Add sat cycle

CHANGELOG.md

@@ -8,6 +8,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Added cycle field ([#6](https://github.com/stac-extensions/sat/issues/6))
+
 ### Changed
 
 ### Deprecated

README.md

@@ -21,13 +21,14 @@ It will often be combined with other extensions that describe the actual data, s
 
 ## Item Properties
 
-| Field Name                            | Type    | Description |
-| ------------------------------------- | ------- | ----------- |
-| sat:platform_international_designator | string  | The International Designator, also known as COSPAR ID, and NSSDCA ID |
-| sat:orbit_state                       | string  | The state of the orbit. Either `ascending` or `descending` for polar orbiting satellites, or `geostationary` for geosynchronous satellites |
-| sat:absolute_orbit                    | integer | The absolute orbit number at the time of acquisition.        |
-| sat:relative_orbit                    | integer | The relative orbit number at the time of acquisition.        |
+| Field Name                            | Type    | Description                                                                                                                                                                                          |
+| ------------------------------------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| sat:platform_international_designator | string  | The International Designator, also known as COSPAR ID, and NSSDCA ID                                                                                                                                 |
+| sat:orbit_state                       | string  | The state of the orbit. Either `ascending` or `descending` for polar orbiting satellites, or `geostationary` for geosynchronous satellites                                                           |
+| sat:absolute_orbit                    | integer | The absolute orbit number at the time of acquisition.                                                                                                                                                |
+| sat:relative_orbit                    | integer | The relative orbit number at the time of acquisition.                                                                                                                                                |
 | sat:anx_datetime                      | string  | The [Ascending Node](https://en.wikipedia.org/wiki/Orbital_node) Crossing (ANX) time, in UTC. It is formatted according to [RFC 3339, section 5.6](https://tools.ietf.org/html/rfc3339#section-5.6). |
+| sat:cycle                             | integer | The number of repeat cycle done by the satellite at the time of the acquisition. [Repeat cycle](https://ltb.itc.utwente.nl/page/498/concept/81577) is the time between two successive identical orbits.                                                                                                                                                                   |
 
 *At least one of the fields must be specified.*
 
@@ -66,6 +67,12 @@ reference. Used to quickly compute orbital parameters without having to download
 fly a baseline between 2 satellite acquisition, to find the best candidate in the archive from a post-disaster event (e.g 
 earthquake) scene acquisition for a DInSAR processing.
 
+#### sat:cycle
+
+The repeat cycle of the satellite. The repeat cycle is the number of orbits required for the satellite to return to the same
+position in its orbit. It is used to determine the relative orbit number. For instance, a satellite with a 16-day repeat cycle
+will have 16 relative orbits.
+
 ## Contributing
 
 All contributions are subject to the

examples/example-sentinel1.json

@@ -54,6 +54,7 @@
     "sat:absolute_orbit": 4892,
     "sat:relative_orbit": 95,
     "sat:anx_datetime": "2015-03-05T04:41:46.5788740Z",
+    "sat:cycle": 407,
     "sar:instrument_mode": "IW",
     "sar:polarizations": [
       "VV",

json-schema/schema.json

@@ -46,6 +46,11 @@
                       "required": [
                         "sat:anx_datetime"
                       ]
+                    },
+                    {
+                      "required": [
+                        "sat:cycle"
+                      ]
                     }
                   ]
                 },
@@ -140,6 +145,10 @@
         "sat:anx_datetime": {
           "type": "string",
           "format": "date-time"
+        },
+        "sat:cycle": {
+          "type": "integer",
+          "minimum": 1
         }
       },
       "patternProperties": {