ULTRASPEC user manual

Vik Dhillon, version: 14 March 2023

  1. Introduction
  2. Pumping down
  3. Powering up
  4. Powering down
  5. Afternoon activities
  6. Software startup
  7. Taking data
  8. Looking at data
  9. Logging of data
  10. Observing
  11. Drift mode
  12. Changing filters
  13. Archiving data
  14. Before you go to bed
  15. Troubleshooting
  16. Contacts


This manual describes how to observe with ULTRASPEC at the TNT. Other useful information can be found at:

Pumping down

This procedure is only to be undertaken by members of the ULTRASPEC team or NARIT staff who have been trained by the ULTRASPEC team.

  1. Move the rotator until ULTRASPEC is horizontal and press the emergency stop button.
  2. Locate the ULTRASPEC plunger valve, which is in the vacuum parts box in the ULTRASPEC cupboard in the dome.
  3. Remove the valve cap covering the vacuum port on the end of the ULTRASPEC cryostat.
  4. Fully withdraw the plunger and then attach it to the cryostat valve by tightening the large nut. To do this, the nut must be moved anti-clockwise. You will know when you have attached the plunger correctly, as it will not wobble and will rotate smoothly when tested.
  5. Push down the plunger and when it stops, start screwing the black knob in a clockwise direction. Keep doing this, watching the shaft height reducing until you feel significant resistance. The shaft is now fully engaged in the cryostat valve.
  6. Attach the flexible pipe from the red Pfeiffer vacuum pump to the plunger valve, taking care to only touch the outer edge of the o-ring, as any grease from your fingers can cause outgassing. Do not over-tighten the clamps, as this reduces the effectiveness of the o-rings. The pump and pipe should be positioned such that they exert no tension on the plunger valve.
  7. Ensure the needle valve at the top of the vacuum pump is closed by screwing it down anti-clockwise.
  8. Ensure that the large red isolating valve on the vacuum pump is closed by turning it clockwise until it clicks.
  9. Ensure the gas ballast valve inside the vacuum pump is open. This allows condensates, such as water vapour which collect in the pump due to the humid environment, to escape.
  10. Switch on the mains power to the pump by pressing the green on/off switch on the bottom right-hand side of the front face of the unit.
  11. Activate the diaphragm pump by pressing the right-hand button on the control panel.
  12. Ensure that the turbo pump is off by pressing the right-arrow button until menu item 23 (MotorPump) appears. If it is on, press both arrow buttons simultaneously, then press the right-arrow button again until off appears, and then press both arrow buttons again to set this value.
  13. Once the pressure in the pump bottoms out around 4 × 100 mbar, open the red isolating valve on the pump. The flexible pipe will now begin evacuating.
  14. What happens next depends on whether or not the cryostat is at atmospheric pressure. If the cryostat pressure is significantly lower than the pump pressure, then opening the plunger valve will allow outside air to rush into the cryostat, possibly contaminating the CCD. Hence the turbo pump must be on in order to ensure the pump pressure is lower than the cryostat pressure. Conversely, if the cryostat is at atmospheric pressure then opening the plunger valve with the turbo pump running would overload the turbo, possibly damaging it. Hence a different procedure must be used in each case.
  15. After a few hours of pumping, turn off the gas ballast valve, which prevents the lowest possible pressure from being obtained.
  16. Continue pumping until the pump pressure has reached of order 10-6 mbar and the cryostat pressure (which is always higher) has reached of order 10-5 mbar. For examples of how long this should take and the typical pressures achieved, please refer to the ULTRASPEC detector page.
  17. Close the plunger. This must be done quickly and forcefully, with significant strength required to push the valve fully in. Great care must be taken to ensure that the plunger is fully closed. This is probably the most difficult step of the pumping process, as most inexperienced users do not fully close the valve. If performed correctly, the cryostat pressure will then slowly begin to rise due to outgassing, but it should not rise significantly above 10-5 mbar.
  18. Unscrew the black knob on the plunger by turning it anti-clockwise, watching the shaft increase in length. When you feel the end of the shaft riding on top of the valve, withdraw the plunger. The cryostat is now safe.
  19. Close the red isolating valve on the vacuum pump. The pump is now safe. Power off the pump using the green on/off switch. The turbo will gradually slow down and the pressure in the pump will gradually increase.
  20. Disconnect the pipe from the plunger valve, which will release the vacuum in the pipe.
  21. Disconnect the plunger valve from the cryostat and replace in its bubble-wrap bag.
  22. The cryostat should immediately be cooled down by filling with liquid nitrogen, as described in the Afternoon activities, and the Lakeshore powered on, as described in Powering up

Powering up

A description of how ULTRASPEC's cables are connected is outside the scope of this manual and it will be assumed that this procedure has already been successfully accomplished. To then start ULTRASPEC from cold, the following operations must be performed:
  1. Check that the ULTRASPEC network switch housed in the blue NETGEAR box on top of the drpc in the control room is powered on.
  2. Turn on the drpc by pressing the large button on the front of the PC.
  3. Check that the green light on the mains socket strip at the top of the rear of the electronics rack is illuminated - this means that the rack is connected to the mains.
  4. Turn on the SDSU controller by flicking the switch on the rear panel of the SDSU PSU housing in the electronics rack. If successful, the fan in the SDSU PSU should start up and two green LEDs should illuminate on the front panel of the controller. If this doesn't work, check the fuses (see the Troubleshooting section for details).
  5. Turn on the vacuum gauge by flicking the switch on the rear of the display unit on the top shelf of the electronics rack.
  6. Turn on the filter wheel by flicking the on/off switch on the black filter wheel control box. The red LED display screen should flash the version number (3.02) whilst it tries to home the wheel. Check that the filters can be changed smoothly by pressing the 'next' button a few times, followed by 'home'. If this doesn't work or the display gives an error, see the Troubleshooting section for details.
  7. Check that the focal plane slide power supply is plugged in.
  8. Turn on the rack PC (housed in the black unit at the bottom of the rack) by pressing the round button on the bottom right-hand side of the front panel. Booting takes around a minute if the system was shut down cleanly. If the PC is recovering from a crash, rebooting may take longer than this whilst the system checks the disks. If you want to see what is happening on the PC whilst it is booting, use the LCD monitor on the sliding tray at the top of the rack; pull the catch under the lid to release it (it is fairly stiff) and press the left-most button on the monitor to power it on. Remember to turn the monitor off again when finished, as it is a source of readout noise. To stow away, release the two catches at the front left and right-hand sides simultaneously and push in.
  9. Turn on the Lakeshore temperature controller, housed approximately half way up the rack, by pressing the black switch from 0 to 1 at the rear of the unit. The front display should illuminate, showing (clockwise from top left) the CCD temperature, the cold finger temperature, the heater power and the CCD target temperature. In normal operation, the CCD temperature should be 160 K, the cold finger about 150 K, the target temperature 160 K and the heater power should be in its medium range; the percentage power value will vary between 0% and 100%, depending on the temperature of the CCD relative to the set point. If the heater power is off, you can set it by pressing the "Heater range" button until the "Medium" setting appears, after which you should press the "Enter" button. Never use the "High" power setting on the heater, as this can destroy the chip. If you want to change the set point, press the "Setpoint" button, then press the "1", "6" and "5" buttons (if you want to change it to 165 K) and then "Enter".

    Ideally, to ensure powering on the Lakeshore does not damage the CCD, Naidu recommends we adopt the following procedure, which the UKATC adopted for cooling the detectors in KMOS:
    1. The Lakeshore ramp should be set to ensure the temperature does not change by more than 1 K/min.
    2. The heater power should be set to off by default when powering on the Lakeshore.
    3. If there is a large difference between the set point and the actual CCD temperature on powering on the Lakeshore, the heater will come on at 100% power (the ramp is not initiated as the set point hasn't changed). This is dangerous for the CCD. So go into the control setup menu and turn off the ramp (this ensures the next step doesn't take ages to complete). Then change the set point to a few degrees below the current CCD temperature. Now turn on the heater - it should give 0% power - and turn the ramp back on. Then change the set point to the desired value. The heater will now come on slowly thanks to the ramp, which is enabled as there has been a set point change.

Powering down

During an observing run it is normal to leave everything turned on to minimise the chances of failure from power cycling the electronics. If, however, the power to the site is to be shut down, the system should be powered down in the following order (refer to the
Powering up section for the location of all relevant switches and devices).
  1. Ensure the observing system is shut down on the drpc (see Before you go to bed).
  2. Turn off the SDSU controller.
  3. Turn off the vacuum gauge.
  4. Turn off the filter wheel.
  5. Turn off the Lakeshore temperature controller. This turns off the heater which means that the chip will now start to cool even further if the cryostat still contains liquid nitrogen. Once this boils off, however, the chip will gradually begin to warm up. It is best not to pump the cryostat during warm-up due to the low pressure that ULTRASPEC achieves in its cryostat when cold - there would be a risk of reverse pumping occuring due to the pump pressure being higher than the cryostat pressure. The chip is always warmer than the cold finger during a gradual warm-up, so there should not be any risk of condensation onto the detector.
  6. Shut down the rack PC by typing "init 0" in an xterminal connected to the PC or by using the sliding monitor and keyboard in the electronics rack. This does not turn the PC power off, so when the LCD monitor says "System halted" you should press the power button.
  7. Turn off power to the entire ULTRASPEC electronics rack by switching it off at the mains.
  8. Shut down the drpc by selecting the Log Out option from the Application Menu on the bottom left-hand side. Then click the Shut Down button on the window that appears. The PC will power down automatically on completion.
  9. Disconnect the white Thai-format power plug underneath the desk where the drpc is located.

At the end of an observing run, when ULTRASPEC is not scheduled for use for more than one night, please shut down the following:

  1. The rack PC - pull out the keyboard at the front of the rack. Login as superuser (>su >password available on page 4 of Paul Kerry's user guide to the ULTRACAM/ULTRASPEC computers) and type init 0.
  2. When the system has halted, turn off the rack PC by pressing the power button on the front.
  3. Turn off the SDSU controller using the on/off switch at the back.
  4. Swith off the black filter wheel control box on the top shelf of the rack
  5. Unplug the power supply to the focal plane slide, which is plugged into the white power strip at the back of the rack.
  6. Leave the drpc in the control room running, as this system is sometimes accessed by ULTRASPEC team members remotely.

Afternoon activities

Before you start observing in the evening, you and/or the NARIT technical staff should do the following. If you are remote observing, you can jump to item 6.
  1. In the dome, check the CCD temperature on the Lakeshore temperature controller is stable and within 1 degree of 160 K.
  2. Check that the cryostat pressure is stable and 10-4 mbar or lower.
  3. Fill the CCD cryostat with liquid nitrogen. First, position ULTRASPEC so that it is horizontal and on the dewar side of the Nasmyth focus. Then push the Emergency Stop button and ensure no-one can access the floor below. Donning a face mask and gloves, insert the filler tube into the cryostat, and then withdraw it by approximately 1 cm. Slowly open the valve on the dewar. Depending on the pressure in the dewar and the temperature of the CCD, the cryostat will take 1-20 minutes to fill. When liquid nitrogen begins pouring out of the filler tube, the cryostat is full. Close the valve on the dewar, remove the filler tube from the cryostat and carefully replace the filler tube in its holder on the dewar. The hold time of the cryostat is approximately 20 hours, but for safety it should be filled twice per day, once in the afternoon before you start observing and once in the morning after you have finished observing (see Before you go to bed). Never fill the cryostat if the vacuum is higher than 10-4 mbar. If this occurs, the chip must be allowed to warm up, and the cryostat will need to be pumped down prior to filling with liquid nitrogen (see Pumping down).
  4. Log the cryostat pressure, chip and cold finger temperatures, and the time the cryostat was filled in the blue log book on top of the electronics rack.
  5. Ensure that the cables running from the instrument to the electronics rack are neatly arranged, show no signs of damage and are not under any stress.
  6. Check to see if you need to make a filter change for the start of the night. If you do, refer to Changing filters.
  7. Ensure all lights are turned off in the dome.
  8. In the control room, check that the end_of_night_tasks script (run on the drpc) successfully completed without error.
  9. Once you are happy that the previous night's data is safely archived (see Archiving data for details), check the contents of /data on the rack. This should be empty of run files, which then ensures that the first run of the coming night will be run001 (strongly recommended).
  10. Start the observing system (see Software startup).
  11. Take bias frames for all of the setups on the previous night (the pipeline option missbias can aid this task) - see Taking data. To ensure minimal light falls on the CCD, ask the TO to turn off the dome lights, close the primary mirror covers (if operational), and align M4 to a port other than ULTRASPEC's, e.g. the 4k camera position. Also, ask the TO to turn the air conditioning in the dome off, as this increases the readout noise. Then position the focal plane slide at pixel -100 (by pressing the block button in the focal-plane slide menu on usdriver), and use the lowest-throughput filter in the wheel, e.g. u' or z'.
  12. Take some full frame bias frames in normal/slow (highest priority), normal/medium, normal/fast unbinned and binned 2x2, time permitting. See
  13. Check the readout noise and bias level of the normal/slow bias frames using the python quality control script. If using the HiPERCAM pipeline: /home/observer/qc/ultraspec/uspec_qc_hicam.py, e.g. /home/observer/qc/ultraspec/uspec_qc_hicam.py /xs run002_002. If using the ULTRACAM pipeline, the corresponding command is: /home/observer/qc/ultraspec/uspec_qc.py. Whichever pipeline you are using, you will first have to use the option grab to generate the required hcm (or ucm) files - remember to delete these after use and/or generate them in a sensible location, e.g. /home/observer/reduce/tmp. Note that if you try to grab data that is not in the /data directory, you need to give the relative path to the data, e.g. to grab run002 in a directory on /data1, use the run name: ../data1/2019_02_27/run002. The bias level should be approximately 850 counts and the readout noise is usually in the range 5-6 counts (but should ideally be 3.5 counts). Further details can be found on the ULTRASPEC detector page.
  14. Check the sunrise / sunset times, e.g. using the ING object visibility page (selecting the Thai National Observatory option).
  15. You can prepare for your planned observations using Stuart Littlefair's usfinder tool. Click on the icon on the desktop of the drpc, and follow the instruction in the online manual to produce your finding charts. You may need to re-size the window if you need to select drift mode.

Software startup

ULTRASPEC can be controlled from any Unix system connected to the ULTRASPEC internal network (see the
Troubleshooting section for details), although it is usual to use the ULTRASPEC drpc in the control room.

  1. Login as observer to the ultraspec drpc in the control room, if prompted. This machine has the IP address If you don't know the password, please contact one of the ULTRASPEC team members.
  2. Open a window on the rack PC by double-clicking on the rack icon on the desktop. Alternatively, you can type rack or ssh observer@ in an xterm. You shouldn't need a password to do this. If you need to know the password, please contact one of the ULTRASPEC team members.
  3. Ensuring that the SDSU controller is switched on, type the following in the xterm of the rack PC:


    The following windows should then appear:

    1. The "camera" window provides information on the commands used to control the CCD, which are sent to the SDSU controller.
    2. The "filesave" window provides information on the commands used to define the quantity of data to be expected, which are sent to the SDSU-PCI card in the rack PC.
    3. The python-based GUI (known as usdriver) sends the xml documents containing the camera and filesave parameters to the SDSU controller and PCI card via the http protocol. A small window will pop up on starting the GUI which will prompt you for a log file name in which to store the command history for that session. Give a filename of the form, e.g. 2015_03_25_usdriver.log
    4. The "Fileserver" window allows users to access data files on the rack PC. You can iconize this window when it appears.
    5. The "Lakeshore temperature monitoring" window which records the CCD temperature every 10 seconds.

  4. Now power on the CCD controller by clicking on the "Initialise" button in the "Instrument setup" box on the upper left-hand side of the GUI. The filesave window should then report the creation of a new run file in the /data directory. At the beginning of a night, this should always be run001. If it isn't, close the observing system down, clear the /data disk, and restart the system. You are now ready to take data.

  5. If taking frames with windows which include the overscan regions, you may wish to run the bias Checker program (the icon can be found on the desktop of the drpc) which will display the read out noise of each new frame taken by ULTRASPEC. It will flash red if the bias levels or read noise are significantly different to the nominal values.

Taking data

To observe with ULTRASPEC, xml applications must be set up using the python usdriver GUI and posted to the rack PC, before starting the exposures.

  1. If the previous configuration is still present and greyed-out, click Unfreeze in the "Observing commands" box on the upper-left side of the GUI.
  2. All non-greyed-out windows and options in the "Instrument parameters" and "Next run parameters" boxes on the upper right-hand side of the GUI should be set accordingly for each run.
  3. The "Count & S-to-N estimator" box on the left-hand side of the GUI can be used for rough signal-to-noise calculations in the 5 SDSS filters, and also displays the calculated exposure times and frame rates for the configuration set in the "Instrument parameters" box.
  4. Once you have entered the Target Name in the "Next run parameters" box, you should verify that it is either available in SIMBAD or in the ULTRASPEC target database by clicking the Verify button. Remember also to click on the correct data type button, and enter the ID, PI and observer details if not greyed out. This aids the data logging procedure.
  5. To change numbers in the boxes, you can left-click to add one, right-click to subtract one, press PageUp to go to the maximum allowed value, PageDown for the minimum, Shift-left/right-click to increase/decrease by 10, Ctrl-left/right-click to increase/decrease by 100, or type the required number manually. To take an unlimited number of exposures, set the Num. exposures box to 0.
  6. When you are happy with the configuration, click Start in the "Observing commands" box. You should see the frame counter increasing in the filesave server window, unless you are running in quiet mode (see Drift mode).
  7. Click Stop if you wish to finish exposing before the requested number of frames have been taken.
  8. If there is any chance you might return to the same target in the future, it is useful to save the configuration settings by clicking the Save button in the "Observing commands" box. The application with all the settings (e.g. binning, window sizes, exposure delay etc) can then be loaded next time by clicking the Load button. All applications should be stored in the /home/observer/.usdriver/apps directory.

Looking at data

As of December 2019, you can use the python-based HiPERCAM pipeline reduction software. This is now the recommended method of looking at ULTRASPEC data, as the ULTRACAM pipeline is no longer supported. You can still use the ULTRACAM pipeline if you need to - instructions on how to do this are given below.

Running the HiPERCAM pipeline requires the same FileServer to be running, but no initialisation command is required to start the pipeline. Please ensure that the real-time data reduction performed on each night is stored in a directory of the form /home/observer/reduce/yyyy_mm_dd on the drpc. Please also ensure that all output files from the pipeline are named according to the run number being reduced. So the standard reduction sequence using the HiPERCAM pipeline would be:

There is a new defect file made specifically for ULTRASPEC when using the HiPERCAM pipeline on the drpc - it can be found in /home/observer/reduce/defects/defect_hicam.dft. The defects can be over plotted when using the command rtplot, to help you avoid placing targets or comparison stars on bad pixels. The red/yellow dots show pixels which suffer more than a twenty/ten percent decrease in responsivity in flat fields.

Please tidy up the /home/observer/reduce/yyyy_mm_dd directory at the end of each night, as it is now archived along with the raw data by the end_of_night_tasks data-archiving script (see Archiving data for details).

If desperate, you can still use the ULTRACAM pipeline reduction software to look at ULTRASPEC data either in real-time or off-line - see the manual for details. The details given in the rest of this section below refer only to the ULTRACAM pipeline, not the HiPERCAM one.

First, open a terminal on the drpc by clicking on the drpc icon on the desktop. The latest version of the software can be initialized by typing the following command in the terminal:


If you have problems running this version, type ultracam followed by a tab, which will show you all of the versions currently available on the drpc.

You can then type any of the pipeline reduction commands, e.g. rtplot. A useful introduction to the ULTRACAM pipeline is Tom's Getting Started page.

There are three defect files available which can be over plotted when using the command rtplot, to help you to avoid placing targets or comparison stars on bad pixels. They can be found on the drpc at:
The first displays pixels which suffer a ten percent decrease in responsivity in flat fields, the second shows those pixels with twenty percent responsivity drops, and the third plots both. Small red dots represent ten percent loss pixels, larger red stars indicate twenty percent pixels.

If you wish to convert the .ucm files on the rack to .fits files:
  1. On the drpc, go to the directory where you want the FITS files to be written.
  2. Check that the FileServer is running
  3. Type tofits.py -u run015
  4. This will produce a sequence of files named run015_1.fits etc
  5. To see more options type tofits.py -h
To wish to convert the .ucm files on the rack to 3D FITS files:
  1. As above, but type to3dfits.py -u run016
  2. This will produce a multi-layered FITS file for each window named run016_1.fits etc
  3. To see more options type to3dfits.py -h
These programs will also create ASCII files named run***.times with the GPS timestamps at the centre of each exposure.

Logging of data

slogger is a c-shell script which produces a log of ULTRASPEC observations on a web browser. slogger also provides status information on the current run, outputting an audible and visual alarm if the CCD temperature rises above 165 K, if the GPS stops working and if the file size goes over a user-defined limit. Please refer to the
Troubleshooting section for advice on how to deal with the problems reported by slogger.

The slogger script runs in real time on the rack PC. The script works by polling the directory containing the data (usually /data) and extracting information from all the xml files it finds. For each ULTRASPEC data file, it also determines the start/end times, file size, number of frames and exposure time. Comments on each run are input using an optional comments file, which must reside in the same directory in which slogger is run. An example of the optional comments file can be found here - it is essential that you do not change the format of the file, i.e. the two header lines and the order of the columns. The easiest thing to do is to use a copy of the previous night's file for the new night. Any keyboard character can be used in this file except < and >.

To run slogger whilst observing on 2013_11_05, open a new rack PC terminal and type the following:

cd /home/observer/slogger
emacs 2013_11_05_log.dat &  -  and enter the run number and comments for any runs already taken.
  >   /data (the directory on the rack PC to which data is written)
  >   2013_11_05_log (the name of the log file - omit the .dat)
  >   6000 (the file size at which you wish the alarms to go off)
  >   y (to test the speaker volume level)
(slogger   /data   2013_11_05_log   6000   y   typed on the command line will also work.)

The script will run indefinitely, polling the data directory a few times every minute and looking for changes in either the data files or the comments file. If it finds a change, it will update the log displayed on the web browser. To exit slogger, just type crtl-c, but only do this when slogger says that it is safe to do so. The final log is written to a file in html format - in the example above the resulting file would be called 2013_11_05_log.html.

slogger can also be run off-line (i.e. when not observing) on the rack PC in exactly the same way as described above and can be used to poll any directory on the rack PC containing ULTRASPEC data.

Note the difference between the Pre-run comment that can be entered in usdriver and the comments that are entered in the slogger comments file. The former are written once only at the very start of a run. The latter can be changed at any point during or after a run, and hence should be used as the primary source.


Drift mode

To obtain the highest frame rates it is necessary to use drift mode, where CCD windows are stacked up in the masked region of the frame transfer chip. A full description of the algorithm is given in the
ULTRACAM MNRAS paper. Generally speaking, it is best to use drift mode when you require approximately 10 Hz frame rates or higher, as otherwise the dead-time due to frame transfer across the 1024 rows in the masked region (which takes approximately 24 milliseconds) becomes a significant fraction of the exposure time.

To take data in drift mode, it is recommended that the observing system is started (see Software startup) with the "-q" (for "quiet") option as follows:

start_uspec -q

The above command suppresses the frame number from being written to the filesave window, reducing the demand on the data reduction PC. It is recommended that you do not overload the rack PC, data reduction PC and ULTRACAM internal network with non-essential tasks when running in drift mode at the highest frame rates in order to minimise the chances of crashes.

If the sky is bright, you might notice that the top part of a window has a different background level compared to the bottom half. This occurs when it is impossible to fit an integer number of windows in the image area and hence part of each window exists on the chip (and hence accumulates sky) for slightly longer than the other part. To negate this effect, put the focal plane mask in the beam. The focal plane mask can also be used to prevent bright stars lying on the same column as your target star but on a higher row from corrupting your image. The slide is also useful if you want to minimise the light falling on the chips when taking bias frames and darks.

The focal plane mask is most easily moved from usdriver by pressing the Focal plane slide button on the upper left-hand side of the GUI. Enter the requested y-pixel postion and click goto. When you have finished this target, click unblock to return the slide to its default position, just outside the view of the CCD.

Setting up for drift mode can be quite tricky - it is recommended that you use setup windows in rtplot to assist you. You can then take full frame images and plot the positions of the drift mode windows in rtplot, allowing you to move the stars into the centres of the windows. Note that you have to use for the name of the setup windows file in rtplot.

Changing filters

Only attempt a filter change if you have been shown how to do so by trained NARIT staff or a member of the ULTRASPEC team.

  1. First, locate the filter(s) you wish to insert into the 6-position filter wheel. These should be found in the wooden boxes in the glass-doored Dry-Cabinet inside the TNT dome. Also locate the air blower and blue gloves in the optics cleaning box, and the small, magnetic Philips screwdriver in the toolbox, all of which are located in the ULTRASPEC cabinet in the dome.
  2. Turn off the filter wheel control box. Unscrew the fastening bolt on the side of the filter wheel housing, being careful to catch the little washer on the end of the bolt. Open the filter wheel door and, holding the edge of the filter wheel, unscrew the central bolt keeping the wheel in place. Carefully slide out the filter wheel, taking great care not to let anything touch the filters. This is best performed with gloves on.
  3. Lay the filter wheel down on a clean surface.
  4. Take out the filter you wish to replace by unscrewing the small screws holding it in place. Be very careful not to drop the screws onto the filter.
  5. Check the air blower is blowing clean air by spraying it first onto your hand. When the flow is definitely clean, blow off any dry residue or dust from the filter. If using a compressed-air canister, make sure you do not shake it prior to spraying on the filter, and always hold it upright.
  6. Return the filter to its correct position in the filter box, carefully storing it inside its labelled pouch.
  7. Place the new filter in the empty position. It does not matter which way round the filters go.
  8. Replace the small black tabs and screw the filter in place, being very careful not to allow the screwdriver to slip off the head. Check that the filter is not loose by picking up the wheel and gently shaking it. This is a particular problem with the KG5 filter. If loose, use one of the square plastic shims located in the wooden filters box in the Dry-Cabinet or the cardboard filter-wheel box in the ULTRASPEC cabinet.
  9. Repeat for any other filters that need changing.
  10. Use the air blower again to blow off any dust before returning the filter wheel to the housing. The side of the filter wheel with text should face towards the ULTRASPEC cryostat.
  11. Carefully slide the filter wheel into the housing, and then tighten the central bolt until you cannot pull the wheel out again. Try rotating the edge of the wheel to make sure it is securely located - if difficult to turn, it could be that you have overtightened the central bolt (although make sure the power is off to the filter-wheel control box, as this can also cause resistance to motion).
  12. Close the filter wheel door, making sure you place the washer on the bolt between the door and the housing. Firmly tighten this bolt.
  13. Turn on the filter wheel control box (see Powering up). If there are any problems, see the appropriate Troubleshooting section.
  14. Note down which positions hold which filters, and use this mapping to update the filter options on the usdriver GUI. Click Filters from the top bar, then Edit filters.

Archiving data

At the end of the night, ensure that slogger has been correctly shut down and that data taking has completely finished.

Make sure that the USB disks are mounted by typing df in a drpc terminal. If they are not mounted, right-click on their desktop icons on the left-hand side of the screen to mount them.

Run the script end_of_night_tasks from the drpc. This archives the original data, which is stored in /data on the rack PC, to two large-capacity USB disk drives in the control room. The script also makes a copy of the data on the archiving disk /data1 in the rack PC, and a subdirectory of /data. Critically, this script also corrects for an intermittent timestamping error. When such an error is found, the data file is automatically corrected, and a copy of the original, uncorrected file is made with a filetype .dat.old. The script is self-explanatory to run.

Before you go to bed

  1. Make sure that the slogger logs are up-to-date and complete for the night.
  2. Shut down the observing system by closing usdriver using "Quit" on the top bar, and typing ctrl-c in the filesave and camera windows (in that order).
  3. Close down the Lakeshore temperature monitoring by typing ctrl-c in the Lakeshore window. This ensures a new log file is created each day, and hence helps to prevent the creation of very long files which are difficult to search through when problems with the CCD temperature occur.
  4. Archive all data obtained during the night (see Archiving data).
  5. Fill the CCD cryostat (see Afternoon activities).
  6. Go to bed.


start_uspec does not bring up filesave and camera windows

This problem will occur if the observing system is already running. It may also occur if the SDSU controller is not powered on or has failed in some way. If the SDSU seems ok, try rebooting the rack PC by typing init 6 when logged in as root - please refer to Paul Kerry's
user guide for details on how to do this.

Unable to connect to the rack PC

Unless you can spot a broken or disconnected network cable, this usually happens because the rack PC has crashed. Go into the dome, turn on the LCD monitor in the rack and hit return on the keyboard. If the normal login prompt does not appear, then the rack PC has probably crashed. If you are unable to bring it back up, switch to the spare rack PC, which is located in one of the black crates, and contact one of the ULTRASPEC team. Note that the rack PC contains a clone disk which is rsynced from the system disk each day at 02:00 UT, so if a faulty system disk is the cause of the rack PC failure, it is possible to swap it with the clone disk (but only when the rack PC is powered down). If you do have to switch to the spare rack PC, you will find that the software on its system disk is likely out of date, and most of your usdriver applications and slogger files, for example, are not present. In this case, the easiest thing to do is to replace the system disk of the spare rack PC with the existing rack PC system disk, or its clone, and try booting. If this fails, you could instead try copying over any files that you need from the existing rack PC's system disk, or its clone, mounted in one of the hot-swappable bays, but boot from the spare rack PC's system disk. Remember also to move over the /data and /data1 disks to the spare rack PC.

Note that the flashing amber light on the front of the rack PC is normal. This indicates that the CPU fan isn't working, but the rack PC does not have a CPU fan, so it can be safely ignored.

Data reduction PC hangs whilst exposing

If the drpc hangs or crashes whilst exposing, it is possible to safely stop the exposure by opening an xwindow on the rack PC from another computer connected to the internal network and then typing usdriver. When the GUI appears, go into expert mode by checking the expert button on the Settings menu. Then click on the observing tab and click the STOP button. With the data safe, you can then try to reboot the data reduction PC. This will kill the camera and filesave windows, of course, so you might also have to reboot the rack PC.

There has been one occasion when the data reduction keyboard stopped responding, probably due to an illegal combination of keystrokes. This was fixed by killing the windows one by one until the offending window had been killed and the keyboard started responding again.

If you are unable to get the drpc working again, you can switch to the spare drpc, which is stored in the black crates. Please refer to Paul Kerry's user guide for details on how to do this. Note that the data drpc contains a clone disk which is rsynced from the system disk each day at 04:00 UT, so if a faulty system disk is the cause of the drpc failure, it is possible to swap it with the clone disk (but only when the drpc is powered down). You can also connect a personal laptop to the switch in the control room and use this to observe, as long as it is a Unix system with the ULTRACAM pipeline installed on it.

Inexplicable crash whilst taking data

This hasn't happened with the new data acquisition system installed in early 2010. If it does recur, one reason could be because you have filled the /data disk. Another reason could be that you are pushing the system to its limits either in terms of data rate or frame rate. The former occurs, for example, when using drift mode at high-frame rates with the fast readout speed. If you experience a crash, try running the same application with the slow readout speed, in quiet mode, which should be more stable.

GPS problems

You can check whether the GPS is working by typing mbgstatus on the rack PC. The output of this command is also displayed in the GPS window in slogger. We have not yet experienced any problems with the new Meinberg GPS system installed in early 2010. If you do experience problems, possible causes might include: has the antenna mounted on the inside of the dome been damaged? Has the GPS cable running between the antenna and the electronics rack been damaged? Has there been a lightning strike nearby? If the GPS does not work, there is a complete spare GPS system in one of the black packing crates.

SDSU controller won't initialise

This problem is most likely due to a faulty SDSU power supply unit (PSU). If this problem occurs, no run file will be created when initialising the system. Also, the lights on the front panel of the SDSU controller will not be lit as normal (e.g. there might be an amber light, or more than one blank LED). To solve the problem, first try to power cycle the PSU. If this doesn't fix the problem, despite repeated attempts, the solution is to switch to the spare SDSU PSU, which is located in the black packing crates on the ground floor. Please contact a member of the ULTRASPEC team if this is necessary.

SDSU won't turn on

This has happened on a number of occasions and has always been due to a blown fuse. There are two different fuses to check. The first is in the mains plug in the power cable from the back of the SDSU PSU rack unit to the socket strip at the top of the electronics enclosure. The second is at the back of the SDSU PSU itself. To get at this, you will have to slide the SDSU PSU out of the electronics rack and open the lid. There are spare fuses in the ULTRASPEC electronics test equipment box in the ULTRASPEC cupboard in the dome.

CCD suddenly outputs nothing but blank, uniform or saturated frames

First, try another exposure. If this fails, try a software power off/on cycle of the SDSU PSU using the power off and power on buttons in usdriver. If this doesn't help, try rotating the rotator by approximately 180 degrees - it is possible some debris in the cryostat is shorting something and the rotation may dislodge it. If the above fails to fix the issue, it is most probably a problem with the SDSU PSU and it may be necessary to swap it for the spare, or to swap the SDSU controller boards - please contact a member of the ULTRASPEC team.

Pickup noise

This is evident as a series of horizontal, vertical, diagonal, or chevron-like lines in a bias frame. Removing it is a black art. The first step is to verify that the pattern is not simply an artifact of the image display device you are using - try zooming in to see if the pattern persists. If it does, estimate how serious a problem it is by determining the standard deviation - image display devices can make a very insignificant level of pickup noise (say, 0.5 counts) appear as if there is a serious problem with the CCD.

If you are determined to try to remove it, first try power cycling the SDSU controller and then allow it to settle down by taking some images for a while before measuring the readout noise again. If the pickup noise persists, then it is almost certainly due to a new noise source in the dome or a change to the earthing. Please speak to NARIT staff to see if any changes have been made to the mains supply, or its earth, and/or the way the dome/telescope motors are wired. Also check that no new cables have been connected to the cube which allow a new route between it and earth. Some things will definitely cause an increase in readout noise. For example, we know that the dehumidifier/air-con and the sliding monitor in the ULTRASPEC electronics rack, when open, are both sources of noise and must be switched off when observing. We also know that attaching the metal-sheathed fibres between the cube and the spectrograph significantly increased the readout noise on ULTRASPEC. Also, check that no part of the electronics rack is in contact with anything other than insulating material.

Can't remember how to plot setup windows in rtplot

A really useful trick when trying to determine the optimum window parameters to use is to take full-frame acquisition images of the field and then overlay the windows defined on usdriver on the images using rtplot. You can then see the windows move and change size/shape as you adjust their parameters on usdriver. I always forget how to do this, so here is a reminder:

SETUP - do you want to plot setup windows? [no]: y
SETWIN - name of setup windows file [setwin]:

Filter wheel won't initialise, returns an error, or will not change filter

Sometimes this can be solved by power-cycling the black filter wheel control box on the top shelf of the rack, so this should be the first thing to try.

If the problem persists, the most likely cause is that the filter wheel is slipping inside the housing, either because the door bolt is too loose or the central bolt is too loose. Turn off the filter wheel control box, open the filter wheel door and check that you cannot pull the wheel out of the housing. If you can, tighten the central bolt. Also check that the wheel rotates smoothly through an entire turn, without grinding on the edge. (Make sure the filter wheel control box is powered off, otherwise the wheel will be difficult to move.) If this grinding occurs, either try loosening the central bolt or replacing the entire wheel with one of the spares. Close the filter-wheel door, ensuring the washer is present on the door bolt, and firmly tighten the door bolt.

Lakeshore temperature monitoring won't work

This should be started automatically by start_uspec. If it doesn't work, e.g. no temperatures appear every 10 seconds in the Lakeshore window, you should first kill the current temperature monitoring process by typing ctrl-c in the Lakeshore xterm. Then, on the rack PC, simply type:

cd /home/observer/Lakeshore
python ls332.py --interval=10

If no temperatures appear immediately, the above operation has failed. You will then have to cancel the script and type python ls332.py --interval=10 again.

Networking and computing problems

Please refer to Paul Kerry's user guide.


If you experience problems with ULTRASPEC that you are unable to solve, or have any questions regarding any aspect of operation, you are encouraged to email all members of the team, which should ensure a speedy response. Contact details and specialities are listed below.

Vik Dhillon vik.dhillon@sheffield.ac.uk 0044-114-222-4528 general
Stuart Littlefair s.littlefair@sheffield.ac.uk 0044-114-222-4525 usdriver and usfinder
Paul Kerry p.kerry@sheffield.ac.uk 0044-114-222-3551 computing, networking and data archiving
Tom Marsh t.r.marsh@warwick.ac.uk 0044-247-657-4739 usdriver and pipeline reduction software

In an emergency or if your problem is urgent, please call any one of the numbers above.