Summary
 

Observation code	:	VS07k		AIPS Version	:	15OCT99
Date of Observation	:	1999/127		Difmap Version	:	Not used
Source Name	:	J0958+47		vsop_difmap used	:	No
Calibration Source(s)	:	0923+392
Ground telescopes	:	NRAO_140, NOTO		Model Fitted to data	:	No
Tracking Station(s)	:	GZ, TZ		Image made	:	No
Correlator	:	Penticton

 

Abstract 1. Removed delay and rate offset from original data. Values from both tracking passes about the same: -250 nsec and -2 mHz. 2. Flagged all Torun data. 3. Used nominal gain values for VSOP, GB and NT. Used measured Tsys for GB and NT. See ANTAB.TXT. However, these values did not give expected flux density levels. More of this below 4. Fringe fitting of 16-ch, 2-sec data was excellent. After minor editing, good results obtained with 2-min integrations using FRING. 5. Here is the amplitude problem: SOURCE Expected Correlated Flux Density at 100 Mlambda NT - GB baseline VLBA obs These Observ 0923+392 11 Jy 2.4 Jy J0958+47 1.6 Ju 0.3 Jy In otherwords, the correlated flux density on the ground baseline is about 20% of that expected. Both sources have not varied much over the last few years. Since there is only one ground baseline, it is difficult to determine how to fix the ground antenna gains. The adhoc values of NRAO_140 x 2.5 NOTO x 1.5 gives somewhat consistent results, including the HALCA baselines. 6. The calibrated data base contains the above adhoc gain corrections to NRAO_140 and NOTO. No changes made to HALCA Parameters. 7. In view of the uncertain gain calibration, no difmaping and modeling was done. I think the amplitude versus u-v plots is probably okay for statistical purposes.

AIPS Input Files

ANTAB.TXT

Comments NRAO_140 gain values not available. George calculated it for me.

Additional Files

Name	Description
AMP_CAL	This plot comes directly from the aplication of ANTAB.TXT. Both IF's are identical. This is being shown since there appears to be a gain calibration error for ant 2 and 4.
SN_CAL_DEL1	Antenna 4 (NRAO_140) is the reference. Plotted are residual fringe fits for VSOP_SC and NOTO. Two minute integrations were used and, with some spotty editing, nice results were obtained. Some comments are: (1) The jump in the NOTO SNR is strange. Perhaps, it is related to the incorrect gain calibration. (2). The 30 nsec jumps in ante 1 and 2 occur in both IF's with good SNR, so they have been left and calibrated out.
SN_CAL_DEL2	see above
SN_CAL_RAT_1	see above
SN_CAL_RAT_2	see above
SN_PHAS	see above
SN_CAL_SNR1	see above
SN_CAL_SNR2	see above
UV0923+392	Correlated flux density of 0923+292. It is 2.4 Jy. It should have been at 100 mLambda, about 11 Jy, based on the VLA data base and the VLBA observations. For J0958, all baselines are shown in the figure. The heavy dots at 100 Mlambda are for the NOTO-GB baseline and is 0.3 Jy. According to the VLBA image, this source was slightly resolved with a flux density of 1.5 Jy. Baseline VSOP-NOTO has the higher flux density than the Baseline VSOP-GB. Since these two u-v tracks are similar, one suspects that the GB gain is more in error than the NOTO gain.
UV0948+47	see above
0927+390.ps	The VLBA pre-launch results indicating that the flux density derived in this survey experiment is too low.
0958+472.ps	see above
UVCOR_J0958+47	Here is the correlated visibility with baseline for the source, after the adhoc gain corrections. The flux density of 0923+392 is now about 10 Jy which is okay.
TASAV.FITS	Description of the tables used. SN1: Contains the apriori gain values from ANTAB.TXT (GC1 and TY1) CL2: CLCAL of CL1 + SN1 using 2PT FG1: The flag file. Mostly flagging out Torun and and little of the other telescopes to get nice continuity SN2: The FRING results. 2-min integration CL3: CLCAL of CL2 + SN2 using 2PT CL4: CLCOR ANT 2 gain bumped by 1.5; ANT 4 gain bumped by 2.5 (adhoc)
J0958+47_FOMALONT_AIPS.FITS	J0958+47 file is split data using CL4 above. It is then average to 30-second sampling. J0923+392 is the bit of data after the calibration. Only baseline NOTO-NRAO_140 is available.
0923+392_FOMALONT_AIPS.FITS	see above

AIPS Output Files

PRTAN.LIS LISTR.LIS UVPLT_UV.PS

UVPLT_UVD.PS UVPLT_UVPA.P WEIGHTS.PS