TrackingFileSet
TrackingFileSet — Manages the observation data contained in one or more external tracking data files.
Description
A TrackingFileSet is required for both simulator and estimator runs. For a data simulation run, the user must specify the desired tracking strings for the simulated data (via AddTrackingConfig) and provide an output file name for the simulated tracking observations (via FileName). In simulation mode, the user may specify a range modulo constant, Doppler count interval, and other parameters, depending on the type of tracking data being simulated. See the remarks below for more details.
When running the estimator, the FileName parameter specifies the path to a pregenerated external tracking data file. It is not necessary to explicitly specify tracking configurations when running the estimator; GMAT will examine the specified external tracking data file and determine the tracking configurations automatically. GMAT will throw an error message if it is unable to uniquely identify all objects found in the tracking data file.
When running the estimator, one or more AcceptFilters and/or RejectFilters may be employed to select from all available observations a smaller subset for use in the estimation process.
The SimRangeModuloConstant and SimDopplerCountInterval fields apply only to the simulator and are ignored by the estimator. When running the estimator, these values are provided in the tracking data file. For both the simulator and estimator, relativity, light time, and ET-TAI corrections may optionally be applied.
See Also: Simulator, BatchEstimatorInv, AcceptFilter, RejectFilter, Tracking Data Types for OD
Fields
| Field | Description | ||||||||||||
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| AddTrackingConfig |
One or more signal paths and measurement types for simulation or estimation. See the Remarks section below for details on the Tracking Strand specification.
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| DataFilters |
Defines filters to be applied to the data. One or more filters of either type (AcceptFilter, RejectFilter) may be specified. Rules specified by data filters on a TrackingFileSet are applied to determine what data is admitted or rejected as input to the estimation process.
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| FileName |
For simulation, specifies an output file for the simulated measurement data. For estimation, specifies one or more preexisting tracking data input files in GMD-format.
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| RampTable |
Specifies a transmit frequency ramp table to be used when computing measurements for both simulation and estimation.
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| SimDopplerCountInterval | Specifies the Doppler count interval used for Doppler and range-rate measurements. This value is only used in simulation mode.
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| SimRangeModuloConstant | Specifies the value of the DSN range ambiguity interval. This value is only used in simulation mode.
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| UseETminusTAI |
Flag specifying if General Relativistic time corrections should be made to the measurements. If this flag is set, GMAT will apply the adjustment from TAI to Ephemeris Time when solving the light time equations for the computed measurement. See Remarks below for more details.
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| UseLightTime |
Flag specifying whether light time corrections should be applied to computed measurements.
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| UseRelativityCorrection |
Flag specifying if General Relativistic corrections should be made to the computed measurements. If this flag is set, GMAT will adjust the computed light time to include the effects due to the coordinate velocity of light and bending of the signal path. See Remarks below for more details.
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Remarks
See Tracking Data Types for OD for a detailed listing of all tracking data types and tracking data file formats supported by GMAT for orbit determination.
Setting UseETminusTAI to True corresponds to inclusion in the computed round-trip light time of the ET-TAI uplink and downlink terms in Eq. 11-7 of Moyer, Formulation of Observed and Computed Values of Deep Space Network Data Types for Navigation, JPL Publication 00-7, October 2000. Setting UseRelativityCorrection to True corresponds to inclusion of the RLT uplink and downlink terms in Eq. 11-7 of Moyer.
The SimRangeModuloConstant field is used only in the simulation of DSN range tracking data. The user may specify a value to be used for this field or may omit it, in which case the default value is used. This field is not applicable to estimation. In estimation, this value is provided in the input tracking data file.
The SimDopplerCountInterval is used in the simulation of DSN_TCP and RangeRate tracking data. The user may specify a value to be used for this field or may omit it, in which case default value of 1 second is used. This field is not applicable to estimation. In estimation, this value is provided in the input tracking data file.
When displaying or saving a TrackingFileSet object using the Write command, GMAT will display a number of items relevant to simulating TDRS data formats. These options are not implemented in the current release and should be ignored or manually removed from the output file.
Tracking Strand Specification
When simulating tracking data, at least one tracking strand must be specified using the AddTrackingConfig parameter. The tracking strand must be enclosed within curly braces. The format of the tracking strand depends on the measurement data type being generated. Use the following table as a guide.
| Measurement Type Name | Tracking Strand Specification Format |
|---|---|
| DSN_SeqRange, DSN_TCP, Range, RangeRate | {XMIT_GroundStation, Spacecraft, RECV_GroundStation} |
| GPS_PosVec | {Spacecraft.Receiver} |
Examples
This example illustrates use of the TrackingFileSet object for simulation of DSN tracking data. Specification of the tracking configurations (AddTrackingConfig) is optional when running the estimator. If omitted, GMAT will attempt to automatically detect the tracking configurations present in the tracking data file.
In this example, the frequency ramp table file
dsn.ramp must be a preexisting ramp table. GMAT will
not simulate ramp table records. Alternatively, the user may omit
specification of a ramp table when simulating data. If the ramp table is
omitted, the simulator will use the frequency specified on the
Transmitter object attached to each
GroundStation.
Create TrackingFileSet dsnObs;
%Create objects referenced by dnsObs
Create GroundStation GDS CAN MAD;
Create Spacecraft EstSat;
Create AcceptFilter af;
dsnObs.AddTrackingConfig = {{GDS, EstSat, GDS}, 'DSN_TCP'};
dsnObs.AddTrackingConfig = {{CAN, EstSat, CAN}, 'DSN_TCP'};
dsnObs.AddTrackingConfig = {{MAD, EstSat, MAD}, 'DSN_TCP', 'DSN_SeqRange'};
dsnObs.FileName = {'dsn.gmd'};
dsnObs.RampTable = {'dsn.ramp'};
dsnObs.UseLightTime = True;
dsnObs.UseRelativityCorrection = False;
dsnObs.UseETminusTAI = False;
dsnObs.SimRangeModuloConstant = 67108864;
dsnObs.SimDopplerCountInterval = 10.;
dsnObs.DataFilters = {af};
BeginMissionSequence;
This example illustrates use of the
TrackingFileSet object for simulation of GPS_PosVec
tracking data. This example assumes that GpsReceiver
is a previously created instance of Receiver and
has been attached to SimSat using the
AddHardware method.
Create TrackingFileSet PosVecObs;
PosVecObs.FileName = {'posvec_obs.gmd'};
PosVecObs.AddTrackingConfig = {{SimSat.GpsReceiver}, 'GPS_PosVec'};
SimMeas.DataFilters = {};
BeginMissionSequence;