Introduction

Background

• RL fringes were found at all baselines, and the fringe amplitude for RL scans was at the level 0.08-0.20 of the fringe amplitude for RR scans. It means that the effect of polarization impurity in normal RR scans is at the level 0.01-0.04, roughly 10 times smaller than in RL scans.
  
  
• Individual fringe amplitudes vary up to 3 times within the band of registration (360MHz at X-band and 80MHz at S-band)
  
  
• Bandwidth synthesis for RL scans at X-band failed: residual phases scattered up to 2 radians. Bandwidth synthesis for RL scans at S-band was poor: residual phases scattered up to 0.5 radians. The ratio of residual phase scattering at X-band and S-band is 4. This ratio is about the ratio of frequencies - 8.2/2.2 . It is an indication that the effect which caused phase scattering is a path-like but not phase-like.
  
  

• Almost all stations have instrumental polarization exceeding 1% and some stations have instrumental polarization exceeding 10%.
  
• Instruments polarization is depends on time relatively weak, but may change after any manipulation with appliances.
  
• Instrumental polarization shows strong frequency dependence at many stations. Dependence of instrumental polarization on frequency has quasi-sinusoidal modulation with periods about the physical scales of the antenna: tens MHz.
  

Motivation

Objectives

• To measure polarization impurity on stations participating in the experiment.
• To investigate dependence of instrumental polarization on
  • time
  • frequency
  • parallactic angle
• To investigate how residual phases depend on
  • time
  • frequency
  • parallactic angle
• To determine relative jumps in group and phase delays for RR and RL scans.
• To make phase connection of RR and RL scans.
• To investigate misclosure for RR and RL scans for
  • group delays
  • multiband fringe phases
  • individual phases

Schedule

Stations

Sources

|--------------------|----------------|--------------|--------------|
| IAU name   name    | 8.0GHz  4.8GHz | 6cm    15cm  | P-8.0  P-4.8 |
|  (1)       (2)     | (3)     (4)    | (5)    (6)   | (7)    (8)   |
|--------------------|----------------|--------------|--------------|
| 0316+413   3C84    | 21.15   21.35  | 18.72  24.80 |  0.14  0.25  |
| 0538+498   3C147   |  4.64    7.92  |  8.18  12.98 |  0.10  0.21  |
| 0552+398   DA193   |  5.77    5.74  |  5.43   3.40 |  2.22  0.87  |
| 0923+392   4C39.25 | 10.64   12.53  |  7.57   4.20 |  1.09  1.08  |
| 1226+023   3C273B  | 38.84   43.27  | 43.41  41.44 |  3.59  3.67  |
| 1253-055   3C279   | 24.83   17.82  | 15.34  11.80 |  2.23  3.93  |
| 1641+399   3C345   |  8.53    8.37  |  5.65   7.60 |  3.51  3.01  |
| 1921-293   OV-236  | 11.67   14.43  | 10.00   4.60 |  3.00  1.04  |
| 2134+004   2134+00 |  8.80    8.52  | 11.49   6.50 |  1.92  0.30  |
| 2251+158   3C454.3 | 11.78   12.92  | 10.03  10.50 |  1.37  2.57  |
|--------------------|----------------|--------------|--------------|

Frequencies

Observing scenarios

• Scenario a ("band scan")
  A pair of sources: 0316+413, 0923+392 is observed from 182.10:00 till 182.12:15 and a pair of sources: 0923+392, 2251+158 is observed from 183.07:20 183.09:43. First two scans are made in RR then two scans in RL, then frequencies of individual videoconverters are changed. Frequencies are changed 6 times by adding an offset to all frequencies of videoconverters with respect to initial (default) setup each time. Sequence of offsets at X-band is -2, -3, -5, +3, +6, +8 MHz and -1, -4, -6, -10, -15, -21 MHz at S-band. Restriction: a) the frequencies of the individual vcs should not cross the boundary 224MHz of local oscillator: 8304 = 8080 + 224MHz and 2244 = 2020 + 224MHz in order not to change their setup: upper or lower was taken into account; b) the frequencies of the individual vcs should not exceed 499 MHz.



• Scenario b ("pair connection")
  A pair of sources is observed. Two observations in RR and two observations in RL. Then the procedure is repeated. Pair 1226+023, 1253-055 is observed at 182.12:44 -- 182.14:00 and at 182.16:44 182.17:33. Pair 0538+508, 0552+398 is observed between 182.14:06 and 182.16:44



• Scenario c ("stay on source")
  One source is observed, but polarization is swapped after each scan. 1253-055 is observed at the baseline MEDICINA/MATERA from 182.17:33 till 182.20:00 while WETTZELL is engaged for NEOS Intensive and temporarily does not observe BRD01.



• Scenario d ("full coverage")
  All visible sources are observed during 2-3 hours, in normal geodetic fashion to achieve full sky coverage, but polarization setup is not changed during that period. Then polarization is swapped and again 2-3 hours of observations. RR: 182.20:04 182.23:11, RL: 182.23:11 183.02:04 RR: 183.02:04 183.04:05, RL: 183.04:05 183.07:17

Comments:

Predicted SNR

Average predicted SNR at the baseline TIGOWTZL/WETTZELL over all observations:

Schedule (skd-file)

Schedule summary

Schedule for change of polarization setup for MEDICINA

This page was prepared by Leonid Petrov.
Web-master: petrov@kuestner.geod.uni-bonn.de

Last update: 22-JUN-99 14:13:12