Use Case: Observing Preparation: Set Up to Observe a Single Field, Single Line, Easy Frequency Project.

This ObsPrep usage scenario is based on the SSR use cases and it represents a possible use of the OT to set up an observing project. It should not be considered as a replacement of the UCs in the SSR Memo 11. It has been developed to aid in testing the ability of the design of the OT to support the specific case of the described observation setup.

Goal:   Define a program using the ALMA observing tool for a single field and a single spectral line at an "easy" frequency.

Contact Author:   L. Testi

Role(s)/Actor(s):
Primary:   The observer (follows the basic course for this UseCase)
Secondaries:  
  Observing Preparation Tool
  Spectral Line Catalogs
  Source Catalogues and Databases
  DSS/2MASS Image Library
  Local User Resources (Catalogues, Images, Spectra)

Priority:   Critical

Performance:   Response to user inputs in near real time.

Frequency of Use:   Perform this ObsPrep Use Case for each single field, single spectral line imaging experiment that has been approved by the TAC for ALMA observations.

Preconditions:

1. Proposal written by PI and submitted to ALMA TAC.
2. Project approved by the TAC for ALMA observations and ready for phase 2.
3. Project goals and constraint are:
   Primary Science Goal:
   Image in a given primary line and in the nearby continuum at relatively high angular resolution the inner regions of a hot core, the aim is to resolve a rotating disk structure.
   Secondary Science Goal:
   Image the other possible components of the transition to derive various properties of the emission gas. Image at a suitable spectral resolution other interesting lines that may be observed with the main target line, if this does not degrade too much the continuum sensitivity.
   Primary Science Constraints:
     -   Spatial Resolution <= 0.1 arcsec (100AU @ 1kpc)
     -   Spectral Resolution <= 0.3 km/s (to resolve the velocity pattern)
     -   Range of Spatial Scales = 0.1-10 arcsec (from res to 10000 AU @ 1kpc)
     -   Line RMS <= 3 mJy/beam (in each channel)
     -   Continuum RMS <= 0.1 mJy/beam
   

Basic Course:   Set up for Observations (User steps and OT responses)

NOTE: All steps in the Basic Course should be able to be saved in the micro-archive or as stand-alone disk file these can be saved & reloaded for later processing and/or share between different Co-I (e.g. via e-mail exchange).

1. Select Project Type:
   Choose Standard Imaging; Spectroscopy
   
2. Select Target & Velocity: 
•  Source Name [Resolved by SIMBAD and coordinates presented] and/or enter name and coordinates manually [Galactic or Equ1950/2000]
• The user may want to specify the pointing position as offsets from the source coorinates
  
• Velocity and Velocity system
  
3. Select the Line:
   Use one or more selection methods:
   
   •  Name
   •  Catalog
   •  Pull-down-menu
   •  Frequency/Wavelength [Note: be sure this is accurate enough!]
4. If desired, view the primary beam displayed on a DSS/2MASS or local image. If a DSS/2MASS image is requested, the FOV needs to be entered by the user. If a locally supplied image is to be used, the OT will display the supplied image [which must have a compatible header] 
5. The user may want to refine the pointing position using either the Visual Editor (e.g. click/drag with the mouse) or by changing the coordinates
   
6. Enter Spatial Resolution and Range of Scales:
   The OT should display the Primary Beam on the image and give feedback on whether one array configuration is enough and whether one or more pointings and ACA/TP measurements are required to cover the max scale range around the target. The user should be able to change the parameters and have immediate feedback. If multi-field/ACA/TP needed, then follow the appropriate test case.
   
7. Enter Resolution/Bandwidth:
   The OT should provide a warning if more than one correlator setup is required to match the desired bandwidth at the requested resolution.
   The OT provides feedback: total bandwidth of the spectral window at the selected resolution.
   All other correlator bands are set to continuum observations with maximum bandwidth.
   
8. Enter Required RMS in Line or Continuum:
   The OT provides feedback on the total on-source time required and display the corresponding RMS in the other case (continuum if one specifies line and vice-versa), it should be possible to change which of the two the user sets, reset the value and get immediate feedback.
9. Set Up the Correlator with the following steps:
   
   • The OT shows a template spectrum around the selected line. It should be possible to switch between the "Orion hot core" template and/or other astronomical templates, a schematic view based on a line list, and a user spectrum (ASCII file with nu and intensities, can be theoretical or observed).
   • The user zooms in on the line of interest with a click, adjusts the band center to cover all the line components that the user can/wish given the available bandwidth of the spectral window.
   • The user zooms out for other possible lines of interest.
   • The user adjusts LO freq in order to cover the lines of interest.
     Note: The primary line can slip out of the originally selected correlator window domain and into another correlator window. The OT should be sure that the line is covered and not allow the user to select an LO frequency that prevents the observation of the primary line. The OT should be able to switch between correlator bands to ensure that the line is always covered with the required bandwidth/resolution.
   • The user should be able to zoom in on lines of interest and modify correlator bands to set resolution and bandwidth for these. The OT should update the continuum sensitivity for the bands that are subtracted from continuum to observe lines and should show the expected sensitivity in the "new" spectral bands in the given amount of integration time.
   • Low Priority: The user may want to select as "bad" some ranges (channels) of the continuum bands in order to avoid strong lines in the pipeline processed continuum image.
10. The user reviews the default calibration choices:
      -   The OT can be required to show the calibration choices (calibrator, calibration options, integration times, duration of observing cycles, etc...)
      -   The advanced user can change the (allowed) parameters and receive warnings/feedback on the expected calibration accuracy.
    
11. Required Feedback (TDB on where and when this feedback should be provided to the user):
      -   Beam information (expected beam ellipticity and axes)
      -   Total duration
      -   Weather constraints - stringency and likelihood to achieve
      -   Configurations required - availability and timescales
      -   Warnings related to data quality (due to calibration scheme chosen)
      -   Map sizes, data rate, total data volume
      -   Scheduling Block breakdown
    

Postconditions:

1. User saves the observing setup on their local machine. It should be possible to save the project in the OT local micro-Archive or as an external file to share the work with other CoIs (via e-mail). The actual scheduling blocks (SBs) should also be saved to the local directory if desired by the user. Note: the 'saved file' for the OT and the SBs can be the same thing.
2. The user requests that the programme and associated SBs are validated.
3. If validated, User submits the complete programme and associated SBs from OT.

Issues to be Determined or Resolved:   Required feedback listed in point 10. of the Basic Course above.

Notes:   The relevant UCs from SSR Memo 11 are: 4.1 [part], 4.2.1, 4.2.2, 4.2.3, 4.2.6, 4.2.8, and for the specific observing mode described above: 4.7.1 (actually the more relevant for the example laid out).

Last modified: 08jul03