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You can configure the Orbit Determination Properties for a Sensor through FreeFlyer script or the Object Browser. There are two ways to navigate to the "Antenna Model" page of the Sensor object editor:


1.Open the desired Sensor's editor and select the Antenna Model page

2.Highlight the desired Sensor on the "Objects to Process" page of a Kalman Filter, Square Root Information Filter, Unscented Kalman Filter, or Batch Least Squares object editor and click the "Modify Sensor Estimation Options" button


From this page, you can configure any of these options:


The Sensor ID, transmitter frequency, and receiver frequency

The Sensor properties that you want to ignore, estimate, or consider

oIgnore: Leave the property out of the estimated state.

oEstimate: Include the property in the estimated state and allow the estimator to update its value.

oConsider: Include the property in the estimated state, but do NOT allow the estimator to update its value. This means that the property gets included in the covariance, but is not directly estimated.

The A Priori Bias, Sigma, and Process Noise for each of the properties


Sensor OD Properties

Sensor OD Properties


To define the Sensor properties that you want to estimate or consider via FreeFlyer script, you will access the Sensor's OD properties, as shown in the example below:


Spacecraft1.Sensors[0].OD.TimeTagBias.ProcessAction = 1;


// Spacecraft-to-Spacecraft Observation Sensor Properties

// Properties to Estimate

Spacecraft1.Sensors[0].OD.SpacecraftObservation.Azimuth.Bias.ProcessAction   = 1;

Spacecraft1.Sensors[0].OD.SpacecraftObservation.Elevation.Bias.ProcessAction = 1;


// Properties to Ignore

Spacecraft1.Sensors[0].OD.SpacecraftObservation.Range.Bias.ProcessAction          = 0;

Spacecraft1.Sensors[0].OD.SpacecraftObservation.RangeRate.Bias.ProcessAction      = 0;

Spacecraft1.Sensors[0].OD.SpacecraftObservation.RightAscension.Bias.ProcessAction = 0;

Spacecraft1.Sensors[0].OD.SpacecraftObservation.Declination.Bias.ProcessAction    = 0;


Once the Sensor has been configured, it can be attached to a GNSS Receiver, Transponder, or TDRS Transponder, and used as an observing object, object being observed, or TDRS relay when simulating tracking data or including tracking data in an estimation process.


The Attached Sensors page of the GNSS Receiver, Transponder, and TDRS Transponder object editors allow you to indicate any Sensors that will be attached to the hardware for simulating or processing OD tracking data. The Sensor's X, Y, and Z position properties will be used to model an offset from the origin of the Spacecraft body coordinate system (BCS) when modeling measurements. You can also specify the Sensors to attach or detach via FreeFlyer script:







Sensor Measurement Model

When the observer is a Sensor, you can configure the measurement model (including the noise, maximum, and minimum values) for each of the following measurement types:



Range Rate



Right Ascension



You can configure these values through the Object Browser by double-clicking on the desired Spacecraft and navigating to the "Sensors" page under the Orbit Determination section, highlighting the desired Sensor and selecting "Edit Sensor". The panel that pops up is shown in the image below:


The Sensor Measurement Model Editor

The Sensor Measurement Model Editor


You can also configure these options through FreeFlyer script, by accessing various properties of the Sensor object:


// Range and RangeRate Measurement Model

Spacecraft1.Sensors[0].OD.SpacecraftObservation.Range.Noise     = 0.02;

Spacecraft1.Sensors[0].OD.SpacecraftObservation.RangeRate.Noise = 0.0001;


// Angles Measurement Model

Spacecraft1.Sensors[0].OD.SpacecraftObservation.Azimuth.Noise   = 0.1;

Spacecraft1.Sensors[0].OD.SpacecraftObservation.Elevation.Noise = 0.1;


Spacecraft1.Sensors[0].OD.SpacecraftObservation.RightAscension.Noise = 0.1;

Spacecraft1.Sensors[0].OD.SpacecraftObservation.Declination.Noise    = 0.1;



See Also


Sensor Properties and Methods

SensorODProperties Properties and Methods