txt                       Release notes files.
         |
         |-[cosmo]                           Directory containing SPICE-Enhanced
         |    |                              Cosmographia configuration files.
         |    |
         |    |-[config]                     Directory containing configuration files
         |    |  |                           for the spacecraft(s) and the SPICE kernels used.
         |    |  |
         |    |  +-- *.json                  JSON configuration files.
         |    |
         |    |-[models]                     Directory containing 3D models for the spacecraft(s).
         |    |  |
         |    |  |-- *.3ds                   3D Studio models.
         |    |  |-- *.cmod                  Celestia models.
         |    |  +-- *.jpg                   Texture for the models
         |    |
         |    |-[observations]               Directory containing observations.
         |    |  |
         |    |  +-- *.json                  JSON observation files.
         |    |
         |    |-[scenarios]                  Directory containing scenarios definitions.
         |    |  |
         |    |  +-- *.json                  JSON scenario files.
         |    |
         |    |-[sensors]                    Directory containing sensor configurations.
         |    |  |
         |    |  +-- *.json                  JSON sensor files.
         |    |
         |    +-[scripts]                    Directory containing scripts.
         |       |
         |       |-- *.py                    Python files.
         |       |-- *.csh                   Bash files for Unix/MAC.
         |       +-- *.bat                   Batch files for Windows.
         |
         |-[deprecated_kernels]              Directory that replicates the kernels
         |                                   directory with deprecated kernels.
         |
         |-[skd]                             Directory that contains a zipped directory
         |   |                               with the latest sub-set of the
         |   |                               SPICE Kernel Dataset from the meta-kernels
         |   |
         |   +-- *.zip                       Zipped directory.
         |
         +-gnss.html                 This file.

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    Kernel Types
    ============

       Different SPICE kernel types are used to store different kinds of
       ancillary data.

       SPK (Spacecraft Planet Kernel) files contain ephemerides (position
       and velocity) for spacecraft, planets, satellites, comets and
       asteroids as well as for moving or fixed spacecraft and instrument
       structures. SPK files are located under the kernels/spk
       directory of this archive.

       PCK (Planetary Constants Kernel) files contain certain physical,
       dynamical and cartographic constants for target bodies, such as size
       and shape specifications, and orientation of the spin axis and prime
       meridian. PCK files are located under the kernels/pck
       directory of this archive.

       IK (Instrument Kernel) files contain instrument parameters relevant
       for computing an instrument's geometry such as field-of-view
       definitions, CCD and optical distortion characteristics, and internal
       timing parameters. IK files are located under the kernels/ik
       directory of this archive.

       CK (C-matrix Kernel) files contain time varying orientations for
       spacecraft, spacecraft structures, and articulating science
       instruments. CK files are located under the kernels/ck
       directory of this archive.

       DSK (Digital Shape Kernel) files contain detailed shape models for
       extended objects. These objects typically are solar system bodies such as
       planets, dwarf planets, natural satellites, asteroids, and comet nuclei. DSK
       data can represent the shapes of such objects, as well as local topography,
       such as that in the vicinity of a rover or a tracking station. DSK data also
       can represent shapes of artificial objects such as spacecraft components, or
       represent abstractions such as the subset of a target body's surface that
       has a property of interest. DSK files are located under the kernels/dsk
       directory of this archive.

       LSK (Leapseconds Kernel) files contain the leapseconds and the
       values of other constants required to perform a transformation
       between Universal Time Coordinated (UTC) and Ephemeris time (ET),
       which is also known as Barycentric Dynamical Time (TDB). LSK
       files are located under the kernels/lsk directory of
       this archive.

       SCLK (Spacecraft Clock Kernel) files contain on-board clock
       calibration data required to perform a transformation between
       Ephemeris time (ET) and spacecraft on-board time (SCLK). SCLK files
       are located under the kernels/sclk directory of this
       archive.

       FK (Frame definitions Kernel) files contain information required to
       define reference frames, sources of frame orientation data and
       connections between these frames and other frames supported within
       the SPICE system. The science instrument frame definitions provided
       in the FK files include mounting alignment information for the
       instruments. FK files are located under the kernels/fk
       directory of this archive.

       MK (Meta-Kernel) files list sets of related SPICE kernels that
       should be used together, providing an easy way to make data from
       these kernel sets available to a SPICE-based application by loading
       meta-kernels into the program using the high level SPICE data loader
       routine FURNSH. MK files are located the kernels/mk
       directory of this archive.

    Kernel Details
    ==============

       The subsections below provide details, such as file naming
       conventions and specific details, for each of the kernel types
       included in this archive.

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    SKD Latest Release Notes
    ========================

       This section provides the latest release notes of the GNSS
       SPICE Kernel Dataset

    Back to Table of Contents

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    SPICE Software and Documentation
    ================================

       The latest SPICE Toolkit for a variety of computer platforms,
       additional utility programs, documentation, tutorials, and hands-on
       lessons are available at the NAIF Node of the PDS:

          http://naif.jpl.nasa.gov

       specifically:

          Toolkit:   http://naif.jpl.nasa.gov/naif/toolkit.html

          Utilities: http://naif.jpl.nasa.gov/naif/utilities.html

          Tutorials: http://naif.jpl.nasa.gov/naif/tutorials.html

          Lessons:   http://naif.jpl.nasa.gov/naif/lessons.html

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    Contact Information
    ===============================

       If you have any questions regarding this file contact the
       ESA SPICE Service (ESS) at ESAC:

               Alfredo Escalante Lopez
               (+34) 91-8131-429
               spice@sciops.esa.int

    End of GNSS SPICE Kernel Dataset description.
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