Facilities

A facility is represented in the Browser and in the ODTK toolbar by the icon. For each facility in a tracking system, the following properties can be accessed and, if desired, changed using the Object Properties window:

Facility Properties
Property Description
Position

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
PositionType

Select MeanTide or TideFree option.

ModelStationMotion

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

Estimate

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
Estimation of facility location is supported for range, Doppler, azimuth and elevation measurements.
UsePositionFromMeasurementFile

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.

LocationErrors

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.

MeasurementStatistics

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

MeasurementProcessing

Same as the MeasurementProcessing attributes for a satellite.

MinElevation

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.

MaxElevation

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.

AzElMask

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.
ReferenceEmitter

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.

OpticalProperties

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

RangingMethod

Select Transponder, Retroreflector, or Skin Track.

AntennaType

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

BoresightAzimuth, BoresightElevation

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.

Az (deg) El (deg) Local-X Local-Y Local-Z
0 90 North West Zenith
90 90 East North Zenith
180 90 South East Zenith
270 90 West South Zenith
MaxAngleDown

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.

AntennaCorrectionType

Select from the available list of DSN antenna correction models.

AntennaMountType

Select from the available list of antenna mount types.

DirectionCosineAzimuthOffset

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

TroposphereModel

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.
TroposphereModel.EstimateBias

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.

TroposphereModel.BiasSigma

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

TroposphereModel.BiasHalfLife

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.

TroposphereModel.Data

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.

IonosphereModel

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.

IRI2007 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.

MeasTimeBias

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.
MeasTimeBias.Estimate

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

MeasTimeBias.TimeBiasModel

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

MetDataSource

MetDataSource is the source of meteorological data to support computations with the Marini-Murray or Saastamoinen model as either Constant values or File based time dependent values.

Settings for Constant meteorological data are:

Settings for File based meteorological data are:

Antenna Type

Two types of radar antennas are provided. The data does not affect the orbit determination process, but it can be used to define visibility constraints for measurement simulation.

Antenna Types
Type Description
Mechanical Refers to a classical radar dish antenna, which typically has a minimum elevation visibility constraint.
Phased Array Refers to a radar array with fixed orientation in topocentric coordinates, with visibility constraints defined by the fixed orientation of the face. If a radar site is designated as Phased Array, you are prompted to specify the Boresight Azimuth and Boresight Elevation. Visibility constraints can then be constructed as a minimum azimuth and elevation angle with respect to the boresight.
Optical Refers to one of a family of ground based, visible spectrum tracking devices, which may include GEODSS, AMOS, MOTIF and Baker-Nunn Cameras, all designed to track when the facility is in the Earth's shadow and the target is illuminated.

Antenna Correction Type

The corrections produced by these models are only applied to DSN observations. Depending on the type chosen, range computations to the antenna reference location will be corrected for the effective location of the antenna as reflected in a measured range to the target. Some antenna types do not produce a correction. See the following table for details of the various antenna correction types.

Antenna Correction Types
Identifier Diameter m Angle Pair Axis-Offset b m Secondary Angle
26-H-D
34-H-D
26 or 34 HA-DEC 6.706 δ
26-A-E 26 AZ-EL 0.9144 γ
26-X-Y 26 Χ´ - Υ´ 6.706 Υ´
9-X-Y 9 Χ - Υ 2.438 Υ
34-HSB 34 AZ-EL 1.8288 γ
34-HEF 34 AZ-EL 0 γ
34-BWG 34 AZ-EL 0 γ
64-A-E
70-A-E
64 or 70 AZ-EL 0 γ
11VLBI 11 AZ-EL 0 γ

For 26-m or 34-m hour angle-declination (HA-DEC) antennas, the antenna type is specified as 26-H-D or 34-H-D and the antenna correction in meters is calculated as:

ΔAρ = -b cos δ m

where δ is the declination angle of the spacecraft or quasar. The axis-offset b is 6.706 m.

For the 26-m azimuth-elevation (AZ-EL) antenna, the antenna type is specified as 26-A-E and the antenna correction is calculated from:

ΔAρ = -b cos γ m

where γ is the elevation angle of the spacecraft or quasar. The axis-offset b is 0.9144 m.

For 26-m X-Y mount antennas, the antenna type is specified as 26-X-Y and the antenna correction is calculated from:

ΔAρ = -b cos Υ´ m

where the secondary angle of the antenna is the auxiliary angle Υ´. Note that the 26-m X-Y mount antennas actually measure the angles Χ´ and Υ´ which are X and Y angles in the North-South sense. The axis-offset b is 6.706 m.

For 9-m X-Y mount antennas, the antenna type is specified as 9-X-Y, and the antenna correction is calculated from:

ΔAρ = -b cos Υ m

where the secondary angle of the antenna is the auxiliary angle Υ. The 9-m X-Y mount antennas measure the angles Χ and Υ which are X and Y angles in the East-West sense. The axis offset b is 2.438 m.

For 34-m AZ-EL mount high-speed beam wave guide antennas, the antenna type is specified as 34-HSB, the axis-offset b is 6 feet or 1.8288 m, and the antenna correction can be calculated from Eq.

For 34-m AZ-EL mount high efficiency antennas, the azimuth and elevation axes intersect and the antenna correction is zero. This antenna type is specified as 34-HEF.

For 34-m AZ-EL mount beam wave guide antennas, the axes intersect and the antenna correction is zero. This antenna type is specified as 34-BWG.

For 64-m or 70-m AZ-EL mount antennas, the axes intersect and the antenna correction is zero. These antennas can be specified as 64-A-E or 70-A-E.

For 11-m AZ-EL mount orbiting VLBI antennas, the azimuth and elevation axes intersect and the antenna correction is zero. These antennas are specified as 11VLBI. The upper part of the azimuth axis of the antenna is mounted on a wedge which tips the azimuth axis away from the vertical by 7°. The lower surface of the wedge is horizontal, and the upper surface is tipped 7° from the horizontal. The wedge can be rotated about a vertical axis. Let

σ = azimuth angle in degrees east of north of the high point of the wedge.

The azimuth axis is tipped away from the vertical by 7° in the direction σ + 180° east of north. The azimuth of the wedge σ (the so-called train angle) is held fixed during a pass of the spacecraft over the antenna. The station location is the intersection of the tipped azimuth axis and the elevation axis. It is located on the circumference of a horizontal circle of radius r. The current estimate of this radius is:

r - 39.838 cm - 0.39838 x 10-3 km

The solve-for station location is the center of the horizontal circle. The Earth-fixed vector from the solve-for station location to the actual station location is given by:

Δrb = -r cos σ N -r sin σ E km

where the components of the vectors are referred to the Earth-fixed coordinate system aligned with the true pole, prime meridian, and equator of date. The north and east vectors are calculated from Eqs. For 11-m AZ-EL mount orbiting VLBI antennas, the station location offset vector Δrb given by Eq. is added to the Earth-fixed position vector rb of the tracking station given by Eq.

REFERENCE: Moyer, Theodore D., "Formulation for Observed and Computed Values of Deep Space Network Data Types for Navigation", Monograph 2, Deep Space Communications and Navigation Series.

Antenna Mount Type

The antenna mount type is used in the simulation and processing of X/Y angle measurements to provide a definition for the X/Y angles. An antenna mount type specified through the tracking data provider will override the setting on the facility. In particular, the UTDF and GEOS-C tracking data formats specify which mount type the measurements are for.

Antenna Mount Type
Type Description
AzEl Antenna uses an azimuth-elevation mount. The natural angles which are measured from this mount are azimuth and elevation where azimuth is the angle from local north measured (positive in the easterly direction) to the projection of the relative position vector in the local horizontal plane. Elevation is the angle between the relative position vector and the local horizontal plane (positive towards the zenith direction). If X/Y measurements are simulated or processed, they will be interpreted using the XY_EW definition.
DirCos_EW Antenna uses an East-West direction cosine mount. The East direction cosine is measured as the projection of the relative position unit vector onto the local antenna East direction. The North direction cosine is measured as the projection of the relative position unit vector onto the local antenna North direction. The local antenna reference frame directions differ from the standard topocentric East and North direction by a rotation about the zenith direction given by the DirectionCosineAzimuthOffset which specifies the azimuth of the antenna local North direction.
XY_EW Antenna uses an X-Y mount where the X axis lies along the west-east line. The X angle is measured as the angle between the zenith direction and the projection of the relative position vector into a reference plane containing the zenith direction and oriented north-south. The X angle is defined to be positive when the satellite is south of the station. The Y angle is measured as the angle between the reference plane and the relative position vector (positive towards the east).
XY_NS Antenna uses an X-Y mount where the X axis lies along the south-north line. The X angle is measured as the angle between the zenith direction and the projection of the relative position vector into a reference plane containing the zenith direction and oriented east-west. The X angle is defined to be positive when the satellite is east of the station. The Y angle is measured as the angle between the reference plane and the relative position vector (positive towards the north).
XY_Z Antenna uses an X-Y mount where the X axis direction is defined by the Z angle which is supplied in the tracking data. The X axis direction is found by rotating the north direction about the zenith in a right handed sense by the Z angle. A mount type of XY_EW would be equivalent to a Z angle of 270 degrees and a mount type of XY_NS would be equivalent to a Z angle of zero. The X angle is measured as the angle between the zenith direction and the projection of the relative position vector into a reference plane containing the zenith direction and perpendicular to the X axis. The X angle is defined to be positive when the rotation about the X axis is in the right handed direction. The Y angle is measured as the angle between the reference plane and the relative position vector. The Y angle is defined to be positive when the rotation about the Y axis is in the right handed direction.

AzElMask Utilization and Geometric Data Reporting by ODTK

Various facilities can use a local horizon mask and various facilities can report geometric range, azimuth, elevation, and range rate. The two sets are not the same. For all multi-legged tracking the reported geometric data is only for the last leg, the leg to the reporting facility, at the time of signal reception. For example, for 4-legged TDRS data from WSGT --> TDRS --> BRTS transponder --> TDRS --> WSGT, only the geometric data for the return link to WSGT is reported. For TDOA and FDOA measurements only geometric data from the emitter to the second relay satellite (last relay satellite in the tracking strand) is reported.

Space based measurements will report grazing altitude, the height of the ray-path at the closest approach to the earth. This data is also available for GPS receivers mounted on a spacecraft.

AzElMask Utilization and Geometric Data Reporting by ODTK
Facility Uses AzElMask Report Geometry Notes
Ground based range, azimuth, elevation, and Doppler Yes Yes Geometric range, azimuth, elevation and range rate are reported between receiving facility and satellite, at the time the signal is received.
Ground based right ascension & declination Yes Yes Geometric range, azimuth, elevation and range rate are reported between receiving facility and satellite, at the time the signal is received.
BRTS 4L Range & 5L Doppler Yes No Masking constraints are checked for BRTS-to-TDRS signal path.
Emitter Yes No Mask constraints are checked to both primary satellite and secondary satellite.
1W Bistatic Range Yes Yes Masking constraints are checked for both transmitter and receiver. Geometric range, azimuth, elevation and range rate are reported between receiving facility and receiving facility.
TDRS 4L Range & 5L Doppler & 3L (return-link) Doppler Yes Yes Geometric range, azimuth, elevation and range rate are reported between receiving facility and TDRS; grazing altitude is reported between TDRS and user satellite.
GPS receiver on a facility Yes Yes Mask is assigned to the parent facility.
  • 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
TDOA & FDOA receiver Yes Yes AzElMask is evaluated for the receiver facility to each satellite. Geometric range, azimuth, and elevation are reported between the emitter and the second relay satellite in the strand list.
GPS receiver on spacecraft No Yes AzElMask is not used, but boresight and boresight elevation (in the antenna object) and grazing altitude provide masking conditions. Reports geometric range, elevation, and grazing altitude.
Space based range, azimuth, elevation, right ascension, and declination No Yes AzElMask is not used, but grazing altitude provides a masking condition. Reports geometric range, elevation, and grazing altitude.

ODTK 6.5