schema.json

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "schema.json#",
  "title": "Sat Extension",
  "description": "STAC Sat Extension to a STAC Item.",
  "allOf": [
    {
      "$ref": "../../../item-spec/json-schema/item.json"
    },
    {
      "$ref": "#/definitions/sat"
    },
    {
      "$ref": "../../../item-spec/json-schema/instrument.json"
    }
  ],
  "definitions": {
    "sat": {
      "type": "object",
      "required": [
        "stac_extensions",
        "properties"
      ],
      "properties": {
        "stac_extensions": {
          "type": "array",
          "contains": {
            "const": "sat"
          }
        },
        "properties": {
          "type": "object",
          "anyOf": [
            {"required": ["sat:relative_orbit"]},
            {"required": ["sat:orbit_state"]}
          ],
          "properties": {
            "sat:relative_orbit": {
              "type": "integer",
              "minimum": 1
            },
            "sat:orbit_state": {
              "title": "Orbit State",
              "type": "string",
              "enum": [
                "ascending",
                "descending",
                "geostationary"
              ]
            }
          }
        }
      }
    }
  }
}