-----Problem Recovery-----

-----Operations and Observing-----

-----Adaptive Optics Observing----

First, read the available information on the Web and check with CARA staff in Waimea that the instrument is released and ready for use. Go to blue background on hanauma screen and hold down the right mouse button to get the pull-down menu. Go to "NIRSPEC Control Menu", follow arrow to right and release on "Start NIRSPEC Control Software". A text window will appear, with a startup script running in it. Read and follow the instructions in the Startup Script.

YES! The NIRSPEC software has a problem with continuous consumption of memory swap space on the host computer. If you leave NIRSPEC running during the day, you greatly increase your chances of a crash during the following night due to the host computer running out of swap space. Shutting down the software in the normal manner releases most of the consumed swap space. Shutting down and restarting also assures you a fresh start, in a new data directory. So do yourself a favor, and shut down NIRSPEC before you leave at the end of the night.

It is OK to initialize mechanisms upon startup unless this is a recovery from a crash.

If you are recovering from a crash and you need to take calibration lamp exposures at the present grating and slit settings, then do not init during the startup script. Instead, wait until the startup script is complete, then use the "Init" menu (on XNIRSPEC, left-click on "Engineer" then on "Motors", then on "Init" to get the "Init" menu) to init only the Calibration unit cover and the Calibration lamp mirror (you can do them both at once) by clicking on those two entries, then "Init" and "Dismiss". Take your lamp exposures using XNIRSPEC only (NOT the EFS GUI!), then init the remaining mechanisms from the "Init" menu. Initializing the image rotator causes a slight vibration that can sometimes make the gratings move slightly, so don't init the rotator until after you've taken your lamps. Remember that after you init the gratings and slit you will need to take new calibration lamps, even if you set them back to the same settings they were at before (but now you can use the EFS GUI if you want).

Bring NIRSPEC up in Daytime mode when you start up in the afternoon or early evening. You should change to Nighttime mode when you are ready to have the OA focus the telescope and begin observing.

To change to Nighttime mode, put the mouse pointer on the blue background, hold down the right button, go into the "NIRSPEC Control Menu, and let up on "Enable Night-time Mode". If you are restarting during the night, you can go directly into nighttime mode by choosing that option in the startup script. For more details, see the Start of Night Procedure

Drag the screen to a better position if necessary. Go to the XNIRSPEC Instrument Status screen, click on IROT and click TRACKING ON; this starts the communication between the telescope software and the NIRSPEC rotator. Then go to the IROT GUI, type in 0.0 in the Physical Angle entry window and click on SET. For more details, see the Start of Night Procedure

Yes. Go to the blue background, hold down the right mouse button and under NIRSPEC Control Menu, go down to the last entry, "**Close NIRSPEC & Stop Software" and release on that item. This will close the Dust Cover, (after a short delay) put in the "BLANK" filter, and then stop the software and close most of the displays. Those that do not disappear (the Image Rotator GUI and the Echelle Format Simulator or EFS GUI) can be closed by a right click on the top bar. Also, the Rotator GUI has a "Quit" button at the bottom, and the EFS GUI has a "Quit" choice under the FILE menu.

Don't panic. Go to the blue background and under the NIRSPEC Control Menu do Restart XNIRSPEC. Although the exposure timer will not re-activate, the current exposure will complete. So just wait. If you can remember what happened and what you did immediately prior to XNIRSPEC disappearing, please send an email with the information to dsprayberry@keck.hawaii.edu

On the same monitor, look for an iconified window with the same name as the one that has frozen; open that window, hit Enter a couple of times, and enter the command "exit". The frozen window should vanish. Then quit the other QuickLook window from the FILE menu using the Quit All choice. Go to the blue screen and under Control Menu do Restart QuickLook. This sometimes occurs if too many sub-options are active.

As a rule, it is a Very Good Idea to have only one popup open at a time. It is also a Very Good Idea to dismiss each popup immediately as soon as you're done with it. Not only does this avoid confusion about which one is "alive" but it also may reduce the chances of a crash.

There is a known conflict between the "Diagonal Cut" function (available under the PLOT menu) and the "Move Telescope" function. If you have started the "Diagonal Cut" function and not dismissed the popup since the last time you used "Move Telescope," then the "Move Telescope" will not work. The behavior is that "Move Telescope" gives you the first prompt ("Click Mouse on Start Point") but never comes back with the second prompt ("Click Mouse on End Point"). You can restore the "Move Telescope" by dismissing the "Diagonal Cut" popup; click the "Done" button on that popup to dismiss it.

There may on rare occasions be something more serious wrong. If dismissing the "Diagonal Cut" popup does not restore the "Move Telescope" function, then kill both QuickLook displays (using the "Quit All" or "Exit" options under the FILE menu) and from the background Openwindows menu select "NIRSPEC Control Menu -> Restart QuickLook."

As a rule, it is a Very Good Idea to have only one popup open at a time. It is also a Very Good Idea to dismiss each popup immediately as soon as you're done with it. Not only does this avoid confusion about which one is "alive" but it also may reduce the chances of a crash.

The image rotator needs to be re-initialized. See this procedure for instructions on how to do that.

You should shut down the NIRSPEC software and restart within ONE HOUR. This warning is meant to give you time to complete your current observing sequence and shut down before NIRSPEC crashes due to a lack of memory swap space. If you are running an observing sequence from the EFS, finish that sequence. If you have not already taken a set of calibration lamp exposures at your current instrument configuration, then take the calibrations before shutting down. But do shut down and restart as soon as your current sequence and calibrations are done. DO NOT ignore this warning!

If the product of "itime" x "coadds" is less than 1 sec, the image will usually fail to display in the QuickLook, even though the image has been taken. You can still view the image with using the FILE menu and the Open entry in that menu. To ensure an image with short itime shows up in QuickLook, always choose coadds such that the product is > 1 sec.

For the SPEC detector, the minimum itime is 0.25 seconds in CDS mode. For the SCAM detector, the minimum itime is 0.1 seconds in CDS mode. In MCDS mode, scale these values by the number of reads.

To stay below 1% non-linearity in CDS or MCDS mode, keep the counts below: 18,000 DN for the SPEC (conversion = 5 e/DN); and 25,000 DN for the SCAM (conversion = 4 e/DN), BUT, see also the question about persistence below.

Try to avoid saturation and over-exposure. In particular, on the SPEC detector, try to avoid exposing to levels above 10,000 DN per coadd in CDS or MCDS sampling mode. Your data will still be within the 1% linearity regime between 10,000 and 18,000 DN per coadd, but the more you fill the wells the longer the persistence will persist.

Experience shows that repeated readouts will reduce the persistence considerably. There is a command called "flush" that can be run from any terminal window with a "waimea>" prompt that will automatically take a test image with a large number of coadds at the minimum integration time. The flush command accepts an optional parameter of the number of readouts to coadd; the default value is 50. For severe persistence you may need to set this value to 100 or more. BE SURE that you do NOT have a bright star on the slit or a calibration lamp turned on when you run flush!

There is also a component of the persistence that behaves like increased dark current. This component seems to be reduced only by integration time on the detector. If bad persistence occurs, and the "flush" command does not completely remove it, put in the BLANK in the filter wheel and take several long (300 s) darks. Examine each dark carefully before starting the next, to see if the persistence has been acceptably removed.

For more information, please see this web page.

The Thin blocker is a thin piece of PK50 glass used to block thermal emission. The short-wavelength wide-bandwidth spectroscopic filters have small leaks in the thermal IR, so the Thin blocker is needed with them. Here's the rule:

• Use the Thin blocker with Nirspec-1 through Nirspec-6.
• Use the Open position with all other filters.
• NOTE: the Thin blocker can be used with Nirspec-7, but it will cut off the long-wavelength end of the Nirspec-7 passband.

If there is a menu entry for a Thick blocker, ignore it. The former Thick blocker has been removed and replaced with the AO pupil stop.

The center is at pixel (132,126).

Go to the TEL menu on the SCAM QuickLook panel, and select the "Move Telescope" entry in that menu. Left-Click once on the star and then left-click once again on pixel (132,126).

Exposures of 30-60 s are easily obtained in the short wavelengths (Nirspec-3 (very similar to J) and Nirspec-5 (a broad H)); 15 s or so is good for K, KL and Nirspec-7.

You do better by taking the difference of two slightly displaced images: use the SNAPI button on the SCAM control panel of XNIRSPEC. You can go much deeper by doing a 9-point dither pattern: use the BOX9 button on the SCAM control panel of XNIRSPEC. In both cases, the telescope is returned to its original position after the dithers are done so that you can use Move Tel on the displayed image.

You must take arcs and flats BEFORE you change the settings of either of the two Gratings or the Slit wheel.

A useful observing pattern is: setup1, object, cal star, arcs, setup 2, object, cal star, arcs, etc.

Another option is: setup 1, object, arcs, setup 2, object, arcs, etc. then repeat the sequence for the Cal star.

Yes! Spectral shifts of up to 20 pixels may occur because of vibration from image rotator when observing in slit P.A. mode or slewing to a new rotator angle. Night sky OH lines inherent to the spectra may be usedfor internal calibration if there is a discrepancy with the observed arc lamp lines. If absolute confidence in the lamp exposures is required, it is advisable to take a lamp sequence before every telescope slew when observing in PA mode (i.e., with the rotator tracking sky PA).

Alternatively, observing with the rotator stationary can eliminate the movement of the echelle grating by eliminating image rotator motion and hence image rotator vibration.

The Cal star is needed to remove the atmospheric extinction (by division). The best Cal star is one with no (or very weak) intrinsic spectral features. Isolated features can be interpolated. A0V stars are useful (mainly in J and K); O stars are helpful for H-band where A-stars have too many lines. It is best to keep the airmass difference at 0.1 or less.

Each image taken is automatically displayed. Use a NOD2 pattern and take the difference of the two exposures using the Sdiff entry under the MATH menu in QuickLook. The Sdiff routine subtracts the most recent image from the one before (e.g., if the two most recent images are 34 and 35, Sdiff displays 34 minus 35), and the Arithmetic option allows any arbitrary image pair to be subtracted. Under the PLOT menu on QuickLook, you can use the Horizontal, Vertical or Diagonal entries to graph a cut through the displayed image.

Depending on whether NIRSPEC is behind the AO system or not, and on what filter and blocker combination is used, echelle spectra may exhibit an underlying sinusoidal ripple. The effect is particularly pronounced in AO mode, where the slow, almost parallel beam (f/160) induces a Fabry-Perot pattern as it encounters the dewar window. In non-AO mode, interference occurs between the NIRSPEC order sorting filters and their associated blockers near the pupil plane. This effect can be almost completely removed with the application of a fourier domain filter, such as hanning. In non-AO mode, the fringing effect is usually less than a few percent. This may be reduced by taking out the long wavelength blocker, although care should be taken to characterize the impact of the red leak if the blocker is out.

The main performance difference is lower throughput (down by a factor of 3 or 4 in imaging mode with the AO system, down by a factor of 5 to 10 in spectroscopic mode). The benefit, of course, is much higher spatial resolution: the SCAM plate scale is 0.0168 arcsec/pixel with the AO system, compared to 0.172 without.

The main observing limitation is that NIRSPEC cannot be used at wavelengths longer than 2.6 microns when it is behind the AO system. The AO pupil stop is mounted in the same filter wheel that contains the longer wavelength filters, so it is not possible to have both the pupil stop and a long wavelength filter in the beam at the same time. Take a look at the Specifications page. Only the filters listed as being in Filter Wheel 2 can be used with the AO system.

There is a new page of observing procedures and notes for NIRSPEC+AO. You can find it here. We hope to be improving this page over time, so please check it before every NIRSPEC+AO run to keep up with the latest developments.

It is possible to set the NIRSPEC rotator at a fixed angle other than the default of 0.0, to allow setting the slit PA independently of the AO system rotator setting. This mode can be useful to observers who need to select an arbitrary slit PA, but who also have a large enough separation between their science target and AO guide star that the AO rotator setting is dictated by the needs of the AO system. You can find instructions in the use of this mode in the notes on AO observing, under the heading "Using the NIRSPEC Rotator to set PA."

It is not possible to use NIRSPEC's rotator to track a PA on the sky with NIRSPEC behind the AO system. That function can be performed only by the AO system rotator.