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NOAO Newsletter - Kitt Peak National Observatory - December 1997 - Number 52

Phoenix Status

The regularly scheduled use of Phoenix for 1-5 mum high-resolution spectroscopy began in January 1997. Since that time, spectra of objects of magnitude 7-8 have been routinely obtained in the 1.5-2.5 mum region (see Figure). While this performance is impressive, it can be significantly improved. The collimator imaging in Phoenix is currently limiting the sensitivity. The best collimator focus produces a spectral resolution of about 60,000 and a spatial width of nearly 5" on the 2.1-m telescope. Throughout the 1-2.5 mum region, the detector is the predominant source of noise, and having the spectrum spread out over 5 to 10 times the optimum number of pixels severely degrades performance at limiting magnitudes. Optical and mechanical modeling points to the grating as the cause of the problem. The grating is a replica grating with epoxy replication material on a silicon substrate. The very different coefficients of thermal expansion between these two materials warp the grating when it is cold. A project is now underway to characterize the epoxy material and to replace the current replica with one that will remain flat under cryogenic conditions.

Caption: Spectrum of the symbotic star V1329 Cyg (H = 7.3) over the range 6401-6430-1 (1.5552-1.5622 m), showing the 30 CO band head and numerous atomic transitions. The unmarked lines are CO lines in the 3-0 band. This spectrum is a 1200s integration at the KPNO 2.1-m telescope. The bright standard HR 8621 is shown for comparison; the difference in radial velocities of the two stars is easily seen.

The Phoenix Web page describes two other instrument problems. One is that the mechanisms still move relatively slowly and occasionally have positioning problems. We now realize that this problem is largely due to the insufficient resolution of the encoders selected. A project has been started to replace the encoders with more suitable models. The other problem reported is that the slit viewer optics are out of focus. This problem resulted from chromatic optics in the slit viewer assembly. New optics have arrived and final installation and testing is underway.

Graphical User Interface (GUI)

For several months we have been testing a graphical interface to the Phoenix Wildfire software. This now is ready for general use. Observers who have used the GUI find it makes the operation of the instrument much more transparent. The GUI also has a number of user-friendly features unavailable through the Wildfire command line code. For instance, the grating equation is solved for the encoder position by the GUI when the wavenumber or wavelength is entered. The GUI features a graphical light path with the currently selected positions of the wheels labeled. A countdown clock pops up during integrations.

Whereabouts for the September 1998-January 1999 Scheduling Period

NOAO long range planning calls for Phoenix to be shared between CTIO and KPNO. The tentative schedule was for Phoenix to be shipped for its first visit to CTIO in August 1998. However, the long lead time for the new grating suggests that the replacement grating will not arrive until sometime late in 1998. Since there is limited clean room space at La Serena and grating replacement involves major work on the instrument, the shipment date to CTIO has been delayed at least six months. As a result, Phoenix will be available on the KPNO 2.1m and 4-m telescopes through the end of 1998.

Web Page Changes

Jeff Valenti has joined the Phoenix team as a NOAO post-doctoral fellow. Among other responsibilities, Jeff will be working on new material for the Phoenix web page, including an updated user manual reflecting the GUI user interface and a PostScript version of the 1-5 mum FTS He-Ne hollow cathode atlas. These changes will appear over the next few months.

Ken Hinkle, Dick Joyce, Jeff Valenti

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