Use Case: Observatory Mode: Tower Holography

Last modified: 20apr07

Goals:   Use the holography tower transmitter to map the surface accuracy of a single dish.

Contact Authors:   D. Shepherd, R. Lucas, J. Mangum

Role(s)/Actor(s):
Primaries:

• Staff Astronomer/Commissioning Team/Operator - Generate a holography project with one SB and submit it to the Archive, create an interactive mode array, submit the project for observations in interactive mode, extract the resulting ASDM from the Archive, reduce the data offline.
  

• ObsPrep - Provides a user interface to the Observing Tool (OT) to allow the astronomer to create the SB that defines holography inputs.
  
• Executive - Start up the integrated system, provide logging status of the holography procedure.
  
• Scheduling - Allows the Operator/Astronomer to to create an array for holography, query the archive for available SBs, and interactively schedule the SB. Display a list of available SBs when queried. Update the project status.
  
• Control - Activates the SB, drives the antennas, observes the tower signal, integrates in total power mode for each position observed in the raster scan; puts the data in the ASDM which is then written by Data Capture to the Archive. Control sends out notification that the procedure is complete.
  
• TelCal - Provides data reduction software (CLIC-based) which allows the astronomer to reduce the holography map after data is taken and then creates a results file (in ASDM format) that can be stored in the Archive.
  
• Correlator - No involvement. The holography receiver itself performs the correlations and reports those products 6 times per timing event (TE).
  
• Archive - Repository for the project/SB, holography data (ASDM), and holography results.
  
• DataCapture - Provides data flow and notification channel for broadcasts.
  
• Offline - No involvement.
  
• QuickLook - No involvement
  

Priority :   Critical (Tower holography can be done offline in an ad-hoc way but it is extremely desirable to have this automated for commissioning).

Performance :   Control, Data Capture, Scheduling & Archive activities must run in real-time or near-real time (within seconds).

Frequency of Use :   Every antenna will have to undergo tower holography at the OSF to measure the initial figure of the dish. Once set, this should not need to be re-done unless there is a problem with the dish surface. Once the antenna is in a science array, interferometric holography can be done.

Preconditions:

1. The Front End group provides a LabView GUI interface to control the tower transmitter and receiver. Using this interface, the staff astronomer turns on the transmitter before the holography run and optimizes the receiver.
• Note: the holography receiver is its own correlator. The phase and amplitudes in the beam map are obtained by correlating the signals from the horn at the antenna focus and from the reference horn looking directly at the transmitter. It produces 6 signals:
  • S*S, S*R, Q*Q, Q*R, R*R, S*Q
  where S, Q, R are the signal, signal(phase offset by pi/2), and reference signal respectively.
2. The Astronomer/Operator has a valid user name and password on console1 (also known as golum at the ATF), they have operator group privileges and access to the shared disk space (/userdata) from their home directory, and they have logged into the operators console (console1 or golum) as themselves.
3. The Astronomer/Operator started the ALMA software by typing runOMC from a terminal window. The following subsystems (at least): Control, TelCal, Archive & Scheduling. The Operator interface GUI is available and active. DataCapture is either running or ready for Control to start up when needed (DC runs within the Control component).
   • If the Astronomer/Operator has pre-configured the OMC layout, there is an omc.layout file in their home directory which will define what should be displayed when the OMC is first started and how it should be laid out.
   • The system startup (after typing runOMC) took less than about 3 minutes to start up (assuming the "start ACS" and "Operational" buttons were clicked in a timely fashion).
4. The OT should be able to generate the holography SB.
5. The Scheduler is ready for Operator input to create an interactive array and submit an SB or in Dynamic Mode (to automatically schedule an optical pointing SB that is high priority).
6. The Control subsystem is active and ready to execute an SB when requested by the Scheduler or Astronomer/Operator.
7. The Archive permissions are set to allow the Scheduler/Project Manager and DataCapture to write to the Archive.
8. The Tomcat server to allow the user to query the Archive via the ArchiveManager web browser has been started.
9. It is assumed that intents that are broadcast throughout the system are identified by TelCal as being associated with holography so TelCal will not respond to the scans and try to do anything in real-time. This is a change from the current (26apr06) software that must be coordinated between all subsystems and implemented before holography can be run with this use case. The work around is to put TelCal in an 'offline' mode which is not a good thing to do in the long term.
10. A verified, standard mode holography script has been written and is available for insertion into an SB in the OT project.
11. All documentation referenced below and additional detailed documentation on specific subsystems is available at: http://almasw.hq.eso.org/almasw/bin/view/Usertests/AcceptanceAIVDocumentation20070411

Basic Course:

1. The Astronomer/Operator creates a holography project/SB with the Observing Tool and specifies the input parameters needed to set up the resolution (related to the number of rows in the map), the observing frequency, scanning speed & direction, calibration mode and calibration integration time, and how often calibration should be performed at the bore sight. The Astronomer/Operator clicks the option for the standard mode script to be used.
2. The Astronomer/Operator requests that the OT verifies the scheduling block for holography and places it in the Archive.
3. The Astronomer/Operator sets up and tunes the holography receiver and slews the antenna to the bore sight position of the tower by typing the following command in an x-term window:
   • initializeHolography
   This single command will load the software for tower holography, initialize an array of one antenna (Vertex), slew the antenna to the tower bore-sight position, and tune the receiver to the high-band.
   • Alternate course: The Astronomer/Operator wants to use a different antenna or tune the receiver to the low-band: The Astronomer/Operator sets up the holography receiver for an arbitrary antenna using control command language (CCL). In an x-term window, the Astronomer starts up a "manual mode console" by typing mmc. A ccl>>> prompt will appear. CCL commands can then be used to select a different antenna for tower holography and initialize & tune the receiver as described in the ATF nominal procedures.
4. The Astronomer/Operator sets up the holography transmitter and tunes the receiver to the transmitter frequency using Labview GUIs.
   • NOTE: These LabView GUI interfaces are not part of the Computing IPT software deliverables. Brief procedures on how to use them to set up the transmitter and receiver under nominal conditions are provided in the ATF nominal procedures document written by the Computing IPT. However, the LabView GUI procedures in this document are not a computing deliverable; they are provided for convenience and may change based on commissioning tests.
5. The Astronomer/Operator uses the Scheduling GUI interface to select a sub-array with a single antenna to be used for interactive observing. The selected antenna has the holography receiver and associated hardware installed.
6. When the interactive array is created the Scheduler queries the Archive for a list of available SBs to run. If desired, the Operator can narrow the query parameters to show fewer SBs if desired (e.g. only those beginning with "Holo"). The holography project/SB is one of them.
7. The Astronomer/Operator selects the SB in the holography project via the Interactive Scheduler GUI interface and clicks on the "Execute" button.
8. Control creates an ExecBlock (EB) and begins execution.
9. ExecBlock execution events (controlled by the standard mode script that is referenced in the OT project - if this script is modified then the specific details below may change):
• Control slews the antenna to the starting Az/El of the raster scan. The starting point should be the measured beacon position. The offset slews will be relative to this position.
• Control begins integrations in total power mode for each position in the raster scan.
• The holography receiver performs the needed correlations and sends one total power and three correlated signals to DataCapture 6 times per timing event.
• Control slews the antenna to the next Az/El in the raster scan and the process repeats. Calibration observations of the bore sight position are done every "Cals row" number of rows as specified in the SB.
• When the entire xy raster is complete, the holography SB is complete.
• DataCapture transfers the data in ASDM format to the Archive.
10. While the ExecBlock is running:
    • Scheduling indicates the SB is running by showing an 'R' in the status column next to the SB name.
    • Control sends log messages to the logging channel in DataCapture and the logs are then relayed to the Archive. Log messages are displayed on the logger interface of the Operator GUI.
    • A "HOLOGRAPHY" scan intent is generated by Control and attached to all raster rows except for the bore-sight ones (in the ASDM scan table, each row is considered a scan). The bore-sight scans shall have a PHASECAL scan intent generated by Control. These intents are broadcast on a notification channel.
11. When the ExecBlock is complete the following happens:
• Control sends out an 'End' event and generates a log message saying that holography is complete.
• The log message is displayed on logger interface of the Operator GUI and sent to the Archive.
• The 'End' event will be used by Exec to update the status of the schedule block in the Exec 'Data Flow Panel.'
• The 'Data Flow' tab or sub-panel on the Operator GUI will indicate that the Exec block is complete (1-0 --> 1-1) and the total number of rows+bore-sight observations will be displayed as the total number of sub-scans taken).
• Project Manager (Scheduler) detects the completion event on the ExecBlock from the Control subsystem and updates the Project Status in the Archive if needed.
12. The Astronomer/Operator notes the UID identifier in the OMC 'Data Flow' tab (e.g. uid://X00/Xf/X2) and exports the resulting ASDM from the archive by typing the following command from an x-term window:
    • asdmExport uid_number
    Where the uid_number is the UID identifier noted above. The ASDM is written to disk. The name will be similar to the UID identifier except that '/' or ':' characters will be replaced by '_' underscore characters since disk file names are not allows to have these special characters (e.g. uid_ _ _X00_Xf_X2)
13. Processing of the holography data will be done offline by the Astronomer/Operator to allow for flexible interaction with the software. The following steps involve an interface to TelCal and the Archive:
    • In a terminal window on the operator console, the Astronomer/Operator moves to the directory in which the ASDM file was downloaded. They then start the CLIC data reduction software by typing 'clic.' Holography reduction is GUI-driven as outlined in the ATF nominal procedures and described in more detail in the HolographyHowTo document provided by TelCal.
    • After the reduction, disk files will be generated that describe the beam and provide a map of the holography results.
    • If desired, the Astronomer/Operator can also generate a Calibration Data Model (CalDM) result (e.g. holo-Result.sdm) that provides list of surface panel screws to be turned and how they should be turned (e.g. screw # 42: CCW 1/4 turn). The screw turn results will also be displayed on screen in a human-readable format. The CalDM result also contains two FITS images of the beam and map results. These FITS files can be viewed by any standard FITS image reader.
    • The CalDM result can be imported to the Archive using the command:
      • CalDMimport holo-Result.sdm
      Where the holo-Result.sdm is the name of the holography result on disk. A UID number will be reported giving the name of the result in the Archive.
14. The Astronomer/Operator should be able to download the CalDM result from the Archive using the command:
    • CalDMexport uid_number
    Where the uid_number is the name of the holography result in the Archive.
15. The Astronomer/Operator should be able to query the Archive from a command line in a terminal window:
    • archiveQuery -q {\"*\"} ASDM
16. The Astronomer/Operator should be able to query the Archive using the ArchiveManager from a web browser: using the address http://acc.atf.nrao.edu:8180/ArchiveManager/ (outside of the firewall) or http://10.30.1.2:8180/ArchiveManager/ (inside of the firewall). See ATF nominal procedures for how to query for specific types of files (schema) in the Archive.

Postconditions:

1. Holography data and the holography reduction results from TelCal processing are in the Archive.
2. The system logs are available in the Archive.

Issues to be Determined or Resolved:  

1. None at this time.

Notes:  

1. Use Case created by D. Shepherd based on conversations with Robert Lucas, Jeff Mangum, Alan Bridger, and Jeff Kern