### Orekit Package Overview

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/utils/class-use/ParameterDriversProvider

Lists the main packages in the Orekit library and provides a brief description for each.

```APIDOC
## Orekit Package Overview

### Description
This section provides a high-level overview of the core packages within the Orekit library, outlining their primary functionalities.

### Packages

*   **org.orekit.attitudes**: Provides classes to represent simple attitudes.
*   **org.orekit.estimation.measurements**: Defines classes related to orbit determination measurements.
*   **org.orekit.estimation.measurements.gnss**: Handles GNSS (Global Navigation Satellite System) measurements.
*   **org.orekit.estimation.measurements.modifiers**: Provides measurement modifiers.
*   **org.orekit.forces**: Provides the interface for force models used by `NumericalPropagator`, including classical spacecraft models.
*   **org.orekit.forces.drag**: Contains all drag-related forces.
*   **org.orekit.forces.empirical**: Implements empirical forces.
*   **org.orekit.forces.gravity**: Contains all gravity-related forces.
*   **org.orekit.forces.inertia**: Provides inertial force models.
*   **org.orekit.forces.maneuvers**: Models simple maneuvers.
*   **org.orekit.forces.maneuvers.propulsion**: Provides propulsion models for `Maneuver` classes.
*   **org.orekit.forces.maneuvers.trigger**: Provides maneuver trigger models for `Maneuver` classes.
*   **org.orekit.forces.radiation**: Contains all radiation pressure related forces.
*   **org.orekit.gnss.attitude**: Provides classes related to navigation satellites attitude modeling.
*   **org.orekit.models.earth.ionosphere**: Simulates the impact of the ionosphere.
*   **org.orekit.models.earth.ionosphere.nequick**: Implements NeQuick ionosphere models.
*   **org.orekit.models.earth.troposphere**: Simulates the impact of the troposphere.
*   **org.orekit.models.earth.troposphere.iturp834**: Contains the troposphere model OTU-4 P.834.
*   **org.orekit.propagation.analytical**: Top-level package for analytical propagators.
*   **org.orekit.propagation.analytical.gnss**: Propagates GNSS orbits.
*   **org.orekit.propagation.analytical.gnss.data**: Contains classes for GNSS almanacs and navigation messages.
*   **org.orekit.propagation.analytical.intelsat**: Propagates Intelsat's 11 elements.
*   **org.orekit.propagation.analytical.tle**: Reads and extrapolates TLEs (Two-Line Elements).
*   **org.orekit.propagation.integration**: Utilities for integration-based propagators.
*   **org.orekit.propagation.numerical.cr3bp**: Top-level package for CR3BP Models used with a numerical propagator.
*   **org.orekit.propagation.semianalytical.dsst.forces**: Provides force models for Draper Semi-analytical Satellite Theory (DSST).
```

--------------------------------

### Time Interval Start

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/class-use/AbsoluteDate

Get the start date of a time interval.

```APIDOC
## Get Time Interval Start Date

### Description
Retrieves the starting date of a time interval.

### Method
GET

### Endpoint
`/timeInterval/startDate`

### Parameters
None

### Response
#### Success Response (200)
- **startDate** (AbsoluteDate) - The starting date of the time interval.

#### Response Example
```json
{
  "startDate": "2023-01-01T00:00:00.000Z"
}
```
```

--------------------------------

### Get Start Year from IIRVEphemerisFile (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/iirv/IIRVEphemerisFile

Gets the start year associated with the ephemeris data in this file. This information is crucial for time-related calculations.

```java
public int getStartYear()
```

--------------------------------

### AnalyticalSolarPositionProvider Constructors

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/bodies/AnalyticalSolarPositionProvider

Constructors for initializing the AnalyticalSolarPositionProvider.

```APIDOC
## Constructors

### `AnalyticalSolarPositionProvider()`

**Description**: Constructor with default data context.

**Method**: `CONSTRUCTOR`

### `AnalyticalSolarPositionProvider(DataContext dataContext)`

**Description**: Constructor.

**Parameters**:
- `dataContext` (DataContext) - Required - data context
```

--------------------------------

### AcmSatelliteEphemeris API - Start and Stop Dates

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/class-use/AbsoluteDate

API for getting the start and end dates of the ephemeris.

```APIDOC
## AcmSatelliteEphemeris API - Start and Stop Dates

### Description
Provides access to the start and end dates of the satellite ephemeris.

### Method
`getStart` (AbsoluteDate)
`getStop` (AbsoluteDate)

### Endpoint
N/A (Methods within a class)

### Parameters
None

### Request Example
```json
{
  "example": "No request body for getter methods"
}
```

### Response
#### Success Response (200)
* For `getStart`: `AbsoluteDate` object representing the start date.
* For `getStop`: `AbsoluteDate` object representing the end date.

#### Response Example
```json
{
  "example": "AbsoluteDate object"
}
```
```

--------------------------------

### NumericalPropagator Constructors

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/numerical/NumericalPropagator

Provides details on how to instantiate a NumericalPropagator.

```APIDOC
## NumericalPropagator Constructors

### Description
Provides details on how to instantiate a NumericalPropagator.

### Constructor Detail

#### NumericalPropagator(ODEIntegrator integrator)

* **Description**: Creates a new instance of NumericalPropagator, based on orbit definition mu. After creation, the instance is empty, i.e. the attitude provider is set to an unspecified default law and there are no perturbing forces at all. This means that if `addForceModel` is not called after creation, the integrated orbit will follow a Keplerian evolution only. The defaults are `OrbitType.EQUINOCTIAL` for `propagation orbit type` and `PositionAngleType.ECCENTRIC` for `position angle type`.
This constructor uses the `default data context`.

* **Parameters**:
  * `integrator` (ODEIntegrator) - numerical integrator to use for propagation.

* **See Also**:
  * `NumericalPropagator(ODEIntegrator, AttitudeProvider)`

#### NumericalPropagator(ODEIntegrator integrator, AttitudeProvider attitudeProvider)

* **Description**: Creates a new instance of NumericalPropagator, based on orbit definition mu. After creation, the instance is empty, i.e. the attitude provider is set to an unspecified default law and there are no perturbing forces at all. This means that if `addForceModel` is not called after creation, the integrated orbit will follow a Keplerian evolution only. The defaults are `OrbitType.EQUINOCTIAL` for `propagation orbit type` and `PositionAngleType.ECCENTRIC` for `position angle type`.

* **Parameters**:
  * `integrator` (ODEIntegrator) - numerical integrator to use for propagation.
  * `attitudeProvider` (AttitudeProvider) - the attitude law.

* **Since**:
  10.1
```

--------------------------------

### Set and Get Duty Cycle Pulse Period (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/ccsds/ndm/odm/ocm/OrbitManeuverHistoryMetadata

Provides functionality to set and get the time elapsed between the start of one duty cycle pulse and the start of the next. Expects a double representing time. This defines the frequency of the duty cycle.

```Java
public void setDcTimePulsePeriod(double dcTimePulsePeriod)
public double getDcTimePulsePeriod()
```

--------------------------------

### TLEPropagator Instance Methods

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/analytical/tle/TLEPropagator

Documentation for instance methods available on TLEPropagator objects.

```APIDOC
## TLEPropagator Instance Methods

### getPVCoordinates(AbsoluteDate date)

**Description**: Get the extrapolated position and velocity from an initial TLE.

**Parameters**:
- `date` (AbsoluteDate) - the final date

**Returns**:
- (PVCoordinates) the final PVCoordinates

### sxpInitialize()

**Description**: Initialization proper to each propagator (SGP or SDP).

### sxpPropagate(double t)

**Description**: Propagation proper to each propagator (SGP or SDP).

**Parameters**:
- `t` (double) - the offset from initial epoch (min)

### resetInitialState(SpacecraftState state)

**Description**: Reset the propagator initial state.

**Parameters**:
- `state` (SpacecraftState) - the new initial state.
```

--------------------------------

### AttitudeStateHistory API - Start and Stop Dates

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/class-use/AbsoluteDate

API for getting the start and end dates of an attitude state history segment.

```APIDOC
## AttitudeStateHistory API - Start and Stop Dates

### Description
Provides access to the start and end dates of an attitude state history segment.

### Method
`getStart` (AbsoluteDate)
`getStop` (AbsoluteDate)

### Endpoint
N/A (Methods within a class)

### Parameters
None

### Request Example
```json
{
  "example": "No request body for getter methods"
}
```

### Response
#### Success Response (200)
* For `getStart`: `AbsoluteDate` object representing the start date.
* For `getStop`: `AbsoluteDate` object representing the end date.

#### Response Example
```json
{
  "example": "AbsoluteDate object"
}
```
```

--------------------------------

### Propagator Matrix Computation Setup

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/AbstractPropagator

Methods for setting up and clearing the computation of State Transition Matrices and Jacobians.

```APIDOC
## POST /matricesComputation/setup

### Description
Sets up the computation of the State Transition Matrix (STM) and Jacobians with respect to parameters. If called, these matrices will be automatically computed during propagation, and a harvester will be available to retrieve them.

### Method
POST

### Endpoint
/matricesComputation/setup

### Parameters
#### Request Body
- **stmName** (string) - Required - The state name for the State Transition Matrix.
- **initialStm** (object) - Optional - The initial State Transition Matrix (∂Y/∂Y₀). If null, a 6x6 identity matrix is assumed.
- **initialJacobianColumns** (object) - Optional - The initial columns of the Jacobians matrix with respect to parameters. If null or missing parameters, the corresponding initial column is assumed to be 0.

### Request Example
```json
{
  "stmName": "OrbitSTM",
  "initialStm": [
    [1.0, 0.0, 0.0, 0.0, 0.0, 0.0],
    [0.0, 1.0, 0.0, 0.0, 0.0, 0.0],
    [0.0, 0.0, 1.0, 0.0, 0.0, 0.0],
    [0.0, 0.0, 0.0, 1.0, 0.0, 0.0],
    [0.0, 0.0, 0.0, 0.0, 1.0, 0.0],
    [0.0, 0.0, 0.0, 0.0, 0.0, 1.0]
  ],
  "initialJacobianColumns": {
    "param1": [0.1, 0.2, 0.3, 0.4, 0.5, 0.6],
    "param2": [0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
  }
}
```

### Response
#### Success Response (200)
- **MatricesHarvester** (object) - An object representing the harvester to retrieve computed matrices.

#### Response Example
```json
{
  "harvester": {
    "stmName": "OrbitSTM",
    "isComputingSTM": true,
    "isComputingJacobians": true
  }
}
```

## DELETE /matricesComputation

### Description
Erases the internal matrices harvester, stopping the computation of STM and Jacobians.

### Method
DELETE

### Endpoint
/matricesComputation

### Parameters
None

### Request Example
None

### Response
#### Success Response (200)
- **message** (string) - Indicates that matrices computation has been cleared.

#### Response Example
```json
{
  "message": "Matrices computation cleared successfully."
}
```
```

--------------------------------

### FieldAbstractPropagator: Get Start Date Method (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/FieldAbstractPropagator

Retrieves the start date of the propagation. This protected method returns the date from which the propagation is considered to have started.

```java
protected FieldAbsoluteDate<T> getStartDate()
```

--------------------------------

### Force Model Initialization API

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/ForceModel

Methods for initializing a force model at the start of propagation.

```APIDOC
## init

### Description
Initialize the force model at the start of propagation. This method will be called before any calls to `addContribution`, `acceleration`.

### Method
`init`

### Parameters
- **initialState** (FieldSpacecraftState<T>) - Spacecraft state at the start of propagation.
- **target** (FieldAbsoluteDate<T>) - Date of propagation. Not equal to `initialState.getDate()`.

### Type Parameters
- **T** - type of the elements
```

--------------------------------

### Get Firing Start Detector (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/maneuvers/trigger/StartStopEventsTrigger

Retrieves the detector used for firing start events. This is a getter method for accessing the firing start detector instance.

```Java
public A getStartDetector()

```

--------------------------------

### BoxAndSolarArraySpacecraft Static Methods

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/BoxAndSolarArraySpacecraft

Provides documentation for the static methods used to build panels for the BoxAndSolarArraySpacecraft.

```APIDOC
## BoxAndSolarArraySpacecraft Static Methods

### Description
Static methods to assist in building panel configurations for the spacecraft.

### Method Summary

| Modifier and Type | Method | Description |
|---|---|---|
| `static List<Panel>` | `buildBox(double xLength, double yLength, double zLength, double drag, double liftRatio, double absorption, double reflection)` | Build the panels of a simple parallelepipedic box. |
| `static List<Panel>` | `buildPanels(double xLength, double yLength, double zLength, ExtendedPositionProvider sun, double solarArrayArea, Vector3D solarArrayAxis, double drag, double liftRatio, double absorption, double reflection)` | Build the panels of a simple parallelepiped box plus one solar array panel. |
```

--------------------------------

### Constructor Detail

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/analytical/BrouwerLyddanePropagator

Details on the BrouwerLyddanePropagator constructor.

```APIDOC
## BrouwerLyddanePropagator

### Description
Constructor for BrouwerLyddanePropagator.

### Method
public

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
None

#### Response Example
None
```

--------------------------------

### Get Ephemeris Start Date (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/general/OrekitEphemerisFile

Retrieves the start date of an ephemeris. This method is equivalent to calling getPropagator().getMinDate(). It returns the ephemeris start date.

```java
public AbsoluteDate getStart()

Get the start date of the ephemeris.
The date returned by this method is equivalent to  getPropagator().getMinDate(). 

Specified by:
    `getStart` in interface `EphemerisFile.SatelliteEphemeris<TimeStampedPVCoordinates,​OrekitEphemerisFile.OrekitEphemerisSegment>` 

Returns:
    ephemeris start date.
```

--------------------------------

### MultisatStepNormalizer Methods

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/sampling/MultisatStepNormalizer

Provides access to methods for handling steps, initialization, finalization, and retrieving configuration.

```APIDOC
## MultisatStepNormalizer Methods

### Description
Provides methods to manage and retrieve information about the step normalization process.

### Method
#### `getFixedTimeStep()`

##### Description
Get the fixed time step used for normalization.

##### Method
`getFixedTimeStep()`

##### Parameters
None

##### Request Example
```json
{
  "method": "getFixedTimeStep"
}
```

##### Response
* **fixedTimeStep** (double) - The fixed time step.

##### Response Example
```json
{
  "fixedTimeStep": 100.0
}
```

### Method
#### `getFixedStepHandler()`

##### Description
Get the underlying fixed step handler wrapped by this normalizer.

##### Method
`getFixedStepHandler()`

##### Parameters
None

##### Request Example
```json
{
  "method": "getFixedStepHandler"
}
```

##### Response
* **fixedStepHandler** (MultiSatFixedStepHandler) - The wrapped fixed step handler.

##### Response Example
```json
{
  "fixedStepHandler": "<MultiSatFixedStepHandler_instance>"
}
```

### Method
#### `init(List<SpacecraftState> s0, AbsoluteDate t)`

##### Description
Initialize the step handler at the start of a propagation. This method is called once at the beginning of the propagation.

##### Method
`init(List<SpacecraftState> s0, AbsoluteDate t)`

##### Parameters
* **s0** (List<SpacecraftState>) - The initial states for each satellite.
* **t** (AbsoluteDate) - The target time for the integration.

##### Request Example
```json
{
  "method": "init",
  "s0": [
    {
      "date": "2023-01-01T00:00:00.0Z",
      "attitude": {},
      "mass": 1000.0,
      "frame": "EME2000"
    }
  ],
  "t": "2023-01-01T00:00:00.0Z"
}
```

##### Response
This method does not return a value.

##### Response Example
None

### Method
#### `handleStep(List<OrekitStepInterpolator> interpolators)`

##### Description
Handle the current step of the propagation. All provided interpolators share the same time range.

##### Method
`handleStep(List<OrekitStepInterpolator> interpolators)`

##### Parameters
* **interpolators** (List<OrekitStepInterpolator>) - A list of interpolators for the current step.

##### Request Example
```json
{
  "method": "handleStep",
  "interpolators": [
    {
      "minDate": "2023-01-01T00:00:00.0Z",
      "maxDate": "2023-01-01T01:00:00.0Z"
    }
  ]
}
```

##### Response
This method does not return a value.

##### Response Example
None

### Method
#### `finish(List<SpacecraftState> finalStates)`

##### Description
Finalize the propagation, providing the states at the end of the propagation.

##### Method
`finish(List<SpacecraftState> finalStates)`

##### Parameters
* **finalStates** (List<SpacecraftState>) - The list of spacecraft states at the end of the propagation.

##### Request Example
```json
{
  "method": "finish",
  "finalStates": [
    {
      "date": "2023-01-02T00:00:00.0Z",
      "attitude": {},
      "mass": 990.0,
      "frame": "EME2000"
    }
  ]
}
```

##### Response
This method does not return a value.

##### Response Example
None
```

--------------------------------

### Get Next Maneuver Start Time - Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/ccsds/ndm/odm/ocm/OrbitManeuverHistoryMetadata

Retrieves the start time of the next maneuver. The method returns an AbsoluteDate object.

```Java
public AbsoluteDate getManNextEpoch()
```

--------------------------------

### SGP4 Method Documentation

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/analytical/tle/SGP4

Documentation for the core methods of the SGP4 class, including initialization and propagation.

```APIDOC
## SGP4 Methods

### Description
Documentation for the core methods of the SGP4 class, including initialization and propagation.

### Method: sxpInitialize
```java
protected void sxpInitialize()
```

#### Description
Initialization proper to each propagator (SGP or SDP).

#### Overrides
`sxpInitialize` in class `TLEPropagator`

### Method: sxpPropagate
```java
protected void sxpPropagate(double tSince)
```

#### Description
Propagation proper to each propagator (SGP or SDP).

#### Overrides
`sxpPropagate` in class `TLEPropagator`

#### Parameters
- **tSince** (double) - the offset from initial epoch (min)
```

--------------------------------

### Get maneuver start date - Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/maneuvers/trigger/DateBasedManeuverTriggers

Retrieves the start date of the maneuver. Returns an AbsoluteDate object.

```java
public AbsoluteDate getStartDate()
```

--------------------------------

### LightFluxModel Initialization

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/class-use/AbsoluteDate

Initializes the light flux model before propagation starts.

```APIDOC
## LightFluxModel Initialization

### Description
Initializes the light flux model before propagation starts.

### Methods

#### `init` (ConicallyShadowedLightFluxModel)

##### Description
Perform initialization steps before starting propagation.

##### Method
`void`

##### Endpoint
N/A (Method within a class)

#### `init` (LightFluxModel)

##### Description
Perform initialization steps before starting propagation.

##### Method
`default void`

##### Endpoint
N/A (Method within a class)

### Parameters
#### Path Parameters
- **initialState** (SpacecraftState) - Required - The initial state of the spacecraft.
- **targetDate** (AbsoluteDate) - Required - The target date for initialization.
```

--------------------------------

### Get Orbits Start Columns (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/estimation/sequential/UnscentedKalmanModel

Retrieves the starting column indices for orbits. This is a protected method.

```java
protected int[] getOrbitsStartColumns()
```

--------------------------------

### Get Start Screen Period Method in Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/ccsds/ndm/cdm/CdmRelativeMetadata

Retrieves the start time in UTC of the screening period for the conjunction assessment.

```java
public AbsoluteDate getStartScreenPeriod()
// Get the start time in UTC of the screening period for the conjunction assessment.
```

--------------------------------

### AbstractPropagator Constructors and Methods

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/AbstractPropagator

Documentation for the constructors and methods of the AbstractPropagator class.

```APIDOC
## AbstractPropagator

### Description
Common handling of `Propagator` methods for propagators. This abstract class allows to provide easily the full set of `Propagator` methods, including all propagation modes support and discrete events support for any simple propagation method.

### Method
abstract class

### Endpoint
N/A

### Parameters
None

### Request Example
None

### Response
None

## Constructors

### `AbstractPropagator()`

#### Description
Build a new instance.

#### Method
protected

#### Parameters
None

## Methods

### `setStartDate(AbsoluteDate startDate)`

#### Description
Set a start date.

#### Method
protected void

#### Parameters
- **startDate** (AbsoluteDate) - start date

### `getStartDate()`

#### Description
Get the start date.

#### Method
protected AbsoluteDate

#### Returns
start date

### `getAttitudeProvider()`

#### Description
Get attitude provider.

#### Method
public AttitudeProvider

#### Returns
attitude provider

### `setAttitudeProvider(AttitudeProvider attitudeProvider)`

#### Description
Set attitude provider.

#### Method
public void

#### Parameters
- **attitudeProvider** (AttitudeProvider) - attitude provider

### `getInitialState()`

#### Description
Get the propagator initial state.

#### Method
public SpacecraftState

#### Returns
the initial state

### `propagate(AbsoluteDate target)`

#### Description
Propagate towards a target date.

#### Method
public SpacecraftState

#### Parameters
- **target** (AbsoluteDate) - the target date

#### Returns
the state at the target date
```

--------------------------------

### Get seconds since Na start from GLONASSDate (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/GLONASSDate

Returns the number of seconds elapsed since the start of the current day (Na start) within the GLONASS date representation.

```Java
public double getSecInDay()
```

--------------------------------

### ShootingPropagationSettings Constructor (Full)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/control/indirect/shooting/propagation/ShootingPropagationSettings

This constructor allows full configuration of ShootingPropagationSettings by providing force models, adjoint dynamics provider, propagation frame, integration settings, and an attitude provider. This offers granular control over the propagation environment.

```java
public ShootingPropagationSettings(
    List<ForceModel> forceModels,
    AdjointDynamicsProvider adjointDynamicsProvider,
    Frame propagationFrame,
    ShootingIntegrationSettings integrationSettings,
    AttitudeProvider attitudeProvider
)
```

--------------------------------

### Initialize Propagation Models with FieldAbsoluteDate

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/class-use/FieldAbsoluteDate

Demonstrates the initialization of various propulsion and radiation force models using `FieldAbsoluteDate` and `FieldSpacecraftState`. These methods prepare models for propagation start.

```java
PropulsionModel.init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target)
AbstractManeuverTriggers.init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target)
FieldManeuverTriggersResetter.init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target)
IntervalEventTrigger.init(FieldSpacecraftState<D> initialState, FieldAbsoluteDate<D> target)
ManeuverTriggers.init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target)
AbstractManeuverTriggers.initializeResetters(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target)
ConicallyShadowedLightFluxModel.init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> targetDate)
LightFluxModel.init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> targetDate)
RadiationPressureModel.init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target)
```

--------------------------------

### SatelliteAntenna.getValidFrom

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/class-use/AbsoluteDate

Gets the start date of validity for a satellite antenna.

```APIDOC
## SatelliteAntenna.getValidFrom

### Description
Get start of validity for the satellite antenna.

### Method
Getter

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "example": "satelliteAntenna.getValidFrom()"
}
```

### Response
#### Success Response (200)
- **validFrom** (AbsoluteDate) - The start date of validity.

#### Response Example
```json
{
  "example": "AbsoluteDate object"
}
```
```

--------------------------------

### Get GeoMagneticField Validity Period Start

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/models/earth/GeoMagneticField

Returns the start of the validity period for this geomagnetic field model, expressed as a decimal year.

```java
public double validFrom() {
    // Implementation details...
    return 0.0;
}
```

--------------------------------

### ShootingPropagationSettings Constructors

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/control/indirect/shooting/propagation/ShootingPropagationSettings

Provides documentation for the constructors of the ShootingPropagationSettings class.

```APIDOC
## ShootingPropagationSettings Constructors

### Description
Documentation for the constructors of the `ShootingPropagationSettings` class, used to define propagation settings for indirect shooting methods.

### Constructor Summary

*   `ShootingPropagationSettings(List<ForceModel> forceModels, AdjointDynamicsProvider adjointDynamicsProvider, ShootingIntegrationSettings integrationSettings)`
    Simple constructor with default frame and attitude provider.

*   `ShootingPropagationSettings(List<ForceModel> forceModels, AdjointDynamicsProvider adjointDynamicsProvider, Frame propagationFrame, ShootingIntegrationSettings integrationSettings, AttitudeProvider attitudeProvider)`
    Constructor.

### Constructor Detail

#### ShootingPropagationSettings
```java
@DefaultDataContext
public ShootingPropagationSettings(
    List<ForceModel> forceModels,
    AdjointDynamicsProvider adjointDynamicsProvider,
    ShootingIntegrationSettings integrationSettings
)
```

Simple constructor with default frame and attitude provider.

**Parameters:**
* `forceModels` - forces for numerical propagation
* `adjointDynamicsProvider` - adjoint derivatives provider
* `integrationSettings` - integration settings

#### ShootingPropagationSettings
```java
public ShootingPropagationSettings(
    List<ForceModel> forceModels,
    AdjointDynamicsProvider adjointDynamicsProvider,
    Frame propagationFrame,
    ShootingIntegrationSettings integrationSettings,
    AttitudeProvider attitudeProvider
)
```

Constructor.

**Parameters:**
* `forceModels` - forces for numerical propagation
* `propagationFrame` - frame used as reference frame in equations of motion by integrator
* `adjointDynamicsProvider` - adjoint derivatives provider
* `integrationSettings` - integration settings
* `attitudeProvider` - attitude provider

```

--------------------------------

### Get Start of Validity - Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/gnss/attitude/GNSSAttitudeProvider

Retrieves the start date of validity for the GNSSAttitudeProvider. This method is inherited from the EventDetectorsProvider interface.

```java
AbsoluteDate
validityStart()

```

--------------------------------

### Set Up STM and Jacobian Generators - Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/numerical/NumericalPropagator

Sets up the handling for State Transition Matrix (STM) and Jacobian matrices. This method is an override from AbstractIntegratedPropagator, configuring the necessary components for matrix generation during propagation.

```Java
protected void setUpStmAndJacobianGenerators()
```

--------------------------------

### BoxAndSolarArraySpacecraft Instance Methods

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/BoxAndSolarArraySpacecraft

Provides documentation for the instance methods of the BoxAndSolarArraySpacecraft class, including drag and radiation calculations.

```APIDOC
## BoxAndSolarArraySpacecraft Instance Methods

### Description
Instance methods for calculating spacecraft accelerations and retrieving configuration details.

### Method Summary

| Modifier and Type | Method | Description |
|---|---|---|
| `<T extends CalculusFieldElement<T>> FieldVector3D<T>` | `dragAcceleration(FieldSpacecraftState<T> state, T density, FieldVector3D<T> relativeVelocity, T[] parameters)` | Compute the acceleration due to drag. |
| `Vector3D` | `dragAcceleration(SpacecraftState state, double density, Vector3D relativeVelocity, double[] parameters)` | Compute the acceleration due to drag. |
| `List<ParameterDriver>` | `getDragParametersDrivers()` | Get the drivers for supported parameters. |
| `List<Panel>` | `getPanels()` | Get the panels composing the body. |
| `List<ParameterDriver>` | `getRadiationParametersDrivers()` | Get the drivers for supported parameters. |
```

--------------------------------

### Get Start Epoch - Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/ilrs/ILRSHeader

Retrieves the starting epoch (UTC) for the ephemeris data. This method returns an AbsoluteDate object.

```java
public AbsoluteDate getStartEpoch()
```

--------------------------------

### Package Overview

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/bodies/class-use/OneAxisEllipsoid

This section provides a high-level overview of the different packages available in the Orekit library and a brief description of each.

```APIDOC
## Orekit Package Documentation

### Description
Provides a list of core Orekit packages and their descriptions.

### Packages
* **org.orekit.attitudes**: This package provides classes to represent simple attitudes.
* **org.orekit.bodies**: This package provides interface to represent the position and geometry of space objects such as stars, planets or asteroids.
* **org.orekit.files.ccsds.ndm.odm.ocm**: This package contains class managing CCSDS Orbit Comprehensive Message.
* **org.orekit.forces.radiation**: This package provides all radiation pressure related forces.
* **org.orekit.geometry.fov**: This package provides classes for representing a spacecraft sensor Field Of View.
* **org.orekit.gnss**: This package provides classes related to GNSS applications.
* **org.orekit.models.earth**: This package provides models that simulate certain physical phenomena of Earth and the near-Earth environment.
* **org.orekit.models.earth.atmosphere**: This package provides the atmosphere model interface and several implementations.
* **org.orekit.models.earth.displacement**: This package provides models computing reference points displacements on Earth surface.
* **org.orekit.models.earth.tessellation**: This package provides ways to do tessellation and sampling of zones of interest over an ellipsoid surface.
* **org.orekit.propagation.events**: This package provides interfaces and classes dealing with events occurring during propagation.
* **org.orekit.propagation.semianalytical.dsst.forces**: This package provides force models for Draper Semi-analytical Satellite Theory (DSST).
* **org.orekit.utils**: This package provides useful objects.
```

--------------------------------

### Get Start Date of TimeSpan

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/utils/TimeSpanMap

Retrieves the start date of this time span. This method is part of the TimeSpanMap.Span class in Orekit.

```java
public	AbsoluteDate	getStart()
```

--------------------------------

### ForceModel Initialization

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/maneuvers/Maneuver

Documentation for initializing a ForceModel at the start of propagation.

```APIDOC
## ForceModel Initialization

### Description
Initialize the force model at the start of propagation. This method will be called before any calls to `ForceModel.addContribution`, `ForceModel.acceleration`.

### Method
INIT

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
#### Success Response (200)
N/A

#### Response Example
N/A

### Parameters:
- **initialState** (SpacecraftState) - spacecraft state at the start of propagation.
- **target** (AbsoluteDate) - date of propagation. Not equal to `initialState.getDate()`.
```

--------------------------------

### Get Seconds Since Week Start (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/GNSSDate

Retrieves the number of seconds that have elapsed since the start of the current GNSS week.

```java
public double getSecondsInWeek()
```

--------------------------------

### Get Milliseconds Since Week Start (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/GNSSDate

Retrieves the number of milliseconds that have elapsed since the start of the current GNSS week.

```java
public double getMilliInWeek()
```

--------------------------------

### AggregatedPVCoordinatesProvider Methods

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/utils/AggregatedPVCoordinatesProvider

Documentation for the methods available in AggregatedPVCoordinatesProvider.

```APIDOC
## AggregatedPVCoordinatesProvider Methods

### getMinDate

```java
public AbsoluteDate getMinDate()
```

#### Description

Get the first date of the range.

#### Returns

- **AbsoluteDate** - the first date of the range.

### getMaxDate

```java
public AbsoluteDate getMaxDate()
```

#### Description

Get the last date of the range.

#### Returns

- **AbsoluteDate** - the last date of the range.

### getPosition

```java
public Vector3D getPosition(AbsoluteDate date, Frame frame)
```

#### Description

Get the position of the body in the selected frame. Copied from interface: `PVCoordinatesProvider`.

#### Parameters

- **date** (AbsoluteDate) - current date.
- **frame** (Frame) - the frame where to define the position.

#### Returns

- **Vector3D** - position of the body (m and).

### getVelocity

```java
public Vector3D getVelocity(AbsoluteDate date, Frame frame)
```

#### Description

Get the velocity of the body in the selected frame. Copied from interface: `PVCoordinatesProvider`.

#### Parameters

- **date** (AbsoluteDate) - current date.
- **frame** (Frame) - the frame where to define the velocity.

#### Returns

- **Vector3D** - velocity of the body (m/s).

### getPVCoordinates

```java
public TimeStampedPVCoordinates getPVCoordinates(AbsoluteDate date, Frame frame)
```

#### Description

Get the `PVCoordinates` of the body in the selected frame. Copied from interface: `PVCoordinatesProvider`.

#### Parameters

- **date** (AbsoluteDate) - current date.
- **frame** (Frame) - the frame where to define the position.

#### Returns

- **TimeStampedPVCoordinates** - time-stamped position/velocity of the body (m and m/s).
```

--------------------------------

### Force Model Initialization and Parameter Drivers

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/empirical/ParametricAcceleration

Provides methods for initializing a force model and retrieving its parameter drivers.

```APIDOC
## POST /force/model/init

### Description
Initializes the force model at the start of propagation with a given spacecraft state and target date.

### Method
POST

### Endpoint
/force/model/init

### Parameters
#### Request Body
- **initialState** (SpacecraftState) - Required - The spacecraft state at the start of propagation.
- **target** (AbsoluteDate) - Required - The date of propagation, which should not be equal to `initialState.getDate()`.

### Request Example
```json
{
  "initialState": "spacecraft state object at start date",
  "target": "2023-10-27T10:00:00Z"
}
```

### Response
#### Success Response (200)
- **message** (string) - Indicates successful initialization.

#### Response Example
```json
{
  "message": "Force model initialized successfully."
}
```
```

```APIDOC
## GET /force/model/parameters/drivers

### Description
Retrieves the list of parameter drivers associated with the force model.

### Method
GET

### Endpoint
/force/model/parameters/drivers

### Response
#### Success Response (200)
- **drivers** (List<ParameterDriver>) - A list of parameter drivers available for the force model.

#### Response Example
```json
{
  "drivers": [
    {
      "name": "some_parameter",
      "minValue": 0.0,
      "maxValue": 1.0,
      "selected": true
    }
  ]
}
```
```

--------------------------------

### Get Usable Start Time in Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/ccsds/ndm/odm/ocm/TrajectoryStateHistoryMetadata

Retrieves the start time of the usable time span covered by ephemerides data. This is important for proper interpolation. Returns an AbsoluteDate.

```java
public AbsoluteDate getUseableStartTime()
```

--------------------------------

### BoxAndSolarArraySpacecraft Constructor (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/BoxAndSolarArraySpacecraft

Constructs a BoxAndSolarArraySpacecraft model. Two constructors are provided: one taking a list of panels and another that builds the model with optimal solar array lighting.

```java
public BoxAndSolarArraySpacecraft(List<Panel> panels)
public BoxAndSolarArraySpacecraft(double xLength, double yLength, double zLength, ExtendedPositionProvider sun, double solarArrayArea, Vector3D solarArrayAxis, double dragCoeff, double liftRatio, double absorptionCoeff, double reflectionCoeff)
```

--------------------------------

### Get Start Date from Maneuver Triggers (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/time/class-use/AbsoluteDate

The getStartDate method in DateBasedManeuverTriggers returns the AbsoluteDate marking the start of the maneuver. This is crucial for defining the temporal window of maneuver execution.

```java
AbsoluteDate DateBasedManeuverTriggers.`getStartDate()`
```

--------------------------------

### GillIntegratorBuilder Constructor

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/conversion/GillIntegratorBuilder

Details on how to instantiate a GillIntegratorBuilder.

```APIDOC
## GillIntegratorBuilder Constructor

### Description
Build a new instance of GillIntegratorBuilder.

### Method
CONSTRUCTOR

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Constructor Signature
```java
public GillIntegratorBuilder(double step)
```

### Parameters
- **step** (double) - Required - step size in seconds (s)

### Response
N/A

### Constructor Example
```java
GillIntegratorBuilder builder = new GillIntegratorBuilder(60.0);
```
```

--------------------------------

### Get Usable Start Time

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/ccsds/ndm/odm/oem/OemMetadata

Retrieves the start time of the usable time span covered by ephemerides data. This is necessary for proper interpolation.

```APIDOC
## GET /ephemerides/usableStartTime

### Description
Gets the start of the usable time span covered by ephemerides data, which is necessary for proper interpolation.

### Method
GET

### Endpoint
/ephemerides/usableStartTime

### Parameters
#### Path Parameters
None

#### Query Parameters
None

### Request Example
(No request body for GET requests)

### Response
#### Success Response (200)
- **useableStartTime** (AbsoluteDate) - The usable start time.
```

--------------------------------

### Get Start Detector Method (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/maneuvers/trigger/StartStopEventsTrigger

Returns the start event detector used by this trigger. This detector signals the beginning of the maneuver firing interval.

```java
A getStartDetector()
```

--------------------------------

### ShootingPropagationSettings Constructor (Simple)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/control/indirect/shooting/propagation/ShootingPropagationSettings

This constructor initializes ShootingPropagationSettings using a list of force models, an adjoint dynamics provider, and integration settings. It assumes default values for the propagation frame and attitude provider.

```java
public ShootingPropagationSettings(
    List<ForceModel> forceModels,
    AdjointDynamicsProvider adjointDynamicsProvider,
    ShootingIntegrationSettings integrationSettings
)
```

--------------------------------

### OrekitStepNormalizer Constructors and Methods

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/propagation/sampling/OrekitStepNormalizer

This section details the constructors and methods available for the OrekitStepNormalizer class, including initialization, step handling, and retrieving configuration.

```APIDOC
## OrekitStepNormalizer

### Description
This class wraps an object implementing `OrekitFixedStepHandler` into a `OrekitStepHandler`. It mirrors the `StepNormalizer` interface from Hipparchus but provides a space-dynamics interface to the methods.

### Constructor Summary

| Constructor | Description |
|---|---|
| `OrekitStepNormalizer(double h, OrekitFixedStepHandler handler)` | Simple constructor. |

### Method Summary

| Modifier and Type | Method | Description |
|---|---|---|
| `void` | `finish(SpacecraftState finalState)` | Finalize propagation. |
| `OrekitFixedStepHandler` | `getFixedStepHandler()` | Get the underlying fixed step handler. |
| `double` | `getFixedTimeStep()` | Get the fixed time step. |
| `void` | `handleStep(OrekitStepInterpolator interpolator)` | Handle the last accepted step. |
| `void` | `init(SpacecraftState s0, AbsoluteDate t)` | Initialize step handler at the start of a propagation. |

## Constructor Detail

### OrekitStepNormalizer

```java
public OrekitStepNormalizer(double h, OrekitFixedStepHandler handler)
```

#### Description
Simple constructor.

#### Parameters
* **h** (double) - fixed time step (sign is not used)
* **handler** (OrekitFixedStepHandler) - fixed time step handler to wrap

## Method Detail

### getFixedTimeStep

```java
public double getFixedTimeStep()
```

#### Description
Get the fixed time step.

#### Returns
* **double** - fixed time step

Since:
11.0

### getFixedStepHandler

```java
public OrekitFixedStepHandler getFixedStepHandler()
```

#### Description
Get the underlying fixed step handler.

#### Returns
* **OrekitFixedStepHandler** - underlying fixed step handler

Since:
11.0

### init

```java
public void init(SpacecraftState s0, AbsoluteDate t)
```

#### Description
Initialize step handler at the start of a propagation. This method is called once at the start of the propagation. It may be used by the step handler to initialize some internal data if needed. The default method does nothing.

#### Parameters
* **s0** (SpacecraftState) - initial state
* **t** (AbsoluteDate) - target time for the integration

Specified by:
`init` in interface `OrekitStepHandler`

### handleStep

```java
public void handleStep(OrekitStepInterpolator interpolator)
```

#### Description
Handle the last accepted step.

#### Parameters
* **interpolator** (OrekitStepInterpolator) - interpolator for the last accepted step. For efficiency purposes, the various propagators reuse the same object on each call, so if the instance wants to keep it across all calls (for example to provide at the end of the propagation a continuous model valid throughout the propagation range), it should build a local copy using the clone method and store this copy.

Specified by:
`handleStep` in interface `OrekitStepHandler`

### finish

```java
public void finish(SpacecraftState finalState)
```

#### Description
Finalize propagation.

#### Parameters
* **finalState** (SpacecraftState) - state at propagation end

Specified by:
`finish` in interface `OrekitStepHandler`
```

--------------------------------

### Get Start Date Method (Java)

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/forces/maneuvers/trigger/DateBasedManeuverTriggers

Retrieves the start date of the maneuver. This method returns an AbsoluteDate object, indicating when the maneuver is scheduled to begin.

```java
AbsoluteDate
getStartDate()
```

--------------------------------

### PVCoordinatesProvider Interface

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/utils/PVCoordinatesProvider

This section provides documentation for the methods available in the PVCoordinatesProvider interface.

```APIDOC
## PVCoordinatesProvider Interface

### Description
Interface for PV coordinates providers. The PV coordinates provider interface can be used by any class used for position/velocity computation, for example celestial bodies or spacecraft position/velocity propagators, and many others...

### Method Summary

| Method                     | Description                                     |
|----------------------------|-------------------------------------------------|
| `getPosition`              | Get the position of the body in the selected frame. |
| `getPVCoordinates`         | Get the `PVCoordinates` of the body in the selected frame. |
| `getVelocity`              | Get the velocity of the body in the selected frame.   |

### Method Detail

#### getPosition

```java
default Vector3D getPosition(AbsoluteDate date, Frame frame)
```

Get the position of the body in the selected frame.

**Parameters:**
- `date` (AbsoluteDate) - current date
- `frame` (Frame) - the frame where to define the position

**Returns:**
- `Vector3D` - position of the body (m and)

**Since:**
- 12.0

#### getVelocity

```java
default Vector3D getVelocity(AbsoluteDate date, Frame frame)
```

Get the velocity of the body in the selected frame.

**Parameters:**
- `date` (AbsoluteDate) - current date
- `frame` (Frame) - the frame where to define the velocity

**Returns:**
- `Vector3D` - velocity of the body (m/s)

**Since:**
- 13.1

#### getPVCoordinates

```java
TimeStampedPVCoordinates getPVCoordinates(AbsoluteDate date, Frame frame)
```

Get the `PVCoordinates` of the body in the selected frame.

**Parameters:**
- `date` (AbsoluteDate) - current date
- `frame` (Frame) - the frame where to define the position

**Returns:**
- `TimeStampedPVCoordinates` - time-stamped position/velocity of the body (m and m/s)
```

--------------------------------

### Get Validity Start Date - Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/gnss/attitude/Glonass

Retrieves the start date for the validity of the attitude provider. This method is part of the GNSSAttitudeProvider interface and returns an AbsoluteDate object.

```java
public AbsoluteDate validityStart()

Get start of validity for this provider.
Specified by:
    validityStart in interface GNSSAttitudeProvider
Returns:
    start of validity for this provider
```

--------------------------------

### Get Ephemeris Start Date in Java

Source: https://www.orekit.org/site-orekit-13.1.1/apidocs/org/orekit/files/general/EphemerisFile

Retrieves the start date of the ephemeris data for the satellite. This date is equivalent to the minimum date of the propagator obtained from this ephemeris.

```java
AbsoluteDate getStart()

```