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Mopra Sensitivity Calculator V2.0

Central Observing Frequency MHz
MOPS Configuration:
System Temperature: K Leave blank to use average value
For Position-switching mode:
Integration time (ON+OFF Positions):min
OR For On-the-fly mapping mode:
Length of scan rows: arcmin
Number of maps:  OR  Sensitivity to be achieved in a channel and pixel Ta*: mK    OR   Tmb: mK
Optional Smoothing Range:km/s (if applied, then the above input sensitivities are interpreted to be over the smoothing range)

To refresh the screen using the default entries, press SHIFT and click the 'reload' button of your browser simultaneously.

Central Observing Frequency

The observing frequency (in MHz) of the centre of the MOPS band. The value must be in the range:
12-mm: 16000 - 25000 MHz
7-mm: 30000 - 50000 MHz
3-mm: 77500 - 117000 MHz

Example: 22000

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MOPS Configuration

MOPS Refers to the Mopra Spectrometer, the new polyphase digital filterbank. MOPS can operate in wideband mode (8.2 GHz bandwidth) or zoom mode (137.5 MHz bandwidth).

Example: MOPS Zoom Mode

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System Temperature

The value of the system temperature for which you want to make the sensitivity calculation. Leave blank to use a value that is typical for good observing conditions at an observing elevation of approximately 60 degrees.
For each band the typical range of system temperatures in observing conditions is found to be:
12-mm: 50 to 120 K
7-mm: 60 to 150 K
3-mm: 200 to 700 K (Values > 400 K are for a central frequency above 98 GHz)

Example: 80 K

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Position Switching Mode

In this mode the observing sequence is OFF-ON. Where OFF is a spectrum taken a few arcmin offset from target. This observation is followed by a spectrum centred on the target (ON). The OFF spectrum is used for offline continuum/sky subtraction.

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Integration Time

The integration time for the OFF spectrum plus the integration time for the ON spectrum. The OFF-ON spectra pair must have the same integration time and because of sky instabilities should be taken no more than 5 min apart in time.

Example: 10 min which is equivalent to an on-source (target) integration time of 5 min

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On-the-fly Mapping Mode

In this mode, also called raster mapping, data is continuously taken while scanning along a row in either RA or Dec. A map is constructed by stacking several different rows. Each row is separated by less than the FWHM beamwidth. At the end of each row a single pointed observation at an OFF (reference) position is required. The OFF position is several arcmin from the mapped area. The OFF spectrum is used for offline/sky continuum subtraction. The scanning speed is limited by the number of seconds to average spectra over before writing to disk. For Mopra this value is currently fixed at 2 s.

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Length of scan rows

The length (in arcmin) of each row in the on-the-fly map. At this stage this calculator supports square maps only (as does the online schedule preparation tool). For 7- and 3-mm observations it is recommended that each map take no more than approximately 1 hour to complete so that antenna pointing checks can be made approximately every hour. With Mopra the following areas can be mapped in approximately 1 hr of observing:
4 x 4 arcmin^2 at 98 GHz (1 hr to complete)
10 x 10 arcmin^2 at 44 GHz (1 hr to complete)
For 12-mm observations antenna pointing is less of an issue. However it is generally a good idea to have each map take no more than approximately 2 hours to complete. In this case:
30 x 30 arcmin^2 at 22 GHz (2 hr to complete)

Example: 20 arcmin which will produce a map size of 20 x 20 arcmin^2

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Number of repeated maps

The number of times you intend to observe the same on-the-fly map in order to achieve a better signal-to-noise.

Example: 2

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Last updated 10 Oct 2013 by Dr Balthasar Indermuehle, Omnium Rector
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