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Add orbit state vectors (#8)
* Add orbit state vectors * updated changelog * json schema * Remove .vscode/settings.json * feat: Add validation for orbit state vectors with date-time strings * updated versions for validation * Update README.md Co-authored-by: Matthias Mohr <m.mohr@uni-muenster.de> * feat: Update date-time string pattern in JSON schema for improved validation * Update README.md Co-authored-by: Matthias Mohr <m.mohr@uni-muenster.de> * docs: Improve clarity in README regarding state vector file references --------- Co-authored-by: Matthias Mohr <m.mohr@uni-muenster.de>
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‎.github/remark.yaml‎

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plugins:
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# GitHub Flavored Markdown
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- remark-gfm
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# Check links
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- validate-links
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# Apply some recommended defaults for consistency
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# General formatting
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- - remark-lint-emphasis-marker
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- '*'
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- remark-lint-no-undefined-references
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- remark-lint-hard-break-spaces
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- remark-lint-blockquote-indentation
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- remark-lint-no-consecutive-blank-lines
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- - remark-lint-unordered-list-marker-style
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- '-'
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- - remark-lint-list-item-indent
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- space
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- space
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# Tables
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- remark-lint-table-pipes
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- remark-lint-no-literal-urls

‎CHANGELOG.md‎

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### Added
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- Added `orbit_cycle` field ([#6](https://github.com/stac-extensions/sat/issues/6))
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- Added sat:orbit_state_vectors field ([#8](https://github.com/stac-extensions/sat/issues/8))
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### Changed
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‎README.md‎

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## Item Properties
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| Field Name | Type | Description |
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| ------------------------------------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| sat:platform_international_designator | string | The International Designator, also known as COSPAR ID, and NSSDCA ID |
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| sat:orbit_state | string | The state of the orbit. Either `ascending` or `descending` for polar orbiting satellites, or `geostationary` for geosynchronous satellites |
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| sat:orbit_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. |
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| sat:absolute_orbit | integer | The absolute orbit number at the time of acquisition. |
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| sat:relative_orbit | integer | The relative orbit number at the time of acquisition. |
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| 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). |
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| Field Name | Type | Description |
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| ------------------------------------- | --------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| sat:platform_international_designator | string | The International Designator, also known as COSPAR ID, and NSSDCA ID |
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| sat:orbit_state | string | The state of the orbit. Either `ascending` or `descending` for polar orbiting satellites, or `geostationary` for geosynchronous satellites |
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| sat:absolute_orbit | integer | The absolute orbit number at the time of acquisition. |
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| sat:relative_orbit | integer | The relative orbit number at the time of acquisition. |
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| sat:orbit_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. |
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| sat:orbit_state_vectors | Map<string, \[number]> | The state vectors of the satellite at the time of acquisition. |
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| 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). |
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*At least one of the fields must be specified.*
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position in its orbit. It is used to determine the relative orbit number. For instance, a satellite with a 16-day repeat cycle
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will have 16 relative orbits.
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#### sat:orbit_state_vectors
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The state vectors of the satellite at the time of acquisition. The state vectors are a set of parameters that describe the
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position and velocity of the satellite at a given time. The state vectors are used to compute the position of the satellite
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at any time during the acquisition.
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The state vectors are usually provided in the [ECI](https://en.wikipedia.org/wiki/Earth-centered_inertial) frame.
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The field is a map where the key is the time of the state vector and the value is an array of 6 elements (optional 9).
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The first 3 elements are the position of the satellite in meters and the last 3 elements are the velocity of the satellite in meters per second.
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The optional 3 additional elements are the acceleration of the satellite in meters per second squared.
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Example:
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```json
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{
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"sat:orbit_state_vectors": {
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"2015-03-05T05:19:40.103Z": [
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5082939.4189831074,
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1595651.7369050409,
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4648033.5588545678,
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5173.8779329387489,
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-269.5432365485845,
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-5550.246440359806
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],
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"2015-03-05T05:19:45.449Z": [
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5110519.0376543682,
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1594174.328112772,
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4618284.7202579351,
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5143.1200754073143,
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-283.12343661734587,
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-5578.2160610647188
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],
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"2015-03-05T05:19:50.449Z": [
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5136162.3887853986,
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1592727.024757518,
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4590328.5904560406,
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5114.1961953273549,
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-295.79384304587683,
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-5604.2108611458289
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]
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}
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}
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```
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It is recommended that the state vectors are provided in a separate file and referenced as a link with relationship type `sat:osv`.
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The file should correspond to the example above.
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## Relation types
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The following types should be used as applicable `rel` types in the
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[Link Object](https://github.com/radiantearth/stac-spec/tree/master/item-spec/item-spec.md#link-object).
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| Type | Description |
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| ------- | -------------------------------------------------- |
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| sat:osv | Link to a file containing the orbit state vectors. |
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## Contributing
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All contributions are subject to the

‎examples/example-sentinel1.json‎

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"sat:relative_orbit": 95,
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"sat:anx_datetime": "2015-03-05T04:41:46.5788740Z",
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"sat:orbit_cycle": 407,
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"sat:orbit_state_vectors": {
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"2015-03-05T05:19:40.103Z": [
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5082939.418983107,
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1595651.736905041,
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4648033.558854568,
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5173.877932938749,
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-269.5432365485845,
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-5550.246440359806
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],
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"2015-03-05T05:19:45.449Z": [
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5110519.037654368,
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1594174.328112772,
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4618284.720257935,
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5143.120075407314,
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-283.1234366173459,
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-5578.216061064719
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],
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"2015-03-05T05:19:50.449Z": [
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5136162.388785399,
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1592727.024757518,
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4590328.590456041,
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5114.196195327355,
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-295.7938430458768,
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-5604.210861145829
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]
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},
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"sar:instrument_mode": "IW",
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"sar:polarizations": [
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"VV",

‎json-schema/schema.json‎

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"required": [
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"sat:orbit_cycle"
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]
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},
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{
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"required": [
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"sat:orbit_state_vectors"
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]
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}
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]
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},
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"sat:orbit_cycle": {
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"type": "integer",
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"minimum": 1
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},
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"sat:orbit_state_vectors": {
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"type": "object",
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"$comment": "The key is a date-time string, and the value is an array of numbers.",
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"patternProperties": {
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"^(\\d{4}-[01]\\d-[0-3]\\dT[0-2]\\d:[0-5]\\d:[0-5]\\d\\.\\d+([+-][0-2]\\d:[0-5]\\d|Z))|(\\d{4}-[01]\\d-[0-3]\\dT[0-2]\\d:[0-5]\\d:[0-5]\\d([+-][0-2]\\d:[0-5]\\d|Z))|(\\d{4}-[01]\\d-[0-3]\\dT[0-2]\\d:[0-5]\\d([+-][0-2]\\d:[0-5]\\d|Z))$": {
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"type": "array",
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"items": {
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"type": "number"
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},
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"minItems": 6,
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"maxItems": 9
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}
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},
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"additionalProperties": false
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}
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},
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"patternProperties": {

‎package.json‎

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{
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"name": "stac-extensions",
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"name": "stac-extension-sat",
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"version": "1.0.0",
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"scripts": {
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"test": "npm run check-markdown && npm run check-examples",
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"format-examples": "stac-node-validator . --format --schemaMap https://stac-extensions.github.io/sat/v1.0.0/schema.json=./json-schema/schema.json"
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},
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"dependencies": {
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"remark-cli": "^8.0.0",
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"remark-lint": "^7.0.0",
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"remark-lint-no-html": "^2.0.0",
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"remark-preset-lint-consistent": "^3.0.0",
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"remark-preset-lint-markdown-style-guide": "^3.0.0",
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"remark-preset-lint-recommended": "^4.0.0",
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"remark-validate-links": "^10.0.0",
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"stac-node-validator": "^1.0.0"
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"remark-cli": "^12.0.0",
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"remark-gfm": "^4.0.0",
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"remark-lint": "^9.1.2",
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"remark-lint-no-html": "^3.1.2",
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"remark-preset-lint-consistent": "^5.1.2",
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"remark-preset-lint-markdown-style-guide": "^5.1.3",
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"remark-preset-lint-recommended": "^6.1.3",
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"remark-validate-links": "^13.0.0",
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"stac-node-validator": "^1.3.0"
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}
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}

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