The NIRC2 web pages have been reformatted and reorganized to conform to the Keck instrument page standards. Feedback is welcome.
NIRC2 was opened up and serviced Sep. 17. The lead screw for the camera stage was inspected. The preload on the nut was reduced by removing one of the two wave washers. Testing when warm under vacuum showed that the stage was moving freely. NIRC2 is now closed up and has been vacuum pumped for 24 hrs. The cold heads have been turned on and cool down has started at 16:02 HST Sep. 18.
A new startup script has been released for NIRC2, which will automatically launch some of the most often used tools and GUIs, including the PIG (program identification gui). The PIG is a new tool that allows you to easily flag which data are yours on split nights. An example of the PIG is shown (for NIRSPEC; it is used for all instruments). A single click allows you to change OBSERVER names and data directory. An edit field allows you to change OBSERVER, if the default (from the telescope schedule) is not what you want. Please use the PIG while observing. It is your friend.
We have decided to warm up NIRC2 in order to take advantage of an opportune window in the schedule this month to fix the camera stage problem that we've been experiencing. The CCRs were turned off around noon today. The dewar is expected to be ready to open for service Monday, 17 September. NIRC2 should be cooled and fully operational by Sep. 29.
We have been experiencing some difficulty with moving the camera stage to the wide camera. As a precautionary measure, observers are strongly advised not to use the wide camera.We will attempt to trouble-shoot the problem when NIRC2 is off sky.
We now have a library of imaging flats and darks (some graciously provided by A. Kraus) available here. More can be added as they become available.
In the spirit of giving this holiday season, US Space Command recently increased the number of LGSAO targets that observers are permitted to submit for LGSAO observations. The new maximum per night is 130 total targets. For split nights, each half night observing team is allocated 65 targets.
NIRC2 has reached equilibrium operating temperatures. Cold head speeds are being tuned, but preliminary checks indicate that all systems are operating normally. More information on the newly installed filters is available on the updated filters page.
NIRC2 was opened up and serviced Sep. 05-06. Seven new filters were installed: z, Y, L-wide, Pa-gamma, He IA (10,830A), Br-alpha, and Br-alpha continuum. The L-undersize and a duplicate Br-gamma filter were removed. The cold heads were purged. NIRC2 is now closed up and has been vacuum pumped for 24 hrs. The cold heads have been turned on and cool down has started at 16:07 HST Sep. 07.
Warm up of NIRC2 has begun for the service mission led by PI Keith Matthews to install new filters. An L filter, a Y filter, which was procured with generous partial funding from M. Liu, and a number of narrow-band filters will be added. The extra Br-gamma filter and the L-undersize filter will be removed. NIRC2 will be opened and filters installed Sep. 6-8. NIRC2 should be cooled and fully operational by Sep. 16.
We have a new set of data acquisition scripts that improve on-sky observing efficiency by reducing delays in status checks and time waiting for data writing to complete. Some minor modifications were also made to quicklook to handle more rapid image exposures. The time saved by the new scripts is estimated to be about 15-45 minutes per night, depending on the nature of your program. Unfortunately, the new scripts have also been found to introduce a "side effect" that causes the detector (Alad) server to crash, on average, about once a night, which requires ~5 min to recover. We will continue to investigate these server crashes, but in the mean time if you wish to use the new scripts, please let your support astronomer know.
|Starting with the June 2010 NIRC2 run, we ask all observers to start up their NIRC2 control software within VNC desktops. Virtual Network Computing (VNC) is a technology that allows windows to be shared with observers at other computers and has been used successfully for years at Keck to provide mainland observers with access to Keck instrument controls. By expanding the use of VNC to all observers, we will thus have a single startup procedure for observers to follow regardless of whether or not they will operate with mainland observers. Operating under VNC also makes it easier for support staff to assist observers with troubleshooting and allows our observing assistants to monitor the status of observations during the night. Your support astronomer will be happy to assist you with starting your NIRC2 software under VNC.|
|To take advantage of the color-map speed up available when quicklook is run from within an 8-bit display, the VNC configuration has been changed to use an 8-bit (tan background) display for the center screen. Users will also notice that xterms have all been converted to black-and-white to accomodate this change. The primary advantage of this change will be experienced when users apply right-mouse-button color stretch to tease out faint features. The improvement should help with rapid cadence programs such as companion-search survey programs.|
We have discovered an unusual aspect of data collected with NIRC2 in
multiple correlated double-sampling (MCDS) mode. The peculiarity is
seen most easily in dark frames.
Figure 1 shows a
histogram, with the expected Gausian distribution, of pixel values
across a NIRC2 dark. The dark shown in figure 1 was taken in single
correlated double sampling (CDS) mode.
Figure 2 shows
a similar histogram of a dark taken in MCDS mode. Note the
excess of zero-valued pixels.
We have checked darks going back seven years, and with varying numbers of samples, and we see the same effect in all these data. Therefore, we believe that this phenomenon has existed since NIRC2 commissioned and occurs for all MCDS frames, regardless of the number of samples sepcified. We will continue to look at this problem to see if we can determine the root cause, and to see if there is a significant effect on data quality resulting from this anomaly.
Users of the wide camera, observing at Kp (or longward of Kp), please
be aware that a 'glow' now appears in the lower right portion of the
detector. See jpeg image. The fits file associated
with this image can be downloaded by clicking here.
This effect began, we believe, around August, 2009, and may be the result of a new optic that was installed on the AO bench (a replacement IR dichroic) around that time. We are working to better characterize, and hopefully correct, this effect. The effect produces a less than 1% increase in flux in that area and may be removable by flat fielding.
For observers who might be new to observing in the infrared: The harmful effects of over-exposing with NIRC2 are shown in figure 1. Note that, unlike a CCD (which will "flat top" if over-exposed), the correlated double sampling (CDS) mechanism inherent in IR readout systems, will result in a "roll over" phenomenon. In this example, the total DN reaches approximately 13000 at which point the measured signal begins decreasing.
A spreadsheet containing the the data values for the passband curves that appear on the NIRC2 filters page is now available on that page. See Note #10.
Along with recommended integration times, the dome flat calibration instructions page has been update to include a step-by-step procedure. Please consult this procedure when taking flats unattended (e.g., morning dome flats).
Over the past 1-2 years, the NIRC2 slit stage has faulted on several occasions when driven to locations near its negative limit. For this reason, we are restricting use of that stage to exclude use of the fine pin-hole mask. All other positions for that mask (slits 10-through-160 for spectroscopy, coronagraphic spots 100 through 2000, and the coarse pin-hole mask) are available for use. We will continue to investigate this issue and apologize for the inconvenience.
Observers using vertical angle mode, who are intending a fixed pupil, for example users of aperture masking or angular differential imaging (ADI), should be aware that a tracking shift in the pupil plane of order 0.4 degrees occurs when an object being observed in vertical angle mode transits near zenith. This effect is likely related to the difference between true vertical and the as-built telescope Y axis, as the offset is equal to the difference between PARANG and PARANTEL. A correction equal to that difference must also be applied to recover absolute astrometry. This plot characterizes the jump.
A problem with the NIRC2 detector readout system occurred on Wednesday night, June 18th, 2008. The root cause was traced to a failed transputer board in the detector system electronics rack. That board has been replaced and since that repair mission, NIRC2 has been in use on five science nights without a recurrence of the problem. Several efforts are underway to improve our preparedness should a similar problem occur in the future, including the configuration of a hot-swappable host computer system.
An Image Quality comparison page has been been generated for collecting observers' before and after experiences with NIRC2 since the upgrade of the AO Wave Front Controller.
As of April 24, 2008, an LGS mode which allows for differential motion between the laser and the tip-tilt reference is available for shared risk. Limiting rates and magnitudes for this new mode, as well as all other nonsidereal AO modes, are provided in a summary table. Contact Randy or Al for details.
The Astrometry Page has been revised, including new information related to the NIRC2 position angle.
The procedure for observing M15 for astrometric calibration
has been added to the
If you use the procedure, please consider contributing your calibration
frames to the Observatory (via your Support Astronomer) for general use
by the community.
|Since the commissioning of NGWFC, many have wondered: Under what conditions is it better to use NGS over LGS? Please see KAON 489 figure 14 for details, but the short answer is "When brighter than 14th and closer than 10 arcseconds, use NGS."|
The IDL code to remove geometric distortion (graciously provided by Brian Cameron) has been added to the NIRC2 web page. Go to the Dewarp Utility Page.
Strehl-vs-magnitude and related performance statistics for the upgraded AO system have been characterized.
The NIRC2 Adaptive Optics feed has been upgraded. Performance improvement is still being quantified, but in the mean time, check out this snapshot of improved performance at J from Mike Liu's April 3rd SSC presentation.
At the CfAO Retreat held in Santa Cruz March 26th, an informal meeting was held by NIRC2 observers interested in precise astrometry. The collaboration has resulted in a report, recommended calibration fields, and a dewarp application. Once these are finalized they will appear on this page. In the mean time, email firstname.lastname@example.org if you desire preliminary versions of this material.
Please check out the new NIRC2 home page. It is a work in progress, but comments are welcome.
Based on photometric data gathered in April of 2004 the zero points have been updated. The values are included in the list of filters and in the NIRC2 manual. There was improvement in both the zero points and the background levels from the initial commissioning measurements, likely the result of cleaner optics on the AO bench.
The three mirrors in the AO rotator were recoated with silver (2 of the 3 surfaces were previously Al.) and reinstalled in March 04. The rotator, which is often referred to as the K mirror, was subsequently realigned to the optical axis of the telescope and to the pupil of the optical system. One requirement of the realignment effort was to minimize the pupil nutation as a function of rotator angle, which has been a significant problem in the past. The realignment effort met the requirements and was deemed successful with the pupil nutation now only 10cm on the primary (peak to valley). These changes will have several likely benefits to NIRC2 observers,
An accurate and consistent method of measuring image quality on NIRC2 has been developed by Marcos van Dam, WMKO AO Scientist. The tool is available from the NIRC2 user interface menu and users are encouraged to give it a try. Instructions for its use are available as a web document.
The NIRC2 dewar was warmed to ambient temperature and opened in late August of 2003, the first time since being delivered to WMKO in June of 2001. The primary purpose of the service mission was to install recently procured narrow-band filters. The successful effort was led by PI, Keith Mathews of CalTech. One prerequisite to going forth with the service efforts was the development of the Keck II AO enclosure into a clean "ish" room. The clean room project was led by Craig Nance . He and the summit facilities group worked hard to enable this important work on NIRC2 to be accomplished.
Preliminary characterization has produced filter wavelength information that is now available on the NIRC2 filter page. Full characterization of the transmission profiles is yet to be completed.
A bug in the software was found that was hard-wiring the pixel scale to that of the wide-field camera. This has been fixed, so that the plate scale gets properly read from the FITS image keyword. Telescope movement in all three cameras was confirmed, and moving the telescope using an image from one camera while a different camera was currently in use was also verified.
You can still, of course, use one of the other telescope move commands, including "mov", "pxy", etc.
Currently the tint value is set with full precision, and the tint command prints it out to 4 decimal places.
Like NIRSPEC's version, the NIRC-2 "Move Tel" command does not work reliably. We have added debugging lines to the code to try to track down this problem, but meanwhile you may want to rely on the command-line command "mov" to move a target from one (x,y) position to another.
Update, 2002-Dec-25: A bug causing failure of the "Move Tel" command was found and fixed during December engineering. (see above.)
Work on the Strehl calculator proceeds. It now gets the pixel scale and filter bandpass information from the image headers, rather then requiring the observer to type this in each time. We will be adding better theoretical PSFs in the future, using the correct NIRC-2 pupil mask where appropriate.
The tool is available on-line using ION, IDL On the Net , which was recently installed on the Keck public web server. Please report any problems or suggestions associated with using this tool. .
Because NIRC-2 currently has a somewhat limited inventory of filters, observers may wish to know what may be in store for the future. We are providing a list of filters that have been ordered, and will hopefully make their way into the NIRC-2 filter wheels. Note, however, that there is no guarantee that all of these filters will get successfully made and delivered to the NIRC-2 team at Caltech.
The "n=#" argument can be placed anywhere, e.g. "bxy5 n=3 1.3" will take three exposures at each of five dither positions in a 1.3 x 1.3 arcsec box. ("1.3" is the step size, not the size of the entire pattern.) Similarly, "bxy4 1.2 2.7 n=4" will take four exposures in each of four positions in a 2.4 x 5.4 arcsec rectangular pattern.
Commissioning is still not complete, and not all observing modes have been adequately tested. Also, Keck staff are still receiving training on the instrument. Thus, the early shared risk use of NIRC2 will have limitations applied. The spectroscopy mode of instrument is not fully tested and will not be supported in 2001B, especially since those planning spectroscopy programs will likely choose to stick with NIRSPEC. The coronography modes will also not be available during the pre-commissioned use of NIRC2. With it's three cameras, NIRC2 offers field of view advantages over the NIRSPEC SCAM detector with choices of 10, 20, and 40 arcsec FOV. NIRC2 has fewer optics in the path and is expected to have better sensitivity in most situations. Please see NIRC2 specifications and a comparison of NIRC2 to NIRSPAO for more information on the trade-offs between the two instruments.
M8 in JHK Neptune in K
NIRC-2 being lowered into Keck II AO enclosure.
PI Keith Matthew's of CalTech prepares NIRC-2 for placement, Bob Goodrich assists.
NIRC2 workers imaged at K (2.2 microns) with NIRC2's pupil imaging capability.
Perhaps it is the first use of a 10 meter telescope to image human beings.
From left to right, Randy Campbell, Keith Matthews, Eiichi Egami, James Larkin.