Science Parameters

The Science Parameters have the following items:

• Science Parameters Name: This should be a unique and descriptive identifier for the Science Parameters.
• Representative Bandwidth: This is the bandwidth that will be used to determine whether the requested sensitivity has been reached. It will usually be the spectral resolution for spectral line observations and the maximum usable bandwidth (7.5 GHz) for continuum.
• Representative Frequency: This is the frequency that will be used to determine whether the requested sensitivity has been reached and is read by the ALMA Data Reduction Pipeline for this purpose. It should be in the barycentric frame.
• Sensitivity Goal: This is the sensitivity equivalent to that requested by the PI. For the largest 12-m Array or the 7-m Array in the case of SACA, this is simply the value requested by the PI in the Science Goal. For the other arrays, this value is scaled by their relative sensitivity i.e. according to their antenna areas, number of antennas and the time spent observing. For the TP Array, an additional term is added which reflects the noise added by observing a reference position. Currently, the purpose of this parameter is for checking during the QA2 process that the requested sensitivity was met. Note that the sensitivity goal does not reflect any increases in the observing time due to the minimum time spent observing or quantisation issues. Therefore, the sensitivity goal is often worse than that expected in practice. For a sensitivity in kelvins where the PI entered a range of angular resolutions, the sensitivity goal is converted to a flux value using the nominal angular resolution of the largest configuration that is likely to be scheduled. In the future, this parameter might be used to halt an execution once the desired sensitivity is reached i.e. the integration time will be dynamically calculated.
• Integration Time on source: Desired integration time for each source attached to this Science Parameters. As dynamic integration times are not yet used, an SB will instead be observed for this amount of time. It normally consists of an integer multiple of subscans, each of which must run to completion. The total on-source time is given by this parameter multiplied by the number of executions. In general, more time than required will be observed due to quantisation effects such as only being able to observe integer multiples of complete mosaics.
• Sub Scan Duration: A subscan describes the smallest amount of data that can be continuously observed whilst the telescope is pointing in a specific direction, perhaps with associated scanning movement. This means that changing the telescope pointing (e.g. by changing the scan direction or moving to a new pointing direction) requires a new subscan and thus this parameter sets how long each position in a mosaic, or each scan in a raster, is observed for. If an approximation is entered (the real value often has lots of decimal places), a button is available to adjust this to the nearest legal value. A value of 30 s is typical. Once begun, a subscan will always run to completion i.e. and integration time of 31 s and a subscan duration of 30 s will produce 60 s of data. All subscan durations must be integer multiples of the integration duration and 48 ms.
• Force Atmospheric Calibration: Whether a system temperature measurement is needed will often be determined by the observing script, but checking this will ensure what one is taken every time the science Target is observed.
• Advanced Parameters: Not yet implemented.