Facilities

Select among:

• Geodetic - specify Lat, Lon, Alt
• Geocentric - specify Lat, Lon, Alt
• Cartesian - specify X, Y, Z
• Cylindrical - specify Radius, Theta, Z
• Spherical - specify Lat, Lon, Rad

Select MeanTide or TideFree option.

Set to true to expose a complete station motion model based on IERS Technical Note 32 (IERS Conventions 2003).

This attribute is used to indicate whether or not the location of the facility should be estimated by the Filter/Smoother or a random deviate generated by the simulator. Options are:

• Lat Lon Alt - Estimate all 3 positional components.
• Lat Lon - Estimate latitude and longitude only, leaving the altitude fixed at the user input value
• Nothing - Do not estimate the location of the facility

Set to true to allow position information from a tracking data reader to modify the position of the facility during measurement modeling for ground based two way range, two way Doppler, azimuth, elevation, right ascension and declination observations. This capability is useful for processing of observations taken from ship based trackers. This setting only affects observation modeling during estimation, it has no effect on simulations. If set to true, it is important that all tracking data readers used in your scenario must either provide position data or do not provide position information for the facility to avoid inconsistent results.

If you choose to estimate the location of the facility (see above), then you must also enter apriori position uncertainty information in terms of components in the topocentric frame (South, East, Up). If you choose to estimate only the latitude and longitude of the facility, then the simulator will randomly deviate only those two quantities.

Various statistical properties can be set for the facility's measurement elements.

Same as the MeasurementProcessing attributes for a satellite.

Enter a minimum elevation constraint for the facility. This constraint is used by the simulator and filter - no measurements are processed (by the filter) or generated (by the simulator) at a given time if the observed or calculated elevation angle between the facility and the satellite is less than the constraint value.

Enter a maximum elevation constraint for the facility. This constraint is used by the simulator and filter - no measurements are processed (by the filter) or generated (by the simulator) at a given time if the observed or calculated elevation angle between the facility and the satellite is greater than the constraint value.

Allows specification of an azimuth-dependent obscura profile by using the data in an external azimuth-elevation mask file (*.aem). Azimuth-elevation mask files must be formatted to work with STK/ODTK and end in a .aem extension. This profile models the effects of buildings and hills around a facility location.

• Enabled - Turn on/off use of the mask file in line-of-sight calculations.
• Filename - Specify the file containing the azimuth-elevation mask to be used.

Specifies the one base emitter to which SD TDOA and/or SD FDOA measurements will be referenced in the case where the SD measurements are constructed from undifferenced measurements during the estimation process. The single differenced measurements will be constructed in the sense of (other emitter - reference emitter). The reference emitter is not used in the case that the single differenced measurements are loaded directly.

Enter the optical polar exclusion angle in the selected angle unit and set related options.

Select Transponder, Retroreflector, or Skin Track.

Select Mechanical or Phased Array. For the latter, specify values for Boresight Azimuth and Elevation.

These properties currently only apply to Facilities of AntennaType = PhasedArray and are hidden when the AntennaType is not PhasedArray.

These inputs are a pair of angels that orient the radar "face" local coordinate system. In the local system the z-axis is in the direction of the radar face normal direction, and the xy plane is the plane of the "face". The orientation is consistent with the STK Azimuth-Elevation Orientation Method, About Boresight Rotate option.

Consider a system where the +X-axis is in the North direction, the +Y-axis is in the West direction, and +Z-axis is in the Zenith direction. Then BoresightAzimuth is a horizontal angle measured in the XY plane of this system clockwise (eastward) from the North. BoresightElevation is a vertical angle measured from the local XY plane, positive towards Zenith. The transformation from this system to the radar "face" local system then consists of a rotation about this system's +Z axis by the BoresightAzimuth angle followed by a rotation about the new +Y axis by (90 deg - BoresightElevation). The following table gives the orientation of the radar "face" local frame for different BoresightAzimuth's, with BoresightElevation = 90 deg.

This property currently only applies to Facilities of AntennaType = PhasedArray and is hidden when the AntennaType is not PhasedArray.

Supplements MinElevation, MaxElevation, and AzElMask as a processing constraint for phased array radars. No phased array measurements will be processed (by the filter) or generated (by the simulator) if the observed or calculated angle down from radar face normal is greater than this angle.

This property currently only applies to Facilities of AntennaType = PhasedArray and is hidden when the AntennaType is not PhasedArray.

Select from the available list of DSN antenna correction models.

Select from the available list of antenna mount types.

Specifies the azimuth of the local antenna North direction which is used in the definition of the East and North direction cosine measurements.

Set the Enabled property to Yes, No or Based on Tracking System. The Model property (read only if you select Based on Tracking System) identifies the model.

DSNMedia Model: Models troposphere zenith delays using the JPL DSN media correction data files and as described in 820-013 Deep Space Network External Interface Specification JPL D-16765 TRK-2-23 Media Calibration Interface. Delays are computed based on power or trigonometric series representations of dry and wet delay corrections. Series representations are input via files as specified in the Scenario.EarthDefinition.DSNMediaCalibration file list. Computed dry delays due to the troposphere represent corrections to a baseline seasonal correction model from C.C. Chao. This baseline model is described in JPL Publication 94-24, “A Comparative Survey of Current and Proposed Tropospheric Refraction-Delay Models for DSN Radio Metric Data Calibration”, 1994 by Estefan and Sovers. Computed values of wet delays represent the total wet delay in the zenith direction. Zenith delays are mapped to the current elevation of the satellite using the Niell (NMF) mapping functions.

Note: If a facility is configured to use DSN Media Calibration Data for troposphere modeling and a requested time (during a tracking interval) is not covered by the data specified in the scenario properties, ODTK will stop processing.

SCF Model: The SCF model takes as input the surface refractivity at each facility location. Actual surface refractivity varies with local temperature, pressure and humidity. The surface refractivity can be modeled either as a constant value (select Constant as the SurfaceRefractivity option), or interpolated from a set of monthly averages (select Monthly Averages), or as a 10th-order polynomial function fit over the span of one year (select Polynomials).

Marini-Murray Model: The Marini-Murray model is the standard model for determining the effect of the troposphere on laser ranging data. If this model is selected, set the following:

• OverrideWavelength – If set to true, the Wavelength value will override any value specified in the tracking data.
• Wavelength - The laser operating wavelength. This value is always used when simulating laser ranging data and is also used when estimating if the OverrideWavelength flag is set to true or if wavelength information is not available in the tracking data.
• MetDataSource - A source for meteorological data as described below.

Saastamoinen Model: The Saastamoinen model is a standard model often used for determining the effect of the troposphere on GPS data. If this model is selected, set the following:

• MetDataSource - A source for meteorological data as described below.

Select true to estimate a correction to the a priori model value of the troposphere delay at zenith. The corrected delay is considered to be due to the wet component of the troposphere and is mapped to the current elevation angle using the wet mapping function associated with the a priori model. For the SCF model, the same mapping function is used for the wet and hydrostatic parts of the delay. For the Saastemoinen model, the Neill NMF wet mapping function is used.

Square root of the variance of a Gauss Markov bias associated with the estimate of the tropospheric correction.

The half life of the Gauss Markov bias. In the absence of measurements for a period equal to the half life, the Gauss Markov bias will decay by a factor of two during estimation. The half life also controls how quickly the value of the bias can be changed during simulation.

Constant allows you to model surface refractivity as a single value at any time; enter this value as ConstantValue.

Monthly Averages: The surface refractivity will be interpolated from a set of monthly averages.

• DayOfMonth: Indicates that the input monthly average is centered on this day of each month. For the first of the month, enter 1, for the middle of the month enter 15, and for the end of the month, enter 31. In this last case, the date for February will be adjusted to the 28th or 29th, and for the months of April, June, September and November will be adjusted to the 30th. The time of day in all cases is 0 hours UTC.
• Jan-Dec: The average surface refractivity value for the month.

Polynominals allows you to model surface refractivity as a 10th-order polynominal function fit over a one-year span. Enter these polynomials under Polynominal1 - Polynominal11.

Set the Enabled property to Yes, No or Based on Tracking System. If the Enabled property is set to Yes, select a model and enter desired values for transmitter and receiver frequency. Otherwise, the values for these properties is inherited from those set at the Tracking System level.

DSNMedia Model. Models ionosphere delays along the spacecraft line of sight using the JPL DSN media correction data files and as described in 820-013 Deep Space Network External Interface Specification JPL D-16765 TRK-2-23 Media Calibration Interface. Delays are computed based on power or trigonometric series representations of ionospheric delay corrections in the direction of the satellite. Series representations are input via files as specified in the Scenario.EarthDefinition.DSNMediaCalibration file list. A separate series representation is used for each tracking pass. The computed value represents the one way delay in meters at the nominal S-band frequency of 2295 Mhz.

Note: If a facility is configured to use DSN Media Calibration Data for ionosphere modeling and a requested time (during a tracking interval) is not covered by the data specified in the scenario properties, ODTK will stop processing.

IRI2016 Model. An empirical standard model of the ionosphere, based on all available data sources.The IRI models are self-contained; however they require that the IRI Model Data be current. The ODTK LaunchPad provides a utility to Update Data Files, including the IRI model data files.

These inputs allow the user to:

1. Apply a measurement time tag bias to the measurements for which this facility is the tracker
2. Optionally simulate and estimate that time tag bias. The same time tag bias will apply to all measurements from this one facility tracker with these caveats:
   • If a time tag bias is applied it will apply to all measurement types.
   • The are certain measurements where the facility time bias will not be estimated. These include the Ground FDOA Dot, DSN Doppler/TCP, DSN 3W Doppler, TDRSS BRTS Range and Doppler, TDOA 2 Emitters, TDOA Dot 2 Emitters, 3L Doppler, SD TDOA/FDOA.
   • Estimation applies to filter, smoother, and VLS. Currently, cannot estimate this bias with Least Squares.

If set to true the time tag bias will be estimated using the stochastic model defined by the "TimeBiasModel" parameter.

The stochastic sequence to model and estimate the time bias. Note that a non-zero "Constant" value will be applied even if the Estimate flag is false.

Choices for the TimeBiasModel include:

• GaussMarkov = Bias will be modeled as a scalar exponential Gauss Markov sequence
• RandomWalk = Bias will be modeled using a Wiener (Brownian motion) sequence
• Vasicek = Bias will be modeled using a Vasicek stochastic sequence. This is a two-parameter model that solves for both a short-term and long-term bias.

Reference the Stochastic Models section for the description and inputs associated with each model

• Pseudorange and Phase = downlink geometry
• Single differenced measurements report geometry of second GPS satellite
• Double differenced measurements report geometry of second satellite at second receiver