|
|||
| Joint Astronomy Centre |
|
|
|
| Show document only |
The Telescope Systems Specialist (TSS)
will run the instrument up and down.
The TSS runs UIST from the "cassControl" gui. (Note - cassControlEng gives a similar Gui, though data are then saved to engineering directories.)
From the above window open the uist_oper screen. From here, datum the wheels and turn the black-body on. (Use the uist-ccs console to reboot the CCS [mechanisms - grism, filter wheels, etc.] if necessary.) To run-up UIST the TSS and observer simply run through the steps on the left of the window:
The run-down sequence is displayed in red (steps [6] to [9]).
IMPORTANT: In you are unsure about whether the array is enabled or disabled, check the LEDs on the controller in the dome. Most of the green LEDs should be OFF. Once the software has been run down, set UIST to dark from the uist_oper screen, switch off the black-body and arc lamps, and put the calibration unit in the beam. ENGINEERING: Instead of running cassControlEng, "ocs_up -simTel -eng" can be run from the command line, together with "uistMenu". NUKE: use this to kill drama and rtai processes if you are having problems running up.
UIST observing programmes are set up using the OT.
Your complete observing programme should be prepared from your home
institute and checked by your support scientist prior to your run
or to your program being initiated in the queue. A
general guide is available.
Type ukirtot to run-up the Observing
Tool or at the summit on Kauwa click on the
 The OT File dropdown menu. To create a new program, click on "New Program" and on "UKIRT_Template Library". From the templates expand the UIST folder as shown below. Choose a template suitable for your observations. Drag or copy and paste the required observation into your new program and edit to suit, paying attention to the advice in the Notes. Note there is a separate library of photometric standards.
 UIST template library (click for a full-sized image). The next section lists the contents of the imaging template observations. A table of DR recipes is also available. Note that the reduction recipes and observation sequences are intrinsically connected and if you change one make sure the other is still appropriate.
UIST observing programmes are run from the OM. The observer at the summit uses the Query Tool (QT )to access and extract observations from the database (observations which were previously prepared using the OT ). The QT allows the user to select observations based on their "observability", using constraints such as seeing, photometric requirements, dryness and of course source accessibility. A copy of the QT screen is shown below.
Click above for an expanded image An observing programme will consist of a list of "Minimum Schedulable Blocks", or MSBs. For example, a standard star and source observation might constitute an MSB. By entering a project ID in the QT (usually the project PATT number, e.g. u/03a/99), a list of MSBs can be displayed in the bottom half of the QT window. MSBs may then be selected and their components displayed on a second page of the QT window, as shown below.
Click above for an expanded image
Click above for an expanded image With the queue running, each observation will be sent automatically to a third window, the "Sequence Console", which shows the individual steps of the observation (the slew to the source, the configuration of the instrument, and the actual observations). From the sequencer the observer is finally ready to take data using the "run from highlight" button. The sequence console is shown below.
Click above for an expanded image A more general guide to using the OMP is also available.
Several data reduction recipes are provided for UIST with ORAC. The template observing sequences discussed above contain recipes appropriate to the associated observing mode. Please take care when changing DR recipes; many have specific requirements in terms of darks and flat fields, which must be acquired before a target observation is obtained and reduced on-line. Tables of available DR recipes - and links to detailed descriptions of them - are available. If a special reduction recipe would be useful to you, please contact your support scientist - we may be able to produce something specific to your needs, though we do need to be notified well in advance of your run at UKIRT. To run ORAC-DR while at the telescope simply type oracdr_uistThe software will then point to the current night's data directories. (If you wish to reduce, say, the previous nights data, you can specify the UT date on the command line, e.g. oracdr_uist 20001031 .) The above command should be followed by oracdr -loop flagTwo windows will open: an ORAC text display and - when the first exposure is completed - a GAIA window which will automatically display data frames. The pipeline will reduce the data as they are stored to disk, using the recipe name in the image header. The pipe-line is meant to run without interference from the observer. Thus, although you can use the various GAIA tools to examine images, the pipeline should not need to be stopped and/or restarted. If, however, you do need to re-reduce a block of data, this is possible with the command oracdr -loop flag -from 199or with oracdr -loop flag -list 199:210Specific calibration frames can also be used. For example, a 9-point jitter with a very short exposure should not use the "self-flat" from a JITTER_SELF_FLAT recipe, because of insufficient signal in the background for the flat-fielding. Instead, a separate sky-flat should first be acquired, and this later specified on the command line (when re-reducing the data), viz.: oracdr BRIGHT_POINT_SOURCE -list 31:40 -calib flat=flat_J_7Note this forces the DR to use the BRIGHT_POINT_SOURCE recipe and the frame "flat_J_7.sdf" for the flat-field division (BRIGHT_POINT_SOURCE would by default use the flat with the correct filter taken nearest to the target). Help on this and other ORAC-DR topics is available by typing oracdr -helpTo exit (or abort) ORACDR click on EXIT in the text log window, or type ctrl-c in the xterm. The command oracdr_nuke can be used to kill all DR-related processes, should you be having problems. Reducing data at your home institute To reduce data anywhere other than at UKIRT you must of course install orac-DR, which is part of the starlink collection. The software is (freely) available here: http://starlink.jach.hawaii.edu/. To run ORAC-DR you again specify the instrument with: oracdr_uistHowever, you must also tell ORAC-DR where the raw data are, and where the reduced data are to be written: setenv ORAC_DATA_IN /export/data/cdavis/myrawdata/ setenv ORAC_DATA_OUT `pwd`The second command tells ORAC-DR to write the reduced data to the current directory. Finally, reduce your data in blocks as described above using the -list option. Note that you must always reduce the array test observations taken at the start of each night first, since ORAC-DR uses the readnoise measurements and bad pix mask created from these observations. Usually there are about a dozen observations taken as part of the array tests - check the night's observing log for details. Coadds If more than one co-add is used, then users should note that the "co-added" frames are in fact averaged. In other words, the data values, or counts, in each raw frame correspond to the exposure time of one co-add. Similarly, the frames that comprise a jitter pattern are also averaged by ORAC-DR. However, please note that if a jitter sequence is repeated the mosaics that result from each jitter pattern are added to give the final, "master" mosaic. As an example; if you expose with 10secs x 2 coadds, and you repeat a nine-point jitter pattern three times, the integration time equivalent to the counts in each of the three mosaics will be 10 seconds. The integration time in the final, master mosaic (the sum of the three seperate mosaics) will then be 30 seconds. In all cases the integration time written to the fits header always reflects the averaging or addition of frames described above. Division by the integration time given in the header will always give data calibrated in counts/second.
The Basic Idea...In 2006 a second imaging-polarimetry mask with occulting wires was installed in the UIST slit wheel. Although this new mask was designed for coronagraphic imaging polarimetry, it can also be used for normal coronagraphic imaging (i.e. without the polarimetry prism and waveplate in the beam). The idea is that bright sources can be positioned behind either of two wires, so that longer exposures can be secured without saturating the array and without latency issues, bleeding, internal reflections, ghosting, etc. Under normal observing conditions (0.6-0.7 arcsec seeing, clear skies, etc.) 10-20 sec images can be obtained through the broad-band filters on 7-8th mag stars.
With Coronagraphic imaging, the user may use either a 6-pixel (0.7arcsec) or an 11-pixel (1.3 arcsec) wire. These are suspended 3/4 and 1/4 of the way along a 120"x20" rectangular aperture in the bottom half of the array. A second, similar-sized aperture in the top half of the array is available for sky-subtraction. Alternatively, point sources that appear in this aperture could be used for PSF fitting. The separation between these two apertures is ~48 arcsec (see above).
Position AngleThe position angle of the image plane can be orientated so that extended targets are placed orthogonal to the wire. For example, with a disk, jet or nebula orientated E-W you should use a position angle of 0 degs; with a disk orientated N-S you should use a position angle of -90 degs. Any angle between -90 and +90 degrees can be used, although acquisition will be easier if you use angles between 0 and -90! . To fully understand what's happening, see the figure below (you may need a shot of coffee first)...
From the above figure one can see that raw coronagraphic images are firstly flipped about a horizontal axis. They are then rotated by the position angle selected.
Offsets and Observing StrategyA suggested MSB is available in the UIST imaging template library. Since offsets must keep the source behind the occulting wire, and because both wires are only ~20 arcsec in length, separate sky frames will probably be needed to construct a flat-field image. Note that, regardless of position angle, offsets in "q" will always be along the wire. (An offset of q=+48 will put the source in the top aperture, though this is certainly not desirable with bright targets.)A possible sequence might consist of 11 frames, six sky frames interleaved with five images with the target behind the occulting wire. The frames with the source behind the wire might have p,q offsets of 0,0; 0,+0.6; 0,-0.6; etc. (the offsets being multiples of 0.12" pixels), while the sky frames could put the bright star between the two rectangular apertures, or well off of the array.
Imaging Acquisition: putting the bright target behind the wireIn the example MSB in the template library, a short (1sec) exposure is used to acquire the target. The instrument is run in "Movie mode", which means that frames are taken (though not saved) repeatedly so that the target can be placed behind the wire. This 1 sec exposure time is subsequently updated using a "UIST Imaging Iterator", so that longer exposures can be used for taking the actual science data. "Pick-object" is used with the Gaia Movie display; the posn of the target is "saved" and the source moved behind the wire by the telescope operator who uses UPICK. When you first slew to the target and start Movie, if you don't immediately see the target, ask the telescope operator to move "up 10" and/or "down 10" while you are running Movie. When you can see the target, then use pick-object and upick to place it behind the wire. By default the acquisition process will put the source behind the 6-pixel (0.7 arcsec) wire. If the wider occultor is required, the telescope operator should apply a "left 62.6 arcsec" after the slew and initial acquisition. This will move the target from the thin wire to the thick wire; the position can be fine-tuned with subsequent small left/right offsets (while still running Movie).
Data ReductionA dedicated pipeline recipe is pending. |
icon on the tool bar.
A small window will appear containing a photo of UKIRT, as well as a welcome
window; dismiss the latter and use the former to either fetch existing programs
from the database using the "Observing Database" dropdown menu, or to create new
programs, using the "File" dropdown menu. The latter is shown in the image below.