08 July 2000 - Gain Curve Calibration K Band Status Steven T. Myers 12 September 2000 ------------------------------------------------------------------------------- Previous Gain Curves - April 15/16, 1999 ELINT Data For AN 1-20,22-28 (tau=0.032); data from Feb98 for AN21 Antenna 21 is OUT. Elevations 28 to 82 deg. ------------------------------------------------------------------------------- Current Data: Summary of Run - Q Band tau=0.21 from tipper data data quality poor to fair K-band pointing suspect due to high water column 27 antennas available, AN 11 out of array Poor data on AN 3,7,8,10,14,15,17,24 Probably unusable data on AN 1,20,28 Unusable data on AN 19,21,23 AN 1 poor - data poorly fit by parabola - UNTRUSTWORTHY -> USE APR99 CURVE note: curve max at EL>72 AN 2 fair - poor fit to parabola at EL<30 note: curve max at EL>72 AN 3 poor - noisy, poor fit at EL<30 AN 4 good AN 5 fair AN 6 fair - noisy, poor pointing? AN 7 poor - noisy, bad pointing AN 8 poor - noisy, bad pointing AN 9 fair AN 10 poor - insufficient EL range, need EL<34 data AN 11 missing from array - USE APR99 CURVE INTERIM AN 12 good note: curve max at EL=32 AN 13 fair AN 14 poor - poor fit, noisy, bad pointing? AN 15 poor - noisy, bad pointing note: curve max at EL=60? AN 16 fair AN 17 poor - noisy at low EL AN 18 fair note: curve max at EL>72 AN 19 poor - noisy, no sign of gain curve at all! - USELESS -> APR99 DATA AN 20 poor - very noisy, bad pointing, and poor fit - PROBABLY USELESS AN 21 poor - noisy, insufficient EL range, inverted curves - USELESS -> USE FEB98 CURVE, NO APR99 DATA AN 22 fair AN 23 poor - insufficient EL range, inverted curves - USELESS -> APR99 DATA AN 24 poor - bad data at key elevations, poor fit AN 25 fair - missing data at EL<28 AN 26 fair - noisy AN 27 fair AN 28 poor - very noisy, bad pointing, and poor fit - PROBABLY USELESS ------------------------------------------------------------------------------- Results can be found at http://www.aoc.nrao.edu/~smyers/calibration/Gains/ Contents: K-Apr99.elint ELINT output final K band from April 1999 K-Jul00.elint ELINT output final K band from July 2000 K-Jul00.elint.run0.ps.gz plots for raw unedited data K-Jul00.elint.ps.gz plots for final edited data ABSKGAIN-JUL00.001 Jul00: CLCOR Procedure, absolute calibration FIXKGAIN-JUL00.001 Jul00: CLCOR Procedure, gain normalized FIXKGAIN-APR99.001 Apr99: CLCOR Procedure, gain normalized FIXKGAIN.001 AIPS procedure to run CLCOR, best data K-08Jul00.status this file gainextract.pl perl script to extract curves from ELINT out gainplot.sm sm macro to plot gain curves The useful file FIXKGAIN.001 as well as the plot K-Jul00.elint.ps.gz are linked to the calibration page http://www.aoc.nrao.edu/~smyers/calibration/index.html and the gain curve page http://www.aoc.nrao.edu/~smyers/calibration/Gains/index.html The curves in FIXKGAIN.001 use Jul00 for most, except for Apr99 curves for AN 11,19,23 and Feb98 curve for AN 21. The Jul00 curves for AN 20,28 were retained, though poor, as the ones from Apr99 seemed less likely. ------------------------------------------------------------------------------- Suggestions for Next Calibration Run: The K-band data was particularly plagued by the high water vapor column (tau=0.21) which threw off the pointing for certain antennas on a number of scans. Unfortunately, instead of using the primary pointing from X-band as is normal, we elected to try secondary pointing at Q and K and got burned by the atmosphere at K (the Q band pointing seemed reasonable). We have obtained only very poor curves for AN 1,19,20,21,23,28, poor data at best for AN 3,7,8,10,14,15,17,24, and none on AN 11. We reverted to the Apr99 curves for AN 1,11,19,23 and Feb98 curve for AN 21, and made do with the rest. Furthermore, this run did not go to high enough elevation, and some of the antennas did not have data at low elevations (they were out of the array then). I suggest that we conduct another full gain curve run in the early winter - late November or early December - when the weather improves. Although the array will be in A configuration, the improved weather should offset any problems this will cause. In addition, we would have data for any new receivers added in the fall. Note that getting reliable gain curves is sufficiently important for observers at Q and K bands that it is worthwhile to devote suffient time to track the calibrator through the full elevation range (as well as possibly going "over the top"). Also, I would plan to include U band in the schedule to make sure we have updated gains there also. It would be good to not schedule this shoe-horned on a maintenance day as this often means that some antennas are missing (especially from the beginning of the run). This was a problem this time around in particular. -Steven Myers -------------------------------------------------------------------------------