## ADDED Requirements

### Requirement: PlanetConfig shape

The system SHALL export a `PlanetConfig` type containing name, mass, radius, polar radius, surface gravity, rotation period, axial tilt, optional atmosphere, satellites, optional orbital elements, and optional texture manifest.

#### Scenario: Validate PlanetConfig schema

- **WHEN** a `PlanetConfig` with all required fields is constructed via Zod parse
- **THEN** validation succeeds
- **AND** when mass is omitted, validation throws `ValidationError`

### Requirement: AtmosphereConfig shape

The system SHALL export an `AtmosphereConfig` type with surface pressure, scale height, Rayleigh coefficient, Mie coefficient, and extinction per air mass.

#### Scenario: Validate atmosphere

- **WHEN** an `AtmosphereConfig` with valid positive values is parsed
- **THEN** validation succeeds
- **AND** `atmosphericDensity(0)` on a `PlanetSurface` using this config returns surface pressure-derived density

### Requirement: SatelliteConfig shape

The system SHALL export a `SatelliteConfig` type with name, mass, radius, orbital radius, orbital period, inclination, eccentricity, and albedo.

#### Scenario: Satellite definition

- **WHEN** a `SatelliteConfig` for a moon is parsed with `mass > 0` and `orbitalRadius > 0`
- **THEN** validation succeeds

### Requirement: PlanetSurface geometry delegation

The system SHALL implement `PlanetSurface` whose `distance`, `bearing`, `destination`, and `pointInPolygon` methods delegate to `@suaveplan/geo` functions using the planet's ellipsoid.

#### Scenario: PlanetSurface uses correct ellipsoid

- **WHEN** a `PlanetSurface` is constructed with a planet having `radius = 3396200` and `polarRadius = 3376200` (Mars-like)
- **THEN** `distance` between two surface points matches the great-circle distance on that ellipsoid, not WGS84

### Requirement: Atmospheric density

The system SHALL compute atmospheric density at a given altitude from `AtmosphereConfig` using the scale-height exponential model.

#### Scenario: Density halves at scale height

- **WHEN** `atmosphericDensity(scaleHeight)` is called on a planet with `scaleHeight = 8500`
- **THEN** the result equals half the surface density

### Requirement: Air mass

The system SHALL compute air mass for a given altitude angle using the Kasten–Young formula.

#### Scenario: Zenith air mass

- **WHEN** `airMass(90)` is called
- **THEN** the result is approximately `1.0`
- **AND** `airMass(0)` returns a value significantly greater than `1.0`

### Requirement: No bundled planet data

The system SHALL NOT bundle any pre-defined planet configuration.

#### Scenario: Inspect geo-planet exports

- **WHEN** all exports from `@suaveplan/geo-planet` are enumerated
- **THEN** no `EARTH`, `MARS`, or pre-built `PlanetConfig` constant exists