OCCAM 5.0. USER'S GUIDE
Contents
1. 24 KOKEE 0 000 N N N 0 00000 0 000 0 000 0 000 GILCREEK 0 000 N N N 0 00000 0 000 0 000 0 000 NRAO20 0 000 N N N 0 00000 0 000 0 000 0 000 WETTZELL 0 000 N N N 0 00000 0 000 0 000 0 000 FORTLEZA 0 000 N N N 0 00000 0 000 0 000 0 000 CONSTRAINED DIRECTIONS al WETTZELL FORTLEZA AUXILIARY PARAMETERS TIME INT ZD ZDR ZRS CO CR CRS GR GRR KOKE 99 99 2 00 0 00 0 00 0 00 0 00 12 00 0 00 GILCREEK 99 99 2 00 0 00 99 99 1 00 99 99 12 00 0 00 NRAO20 2 00 2 00 0 00 99 99 1 00 99 99 12 00 0 00 WETTZELL 99 99 2 00 0 00 1 00 1 00 1 00 12 00 0 00 FORTLEZA 99 99 2 00 0 00 99 99 1 00 99 99 12 00 0 00 PIECEWISE LINEAR FUNCTIONS AND CONSTRAINTS NVERSE FRACTIONAL WEIGHT OF CONSTRAINTS 999 RATES RW ZDR PL RW CLR PL RW GRR PL MM SQRT H MM SQRT H MM SQRT H KOKEE 15 000 Y 0 000 N 0 000 N GILCREEK 15 000 Y 20 000 Y 0 000 N NRAO20 15 000 N 20 000 Y 0 000 N WETTZELI 5 000 Y 20 000 N 0 000 N FORTLEZA 15 000 Y 20 000 Y 0 000 N OFFSETS SIG ZDO EX SIG CLO EX SIG GRO EX MM MM MM KOKEE 0 000 N 0 000 N 0 500 N GILCREEK 0 000 N 0 000 N 0 500 N NRAO20 0 000 N 02. 313 328 Axis offset corrections delay and rate 329 408 Partial derivatives with respect to Z X Y RA Dec for delay and rate 409 424 Partial derivatives with respect to the nutation offsets obliquity and longitude Real 8 425 448 Partial derivatives with respect to the EOP X Y UT1 UTC Real 8 449 456 Thermal deformation of antenna Real 8 457 464 Source azimuth Real 8 465 480 Partial derivatives with respect to troposphere gradients Real 8 3 BASTIM 17 Direct access file with a record length of 144 bytes 1 4 Dummy integer Total number of records in first one 5 8 Record number of the observation in file SORTIM 9 16 Record number of the observation for station on STATIM 17 48 Observed delay and rate with formal errors 49 80 lonospheric correction for delay and rate and errors 81 104 Theoretical delay one second before one after and at the observation time 105 128 Theoretical rate one second before one after and at the observation time 129 136 Ambiguity correction term 4 DICTIO 21 Direct access file with a record length of 2128 bytes Each record represents one baseline and it contains the list of record numbers in BASTIM in which there is data of that baseline An ambiguity correction term for the baseline is also stored 5 STACAT 20 Direct access file with a record length of 128 bytes 1 4 Dummy integer Total number of stations on first record 5 12 Station name Character 8 13 36 Sta
3. 80 06 Card 7 Col 1 10 Time difference between reference epoch and the start of observation sec Col 11 20 Duration of observation sec Col 21 30 A priori UTC offset at site 1 sec Col 31 50 Observation frequency MHz Col 51 60 Group delay ambiguity ns 30 Col 71 78 Sequence number Col 79 80 07 Card 8 Col 1 20 lonospheric delay ns Col 21 30 Formal error of ionospheric delay ns Col 31 50 lonospheric delay rate ps sec Col 51 60 Formal error of ionospheric delay rate ps sec Col 71 78 Sequence number Col 79 80 08 31 APPENDIX B FORMATS AND EXAMPLES OF EXTERNAL FILES USED IN OCCAM 1 CATALOG File name any First two columns determine the record code RC RC TC terrestrial coordinates Col 1 2 Record code Col 4 11 Station name Col 12 28 X component m Col 29 43 Y component m Col 44 58 Z component m Col 60 63 Axis type Valid types are AZEL Azimuth elevation mounting EQUA Equatorial mounting X Y1 X Y mounting North South X Y2 X Y mounting East West Col 64 73 Axis offset m RC TV terrestrial velocities Col 1 2 Record code Col 4 11 Station name Col 12 19 X velocity m year Col 20 27 Y velocity m year Col 28 35 Z velocity m year RC CC celestial coordinates Col 1 2 Record code Col 4 11 Source name Col 13 27 Right ascension HH MM ss sssssss Col 32 47 Declination sDD MM ss sssss Col 50 57 Deviation in rig
4. SIGMA OF CONSTRAIN limits the strength of the constraint default 0 001 m The ECCENTRICITIES apply only to mobile sites and are the North East and Up component of the antenna with respect to the geodetic mark All values are in meters and the format is A8 2X F6 3 2X A1 2X F8 5 3F8 5 The next line asks how many directions will be constrained in the analysis Format 23X 13 If the number of fixed directions is not 0 there follow as many lines as constrained directions specifying the fixed baseline The constraint will be given 0001 m sigma Format is A8 1X A8 Also you will be asked to input manually the following information troposphere dispersion in cm 2 clock dispersion in cm 2 pole coordinates dispersion in cm 2 UT1 UTC parameter dispersion in cm 2 Pole parameters exponential coefficients UT1 UTC parameter exponential coefficient Phase for pole components Phase for UT1 UTC The expected values follow the questions on the screen Alternative choice can be made on user s feeling The amount of VLBI stations is limited to 8 ones for the option At the first step the observations are adjusted using weighted least squares method The post fit residuals are calculated to fix the outliers which are downweighted at the next step The output files UT1 DAT X_EOP DAT Y_EOP DAT contain the high frequency EOPs Format is F15 8 2X F10 7 for UT1 DAT F15 8 2X F9 6 for others Output
5. files etc A name related to the Experiment s date and type is a good choice e g IRISA570 B Catalog to be used 12 characters You must enter the name of the catalog for Source and Station coordinates See appendix B for a description of the format of the catalog An example of catalog is copied to your work directory when installing OCCAM with the name ITRF2000 CAT C Data File Name 12 characters The name of the NGS Format data file must be entered If any source or station included on the data set is not available on the catalog the program flags warning messages It is recommended to quit and update the catalog before continuing D The next step asks you if OCCAM shall create the OPT files automatically The default is Y for yes but have in mind that it is not necessarily the optimal choice for each individual session If you choose Y the next options below E F G to be answered more If you choose N there will be no more questions and you will follow to step H E The program shows a list of the existing stations and asks which of them is to be taken as reference If your input is not one of the observing stations the first station listed is chosen F The following question estimate atmosphere gradients is valid for the Kalman filter approach only G The following question 24 hour or INTENISIVE 2 hour experiment 24 02 specify which type of session to be analyzed The package has some limits in the numbe
6. parameters are in principle considered RANDOM WALK stochastic processes So all of them can be given a rate of change with time For a random walk the sigma of the change of the value after a time interval DT comes as SQRT PSD DT PSD is the power spectral density of the WHITE NOISE associated with the random walk If PSD 0 then the parameter is not allowed to change with time so it is considered a constant parameter The user has to provide the PSD values for all the parameters The units required are picoseconds 2 second for all the station parameters and arcseconds 2 day for the nutation and orientation terms There is one line for each parameter with format F10 3 in the same order as for the a priori values and sigmas In general only troposphere term and gradients and clock offsets are considered random walks but orientation terms could be allowed a small rate of change specially if long experiments more than 24 hours are analyzed The final results of the program are stored in the file KVLBI RES that can be directly printed Information about the evolution of the parameters with the successive filter iterations can be either seen in files KVLBI The program displays the post fit Chi squared of the residuals during process to check that the options selected are in accordance with the data 2 2 KALMAN FILTER PROCESS for operational EOP service in frame of IVS equivalent to running the program KVLBI_IE Files KVLBI_IE F
7. parameters can be estimated once per 24 hour session Moreover LSM allows the estimation of further auxiliary parameters atmospheric gradients offset and rate continuous piecewise linear functions AL t AL offset AL rate0 t to vt AL rate n t ty This example shows a continuous piecewise linear function plf for the zenith delay i e OCCAM 5 0 solves for one offset and several rates Plf s can also be used for the clocks and gradients Mind that auxiliary parameters for the clocks are always estimated in addition to the quadratic function mentioned above discontinuous functions OCCAM 5 0 also offers the possibility to solve for other kinds of functions for the auxiliary parameters zenith delay clock gradients For instance there is the chance to estimate offsets only for certain time intervals More details can be found in the description of the options file Ism opt 23 Constraints Constraints can be set for the offsets and rates of the auxiliary parameters Those constraints prevent the parameters from varying too much Furthermore the setting of the constraints might be necessary in order to avoid the singularity of the normal equations This is the case if parameters are estimated for a certain time interval with no observations contributing to this parameter Constraints are set by specifiying the sigmas for observation equations AL offset 0 sigma for the offset AL rate 0 sigma
8. to 11 ONSALA60 R PHR INS PHNS TEW PHEW 0 384 0 091 0 084 0 019 0 224 0 120 0 071 0 003 0 084 0 058 0 027 0 021 0 008 0 032 0 017 0 009 0 004 0 007 0 124 0 034 0 031 0 009 0 042 0 041 0 015 0 006 0 018 56 0 46 1 90 7 34 4 44 5 123 2 49 6 178 4 14 9 84 2 131 3 77 7 103 9 L722 55 0 25 2 165 0 173 3 75 4 97 6 40 8 94 8 119 0 25 4 98 7 L4 1 1774 0 4 ATMOSPHERIC LOADING CORRECTION DATA File names station _name ATM and ATMEAN97 These files have to be stored in the ATM directory Each line of the ATM files which contain the corrections for one station include the following Time of correction mjd four epoches per day corrections up east north m Format of the lines in ATMEANQ7 which contains corrections due to average pressure on sites It is subtracted from the correction to avoid offsets eight character station name correction offsets up east north m 5 THERMAL DEFORMATION CONTROL FILE File name THERMAL DEF The file THERMAL DEF contains mainly the info from the file titled thermal dat from the homepage of IVS Analysis Coordinator A Nothnagel homepage fittp miro geod uni bonn de vibi IVS AC Its format is The data is organized in blocks Each block contains two lines line 1 eight character station name line 2 f9 5 f6 1 1x f11 6 4 f6 1 i6 f6 1 gf 1 C expansion coefficient for foundation 34 hf m height of concrete foundation
9. will contribute 3 or 5 parameters clock offset rate and tropospheric term and if necessary two troposphere gradients After 2 nutation parameters and 3 EOP need to be estimated In brief the order of the parameters is Trop of St 1 Clk offset Clk rate Trop of St 2 and if necessary two troposphere gradients Clk offset Clk rate Trop of St n and if necessary two troposphere gradients Nutation in obliquity Nut in longitude X Y wobbles UT1 UTC corrections This order will be kept all over the program and is the order in which the parameters and sigmas are displayed in the output files KVLBI RES KVLBI Units are meters for all the station parameters including clock terms and arc seconds for nutation and EOP Format of each line is 2F20 3 If the user wants to constrain parameters to their a priori value then the a priori sigma must be reduced accordingly It permits that in practice some parameters are not estimated but are fixed to their a priori values Then we have a new comment line that permits to identify where the stochastic characterization of the parameters start All parameters are in principle considered RANDOM WALK stochastic processes So all of them can be given a rate of change with time For a random walk the sigma of the change of the value after a time interval DT comes as SQRT PSD DT PSD is the power spectral density of the WHITE NOISE associated with the random walk If PSD 0 then t
10. 0 Mbytes free space on Hard Disk to contain the program data files and solution outputs The executable code would need 4 Mbytes of space Your computer must have as many Mbytes of RAM memory as available But it is possible to compile all FORTRAN files with advanced compiler Lahey Fortran Power Station etc to make use all available RAM memory The best configuration to keep the program in your computer is to separate the program directory from the working directory where you process your data If you have a comressed Version of the OCCAM software all files will be in the right path after the decomression A suitable configuration may read like this CAOCCAM Executable code of OCCAM 5 0 C OCCAM BAT BATCH Files to run OCCAM Menu System C OCCAM SCR Screen files for the menu system C OCCAM COMPILE Source code of OCCAM C OCCAM EPHEM Ephemerides and EOP files C OCCAM ATM Atmospheric loading data C OCCAM WORK Working directory C OCCAM FIL Useful information C OCCAM DOC Documentation These are the files that are installed into your work directory CHOOSE COM COLLOCAT OPT EPHEM DAT OCCAM BAT KVLBI OPT KVLBI_IE OPT LOADING OCE LSM OPT THERMAL DEF OCCAM SCR You will also need to have a catalog file with extension CAT contains information about positions of stations and radiosources and velocities of stations The current version includes a ITRF2000 CAT file as well The file contains ITRF2000 catalog for station coordinates and vel
11. 000 N 0 500 N WETTZELI 0 000 N 0 000 N 0 500 N FORTLEZA 0 000 N 0 000 N 0 500 N A detailed explanation of every option follows The first line gives the user a chance to reweight and edit the data SIGMA ADDED means that a constant number is added quadratically to the apriori sigmas of the observables as they defined in the ngs data file It is given in meters FACTOR ADDED refers to the threshold for the editing of observations The smaller this factor is the more observations are downweighted The following criterion is used for the downweighting of the observation i w i 2 sqrt cofactor i gt factor v i is the residual of the observation and cofactor i is the cofactor aposteriori of the residual The format of the line is 12X F8 4 12X F8 4 12X A1 The second and third lines specify which troposphere models are available and which will be used respectively Presently the only option is the Niell mapping function A3 Mind that with OCCAM 5 0 LSM the dry zenith delay is calculated apriori and the wet zenith delay is estimated by the least squares analysis 25 The fourth line specifies the cutoff elevation angle The format is 18X F4 1 The fifth line gives the user the chance to downweight low obervations A1 The next line is then intended to provide the elevation angle from which downweighting should be started and the way of downweighting itself F4 1 2X A7 The next two lines allow the
12. 3X I3 If the number of fixed directions is not 0 there follow as many lines as constrained directions specifying the fixed baseline Format is A8 1X A8 Hint If all station coordinates should be fixed to their apriori values all directions and all heights have to be constrained In the next paragraph the time intervals for the estimation of the the auxiliary parameters have to be set Mind that there is no estimation of clock parameters for the first reference station If you want to solve for a piecewise linear function plf you have to set one offset for the whole experiment 24 00 or just take 99 99 and additionally the time intervals for the rates have to be specified e g 2 00 for a two hours time interval The Ism opt file above shows some examples for the parametrization plf for the zenith delay at KOKEE e g two hours time interval one hour discontinuous quadratic functions for the clock at WETTZELL two hours discontinuous functions for the zenith delay at NRAO20 twelve hours offsets for the gradients for all stations In particular the items are NAME ZENITH DELAY OFFSET ZENITH DELAY RATE ZENITH DELAY RATE SQUARED CLOCK OFFSET CLOCK RATE CLOCK RATE SQUARED GRADIENT OFFSET GRADIENT RATE The format is A8 3X 8 F5 2 1X The inverse fractional weight of constraints should be set to 999 by default By using it the sigmas of the constraints for the plf s can be adapted to the numbers of observations within a
13. 62 Data quality flag 0 means good data 29 Col 64 68 Delay and delay rate type Col 69 69 if ionospheric calibration applied Col 70 70 C if cable calibration applied Col 71 78 Sequence number Col 79 80 02 Card 3 Col 1 20 Correlation coefficient and formal error Col 21 40 Fringe amplitude and formal error J Col 41 70 Total fringe phase and formal error rad Col 71 78 Sequence number Col 79 80 03 Card 4 Col 1 15 System temperature at site 1 and formal error K Col 16 30 System temperature at site 2 and formal error K Col 31 45 Antenna temp at site 1 and formal error K Col 46 60 Antenna temp at site 2 and formal error K Col 71 78 Sequence number Col 79 80 04 Card 5 Col 1 20 Cable cal correction for sites 1 and 2 ns Col 21 40 WVR parameter at site 1 and formal error ns Col 41 60 WVR parameter at site 2 and formal error ns Col 62 64 WVR parameter definition code at sites 1 and 2 0 parameter is zenith path delay 1 parameter is path delay along line of sight Col 71 78 Sequence number Col 79 80 05 Card 6 Col 1 20 Ambient atmosph temperature at sites 1 and 2 C Col 21 40 Ambient barometric pressure at sites 1 and 2 mb Col 41 60 Atmospheric humidity parameter at sites 1 and 2 Col 62 64 Humidity parameter definition at sites 1 and 2 0 Relative humidity 1 Dew point C 2 Wet bulb temperature C Col 71 78 Sequence number Col 79
14. C report71 pdf To apply the ocean loading corrections the program needs an external file with the amplitudes and arguments of the main tidal components for the model This file must be called LOADING OCE and when installing the package an example with real data for all VLBI stations is copied into your work directory In Appendix B you can find a description of the format in case you need to update this information How to use STATION CORRECTIONS AND DERIVATIVES The program allows the user to select if any correction to station coordinates should be neglected By default all corrections are included but the user can neglect up to four effects BY DEFAULT ALL CORRECTIONS WILL BE ADDED TO THE DATA BASES DO YOU WANT TO CHANGE THIS Answering Yes you will receive the following message THIS CORRECTIONS ARE APPLIED A ANTENNA DEF B OCEAN LOAD C ATMOS LOAD D POLE TIDE SELECT THE CORRECTIONS YOU WANT TO NEGLECT And the user can select which of them to drop 1 5 GEOMETRIC MODEL equivalent to running the program GEOMET Files GEOMET FOR QUASAR1 FOR SLOG FOR ARC FOR OPENING FOR Purpose This program computes the theoretical delays and delay rates for each observable included in the original data file It considers the geometrical configuration of antennas and all relativistic effects The information is stored on the file BASTIM How to use GEOMETRIC MODEL The program can use one of three available geometric mode
15. OADING DATA Required for Station Corrections and Derivatives option in the Model Computation Menu 1 3 If you want to add corrections due to the ocean loading effect you must provide the amplitudes and phases of the main tidal components at each station The example file LOADING OCE contains real data for several antennas The name of the file must be LOADING OCE so you can simply add the information for your antennas to the present file or update the existing information if better data is available The files are provided by WHans George Scherneck via ftp service fto gere oso chalmers se pub hgs oload olrs19 VLBI blq A close description of the strategy to obtain the coefficients can be found at the Web address http www oso chalmers se hgs One version of the file is enclosed See appendix B for a detailed explanation of the file and its format D THERMAL DEFORMATION DATA Required for the Station Corrections and Derivatives option in the Model Computation Menu 1 3 and recommended by the IERS Conventions The description of the model used can be found in Haas et al 1999 http Awww dgfi badw de dgfi DOC report71 pdf The antenna dimensions information is taken from the file THERMAL DAT from the IVS Analysis Coordinator s homepage http miro geod uni bonn de vibi IVS AC The initial mean temperature has been chosen using some summarized experiences If we did not have a reliable amount of data the value is equal to 999 C and no corre
16. OCCAM 5 0 USER S GUIDE O Titov V Tesmer J B hm8 1 Australian Surveying and Land Information Group Canberra Australia 2 German Geodetic Research Institute Munich Germany 3 Vienna Technical University Vienna Austria ABSTRACT OCCAM 5 0 has new limits 20 stations and 100 radiosources can be processed simultaneously The number of baselines under study is 190 correspondingly The current version of OCCAM supports IERS Conventions 2000 The ephemeride DE405 LE405 takes the place of DE403 LE403 To correct subdiurnal EOP variations two models can be chosen proposed by Ray recommended by IERS Conventions 1996 and by Eanes IERS Conventions 2000 which takes into account many more tidal terms A new least squares approach based on the Gauss Markov model is available with the new version USER S GUIDE MODIFICATIONS LOG WRITER INSTITUTION DATE VERSION NUMBER 1 N Zarraoa IAG Madrid 18 03 1991 2 0 2 N Zarraoa IAG Madrid 13 01 1992 3 0 3 N Zarraoa SK Honefoss 17 12 1993 3 3 4 O Titov IAA St Petersburg 18 05 1997 3 4 5 O Titov SPbU St Petersburg 1999 4 0 6 O Titov SPbU St Petersburg J Bohm TU Vienna May 2001 5 0 V Tesmer DGFI Munich DISTRIBUTION LIST Name Institute M N Kulkarni Survey of India Dehradun India B R Pettersen Norwegian Agriculture University Norway V Tesmer German Geodetic Research Institute Munich Germany Z Malkin Institute of Applied Astronomy Saint P
17. OR KALMAN FOR MATRIX FOR ARC FOR OPENING FOR Itis a approach for operational EOP analysis similar to 2 1 Station positions are fixed using reference frame recommended by IERS The program is controlled by the file KVLBI_IE OPT An example of the file is shown below IGMA ADDED 01 FACTOR ADDED 5 DWN MAN IGN D METERS ROPOSPHERIC MODEL NIELL ELL 85 ES NUTATION OFFSET ES EARTH ORIENTATION PARAMETERS O STATION COORDINATES ES ATMOPSPHERIC GRADIENTS STATIONS 3 V CONSTRNT __N_ ECC __E ECC __H_ ECC ETTZELL 0 0 N 0 00 NSALA60 0 0 N 0 00 RYSILNO 0 0 N 0 00 CONSTRAINED DIRECTIONS 0 A PRIORI PARAM AND FORMAL ERRORS M NO ST 1 5 3 4 5 0 0 ley 0 0 0 010 0 0 00 20 O HOBZ2ZK ZK KAZHN 18 oie O ae So O H O oO D a RIORI POWER SP DENSITY PS 2 S NO STATIONS 1 5 3 5 oe oe O O OOOO LO O OOOO OOO HOO oh Oo OOo Oo OO OOo OOo OOO O OOOO O FO OO Or AA OTO O O He 0 Or Or OO Or O ORC OOO OO A detailed explanation of every option follows The first line gives the user a chance to reweight and edit the data SIGMA ADDED means a constant factor to add quadratically to the a priori si
18. as an example See Appendix B for a description Any name is valid for this file B EPHEMERIS TABLE Required for Precession and Nutation option in Model Computation Menu 1 2 You must create a file called EPHEM DAT for your experiment This file should contain Earth Orientation Parameters hereafter EOP You can obtain this information from the International Earth Rotation Service IERS C04 series from IERS http npiers obspm fr eop pc You will have to include EOP data not only for the experiment s date but also for several days around Nine or more data records should provide a more precise interpolation OCCAM 5 0 version makes use of the Lagrangian interpolation scheme and can add subdiurnal EOP corrections as recommended by the IERS Sun Earth and Moon ephemerids This information is available from DE LE405 code in accordance with IERS 2000 Conventions It is advisable to include 5 6 days of data in your table for a better interpolation OCCAM requires an information with 0 5 day steps OCCAM can generate the EPHEM DAT file for the experiment automatically In order to do that you have to provide a complete ephemeride catalog for the year of the experiment you want to run and a similar file for EOP The name of the files must be EPHEM ye and EOP ye where ye is the year of the experiment 99 00 01 They should be stored in the OCCAM EPHEM subdirectory A description of the files can be found in appendix B C OCEAN L
19. ates Local meteorological data and source coordinates azimuth hour angle and elevation are also included here BASTIM has one record for each single scan pair baseline time It contains the observed and theoretical delays and rates ionospheric corrections etc STACAT is a catalog of the stations included in the experiment DICTIO is a directory of where to look for different items of data For each baseline it specifies in which record of BASTIM each scan is included These files are Direct Access files Their contents can be read using 3 1 Extract information from OCCAM Standard Files BATCH is a list of the present baselines of It also specifies which catalogue is used and whose stations should be run METEOR is an ASCII file containing surface meteorological data and cable calibrations extracted from the original Data File It can be used to check if any station has no meteorological data available A detailed description of all these files is found in appendix C In following steps the package generates other files that will be described when necessary How to use DATA HANDLING When you select this option you are advised that any existent OCCAM SDF will be erased As the names of the files are fixed erasing them at the beginning avoids errors in the future The program will ask the user to provide some information A Experiment Name 8 characters It gives a key for the experiment that can be followed when backing up
20. ay provide some assistance only if you send to the OCCAM Coordinator a written report as complete as possible on the problem found 7 We strongly recommend that if you find any bug or error in the source code of OCCAM you send a report about it to the OCCAM Coordinator to distribute a corrected version to all the users 8 You may have implemented new modules or upgraded already existent ones in OCCAM that could be useful for other users If you want your changes to be definitely implemented in the standard version of OCCAM send the new source code with complete information about the new features to the OCCAM Coordinator Upgraded versions of OCCAM will be periodically distributed to all users CONTENTS PRELIMINARY INFORMATION Introduction Configure your computer to run OCCAM What do really need to process data Running OCCAM V5 0 CHAPTER 1 COMPUTE MODEL AND CREATE STANDARD DATA FILES 1 1 Automatic model computation 1 2 Data handling 1 3 Precession and nutation 1 4 Station corrections and derivatives 1 5 Geometric model CHAPTER 2 COMPUTE EXPERIMENT SOLUTION 2 1 Kalman Filter Process geodetic 2 2 Kalman Filter Process EOP service 2 3 Least squares collocation method 2 4 Least squares method CHAPTER 3 UTILITIES 3 1 Extract information from OCCAM standard files 3 2 Extract Obs Calc files APPENDIX A Description of NGS data formats APPENDIX B Formats and examples of external and output f
21. cause set of station in frame of One special network is not fixed When you compare your resulting EOP time series you must remember that the set of constrained stations are kept for all sessions Therefore it is reasonable to fix EOP in spite of loss of your result accuracy How to use MULTIBASELINE KALMAN ANALYSIS for geodetic tasks The program is controlled by file KVLBI OPT file An example of the file is shown below SIGMA ADDED 01 FACTOR ADDED 5 DWN MAN IGN D METERS TROPOSPHERIC MODEL NIELL NIELL 85 YES NUTATION OFFSET NO EARTH ORIENTATION PARAMETERS NO ATMOPSPHERIC GRADIENTS NO STATIONS 3 V CONSTRNT __N_ECC __E_ECC H_ECC ETTZELL 0 0 N 0 00 NSALA60 0 0 N 0 00 RYSILNO 0 0 N 0 00 066 018 2e8Z3 ONSTRAINED DIRECTIONS 1 ETTZELL ONSALA60 PRIORI PARAM AND FORMAL ERRORS M NO ST 1 6 1 10 10 10 10000 010 10 10 10 10000 010 ORI POWER SP DENSITY PS 2 S NO STAT 1 6 1 FOO Or O OECO O Ore Oi OO OOS O7nO7 Or OOO ve A detailed explanation of every option follows The first line gives the user a chance to reweight and edit the data SIGMA ADDED means a constant factor to add qua
22. certain time interval 42X 13 The next paragraph specifies the constraints for the rates of the plf s Mind that plf s have to be marked with Y in order to distinguish them from discontinuous functions The units of the constraints Sigmas are comparable to those of random walk parameters mm sart h The items are NAME ZENITH DELAY RATE PLF Y or N CLOCK RATE PLF GRADIENT RATE PLF A8 3 3X F7 3 2X A1 26 The last paragraph contains information for the offsets of the auxiliary parameters Do not use an offset constraint for the wet zenith delay but do use a constraint for the gradient offset If the sigma for the offset is set to 0 000 no constraint will be applied The items are NAME ZENITH DELAY OFFSET EX CLOCK OFFSET EX GRADIENT OFFSET EX A8 3 8X F7 3 2X A1 The symbol EX means that external information e g zenith delays by GPS can be introduced but this options does not work with this version 27 CHAPTER 8 UTILITIES INTRODUCTION In this option we have included some programs that usually are not needed during standard processing but that may be useful in certain cases With this option the user will see the following menu OCCAM V 5 0 UTILITIES MENU 3 1 Extract information from OCCAM Standard Files 3 2 Extract Obs Calc Files lt Return gt Previous Menu 3 1 EXTRACT INFORMATION FROM OCCAM STANDARD FILES DUMPTHEO Files DUMPTHEO FOR OPENING FOR ARC FOR This options allows to extract
23. ck to the System Menu and select Option 2 to get the Solution Computation Menu SCM D OCCAM 5 0 version supports Kalman filter least squares method and least squares collocation technique to get the solution CHAPTER 1 COMPUTE MODEL AND CREATE STANDARD DATA FILES INTRODUCTION When you enter option 1 in the System Menu your screen will look this way OCCAM V5 0 MODEL COMPUTATION MENU 1 1 Automatic Model Computation 1 2 Data Handling 1 3 Precession and Nutation 1 4 Station Corrections and Derivatives 1 5 Geometric Model lt Return gt Previous Menu These options allow you to reformat your data set into OCCAM SDF compute models and corrections to generate theoreticals for the observables and compute partial derivatives for the adjustment You can choose between the automatic model generation in option 1 1 or step by step model generation using options from 1 2 to 1 5 Before running any of this options all the previous ones must have been already completed More detailed descriptions of these options follow 1 1 AUTOMATIC MODEL COMPUTATION This option is equivalent to running options 1 2 1 3 1 4 and 1 5 in this order Thus refer to the following items for explanations 1 2 DATA HANDLING Equivalent to running the program DTAUO Files DTAU FOR OCCAM_N FI DTAU1 FOR LSM_OPT FOR OPT FOR ARC FOR OPENING FOR Purpose This option reads the original VLBI data files for the exper
24. ction will be applied The user can change it A description of the THERMAL DEF file can be found in appendix B E ATMOSPHERIC LOADING DATA Also required for the Station Corrections and Derivatives option in the Model Computation Menu 1 3 and recommended by the IERS Conventions The data must be stored in a subdirectory OCCAM ATM Each station has got an own time series of corrections though a own station_name ATM file The version 5 0 interpolates the quarter daily corrections computed by Scherneck which can be found and downloaded on http www oso chalmers se hgs apload html These data sets are computed with the today s probably most reliable approach This approach additionally needs the file ATMEAN97 which consists of correction offsets due to a mean pressure for each station http www oso chalmers se hgs apload html These are subtracted from the corrections by the software A description of the files is to be found in appendix B F CONTROL FILES All OPT files are required for running the solutions with the Solution Computation Menu Chapter 2 KVLBI OPT is used for the Kalman Filter Process Multibaseline 2 1 KVLBI_IE OPT is used for the Kalman Filter Process Multibaseline 2 2 COLLOCAT OPT is used for the Least Squares Collocation Technique 2 3 OPT is used for the Least squares method LSM 2 4 A description of these files is provided in Chapter 2 G To use some utilities you may need other
25. defined by the IAU We call this choice xGRS i B use scaling x TT i x GRS i 1 L G where L G 6 969 10 What we observe is actually the delay in terms of TT so the choice between 1 and 2 is clear choice 2 should be used Absolutely INDEPENDENT of the choice between 1 and 2 we have to choose between the possibilities A and B The IAU in 1997 in Kyoto has officially prohibited to use the scaled coordinates x TT i So the IAU choice is A and the IAU approach is 2A 2 for time A for coordinates IERS1992 is 1A this is also equivalent to 2B that is the formula for 2B is absolutely the same as for 1A within the required accuracy Note that IERS1996 was wrong in all meanings different and wrong choices of scaling However the ITRF2000 was decided to be represented by scaled coordinates xTT i this is against the IAU resolutions but it was decided by a ITRF meeting in November 2000 Therefore it is expected that the new IERS Conventions will support both the IAU choice 2A and the ITRF choice 2B with appropriate explanations CHAPTER 2 COMPUTE EXPERIMENT SOLUTION INTRODUCTION Before running this option the SDF must have been generated and completely filled by option 1 They must be present at your work directory When you select this option your screen will show you the following menu OCCAM V5 0 SOLUTION COMPUTATION MENU 2 1 Kalman Filter Process geodetic 2 2 Kalman Filter Process EOP serv
26. dratically to the a priori sigmas of the observables as they come in the data file It is given in meters FACTOR ADDED refers to the threshold for data editing The program computes the expected sigma of the observed calculated delays If the difference is bigger than FACTOR times the expected sigma then it may act 16 according to the following option DWN MAN IGN If D the observation will be Downweighted if M the user will be asked to take a decision interactively Manually if it will be used as such Ignore the warning The format of the line is 12X F8 4 12X F8 4 12X A1 The 2nd and 3rd lines specify that troposphere model by Niell is available and which will be used respectively Also the 3rd line specifies a limit of zenith distance Z in degrees Below the limit all observations will be downloaded by multiplication on factor to sec Z 2 The 2nd line is not read and the format of the 3rd is A3 4X F3 0 The 4th line allows the user to turn off NO NUTATION or on YES NUTATION the estimation of nutation offsets 5th line works the same way with the estimation of EOP Both are read with A1 format If the user wants to estimate only some of the EOP or only one of the nutation offsets it can be done by constraining the sigma of the a priori value as is explained below The 6th line indicates if the troposphere gradients to be estimated or not A1 The 7th line specifies the number of stations to be processed in forma
27. e one after and at the observation time Real 8 433 440 Earth Rotation velocity Real 8 441 488 X wobble and Y wobble one second before one after and at the observation time 489 560 Moon X Y Z geocentric coordinates one second before one after and at the observation time Real 8 561 632 Geocentric sun coordinates X Y Z one second before one after and at the observation time Real 8 633 680 Partial derivatives of the source direction unit vector with respect to nutation obliquity 3 and longitude 3 All Real 8 681 752 Final matrix of precession and nutation nine components all Real 8 2 STATIM 18 Direct access file with a record length of 480 bytes 1 4 Dummy integer Total number of records on first one 5 8 Record number for this station in file STACAT 9 12 Record number of this observation in SORTIM 13 40 Temperature Pressure Humidity and humidity factor All Real 8 Last one integer 41 48 Cable calibration Real 8 49 120 Station coordinates X Y Z one second before one after and at the observation time Real 8 121 192 Station Coordinates Longitude latitude height one second before one after 36 and at the observation time 193 264 Zenith distance hour angle and local sidereal time one second before one after and at the observation time 265 280 Zenith tropospheric path delay dry and wet 281 312 Tropospheric mapping functions or corrections for delays and rates Models Niell 2 values
28. etersburg Russia M Kudryashova Saint Petersburg University Saint Petersburg Russia A Mowlam Melbourne University Melbourne Australia Qian Zhihan Shanghai Observatory Shanghai China V Zharov Shternberg Astronomical Institute Moscow Russia H Schuh Vienna Technical University Vienna Austria PREFACE 1 OCCAM V 5 0 is a Research and Development package for the analysis of geodetic and geodynamics VLBI experiments It is distributed freely 2 The OCCAM Coordinator will be responsible for maintaining the configuration control on the standard OCCAM Modifications that prove their worth and usefulness may be incorporated to the standard version and distributed to all users 3 Presently the OCCAM Coordinator name and address is Oleg Titov Australian Surveying and Landing Information Group AUSLIG PO Box 2 Belconnen Canberra ACT 2616 Australia Tel 61 2 62014361 Fax 61 2 62014366 E mail OlegTitov auslig gov au 4 Please do not distribute the package OCCAM by yourself without informing the OCCAM Coordinator This formality will help the distribution of upgraded versions of the package to all interested users 5 If you find any part of this User s Guide difficult to understand incomplete or in disagreement with your experience as OCCAM user please send your comments and suggestions to the OCCAM coordinator preferably via electronic or standard mail 6 If you find serious problems using the OCCAM package we m
29. files You will find descriptions of those files either in appendix B or the chapter referring to the utility itself H There are other necessary files created by OCCAM like the OCCAM Standard Data Files SDF or the clock model file These are described in chapter 1 and appendix C RUNNING OCCAM V 5 0 Once you have configured your computer and installed the basic files into your hard disk you just have to enter OCCAM and your screen will look like this OCCAM V5 0 SYSTEM MENU 1 Compute Model and Create Standard Data Files 2 Compute Experiment Solution 3 Utilities lt Return gt Exit to DOS Detailed descriptions of the different options will follow To select any item you only have to enter the corresponding number IMPORTANT Remember not to hit lt RETURN gt after the number because the option is only used to quit or go one menu back If your Menu present options like 1 2 you must only enter the last digit as selection First digit corresponds to the main menu option number So for 1 2 you only enter 2 The normal sequence of operations needed to process an experiment is the following A Select Option 1 to get the Model Computation Menu MCM B From the MCM choose options 1 2 1 3 1 4 and 1 5 in this order All four options have to be completed If you want to repeat any of them the following ones have to be repeated as well With option 1 1 Automatic mode you make the complete chain C Go ba
30. files are also INFORM DAT SKO DAT EPS DAT ERP DAT The file INFORM DAT contains a priori information used for the session analysis 22 The file SKO DAT contains the calculated values normalized chi squared and weighted root mean squared w r m s in cm The file EPS DAT contains post fit residuals without separation on baselines The order numbers of VLBI sites are included here as well in cm The file contains a daily estimates of five EOPs as average values for the session all in arcsec 2 4 LEAST SQUARES METHOD BASED ON THE GAUSS MARKOV MODEL LSM Equivalent to running the program LSM Files LSM FOR LSM_OPT FOR MNK FOR DSINV FOR OUTB FOR READOPT FOR PREPARE FOR TIMSPLIT FOR ABAT2 FOR ARC FOR OPENING FOR Purpose OCCAM 5 0 is able to do a classical least squares estimation with a large variety of parameters that can be determined during the analysis Principally LSM is a two step approach with bad observations being downweighted after the first estimation step The basic number of parameters nr1 to be estimated for a 24 hour experiment is nr1 1 nantenna 1 7 2 3 nantenna the number of stations i e for the reference station OCCAM 5 0 only solves for one troposphere wet zenith delay whereas for the other antennas the station coordinates x y z and three clock parameters offset rate and rate squared are also adjusted Additionally two nutation parameters and three earth orientation
31. for the rate Additionally the sigmas for the constraints can be further modified by setting an inverse fractional weight ifw of the constraints The reason for this option is that there is a difference whether you set a constraint for a parameter with 300 or 100 observations contributing to it In other words the more observations you have the smaller must be the sigma to have an equally powerful constraint Example 300 observations contributing to a parameter time interval 2 hours sigma random walk is set to 20 mm sart h in the options file ifw is set to 10 variance 20 2 2 mm 2 h 2 200 mm 2 h 2 variance 200 300 10 So the sigma 2 58 mm h is used for the observation equation If we only had 100 observations the sigma would be 4 47 mm h Nevertheless if you are not sure about this option just set the ifw to 999 By doing so no ifw is applied How to use the LEAST SQUARES METHOD The program is controlled by the file LSM OPT An example of the file is shown below 0 0 COSZ 2 ES NUTATION OFFSET NO EARTH ORIENTATION PARAMETERS NO FREE SOLUTION NO STATIONS 5 V N E CONSTRNT _ N_ ECC E ECC H_ECC SIGMA ADDED 0 010 FACTOR ADDED 5 00 DWN MAN IGN D TROPOSPHERIC MODEL NIELL NIELL CUTOFF ELEVATION 10 0 NO DOWNWEIGHTING FOR LOW ELEVATIONS COSZ COSZ 2 2 X
32. gmas of the observables as they come in the data file It is given in meters FACTOR ADDED refers to the threshold for data editing The program computes the expected sigma of the observed calculated delays If the difference is bigger than FACTOR times the expected sigma then it may act according to the following option DWN MAN IGN If D the observation will be downweighted if M the user will be asked to take a decision interactively Manually if it will be used as such Ignore the warning The format of the line is 12X F8 4 12X F8 4 12X A1 The 2nd and 3rd lines specify that troposphere model by Niell is available and which will be used respectively Also the 3rd line specifies a limit of zenith distance Z in degrees Below the limit all observations will be downloaded by multiplication on factor to sec Z 2 The 2nd line is not read and the format of the 3rd is A3 4X F3 0 The 4th line establishes the estimation of nutation offsets 5th line works the same way with the estimation of EOP Both are read with A1 format If the user wants to estimate only some of the EOP or only one of the nutation offsets it can be done by constraining the sigma of the a priori value as is explained below The 6th line indicates that station coordinates are not estimated A1 The 7th line indicates if the troposphere gradients to be estimated or not A1 The 8th line specifies the number of stations to be processed in format 13X 12 There is
33. he collocation technique allows to estimate subdiurnal variations of the EOPs with time resolution which corresponds to rate VLBI observation performance one point per a few minutes Station positions are fixed using reference frame recommended by IERS The program is controlled by the file COLLOCAT OPT An example of the file is shown below SIGMA ADDED 01 FACTOR ADDED 6 DWN MAN IGN D METERS TROPOSPHERIC MODEL LANYI DAVIS MARIN CHAO NIELL 85 YES NUTATION OFFSET YES EARTH ORIENTATION PARAMETERS NO ATMOSPHERIC GRADIENTS NO STATIONS 6 CONSTRNT N WESTFORD GILCREEK HARTRAO HOBART26 ALGOPARK MATERA CONSTRAINE WESTFORD M CC E Q Q H Q Q O GO O OOO Ff De o eO o w HO OQO OGOGO NOOO O O OG we Nie E TE T DE H I OGO OOOO 0O Pe SS eS Be tee ee sere A detailed explanation of every option follows The first line gives the user a chance to reweight and edit the data SIGMA ADDED means a constant factor to add quadratically to the a priori sigmas of the observables as they come in the data file It is given in meters FACTOR ADDED refers to the threshold for data editing The program computes the expected sigma of the observed calculated delays If the difference is bigger than FACTOR times the expected sigma then it may act 21 according to the follo
34. he parameter is not allowed to change with time so it is considered a constant parameter The user has to provide the PSD values for all the parameters The units required are arcseconds 2 day for the nutation and orientation terms There is one line for each parameter with format F10 3 in the same order as for the a priori values and sigmas 20 In general only troposphere and clock offsets are considered random walks but orientation terms could be allowed a small rate of change specially if long experiments more than 24 hours are analyzed Otherwise the troposphere gradients can be considered as a constant parameters If the control file has some errors more stations than quoted not enough parameter lines for a priori values sigmas or PSD etc the program flags a warning message and aborts Check that the number of lines coincides with the number of parameters or stations in each block The final results of the program are stored in the file KVLBI RES Information about the evolution of the parameters with the successive filter iterations can be either seen in files KVLBI The program displays the post fit chi squared of the residuals during process to check that the options selected are in accordance with the data 2 3 LEAST SQUARES COLLOCATION METHOD Equivalent to running the program COLL Files COLL FOR COLL_ALL FOR C_EOP_0 FOR DSINV FOR INFORM FOR MK1 FOR READING FOR SUBS1 FOR SUBS2 FOR ARC FOR OPENING FOR T
35. ht ascension _ss sssssss Col 60 66 Deviation in declination SS SSSSSS Source coordinates must be provided in J2000 0 reference frame RC HH Col 1 2 Record code Col 4 70 Comments RC EP epoch of the terrestrial coordinates velocities Col 1 2 Record code Col 4 9 Epoch years 2 EPHEMERIS FILE File name ERPHEM DAT First four columns determine the record code RC 32 RC EOP1 or Earth orientation parameters Col 1 4 Record code Col 7 13 Modified Julian date of the data Col 15 22 X wobble arcsec Col 23 30 Y wobble arcsec Col 33 41 UT1 UTC sec Col 44 45 TAI UTC integer number of seconds Col 47 53 Nutation angle Dpsi arcsec Col 55 61 Nutation angle Deps arcsec RC MOOND Moon ephemeris position and velocity Col 1 5 Record code Col 6 13 Modified Julian date of data Col 14 157 X Y Z geocentric coordinates X Y Z velocities RC EARTD Col 1 5 Record code Col 6 13 Modified Julian date of data Col 14 157 X Y Z barycentric coordinates X Y Z velocities RC SUND Col 1 5 Record code Col 6 13 Modified Julian date of data Col 14 157 X Y Z geocentric coordinates X Y Z velocities The program assumes that the tables are given in UTC time for interpolation If you generate EPHEM DAT automatically you need global files for ephemerids and EOP The ephemerids file for one year must be called EPHEM ye and it is convenient that it overlaps a little w
36. ice 2 3 Least squares collocation method 2 4 Least squares method lt Return gt Previous Menu Detailed description of this menu follows 2 1 MULTIBASELINE KALMAN ANALYSIS Equivalent to running the program KVLBI Files KVLBI LFOR KALMAN FOR MATRIX FOR ARC FOR OPENING FOR Purpose OCCAM 5 0 can perform a direct multibaseline analysis using the Kalman Filter theory to get the least squares results for the station positions and nutation offsets while considering clock and atmospheric terms as stochastic processes random walks model This estimation program has been tested by Nestor Zarraoa about 1992 with respect to the program SOLVE developed by the NASA Goddard Space Flight Center VLBI group showing the equivalence of both programs at the formal error level of the VLBI results Similar results have been found with respect to other implementation of the Kalman Filter method for VLBI analysis by Tom Herring MIT You are able to estimate the station positions with fixed EOP parameters and without fixing of them At the former case all systematic in a priori EOP will move to your geodetic results but it will be a unificated system of results with errors At the latter case you will prevent your geodetic results from EOP incompleteness using some constrained But you will have to apply for the same constrains fixing a set of stations from session to session to a reference frame Practically it is impossible case be
37. ifo ga 1 C expansion coefficient for antenna hp m height of antenna pillar hv m height of vertex hs m height of subreflector hd m height of declination shaft 10 gt factor for hs is 0 9 for prime focus antennas only 20 gt factor for hs is 1 8 reference temperature C The usual reference temperature used for designing and constructing buildings is 20 C In this approach mean temperatures at the sites are used for not generating offsets to the coordinates 35 APPENDIX C DESCRIPTION OF OCCAM INTERNAL FILES 1 SORTIM 19 Direct access file with record length of 752 bytes 1 4 Dummy integer On first record total number of records 5 12 Source name Character 8 13 28 Right ascension and declination at 2000 0 Real 8 29 40 Modif Julian date and fraction of day in radians Integer 4 and Real 8 41 48 Integer number of seconds between UTC and TAI Real 8 49 168 Apparent RA and Dec and geocentric source direction unit vector 3 for one second before one after and at the observation time All Real 8 169 240 Earth barycentric coordinates X Y Z one second before after and at the observation time Real 8 241 312 Earth barycentric velocity X Y Z one second before after and at the observation time Real 8 313 384 Earth barycentric acceleration X Y Z one second before after and at the observation time Real 8 385 432 Greenwich sidereal time and hour angle one second befor
38. iles APPENDIX C Description of OCCAM internal files PRELIMINARY INFORMATION INTRODUCTION The package OCCAM V 5 0 provides a useful tool to process VLBI sessions with an Personal Computer PC running with WINDOWS version 95 or higher Complete tests have been carried out with Pentium II Pentium III based processors Additionally the version 5 0 is in regular use with LINUX The software package OCCAM consists of several executable programs which must be used in strict order to get a solution of a VLBI session There are some auxiliary programs in the package too The executables can be started manually or automatically via batch files Please note that the batches work with WINDOWS only Their use is not supported by LINUX It is recommended to use powerful computers for data analysis because the modern observational experiments include the tremendous number of observations This user s guide will concentrate on the use of OCCAM on a PC environment Since the previous OCCAM 4 0 version the following changes have been done IERS Conventions 2000 replaced the IERS Conventions 1996 Least squares method was added as an option to get a solution Troposphere gradients can be estimated optionally Reference station can be chosen manually Elevation cut off angle can be specified at the opt file OCCAM does not use virtual disks anymore CONFIGURE YOUR COMPUTER TO RUN OCCAM It is recommended to have at least 1
39. iment given in NGS format and converts them into OCCAM SDF which are used by the rest of the options in the package Detailed description of the NGS Format is provided in Appendix A The program reads global Ephemeris and EOP catalogs and creates the file EPHEM DAT specific for the experiment to be processed The user can also create EPHEM DAT himself The file format is described in Appendix B The information needed is described in the option 1 8 PRECESSION AND NUTATION The package OCCAM generates and uses several SDF These are called SORTIM STATIM BASTIM BATCH DICTIO and STACAT All these files are created by this option A file called METEOR containing the meteorological data from the stations is also generated but it is not used any more by the package This option creates the files with their final size The rest of the options only add or read information on them SORTIM stores information regarding sources and time One record is reserved for each source time combination It contains the observation time tag UTC the source observed and its coordinates interpolated EOP Ephemeris of Sun Earth and Moon sidereal time etc STATIM includes information regarding stations It reserves one record for each pair station observation time Station coordinates corrected for Earth Tides Ocean Loading Pole Tide etc are stored here as well as tropospheric models axis offsets and partial derivatives with respect to source and station coordin
40. information from OCCAM SDF Data can be extracted from BASTIM STATIM SORTIM and STACAT Information from BASTIM can be extracted by record number by source by station or the whole file There are interactive menus to select how to extract the data for all files Information from STATIM can be extracted from the whole file by source or by record number Information from SORTIM is extracted by record number If file STACAT is to be read the full file is processed File OUTPUT XTC contains the extracted information 3 2 EXTRACT OBS CALC FILES Code EXTRACT Files EXTRACT FOR OPENING FOR ARC FOR This option reads the SDF and generates a series of outputs with several information OUTPUT OMC includes the Obs Calc values plus the tropospheric calibrations DAVIS model It writes the station names source name year day of year hour minute integer second observed minus computed delay atmospheric correction for station 1 and 2 The format is 1X A8 1X A8 2X A8 2X 14 1X 13 1X 312 2X 3D22 16 OUTPUT THE includes the theoretical delays The variables written are record number station names source name year day of year hour minute second theoretical without atmospheric model and theoretical with atmospheric model The format used is 18 A8 1X A8 2X A8 2X 14 1X 13 1X 312 2X 2D22 16 OUTPUT PAR lists the partial derivatives respect to all parameters It writes the station names source name year day of year and hour minute seco
41. ith the previous and next year Each record must contain all the information for each epoch in free format The variables are Record number Epoch Earth barycentric coordinates X Y Z velocities X Y Z Sun geocentric coordinates X Y Z and velocities X Y Z Moon geocentric coordinates X Y Z and velocities X Y Z The EOP file for one year must correspond to the EOP1 series in the current implementation of OCCAM and the format is free in the following order Epoch MJD X wobble Y wobble UT1 UTC UT1 TAI 3 OCEAN LOADING DATA File name LOADING OCE The data is organized in blocks One block for each station Each block contains Record 1 Station name from column 1 to 8 Record 2 Amplitude of radial displacement for each component 7 characters per value m Record 3 Amplitude of horizontal north south displacement for each component 33 7 characters per value m Record 4 Amplitude of horizontal east west displacement for each component 7 characters per value m Record 5 Phase of radial displacement for each component 7 characters per value Deg Record 6 Phase of horizontal north south displacement for each component 7 characters per value Deg Record 7 Phase of horizontal east west displacement for each component 7 characters per value Deg The tidal components are indexed in the following order M2 S2 N2 K2 K1 O1 P1 Q1 MF MM SSA Example of block Only nine components shown but can be up
42. known reasons Perhaps there are strong non tidal effects in pole motion Then the user will have to choose the a priori nutation model A IAU 1980 NUT MODEL ON DEFAULT B HERRING MODEL C MBH_2000 MODEL Default is A but the choice depends on the goal of the solution The most precise model should be MBH_ 2000 The next option is to choose the Short Period UT1 variations to apply if option A selected in the very first step of this program FOR THE TIDAL UT1 VARIATIONS YOU CAN CHOOSE BETWEEN A IERS STANDARDS 1989 UT1 UT1R SHORT PERIOD lt 35 DAYS B IERS CONVENTIONS 1992 UT1 UT1S SHORT AND LONG PERIODS SELECT YOUR PREFERENCE For good interpolation of UT1 we need to subtract short term variations with periods less than 35 days The default in OCCAM is A because the updated model of the IERS Conventions 1996 includes the terms that are already present on the EOP tables that are standard in OCCAM The bulletin B 1 days series EOP1 code in ERPHEM DAT has no terms with period shorter than 35 days applied Thus after interpolation option A is applied to restore the terms in final UT1 time series Overall there are three steps 1 Subtraction of short term lt 35 days terms 2 Interpolation 3 Restoration of short term lt 35 days terms IMPORTANT Other sources for EOP may require a special use of the UT1 corrections and or interpolation methods that are not included in OCCAM 5 0 Before
43. ls SELECT THE RELATIVISTIC MODEL TO BE APPLIED A IERS 1992 MODEL B IERS 1996 MODEL C IAU 1997 MODEL Enter your selection A B C Q to quit The default model is A from IERS Conventions 1992 what differs from previous OCCAM version The user can also choose whether to apply Earth Gravity correction to light propagation or not Default option is to apply it This option is not available for IAU 1997 model It always applies the Earth Gravity correction to light propagation that can not be deselected Meanwhile the choice of correct relativistic model is not a simple problem Sergey Klioner kindly prepared a short description on the topic see below If you use ITRF2000 system you will have to choose the option A default If you want to use the IAU 1997 option you will have to scale the coordinates of stations from ITRF catalogue The VLBI model can be symbolically written as c t 2 t 1 k x 2 x 1 additional terms Here c the speed of light t 1 time epoch of arrival the wave front to site x 1 t 2 time epoch of arrival the wave front to site x 2 k scaling factor The exact form of these additional terms depends also on the scaling you use for t i and x i The possibilities for t i 1 use TCG 2 use TT The possibilities for x i A use no additional scaling that is use directly the spatial coordinates of the Geocentric Celestial Reference System as
44. nd observed minus computed delay and the partial derivatives with respect to X Y Z 1st station X Y Z 2nd station atmospheric parameter 1st and 2nd station RA and Declination of source 28 nutation obliquity and longitude The format is A8 1X A8 2X A8 2X 14 1X 13 1X 312 2Xx 13D15 8 These files are useful for plotting comparison or debugging APPENDIX A DESCRIPTION OF THE NGS VLBI FORMAT NGS VLBI DATA FORMAT 1 Site cards Col 1 8 Site name Col 11 25 Site X component m Col 26 40 Site Y component m Col 41 55 Site Z component m Col 57 60 Axis type Col 61 70 Axis offset End of site cards is indicated by END 2 Source cards Col 1 8 Source name Col 11 28 Right ascension HH MM SS SSSSSSSSS Col 31 48 Declination sDDMMSS SSSSSSSSS End of source cards is indicated by END 3 Auxiliary parameters Col 1 20 Reference frequency Col 21 30 Group delay ambiguity spacing Col 32 33 Delay type GR or PH Col 35 36 Delay rate type GR or PH End of this card is indicated by END 4 Data cards Card 1 Col 1 18 Names of site 1 and site 2 Col 21 28 Source name Col 30 60 Time YYYY MM DD HH MM SS SSSSSSSSSSS Col 61 70 Run identification code Col 71 78 Sequence number Col 79 80 01 Card 2 Col 1 20 Observed delay ns Col 21 30 Formal error of observed delay ns Col 31 50 Observed delay rate ps sec Col 51 60 Formal error of observed delay rate ps sec Col 61
45. nd Sun and Moon geocentric position and velocities That info can be included under the headers EARTD SUND MOOND If global catalogs are available for the user the option 1 2 can be used to generate directly EPHEM DAT entering the path where those files are Their name has to be EPHEM ye or EOP ye where ye means the year 99 00 01 etc Check the formats of those files in appendix B DE405 LE405 ephemerides are used for OCCAM 5 0 How to use PRECESSION AND NUTATION During the execution of this program you can turn off several models that are applied in this program The following menu is displayed DEFAULT MODELS WILL BE APPLIED FOR A SHORT PERIOD UT1 VARIATIONS B EFFECT OF OCEANIC TIDES ON UT1 AND POLAR MOTION DO YOU WANT TO CHANGE THIS Y N Q TO QUIT You can turn off any of them at this step The default is applying them both The next step will be a more detailed question on the model for the effect of oceanic tides on UT1 and polar motion if model option B chosen before CHOOSE MODEL TO BE APPLIED FOR A RAY MODEL IERS 96 CONVENTIONS B EANES MODEL IERS 2000 CONVENTIONS ON DEFAULT The default in OCCAM is B Both options A and B use the Lagrangian interpolation scheme for EOP as recommended by the IERS The test calculations showed that for UT1 UTC there is a good agreement between observational and model subdiurnal variations For pole coordinates difference are larger due to un
46. ocities and ICRF extension 1 for radiosources coordinates Pay attention that the disk C is used on default OCCAM and data files to be stored into the disk C Corresponding paths are included in all BAT files If you use another disk the BAT file must be updated for data analysis WHAT DO REALLY NEED TO PROCESS DATA 1 INPUT DATA FILES FOR THE EXPERIMENT OCCAM uses VLBI data in NGS Format If your data is in any other format you must change it to NGS before using OCCAM NGS files can be downloaded from data servers of the IVS like ftp cddisa gsfc nasa gov vlbi ivsdata ngs If you have NGS Format data follow the instructions in Chapter 1 2 NECESSARY FILES When you install OCCAM several files are copied to your work directory Some of them are examples of the necessary files described below Some other files may also be necessary It may be very useful for you to create similar files e g own catalogs ephemerids tables option files etc according to your needs These are the files you need to run OCCAM A CATALOG Required from beginning to end You should create your own catalog containing the coordinates and velocities if you wish to apply an a priori velocity model of the stations and the celestial coordinates of the sources involved in the experiment It would be useful to create a global catalog with all the stations and sources you may need The installation of the OCCAM 5 0 provides you with the file ITRF2000 CAT
47. ock fixed will only contribute the first parameter its tropospheric term and if necessary two troposphere gradients All the other stations will contribute 6 or 8 parameters X Y Z position clock offset rate and tropospheric term and if necessary two troposphere gradients If nutation is to be estimated 2 more parameters will be there If Earth Orientation is to be solved 3 parameters more are to be included In brief the order of the parameters is Trop of St 1 and if necessary two troposphere gradients X Y Z Clk offset Clk rate Trop of St 2 and if necessary two troposphere gradients X Y Z Clk offset Clk rate Trop of St n and if necessary two troposphere gradients Nutation in obliquity Nut in longitude if on X wobble Y wobble UT1 UTC corrections if on This order will be kept all over the program and is the order in which the parameters and sigmas are displayed in the output files KVLBI RES KVLBI etc Units are meters for all the station parameters including clock terms and arc seconds for nutation and EOP Format of each line is 2F20 3 17 If the user wants to constrain parameters to their a priori value then the a priori sigma must be reduced accordingly It permits that in practice some parameters are not estimated but are fixed to their a priori values Then we have a new comment line that permits to identify where the stochastic characterization of the parameters start All
48. one line for each station to be processed in which the following information is provided NAME ADDED SIGMA VERTICAL CONSTRAIN SIGMA OF CONSTRAIN ECCENTRICITIES NORTH EAST UP The NAME must coincide with the name on the data file and catalogs The ADDED SIGMA is used for reweighting the data from that station The value will be added quadratically to the a priori sigma of the observable VERTICAL CONSTRAIN Y or N indicates if the height component of the stations will remain fixed or not to the a priori value At the option it should be N always SIGMA OF CONSTRAIN limits the strength of the constraint default 0 001 m The ECCENTRICITIES apply only to mobile sites and are the North East and Up component of the antenna with respect to the geodetic mark All values are in meters and the format is A8 2X F6 3 2X A1 2X F8 5 3F8 5 The next line asks how many directions will be constrained in the analysis Format 23X 13 At the option should be 0 always Next line is just a comment line but it must be there It helps to find where the parameter count starts Then there are as many lines as parameters to be solved with their a priori value and sigma of such a priori The number of parameters are as follows The first station which will be considered master station for the coordinates fixed and clock fixed will only contribute the first parameter its tropospheric term and if necessary two troposphere gradients All the other stations
49. r of observations it can handle Version 5 0 is limited to 20 Stations 100 Sources and 1000 different scans observation to a single source at the same time by two or more stations If these limits are overflown then error messages are displayed and the program aborts H The program can generate automatically the file EPHEM DAT used by the 1 3 option PRECESSION AND NUTATION To do so the user has to provide the path to search for the global ephemerides and EOP files The pathway OCCAM EPHEM is recommended More details about EPHEM DAT can be found in appendix B 1 3 PRECESSION AND NUTATION equivalent to running the program PN Files PN FOR EANES FOR VLPN FOR NUTATION FOR MHB FOR HERR_NUT FOR ARC FOR OPENING FOR RAY FOR MATRIX FOR ROT FOR Purpose This option transforms between the J2000 0 Celestial Reference Frame for the quasars to their apparent positions in the observation time EOP and Ephemeris data for Sun Earth and Moon are read from a file called EPHEM DAT and interpolated to each observation s epoch See appendix B for a complete description of the formats of the file This information is stored on file SORTIM for further use The information for EPHEM DAT can be obtained in several ways Earth Orientation Parameters IERS distributes EOP C04 yearly time series from IERS Web site http hpiers obspm fr eop pc Ephemeris Global catalogs of ephemerides can provide barycentric Earth position and velocity a
50. t 13X 12 There is one line for each station to be processed in which the following information is provided NAME ADDED SIGMA VERTICAL CONSTRAIN SIGMA OF CONSTRAIN ECCENTRICITIES NORTH EAST UP The NAME must coincide with the name on the data file and catalogs The ADDED SIGMA is used for reweighting the data from that station The value will be added quadratically to the a priori sigma of the observable VERTICAL CONSTRAIN Y or N indicates if the height component of the stations will remain fixed or not to the a priori value SIGMA OF CONSTRAIN limits the strength of the constraint default 0 001m The ECCENTRICITIES apply only to mobile sites and are the North East and Up component of the antenna with respect to the geodetic mark All values are in meters and the format is A8 2X F6 3 2X A1 2X F8 5 3F8 5 The next line asks how many directions will be constrained in the analysis Format 23X 13 If the number of fixed directions is not 0 there follow as many lines as constrained directions specifying the fixed baseline The constrain will be given 0 001 m sigma Format is A8 1X A8 Next line is just a comment line but it must be there It helps to find where the parameter count starts Then there are as many lines as parameters to be solved with their a priori value and sigma of such a priori The number of parameters are as follows The first station which will be considered master station for the coordinates fixed and cl
51. tion a priori coordinates X Y Z Real 8 37 44 Epoch for the a priori coordinates Real 8 45 68 A priori velocity of the station X Y Z Real 8 69 72 Mounting type 37 73 88 Axis offsets 89 112 Longitude latitude and height 113 120 Geocentric radius of station 121 128 Equatorial component of station vector 6 BATCH ASCII file with the list of the involved baselines 7 METEOR ASCII file with the meteorological data and cable calibration extracted from NGS format input file 8 CLOCK BREAKS MODEL Filename BREAKS RES Each record contains information about one single clock break but the Kalman Filter program only reads columns 1 to 3 The third column information is not use now The format is I3 2x 13 Col 1 3 Station Code number Col 5 8 Time Code number Col 11 14 Clock break type 1 Clock offset jump 1 Clock rate variation Example of file 4 55 1 0 1 63 1 0 38
52. user to decide whether nutation and earth orientation parameters should be solved for Both are read with A1 format Mind that presently only one set of nutation and or eop parameters can be estimated for one 24 hour experiment The next line is intended to specify whether a free network solution should be estimated This option does not work yet A1 The next line specifies the number of stations to be processed The format that is used is 13X 2 There is one line for each station to be processed in which the following information is provided NAME ADDED SIGMA CONSTRAINT VERTICAL NORTH EAST SIGMA OF VERTICAL CONSTRAINT ECCENTRICITIES NORTH EAST UP The NAME must coincide with the name in the data file and catalogs The ADDED SIGMA is used for reweighting the data from that particular station This value will be added quadratically to the apriori sigma of the observable VERTICAL CONSTRAINT Y or N indicates if the height component of the stations will remain fixed or not to the apriori value The NORTH and EAST CONSTRAINTS do not work yet The SIGMA OF VERTICAL CONSTRAINT limits the strength of the vertical constraint default 0 001m The ECCENTRICITIES apply only to mobile sites and are the North East and Up component of the antenna with respect to the geodetic mark All values are in meters and the format is A8 2X F6 3 2X 3 A1 2X F8 5 3F8 5 The next line asks how many directions will be constrained in the analysis Format 2
53. using any other source for EOP please read carefully its description and check which options in OCCAM are best for using that data 1 4 STATION CORRECTIONS AND DERIVATIVES equivalent to running the program STATION Files STATION FOR OCCAM_N FI CORREC FOR PARTIALS FOR TROPOSPH FOR ATM_SCH FOR MATTEW FOR ARC FOR OPENING FOR Purpose This program stores the following information on file STATIM A Corrections to the catalog station coordinates due to earth tides B Further such corrections due to antenna deformations ocean loading atmospheric loading and the secular pole tide can be deselected Antenna axis offset contributions to delays and rates Troposphere models by A Niell Local source coordinates azimuth elevation hour angle Partial derivatives of the delay with respect to station source coordinates nutation parameters and EOP amoo The model for the solid earth tides used in OCCAM 5 0 is the model by Matthews and Dehant 1999 as recommended by the IERS CONVENTIONS 2000 exception the part for permanent tide correction In accordance with conventional approach different from IERS official recommendations the part for permanent tide restitution has not been activated Thus OCCAM s reference surface on the earth is the artificial surface as used by almost all known space geodetic softwares For further information the user is referred to MATTHEWS 1999 http www dgfi badw de dgfi DO
54. wing option DWN MAN IGN If D the observation will be downweighted if M the user will be asked to take a decision interactively Manually if it will be used as such Ignore the warning The format of the line is 12X F8 4 12X F8 4 12X A1 The 2nd and 3rd lines specify that troposphere model by Niell is available and which will be used respectively Also the 3rd line specifies a limit of zenith distance Z in degrees Below the limit all observations will be downloaded by multiplication on factor to sec Z 2 The 2nd line is not read and the format of the 3rd is A3 4X F3 0 The 4th line establishes the estimation of nutation offsets 5th line works the same way with the estimation of EOP Both are read with A1 format The 6th line indicates if the troposphere gradients to be estimated or not A1 The 7th line specifies the number of stations to be processed in format 13X 12 There is one line for each station to be processed in which the following information is provided NAME ADDED SIGMA VERTICAL CONSTRAIN SIGMA OF CONSTRAIN ECCENTRICITIES NORTH EAST UP The NAME must coincide with the name on the data file and catalogs The ADDED SIGMA is used for reweighting the data from that station The value will be added quadratically to the a priori sigma of the observable VERTICAL CONSTRAIN Y or N indicates if the height component of the stations will remain fixed or not to the a priori value At the option it should be N always
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