Delta Use Case for EVLA Observing - Spectral Line Bryan Butler 2004-Aug-11 As described in the main use case document, subsequent use cases from that one will be presented as "delta" use cases - only providing steps that are different from those in the main use case. This is the second of these delta use cases, describing spectral line observing. I. Proposal Preparation and Submission ... 4. necessary resources, including configuration, frontend(s), backend (correlator) setup. Some detail on backend setup will be required here, to be sure that the desired observation is possible with the WIDAR correlator. This will include line width, total observing bandwidth, and required spectral resolution (all in km/s or MHz, e.g.). Rest frequency of the line must be input - common lines (HI, OH, NH3, etc...) should be provided as defaults. ... 5. source information: position, flux density, size, velocity (in km/s, or redshift), peak (in a single channel) and total integrated line flux density ... 7. time needed a) in order to figure out how much time is needed, the user may do one of: (1) specify an rms, from which the tool automatically calculates the necessary time. For spectral line observations, the ability to specify an rms per channel must be provided. (2) specify a dynamic range, then given the source flux density the tool figures out the needed rms and then the time. For spectral line observations, this dynamic range is at the peak of the line, and the rms is per channel. (3) for spectral line observations, the observer must input a required bandpass accuracy, e.g., .1%. This may drive the required observing time, along with necessary calibrations and accuracy. II. Observation Preparation ... C. the user then specifies the following: ... 2. a source list, containing all of the sources of interest ... d) a hardware setup for each source (including frontend and backend details), including integration time, correlator setup, etc... For spectral line observations, some detail on backend setup will be required here, to set up the WIDAR correlator: (1) rest frequency of the line - common lines (HI, OH, NH3, etc...) should be provided as defaults. (2) source velocity (3) total observing bandwidth (4) spectral resolution units of velocity, frequency, or redshift should all be allowed where sensible. ... g) a sequence of observations - including the cycle time between source and phase calibrators, and when to observe the flux density and, if needed, bandpass calibrators. Note that sensible defaults should be provided, of course. ... i) for spectral line observations, associated bandpass calibrators (might be the same for many sources) III. During Observing nothing beyond the default use case, except it should be noted that the user will be interested in seeing the instrumental bandpass (from TelCal, probably) and spectrum of target sources (from the Quick Look Pipeline). IV. After Observing (Data Access) nothing beyond the default use case...