AstroUniverse

CelestialBody(name::AbstractString, mu::Real, equatorialradius::Real, flattening::Real, naifid::Integer, texturefile::AbstractString)

Positional outer constructor that promotes numeric fields to a common type.

CelestialBody(name::AbstractString, mu::Real, equatorial_radius::Real, flattening::Real, naifid::Integer)

Represents a celestial body with physical parameters.

Fields (units):

• name::String
• mu::T — gravitational parameter
• equatorial_radius::T — equatorial radius
• flattening::T — geometric flattening
• naifid::Int — NAIF body ID
• texture_file::String — path to texture image file for visualization (optional)

Notes:

• Numeric fields (mu, equatorial_radius, flattening) are promoted to a common element type T to ensure type stability (e.g., passing a BigFloat will promote the others to BigFloat).
• Units default to km and seconds for built-in celestial bodies. If changing units, be consistent throughout the simulation.

Examples

using AstroUniverse
moon_like = CelestialBody(name="MyMoon", 
                                 mu=4902.8, 
                                 equatorial_radius=1737.4, 
                                 flattening=0.0,
                                 naifid=301,
                                 texture_file="path/to/moon_texture.jpg");
show(moon_like)

# output
CelestialBody:
  name               = MyMoon
  μ                  = 4902.8
  Equatorial Radius  = 1737.4
  Flattening         = 0.0
  NAIF ID            = 301
  Texture File       = path/to/moon_texture.jpg

CelestialBody(; name="unnamed", mu=earth.mu,
                equatorial_radius=earth.equatorial_radius,
                flattening=earth.flattening, naifid=earth.naifid,
                texture_file="")

Keyword outer constructor that defaults all fields to Earth's values. Numeric fields are promoted to a common element type.

function __init__()

Load SPICE kernels from managed scratch space on module initialization.

download_spice_kernel(filename::AbstractString, url::AbstractString)

Download a SPICE kernel from the given URL to the cache directory.

The kernel is cached in the AstroUniverse managed scratch directory, so it will only be downloaded once and persist across Julia sessions. This function does NOT load the kernel into SPICE - use load_spice_kernel after downloading.

Arguments

• filename: Name of the kernel file (e.g., "de441.bsp")
• url: Full URL to download the kernel from

Examples

using AstroUniverse

# Download Mars satellite ephemeris (Phobos, Deimos)
download_spice_kernel("mar099.bsp",
    "https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/satellites/mar099.bsp")

# Then load it
load_spice_kernel("mar099.bsp")

All kernels available at: https://naif.jpl.nasa.gov/pub/naif/generic_kernels/

See also: load_spice_kernel, get_spice_directory

ensure_kernel_download(cache_dir, filename, url)

Download SPICE kernel if it doesn't exist. Does not furnish/load the kernel.

get_gravparam(body)

Return the body’s gravitational parameter μ.

get_spice_directory()

Return the path to the AstroUniverse SPICE kernel cache directory.

This directory persists across Julia sessions and is managed by Scratch.jl. You can manually place kernel files here to avoid downloading them.

Examples

using AstroUniverse

dir = get_spice_directory()
println("SPICE kernels cached at: ", dir)

# Manually copy a kernel file to the cache
# cp("my_kernel.bsp", joinpath(dir, "my_kernel.bsp"))
# Then load it
# load_spice_kernel("my_kernel.bsp")

See also: download_spice_kernel, list_downloaded_spice_kernels

list_cached_spice_kernels()

List all SPICE kernels currently loaded in memory.

Displays the filenames of kernels that have been furnished to SPICE and are actively being used. This shows what's actually in the SPICE kernel pool, not what's downloaded to disk.

Examples

using AstroUniverse

list_cached_spice_kernels()

# output
Cached SPICE Kernels (2 loaded):
  naif0012.tls
  de440.bsp

See also: load_spice_kernel, unload_spice_kernel, list_downloaded_spice_kernels

list_downloaded_spice_kernels()

List all SPICE kernel files (.bsp and .tls) downloaded to the persistent storage directory.

Displays kernel filenames with their file sizes in a formatted table. These are files available for loading, not necessarily currently loaded in SPICE memory. Use list_cached_spice_kernels to see which kernels are currently loaded.

Examples

using AstroUniverse

list_downloaded_spice_kernels()

# output
Downloaded SPICE Kernels:
  naif0012.tls              (5.3 KB)
  de440.bsp                 (114.0 MB)
  mar099.bsp                (2.1 MB)

Storage location: /path/to/scratch/spice_kernels

See also: download_spice_kernel, list_cached_spice_kernels, get_spice_directory

load_spice_kernel(filename::AbstractString)

Load a SPICE kernel from the cache directory into the SPICE system.

The kernel file must already exist in the cache (use download_spice_kernel first if needed). This calls SPICE.furnsh() to register the kernel.

Arguments

• filename: Name of the kernel file in the cache (e.g., "de441.bsp")

Examples

using AstroUniverse

# Download then load
download_spice_kernel("de440.bsp",
    "https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/planets/de440.bsp")
load_spice_kernel("de440.bsp")

# Or just load if already downloaded
load_spice_kernel("naif0012.tls")  # Default kernel

See also: download_spice_kernel, unload_spice_kernel, unload_all_spice_kernels

set_gravparam!(body, μ)

Set the body’s gravitational parameter μ.

function translate(from::CelestialBody, to::CelestialBody, jd_tdb::Real)

Compute the ICRF position vector from one body to another at a given TDB Julian date.

Arguments

• from: Observing/origin body.
• to: Target body.
• jd_tdb: Julian date in the TDB time scale.

Notes:

• Requires SPICE kernels to be loaded with SPICE.furnsh before calling.
• Uses the J2000/ICRF frame; distances are kilometers.

Returns

• 3-element position vector [x, y, z] in kilometers, from from to to, in ICRF (J2000).

Examples

# vector from Earth to Moon
using AstroUniverse
r_em = translate(earth, moon, 2458018.0)
println(r_em)

# output (may differ slightly due to SPICE kernel versions):
3-element Vector{Real}:
 -375694.5992365016
  -96115.68241892057
  -12226.882894748915

unload_all_spice_kernels()

Unload all SPICE kernels from memory.

This calls SPICE.kclear() to remove all loaded kernels. Useful for creating custom kernel configurations. The files remain in the storage directory.

Examples

using AstroUniverse

# Create custom configuration
unload_all_spice_kernels()
list_cached_spice_kernels()  # Shows none loaded

See also: load_spice_kernel, unload_spice_kernel

unload_spice_kernel(filename::AbstractString)

Unload a specific SPICE kernel from the SPICE system.

This calls SPICE.unload() to remove the kernel from memory. The file remains in the cache.

Arguments

• filename: Name of the kernel file to unload (e.g., "de440.bsp")

Examples

using AstroUniverse

# Swap planetary ephemeris versions
unload_spice_kernel("de440.bsp")
load_spice_kernel("de440.bsp")

See also: load_spice_kernel, unload_all_spice_kernels

Base.show(io::IO, body::CelestialBody)

Delegate show to MIME"text/plain" output.

function show(io::IO, ::MIME"text/plain", body::CelestialBody)

Show method for text/plain output.

const EARTH_DEFAULTS

Default physical parameters for Earth CelestialBody.

Earth (NAIF ID 399) CelestialBody model.

Jupiter (NAIF ID 599) CelestialBody model.

Mars (NAIF ID 499) CelestialBody model.

Mercury (NAIF ID 199) CelestialBody model.

Moon (NAIF ID 301) CelestialBody model.

Neptune (NAIF ID 899) CelestialBody model.

Pluto (NAIF ID 999) CelestialBody model.

Saturn (NAIF ID 699) CelestialBody model.

Sun (NAIF ID 10) CelestialBody model.

Uranus (NAIF ID 799) CelestialBody model.

Venus (NAIF ID 299) CelestialBody model.