LBA Calibrator Survey

LBA Calibrator Survey (LCS)

Objectives of the campaign
People
Previous Observations
Proposed Observations
List of candidates
Current status
Mailing list

Objectives of the campaign

The goal of the project is to observe at 8.4 GHz a list of candidate flat spectrum radio sources with declination < -50° with using the Australian LBA instgrument and to 1) determine their postiion with milliarcsec accurady; 2) measure their correlated flux density; 3) detrmine their suitability as calibrators for phase referencing observations and as target for astrometry and geodesy observations.

Preliminary results

Preliminary results of these campaign are accessible here.

Experiment v254b

Experiment v271a

People

Team members (in alphabetic order):

Alessandra Bertarini Max Planck Inst. fuer Radioastronomie, Bonn, Germany
Roy Booth Hartebeesthoek Radio Astronomical Observatory, South Africa
Sarah Burke-Spolaor Swinburne University of Technology, Australia
Ed Fomalont National Radio Astronomy Observatory, USA
Ron Ekers Australia Telescope National Facility, Australia
Kee-Tae Kim Korea Astronomy & Space Science Institute, South Korea
Tara Murphy University of Sydney, Australia
Leonid Petrov NVI, Inc./NASA GSFC, USA
Chris Phillips Australia Telescope National Facility, Australia
Sergei Pogrebenko Joint Institute for Very Long Baseline Interferometry in Europe
Elaine Sadler University of Sydney, Australia
Anastasios Tzioumis Australia Telescope National Facility, Australia

Previous Observations

On 2007.06.24_12:00 a 12 hour K-band experiment v230 with ATCA-104, CEDUNA, MOPRA, PARKES, HARTRAO HOBART26, SESHAN25 was observed. The primary goal of the experiment was to derive coordinates of stations ATCA-104, CEDUNA, MOPRA with centimeter accuracy. The secondary goal of the project was to check feasibility of running global astrometry experiments with the LBADR backend.

Five sources, never previously observed with the VLBA, were added to the schedule, two scans per source. All of them have been detected. Their positions were determined with 2–5 mas accuracies. More details can be found here. This experiment has proved the concept.
More details about the v230 experiment can be found here.

Proposed Observations

We request two 24 hour observing sessions at ATCA, Ceduna, Mopra, Hobart, Parkes, Hartrao (and Tidbinbilla if available) for running X-band observations to determine coordinates at a milliarcsec accuracy level for ~400 flat-spectrum sources in the declination zone [-50°, -90°]. We will also produce estimates of correlated flux density and source structure. The output catalogue of source positions will be of use for phase-referencing observations at the LBA, as a calibrator pool for the ATCA, ALMA, and SKA, for space navigation, and as a source list for geodetic observations. Considering success rate of 75 %, the pool of known southern calibrators is expected to increase by a factor of 4.

Full text of the proposal for observations in 2008.

Full text of the proposal for future observations in 2009.

The list of 203 candidates was generated on a basis of the preliminary results at20g catalogue. They were selected on the basis of their spectra: the sources with projected correlated flux density > 200 mJy and with the spectral index flatter than -0.6 were selected.

Current status

2008.12.15 The table of preliminary estimates of correlated flux densities of observed sources were produced.

2008.12.15 Estimates of SEFD in v254b and v271a experiments were produced from amplitude analysis.

2008.12.14 The second proposal has been submitted to the observing programming committee.

2008.12.07 The catalogue of positions of 243 target sources is prepared.
The catalogue is accessible here.

2008.12.05 Experiment v271a was correlated and analyzed.
More information about v271a experiment is accessible here.

2008.11.20 Schedule of experiment 271b is prepared. Observing time for v271b experiment is alloted:
[2008.11.28_09:00:00, 2008.11.29_09:00:00]. Schedule files is available: v271b.vex, v271b.plan, v271b.stat, v271b.skd, v271b.skf

94 target sources (66 sources scheduled in 4 scans, 28 in 3 scans) and 47 troposphere calibrator sources are scheduled.

Other resources:

LBA v271b Wiki page

LBA v271b ftp directory

2008.10.23 Preliminary partial correlation of v271a experiment (4 stations only).

Statistics:

 Correlated:                                            1564 
 Number of potentially recoverable observations:        1222            
 Number of potentially good observations with QC 5-9:   1223            
 Number of used observations:                           1159  ( 94.84%) 

 Quick look at v271a
  
 127 scheduled
 126 observed
 118 detected

Detection rate is 93%. Resolving ambiguities was a bigger problem for this
experiment, but it went through. It is difficult to tell anything about
astrometric quality, since two few baselines were processed.

2008.08.13 Correlation of v254b experiment is finished. The correlator output is available here. Weather, Tsys and uvflag data:

Station Weather data Tsys data UV flag

ATCA-104 v254b_at.tsys+weather v254b_at.tsys+weather n/a

CEDUNA v254bcd.log v254bcd.log v254bcd.uvflg

HOBART26 v254bho.log v254bho.log v254b_ho.uvflg

MOPRA v254b_mo.tsys+weather v254b_mo.tsys v254b_mo.uvflg

PARKES v254b_pa.weather n/a n/a

The second preliminary catalogue of source positions was derived from data analysis of the experiment. The catalogue is available here.

2008.08.10_00:00 24 hour VLBI experiment v271a ran at ATCA-104, CEDUNA, DSS45, HARTRAO, HOBART26, MOPRA, PARKES 127 targeted sources and 49 tropospheric calibrators were scheduled.

2008.07.25 A part of v254b experiment was correlated, the output of the correlator was made accessible, and preliminary results were produced. Among 123 scheduled sources, all 123 were observed and 121 were detected. The success rate is 98.4% — the world record!! Group deal delay solution has fit 42 psec with 2.4% outliers. Group delay ambiguities with spacing 3.9 ns (another world record!) were successfully resolved. Very preliminary catalogue of source positions is available here . The listing of the solution is accessible here .

Problem: Clock stability of CEDUNA was low. Plots of residuals + estimates of clock for all baselines and for the Ceduna/Mopra baseline illustrate the problem.

Fringe plots of several strong SNR scans at ATCA-104/CEDUNA, ATCA-104/PARKES, CEDUNA/PARKES baselines

Scan No00140 fringe plot at AC fringe plot at AP fringe plot at CP

Scan No00264 fringe plot at AC fringe plot at AP fringe plot at CP

Scan No00270 fringe plot at AC fringe plot at AP fringe plot at CP

2008.02.07 A favorite response on V271 proposal "LBA Calibrator Survey" the Time Allocation Committee was received.

2008.02.05_04:00 24 hour VLBI experiment v254b ran at ATCA-104, CEDUNA, MOPRA, HOBART26, PARKES. 123 targeted sources and 43 tropospheric calibrators were scheduled. As of 2008.06.18, the data are being transferred to Bonn for correlation.

2007.12.20 The proposal has been submitted. The proposal was assigned number v271.

2007.06.24 The pilot project, 12 hours K-band geodetic experiment was observed at ATCA-104, CEDUNA, HARTRAO, HOBART25, MOPRA, PARKES, SESHAN25. Positions of ATCA-104, CEDUNA, MOPRA were determined with a 1–3 cm level of accuracy. Coordinates of 5 new sources never observed before with VLBI were determined with accuracy of 2–5 mas. K-band correlated flux density of 59 sources were determined. More details can be found here.

Mailing list

is for discussing issues related to the LCS experiments. Only subscribers can post messages to the list. The messages posted to the list are available for viewing to all from the mail archive.

Back to VLBA Calibrator Survey web page.
This page was prepared by Leonid Petrov ()
Last update: 2008.12.15_22:17:16

Station	Weather data	Tsys data	UV flag
ATCA-104	v254b_at.tsys+weather	v254b_at.tsys+weather	n/a
CEDUNA	v254bcd.log	v254bcd.log	v254bcd.uvflg
HOBART26	v254bho.log	v254bho.log	v254b_ho.uvflg
MOPRA	v254b_mo.tsys+weather	v254b_mo.tsys	v254b_mo.uvflg
PARKES	v254b_pa.weather	n/a	n/a

Scan No00140	fringe plot at AC	fringe plot at AP	fringe plot at CP
Scan No00264	fringe plot at AC	fringe plot at AP	fringe plot at CP
Scan No00270	fringe plot at AC	fringe plot at AP	fringe plot at CP