EOIR Radiometric Properties

The Radiometric tab is available for a sensor when you select Sensor Type as EOIR on the sensor properties Definition page. Use this tab to define the radiant energy measurement properties of the sensor.

Saturation and Sensitivity

Make selections regarding EOIR's saturation and sensitivity approach using the following setting choices:

Setting	Description
Units of Saturation and Sensitivity	Selecting one of the following types: Irradiance. The Sensitivity and Dynamics Range parameters operate in irradiance units (W cm^-2). Irradiance is better suited for sensors that are observing point sources like stars. Radiance. The Sensitivity and Dynamics Range parameters operate in radiance units (W cm^-2 sr^-1). Radiance is better suited for sensors that are observing resolved images, where object shapes are discernible.
Simulate Saturation	Select this check box to have EOIR simulate saturation. Then pixels can only measure up to the specified saturation level of radiant signal. This is the way physical detectors would behave. Saturation defines the "brightest" signal that the sensor can measure.
Simulate Quantization	Select this check box to have EOIR simulate quantization. EOIR then performs the analog to digital conversion of the output image. To maintain realism, EOIR applies the quantization noise to the NEI/NER dark noise when you do NOT select this check box (don't simulate quantization).

Setting

Description

Units of Saturation and Sensitivity

Selecting one of the following types:

Irradiance. The Sensitivity and Dynamics Range parameters operate in irradiance units (W cm^-2). Irradiance is better suited for sensors that are observing point sources like stars.
Radiance. The Sensitivity and Dynamics Range parameters operate in radiance units (W cm^-2 sr^-1). Radiance is better suited for sensors that are observing resolved images, where object shapes are discernible.

Simulate Saturation

Select this check box to have EOIR simulate saturation. Then pixels can only measure up to the specified saturation level of radiant signal. This is the way physical detectors would behave. Saturation defines the "brightest" signal that the sensor can measure.

Simulate Quantization

Select this check box to have EOIR simulate quantization. EOIR then performs the analog to digital conversion of the output image.

To maintain realism, EOIR applies the quantization noise to the NEI/NER dark noise when you do NOT select this check box (don't simulate quantization).

Radiometric parameter input mode

From the Input shortcut menu, select whether to use High Level or Low Level radiometric parameters.

High Level parameters

You can populate and edit sensor performance data with measurements from an actual sensor or estimates for a sensor being developed.

Sensitivity defines the "noise floor" of the sensor. The sensor will not detect signals below this level. Use the table in the Sensitivity section of the page to enter the following data:

Parameter

Description

Integration Time

Enter the time in msec. For a definition of integration time, see the subsection in this topic called "Specifying an integration time."

Equivalent Value

Enter the Equivalent Value for Noise Equivalent Irradiance/Radiance (NEI/NER) vs. Integration Time.

To maintain realism, EOIR applies the quantization noise to the NEI/NER dark noise when you do NOT select the Simulate Quantization check box (don't simulate quantization).

Dynamic Range is the ratio of the brightest signal to the noise floor. Use the table in the Dynamic Range section of the page to enter the following data:

Parameter	Description
Integration Time	Enter the time in msec. For a definition of integration time, see the subsection in this topic called "Specifying an integration time."
Equivalent Value	Enter the Equivalent Value for Saturation Equivalent Irradiance/Radiance (SEI/SER) vs. Integration Time.

For each of these tables, you can do the following:

Click Add to add another pair to the table.
Select a pair entry and click Remove to delete it.
Click Remove All to delete all the table entries.

Low Level parameters

Specify the following radiometric parameters:

Parameter	Description
Quantum Efficiency Mode	Select the method for specifying the Quantum Efficiency (QE) value. The options are Band Effective and Spectral Response.
Spectral QE File	Click the ellipsis button to choose a file of SRF-formatted spectral profile of QE values. This is only available when you choose Spectral Response as the Quantum Efficiency Mode.
QE	Enter a spectrally flat band-effective quantum efficiency value in e-/photon. The default value is 1.0. This is only avaliable when you choose Band Effective as the Quantum Efficiency Mode.
Detector Fill Factor	Enter the portion of the detector area that is photosensitive, expressed as a ratio between 0.0 and 1.0. The default value is 1.0.
Read Noise	Enter the root-mean-square number of the electrons-per-pixel (e-/pixel) noise from reading out the charge. The default value is 1.0.
Dark Current Rate	Specify the average rate of accumulated dark noise per detector in e-/s pixel.

Analog to Digital Conversion

You can specify the following parameters for converting analog to digital.

Parameter	Description
( method)	Select a method for specifying the analog to digital quantization. Choose one of the following options: Bit-Depth and Noise Bit-Depth and QSS Full-Well and Noise Full-Well and QSS where QSS is quantization step size. The noise value is specified by the equation Noise = (dark current * integration time) + read noise, which becomes the QSS.
Full-Well Capacity	Specify the maximum number of electrons per detector (e-/pixel), i.e., where a detector will saturate. The default value is 100,000.000, and the maximum value is 1e15. This only applies to the Full-Well methods.
Digital Bit-Depth	Specify the number of bits to quantize the dynamic range of the signal into digital counts. The default value is 8. This only applies to the Bit-Depth methods.
Quantization Step Size	Specify the number of electrons per digital count in the quantized digital output. The default value is 100.0, and the maximum value is 1e12. This only applies to the Bit-Depth methods.

Specifying an integration time

When preparing to take measurements with the sensor model, you specify an Integration Time. This is the time interval over which a radiant signal is collected before generating an image. The longer the time, the more photons get collected. This field is equivalent to the "exposure time" setting on an old analog film camera.

The sensor model uses the Integration Time to interpolate into the Edit tables to compute Dynamic Range and NEI/NER and SEI/SER. In the case where the selected Integration Time is outside of the bounds of numbers entered in the table or there was only a single point entered, a physics-based approximation is used to extrapolate Dynamic Range, NEI/NER, and SEI/SER.

For additional information, see EOIR Model Description and Validation (PDF).