AstroMeasurements.jl

Julia library for computing astrodynamic measurements from various observer types. Repo: HAMMERHEAD-Space/AstroMeasurements.jl

Architecture

Observer Types

Source Layout

src/
  AstroMeasurements.jl          # Module entry, exports, includes
  constants.jl                   # Physical constants
  observer_types.jl              # Observer type definitions
  observer_functions.jl          # Shared observer utilities
  get_measurement.jl             # Core measurement computation
  get_measurement_jacobian.jl    # Analytical Jacobians
  radar.jl                       # Radar-specific logic
  optical.jl                     # Optical-specific logic
  gnss.jl                        # GNSS-specific logic
  fullstate.jl                   # Full-state observer logic

Key Patterns

Core API

# Compute measurement from observer
meas = get_measurement(observer, state, params...)

# Compute analytical Jacobian
H = get_measurement_jacobian(observer, state, params...)

Multiple dispatch on observer type selects the correct measurement model.

Analytical Jacobians

Hand-derived Jacobians verified against ForwardDiff in tests. This provides:

• Better performance than AD for orbit determination inner loops
• Validated correctness against automatic differentiation

Features

• Light-time correction: Optional for ground station observations
• Elevation masking: Configurable elevation masks for visibility checking
• Frame transformations: Uses SatelliteToolboxTransformations for ECI/ECEF conversion

Adding a New Observer Type

1. Define observer struct in observer_types.jl
2. Implement get_measurement() dispatch for the new type
3. Derive and implement analytical Jacobian in get_measurement_jacobian.jl
4. Validate Jacobian against ForwardDiff in tests
5. Add @check_allocs test for measurement computation

Dependencies

• AstroCoords 0.3, Parameters 0.12, StaticArraysCore 1
• SatelliteToolboxTransformations 1 (frame transformations)
• Test: AllocCheck, Aqua, ForwardDiff, JET