urn:nasa:pds:context:telescope:irtf-maunakea.3m2 1.1 1.16.0.0 Product_Context urn:nasa:pds:context:telescope:irtf.3m0 InfraRed Telescope Facility 3.0-Meter Telescope 2023-10-12 1.1 Revised version produced by SBN/PSI Node. Updated telescope aperture in the description. 2021-11-06 1.0 Revised version produced by RMS Node, including LID, Title, Alias, Reference List, and Aperture urn:nasa:pds:context:facility:observatory.irtf-maunakea telescope_to_facility urn:nasa:pds:context:instrument:irtf-maunakea.3m2.cvf telescope_to_instrument urn:nasa:pds:context:instrument:irtf-maunakea.3m2.mirac telescope_to_instrument urn:nasa:pds:context:instrument:irtf-maunakea.3m2.mirac2 telescope_to_instrument urn:nasa:pds:context:instrument:irtf-maunakea.3m2.mirli telescope_to_instrument urn:nasa:pds:context:instrument:irtf-maunakea.3m2.mirlin telescope_to_instrument urn:nasa:pds:context:instrument:irtf-maunakea.3m2.mirsi telescope_to_instrument urn:nasa:pds:context:instrument:irtf-maunakea.3m2.primo_1 telescope_to_instrument urn:nasa:pds:context:instrument:irtf-maunakea.3m2.spex telescope_to_instrument urn:nasa:pds:context:instrument:multi-host.generic_insp_hsp telescope_to_instrument 3.2 155.4719 19.8262 4168.07 A 3.2-meter telescope optimized for use in infrared astronomy and located on Mauna Kea 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