The final technical specifications of your Science Goal are entered in the Control and Performance panel (see Fig. 3.9). The Configuration Information section at the top of the panel displays information on the array configurations planned for Cycle 3, and uses the representative frequency defined in the spectral setup to calculate the Synthesized beamsize and the Maximum recoverable scale of the observations.
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You can define and check technical details of the observations using the following fields (fields displayed in red must be filled):
Desired Angular Resolution: your choice is guided by the synthesized beamsizes corresponding to the most compact and most extended configurations available in Cycle 3 as displayed in the Configuration Information. The value entered cannot be smaller than the synthesized beam size of the most extended configuration, and cannot be larger than twice the synthesized beam size of the most compact configuration. You can input the angular resolution in arc-seconds or a fraction of the main beam size. |
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Observations requesting very small angular resolutions (i.e. those making use of long baselines) are very inefficient because they need to be heavily calibrated to correct for atmospheric phase fluctuations. Since the array configuration is determined based on the AR defined in the OT, it is possible to inadvertently trigger long baseline observations by entering an AR just slightly smaller than that actually required (e.g. standard B3 continuum observations requiring a 0.346#6 AR will trigger long baselines, while 0.357#7 AR observations will not). You can see if the observations defined make use of long baselines in the time estimate pop-up (the number of phase calibrator observations per SB execution will be unusually large, above 25 or so), or by running a validation check (see Section 3.10). Obviously, long baselines should be avoided if they are not necessary to achieve a Science Goal. |
Largest Angular Structure in source: here you should enter the largest angular structure that you wish to resolve in your source(s), which may be different from the actual size of the source. The value entered determines whether you need multiple 12-m configurations and/or the ACA, and therefore has a direct influence on the time estimate (see the Maximum recoverable scale for the 12-m configurations in the Configuration Information table for guidance.). The input units are the same as for the angular resolution. | ||||||||||||
Desired sensitivity per pointing: you should enter the sensitivity required for the most restrictive line/continuum observation to achieve the scientific aims of the Science Goal, and if relevant mention the S/N achieved for the remaining lines/continuum in the Technical Justification. In the case of a rectangular field mosaic you should specify the sensitivity required over the mosaic, not that for individual overlapping pointings. We recommend that the sensitivity requested is good enough to give a 3 8#8 detection at the very least, ideally 5 9#9. | ||||||||||||
Bandwidth used for Sensitivity: for continuum observations, this field is automatically set to AggregateBandwidth. For spectral line or spectral scan observations you can pick one of six choices given in the dropdown menu:
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Do you request complementary ACA observations: press the Suggest button to see whether the OT recommends/allows ACA observations based on the requested AR and LAS. The ACA comprises the 7-m Array as well as the Total Power (TP) Array. Note that the TP array is not offered for continuum observations and in Bands 9 and 10. You can choose to override the recommendation of the OT, but must carefully justify this in the technical justification. Note that the ACA cannot be used with the most extended 12-m configurations as this would result in a gap in the baseline coverage.
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Science goal integration time estimate: The Time Estimate button will estimate the total time required to achieve the desired sensitivity goal on the 12-m antennas, including calibrations, multiple pointings, and overheads (see Fig. 3.9). In the event that two 12-m configurations are needed to provide sufficient baseline coverage, the time breakdown will be calculated for the more extended of the two, while the time required for the more compact configuration will be calculated from the former using a fixed multiplicative factor. Similarly, the 7-m Array and TP Array observations are estimated to require a factor of 2 and 4 times the most extended 12-m Array observations respectively. Unless specified otherwise (see below), it is the total time reported here that will be used by the observatory as an estimate of how long your project will take to complete. Note that, for Cycle 3, proposals requiring more than 100 hours cannot be submitted. | ||||||||||||
Override OT's sensitivity-based time estimate If your Science Goal is not sensitivity driven, but instead requires a certain time (e.g. for a monitoring experiment) you can choose to override the OT's time estimate. The time entered should be the total time (including calibrations and overheads) for the more extended 12-m configuration needed; time estimates for the ACA are the automatically calculated by the OT. | ||||||||||||
Are the observations time-constrained? The OT now has the ability to capture the following time constraints:
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The ALMA OT Team, 2023 Mar 17