Sensor Models¶

Simulated SSN ground sensor producing az/el/range (radar) or angles-only az/el (optical) measurements.

SensorType ¶

SensorType()

Sensor measurement type, driving measurement-model selection.

Parsed from the sensor_type dataset property: AZEL_RANGE sensors (radar/phased-array/mechanical trackers, dataset value "azel_range") measure [az, el, range]; AZEL sensors (angles-only optical trackers, dataset value "azel") measure [az, el].

Example

import brahe as bh
sites = bh.datasets.ssn_sensors.load()
sensor = bh.SimpleSSNSensor.from_location(sites[0])
if sensor.sensor_type == bh.SensorType.AZEL_RANGE:
    print("radar sensor")

Initialize instance.

AZEL `class-attribute` ¶

AZEL: Any = SensorType.AZEL

Sensor measurement type, driving measurement-model selection.

Parsed from the sensor_type dataset property: AZEL_RANGE sensors (radar/phased-array/mechanical trackers, dataset value "azel_range") measure [az, el, range]; AZEL sensors (angles-only optical trackers, dataset value "azel") measure [az, el].

Example

import brahe as bh
sites = bh.datasets.ssn_sensors.load()
sensor = bh.SimpleSSNSensor.from_location(sites[0])
if sensor.sensor_type == bh.SensorType.AZEL_RANGE:
    print("radar sensor")

AZEL_RANGE `class-attribute` ¶

AZEL_RANGE: Any = SensorType.AZEL_RANGE

Sensor measurement type, driving measurement-model selection.

Parsed from the sensor_type dataset property: AZEL_RANGE sensors (radar/phased-array/mechanical trackers, dataset value "azel_range") measure [az, el, range]; AZEL sensors (angles-only optical trackers, dataset value "azel") measure [az, el].

Example

import brahe as bh
sites = bh.datasets.ssn_sensors.load()
sensor = bh.SimpleSSNSensor.from_location(sites[0])
if sensor.sensor_type == bh.SensorType.AZEL_RANGE:
    print("radar sensor")

SimpleSSNSensor ¶

SimpleSSNSensor(location: Any, az_min: Any = 0.0, az_max: Any = 360.0, el_min: Any = 0.0, el_max: Any = 90.0, range_max: Any = None, bias: Any = Ellipsis, noise: Any = Ellipsis, seed: Any = None)

A simulated SSN ground sensor producing az/el/range or angles-only az/el measurements.

Pairs a sensor site (location, field-of-view limits, bias/noise calibration) with measurement generation. Radar (azel_range) sensors measure [az, el, range]; optical sensors measure [az, el]. Angles are in degrees, range in meters. The azimuth window is wrap-aware: az_min > az_max means the window crosses north (e.g. Cape Cod 347deg -> 227deg).

Example

import brahe as bh
sites = bh.datasets.ssn_sensors.load()
sensors = bh.SimpleSSNSensor.from_locations(sites, seed=42)

Initialize instance.

az_max `property` ¶

az_max: float

Azimuth window end (degrees).

Returns:

Name	Type	Description
`float`	`float`	Azimuth window end.

az_min `property` ¶

az_min: float

Azimuth window start (degrees).

Returns:

Name	Type	Description
`float`	`float`	Azimuth window start.

calibrated `property` ¶

calibrated: bool

Whether the sensor's site supplied full noise calibration.

Returns:

Name	Type	Description
`bool`	`bool`	True if all three noise fields were present; False for sensors loaded with default zero noise.

el_max `property` ¶

el_max: float

Maximum elevation (degrees).

Returns:

Name	Type	Description
`float`	`float`	Maximum elevation.

el_min `property` ¶

el_min: float

Minimum elevation (degrees).

Returns:

Name	Type	Description
`float`	`float`	Minimum elevation.

location `property` ¶

location: PointLocation

Sensor site location.

Returns:

Name	Type	Description
`PointLocation`	`PointLocation`	Sensor site location.

measurement_dim `property` ¶

measurement_dim: int

Measurement dimension: 3 for radar (az/el/range), 2 for optical (az/el).

Returns:

Name	Type	Description
`int`	`int`	Length of the vector returned by measure().

name `property` ¶

name: str

Sensor name (from the site location).

Returns:

Name	Type	Description
`str`	`str`	Sensor name.

range_max `property` ¶

range_max: Union[float, None]

Maximum range (meters), if limited.

Returns:

Type	Description
`Union[float, None]`	float or None: Maximum range, or None if unlimited.

sensor_type `property` ¶

sensor_type: SensorType

Sensor measurement type.

Returns:

Name	Type	Description
`SensorType`	`SensorType`	`SensorType.AZEL_RANGE` (radar; `[az, el, range]`) or `SensorType.AZEL` (optical; `[az, el]`).

azelrange `method descriptor` ¶

azelrange(epoch: Epoch, state: ndarray) -> ndarray

True (noise-free, bias-free) az/el/range of a target.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Measurement epoch.	required
`state`	`ndarray`	Target ECI state (first 3 elements used; meters).	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: [azimuth_deg, elevation_deg, range_m].

from_location `staticmethod` ¶

from_location(location: PointLocation, seed: Union[int, None] = None) -> SimpleSSNSensor

Build a sensor from a dataset site's properties.

Supports sensor_type == "azel_range" (radar; [az, el, range]) and sensor_type == "azel" (angles-only optical trackers; [az, el]). Noise fields default to zero when absent, flagging the sensor uncalibrated; radar sites read az/el/range noise, optical sites read az/el noise. Bias fields default to zero when absent; limits default to an open field of view (azimuth 0-360deg, elevation 0-90deg, unlimited range). Optical sites carry no range fields, so they have no range constraint.

Parameters:

Name	Type	Description	Default
`location`	`PointLocation`	Site from e.g. `bh.datasets.ssn_sensors.load()`.	required
`seed`	`int or None`	RNG seed for reproducible measurements.	`None`

Returns:

Name	Type	Description
`SimpleSSNSensor`	`SimpleSSNSensor`	New sensor instance.

Raises:

Type	Description
`ValueError`	If the site is missing a `sensor_type` property or has an unrecognized one.

from_locations `staticmethod` ¶

from_locations(locations: list[PointLocation], seed: Union[int, None] = None) -> SimpleSSNSensor

Build sensors from all constructible sites, skipping unsupported ones.

Sites with an unknown sensor_type are skipped, but sites lacking calibration are still included with zero noise. Both radar (azel_range) and optical (azel) sites construct. When seed is provided, sensor i is seeded with seed + i for reproducible measurement generation. Use from_locations_calibrated to keep only fully-calibrated sites.

Parameters:

Name	Type	Description	Default
`locations`	`list[PointLocation]`	Candidate sites.	required
`seed`	`int or None`	Optional base RNG seed.	`None`

Returns:

Type	Description
`SimpleSSNSensor`	list[SimpleSSNSensor]: One sensor per constructible site.

Example

import brahe as bh
sites = bh.datasets.ssn_sensors.load()
sensors = bh.SimpleSSNSensor.from_locations(sites, seed=42)

from_locations_calibrated `staticmethod` ¶

from_locations_calibrated(locations: list[PointLocation], seed: Union[int, None] = None) -> SimpleSSNSensor

Build sensors from constructible, fully-calibrated sites only.

Like from_locations but drops sites that did not supply every noise field their type measures (az/el/range for radar, az/el for optical), i.e. sensors whose calibrated is False.

Parameters:

Name	Type	Description	Default
`locations`	`list[PointLocation]`	Candidate sites.	required
`seed`	`int or None`	Optional base RNG seed.	`None`

Returns:

Type	Description
`SimpleSSNSensor`	list[SimpleSSNSensor]: One sensor per constructible, calibrated site.

measure `method descriptor` ¶

measure(epoch: Epoch, state: ndarray) -> Union[ndarray, None]

Generate one measurement if the target is visible (step-wise API).

Visibility is evaluated on the true geometry; the returned measurement is truth + bias + noise with azimuth normalized into [0, 360). The measurement is 3-dim [az, el, range] for azel_range sensors and 2-dim [az, el] for optical sensors.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Measurement epoch.	required
`state`	`ndarray`	True target ECI state (meters).	required

Returns:

Type	Description
`Union[ndarray, None]`	numpy.ndarray or None: [az_deg, el_deg, range_m] ([az_deg, el_deg] for optical) when visible, None otherwise.

measurement_model `method descriptor` ¶

measurement_model() -> Any

Filter-side measurement model matching this sensor.

The model uses the sensor's noise standard deviations for its noise covariance and the sensor's bias in predict(), so an estimator configured with this model is consistent with measurements generated by measure(). Returns an AzElRangeMeasurementModel for radar (az/el/range) sensors and an AzElMeasurementModel for optical (angles-only) sensors.

Returns:

Type	Description
`Any`	AzElRangeMeasurementModel \| AzElMeasurementModel: Matching model in degrees.

simulate_observations `method descriptor` ¶

simulate_observations(trajectory: OrbitTrajectory, start: Epoch, end: Epoch, dt: float, model_index: int) -> list[Observation]

Generate observations over a trajectory segment (batched API).

Samples the trajectory at cadence dt over [start, end] (inclusive) and calls measure() at each sample; non-visible samples are skipped. Pass detection is intentionally not performed here.

Parameters:

Name	Type	Description	Default
`trajectory`	`OrbitTrajectory`	Interpolatable ECI trajectory of the target.	required
`start`	`Epoch`	First sample epoch.	required
`end`	`Epoch`	Last sample epoch (inclusive).	required
`dt`	`float`	Sample interval (seconds, > 0).	required
`model_index`	`int`	Observation.model_index to tag measurements with.	required

Returns:

Type	Description
`list[Observation]`	list[Observation]: Observations for every visible sample.

Raises:

Type	Description
`ValueError`	If dt <= 0.

visible `method descriptor` ¶

visible(epoch: Epoch, state: ndarray) -> bool

Whether a target is inside the sensor's field of view.

Checks elevation limits, the wrap-aware azimuth window, and maximum range.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Measurement epoch.	required
`state`	`ndarray`	Target ECI state (first 3 elements used; meters).	required

Returns:

Name	Type	Description
`bool`	`bool`	True if the target is within the field of view.

with_bias `method descriptor` ¶

with_bias(bias_az_deg: float, bias_el_deg: float, bias_range_m: float) -> SimpleSSNSensor

Override the sensor's measurement bias.

The derived measurement_model reads these values.

Parameters:

Name	Type	Description	Default
`bias_az_deg`	`float`	Azimuth bias (degrees).	required
`bias_el_deg`	`float`	Elevation bias (degrees).	required
`bias_range_m`	`float`	Range bias (meters).	required

Returns:

Name	Type	Description
`SimpleSSNSensor`	`SimpleSSNSensor`	The sensor with updated bias.

Raises:

Type	Description
`ValueError`	If any bias is non-finite.

with_constraint `method descriptor` ¶

with_constraint(constraint: Union[ElevationConstraint, OffNadirConstraint, LocalTimeConstraint, LookDirectionConstraint, AscDscConstraint, ElevationMaskConstraint, ConstraintAll, ConstraintAny, ConstraintNot]) -> SimpleSSNSensor

Add an extra field-of-view constraint (extension point).

The constraint is evaluated by visible alongside the limits-derived constraints, so users can extend visibility with arbitrary access constraints (e.g. ElevationConstraint, AzimuthConstraint, RangeConstraint, LookDirectionConstraint).

Parameters:

Name	Type	Description	Default
`constraint`	`AccessConstraint`	An access constraint object, e.g. ElevationConstraint, AzimuthConstraint, or RangeConstraint.	required

Returns:

Name	Type	Description
`SimpleSSNSensor`	`SimpleSSNSensor`	The sensor with the constraint appended.

with_noise `method descriptor` ¶

with_noise(sigma_az_deg: float, sigma_el_deg: float, sigma_range_m: float) -> SimpleSSNSensor

Override the sensor's noise standard deviations.

The derived measurement_model reads these values.

Parameters:

Name	Type	Description	Default
`sigma_az_deg`	`float`	Azimuth noise standard deviation (degrees).	required
`sigma_el_deg`	`float`	Elevation noise standard deviation (degrees).	required
`sigma_range_m`	`float`	Range noise standard deviation (meters).	required

Returns:

Name	Type	Description
`SimpleSSNSensor`	`SimpleSSNSensor`	The sensor with updated noise.

Raises:

Type	Description
`ValueError`	If any sigma is negative or non-finite.

Sensor Models¶

SensorType ¶

AZEL class-attribute ¶

AZEL_RANGE class-attribute ¶

SimpleSSNSensor ¶

az_max property ¶

az_min property ¶

calibrated property ¶

el_max property ¶

el_min property ¶

location property ¶

measurement_dim property ¶

name property ¶

range_max property ¶

sensor_type property ¶

azelrange method descriptor ¶

from_location staticmethod ¶

from_locations staticmethod ¶

from_locations_calibrated staticmethod ¶

measure method descriptor ¶

measurement_model method descriptor ¶

simulate_observations method descriptor ¶

visible method descriptor ¶

with_bias method descriptor ¶

with_constraint method descriptor ¶

with_noise method descriptor ¶

See Also¶

AZEL `class-attribute` ¶

AZEL_RANGE `class-attribute` ¶

az_max `property` ¶

az_min `property` ¶

calibrated `property` ¶

el_max `property` ¶

el_min `property` ¶

location `property` ¶

measurement_dim `property` ¶

name `property` ¶

range_max `property` ¶

sensor_type `property` ¶

azelrange `method descriptor` ¶

from_location `staticmethod` ¶

from_locations `staticmethod` ¶

from_locations_calibrated `staticmethod` ¶

measure `method descriptor` ¶

measurement_model `method descriptor` ¶

simulate_observations `method descriptor` ¶

visible `method descriptor` ¶

with_bias `method descriptor` ¶

with_constraint `method descriptor` ¶

with_noise `method descriptor` ¶