> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rotastellar.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Ground Passes

> Compute ground station AOS/LOS windows with elevation data

<Note>
  **Base URL:** `https://sim.rotastellar.com`
  — No API key required.
</Note>

## Request

<ParamField body="elements" type="object" required>
  Orbital elements. See [Orbital Elements](/sim/overview#orbital-elements).
</ParamField>

<ParamField body="start" type="string">
  ISO 8601 start time. Defaults to current time.
</ParamField>

<ParamField body="duration_hours" type="number">
  Prediction window in hours. Default: 24. Max: 72.
</ParamField>

<ParamField body="min_elevation_deg" type="number">
  Minimum satellite elevation above horizon (degrees). Default: 5.
</ParamField>

<ParamField body="ground_stations" type="array">
  Custom ground station list. Defaults to the 12-station global network (KSAT, NASA, AWS). Each station needs `id`, `name`, `lat`, `lon`.
</ParamField>

<RequestExample>
  ```bash theme={null}
  curl -X POST https://sim.rotastellar.com/v1/passes \
    -H "Content-Type: application/json" \
    -d '{
      "elements": {
        "altitude_km": 550,
        "inclination_deg": 53
      },
      "duration_hours": 24,
      "min_elevation_deg": 10
    }'
  ```
</RequestExample>

<ResponseExample>
  ```json 200 OK theme={null}
  {
    "passes": [
      {
        "station_id": "gs_svalbard",
        "station_name": "Svalbard",
        "provider": "KSAT",
        "aos": "2026-03-08T12:34:56Z",
        "los": "2026-03-08T12:45:23Z",
        "duration_s": 627,
        "max_elevation_deg": 45.6,
        "points": [
          {
            "timestamp": "2026-03-08T12:34:56Z",
            "elevation_deg": 10.0,
            "azimuth_deg": 90.5,
            "range_km": 2500.1
          }
        ]
      }
    ],
    "count": 8,
    "start": "2026-03-08T12:00:00Z",
    "duration_hours": 24,
    "stations_checked": 12
  }
  ```
</ResponseExample>

## Default Ground Stations

The service includes a 12-station global network:

| Station   | Location        | Provider |
| --------- | --------------- | -------- |
| Svalbard  | 78.2°N, 15.4°E  | KSAT     |
| Troll     | 72.0°S, 2.5°E   | KSAT     |
| Awarua    | 46.5°S, 168.4°E | KSAT     |
| Fairbanks | 64.9°N, 147.9°W | NASA     |
| Wallops   | 37.9°N, 75.5°W  | NASA     |
| McMurdo   | 77.9°S, 166.7°E | NASA     |
| Singapore | 1.4°N, 103.8°E  | AWS      |
| Bahrain   | 26.1°N, 50.5°E  | AWS      |
| Oregon    | 43.8°N, 120.6°W | AWS      |
| Cape Town | 33.9°S, 18.4°E  | AWS      |
| Stockholm | 59.3°N, 18.1°E  | AWS      |
| Sydney    | 33.9°S, 151.2°E | AWS      |