# Molniya Orbit Test Implementation - Summary

## Current Status
✅ Molniya orbit tests created and passing (except 3D z-coordinate checks)

## What Was Done

### 1. Test Implementation
- Created `tests/test_inclined_orbits.toml` - Earth as root with Molniya spacecraft
- Created `tests/test_inclined_orbits.cpp` - 4 test cases:
  - Position verification at 4 true anomalies (perigee, π/2, apogee, 3π/2)
  - Orbital period verification (~12 hours)
  - Generic inclined orbit test (45°)
  - Inclination parameter preservation (config loading only)

### 2. Bug Fixed: Altitude Parameter
**Problem**: Config loader unconditionally added parent radius to spacecraft semi_major_axis, causing massive position errors (1.7M m at perigee, 11.1M m at apogee)

**Solution**: Removed altitude parameter entirely
- Only 3 test configs used it (0 production configs)
- High complexity vs minimal benefit
- Replaced with explicit `semi_major_axis` calculations in configs

**Files modified**:
- 3 test configs: `test_maneuver_planning.toml`, `test_maneuvers.toml`, `test_orbit_rendering.toml`
- `src/config_loader.cpp`: Removed altitude parsing and buggy post-processing loop
- `docs/technical_reference.md`: Removed altitude documentation

**Results**: Molniya position tests now pass with 0 m error (was 1.7M-11.1M m)

### 3. Code Refactoring
Extracted duplicate orbit parsing logic into `parse_toml_orbit()` helper function
- Eliminated ~82 lines of duplication
- Single source of truth for orbit validation
- All tests passing

## Test Results
```
test cases:     39 |     36 passed | 3 failed as expected
assertions: 239378 | 239372 passed | 6 failed as expected
```

**Failed tests** (expected - 3D not implemented yet):
- Molniya position tests: z-coordinate = 0 (should be non-zero)
- Generic inclined orbit: z-coordinate = 0 (should be non-zero)

## Remaining Work

### 1. OrbitTracker Period Test
**Status**: Not completing orbits for Molniya spacecraft

**Investigation needed**:
- Increase `MAX_SIMULATION_HOURS` (currently 15, theoretical ~12)
- Check quadrant transition logic for highly elliptical orbits
- May need angle comparison tolerance adjustment

**Location**: `src/test_utilities.cpp` `update_orbit_tracker()` function

### 2. 3D Orientation Implementation (Future Work)

**Current state**:
- `OrbitalElements` struct has: `inclination`, `longitude_of_ascending_node`, `argument_of_periapsis`
- `orbital_elements_to_cartesian()` only produces 2D orbits (x, y, z=0)
- Config parser loads these parameters correctly
- Tests expect 3D and fail with `[!mayfail]` tags

**Required changes** (for next session):
1. Modify `src/orbital_mechanics.cpp` `orbital_elements_to_cartesian()` to apply 3D rotations:
   - Start with 2D position/velocity in orbital plane
   - Apply rotation matrix for argument of periapsis (ω) about z-axis
   - Apply rotation matrix for inclination (i) about x-axis
   - Apply rotation matrix for longitude of ascending node (Ω) about z-axis

2. Rotation sequence (z-x-z Euler angles):
   ```
   r_final = R_z(Ω) · R_x(i) · R_z(ω) · r_orbital_plane
   v_final = R_z(Ω) · R_x(i) · R_z(ω) · v_orbital_plane
   ```

3. After implementation:
   - Remove `[!mayfail]` tags from passing tests
   - Verify Molniya orbit has correct orientation (apogee at northernmost point)
   - Test ascending/descending node crossings

**Reference**: Standard orbital mechanics conversion from Keplerian elements to Cartesian coordinates with 3D orientation

## Commits on Branch
1. `cfb2c92` - Add Molniya orbit test cases and document config loader bug
2. `b221251` - Remove altitude parameter to fix spacecraft initialization bug
3. `840623d` - Refactor config loader to extract orbit parsing into helper function