Description of keywords of VTD (VLBI Time Delay) control file language

L. Petrov

Abstract:

Table of contents:

1   General rules

2   Description of keyword

2.1   LEAP_SECOND:
2.2   DE403_EPHEMERIDES:
2.3   STATION_DESCRIPTION:
2.4   STATION_COORDINATES:
2.5   STATION_VELOCITIES:
2.6   STATION_ECCENTRICITIES:
2.7   SOURCE_COORDINATES:
2.8   SOURCE_COORDINATES_2ND:
2.9   SOURCE_COORDINATES_3RD:
2.10   SOURCE_COORDINATES_4TH:
2.11   AEM_FILE
2.12   ERM_FILE
2.13   HARMONIC_EOP_FILE:
2.14   EOP_SERIES:
2.15   EOP_TIME_SCALE:
2.16   UZT_MODEL:
2.17   UZT_USE:
2.18   EROT_COMPAT:
2.19   PRECESSION_EXPRESSION:
2.20   NUTATION_EXPANSION:
2.21   GEODESIC_NUTATION:
2.22   SOLID_EARTH_TIDES_ZERO_FREQ:
2.23   SOLID_EARTH_TIDES_2ND_DEGREE:
2.24   SOLID_EARTH_TIDES_3RD_DEGREE:
2.25   POLE_TIDE_MODEL:
2.26   MPL_FILE:
2.27   POSVAR_FIL:
2.28   POSVAR_MOD:
2.29   POSVAR_INT:
2.30   POSVAR_USE:
2.31   AXIS_OFFSET_MODEL:
2.32   ANTENNA_DEFORMATIONS_FILE:
2.33   ANTENNA_THERMAL_EXPANSION
2.34   METEO_DEF
2.35   HYDROSTATIC_ZENITH_DELAY:
2.36   WET_ZENITH_DELAY:
2.37   HYDROSTATIC_MAPPING_FUNCTION:
2.38   WET_MAPPING_FUNCTION:
2.39   ATMOSPHERE_TILT_PARTIALS:
2.40   SLANT_PATH_DELAY
2.41   ATMOSPHERE_PATH_DELAY_PARTIAL
2.42   EXTERNAL_DELAY_DIR
2.43   EXTERNAL_DELAY_DIR_2ND
2.44   EXTERNAL_DELAY_DIR_3RD
2.45   EXTERNAL_DELAY_DIR_4TH
2.46   IONOSPHERE_MODEL:
2.47   IONOSPHERE_DATA_DIR:
2.48   IONOSPHERE_DATA_DIR_2ND:
2.49   IONOSPHERE_DATA_DIR_3RD:
2.50   IONOSPHERE_DATA_DIR_4TH:
2.51   GRS_METRIC:
2.52   TROP_AXOF_COUPLING:
2.53   TROP_GEOMETRIC_COUPLING:
2.54   PARALLACTIC_ANGLE:
2.55   GALACTIC_ABERRATION:
2.56   GEOM_EXPR_FAR_ZONE:
2.57   GEOM_EXPR_NEAR_ZONE:
2.58   SOURCE_STRUCTURE:
2.59   DOPPLER_EXPR:
2.60   DELAY_RATE:

1   General rules

Control file for VTD consists of lines of variable length. Lines which starts from characters # or * are considered as comments and ignored by parsing software. Each line consists of a keyword and the value. All keywords must be specified, no defaults are allowed. A value should be separated the keyword by one or more delimiters. Valid delimiters: blank (decimal code 32), tabulation (decimal code 9) and binary zero. The first line of the control file should have the label of the format version. The current label version is # VTD Control file. Format version of 2009.02.21 If the file does not have correct format label, VTD library will issue and errors message.

2   Description of keyword

2.1   LEAP_SECOND:

LEAP_SECOND: leap_second_file_name leap_second_file_name is the name of the file in LEAP_SECOND format which tabulates epochs of discontinuities of the function UT1 - TAU(t) and values of discontinuities.

2.2   DE403_EPHEMERIDES:

DE403_EPHEMERIDES: planetary_ephemerides_file_name Planetary_ephemerides_file_name is the name of the DE403 ephemerides file.

2.3   STATION_DESCRIPTION:

STATION_DESCRIPTION: station_description_file_name Station_description_file_name is the name of the file in STADESC format. That file contains information about all stations which participated in the experiment: IVS station name, antenna mounting type, antenna axis offset, tectonic plate. This file may contain information about other stations which did not participated in the analyzed experiment. All stations which participated in the experiment must be listed in this file.

2.4   STATION_COORDINATES:

STATION_COORDINATES: station_coordinates_file_name Station_coordinates_file_name is the name of the file either in GETPAR_STA format ( http://gemini.gsfc.nasa.gov/solve_root/help/getpar_02.html#section3.1 ) or in SIT-MODFILE format. That file contains information about all stations which participated in the experiment: IVS station name, station coordinates and epoch for coordinates of those stations which had episodic motion. This file may contain information about other stations which did not participated in the analyzed experiment. All stations which participated in the experiment must be listed in this file.

2.5   STATION_VELOCITIES:

STATION_VELOCITIES: station_velocities_file_name Station_velocities_file_name is the name of the file either in GETPAR_VEL format ( http://gemini.gsfc.nasa.gov/solve_root/help/getpar_02.html#section3.2 ) or in VEL-MODFILE format. That file contains information about all stations which participated in the experiment: IVS station name, station velocities. This file may contain information about other stations which did not participated in the analyzed experiment. All stations which participated in the experiment must be listed in this file.

2.6   STATION_ECCENTRICITIES:

STATION_ECCENTRICITIES: station_eccentricities_file_name Station_eccentricities_file_name is the name of the file with eccentricity vector in ECC-FORMAT. It contains IVS station name, CDP monument number, starting date of validity of the eccentricity vector, end date of validity of the eccentricity vector, eccentricity vector for each station each period of validity defined as the vector from the monument point for which station coordinates are referred to, to the reference point on the antenna, defined as a point on the fixed axis which is located at the closest distance to the moving axis.

2.7   SOURCE_COORDINATES:

SOURCE_COORDINATES: source_coordinates_file_name The qualifier Source_coordinates_file_name is the name of the file either in GETPAR_SOU format ( http://gemini.gsfc.nasa.gov/solve_root/help/getpar_02.html#section3.3 ) or in SOU-MODFILE format. That file contains information the sources which participated in the experiment: IVS source name, source coordinates. This file may contain information about other source which were not observed in the analyzed experiment.

2.8   SOURCE_COORDINATES_2ND:

SOURCE_COORDINATES: [source_coordinates_file_name_2 or NONE] The qualifier source_coordinates_file_name is the name of the file either in GETPAR_SOU format ( http://astrogeo.org/solve_root/help/getpar_02.html#section3.3 ) or in SOU-MODFILE format. This is the secondary catalogue used by VTD. It might be convenient to keep coordinates of source in more than one file. That file contains information the sources which participated in the experiment: IVS source name, source coordinates. This file may contain information about other source which were not observed in the analyzed experiment.

2.9   SOURCE_COORDINATES_3RD:

SOURCE_COORDINATES: [source_coordinates_file_name_3 or NONE] The qualifier source_coordinates_file_name is the name of the file either in GETPAR_SOU format ( http://gemini.gsfc.nasa.gov/solve_root/help/getpar_02.html#section3.3 ) or in SOU-MODFILE format. This is the ternary catalogue used by VTD. It might be convenient to keep coordinates of source in more than one file. That file contains information the sources which participated in the experiment: IVS source name, source coordinates. This file may contain information about other source which were not observed in the analyzed experiment.

2.10   SOURCE_COORDINATES_4TH:

SOURCE_COORDINATES: [source_coordinates_file_name_4 or NONE] The qualifier source_coordinates_file_name is the name of the file either in GETPAR_SOU format ( http://gemini.gsfc.nasa.gov/solve_root/help/getpar_02.html#section3.3 ) or in SOU-MODFILE format. This is the fourth catalogue used by VTD. It might be convenient to keep coordinates of source in more than one file. That file contains information the sources which participated in the experiment: IVS source name, source coordinates. This file may contain information about other source which were not observed in the analyzed experiment.

2.11   AEM_FILE

AEM_FILE: aem_file_name or NONE Keyword AEM_FILE specifies the name of the file with the apriori Earth rotation model. This file is one of the three files that describes the Earth's rotation in accordance to the empirical Earth rotation model formalism. The file should conform specifications of the AEM files. The AEM file defines values of "large" parameters, i.e. those parameters which squares are not-negligible. These are parameters for precession, several terms in nutation and several terms in the Earth's axial rotation.

2.12   ERM_FILE

ERM_FILE: erm_file_name or NONE Keyword ERM_FILE specifies the name of the file with the apriori Earth rotation model. This file is one of the three files that describes the Earth's rotation in accordance to the empirical Earth rotation model formalism. The file should conform specifications of the ERM files. The ERM file defines coefficients that describe long periodic, "small" variations in Earth's rotation, i.e. those parameters variations which squares are negligible. The coefficients of B-spline allows to compute the instantaneous vector of perturbations to the Earth's rotation. These file describes the slowly varying component of the Earth rotation.

2.13   HARMONIC_EOP_FILE:

HARMONIC_EOP_FILE: [NONE or NERS or file_name] Keyword HARMONIC_EOP_FILE specifies the name of the file with the harmonic Earth Orientation model. This models describes perturbation in the Earth orientation with respect to the apriori model specified by the apriori EOP files, apriori nutation, precession and built-in expression for the UT1 angle. The model is in the form sum (a + b*t)*{sin/cos}( theta/2*t**2 + omega*t + phase) The purpose of this model is to correct apriori EOP model specified in EOP_SERIES, PRECESSION_EXPRESSION, NUTATION_EXPANSION, GEODESIC_NUTATION keywords. NERS -- to take the harmonic EOP variations from the Network Earth Rotation Service (NERS). file_name -- name of the file with the model in HEO format.

2.14   EOP_SERIES:

EOP_SERIES: [NONE or ners_configuration_file or earth_orientation_parameters_file] Earth_orientation_parameters_file is the name of the file of the Earth orientation parameters either in EOP-MOD or NERS EOP series format, or NERS configuation file. The file with the Earth Orientation Parameters contains values of X-coordinate of the pole coordinate, Y-coordinate of the pole coordinate, and UT1 angle at the equidistant grid of time epochs. NONE -- No external file with EOP series. (Supported when ERM formalism was chosen) ners_configuration_file -- name of the control file for NERS client earth_orientation_parameters_file -- name of the file with Earth orientation parameters VTD analyzes the first line of the file in order to determine whether it is the file with the Earth orientation parameters or the NERS configuration file.

2.15   EOP_TIME_SCALE:

EOP_TIME_SCALE: time_scale_of_eop_table Time_scale_of_eop_table defines the time scale used for time tags in the table of the input Earth orientation series specified in the value of the keyword EOP_SERIES. Supported values: TAI TDT TDB UTC UT1 NONE -- (Supported when ERM formalism was chosen)

2.16   UZT_MODEL:

UZT_MODEL: UT1_zonal_tides_model_name UT1_zonal_tides_model_name is the name of the model of UT1 variations induced by zonal tides. Supported values: NONE -- no model is used. DICKMAN1993 -- model of Dickman, 1993, all terms DICKMAN1993_PRINCPLE -- model of Dickman, 1993, only principle term and 14 terms which contributes to UT1 rate greater than 1.0D-14 rad/s DICKMAN1993_SHORT -- model of Dickman, 1993, only terms with periods shorter than 60 days

2.17   UZT_USE:

UZT_USE: [NONE or ADD or INTERPOLATE or SUBTRACT] The way how to apply the mode of UT1 variations induced by zonal tides. NONE -- not to apply contribution of UT1 variations induced by zonal tides; ADD -- add contribution to UT1 caused by zonal tides to apriori EOP; SUBTRACT -- subtract contribution to UT1 caused by zonal tides from apriori EOP; INTERPOLATE -- the model is used for subtracting contribution to UT1 due to zonal tides before computation of interpolating coefficients, and then contribution of UT1 are added to final apriori UT1 values after interpolation.

2.18   EROT_COMPAT:

EROT_COMPAT: [NONE or CALC10 or NO_SANG] If specified, adds corrections to the apriori Earth rotation angles to be compatible with Calc10. It can be used for testing in order to precisely emulate values computed by Calc. These corrections DO NOT improve VLBI path delay prediction. This option is intended for tests only. NONE (recommended) means that no emulation is performed.

2.19   PRECESSION_EXPRESSION:

PRECESSION_EXPRESSION: precession_model_name Keyword PRECESSION_EXPRESSION specifies the name of the precession model. Supported expansions: LIESE_1977 -- Values of precession parameters from Lieske 1976. SIMON_1994 -- Values of precession parameters from Simon 1976. IERS_1996 -- Values of precession parameters from IERS 1976. CAPITAINE_2003 -- Values of precession parameters from Capitaine 2003 NERS -- Precession is computed by the NERS NONE -- No precession (Supported when ERM formalism was chosen)

2.20   NUTATION_EXPANSION:

NUTATION_EXPANSION: nutation_expansion_name Keyword NUTATION_EXPANSION specifies the name of the nutation expansions. Supported expansions: WAHR1980 -- Wahr 1980 nutation expansion. Expansion for Doodson arguments referred to at that paper are used. IERS1996 -- Empirical nutation expansion computed by T. Herring and presented in the IERS 1996 Conventions. Expansion for Doodson arguments referred to at that paper are used. REN2000 -- Theoretical expansion of the rigid Earth model by J. Souchay MHB2000 -- MHB2000 expansion according coefficients presented in the program which T. Herring posted on the Web. MHB2000_TRANSF -- REN2000 expansion with the transfer function from Mathews at al, 2002 paper. MHB2000_ADDON -- REN2000 expansion with the transfer function from Mathews at al, 2002 paper and all add-on terms listed at that paper. MHB2000_PETA -- Simplified expansion to nutation with only three non-linear terms. NERS -- Nutation is computed by the NERS NONE -- No nutation (Supported when ERM formalism was chosen)

2.21   GEODESIC_NUTATION:

GEODESIC_NUTATION usage_flag Keyword NUTATION_EXPANSION specifies whether geodesic nutation should be modeled. usage_flag -- one of YES -- to model geodesic nutation NONE -- not to model geodesic nutation

2.22   SOLID_EARTH_TIDES_ZERO_FREQ:

SOLID_EARTH_TIDES_ZERO_FREQ: Love_model_name Keyword SOLID_EARTH_TIDES_ZERO_FREQ specifies the name of the model of Love numbers for the zeroth frequency. Unfortunately, several erroneous papers and thoughtless resolution of scientific societies created a great confusion about the issues of so-called "permanent tide". VTD allows a user to specify the model for computation of the zonal tides of the zero-th frequency. Love_model_name -- model code. One of MDG97AN -- Mathews, Dehant, Gipson 1997, anelastic variant. NONE -- consider Love numbers for the tides of the second degree as zero.

2.23   SOLID_EARTH_TIDES_2ND_DEGREE:

SOLID_EARTH_TIDES_2ND_DEGREE: Love_model_name Keyword SOLID_EARTH_TIDES_2ND_DEGREE specifies the name of the model of Love numbers of the second degree as a function of frequency. Love_model_name -- model code. One of MDG97EL -- Mathews, Dehant, Gipson 1997, elastic variant. MDG97AN -- Mathews, Dehant, Gipson 1997, anelastic variant. DDW99EH -- Dehant, Defraigne, Wahr 1999, elastic, hydrostatic variant. DDW99IN -- Dehant, Defraigne, Wahr 1999, inelastic, non-hydrostatic variant. LOVE -- Love, 1923 model MATHEWS_2000 -- Mathews, 2000 model MATHEWS_2001 -- Mathews, 2001 model NONE -- consider Love numbers for the tides of the second degree as zero.

2.24   SOLID_EARTH_TIDES_3RD_DEGREE:

SOLID_EARTH_TIDES_3RD_DEGREE: Love_model_name Keyword SOLID_EARTH_TIDES_2ND_DEGREE specifies the name of the model of Love numbers of the third degree. Love_model_name -- model code. One of MDG97EL -- Mathews, Dehant, Gipson 1997. NONE -- consider Love numbers for the tides of the second degree as zero.

2.25   POLE_TIDE_MODEL:

POLE_TIDE_MODEL: Love_model_name Keyword POLE_TIDE_MODEL specifies the name of the model of Love numbers used for computation of the pole tide. Love_model_name -- model code. One of MDG97EL -- Mathews, Dehant, Gipson 1997, elastic variant. MDG97AN -- Mathews, Dehant, Gipson 1997, anelastic variant. DDW99EH -- Dehant, Defraigne, Wahr 1999, elastic, hydrostatic variant. DDW99IN -- Dehant, Defraigne, Wahr 1999, inelastic, non-hydrostatic variant. LOVE -- Love, 1923 model MATHEWS_2000 -- Mathews, 2000 model MATHEWS_2001 -- Mathews, 2001 model NONE -- consider Love numbers for the pole tides as zero.

2.26   MPL_FILE:

MPL_FILE: file_name Keyword MPL_FILE specifies the name of the file with the model of secular motion of the Earth's pole. It specifies shift of the pole at the initial epoch and the rate of change. NB: This feature is included only for compatibility with IERS Conventions. Specifying non-zero pole shift and drift ***IS WRONG***. file_name -- name of the file with the model of secular motion of the Earth's pole.

2.27   POSVAR_FIL:

POSVAR_FIL: model_index model_file_name Keyword POSVAR_FIL specifies the name of the file with the model of position variations. model_index -- the index of the model. Should be 1 if only one model of position variations is in use. Of more than one model is in use, then the models are numbered consecutively from 1 to the last model. Maximum 8 models can be specified. model_file_name -- the name of the file with the model.

2.28   POSVAR_MOD:

POSVAR_MOD: model_index model_type Keyword POSVAR_MOD specifies the model type. Two types are supported: time series and harmonic site position variations model. model_index -- the index of the model. Should be 1 if only one model of position variations is in use. Of more than one model is in use, then the models are numbered consecutively from 1 to the last model. Maximum 8 models can be specified. model_type -- one of HARMONIC_MODE -- the file is in HARPOS format: http://gemini.gsfc.nasa.gov/solve_root/help/harpos_format.txt TIME_SERIES -- the file is in BINDISP format: http://gemini.gsfc.nasa.gov/solve_root/help/bindisp_format.txt B_SPLINE -- ...

2.29   POSVAR_INT:

POSVAR_INT: model_index interpolation_type Keyword POSVAR_MOD specifies the type of interpolation. The values of the position variations models are first read at several epoch around the time range of the experiment, then interpolation polynomials are computed. Position variations at the epoch of the observation are computed on the basis of this polynomial. Two interpolation types are supported: LINEAR and SPLINE model_index -- the index of the model. Should be 1 if only one model of position variations is in use. Of more than one model is in use, then the models are numbered consecutively from 1 to the last model. Maximum 8 models can be specified. interpolation_type -- one of LINEAR SPLINE

2.30   POSVAR_USE:

POSVAR_USE: model_index usage_flag Keyword POSVAR_INT specifies the action of position variations model is not available for the requested station, requested epochs. An alternative is either issue a warning and continue or print the fatal error message and stop. model_index -- the index of the model. Should be 1 if only one model of position variations is in use. Of more than one model is in use, then the models are numbered consecutively from 1 to the last model. Maximum 8 models can be specified. interpolation_type -- one of REQUIRED -- if position variation model is not available for a requested station, requested epoch, then stop. IF_AVAILABLE -- if position variation model is not available for a requested station, requested epoch, then print a warning, set variations to zero and continue.

2.31   AXIS_OFFSET_MODEL:

AXIS_OFFSET_MODEL: usage_flag usage_flag -- the flag. Supported values: YES -- (recommended) means that the contribution to delay due to antenna axis offset is taken into account. NONE -- means that the contribution to delay caused by the antenna axis offset is ignored. It is used for tests only. CALC9 -- forces VTD to emulated a bug in Calc9. This option is for tests only.

2.32   ANTENNA_DEFORMATIONS_FILE:

ANTENNA_DEFORMATIONS_FILE: [NONE or agd_file] Keyword ANTENNA_DEFORMATIONS_FILE specifies the file name that keeps parameters of the models of antenna deformation caused by gravity. The file should conforms AGD specifications. The current model tabulates the change of the focal length as a function of elevation for each antenna. Some antenna may me missing from the agd_file file. The contribution to delay caused by antenna deformations for these antenna will be set to zero.

2.33   ANTENNA_THERMAL_EXPANSION

ANTENNA_THERMAL_EXPANSION NONE or [MODEL antenna_information_file INSITU [NONE or insitu_file] TEMPERATURE [METEO or SPD] LAG time_in_seconds] Keyword ANTENNA_THERMAL_EXPANSION defines the mode for computing the contribution to time delay caused by antenna structures thermal expansion. The 1st qualifier may be NONE or MODEL. If the 1st qualifier is MODEL, then VTD expects to read 8 qualifiers. The second qualifier is the name of the antenna information file in the ANTI format. The antenna information file defines the type of each antenna, dimensions of the antenna structure and their coefficient of thermal expansion, reference temperature. Some antennas may be missing from this file. Contribution to path delay caused by antenna deformations of these antennas will be set to zero. The 3rd qualifier is INSITU. The 4th qualifier is the name of the file with information about antennas that have available data of their thermal height variation measurements with the invar rod. These stations will be excluded from computation of contribution due to antenna thermal deformation according to the model of thermal expansion. Position variations of the reference point for these antennas should be included to the model specified by POSVAR_MOD, POSVAR_FIL, POSVAR_INT, POSVAR_USE. The antenna deformations caused by thermal expansion depend on the effective temperature of elements of antenna structure. The 5th qualifier is TEMPERATURE. It defines the source of temperature data defined in the 6th qualifier METEO or SPD. If METEO, then temperature is supplied with VTD_METEO_IN subroutine. These are usually data collected by local meteorological sensor. If SPD, then air temperature is supplied in SPD (slant path delay) data files. It is computed from the output of the global numerical weather model. The 7th qualifier is LAG. The 8th qualifier defines the lag of antenna temperature with respect to air temperature. Antenna temperature at time t is computed as air temperature at time t - lag. Restrictinos: TEMPERATURE SPD requires EXTERNAL_DELAY_DIR directory names be defined that supplied the source of information about expansion coefficients via 3D B-splines.

2.34   METEO_DEF

METEO_DEF model Qualifier METEO_DEF defines the model that is used for computing missing meteorological parameters. If the atmospheric pressure and/or air temperature are negative, they are interpreted as missing. default_model: IMA -- the model of the International Meteorological Association ISO Standard atmosphere 1976. CALC -- Undocumented model that Calc uses. This model is for test only. NONE -- not to change meteorological parameters. Keep in mind, that if NONE specified, subsequent computation of zenith path delay using SAASTAMOINEN model will be __completely wrong__.

2.35   HYDROSTATIC_ZENITH_DELAY:

HYDROSTATIC_ZENITH_DELAY: [NONE or zenith_delay_path_model_name or MMF mmd_model_file ] Keyword HYDROSTATIC_ZENITH_DELAY specifies the name of the a priori model for the hydrostatic component zenith path delay. zenith_delay_path_model_name -- the name of the model. One of NONE -- do not model hydrostatic path delay SAASTAMOINEN -- Saastamoinen model MMF -- the Mean Mapping Function mode (Petrov (2009), in preparation). Requires the name of the file with the MMF model in the following qualifier.

2.36   WET_ZENITH_DELAY:

WET_ZENITH_DELAY: [NONE or zenith_delay_path_model_name] Keyword WET_ZENITH_DELAY specifies the name of the apriori model for the non-hydrostatic component of the zenith path delay. zenith_delay_path_model_name -- the name of the model. One of NONE -- do not model non-hydrostatic path delay MMF -- the Mean Mapping Function mode (Petrov (2009), in preparation). Requires the name of the file with the MMF model in the following qualifier.

2.37   HYDROSTATIC_MAPPING_FUNCTION:

HYDROSTATIC_MAPPING_FUNCTION: [NONE or mapping_function_name or [MMF mmf_mode file] ] Keyword HYDROSTATIC_MAPPING_FUNCTION defines the model for the mapping function for the hydrostatic component of the path delay -- dependence of the hydrostatic component of the atmospheric path delay with elevation. NB: the argument of the mapping function is so-called vacuum elevation: the elevation which the source would have in the absence of refractive atmosphere. mapping_function_name -- the name of the mapping function. One of NMFH -- Niell 1996 mapping function. MMF -- the Mean Mapping Function mode (Petrov (2009), in preparation). Requires the name of the file with the MMF model in the following qualifier.

2.38   WET_MAPPING_FUNCTION:

WET_MAPPING_FUNCTION: [NONE or mapping_function_name or [MMF mmf_mode file] or external_delay_dir ] Keyword WET_MAPPING_FUNCTION defines the model for the mapping function for the non-hydrostatic component of the path delay -- dependence of the non-hydrostatic component of the atmospheric path delay with elevation. NB: the argument of the mapping function is the so-called vacuum elevation: the elevation which the source would have in the absence of refractive atmosphere. mapping_function_name -- the name of the mapping function. One of NMFW -- Niell 1996 mapping function. MMF -- the Mean Mapping Function mode (Petrov (2009), in preparation). Requires the name of the file with the MMF model in the following qualifier.

2.39   ATMOSPHERE_TILT_PARTIALS:

ATMOSPHERE_TILT_PARTIALS: tilt_partials Keyword ATMOSPHERE_TILT_PARTIALS defines the model for partial derivatives of the atmospheric tilt, or using another words, atmospheric gradients. tilt_partials -- the name of tilt_partials model. Currently, only one value is supported: MACMILLAN_1995

2.40   SLANT_PATH_DELAY

SLANT_PATH_DELAY [SPD_3D or NONE] Keyword SLANT_PATH_DELAY defines that the path delay through the neutral atmosphere for a given elevation, azimuth, time for a given station should be computed by three-dimensional B-spline interpolation of the time series of slant path delays. These time series of path delays are supposed to have been computed at an elevation/azimuth grid for each station using a standalone program SPD_3D by solving numericly a system of non-linear differencial equations of wave propagation through the 4D, heterogeneous atmosphere (L. Petrov, 2009, in preparation) represented by the 4D field of atmospheric parameters that are the output of a numerical weather model. NB: the controbution of the neutral atmosphere can be computed either by using mapping function approach (keywords HYDROSTATIC_ZENITH_DELAY, HYDROSTATIC_MAPPING_FUNCTION, WET_MAPPING_FUNCTION, WET_ZENITH_DELAY) or by SLANT_PATH_DELAY. SPD_3D -- slant path delay will be computed by interpolation of time series of B-spline coefficients stored in files that are kept directory EXTERNAL_DELAY_DIR (or EXTERNAL_DELAY_DIR_2, EXTERNAL_DELAY_DIR_3, EXTERNAL_DELAY_DIR_4 if defined ) NONE -- algorithm for computing slant path delay by interpolation of time series of B-spline coefficients will be disabled.

2.41   ATMOSPHERE_PATH_DELAY_PARTIAL

ATMOSPHERE_PATH_DELAY_PARTIAL [NONE or NMW or NMF or IONO_350 or IONO_400 or IONO_450 or IONO_500 or TOTAL_SCALE or TOTAL_WATER or (GAUSSIAN_LAYER [layer_height layer_fwhm])] Keyword ATMOSPHERE_PATH_DELAY_PARTIAL defines partial derivative of slant path delay with respect to the path delay in zenith direction. This partial derivatives is not used for computing a priori path delay, but is supposed to be used for parameter estimation. The partial derivatives are placed in arrays DER_DEL, DER_RAT, in slots VTD__DER_AT1 (partial derivatives for station #1) and VTD__DER_AT2 (partial derivatives for station #2). NONE -- no partial is computed NMFH -- Niell (1996) hydrostatic mapping function NMFW -- Niell (1996) wet mapping function IONO_350 -- mapping function for the case when residual atmosphere is described as a thin shell at height 350 km. Such a model is suitable for characterizing residual ionosphere. IONO_400 -- mapping function for the case when residual atmosphere is described as a thin shell at height 400 km. Such a model is suitable for characterizing residual ionosphere. IONO_450 -- mapping function for the case when residual atmosphere is described as a thin shell at height 450 km. Such a model is suitable for characterizing residual ionosphere. IONO_500 -- mapping function for the case when residual atmosphere is described as a thin shell at height 500 km. Such a model is suitable for characterizing residual ionosphere. TOTAL_SCALE -- mapping function for the case when residual atmosphere is considered proportional to the total atmosphere. The partial derivative is defined as a ratio of the total slant path delay to the total path delay in the zenith direction. NB: this partial derivative requires computation of a priori slant path delay (SLANT_PATH SPD_3D). WATER_SCALE -- mapping function for the case when residual atmosphere is considered proportional to the water vapor contribution to the atmosphere. The partial derivative is defined as a ratio of the water vapor contribution of slant path delay to the water vapor contribution to path delay in the zenith direction. NB: this partial derivative requires computation of a priori slant path delay (SLANT_PATH SPD_3D). GAUSSIAN_LAYER -- layer_height layer_fwhm -- mapping function for the case when the dependence of concentration of the residual atmosphere is described with the Gaussian model with the specified height and the specified full width half maximum (FWHM). The height of the layer in meters is specified in the 3rd qualifier and the FWHM in meter is specified in the 4th qualifier.

2.42   EXTERNAL_DELAY_DIR

EXTERNAL_DELAY_DIR [NONE or directory_name] Keyword EXTERNAL_DELAY_DIR specifies the directory name of files with external path delays. The format of these files is defined by SLANT_PATH_DELAY keyword. If SLANT_PATH_DELAY is SPD_3D, then the files in the EXTERNAL_DELAY_DIR directory should satisty spd_3d_bin specification. Each file contains the time series of the B-spline coefficients for a specific station.

2.43   EXTERNAL_DELAY_DIR_2ND

EXTERNAL_DELAY_DIR_2ND [NONE or directory_name] Keyword EXTERNAL_PATH_DELAY_FILE specifies the secondary directory name of files with external path delays. Each file contains the time series of B-spline coefficients for a specific station. If a file for a given station is not found in directory EXTERNAL_DELAY_DIR, it is sought in directory EXTERNAL_DELAY_DIR_2ND.

2.44   EXTERNAL_DELAY_DIR_3RD

EXTERNAL_DELAY_DIR_3RD [NONE or directory_name] Keyword EXTERNAL_PATH_DELAY_FILE specifies the name of third directory of files with external path delays. Each file contains the time series of B-spline coefficients for a specific station. If a file for a given station is not found in directories EXTERNAL_DELAY_DIR, EXTERNAL_DELAY_DIR_2ND, it is sought in directory EXTERNAL_DELAY_DIR_3RD.

2.45   EXTERNAL_DELAY_DIR_4TH

EXTERNAL_DELAY_DIR_4TG [NONE or directory_name] Keyword EXTERNAL_PATH_DELAY_FILE specifies the name of fourth directory of files with external path delays. Each file contains the time series of B-spline coefficients for a specific station. If a file for a given station is not found in directories EXTERNAL_DELAY_DIR, EXTERNAL_DELAY_DIR_2ND, and EXTERNAL_DELAY_DIR_3RD, it is sought in directory EXTERNAL_DELAY_DIR_4TH.

2.46   IONOSPHERE_MODEL:

IONOSPHERE_MODEL: [NONE or directory_name] Keyword IONOSPHERE_MODEL specifies the directory name with files with ionospheric path delays. The contribution to path delay will be computed in accordance to this model. As of 2009.05.30 not implemented. Reserved for future use.

2.47   IONOSPHERE_DATA_DIR:

IONOSPHERE_DATA_DIR: [NONE or directory_name] Keyword IONOSPHERE_MODEL specifies the model for computing the contribution of the ionosphere to path delay. As of 2009.05.30 not implemented. Reserved for future use.

2.48   IONOSPHERE_DATA_DIR_2ND:

IONOSPHERE_DATA_DIR_2ND: [NONE or directory_name] Keyword IONOSPHERE_DATA_DIR_2ND specifies the name of the second directory with files with ionospheric path delays. The contribution to path delay will be computed in accordance to this model. As of 2009.05.30, its support is not implemented. Reserved for future use.

2.49   IONOSPHERE_DATA_DIR_3RD:

IONOSPHERE_DATA_DIR_3RD: [NONE or directory_name] Keyword IONOSPHERE_DATA_DIR_3RD specifies the name of the third directory with files with ionospheric path delays. The contribution to path delay will be computed in accordance to this model. As of 2009.05.30, its support is not implemented. Reserved for future use.

2.50   IONOSPHERE_DATA_DIR_4TH:

IONOSPHERE_DATA_DIR_4TH: [NONE or directory_name] Keyword IONOSPHERE_DATA_DIR_4TH specifies the name of the fourth directory with files with ionospheric path delays. The contribution to path delay will be computed in accordance to this model. As of 2009.05.30, its support is not implemented. Reserved for future use.

2.51   GRS_METRIC:

GRS_METRIC: metric_identifier Keyword GRS_METRIC specifies the name of the metric tensor for the geocentric reference system. metric_identifier -- Identifier of the metric tensor. Supported values: IAU2000 -- the metric tensor proposed by Kopeikin and Brumberg. recommended by IAU2000 resolution. ITRF2000 -- the metric tensor which was implicitly used in data analysis in the 20-th century, which was used for constructing the ITRF2000 catalogue of station positions and velocities. Comment: recommendation of IERS2003 is contradictory: in one place the authors of Conventions claimed that they compliant with the IAU2000 recommendation, at another place they propose formulae based on ITRF2000 metric.

2.52   TROP_AXOF_COUPLING:

TROP_AXOF_COUPLING: usage_flag The keyword TROP_AXOF_COUPLING specifies whether to compute contribution to delay due to coupling of the troposphere path delay and antenna axis offsets. By another words TROP_AXOF_COUPLING takes into account additional troposphere path delay due to motion of the reference point. usage_flag -- the flag. Supported values: YES -- to compute contribution due to coupling of the troposphere path delay and antenna axis offsets. NO -- not to compute contribution due to this coupling.

2.53   TROP_GEOMETRIC_COUPLING:

TROP_GEOMETRIC_COUPLING: usage_flag The keyword TROP_GEOMETRIC_COUPLING specifies whether to compute the contribution to delay due to coupling of the troposphere path delay and geometric delay. usage_flag -- the flag. Supported values: YES -- to compute contribution due to coupling of the troposphere path delay and geometric delay. NO -- not to compute contribution due to this coupling.

2.54   PARALLACTIC_ANGLE:

PARALLACTIC_ANGLE: usage_flag The keyword PARALLACTIC_ANGLE specifies whether to compute the contribution to phase delay and phase delay rate due to the parallactic angle. NB: the contribution of the parallactic angle to group delay is zero. usage_flag -- the flag. Supported values: YES -- to compute contribution to phase delay due parallactic angle NO -- not to compute contribution due to parallactic angle.

2.55   GALACTIC_ABERRATION:

GALACTIC_ABERRATION: usage_flag The keyword GALACTIC_ABERRATION specifies whether to compute the contribution to delay caused by the galactic aberration. usage_flag -- the flag. Supported values: YES -- to compute contribution to phase delay due parallactic angle NO -- not to compute contribution due to parallactic angle.

2.56   GEOM_EXPR_FAR_ZONE:

GEOM_EXPR_FAR_ZONE: model_name The keyword GEOM_EXPR_FAR_ZONE specifies the name of the expression for geometric delay in far zone (larger than 10 pc) in vacuum based on general relativity. model_name -- the name of the expression. Supported values: KS_1999 -- expression Kopeikin and Schaefer, 1999 PK_2001 -- expression Petrov and Kopeikin, 2001 (recommended)

2.57   GEOM_EXPR_NEAR_ZONE:

GEOM_EXPR_NEAR_ZONE: model_name The keyword GEOM_EXPR_NEAR_ZONE specifies the name of the expression for geometric delay in the near zone (from Earth's satellite to 10 pc) in vacuum based on general relativity. model_name -- the name of the expression. Supported values: LIGHT_TIME -- iterative solution of the light equation

2.58   SOURCE_STRUCTURE:

SOURCE_STRUCTURE: control_file_name The keyword SOURCE_STRUCTURE specifies the control file for modeling contribution to delay due to source structure. control_file_name -- the name of the control file or NO -- contribution to delay due to source structure will not be computed. This option is curretnly being tested.

2.59   DOPPLER_EXPR:

DOPPLER_EXPR: model_name The keyword DOPPLER_EXPR specifies the name of the expression for computation of the Doppler frequency shift for an object within the Solar system based on general relativity.

2.60   DELAY_RATE:

DELAY_RATE: YES or NONE The keyword DELAY_RATE specifies whether to compute delay rate. If DELAY_RATE is NONE computation runs faster. YES -- to compute delay rate using analytical expressions. NO -- not to compute delay rate.



Questions and comments about this guide should be directed to:

Leonid Petrov ( http://astrogeo.org/petrov )

Last update: 2016.11.17