Radiometer Model

The radiometer model is based on the reference listed below. The following system types are supported: total-power, unbalanced-Dicke, balanced-Dicke and noise-adding. The following scan types are supported: fixed (no scan), cross-track and conical.

The FOV of the instrument is calculated from the antenna specifications (beamwidth), scan-type and the instrument orientation. A sceneFOV can be specified separately. The FOR is built based on the sceneFOV and the maneuver specifications. The sceneFOV/ FOR is used in the coverage calculations (using the OrbitPy package) to find the locations accessed on the ground.

Todo

Field-of-view for conical-scan radiometers.

Note

See Glossary for names of the variables used in any discussion below.

References:

Chapter 6,7 in “Microwave Radar and Radiometric Remote Sensing,” David Gardner Long , Fawwaz T. Ulaby 2014

Model parameters

A RadiometerModel object can be obtained from a json/ dict by using the from_json(.) or from_dict(.) functions. The expected key/value pairs are described below:

Input parameter description
Parameter	Data type	Units	Description
@type	string		Must be Radiometer
@id	string		Unique identifier for the instrument. If `None` a random string is assigned.
name	string		Full name of the instrument
mass	float	kilograms	Total mass of this entity.
volume	float	\(m^3\)	Total volume of this entity.
power	float	Watts	Nominal operating power.
orientation	orientation json object		Orientation of the instrument. Default is alignment to the SC_BODY_FIXED frame.
fieldOfViewGeometry	fieldOfViewGeometry (Spherical-Geometry) json object		Field of view spherical geometry specification of the instrument.
sceneFieldOfViewGeometry	sceneFieldOfViewGeometry json object		The SceneFOV spherical geometry specification of the instrument. Default is the field-of-view spherical geometry.
maneuver	maneuver json object		Maneuver specifications (see Maneuverability and Field Of Regard (FOR) calculations).
pointingOption	pointingOption JSON object		List of orientations to which the instrument axis can be maneuvered.
dataRate	float	Mega-bits-per-s	Rate of data recorded during nominal operations.
bitsPerPixel	integer		Bits encoded per pixel of image.
antenna	antenna JSON object		Antenna specifications.
operatingFrequency	float	Hertz	Operating center frequency.
system	system JSON object		Radiometer system.
scan	scan JSON object		Scan specifications. Default is a FIXED specification (no-scan).
targetBrightnessTemperature	float	Kelvin	Target brightness temperature. Default value is 290K.

`system` JSON object

The radiometer-system refers to the electronics configuration from the antenna to the output of the integrator. Following system-types can be modelled: TOTAL_POWER, UNBALANCED_DICKE, BALANCED_DICKE or NOISE_ADDING.

The antenna, operatingFrequency and the targetBrightnessTemperature specifications of the system are obtained as external inputs when required to compute some system parameters and the radiometric performance. In each of the systems, the predetection stage parameters can be specified in two ways: (1) component-level specification or (2) black-box specification.

The key/value pairs of each of the system types is described below:

"@type":"TOTAL_POWER"

The expected key/value pairs for a total-power radiometer system system excluding that of the predetection-stage are given below.

Common parameters

Parameter

Data type

Units

Description

@type

string

Must be TOTAL_POWER

integrationTime

float

seconds

Integration time.

bandwidth

float

Hertz

Pre-detection bandwidth.

integratorVoltageGain

float

Integrator voltage gain.

Below are the expected key/value pairs of the predetection stage (black-box specification).

Predetection stage parameters (black-box specification)

Parameter

Data type

Units

Description

predetectionGain

float

decibels

Pre-detection stage gain.

predetectionInpNoiseTemp

float

Kelvin

Pre-detection input noise temperature.

predetectionGainVariation

float

Pre-detection stage gain variation. Linear units.

Below are the expected key/value pairs of the predetection stage (component-level specification).

Predetection stage parameters (component-level specification)

Parameter

Data type

Units

Description

tlLoss

float

decibels

Transmission line loss.

tlPhyTemp

float

Kelvin

Transmission line physical temperature.

rfAmpGain

float

decibels

RF amplifier gain.

rfAmpInpNoiseTemp

float

Kelvin

RF amplifier input noise temperature.

rfAmpGainVariation

float

RF amplifier gain variation. Linear units.

mixerGain

float

decibels

Mixer gain.

mixerInpNoiseAmp

float

Kelvin

Mixer input noise temperature.

mixerGainVariation

float

Mixer gain variation. Linear units.

ifAmpGain

float

decibels

Intermediate frequency amplifier gain.

ifAmpInpNoiseTemp

float

Kelvin

Intermediate frequency amplifier input noise temperature.

ifAmpGainVariation

float

IF amplifier gain variation. Linear units.

Example:

Total-power System with component-level predetection-stage specification.
tpr_sys1_json = {"tlLoss": 0.5,
                 "tlPhyTemp": 290,
                 "rfAmpGain": 30,
                 "rfAmpInpNoiseTemp": 200,
                 "rfAmpGainVariation": 10,
                 "mixerGain": 23,
                 "mixerInpNoiseTemp": 1200,
                 "mixerGainVariation": 2,
                 "ifAmpGain": 30,
                 "ifAmpInputNoiseTemp": 100,
                 "ifAmpGainVariation": 10,
                 "integratorVoltageGain": 1,
                 "integrationTime": 100e-3,
                 "bandwidth": 10e6,
                }
Total-power System with block-box predetection-stage specification.
tpr_sys2_json = {"predetectionGain": 83,
                 "predetectionInpNoiseTemp": 200,
                 "predetectionGainVariation": 2000000,
                 "integrationTime": 100e-3,
                 "bandwidth": 10e6,
                 "integratorVoltageGain": 1
                }

"@type":"UNBALANCED_DICKE"

The expected key/value pairs for a unbalanced-Dicke radiometer system system is similar to the TOTAL_POWER system.

The expected key/value pairs for a unbalanced-Dicke radiometer system system excluding that of the predetection-stage consists of all the kep/value pairs of the TOTAL_POWER system and the referenceTemperature key/value pair. The @type key must have “UNBALANCED_DICKE” as the value.

Common parameters

Parameter

Data type

Units

Description

@type

string

Must be UNBALANCED_DICKE

referenceTemperature

float

Kelvin

Reference source noise temperature.

The expected key/value pairs of the predetection stage (black-box specification) is the same as that of the TOTAL_POWER system.

The expected key/value pairs of the predetection stage (component-level specification) consists of all the key/value pairs of the TOTAL_POWER system and the dickeSwitchOutputNoiseTemperature key/value pair.

Predetection stage parameters (component-level specification)

Parameter

Data type

Units

Description

dickeSwitchOutputNoiseTemperature

float

Kelvin

Dicke switch noise temperature referenced to the output port.

"@type":"BALANCED_DICKE"

The expected key/value pairs for a balanced-Dicke radiometer system system is similar to the TOTAL_POWER system.

The expected key/value pairs for a unbalanced-Dicke radiometer system system excluding that of the predetection-stage consists of all the kep/value pairs of the TOTAL_POWER system. The @type key must have “BALANCED_DICKE” as the value.

Common parameters

Parameter

Data type

Units

Description

@type

string

Must be BALANCED_DICKE

The expected key/value pairs of the predetection stage (black-box specification) is the same as that of the TOTAL_POWER system.

The expected key/value pairs of the predetection stage (component-level specification) consists of all the key/value pairs of the TOTAL_POWER system and the dickeSwitchOutputNoiseTemperature key/value pair.

Predetection stage parameters (component-level specification)

Parameter

Data type

Units

Description

dickeSwitchOutputNoiseTemperature

float

Kelvin

Dicke switch noise temperature referenced to the output port.

"@type":"NOISE_ADDING"

The expected key/value pairs for a noise-adding radiometer system system is similar to the TOTAL_POWER system.

The expected key/value pairs for a unbalanced-Dicke radiometer system system excluding that of the predetection-stage consists of all the kep/value pairs of the TOTAL_POWER system and the excessNoiseTemperature key/value pair. The @type key must have “NOISE_ADDING” as the value.

Common parameters

Parameter

Data type

Units

Description

@type

string

Must be NOISE_ADDING

excessNoiseTemperature

float

Kelvin

Excess noise temperature (added noise to the receiver input during the diode ON half-cycle) in Kelvin referenced to the output port.

The expected key/value pairs of the predetection stage (black-box specification) is the same as that of the TOTAL_POWER system.

The expected key/value pairs of the predetection stage (component-level specification) is the same as that of the TOTAL_POWER system.

`scan` JSON object

Three scan-techniques are supported: FIXED (no-scan), CROSS_TRACK and CONICAL. The scan-technique determines the instrument field-of-view (and hence the swath-width), dwell-time (and hence the maximum integration-time).

"@type":"FIXED"

This scan-technique specifies that there is no scan. The antenna (and the feeder) is held fixed with respect to the spacecraft. No parameters are required.

Example:
```
"scan":{
      "@type": "FIXED"
}
```

"@type":"CROSS_TRACK"

In this scan-technique the antenna foot-print is scanned in the cross-track direction. The scanWidth parameter specifies the angular width about the instrument orientation (which in general is SIDE_LOOK), while the interScanOverheadTime specifies the time taken to go from scan of one strip (in the cross-track direction) to the next.

Parameter

Data type

Units

Description

scanWidth

float

degrees

Angular scan-width.

interScanOverheadTime

float

seconds

Time taken from ending current scan to starting next scan. Significant in case of mechanical scanning. Default value is 0.

Example:
"scan":{
         "@type": "CROSS_TRACK,
         "scanWidth": 120,
         "interScanOverheadTime": 1e-3
       }

"@type":"CONICAL"

In this scan-technique the antenna footprint is scanned along the cone-perimeter. The offNadirAngle specifies the (half) cone angle while the clockAngleRange parameter specifies the azimuth extent of the scan (symmetrically about the along-track direction). The interScanOverheadTime specifies the time taken to go from scan of one strip to the next.

For illustration of off-nadir angle and clock angles see Fig.7 in T. Kawanishi et al., “The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E), NASDA’s contribution to the EOS for global energy and water cycle studies,” in IEEE Transactions on Geoscience and Remote Sensing, vol. 41, no. 2, pp. 184-194, Feb. 2003.

Parameter

Data type

Units

Description

offNadirAngle

float

degrees

Off-nadir angle (i.e. the half-cone angle of the conical scan).

clockAngleRange

float

degrees

Scan clock angle range in degrees.

interScanOverheadTime

float

seconds

Time taken from ending current scan to starting next scan. Significant in case of mechanical scanning. Default value is 0.

Example:
"scan": {
         "offNadirAngle": 30,
         "clockAngleRange": 60,
         "interScanOverheadTime": 1e-3
         }

Model results

Using the radiometer model, coverage calculations (using the OrbitPy package) can be carried out over a region of interest. Coverage calculations which involve a grid (list of grid-points) evaluate to see if the grid-points fall within the instrument sceneFOV (sceneFOV = FOV in most cases) or the FOR. The pointing-options feature further allows to automate coverage calculations for numerous instrument orientations.

Once the coverage has been evaluated, the observable locations and the observer (satellite) locations is known. The following data metrics at the observable location on the surface of Earth can be calculated:

Observation data metrics table
Metric/Aux data	Data Type	Units	Description
radiometric res [K]	float	Kelvin	Radiometric resolution/ sensitivity.
ground pixel along-track resolution [m]	float	meters	Along-track resolution of an ground-pixel centered about observation point.
ground pixel cross-track resolution [m]	float	meters	Cross-track resolution of an ground-pixel centered about observation point.
swath-width [m]	float	meters	Swath-width of the strip of which the imaged pixel is part off.
beam efficiency	float		Beam efficiency of the antenna.
incidence angle [deg]	float	degrees	Observation incidence angle at the ground-pixel.

Note

Coverage calculations for radiometers with conical-scan is currently not supported unless a sceneFOV has been explicitly specified.

Todo

The along-track and cross-track pixel resolutions are accurate only for pixels imaged at strictly sidelooking geometry (roll-only, no pitch). Needs revision.

Model description

Below text lays down the formulae coded into the model based on reference [1].

Viewing geometry

The viewing geometry parameters, i.e. \(\mathbf{S}\), \(\mathbf{T}\), \(\mathbf{R}\), \(\theta_i\) and \(\gamma\) are determined using the setup described in basic sensor model description.

Pixel-resolutions

Note that the current formulation is accurate only when ground-pixel is being imaged at the nadir or is at purely side-looking geometry.

\(\rho_{at} = R \mu_{at}\)

\(\rho_{ct} = R \mu_{ct}/ \cos(\theta_i)\)

Todo

Update for the general target geometry.

Radiometric resolution

Integration time calculation

The dwell-time \(t_d\) of the antenna over a pixel gives the maximum possible integration time. It depends on the scan technique:

FIXED

\(t_d = \rho_{at}/v_{g}\)
CROSS_TRACK

\(n_{pps} = \Delta_{asw} / \rho_{ct}\)

\(t_d = \dfrac{\rho_{at}/v_{g} - \Delta_{is}}{n_{pps}}\)
CONICAL

\(n_{pps} = \Delta_{car} / \rho_{ct}\)

\(t_d = \dfrac{\rho_{at}/v_{g} - \Delta_{is}}{n_{pps}}\)

FInally, if the calculated dwell time is lesser than the user-defined integration-time, the integration-time is set to the calculated dwell time, else the integration time is set to the user-specified integration-time.

\(if \hspace{2mm} \tau_{spec} > t_d, \hspace{2mm} \tau = t_d\) else \(\tau = \tau_{spec}\)

Predetection section parameters

The predetection stage includes all subsystems between the antenna and the input terminals of the square-law detector (Pg 273, Fig.7-13 in [1]). The specifications of the radiometric system can be made by either defining the specification of the entire predetection stage (as a black-box) or of their individual components.

If the black-box specifications are provided:

\(G_{PD}^- = G_{PD} - 0.5 \Delta G_{PD}\)

\(G_{PD}^+ = G_{PD} + 0.5 \Delta G_{PD}\)

If the component-level specifications are provided:

(Fig.7-9 in [1] describes the gain of the transmission line as 1/L, where L is the transmission line loss.)

\(G_{TL} = 1/L\) (transmission line “gain”)

\(G_{PD} = G_{TL} G_{RF} G_{MIX} G_{IF}\)

\(G_{PD}^- = G_{TL} * (G_{RF} - 0.5 \Delta G_{RF}) (G_{MIX} - 0.5 \Delta G_{MIX}) (G_{IF} - 0.5 \Delta G_{IF})\)

\(G_{PD}^+ = G_{TL} * (G_{RF} + 0.5 \Delta G_{RF}) (G_{MIX} + 0.5 \Delta G_{MIX}) (G_{IF} + 0.5 \Delta G_{IF})\)

(See Section 7-3.1 in [1] for example calculation of noise temperature from cascaded stages.)

\(T_{REC} = T_{RF} + T_{MIX}/ G_{RF} + T_{IF}/ (G_{RF} G_{IF})\) (Eqn 7.29 in [1])

\(T'_{REC} = (L-1) T_{TL}^{P} + L T_{REC}\)

In case of UNBALANCED_DICKE and BALANCED_DICKE radiometer-system:

\(T'_{REC} = T'_{REC} + T_{DSW}^o\)

System parameters

Calculate system gain factor (eqn 7.43 in [1]):

\(G_s = 2 G_{INT} G_{PD} k_B B\)

Calculate the system gain variation:

\(G_s^- = 2 G_{INT} G_{PD}^- k_B B\)

\(G_s^+ = 2 G_{INT} G_{PD}^+ k_B B\)

\(\Delta G_s = G_s^+ - G_s^-\)

\(\bar{G_s} = G_s\) (average system power gain, TODO: check)

Calculate system temperature:

(antenna radiation efficiency (\(\psi\)) = 1/ antenna loss)

\(T_A = \psi T'_A + (1-psi) T_A^p\)

\(T_{SYS} = T_A + T'_{REC}\) (eqn 7.31 in [1])

Resolution calculation

TOTAL_POWER radiometer system:

\(\Delta T = T_{SYS} \sqrt{\dfrac{1}{B \tau} + (\dfrac{\Delta G_{SYS}}{\bar{G_{SYS}}})^2}\)

UNBALANCED_DICKE radiometer system:

\(\Delta T = \sqrt{\dfrac{2 T_{SYS}^2 + 2 (T_{REF} + T'_{REC})^2}{B \tau} + (\dfrac{\Delta G_{SYS}}{\bar{G_{SYS}}})^2 (T_A - T_{REF})^2}\)

BALANCED_DICKE radiometer system:

\(\Delta T = 2 \dfrac{T_{SYS}}{\sqrt{B \tau}}\)

NOISE_ADDING radiometer system:

\(\Delta T = 2 \dfrac{T_{SYS}}{\sqrt{B \tau}} (1 + \dfrac{2 T_{SYS}}{T_{N}''})\)

Instrument field-of-View spherical-geometry calculations

The instrument field-of-view depends on the chosen scan technique and antenna specifications.

FIXED scan:

The FOV spherical-geometry shape is determined by the antenna shape (CIRCULAR or RECTANGULAR).

\(\theta_{AT} = \mu_{at}\)

\(\theta_{CT} = \mu_{ct}\)

Note that for circular antenna shape :math`mu_{at} = mu_{ct}`.

CROSS_TRACK scan:

The FOV spherical-geometry shape is always RECTANGULAR.

\(\theta_{AT} = \mu_{at}\)

\(\theta_{CT} = \mu_{ct} + \Delta_{asw}\)

CONICAL scan:

TBD. The instrument orientation has to be nadir-pointing.

Swath-width

THe swath-width is calculated from the instrument look-angle and not the look-angle to the target ground-point. The swath-width depends on the scan technique.

FIXED and CROSS_TRACK scan:

In case of fixed-scan mode, there is only 1 imaged ground-pixel per swath. Swath-width is computed to be equal to the antenna-footprint cross-track size. See Fig.5.1.3.1 in Spaceborne SAR Study: LDRD 92 Final Report SANDIA Report March 1993.

\(R_S = R_E + h\)

\(\gamma_n = \gamma_I - 0.5 \hspace{1mm} \theta_{CT}\)

\(\gamma_f = \gamma_I + 0.5 \hspace{1mm} \theta_{CT}\)

\(\theta_{in} = \sin^{-1}(\sin(\gamma_n) R_S/R_E)\)

\(\theta_{if} = \sin^{-1}(\sin(\gamma_f) R_S/R_E)\)

\(\alpha_n = \theta_{in} - \gamma_n\)

\(\alpha_f = \theta_{if} - \gamma_f\)

if \(\gamma_n\) <= 0, the radiometer footprint falls in the nadir-direction, and we have:

\(\alpha_s = \alpha_f + \alpha_n\)

if \(\gamma_n\) > 0 we have:

\(\alpha_s = |\alpha_f - \alpha_n|\)

\(W_{gr} = R_E \alpha_s\)

(\(\theta_{CT} = \mu_{ct}\) for the vase of FIXED scan.)

Note

The swath-width is calculated more precisely as compared to the pixel-resolution calculations. This leads to a small but noticeable difference while examining the results of a FIXED scan radiometer, in which the swath-width should be equal to the pixel-size in the cross-track direction.

CONICAL scan:

Calculate the radius of the small-circle on the Earth surface on which the imaged arc lies.

\(\theta_i^{cs} = \sin^{-1}(\sin(\gamma^{cs}) \dfrac{R_S}{R_E})\)

\(\alpha^{cs} = \theta_i^{cs} - \gamma^{cs}\)

\(r^{cs} = R_E \sin{\alpha^{cs}}\)

\(A^{cs} = \Delta_{car} r^{cs}\)

Beam-efficiency

Please refer to the antenna description.

Examples

Please see the examples folder.

Glossary

\(\mathbf{R}\): Range vector from satellite to target ground point.
\(\theta_i\): Incidence angle at the target ground point.
\(R_E\): Nominal equatorial radius of Earth.
\(c\): Speed of light.
\(h\): Altitude of the satellite.
\(\lambda\): Operating center wavelength of the radiometer.
\(\rho_{at}\): Along-track pixel resolution.
\(\rho_{ct}\): Cross-track pixel resolution.
\(\mu_{AT}\): Along-track antenna FOV.
\(\mu_{CT}\): Cross-track antenna FOV.
\(\theta_{AT}\): Along-track instrument FOV.
\(\theta_{CT}\): Cross-track instrument FOV.
\(v_g\): Ground speed of satellite footprint.
\(t_d\): Dwell time available over the ground-pixel.
\(\tau\): Integration time.
\(\tau_{spec}\): Integration time specification from user.
\(\Delta_{asw}\): Angular scan width in case of CROSS_TRACK scan.
\(\Delta_{car}\): Clock angle range (of scan) in case of CONICAL scan.
\(n_{pps}\): Number of pixels per strip in case of CROSS_TRACK and CONICAL scans.
\(\Delta_{is}\): Overhead time to go switch scan from one strip to another in case of CROSS_TRACK and CONICAL scans.
\(G_{PD}\): Predetection gain (linear units).
\(G_{PD}^+\): Predetection gain + (linear units).
\(G_{PD}^-\): Predetection gain - (linear units).
\(\Delta G_{PD}\): Predetection Gain variation (linear units).
\(L\): Transmission line loss (linear units).
\(G_{TL}\): Transmission line gain.
\(G_{RF}\): RF amplifier gain.
\(G_{MIX}\): Mixer gain.
\(G_{IF}\): IF (Intermediate frequency) amplifier gain.
\(\Delta G_{RF}\): RF amplifier gain variation.
\(\Delta G_{MIX}\): Mixer gain variation.
\(\Delta G_{IF}\): IF amplifier gain variation.
\(T_{REC}\): Predetection stage (excluding the transmission line from antenna to the RF amplifier) input noise temperature. (Receiver noise temperature.)
\(T'_{REC}\): Predetection stage (including the transmission line from antenna to the RF amplifier) input noise temperature. (Receiver noise temperature referred to the antenna terminals.)
\(T_{RF}\): RF amplifier input noise temperature.
\(T_{MIX}\): Mixer input noise temperature.
\(T_{IF}\): IF amplifier input noise temperature.
\(T_{TL}^{P}\): Transmission line physical temperature.
\(T_{DSW}^o\) : Dicke switch output noise temperature.
\(G_s\): System Gain (linear units).
\(G_{INT}\): Integrator voltage gain.
\(B\): Predetection bandwidth.
\(k_B\): Boltzmann constant.
\(G_s^-\): System Gain - (linear units).
\(G_s^+\): System Gain + (linear units).
\(\Delta G_s\): System Gain variation (linear units).
\(\psi\): Antenna radiation efficiency (= 1/ antenna loss).
\(T_A^p\): Antenna physical temperature.
\(T'_A\): Scene brightness temperature \(T_B(\theta,\phi)\), weighted with the antenna pattern.
\(T_A\): Antenna (radiometric) temperature referred at the output terminal of the antenna.
\(\bar{G_s}\): Average system gain.
\(T_{SYS}\): System noise temperature.
\(\Delta T\): Radiometric resolution of the radiometer.
\(T_{REF}\): Reference noise temperature for Dicke radiometer systems.
\(T_{N}''\): Excess noise temperature for NOISE_ADDING radiometer system.
\(R_S\): Distance of satellite from center of Earth.
\(\gamma_I\): Instrument look angle.
\(R_n\): Slant-range to near edge of swath.
\(R_f\): Slant-range to far edge of swath.
\(\gamma_n\): Look angle to nearest (to the satellite) part of swath.
\(\gamma_f\): Look angle to farthest (to the satellite) part of swath.
\(\theta_{in}\): Incidence angle to nearest (to the satellite) part of swath.
\(\theta_{if}\): Incidence angle to farthest (to the satellite) part of swath.
\(\theta_{im}\): Incidence angle at ground corresponding to the instrument look-angle (~middle of swath).
\(\alpha_n\): Core angle of nearest part of swath.
\(\alpha_f\): Core angle of farthest part of swath.
\(\alpha_m\): Core angle corresponding to the instrument look-angle (~middle of swath).
\(W_{gr}\): Swath-width in case of FIXED and CROSS_TRACK scans.
\(\gamma^{cs}\): CONICAL scan off-nadir angle (= look angle to the scanned strip).
\(\theta_i^{cs}\): Incidence angle to the CONICAL scan strip.
\(\alpha^{cs}\): Earth centric angle (angle b/w the nadir position to the scanned strip about center of Earth) in CONICAL scan swath calculations.
\(r^{cs}\): Small circle (on Earth) radius in CONICAL scan swath calculations.
\(A^{cs}\): Scanned arc length (CONICAL scan).

Radiometer Model

Model parameters

system JSON object

scan JSON object

Model results

Model description

Viewing geometry

Pixel-resolutions

Radiometric resolution

Integration time calculation

Predetection section parameters

System parameters

Resolution calculation

Instrument field-of-View spherical-geometry calculations

Swath-width

Beam-efficiency

Examples

Glossary

`system` JSON object

`scan` JSON object