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Technical Justification
The technical justification for the various parameters entered by the user into the OT is now placed into a SG node. This presents the various inputs that need to be justified to the user on a single page and includes a text box into which the technical case should be entered. This node is laid out as follows:
- Relevant science parameters - these are simply a repeat of various important parameters that should be mentioned in the technical case. They mainly relate to the amount of time and arrays required to achieve the scientific goals.
- Expected source properties - these are taken from the Field Setup node, but include additional information such as the implied SNR.
- Continuum: aggregate bandwidth and sensitivity - the bandwidth is the sum of the non-overlapping bandwidth of the defined spectral windows. For single-continuum setups the sensitivity is just the requested Science Goal sensitivity. For spectral line setups the sensitivity is calculated using the aggregate bandwidth and the on-source time required to meet the requested line sensitivity.
- Continuum: peak flux density and SNR - this is the flux density of the faintest source defined and the SNR is the ratio of this to the continuum sensitivity.
- Continuum: polarization and SNR - the polarization will be printed of the source that had the lowest value of polarized continuum flux i.e. percentage polarization multiplied by peak flux density. The SNR is equal to the polarized continuum flux divided by the continuum rms.
- Line: peak flux density and SNR - this is the flux density of the faintest source defined and the SNR is the ratio of this to the requested line sensitivity.
- Line: polarization and SNR - the polarization will be printed of the source that had the lowest value of polarized line flux i.e. percentage polarization multiplied by peak flux density. The SNR is equal to the polarized line flux divided by the line rms.
- Line: line width and number of resolution elements - the line width is the narrowest that was entered and is divided by the spectral resolution of the Representative Window to form a measured of how many resolution elements cover the line's FWHM.
- Line: Dynamic Range - this is the ratio of the continuum flux to the requested line sensitivity and is a mesure of how good a bandpass is required i.e. detecting faint lines on a strong continuum is difficult. The continuum flux is therefore the largest of the values entered on the Field Setup page.
- Non-standard choices - this panel highlights parameters that might be perfectly reasonable, but which require specific mention in the justification text. These are:
- Non-Nyquist mosaic sampling - non-Nyquist values are usually used when the scientific goal is to cover a large survey area and large-scale structures are not being observed.
- Single polarization - dual polarization is more usual and single polarization only used when the highest spectral resolution is required.
- High data rate - if many high spectral-resolution spectral windows are defined, this will lead to a large data rate and associated data volume which impacts on the observatory's resources i.e. for data storage.
- Low max elevation - sources with low declinations will suffer large atmospheric attenuation and be difficult to schedule because of limited time above the horizon.
- User-defined calibration - this is strongly discouraged and must be rigorously justified.
- ACA choice overridden - the OT will recommend whether the ACA is required based on the largest angular scale that needs to be imaged. This recommendation can be overridden, but must be justified.
- Additional time required (for u,v coverage reasons) - if your source has a complicated structure, but the sensitivity requirement is such that not enough time is needed to build up sufficient u,v coverage, the OT's sensitivity-based time estimate may have been overridden. In the TJ node there must be a detailed explanation of why this is necessary and how the new time estimate was calculated. This must include calibrations and overheads.
- Time-constrained observing - these imply significant constraints on the scheduling of all ALMA projects and must therefore be fully justified. In addition, if ``continuous monitoring'' is selected, the time entered (which must include calibrations and overheads) must be explained.
- Justification text - up to 4000 characters of plain text can be written here. The text should justify the Science Goal setup, particularly in light of the parameters displayed above.
Next: Phase 2 Program Scheduling
Up: Phase 1 and Phase
Previous: Control and Performance
Contents
The ALMA OT Team, 2014 May 21