HAMMERHEAD-Space Astrodynamics Ecosystem

Package Dependency Graph

QLaw.jl ──> AstroPropagators.jl ──> AstroForceModels.jl ──> AstroCoords.jl
                                                          ├─> SatelliteToolbox ecosystem
SimsFlanagan.jl ──> Lambert.jl ──> AstroCoords.jl
AstroMeasurements.jl ──> AstroCoords.jl

Shared Conventions

Core Design Principles

1. AD-first: All code must be differentiable. Use promote_type, avoid mutation, use SVector returns.
2. Zero allocations: Hot-path functions (acceleration, EOM) must pass @check_allocs.
3. Type stability: All exported functions must pass JET analysis.
4. SciML composability: Follow Problem/Solution/Algorithm pattern.
5. Multiple dispatch: Use type dispatch over if/else branching.

Standard State Representation

• Position/velocity: [rx, ry, rz, vx, vy, vz] km, km/s in J2000 ECI
• Parameters: ComponentVector(; JD=epoch_jd, μ=gravitational_param)
• Time: elapsed seconds since epoch; Julian Date = p.JD + t / 86400.0

New Package Checklist

When creating a new package in this ecosystem:

• Add .JuliaFormatter.toml with style = "blue"
• Add typos.toml for spell checking
• Set up Aqua.jl, JET.jl, AllocCheck tests
• Use StaticArraysCore (not full StaticArrays) for minimal deps
• Support Julia 1.10+ in compat
• Follow AbstractX base type pattern
• Document with # Arguments, # Returns, # References sections
• Add AD differentiability tests against FiniteDiff