This page provides information on the continuum, spectral line, and mosaic sensitivity calculators. These can be used to assist in developing appropriately motivated sensitivity calculations and time requests that must be included as part of an observing proposal.

The calculators can be found at https://apps.sarao.ac.za/calculators/

Note that clicking on the ‘More information’ button on each tool will bring you to the appropriate section of this document.

Note: All MeerKAT bands are covered by the calculators and these calculators supersede the ipython notebooks released in a previous Call for Proposals. The calculators should be used for the preparation of any observation time request for MeerKAT.

Contents

Quick look tables of sensitivities

Table 1 below gives the theoretical thermal rms noise expected for some example integration times for continuum observations.

Table 1: Expected thermal noise for continuum observations in the L-band. We assume 58 antennas and consider only robust -0.5, which is a good default for continuum imaging, with no confusion noise estimates or Gaussian tapering. Confusion is not reflected in this table since it is dependent on declination and imaging parameters. Please use the continuum sensitivity tool for a more realistic calculation.

Open

Continuum sensitivity

This calculator takes into account expected beam size as a function of declination and imaging parameters to calculate confusion noise, in addition to scaled and tapered thermal noise. It does not take into account additional noise due to calibration errors and dynamic range limitations.

Using the calculator

Open

A screenshot of the continuum calculator, which consists of three input/output zones.

The top left area consists of a series of drop-down boxes for the observation and imaging parameters, and the planned integration time. To only apply Briggs weighting, select ‘Untapered’ in the tapering drop-down box.

Outputs are in the top right - details of calculations are described below.

The plot can be used to determine the optimal robust weighting for the proposed observations. Extraneous curves can be turned off by clicking on the legends:

Assumptions

L- and UHF bands

• A system-equivalent flux density (SEFD) of 425 Jy in L-band and 550 Jy in UHF band, per antenna, is assumed. Note that the SEFDs do have a slope as a function of frequency - full plots can be found here.

• The observatory minimum requirement for a science array is 58 antennas, though more are generally available. The calculator assumes 58.

• While careful flagging can, in some instances, yield some useful data in bands dominated by GNSS and GSM signals, these bands are generally discarded by continuum observers. This gives worst case effective bandwidths as follows: