Mookodi

Mookodi is a low resolution spectrograph and imager, designed to be operated fully robotically. It was designed and built by Liverpool John Moores University (LJMU), and installed on the Lesedi telescope in December 2021. It will undergo a period of science commissioning observations during the first trimester of 2022, with the ability to do spectroscopy and low-cadence imaging.

Specifications

• Camera: Andor DU934P deep depletion camera, 1024 × 1024 CCD, 13 μm pixels
• Spectral range: 400.5 – 799.5 nm ^[1]
• Spectral resolution:

  Dispersion: 3.88 Å/px

  Resolution:

  80µm slit

  R = 301.0 @4671.23 Å

  R = 374.4 @5823.89 Å

  R= 492.5 @7642.02 Å

  160µm slit

  R = 172 @4671.23 Å

• Plate scale: 0.6 arcsec/px ± 0.06 arcsec/px ^[1]
• Field of view: 10' × 10'
• Slit: Long slit with narrow (80µm, 2") and wide (160µm, 4") sections.
• Filters:

  Filter Slide A: Full set of SDSS filters (u', g', r', i', z')

  Filter Slide B: Longpass order blocking (OB) filter, and clear filter. There are three empty slots in this slide available for future use.

1. ↑ ^{1.0 1.1} Preliminary values based on lab tests at LJMU or original spec. Actual values to be confirmed during commissioning.

Suitable Uses

• Spectroscopy
• Low-cadence imaging: the camera is not a frame transfer camera, and in the current implementation exposures are controlled via an iris shutter. The shutter is life-cycle limited and not suitable for high-cadence observations.

Prepare the Lesedi telescope by following the Lesedi start-up recipes. As Mookodi is on the old SHOC port, any references to the SHOC port should be taken to mean the Mookodi port.

The simplest way to operate Mookodi is via the web GUI, but navigation via a command line interface is also possible. Scripted observations are in development.

Note: Dark and bias frames cannot be taken via the web GUI at this stage. They can only be taken via the command line interface (CLI). Observers are encouraged to familiarise themselves with the current known issues before commencing their observing run.

Operation via the web GUI

Open the web GUI at mookodi.suth.saao.ac.za:5000. The GUI is divided into four sections: Instrument configuration, target acquisition, exposure configuration, and camera control. At this stage the target acquisition features are not implemented.

1. Instrument Configuration:
   • Select the desired configuration for each component. The pneumatics and lamps will respond on the push of the button, and indicate when they are busy or in the desired configuration. To conserve lamp lifetime, don't leave them on for extended periods of time.
   • Select the required filter via the dropdown menu under the Filter A or Filter B headings and press the SET button to activate the filter slides. The box above the dropdown indicates the name of the filter in position for each slide, or BUSY if the slide is still finding its requested position.
2. Target Acquisition: NOT IMPLEMENTED
3. Exposure Configuration:
   Select the desired configuration for each setting using the dropdown menu below the relevant heading, then press the SET button to issue the command to the camera.
   • Binning: Options are 1x1, 2x2, 3x3, and 4x4.
   • Gain: High (faint objects), medium, and low (bright objects)
   • Rate (readout rate): Fast (5 MHz), and slow (0.05 MHz)
   • Mode: NOT IMPLEMENTED
   • Number of exposures: NOT IMPLEMENTED
   • Exposure time (in ms): Note the exposure time display does not update when the SET button is pushed, it only updates after the exposure is started. This is a known issue.
4. Camera Control:
   This contains an image display of the last completed exposure, using JS9.
   • Take exposure/Start: Starts an exposure with the SET exposure configuration
   • Abort: Aborts the current exposure.
   • CCD Temperature: Displays the current CCD temperature, and buttons for cooling down and warming up. The camera takes 10 - 15 minutes to cool, and will stabilise at approximately -70 ºC. Cool the camera at the start of observations and warm it up once you are done.

Operation via the command line interface (CLI)

Note: Dark and bias frames can only be performed with the command line interface at this stage.

Camera CLI

From a terminal window:

ssh mookodi@mookodi.suth.saao.ac.za
de
cd development
mookodi-camera-cli

Type help to display options. Either the desired keyword or its number can be entered. Entering 1 displays the current camera configuration.

Instrument CLI

From a separate terminal window, or separate tab:

ssh mookodi@mookodi.suth.saao.ac.za
de
cd development 
mookodi-optomechanics-cli

Type help to display options. Either the desired keyword or its number can be entered. Entering 1 displays the current instrument configuration.

Data storage and retrieval

From a terminal window:

scp mookodi@mookodi.suth.saao.ac.za:/data/lesedi/mkd/yyyy/mmdd/* .<local path to copy to> 

Where yyyy is the year, mm is the month, and dd is the day. The convention is that the data rolls over to the current date at 1200 UTC, hence all the files from a given night are stored in the folder corresponding to the date at the start of the night. e.g. All observations started on the night of 2021/12/11 will be stored in /data/lesedi/mkd/2021/1211/.

It should not ordinarily be necessary for an observer to perform these procedures. However, if a restart is necessary, or if recovering from an unplanned shutdown:

• The Mookodi host machine is set to boot automatically when powered.
• There are three services that need to be run before Mookodi can be operated via the web GUI: opto-mechanics, camera, and web server. Each should be run in a separate screen session, otherwise they will shutdown when you close your ssh session.
• The opto-mechanics and camera servers need to be started before the web server.

ssh mookodi@mookodi.suth.saao.ac.za
./run_camera_server.sh
./run_optomechanics_server.sh
./run_web_server.sh

• The web GUI can now be accessed at mookodi.suth.saao.ac.za:5000

If there is an issue starting the web server, Mookodi can be operated via a command line interface. With the camera and optomechanics servers running, follow the instructions for CLI operation.

This section contains information for the technicians performing daily rounds.

Evening

• Switch on the compressor
• Check that instrument services are running (opto-mech, camera, web service) by opening the web GUI and configuring the instrument as follows:
  • Slit IN
  • OB filter SET (Filter Slide B)
  • 1000 ms exposure SET, Start exposure
• This should produce a noisy image at the camera (visible in the image view window), and all instrument mechanisms should respond as commanded.
• Slit OUT, filter out SET
• If anything fails to respond as expected, follow the troubleshooting procedures.

Morning

• Switch off the compressor
• Check that the camera is warmed up

• FITS headers are not populated with instrument information currently. This is a priority for early 2022. Observers will need to record observation information manually.
• Exposure time display does not update when the SET button is pushed, it only updates after the exposure is started.
• Filter slide A can time out when trying to reach a commanded position when Mookodi is in certain orientations.
• Abort button on the web GUI does not abort exposure, even though it reads as such. Exposure can be aborted via the CLI in the interim.