FOVSimulator.jl

FOVSimulator.jl is a Julia package for simulating camera field of view (FOV) in space missions. It specializes in camera simulations for observing celestial bodies such as asteroids, providing high-precision position and attitude calculations using SPICE kernels and image generation capabilities through ray tracing.

Features

• High-precision position and attitude calculations for spacecraft, cameras, and celestial bodies using SPICE kernels
• Ray tracing-based intersection detection for asteroid shape models
• Thermal image simulation in conjunction with thermophysical models
• Fast intersection detection algorithms using bounding boxes
• Support for multiple bodies (e.g., binary asteroid systems)

Installation

You can install the package using Julia's package manager:

using Pkg
Pkg.add(url="https://github.com/Astroshaper/FOVSimulator.jl")

Or in the package manager mode in Julia REPL (press ] to enter):

] add https://github.com/Astroshaper/FOVSimulator.jl

Dependencies

• LinearAlgebra.jl
• Rotations.jl
• StaticArrays.jl
• SPICE.jl
• AsteroidShapeModels.jl

Basic Usage

1. Import Required Modules

using FOVSimulator
using SPICE

2. Load SPICE Kernels

# Load SPICE kernels
SPICE.furnsh("path/to/kernel/file.tm")

3. Set Up Camera

# Specify camera NAIF ID, FOV angles, and image size
camera_id = -12345  # Camera NAIF ID
fov_angles = (10.0, 8.0)  # FOV angles (width, height) [degrees]
img_size = (1024, 768)  # Image size (width, height) [pixels]

# Create camera object
camera = SpiceCamera("CAMERA_NAME", camera_id, fov_angles, img_size)

4. Set Up Spacecraft

# Create spacecraft object
spacecraft = SpiceSpacecraft("SPACECRAFT_NAME")

# Mount camera on spacecraft
add_instrument!(spacecraft, camera)

5. Set Up Asteroid

# Load shape model
# Load an asteroid shape model
# - `path/to/shape.obj` is the path to your OBJ file (mandatory)
# - `scale` : scale factor for the shape model (e.g., 1000 for km to m conversion)
# - `with_face_visibility` : whether to build face-to-face visibility graph for illumination checking and thermophysical modeling
# - `with_bvh` : whether to build BVH for ray tracing
shape = load_shape_obj("path/to/shape.obj"; scale=1000, with_face_visibility=false, with_bvh=true)

# Create asteroid object
asteroid = SpiceAsteroid("ASTEROID_NAME", shape, "ASTEROID_FIXED_FRAME")

6. Update States

# Set simulation time
et     = SPICE.str2et("2025-01-01T12:00:00")  # Ephemeris time
ref    = "J2000"                              # Reference frame
abcorr = "NONE"                               # Aberration correction flag
obs    = "EARTH"                              # Observer

# Update spacecraft and asteroid states
update!(spacecraft, et, ref, abcorr, obs)
update!(asteroid, et, ref, abcorr, obs)

7. Generate Intersection Map

# Perform intersection detection for each pixel
intersection_map = generate_intersection_map(spacecraft.state.instruments["CAMERA_NAME"], asteroid)

8. Generate Image

# Generate thermal image using temperature data
temperatures = fill(300.0, length(asteroid.static.shape.faces))  # Example: set all faces to 300K
image = generate_image_temperature(intersection_map, temperatures)

# Generate radiance image using emissivity and temperature data
emissivities = fill(0.9, length(asteroid.static.shape.faces))  # Example: set all faces to 0.9 emissivity
radiance_image = generate_image_radiance(intersection_map, emissivities, temperatures)

Advanced Usage

Binary Asteroid Simulation

# Set up primary and secondary asteroids
primary = SpiceAsteroid("PRIMARY", shape_primary, "PRIMARY_FIXED_FRAME")
secondary = SpiceAsteroid("SECONDARY", shape_secondary, "SECONDARY_FIXED_FRAME")

# Update states
update!(spacecraft, et, ref, abcorr, obs)
update!(primary, et, ref, abcorr, obs)
update!(secondary, et, ref, abcorr, obs)

# Generate intersection maps
intersection_map1 = generate_intersection_map(spacecraft.state.instruments["CAMERA_NAME"], primary)
intersection_map2 = generate_intersection_map(spacecraft.state.instruments["CAMERA_NAME"], secondary)

# Generate thermal image (considering both asteroids)
image = generate_image_temperature(
    intersection_map1, temperatures_primary,
    intersection_map2, temperatures_secondary
)

Integration with Thermophysical Models

You can integrate with thermophysical modeling packages to calculate asteroid surface temperatures and use them for thermal image simulation. See the test file test/TIRI_image_Didymos.jl for a detailed example.

Key Components

SpiceCamera

Represents a camera model based on SPICE kernels. Manages static camera information (name, ID, FOV shape, etc.) and dynamic state (position, velocity, etc.).

SpiceSpacecraft

Represents a spacecraft model based on SPICE kernels. Manages static spacecraft information and dynamic state, and can carry multiple instruments (cameras, etc.).

SpiceAsteroid

Represents an asteroid model based on SPICE kernels. Manages static asteroid information (name, shape model, fixed frame, etc.) and dynamic state (position, velocity, etc.).

Ray Tracing Components

The ray tracing functionality (Ray, BoundingBox, intersection detection functions) is now provided by the AsteroidShapeModels.jl package. This includes:

• Ray: Represents a ray for ray tracing
• BoundingBox: Represents a bounding box for shape models
• intersect_ray_triangle: Detects intersection between a ray and a triangle
• intersect_ray_shape: Detects intersection between a ray and a shape model
• intersect_ray_bounding_box: Detects intersection between a ray and a bounding box

Image Generation Functions

• generate_pixel_rays: Generates rays corresponding to each pixel of a camera
• generate_intersection_map: Generates intersection results for each pixel and an asteroid surface
• generate_image_temperature: Generates a thermal image from intersection results and surface temperatures
• generate_image_radiance: Generates a radiance image from intersection results, emissivities, and surface temperatures

License

This package is released under the MIT License. See the LICENSE file for details.