Further Work

The calculator, in its current prototype state, is the product of 6 months of work by one developer. It is intended to be a sufficient platform to allow the development of a more sophisticated tool. There are already several suggestions for work that needs to be done in the future. These are grouped below according to their source.

SKA Engineering

It has been pointed out that SKA Engineers and Astronomers define ‘sensitivity’ differently, and there is some question whether the Sensitivity Model used by the Calculator matches that already in use by the Engineers. We need to ensure that we define and use our terms carefully and that the sensitivity models are reconciled.

Ideas from the Prototype

These ideas cropped up during devolopment of the prototype, but were considered too time-consuming or too far off in the future to be added at that stage:

• Shadowing. In reality, depending on the pointing direction of the dishes in the array, the dishes are likely to obscure one another, resulting in a loss of effective area. This can be accounted for by determining a shadowing fraction (i.e. what proportion of the total area is shadowed) and reducing the effective area by a proportional amount.

• Array configuration. The calculator currently only operates with the full array. There is an option in the calculator to select an array configuration but it currently does nothing. In the future, the user should be able to select from a preset list of configurations.

• Image weighting. The type of image weighting used will affect the sensitivity one can achieve with the observation. Incorporating the Briggs robust weighting parameter into the calculation will help reflect this.

• Beam synthesis. Running some simulations to synthesise beams would be incredibly useful and open up a lot of other options for functionality for the calculator.

• Weather. Currently the user is given the options of “Good”, “Average” and “Bad” weather, corresponding to pwv values of 5.8mm, 10.7mm and 19.2mm respectively. While this is important for the calculation of the atmospheric temperature, \(T_{atm}\), it is impossible for the user to predict what the weather is going to be like when their observation gets scheduled. Instead, it may make more sense to give options for different months/seasons, since then the user would at least get an idea what the weather conditions will likely be over the time their observations could be scheduled.

• Optional smoothing for zooms. Down the line it is probably a good idea to add a optional line smoothing option for zooms.

• More observing modes. The calculator currently sports two observing modes - continuum and line observations. As it is developed, it would be good to have more observing modes added. The prototype has a tab for pulsar observations (and some comments throughout the code), but there is nothing yet implemented for this mode - it is just a placeholder/suggestion.

• Report resources. Adding some report of the resources that will be used for the observation (e.g. compute time) would be a valuable addition to the calculator output.

• Populate inputs from URL. A handy feature would be if the calculator would parse the query string from the URL and preload the calculator inputs with those values. When combined with a ‘link generator’ feature which would be fairly straightforward to add, this would allow users to generate links to the calculations they have performed and share them with colleagues. When the colleague clicked the link/pasted it into their address bar, they would be taken to the page and the inputs would be loaded with the same values the first user had used.

• Other Calculators. In developing this calculator, it was useful to regularly look at other, similar calculators/tools which exist. These other tools helped inform design and inspire new feature ideas. A list of such calculators follows here, which will hopefully be of use as the calculator is further developed.

  • ALMA Sensitivity Calculator

  • ATCA Sensitivity Calculator

  • e-MERLIN Sensitivity Calculator

  • VLA Exposure Calculator

The Vision Thing

Would it be worth asking some people to write a (very) short story describing how they imagine they would use the SKA ‘in the ideal world’, especially with reference to the Sensitivity Calculator? Consider different scenarios e.g. standard observing, response to transient triggers, survey planning, whatever you can think of.