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Technical Justification
In order for the proposal review committees to judge that the proposed observations are technically feasible and will achieve the scientific objectives, it is necessary for the user to justify the various choices that were made when creating the Science Goal. For example, for a spectral line observation it must be shown that the requested sensitivity and correlator setup will enable the line to be detected with sufficient signal to noise and that the spectral resolution of the correlator mode, perhaps including spectral averaging, is appropriate.
From Cycle 2 onwards the technical justification should no longer be submitted as part of the PDF that contains the scientific case, but instead using a node in the Science Goal. This has been designed to help non-expert users in particular in the writing of technical justifications and does this by presenting the relevant parameters that need justifying, including ``non-standard'' choices, in one location in the OT. The user should read the information presented in this node carefully and use and refer to it in the textual justification, which is also entered in this node. Please note that any figures which the user would like to refer to should go into the Scientific Justification PDF.
The following information is presented:
- Relevant science parameters - shown here are parameters that mainly affect the achieved sensitivity and the configurations and arrays that will be required.
- Expected source properties - this is mainly a repeat of the parameters that were entered in the Field Setup node, but are accompanied by their SNR equivalents and a dynamic range, if applicable. The number of resolution elements across the line width is also shown and includes the effects of Hanning smoothing and spectral averaging. A note on SNR and dynamic range calculations:
- If the SG contains multiple sources, the SNR calculations will use the lowest flux density that was entered. SNR values should be no lower than 5, although exceptions are possible.
- The dynamic range is only calculated if a continuum and line flux have been entered and is defined as the ratio of the continuum flux and line rms. The higher this parameter, the more challenging the observation will be as detecting weak lines against a strong continuum requires a very good bandpass calibration. Unlike the SNR value, the dynamic range is calculated using the largest source flux density.
- For spectral line projects where a continuum flux has also been entered, the OT will calculate a continuum SNR using a continuum rms calculated from the maximum non-overlapping bandwidth of the defined spectral windows and the on-source time calculated to acheive the line rms.
- Non-standard choices - there are a number of setup options which, if selected, should be mentioned in the technical justification text. For example, single polarization will normally not be selected as this results in lower sensitivity. However, for a given spectral window width, single polarization gives twice the number of channels and therefore it can be useful when very high spectral resolution is required. As another example, mosaic observations are normally conducted with the individual pointings separated by the Nyquist frequency, but in survey observations where large sources are not being imaged, this is not necessary and larger separations can be used. If this is the case, briefly mention this.
The justification text itself cannot exceed 4000 characters. If no text is entered than the project will not validate.
Next: Summary Information
Up: Adding Phase-1 Science Goals
Previous: Time-constrained observing
Contents
The ALMA OT Team, 2014 May 21