Instrument and Telescopes Used in the Hardersen IRTF NIR Asteroid Reflectance Spectra Bundle
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Date: 2025-04-21
The information was extracted from the sources cited below.

SpeX 
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Introduction 
SpeX is a medium-resolution 0.7-5.3 micron spectrograph built at the Institute for Astronomy (IfA), for the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. The instrument saw first light in May 2000 and was upgraded in 2014. The primary reason for the upgrade was to replace obsolete array control and instrument control electronics although the opportunity was taken to upgrade the arrays as well. The Raytheon Aladdin 3 1024x1024 InSb array in the spectrograph was replaced by a Teledyne 2048x2048 Hawaii-2RG array and the engineering grade Aladdin 2 512x512 InSb array in the IR slit viewer was replaced by the science grade Aladdin 3 array from the spectrograph (only a 512x512 quadrant is used). Astronomical Research Cameras, Inc. controllers run both arrays. Most of the warm electronic hardware was also replaced: motors, motor controllers, Hall effect sensor control, power supplies, computers and GUIs. For most observing programs guiding is done with the IR slit viewer on spillover flux from the object in the slit. However, for optically visible objects selectable IR transmitting and visible reflecting dichroics in SpeX feed the MORIS CCD camera attached to the side of SpeX to enable guiding in the visible. MORIS is also used as a scientific CCD imager and for simultaneous optical and IR observations in conjunction with SpeX. The upgrade has resulted in increased simultaneous (one shot) wavelength coverage in all spectral modes and improved spectral sensitivity (0.25-0.5 mags). Due to the faster computers instrument control is more robust and there are fewer software problems. SpeX was originally funded by the National Science Foundation (NSF) in 1996 with additional funding from NASA for the detector arrays in 1998. The SpeX Upgrade was funded by NSF in 2008 but delays in procurement of a science grade H2RG array delayed completion until 2014. 
New Spex (Aug 2014-) 
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• Spectrograph pixel size 0.10" (18 microns) 
• Slit widths: 0.3", 0.5", 0.8", 1.6" and 3.0" 
• PRISM 0.7-2.52 micron, R~200 matched to 0.3x15" slit or 0.3x60" slit • SXD 0.7-2.55 micron, R~2000 matched to 0.3x15" slit 
• LXD_short 1.67-4.2 micron, R~2500 matched to 0.3x15" slit 
• LXD_long 1.98-5.3 micron, R~2500 matched to 0.3x15" slit 
• Single order short 0.9-2.4 micron, R~2000 matched to a 0.3x60" slit • Single order long 3.1-5.3 micron, R~2500 matched to a 0.3x60" slit 
• Slit viewer: 60x60" FOV at 0.12" per pixel, selection of filters available (no change) 
Old SpeX (2000-Jan 2014) 
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• Spectrograph pixel size 0.15" (27 microns) 
• Slit widths: 0.3", 0.5", 0.8", 1.6" and 3.0" 
• PRISM 0.8-2.5 micron, R~200 matched to 0.3x15" slit or 0.3x60" slit • SXD 0.8-2.4 micron, R~2000 matched to 0.3x15" slit 
• LXD1.9 1.95-4.2 micron, R~2500 matched to 0.3x15" slit 
• LXD2.1 2.15-5.0 micron, R~2500 matched to 0.3x15" slit 
• LXD2.3 2.25-5.5 micron, R~2500 matched to 0.3x15" slit 
• Single order short 0.9-2.4 micron, R~2000 matched to a 0.3x60" slit
• Single order long 3.1-5.4 micron, R~2500 matched to a 0.3x60" slit 
• Slit viewer: 60x60" FOV at 0.12" per pixel, selection of filters available


InfraRed Telescope Facility (IRTF) 3.2m telescope on Maunakea, HI
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Aperture (m):     3.2
Latitude (deg):   19.8262 
Longitude (deg):  155.4719 
Elevation (m):    4168.07

A 3.2-meter telescope optimized for use in infrared astronomy and located on Maunakea in Hawaii. It was first built to support the Voyager missions and is now the US national facility for infrared astronomy, providing continued support to planetary, solar neighborhood, and deep space applications. The IRTF is operated by the University of Hawaii under a cooperative agreement with NASA. According to the IRTF's time allocation rules, at least 50% of the observing time is devoted to planetary science. The IRTF is a 3.2 m classical Cassegrain telescope. The Cassegrain focus f/ratio is f/38 and the primary mirror f/ratio is 2.5. Several aspects of the design of IRTF are optimized for IR observations. The secondary mirror is undersized to prevent the instrument from seeing the thermal emission from the telescope structure around the primary mirror. The primary mirror itself is 126" in diameter, but only the center 118" is used. A small mirror in the center of the secondary mirror prevents the instrument from seeing its own thermal emission. The f/ratio is long to have a small secondary mirror, again to minimize the telescope's thermal emission. The mirror coatings are chosen to have minimal thermal emission. The emissivity of the telescope is usually below 4%. The secondary mirror is mounted on a chopping mechanism to rapidly switch the pointing of the telescope from target to sky at up to 4 Hz. The IRTF is mounted on a large English yoke equatorial mount. The mount is very stiff, reducing flexure and allowing for accurate pointing of the telescope. Since the telescope is on an equatorial mount, the telescope can observe targets through the zenith without concern for field rotation. The yoke mount prevents the telescope from pointing north of +69 degrees declination. Since the telescope was primarily intended for planetary science, this restriction was considered to be acceptable. Since the telescope is on a heavy mounting, it is relatively immune from vibration or wind shake. Telescope Limits Declination The Hour Angle Limits +69:56:00 -59:00:00 +/- 5:04:47



Sources:
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IRTF:
Information was extracted from the telescope website.

SpeX:
Rayner, J.T., P. M. Onaka, M. C. Cushing and W. D. Vacca, 
Four Years of Good SpeX, 
in Ground-based Instrumentation for Astronomy, A. F. M. Moorwood and M. Iye, Eds., Proceedings of the SPIE, vol. 5492, pp. 1498-1509, 2004, doi:10.1117/12.551107.

Rayner, J. T., D. W. Toomey, P. M. Onaka, A. J. Denault, W. E. Stahlberger, W. D. Vacca, M. C. Cushing, and S. Wang,
SpeX: A Medium-Resolution 0.8 - 5.5 micron Spectrograph and Imager for the NASA Infrared Telescope Facility, 
PASP 115, 362-382, 2003, doi:10.1086/367745.


