The DECam Software

3. The DECam Software

3.1 SISPI (Survey Image System Process Integration)

SISPI is DECam's read-out and control system.  Figure 3.1.1 shows a schematic overview of SISPI.

Figure 3.1.1 The SISPI Components shown in a block diagram. (DES-doc-1965-v8)

An exposure sequence starts when the observer sends a request to the Observation Control System or OCS (center of block diagram in Fig. 3.1.1).  The OCS first queries the state of the instrument and sends commands to the telescope control system to slew the telescope to the given location, to adjust the hexapod controller, and to load the requested filter.  Next the OCS preps the front end electronics to receive a new image. The OCS opens the shutter for the length of the exposure, and upon exposure completion, assigns an image builder process to assemble all pixel streams into the full image. The electronics are triggered to readout the CCDs. Image data flows from the DECam CCDs (Focal Plane) and the Monsoon front end electronics to the Image Acquisition and Image Builder systems before it is recorded on a storage device and handed over to the NOAO data transfer system (Data Management).  At a rate of 250 kpix/s it takes about 17 seconds to transfer the data from the focal plane to the computers of the Image Acquisition system. During this time the telescope can slew to its next position. 

Further details on SISPI can be found here.

3.2 Logging In and Starting Up

Before you can begin to take data you must log in.  When you click for the first time on any DECam GUI, you will be required to login. The user name is DECamObserver and the password is the proposal id of the observations taking place.  This password is valid only during the days of the run. It expires automatically afterwards.  By default, you will be logged in with authentication level user. At this level, you can watch the system, but you cannot control it. To control it, you will have to change your authentication level to observer.  This is done in the Observer Console, the first of the GUIs discussed below.

3.3 GUIs

The Graphical User Interfaces (GUIs) can be accessed from any browser at: http://system1.ctio.noao.edu:7001/apps, but full support for all the apps is currently provided only for specfic browser versions.  The GUIs of most interest to observers are highlighted below, and more details on all GUIs can be found here.

OBSERVER CONSOLE

The observer console (Fig. 3.3.1) is the main GUI to operate the system.  The Configure button (top right) is needed when you first start the system. The status display in the upper left corner informs you about the system status and if SISPI is ready to take an exposure. The element next to the status display is used to for exposure and setup control. Currently it consists of three tabs labeled System Control, Exposure Control and Runtime Control. The middle part of the page is reserved for information about the exposure queue on the left and current and past exposures on the right. The GUI elements on the bottom of the page can be collapsed to have more space for the exposure information. When visible the section in the bottom left corner show an animated view of the image data flow through SISPI. Messages from the OCS are displayed in the text field in the bottom right corner.

Figure 3.1.1.  Observer Console GUI

To take an exposure with DECam you have to submit an exposure request to the SISPI exposure queue, by selecting the Exposure Control view from the tab selector.  The top rows consist of parameters for your exposures.  Fill these out and add these to the observing queue by clicking the Add button.  Breaks can be added by pressing the Break button.  You may also upload a script containing a list of exposures and breaks. The button Enable Auto enables the auto pilot to set up the queue for you. To start running the queue, hit Go. To do a single exposure bypassing the queue, hit Step 1.  When your observations are in progress, the queue on the left shows the next exposures, the panel at the bottom shows an schematic view of the system as the current exposure goes on, the table on the right/center of the window shows the list of exposures already done or in progress. It includes information about the location of each image on disk.

A complete description of the Observer GUI can be found here.

COMFORT DISPLAY

A ds9 window on the comfort display monitor shows the last image taken, updating automatically as new images are completed. It shows all science CCDs and focus CCDs. A lower resolution png file (scaled down images of 1 graphic per crate) that can be easily displayed remotely is also produced and you can see it in the Comfort Display web GUI (Figure 3.3.2).  All of the images taken will be automatically transfered to the observer2 work station and can be more closely examined (i.e., with IRAF) from there.

Figure 3.3.2 Comfort Display GUI.

IMAGE HEALTH

This GUI displays detailed statistics on each CCD for each image.  Depending on which of the three image health views are selected in the bottom left corner, a color code indicates each CCDs (1) noise level, (2) sky level and (3) seeing.  The mean, variance per amps for the overscan and data regions are also displayed.  Clicking on a CCD will pop up the image of that particular CCD and the values for that ccd will display on the right panel.

Figure 3.3.3 The Image Health GUI.

ELECTRONIC LOGBOOK

DECam has an electronic logbook, in which exposures automatically are recorded.  Observers are encouraged to make comments.  Certain alarms will be automatically added to the logbook.  The logbook can be accessed either through SISPI, or independently, by pointing your browser to the url: http://system1.ctio.noao.edu:8080/ECL/decam .  A login is required to post (but not to view) logbook entries.

Briefly, additional GUIs include:

GUIDER, which shows the region of interest for the guider CCDs,

ARCHITECT CONSOLE, which shows all the SISPI nodes and the status of their components,

VARIABLE VIEWER, which allows the user to monitor shared variables,

EXPOSURE TABLE, which shows the list of exposures taken recently,

EXPOSURE BROWSER, in which you can query the exposure table,

ALARM HISTORY, which lists the alarms generage by the system,

INTERLOCK VIEWER, which shows the status of the various SISPI interlocks,

ICS, which shows the status of various instrument control system components (i.e., shutter, filter changer, hexapod, etc.)

TELEMETRY VIEWER, which displays time series of variable relevant to the operating stuats of the system (i.e., the LN2 tank level and pressure, the CCDs temperatures and voltages, etc.)

SCRIPTS EDITOR, which allows the creation of an observing queue, including multiple exposures and dithering

and further details can be found here.