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Contents

Index

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Preface
this Guide
Conventions

/1./	The Australia Telescope Compact Array
/1.1/	The Australia Telescope National Facility
/1.2/	Overview of the ATCA
/1.3/	Centimetre Observations (16–3 cm bands)
/1.4/	Millimetre-wave observations (15mm–3mm)
/1.5/	Choosing an Observing Frequency
/1.6/	Choosing Angular and Frequency Resolution
/1.7/	Additional Observing Notes and Techniques
/1.8/	High Time Resolution, Pulsars, Planets and VLBI
/1.9/	Other Things to Consider
/1.10/	Submitting a proposal
/1.11/	Successful Proposals

/2./	Preparing for Observations
/2.1/	Scheduling Strategy
/2.2/	Calibration Requirements
/2.3/	How to Prepare a Schedule File
/2.4/	How to Prepare a Mosaic File
/2.5/	Observation Requirements
/2.6/	Pre-observation Checklist

/3./	Observing
/3.1/	Changeover
/3.2/	Setting up
/3.3/	Observing
/3.4/	Troubleshooting
/3.5/	cm Observing Startup Checklist
/3.6/	mm Observing Startup Checklist

/4./	After your Observations
/4.1/	Archiving Your Data
/4.2/	Report Your Experiences
/4.3/	Data Analysis
/4.4/	Publishing Results

/A./	caobs reference
/A.1/	Using caobs

/B./	cacor reference
/B.1/	Cacor Status Panel
/B.2/	Cacor Data Panel
/B.3/	Cacor Timing Panel
/B.4/	Cacor Log Panel
/B.5/	Cacor Command Panel
/B.6/	Cacor Commands

/C./	SPD reference
/C.1/	Introduction to SPD
/C.2/	SPD Commands

/D./	vis
/D.1/	VIS Commands

/E./	Web Scheduler
/E.1/	Scheduler Fields
/E.2/	Scheduler Actions

/F./	Observatory Coordinates
/F.1/	Site Location
/F.2/	Station Locations

/G./	ATCA Configurations
/G.1/	Array Configurations
/G.2/	Shadowing Diagrams

/H./	People to contact

Index

[Printable Guide] [Printable Chapter]

2.3 How to Prepare a Schedule File

2.3.1 Introduction
2.3.2 How to Use the Web Scheduler
2.3.3 Web Scheduler Examples

2.3.1 Introduction

Observations on the compact array normally consist of a sequence of scans: a scan is a short period of observing where a single source is observed. A complete observation is made up of a number of scans. Observations typically alternate between program source scans and calibrator scans. Details of scans are kept in a schedule file.

The main observing task, CAOBS, reads the schedule file in order to determine what sources are to be observed, for how long, and in what order. The schedule file also defines the frequencies, integration averaging unit and correlator setup to use.

The ATCA web scheduler (http://www.narrabri.atnf.csiro.au/observing/sched/cabb/), is the tool to use to create ATCA schedule files in the CABB era. Schedules made with the old SCHED program are no longer understood by the CABB version of CAOBS and thus cannot be used. However, it is possible for the web scheduler to read in old schedules and save them for use with the new system. Please also note that an active ATNF username and password is required to gain access to the web scheduler page.

You should prepare at least two schedule files:

• A schedule file for setting up and primary flux calibration. It should include 1934-638 and, if 1934-638 will not be up when the observations start, another setup calibrator. If the observations are at mm wavelengths, the primary flux calibrator may be a planet, which is unsuitable for array setup. It is also advisable to observe a bandpass calibrator at the start of observing.
• A schedule file containing the program source(s) and phase calibrator(s), and perhaps contingency schedule files in case the preferred frequency is seriously affected by interference, or the selected calibrator proves to be resolved.

For observations of many sources, use the ATMOS program in MIRIAD to solve the “travelling salesman” problem and optimise the order in which the sources are observed.

With synthesis instruments, it is possible for system errors to lead to artefacts at the centre of the field. For experiments that are intolerant to such artefacts (such as detection experiments), displace the source position a few synthesised beamwidths from the field centre. Note that ATCA software never checks to see how close the telescope is pointing to the sun!

2.3.1.1 Source Rising and Setting Times
2.3.1.2 Antenna Wrap Limits

2.3.1.1 Source Rising and Setting Times

COORD is a useful program that calculates the altitude, azimuth, and rising and setting times of sources. Currently, this is most easily accessed via the Parkes website, http://www.parkes.atnf.csiro.au/cgi-bin/utilities/coord.cgi (though be sure to change from the default values when using the ATCA, i.e., change the site to Australia Telescope Compact Array, and change the elevation limit to 12 degrees for cm observing).

A quick estimate of how long a particular source will be observable for on the ATCA can be made with the table below. It shows, for a source at a particular declination, the LST range before/past zenith it is above 20^\circ elevation. For example, for a source with coordinates RA=08:25:26.869, Dec=-50:10:38.4 (the coordinates for 0823-500), its rise time will be 02:03 LST (take 06:22 from 08:25), and its set time will be 14:47 LST (add 06:22 to 08:25).

Table 2.1: For sources at particular declinations, this table displays the amount of time the source would take to get from rise to transit, or from transit to set at the ATCA. For these numbers, a source is considered set if it is below 20^\circ elevation.

2.3.1.2 Antenna Wrap Limits

Figure 2.1: Wrap limits for the Compact Array and Mopra antenna.

The wrap limits for any antenna in the ATCA are CCW=152.5^\circ and CW=327.5^\circ as shown in Figure wraplimits.

2.3.2 How to Use the Web Scheduler

The CABB web scheduler, located at http://www.narrabri.atnf.csiro.au/observing/sched/cabb/ is used to prepare schedule files. The web scheduler checks the schedule for completeness and, where possible, checks choices such as observing frequency for hardware compatibility. Drive times, and source azimuths and elevations are computed automatically.

Three steps are involved in using the web scheduler:

• A new scan is added to the schedule.
• The details of the scan are changed as desired.
• When all the scans have been defined, the entire schedule is written to file

When constructing a schedule, consider:

• Is the sequence of sources sensible, and how much time is expended on the drive times?
• Does the schedule contain all the sources, and at the appropriate frequencies and bandwidths?

The web scheduler can produce a list to help answer these questions. It is a good idea to study these listings very carefully before observing commences. The scheduler considers drive times: all coordinate entries are automatically followed by a calculation of the azimuth and elevation of the source, as well as the drive time from the previous source, using the entered value for LST. When entering a schedule file, the integration times are specified for each source (and calibrator source). Note that, except in the case of mosaic schedules and DWELL scantypes, these integration times include drive times, so the specified time must be somewhat longer than the amount of integration on source required. This is particularly important for secondary calibrators, when the drive time (up to a minute or so) may be comparable to the integration time (about two to three minutes). Alternatively, the sctype field can be set to DWELL to ensure a source or calibrator is tracked for the specified scan duration.

The schedule file submitted to CAOBS (the online Compact Array control task) need have no specific start time. Rather, the schedule file asks CAOBS to start the first scan as soon as possible. The sequence of scans will be exactly as specified in the schedule file. However, when using the web scheduler, the calculation of azimuths, elevations and drive times is possible only if the starting sidereal time is known (at least approximately). The sidereal time for the first scan in the schedule can be set in the web scheduler by giving the time in the Time field, and setting TimeCode to LST. Alternatively, the starting UT may be specified by setting TimeCode to UT, and by setting the Date to the appropriate start date by clicking on it and using the calendar that appears. Note that when viewing any scan other than the first in the schedule, the fields Time, TimeCode and Date all become read-only.

The environment flag can be used to instruct the online software to remember certain settings, such as attenuators, and to recall them whenever a scan with the same environment flag is encountered. However, this is generally not required, as the online software will remember user settings, and recall them when the same conditions are encountered again. There are at least 128 slots for user settings, so for a normal schedule, the environment flag will probably not need to be used.

2.3.3 Web Scheduler Examples

The following sections will describe how to make schedules, by illustrating a number of examples. A complete technical guide to the operation of the CABB web scheduler can be found in Appendix Web Scheduler.

2.3.3.1 Continuum Schedule Example
2.3.3.2 Zoom Mode Schedule Example

2.3.3.1 Continuum Schedule Example

In this section a simple continuum schedule file is constructed. It will contain three sources: a program source and two calibration sources. The following observing sequence will be specified:

• setup calibrator (0537-441, a catalogued source) for 5 minutes,
• program source (R.A. 05:21:35.5, Dec. -21:24:27.1 (J2000)) for 30 mins,
• a phase calibrator for 5 minutes.

These sources will be observed at the standard C/X band frequencies of 5500/9000 MHz. To create this schedule file, perform the following steps:

Navigate to http://www.narrabri.atnf.csiro.au/observing/sched/cabb/ in a web browser

The first screen is displayed.

Change the Source field to test

Change the RA field to 05:21:35.5 and the Dec field to -21:24:27.1

The delimiter for coordinates must be a colon, and the default Epoch of J2000 should only be changed if necessary.

Change ScanLength to 00:30:00

Change ScanType to Dwell

This ensures that 30 minutes are spent on source, regardless of slewing times.

Ensure Pointing is set to Global

Offset pointing is usually not required for low-frequency observations.

Change the Observer field to Jansky, the Project code to C123

These fields should be set in the first source - they will propagate to the other sources as they are added

Change the Time field to 02:00:00, and the TimeCode field to LST

This indicates that the schedule will be started at an LST of 2h

Click the Freq1 Setup bar

This brings up the frequency selection fields

Enter 5500 in the Continuum frequency box, and keep the Chn. BW selection box to 1 MHz.

The velocity resolution should be calculated to be 54 km/s, and the velocity range will be 111631 km/s

Click the Freq2 Setup bar

This brings up the frequency selection fields

Enter 9000 in the Continuum frequency box, and keep the Chn. BW selection box to 1 MHz.

The velocity resolution should be calculated to be 33 km/s, and the velocity range will be 68219 km/s.

Click the Scan Parameters bar

This brings up the scan details

Click the Search Cal button

This presents a list of nearby calibrators to the right of the scan details, sorted by distance to the source. The closest strong (> 1 Jy) source to the program source is shown to be 0511-220.

Click on the 0511-220 button

The details for this source are displayed from the calibrator database below the source list. This source is a suitable phase calibrator as it is strong and has only a small defect.

Click on the 0511-220 button

Clicking on the button twice (without clicking another source button between clicks) inserts this source into the schedule above the currently selected source.

Select source 1, and change the ScanLength field to 00:05:00

To copy this source to the end of the schedule, click on the Edit menu and select Copy, then select the test source, click on Edit and select Paste.

The schedule should now have three sources (in order): 0511-220, test, 0511-220. The first source needs to be changed to 0537-441.

Select source 1

Change the Source field to 0537-441 and press TAB

The scheduler will automatically put the source coordinates for this known calibrator in the RA and Dec fields

Click on the File menu and select Save As

The Schedule file selector window will appear

The schedule will be called c123_test.sch, so enter this into the Filter box to ensure that there is not already a schedule with this name

If there is another schedule with the desired name, consider changing it

Enter c123_test.sch into the Schedule box and press the Save button

The file selection window will disappear, and the name of the schedule should now appear at the top of the window.

To produce a listing of the schedule, in order to check that the schedule proceeds as expected, click on the Listing tab.

2.3.3.2 Zoom Mode Schedule Example

This example adds to the example from the previous section; ensure that the schedule created in the previous section is in the scheduler before continuing.

Now the aim is to observe 1 zoom band in each IF, each covering at least 70 km/s. The galaxy “test” is actually at a barycentric recessional velocity of 25000 km/s, and these observations will look for CH_3OH methanol and HC_3N cyanoacetylene lines.

To create a schedule that can perform suitable observations for this situation, follow the steps:

Select the first scan in the schedule

This should be 0537-441.

Select the Global change menu item from the Tools menu

Change the Date of this scan to 30/11/2010

The date that the observation will be performed is required to ensure that the observatory velocity is computed correctly.

Hit the Global Apply button.

The date will now change for all the sources in the schedule.

Select the “test” source in the schedule

Click the Freq1 5500MHz bar

This brings up the IF1 frequency selection fields.

Click the topmost Velo button

This brings up the velocity calculator.

Select the CH3OH line from the Spectral Line dropdown box.

The rest frequency of this line (6668.518) appears in the Rest Frequency box below.

Enter 25000 in the Source Velocity field, and select Bary for the velocity frame, and Radio for the velocity convention.

The Sky Frequency will be updated to 6112.490 MHz, and the zoom band frequency will be calculated as the nearest half-MHz, in this case as 6112.5.

Select the Fix checkbox

This signifies that this galaxy is at 25000 km/s. Other lines in other zoom bands will now automatically be shifted by the same velocity.

Click the Apply button in the velocity calculator.

The velocity calculator will disappear and information will be inserted into the first zoom band. In this case, the 6112.5 MHz frequency translates into the channel 3274. The velocity resolution is given as 0.024 km/s, and the velocity range is listed as 49 km/s.

Select the zoom band width to be 2 from the width drop box.

The velocity range now increases to 73.6 km/s.

Click the Freq2 9000MHz bar

This brings up the IF2 frequency selection fields.

Click the topmost Velo button

This brings up the velocity calculator. Note that the velocity field has already been filled out and cannot be altered.

Select the HC3N line from the Spectral Line dropdown box.

The rest frequency of this line (9009.833) appears in the Rest Frequency box below, and the Sky Frequency will be updated to 8258.584 MHz. The zoom band frequency will be calculated to be 8258.5.

Click the Apply button in the velocity calculator.

The velocity calculator will disappear and information will be inserted into the first zoom band. In this case, the 8258.5 MHz frequency translates into the channel 566. The velocity resolution is given as 0.018 km/s, and the velocity range is listed as 36.3 km/s.

Select the zoom band width to be 3 from the width drop box.

The velocity range now increases to 72.6 km/s, comparable to the width provided for the IF1 zoom band.

Click the Scan Parameters bar

This brings up the scan details.

Select the Advanced view menu item from the Tools menu.

This displays the advanced settings for this scan.

Select the Master1 option from the FreqConfig dropdown box.

This signifies that the frequency configuration, including the zoom modes, from this scan, should be defined as the master configuration.

Select the 0537-441 source from the schedule.

Select the Slave-1 option from the FreqConfig dropdown box.

Now this scan will exactly mirror the frequency and zoom mode configuration from the test scan, even if the configuration of the test scan is changed. When a scan is set as a slave scan, the Freq panels will display a message describing which frequency and scan it is slaved to.

Select the 0511-220 source from the schedule.

Select the Slave-1 option from the FreqConfig dropdown box.

Now this scan will exactly mirror the frequency and zoom mode configuration from the test scan.

At this point, the schedule would correctly describe a zoom mode observation.

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Users Guide last modified on 2011-04-27 15:49:06