This is the Australia Telescope Compact Array (ATCA) sensitivity calculator, specifically built to give maximum assistance to users who may not be familiar with the capabilities of the telescope. It aims to guide users through the process of planning an optimal observation strategy, calculate the resulting expected sensitivity and present it in a friendly way.
The calculator that this page uses is identical to the traditional calculator page found here, so users who do not need the extra assistance may continue to use it.
This calculator should be treated as a questionaire. Each panel will ask a series of questions, and when enough valid information is entered, the next panel(s) will open. The panels can be manually opened or closed by clicking on the blue bars. The blue bars also show a summary of the settings made in each panel.
When enough valid information is given by the user, a "Calculate Sensitivity" button will appear in the "Calculation and Results" bar. Clicking this button will close all the panels and present the results.
Questions, comments and issues should be addressed to Jamie (dot) Stevens (at) csiro (dot) au.
Observing Frequency
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| Frequency (GHz) | ||
| Receiver Name | low | high |
| 16cm | 1.1 | 3.1 |
|---|---|---|
| 6cm | 4.4 | 6.7 |
| 4cm | 4.0 | 12.0 |
| 3cm | 8.0 | 10.0 |
| 15mm | 16.0 | 25.0 |
| 7mm | 30.0 | 50.0 |
| 3mm | 83.0 | 105.0 |
The ATCA receiver suite is able to cover the range of frequencies shown
in the table on the right.
The new, upgraded 4cm receivers have now been installed on the ATCA. The 6 and 3 cm bands are left here as options for old observations, but the 4cm band should be used for all future observations in this wavelength.
Please select your band of interest, by clicking on either the buttons below, or
the name of the receiver in the table to the right.
With CABB, the 2 GHz continuum band is always recorded. You must choose the centre
frequency of this continuum band.
In the band, the centre frequency must be between
and MHz. To obtain
the optimum continuum sensitivity, the recommended centre
MHz.
MHz
If you want the calculator to report the sensitivity of a zoom band placed at a particular frequency, please
enter this frequency here, otherwise leave blank.
MHz
MHz
Array Configuration
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The ATCA is periodically reconfigured to suit the requirements of the observers
using it. "Long" arrays, with large antenna separations, are useful for continuum studies
of compact sources where resolution is important, while "short" arrays are useful for
line studies, or when sensitivity to diffuse sources is required.
You can use this calculator to estimate the sensitivity in an array with a maximum
baseline that you choose. Note that this is not necessarily exactly what you would
get in a particular array configuration, which may have a different set of shorter
baselines.
As of February 2013, all six antennas are equipped with the 4cm production receivers. You
may, however, calculate the sensitivity for any number of 4cm receivers.
Correlator Configuration
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The frequency resolution of CABB's 2 GHz continuum band can be configured to
best suit the observation.
- For continuum observations, it is best to select the highest frequency resolution possible, which for CABB is 1 MHz.
- For spectral-line observations, you will generally want to use the correlator mode that will give you the optimum spectral coverage.
- The calculator allows both available and planned CABB modes to be selected: please check the CABB webpage for the modes that have been implemented.
Observation Details
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Please describe the observation you will make.
degrees
Specify the integration as the time spent on-source, excluding calibration overheads.
Depending on the calibration scheme used, these overheads might vary between 5% for
simple 16cm observations, to 50% for 3mm observations.
minutes
This integration time is spread evenly over the period that the source is above
the elevation limit specified below, or the period either side of transit satisfying
the hour-angle limit specified below, whichever is more limiting.
degrees
hours
If you would like the calculator to return velocity ranges and resolutions for
a particular line, please enter its rest frequency here, or select the line from the
drop-down list and press the "Set" button.
GHz
Reduction Details
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The calculator determines the theoretical RMS noise in a resultant image (Stokes I,
Q, U or V), along with the corresponding brightness temperature sensitivity. These
estimates are based on the expressions appearing in the ATNF technical document
AT/01.17/025,
the calculations of antenna efficiency as a function of frequency, revised (CABB-era)
measurements of system temperature as a function of frequency, and simulations of the
effects of different weighting schemes on images made with different ATCA configurations.
In calculating the effects of weighting, 30 second samples and Miriad default cell and
image sizes are assumed.
If you wish, you can calculate the effect that boxcar smoothing would
have on the reduced data by selecting a filter width here.
The calculator can discard the channels that are normally polluted with
self-generated RFI and known externally-generated RFI. Selecting these two options
is the equivalent of putting "options=birdie,rfiflag" into the atlod
Miriad task. You can also choose to
discard any number of edge channels; the analogue filter for CABB makes the
32 MHz on each side of the band noisier.
Calculation and Results
Not ready
Array
Using antenna forming baselines. The antenna efficiency is at the central continuum frequency.Sensitivity
Imaging
All velocities quoted below are with respect to the reference frequency of . weighting produces an RMS noise level equivalent to times higher than Natural weighting. The field of view at the continuum centre frequency is . At the zoom frequency you specified, the field of view is . The synthesised beam size at the continuum centre frequency is if only the five track antenna are used. Including CA06 would make the synthesised beam size .
The synthesised beam size at the specified zoom band frequency is
.