; OBTAB ;--------------------------------------------------------------- ;! Recalculate orbit parameters and other spacecraft info ;# TASK Coordinates Table ;----------------------------------------------------------------------- ;; Copyright (C) 1998 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- ;--------------------------------------------------------------- OBTAB LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC OBTAB Task to calculate various orbital information INNAME Input UV file name (name) INCLASS Input UV file name (class) INSEQ 0.0 9999.0 Input UV file name (seq. #) INDISK 0.0 9.0 Input UV file disk unit # INVERS 0.0 9999.0 Input OB table version 0 => last SUBARRAY Subarray number; 0 => 1 ANTENNAS List of antenna to update All 0 => update all antennae with mount type set to orbiting APARM Orbital parameters 1: semi-major axis in meters 2: eccentricity 3: inclination (deg) 4: RA of ascending node (deg) 5: argument of perigee (deg) 6: mean anomaly at 0h on the observing date (deg) APARM(1) < 6.37812E6 => calculate elements from OB table. ---------------------------------------------------------------- OBTAB Type: Task Use: Use OBTAB to add the orbital elements for orbiting antennae to an AN table. The elements may be supplied explicitly as APARMs or may be calculated automatically from an orbit (OB) table if one is present. The recommended method is to calculate the orbit from the OB table. If an OB table is used to calculate the orbital parameters then it will be assumed to correspond to a single orbiter and any blanked fields will be be filled with recalculated values. Adverbs: INNAME.....Input UV file name (name). Standard defaults. INCLASS....Input UV file name (class). Standard defaults. INSEQ......Input UV file name (seq. #). 0 => highest. INDISK.....Disk drive # of input UV file. 0 => any. INVERS.....Input OB table version; 0 => last SUBARRAY...Subarray number; 0 => 1 This denotes the AN table that will be updated. ANTENNAS...A list of antennas for which the orbital elements will be updated. The mount types for these antennae will be forced to "orbiting". If all of the entries are less than or equal to zero then the orbital elements will be updated for all antennae that already have a mount type of "orbiting". APARM......Orbital elements. 1: The semimajor axis of the orbit in meters. If this value is less than the equatorial radius of the earth then the elements will be calculated from the OB table. 2: The orbital eccentricity 3: The inclination of the orbit to the equator in degrees. 4: The right ascension of the ascending node in degrees. 5: The argument of perigee in degrees. 6: Mean anomaly at 0h on the observing date. ---------------------------------------------------------------- OBTAB: Task to calculate orbital parameters DOCUMENTER: Chris Flatters, NRAO RELATED PROGRAMS: UVPLT, VPLOT, SLIME PURPOSE OBTAB inserts the orbital elements of orbiting antennae into an AN table, allowing models to be plotted for baselines including orbiting antennae at times where there is no data. The normal mode of operation is to calculate the orbital elements using the Cartesian coordinates and velocity vector of the satellite given as a function of time in an OB table. If there is no OB table present then orbital elements may be supplied manually. OBTAB will update several antennae in one pass but will assume that all of the antennae being updated are aliases for a single orbiter. The user may supply a list of antenna numbers to update. If no list is supplied then all antennae that have a mount type of orbiting (MNTSTA=2) will be updated; this will not be what you want if there is more than one real orbiter. OB tables from the VLBA correlator are incomplete. Given an incomplete OB table, OBTAB will fill out the missing information. If the subarray number in the OB table is set to zero then it will be set to the SUBARRAY used by OBTAB. If the antenna number is zero in the OBTAB then it will be set to the first positive entry in ANTENNAS, if any, or the lowest numbered antenna with MNTSTA=2 if there is no positive element in ANTENNAS. Other missing information will be recalculated. Normally, entries from the OB table will only be used to calculate the orbital elements if there subarray number matches the subarray being processed and their antenna ID number corresponds to one of the antennae being processed but zero subarray and antenna entries are assumed to be "wildcards" that match any subarray or antenna. This has the consequence that orbital elements will be calculated incorrectly if an OB table contains data for more than one orbiter and has zero subarray or antenna entries. CURRENT PROBLEMS OBTAB is currently uses a better-safe-than-sorry approach to calculating eclipse parameters that results in it probably performing far more computations than it needs to. This makes it very slow. REFERENCES "Orbital Motion, 3rd Edn", A.E. Roy, Institute of Physics Press (1988). AIPS Memo Number 93, L. Kogan.