Sigma QUick Infrared Camera User Manual download pdf (Page 10)

parameters. The observing modes include: grab (which defines an exposure as a single on-source image), chop (which

takes on- and off-source images by moving the telescope's secondary mirror), nod (which takes an on- and off-source

image by moving the telescope), and chop-nod (which takes one on-source chop pair and one off-source chop pair of

images). The chop signal is TTL while the nod signal can either be a TTL output (necessary at MLOF) or triggered over

the network (necessary at the IRTF). Chop sets are transferred to the host computer as 320 x 480 pixel images and then

saved as 320 x 240 pixel fits images and extensions. Nod images are transferred and saved one image set at a time.

Within the Observing Parameters window, there are two methods for setting the total on-source integration time, frame

time (length of an observation coadded in hardware), chop frequency, chop wait (time needed to allow the secondary to

settle), and nod wait (the time needed to move the telescope). The first mode allows the user to input the parameters in

units of seconds. The second method, mostly used for laboratory testing purposes, allows the user to input the parameters

in units of the frame time. Before the parameters are set in the hardware, they are optimized and re-displayed to allow

the user to readjust before exposing.

When the observing parameters are set, MIRSI updates the values on the PCI controller board through a series of

registers used by the device drivers to send and receive information. The ``Voodoo and Device Driver Programmer's

Reference Manual'' by Scott Streit at San Diego State University (16 August 2000) provides a description of the software

communication with the PCI controller board. Many of the exposure parameters are set using a Manual Command

by the DSP.

Switching between spectroscopic and imaging mode as well as selecting filters is performed in panels located in MIRSI's

Observing Parameters window. In the main motor control panel, all positions are pre-programmed, and upon selection of

a grism or filter, the appropriate aperture is moved into position. For special observing strategies and test purposes, the

grism, discrete filter, and aperture wheels can be controlled individually from panels hidden via tabs under the main

motor control panel. When using the CVF, an observer enters or selects a wavelength in the CVF position list. The

software calculates the closest position to within one motor step and updates the observer's wavelength request.

Other windows that the observer may access from the GUI main window include the Temperature Control, Offset

Control, Controller Setup, and Target Selection windows. From the Temperature Control window, the observer will

monitor the temperatures of the array stage, optics box, nitrogen shield, floating shield, and ambient air. The array stage

heater may be activated, and its temperature may be set from this window. Temperatures are recorded ever minute when

the monitors are active.

Dithering and mosaic patterns are accessed from the Offset Command window. Observers may select one of the

predefined patterns or employ their own patterns for mapping their favorite field. When centering a source in the field,

the observer may send and receive offsets from the Offset Window by interactively selecting the position of the source in

the image displayed in ds9. Target information is stored in lists in the Target window for use in writing image header

information. Targets may be selected from a user defined list which may be updated by the software. The Controller

Setup window is used to download the timing file to the DSP, set array dimensions, and set the image resolution.

6. FIRST LIGHT

On December 5, 2001, MIRSI detected first light from astronomical sources at the 60-inch telescope at the Mt. Lemmon

Observing Facility (MLOF) operated by the University of Minnesota and Steward Observatory in Tucson, AZ (see

Figure 3). Narrow band images of galactic, extragalactic, and solar system bodies were acquired over five nights. The

first light observations were made using an engineering grade detector from Raytheon/SBRC. The science grade array

was installed 12 July 2002, and all future observing runs will be made with the science grade array.

MIRSI’s optics were optimized for the IRTF’s f/35 beam. For MIRSI’s first light run, MIRSI's f/ratio conversion optics

for the MLOF (f/15) were unavailable. The f/ratio mis-match caused severe underutilization of the MLOF primary for

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Sigma QUick Infrared Camera User Manual Page 10