CALC 10 Release Memo David Gordon 2006 April 26 Calc version 10 is released. It has been updated to comply with the IERS Conventions (2003). Below is a brief summary of the changes and new features. Comments, suggestions, question, complaints, etc should be sent to me at dgg@leo.gsfc.nasa.gov. For instructions on running Calc 10, see the Calc User's Guide, file calc_01.txt, in your $SOLVE_HELP_DIR directory. Details of a comparison of Calc 9 and Calc 10 will be published in the 2006 IVS General Meeting Proceedings. A preliminary version (postscript) can be found at http://lupus.gsfc.nasa.gov/discussions/calc10/calc10.ps TRF-to-CRF Solid Body Rotation: Calc 10 now uses the CIO-based method (the 'new paradigm') for rotating from Earth-fixed coordinates to the celestial reference frame. Most of the new code for this was taken from SOFA-based routines on the IERS web site at USNO and modified as needed to compute time derivatives and various partial derivatives. The rotation matrices are saved in the databases, as in Calc 9, but the Lcode name has been changed from 'CF2J2000' to 'CF2J2K '. Calc 10 also computes a classical TRF-to-CRF rotation matrix. It uses the IAU2000A nutation model, along with modifications to precession, Greenwich Siderial Time, polar motion, and a bias rotation, as specified by the 2003 Conventions. The two version of the TRF-to-CRF rotation matrix are supposed to be very nearly identical. I have checked this for a few epochs and find that they produce rotated site positions differing by no more than ~30 microns (~1 micro-arc-sec), and usually much less. Nutation/Precession Modules: Calc 10 makes 2 different nutation/precession computations. First, the X and Y coordinates of the Celestial Intermediate Pole {CIP) in the Geocentric Celestial Reference System (GCRS) and s (provides the position of the Celestial Intermediate Origin [CIO] on the equator of the CIP) are computed (using a modified version of SOFA-based subroutine XYS2000A). They are stored in the database under the new type 2 Lcode 'NUT2KXYS', dimensioned (3,2). Second, the classical nutation offsets (delta-psi, delta-epsilon) are computed based on the IAU2000A nutation model (using a modified version of the SOFA-based subroutine NU2000A). These offsets are stored in the database under the new type 2 Lcode 'NUT2000A', dimensioned (2,2), which replaces Lcode 'NUT 1996'. Partial derivatives of the delays and rates with respect to X and Y are computed from the CIO-based formulation, and stored in the database under the new type 2 Lcode 'NUT2KXYP', dimensioned (2,2). Partial derivatives of the delays and rates with respect to the classical nutation offsets, delta-psi and delta-epsilon, are also computed and stored under the new Lcode 'NUT2000P', dimensioned (2,2), which replaces 'NUT PART'. Calc 10 still also computes the old Wahr nutation (IAU1976/1980 Precession/Nutation models), and saves the difference between the IAU1980 and IAU2000A nutations. The current version of Solve estimates classical nutation corrections with respect to IAU2000A, using the 'NUT2000P' partials. It then converts these to both delta-X and delta-Y corrections, and corrections to the IAU1980 (Wahr) nutation. This scheme should be accurate to a few micro-arc-seconds in X and Y, but eventually, Solve should be modified to use the 'NUT2KXYP' partials and estimate X and Y corrections directly. The conversion from IAU2000A nutation offsets to IAU1980 (Wahr) nutation offsets applies a precession rate difference and a frame offset. Our comparisons with Calc 9 solutions though shows that this conversion may not be quite correct. Polar Motion Module: The polar motion rotation matrix now uses an additional term, s', which provides the position of the Terrestrial Intermediate Origin (TIO) on the equator of the CIP. There is a rotation about the Z-axis of -s', which has a small effect on UT1. Short period ocean tide and nutation contributions to polar motion are now computed, as directed by the 2003 Conventions. The short period nutation contributions are computed using the terms of Table 5.1, and the short period ocean tide contributions are computed using subroutine Ortho_EOP. (Ortho_EOP was coded by Richard Eanes and is based on Richard Ray's ocean tide model.) These two contributions should be added after interpolation of the Xp and Yp tabular pole coordinates, according to the new Conventions. These contributions will be optional in Calc/Solve (i.e., not included in the default delays and rates). They will be available via the Lcodes 'WOBNUTAT' and 'WOBORTHO', which can be applied using the Solve CORF-file. If turned on, the jmg96.hf model should be turned off in Solve. UT1 Module: UT1 is now used to compute an Earth rotation angle, as specified in the IERS Conventions (2003), for use in the CIO-based transformations. And the computation of Greenwich siderial time, needed for the classical transformations, has been modified according to the new Conventions. Subroutine Ortho_EOP also computes a short period UT1 correction for ocean tide effects, which Calc 10 stores under the Lcode 'UT1ORTHO'. It also can be applied using the Solve CORF-file. ('WOBORTHO' and 'UT1ORTHO' should only be applied together, not singly, in Solve; and if they are applied, the jmg96.hf model should be turned off.) Some structural changes were made in the UT1 interpolation. Calc 10 no longer applies (in default mode) any smoothing of the tabular points. [Previous versions removed the fortnightly terms (originally called the Yoder terms) from the tabular values. The interpolation for each observation epoch was made using the modified tabular points, then fortnightly terms at the observation epoch were added back to the interpolated value at each epoch.] However, Calc has used a 1-day EOP series for many years now, and these fortnightly terms all have periods of 5 days or greater, so removing and then restoring them has almost no effect. Die-hard users can still apply UT1 smoothing by setting the UT1 flag (KUT1C) equal to 4. If this option is used, the fortnightly terms model by Defraigne and Smits (1999) is used, as given by the coefficients of Table 8.1 from the IERS Conventions (2003). Calc 10 was also changed so that it will only accept a 1.0 day interval EOP series. Planetary Ephemeris Module: The JPL DE/LE405 ephemeris is now used. Two binary versions will be distributed with Calc 10. One is a 100-year file (1950-2050, 9.3 Mbytes) for use on big Endian architectures (file DE405_be.jpl). The other is an 80-year file (1960-2040, 7.5 Mbytes) for little Endian architecture (file DE405_le.jpl). The user should check and verify that the proper version gets into the param.i file in directory $MK5_ROOT/include. [For details on making and reading ephemeris files, see the JPL web site ftp://ssd.jpl.nasa.gov/pub/eph/export.] Fundamental Arguments: The luni-solar terms were updated to match the IERS Conventions (2003) and expanded to include the 9 planetary terms. They are used for the CIO-based computations. Calc 10 also has two other sets of fundamental arguments (for use in the IAU2000A nutation model and for use in the IAU1980 (Wahr) nutation model) each with small differences in some of the components. Fundamental arguments were saved in the databases by Calc 9, but were never used. Calc 10 no longer saves them. Solid Earth Tides Module: Some small changes were made to match the new Conventions, as described in Chapter 7. Step 1 is unchanged from Calc 9, except there is now no elastic/anelastic option. Step 2 uses different tables and additional terms. The partial derivatives defined by John Gipson for Calc 9 were never used and have been removed. Pole Tide Module: Mean (secular) pole offsets are subtracted from the polar motion values, then these modified X-pole and Y-pole values are used to compute the pole tide corrections. We use the linear approximation formalae (IERS Conventions (2003), Chapter 7, eqns 22, 23a and 23b.) for the secular offsets. The same was done in Calc 9, but with slightly different linear formulae. Also as in Calc 9, we compute a delay and rate contribution ('PTOLDCON') that will remove this step. Adding the 'PTOLDCON' values to the delays and rates will be the same as computing the pole tide with X-pole and Y-pole values uncorrected for secular polar motion. Axis Offsets Module, Antenna Tilts: Calc 10 has been updated to read an antenna fixed-axis tilt file. This file has a large set of tilts (E-W and N-S) for Pietown (from 1989-2004), and single tilts for the other 9 VLBA antennas (only SC-VLBA's is significant though). If anyone knows of other antennas that should be included here, please let me know. We'll try to get this file updated, as the last Pietown data is two years old. Calc 10 will read these tilts and use them in the axis offset computations, if they are provided when Calc is run. The tilt file name can be provided in the external input mode (see the Calc users guide, file calc01.txt), or via a param.i definition, or via a database record type 1 Lcode ('AXISTILT') input read. An output Lcode contribution is also written ('TILTRMVR'), which can be used in Solve (via the CORFxx file) to remove this correction. The default will be to use the tilt corrections. A small error was found in the axis offset computations. Apparently it was never quite correct. A small atmosphere term was incorrectly modified several versions ago, when it should have been replaced with a relativity correction. It has finally been corrected. The effect is to slightly reduce the axis offset formal errors and change some axis offset by up to ~0.1%. A Calc 10 set of axis offsets will be made available to the community in the near future. Ocean Loading Module: The ocean loading module in Calc 10 has not changed from Calc 9. However, we obtained new ocean loading coefficients for all stations using the GOT00.2 model and replaced the earlier coefficients in blokq.dat. These were obtained from the ocean loading service web site at Chalmers University (http://www.oso.chalmers.se/~loading), with assistance from Hans-Georg Scherneck. Atmosphere Loading, Antenna Thermal Deformation: No corrections will be made in Calc 10. Solve has some models for these effects, and they will be used there. Correlator version: Not much has been done yet on the correlator version. Use of the high frequency EOP and the antenna tilts (at the VLBA correlator) may slightly improve astronomy usage. The other changes in Calc 10 should have little effect though. Apriori's to use with Calc 10: A new blokq.dat file has been generated for use with Calc 10. We used site and source positions from a recent Globl solution, and GOT00.2 ocean loading coefficients. The new blokq.dat file will be distributed with the Calc/Solve release. ********************************************************************************* Old Lcodes removed by Calc 10: Type 1 PEP TAPE 2 AXO2CONT 2 C82ETCON 2 PERMDEF 2 ELASTCON 2 GDNUTCON 2 EQE DIFF 2 OLDEQCON 2 FUNDARGS 2 ETJMGPAR 2 NUT 1996 2 NUT PART 2 CF2J2000 New Lcodes added by Calc 10: Type 1 AXISTILT (2,#sites) - Axis tilt information (arc-minutes) 2 NUT2000A (2,2) - Nutation - delta-psi, delta-epsilon 2 NUT2000P (2,2) - Nutation partials - delta-psi, delta-epsilon 2 NUT2KXYS (3,2) - Nutation - X, Y, S 2 NUT2KXYP (2,2) - Nutation partials - X, Y 2 CF2J2K (3,3,3) - TRF-to-CRF rotation matrix 2 TILTRMVR (2,1) - Removes tilt correction (sec) 2 WOBNUTAT (2,1) - Short period nutation corrcection to Xp, Yp 2 WOBORTHO (2,1) - Short period ocean tidal correction to Xp, Yp 2 UT1ORTHO (2,1) - Short period ocean tidal correction to UT1 Old Lcodes Replaced by New Lcodes by Calc 10: Type Old Dimensions New Dimensions New Dimensions 2 NUT 1996 (2,2) NUT2000A (2,2) and NUT2KXYS (3,2) 2 NUT PART (2,2) NUT2000P (2,2) and NUT2KXYP (2,2) 2 CF2J2000 (3,3,3) CF2J2K (3,3,3) ********************************************************************************* New CORFxx file for Calc 10: 1000 Section 20 1 cable CABL DEL CBL STAT 1 -1 2 pcal rmv UNPHASCL -1 -1 3 Nieltdry NDRYCONT 1 1 4 Nieltwet NWETCONT 1 1 5 user cal 6 WVR WVRDELAY WVR STAT -1 1 1000 Section 21 1 cable 1000 Section 30 1 WVR @ zenith WVR DELY 1000 Section 40 1 Pol Tide PTD CONT 2 WobXCont WOBXCONT 3 WobYCont WOBYCONT 4 EarthTid ETD CONT 5 Ocean OCE CONT 6 PTideOld PTOLDCON 7 UT1Ortho UT1ORTHO 8 XpYpOrth WOBORTHO 9 XpYpNutn WOBNUTAT 10 Feed Rot FEED.COR 11 Wahr Nut WAHRCONT 12 TiltRmvr TILTRMVR 1000 Section 41 1 Pol_Tide 2 WobXCont 3 WobYCont 4 EarthTid 5 Ocean 6 Feed Rot 1000 Section 42 1 Pol Tide 2 WobXCont 3 WobYCont 4 EarthTid 1000 Section 50 1 SourStru SOURSTRU 2 SpurPcal SPURPCAL 3 UserMcal USERMCAL 1000 Section 51 1 UserMcal