Figure of Merit Access Constraint Types
The types of access constraints available to you through the Constraints field on the Figure of Merit's
| Constraint | Description |
|---|---|
| Altitude | This is the apparent altitude or true altitude depending on the grid instance of the coverage definition. |
| AngleToAsset |
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| AngularRate | This is the angular rate is the rotational rate of one object that is necessary to keep a fixed vector in that object's body-fixed coordinate system aligned with the line of sight between the two objects. |
| ApparentTime | This represents the start and end local apparent times, using local apparent time at noon when the Sun is at the same longitude as the satellite. It is also known as Local Satellite Time (LST). |
| AtmosLoss | See Atmospheric Absorption Models. |
| AzimuthAngle | For facilities, places, and targets, azimuth is measured in the local horizontal plane, tangent to the surface of the central body. This angle is measured from the local north direction towards the local east direction. An azimuth of 0 degrees specifies a location directly to the north and an azimuth of 180 degrees specifies a location directly to the south. For ships, ground vehicles and aircraft, the azimuth is measured from the projection of the earth fixed velocity vector. For other objects, azimuth is measured in the plane perpendicular to nadir from the projection of the inertial velocity vector to the projection of the relative position vector. This angle is measured in a positive sense according to the right-hand rule about the nadir vector. An azimuth of 0 degrees specifies a location directly in front of the object and an azimuth of 180 degrees specifies a location directly behind the object. |
| AzimuthRate | The azimuth rate is the rate of change of the azimuth angle. |
| BitErrorRate | Limits the bit error rate. |
| BER+I | Limits the bit error rate, taking the effects of interference into account. |
| BetaAngle | The solar beta angle is the signed angle of the vector to the Sun relative to the orbital plane. The signed angle is positive when the vector to the Sun is in the direction of the orbit normal. The orbit normal is parallel to the orbital angular momentum vector, which is defined as the cross-product of the inertial position and velocity vectors. |
| C/I | This is the carrier-to-interference ratio.
Due to the volatile nature of the C/I parameters, the sampling may not be able to precisely capture the threshold. |
| C/N | Limits the true carrier-to-noise ratio. This value includes any pre-receive gains and losses that may be defined for the receiver as well as propagation losses. |
| C/(N+I) | Limits the true carrier-to-noise ratio, taking the effects of interference into account. |
| C/No | Limits the carrier-to-noise density ratio measured at the antenna output. This value includes any pre-receive gains and losses that may be defined for the receiver as well as propagation losses. |
| C/(No+Io) |
The carrier to (noise + interference) ratio (C/(No+Io)) where C is the carrier power, No = kT (Boltzmann's constant * system temperature) and Io = interference power spectral density.
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| CBObstruction | Uses selected central bodies as additional central body constraints. |
| CloudsFogLoss | See Clouds and Fog Models. |
| Comm Plugin | A constraint defined by a user-supplied plugin script. |
| CrdnAngle | Restrict access to intervals during which the selected angle is within the specified minimum and maximum limits. |
| CrdnCondition |
This constraint is based on the selected Condition component from the Calculation tool. Using the Calculation tool, you can configure Condition components by selecting Scalar components and either minimum, maximum, or both limits. The condition is satisfied when the value of its Scalar components falls within specified limits, which is similar to standard Access constraints with minimum and/or maximum limits. During Access computations, the Condition component is sampled judiciously and its satisfaction intervals are determined again, which is similar to other standard Access constraints. When reported or graphed, the Condition component returns: -1 when it is not satisfied +1 when it is satisfied 0 when it is directly on the satisfaction boundary |
| CrdnVectorMag | Use this to restrict access to intervals during which the selected vector is within the specified minimum and maximum limits. |
| CrossTrackRange | Min and Max values set in the Cross Track Range area represent the distance, measured on the surface of the Earth, from the target location to the plane defined by the cross-product of the Earth-fixed position and velocity of the object. The Min and Max values are measured in both positive and negative directions along the Z axis of the coordinate system. |
| DeltaT/T | This is the interference-to-noise ratio, which is the ratio of jammer power spectral density to receiver noise power spectral density.
Due to the volatile nature of the DeltaT/T parameters, the sampling may not be able to precisely capture the threshold. |
| DopplerConeAngle | Measured with respect to the +/- Earth Fixed velocity vector directions. Access within the defined cones is precluded. This constraint is typically used to model the collection area for radars. |
| DopplerShift | Limits the amount of frequency shift due to the relative velocities of the objects involved. The constraint values specify the frequency range relative to the transmitted frequency. For example, if the transmitted frequency is 5 GHz and the Min and Max Doppler Shift are 100 kHz, the allowed frequency range is 4.9999 to 5.0001 GHz. |
| Eb/No | Limits the bit energy to noise power density ratio. These values include all pre-demodulation gains and losses. |
| Eb/(No+Io) |
This is the energy per bit to (noise + interference) ratio (Eb/(No+Io)) where Eb is the energy per bit, No = kT (Boltzmann's constant * system temperature) and Io = interference power spectral density.
|
| ElevationAngle | For objects other than facilities, places, and targets, elevation is measured as the angle between the nadir vector and the relative position vector minus 90 degrees. The elevation angle is positive for objects above the plane perpendicular to nadir. For facilities, places, and targets, elevation is measured as the angle above the local horizontal plane where the local horizontal plane is tangent to the surface of the central body. The elevation angle is positive for objects above the local horizontal plane. |
| ElevationRate | The elevation rate is the rate of change of the elevation angle. |
| ElevationRiseSet | The Rise-Set Elevation angle constraint enables you to specify different elevation angle limits for the rise-stage and setting-stage of a satellite. For example, a receiver (attached to a sensor and/or a facility) will acquire a rising satellite only when it is 15 degrees above horizon, and will track it down to a 5 degree elevation angle when the satellite is setting.
This constraint provides additional flexibility as compared to the normal Elevation angle constraint which applies the same elevation angle limits on the rising and/or setting phase of a satellite. |
| FluxDensity | Limits the power flux density at the receiver. This value represents the flux density as seen by the receiver, including all pre-receive gains and losses that may be defined for the receiver as well as propagation losses. |
| FreeSpaceLoss | See Urban Propagation Wireless InSite Model. |
| Frequency | Limits the range of frequencies to those to which the receiver responds. |
| G/T | This is the receiver gain divided by the system noise temperature. It is the most common Figure Of Merit for describing the performance of a receiver. |
| GeoExclusion | Use this to specify the minimum angle between the direction to the target object and the direction to any point of the geo belt. As of STK 11.x, Earth obstruction is modeled, so that only those points on the geo belt that are visible from the site's ground location are considered when computing the minimum angle. |
| GrazingAlt | This is the nearest distance that the line of sight between the satellite and the other object comes to the Earth defines the grazing altitude. Use this constraint to prevent a communications link between the two objects from moving too far down into the atmosphere, which might degrade the quality of the link.
The grazing altitude is only evaluated along the path between the two objects. If both objects are "in front", meaning relative to the center of the Earth, then the constraint will return a value equal to the altitude of the closest object to the earth. It does not extend the vector past the "to object" to see if that results in a smaller grazing altitude. An example of when this might occur is a GEO satellite looking down at a missile launch. |
| GrazingAngle | Describes how high one object appears above the edge of the Earth (or limb) relative to the satellite. Measured relative to the satellite, as the angle between the Earth limb and the other object. Use this constraint to prevent a sensitive optical sensor, such as those on the Hubble Space Telescope, from aiming too close to the Earth, which might blind the sensor due to reflections off the surface. |
| GroundSampleDistance | Resolution Constraints for sensors enable you to limit access based on sensor characteristics and the quality of the objects in the sensor's view. The Ground Sample Distance is the smallest size of an object on the ground that can be detected by the sensor. It applies to facilities, places, and targets, and is based upon the access geometry and the physical attributes of the sensor. Enter the minimum and maximum Ground Sample Distance in the units of measurement specified at the scenario level. |
| HeightAboveHorizon | This is the minimum and/or maximum height of the facility, place, or target above the horizon. |
| InTrackRange | You can specify the Min and Max values set for In Track Range represent the distance, measured along the ground track on the surface of the Earth, from the sub-satellite point to the point on the ground track nearest the target. Positive values are measured in the positive direction along the Y axis of the coordinate system and negative values are measured in the negative direction along the Y axis of the coordinate system. |
| J/S | This is the jamming to signal ratio, virtually the inverse of C/I. |
| Latitude | It indicates latitude boundaries. You can specify a latitude boundary within which accesses to the vehicle must fall in order to be valid. Specify the Minimum and Maximum latitude values to define the latitude boundary. |
| LinkEIRP | This is EIRP (in dB) computed in the direction of the link being established at the current time instant between a transmitter and a receiver. It is obtained by computing the gain (dB) in the direction of the link and then adding the final transmitter amplifier power (dB) to it. |
| LinkMargin | Allows for filtering of report results based on the Link Margin calculation. |
| LocalTime | You can spcify the start and end local time constraints. The object local time is computed based upon the GMT of interest and the longitude of the object at that time. For every degree of east longitude, 4 minutes are added to GMT to yield the object local time. |
| LOSLunarExclusion | This is the minimum angle between the line of sight from the source object to the object of interest and the line of sight from the source object to the Moon for which access is considered valid. If the line between the source object and the Moon is obstructed for example, the Earth is between a satellite source object and the Moon), then the exclusion constraint is not applied. |
| LOSSunExclusion | The minimum angle between the line of sight from the source object to the object of interest and the line of sight from the source object to the Sun for which access is considered valid. For example, enter 5 degrees in the text field if you want to ignore access to another object if it is within 5 degrees of the Sun (exclusion angle is 5 degrees). If the line between the source object and the Sun is obstructed — for example, the Earth is between a satellite source object and the Sun — then STK does not apply the exclusion constraint. |
| LunarElevationAngle | Min and Max values represent the elevation angle to the apparent position of the Moon. |
| Matlab | This is a constraint defined by a user-supplied MATLAB plugin script. |
| Noise Temperature | See Noise Constraints. |
| ObjectExclusionAngle |
Indicates objects that are to be excluded from access computations if they are at the indicated angle from the original object. The other object that is used to compute the exclusion angle is not selected here, but is instead selected on the Special Constraint page of the object used as the parent CoverageDefinition's Grid Point Object. For more information, see the Object Exclusion Angle constraint. If the line between the source object and the special body is obstructed — for example, the earth is between a satellite source object and the special body — then STK does not apply the exclusion constraint. |
| PolRelAngle | This is the relative angle between the transmitter's plane of polarization and the receiver's plane of polarization. It is computed dynamically at each time step from transmitter and receiver position and attitude information. Polarization mismatch between the receiver and the transmitter antennas transmits into a loss value in dB. |
| PowerAtReceiverInput | This is the received power at the input of the receiver front end amplifier, i.e., after the antenna and the cables etc. This accounts for the antenna gain, cable losses, etc., and is adjusted for polarization mismatch loss. |
| PowerFluxDensity | This is the flux density computed over a reference bandwidth defined in the CommSystem. |
| PropagationDelay | Access to the object is constrained by the minimum and maximum time it takes the signal to travel between the two objects. |
| PropLoss | See Urban Propagation Wireless InSite Model. |
| RainLoss | See Rain Loss Models. |
| Range | The range is measured as the distance between the two objects. |
| RangeRate | Range rate is the component of the relative velocity along the line of sight of the two objects. |
| RcvdIsotropicPower | Specifies the minimum and maximum desired received isotropic power level at the receiver antenna input. This range represents the received isotropic power as seen by the receiver and includes any pre-receive gains and losses that may be defined for the receiver as well as propagation losses. |
| UserCustomALoss | See Custom Loss Plugin Models. |
| UserCustomBLoss | See Custom Loss Plugin Models. |
| UserCustomCLoss | See Custom Loss Plugin Models. |
| SarAreaRate | This is the coverage rate of the SAR radar. Enter Min and/or Max area rate as the ratio of the selected distance unit squared to the selected time unit. |
| SarAzRes | This is the fixed azimuth resolution or the resolution achievable within the desired integration time, depending on the setting of the analysis mode when defining the SAR radar. Enter Min and/or Max azimuth resolution. |
| SarCNR | You can specify the clutter-to-noise ratio for a SAR radar. Enter Min and/or Max SCR. |
| SarCNRJamming | You can specify a clutter-to-noise ratio that includes the effects of jamming for the SAR radar. |
| SarIntTime | This is the fixed integration time or time to achieve the desired azimuth resolution, depending on the setting of the analysis mode when defining a SAR radar. Enter Min and/or Max integration time. |
| SarJOverS | This is the jamming-to-signal ratio for the SAR radar. |
| SarOrthoPolCNR | This is the clutter-to-noise ratio for the SAR radar with orthogonal polarization enabled on the receiver side. |
| SarOrthoPolCNRJamming | This is the clutter-to-noise ratio that includes the effects of jamming for the SAR radar with orthogonal polarization enabled on the receiver side. |
| SarOrthoPolJOverS | This is the jamming-to-signal ratio for a SAR radar with orthogonal polarization enabled on the receiver side. |
| SarOrthoPolPTCR | This is the point target-to-clutter ratio for a SAR radar with orthogonal polarization enabled on the receiver side. |
| SarOrthoPolSCR | This is the signal-to-clutter ratio for a SAR radar with orthogonal polarization enabled on the receiver side. |
| SarOrthoPolSCRJamming | This is the signal-to-clutter ratio that includes the effects of jamming for a SAR radar with orthogonal polarization enabled on the receiver side. |
| SarOrthoPolSNR | This is the signal-to-noise ratio for a SAR radar with orthogonal polarization enabled on the receiver side. |
| SarOrthoPolSNRJamming | This is the signal-to-noise ratio that includes the effects of jamming for a SAR radar with orthogonal polarization enabled on the receiver side. |
| SarPTCR | This is the point target-to-clutter ratio for a SAR radar. Enter the Min and/or Max PTCR. |
| SarSCR | This is the signal-to-clutter ratio for a SAR radar. Enter the Min and/or Max SCR. |
| SarSCRJamming | This is the signal-to-clutter ratio that includes the effects of jamming for a SAR radar. Enter the Min and/or Max SCR. |
| SarSNR | This is the signal-to-noise ratio for a SAR radar. Enter Min and/or Max SCR. |
| SarSNRJamming | This is the signal-to-noise ratio that includes the effects of jamming for a SAR radar. |
| SarSigmaN | Additive noise is commonly defined in terms of Sigma N, which is the effective backscatter coefficient of the additive noise for the SAR radar. Enter the Min and/or Max value. |
| SpectralFluxDensity | The Flux Density is computed across the receiver's bandwidth, as seen by the receiver's RF front end. The bandwidth is the receiver's total bandwidth. |
| SquintAngle | Min and Max values set in the Squint Angle area represent the angle subtended by the Cross Track Ground Range, which is the angle between the object's Earth-fixed velocity vector and a line of sight from the object to the target measured on the surface of the Earth. |
| SrchTrkDwellTime | The sum of the integration time and RF propagation delays for the Search/Track radar. Enter Min and/or Max values. |
| SrchTrkDwellTimeJamming | This is the sum of the integration time and RF propagation delays that includes the effects of jamming for a Search/Track radar. |
| SrchTrkIntegratedJOverS | This is the integrated jamming-to-signal ratio for a Search/Track radar. |
| SrchTrkIntegratedPDet | This is the integrated pulse probability of detection for a Search/Track radar. Enter the maximum and/or minimum values in the range 0-1. The constraint calculation uses the number of pulses integrated value computed by the Search/Track radar according to the pulse integration mode. |
| SrchTrkIntegratedPDetJamming | This is the integrated pulse probability of detection that includes the effects of jamming for a Search/Track radar. Enter the maximum and/or minimum values in the range 0-1. The constraint calculation uses the number of pulses integrated value computed by the Search/Track radar according to the pulse integration mode. |
| SrchTrkIntegratedSNR | This is the integrated signal-to-noise ratio for a Search/Track radar. Enter the Min and/or Max values in the selected ratio unit. this constraint is not available if operating in Goal SNR analysis mode for integration gain. |
| SrchTrkIntegratedSNRJamming | This is the integrated signal-to-noise ratio that includes the effects of jamming for a Search/Track radar. Enter the Min and/or Max values in the selected ratio unit. This constraint is not available if operating in Goal SNR analysis mode for integration gain. |
| SrchTrkIntegrationTime | This is the integration time for a Search/Track radar required to achieve the goal SNR. Enter the Min and/or Max values. This constraint is available only if operating in Goal SNR analysis mode. |
| SrchTrkIntegrationTimeJamming | This is the integration time that includes the effects of jamming for a Search/Track radar required to achieve the goal SNR. Enter the Min and/or Max values. This constraint is available only if operating in Goal SNR analysis mode. |
| SrchTrkOrthPolDwellTime | This is the sum of the integration time and RF propagation delays a Search/Track radar's orthogonal polarization channel. Enter the Min and/or Max values. |
| SrchTrkOrthPolDwellTimeJamming | This is the sum of the integration time and RF propagation delays that includes the effects of jamming of a Search/Track radar's orthogonal polarization channel. Enter the Min and/or Max values. |
| SrchTrkOrthPolIntegratedJOverS | This is the integrated jamming to signal ratio for a Search/Track radar with orthogonal polarization enabled on the receiver side. |
| SrchTrkOrthPolIntegratedPDet | This is the integrated pulse probability of detection. Enter maximum and/or minimum values in the range 0-1. This constraint uses the number of pulses integrated value computed according to the pulse integration mode by the Search/Track radar with orthogonal polarization enabled on the receiver side. |
| SrchTrkOrthPolIntegratedPDetJamming | This is the integrated pulse probability of detection that includes the effects of jamming for a Search/Track radar. Enter maximum and/or minimum values in the range 0-1. This constraint uses the number of pulses integrated value computed according to the pulse integration mode by a Search/Track radar with orthogonal polarization enabled on the receiver side. |
| SrchTrkOrthPolIntegratedSNR | This is the integrated signal-to-noise ratio for a Search/Track radar with orthogonal polarization enabled on the receiver side. Enter Min and/or Max values in the selected ratio unit. This constraint is not available if operating in Goal SNR analysis mode for integration gain. |
| SrchTrkOrthPolIntegratedSNRJamming | This is the integrated signal-to-noise ratio that includes the effects of jamming for a Search/Track radar with orthogonal polarization enabled on the receiver side. Enter Min and/or Max values in the selected ratio unit. This constraint is not available if operating in Goal SNR analysis mode for integration gain. |
| SrchTrkOrthPolIntegrationTime | This is the integration time required to achieve the goal SNR for a Search/Track Radar with orthogonal polarization enabled on the receiver side. Enter Min and/or Max values. This constraint is available only if operating in Goal SNR analysis mode. |
| SrchTrkOrthPolIntegrationTimeJamming | This is the integration time that includes the effects of jamming required to achieve the goal SNR for a Search/Track radar with orthogonal polarization enabled on the receiver side. Enter the Min and/or Max values. This constraint is available only if operating in Goal SNR analysis mode. |
| SrchTrkOrthPolSinglePulseJOverS | This is the single pulse jamming-to-signal ratio constraint for a Search/Track radar with orthogonal polarization enabled on the receiver side. For a CW radar, the single pulse SNR is the SNR resulting from an effective pulse width of 1 second. Enter the Min and/or Max values. |
| SrchTrkOrthPolSinglePulsePDet | This is the single pulse probability of detection for a Search/Track radar with orthogonal polarization enabled on the receiver side. Enter maximum and/or minimum values in the range 0-1. |
| SrchTrkOrthPolSinglePulsePDetJamming | This is the single pulse probability of detection that includes the effects of jamming for a Search/Track radar with orthogonal polarization enabled on the receiver side. Enter maximum and/or minimum values in the range 0-1. |
| SrchTrkOrthPolSinglePulseSNR | This is the single pulse signal-to-noise ratio for a Search/Track radar with orthogonal polarization enabled on the receiver side. For a CW radar, the single pulse SNR is the SNR resulting from an effective pulse width of 1 second. Enter the Min and/or Max values. |
| SrchTrkOrthPolSinglePulseSNRJamming | This is the single pulse signal-to-noise ratio that includes the effects of jamming for a Search/Track radar with orthogonal polarization enabled on the receiver side. For a CW radar, the single pulse SNR is the SNR resulting from an effective pulse width of 1 second. Enter the Min and/or Max values. |
| SrchTrkSinglePulseJOverS | This is the single pulse jamming-to-signal ratio constraint for a Search/Track radar. For a CW radar, the single pulse SNR is the SNR resulting from an effective pulse width of 1 second. Enter the Min and/or Max values. |
| SrchTrkSinglePulsePDet | This is the single pulse probability of detection for a Search/Track radar. Enter maximum and/or minimum values in the range 0-1. |
| SrchTrkSinglePulsePDetJamming | This is the single pulse probability of detection that includes the effects of jamming for a Search/Track radar. Enter maximum and/or minimum values in the range 0-1. |
| SrchTrkSinglePulseSNR | This is the single pulse signal-to-noise ratio for a Search/Track radar. For a CW radar, the single pulse SNR is the SNR resulting from an effective pulse width of 1 second. Enter the Min and/or Max values. |
| SrchTrkSinglePulseSNRJamming | This is the single pulse signal-to-noise ratio that includes the effects of jamming for a Search/Track radar. For a CW radar, the single pulse SNR is the SNR resulting from an effective pulse width of 1 second. Enter the Min and/or Max values |
| SunElevationAngle | Min and Max values represent the elevation angle to the apparent position of the Sun. |
| SunSpecularExclusion | Access periods are restricted to times when the specular reflection point is at least the user specified angle from the line of sight between the constrained object and the secondary object. The location of the solar specular reflection point on the surface of the central body is computed based on the position of the constrained object. The specular reflection point does not exist for instances where the constrained object is in umbra. The specular reflection point exists when the constrained object is sunlit, regardless of whether its location is on land, sea, etc. |
| TerrainGrazingAngle | This is the minimum and/or maximum angle between the relative position vector and the local terrain. This constraint is dependent upon the terrain normal direction specified in the object's Basic properties. If the slope of the terrain is zero, this constraint is equivalent to the Elevation Angle constraint. |
| TotalRcvdRfPower | This is the total RF power received at the receiver antenna terminal, not accounting for antenna gains. This includes the power due to the main carrier and the powers due to the interferers/jammers in the receiver's line of sight. |
| TropScintillLoss | See Tropospheric Scintillation. |
| UrbanTerresLoss | See Urban Propagation Wireless InSite Model. |