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California Institute of Technology

Smithsonian-Taiwan Submillimeter Array

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Smithsonian Institute and Taiwan

7.4.3 Other major observatories

There are a number of other major observatories across the world, many of which are involved in giant planet observations. In this section we will briefly list some of the largest and most famous of these observatories and outline the telescopes available.

(1) Calar Alto. This observatory, sited at an altitude of 2,168 m in Andalusia, Spain, is operated by the Max-Planck-Institut fur Astronomie, Heidelberg, Germany, and has been used extensively for planetary observations. Three main telescopes are provided with apertures of 1.23m, 2.2m, and 3.5m, together with a 1.5m telescope operated by the Observatory of Madrid.

(2) AAO. The Anglo-Australian Observatory is situated in northern New South Wales, Australia and operates the 3.9 m Anglo-Australian telescope and the 1.2 m U.K. Schmidt telescope. The AAO is not currently involved in giant planet observations, but is involved in the search for extrasolar planets, by the "Doppler wobble'' technique described in Chapter 8.

(3) Pic-du-Midi. The Pic-du-Midi Observatory is situated at an altitude of 2,872m in the French Pyrenees. The observatory operates a 1 m and 2 m telescope and has undertaken numerous investigations of the giant planets.

(4) La Palma. The La Palma Observatory, run by the Isaac Newton Group of Telescopes (ING) operates the 4.2 m William Herschel Telescope, the 2.5 m

Isaac Newton Telescope, and the 1.0 m Jacobus Kapteyn Telescope on behalf of British, Dutch, and Spanish research agencies. The La Palma Observatory does not currently undertake giant planet observations.

(5) Kitt Peak National Observatory. The Kitt Peak National Observatory is located high above the Sonoran Desert in Arizona and is home to 22 optical and two radio telescopes representing eight astronomical research institutions. The largest of these telescopes are the 4 m Mayall, the 3.5 m WIYN, the 2.1 m and the 0.9 m. The Kitt Peak National Observatory is also involved in the search for extrasolar planets.

(6) Palomar. The Palomar Observatory in California is owned and operated by the California Institute of Technology. Its principal instruments are the 200-inch (5 m) Hale Telescope, the 48-inch (1.2 m) Oschin Telescope, the 18-inch (0.45 m) Schmidt telescope, and the 60-inch (1.5 m) reflecting telescope. For many years the Hale telescope was the largest in the world.

(7) Las Campanas. The Las Campanas Observatory, at an altitude of 2,438 m in the Chilean Andes, is operated by the Observatories of the Carnegie Institution of Washington (OCIW). The site includes the two 6.5 m Magellan telescopes which began operations in September 2000 and September 2002, respectively.

7.5 AIRBORNE VISIBLE/IR OBSERVATIONS

We saw earlier that IR astronomy from ground-based telescopes is severely hampered by the absorption of gases in the Earth's atmosphere, especially water vapor. Most of this water vapor lies in the lower, warmer parts of the atmosphere and thus, as mentioned earlier, most ground-based IR facilities are placed at high altitudes, in climatically dry parts of the world. However, the number of locations on the Earth that satisfy these requirements is limited, and they are often also remote, making the construction and operation of these telescopes rather difficult. An alternative approach to Earth-based IR astronomy is to mount an infrared telescope on to an aircraft and observe in-flight at high altitude almost anywhere in the world. At the high altitudes attainable by jet aircraft, the obscuration by overlying water vapor is reduced by a factor of 1,000 compared with observations at sea level. In addition, airborne observations are unaffected by cloud obscuration, and such observatories may be used to observe both the southern and northern skies. A further advantage is that an airborne observatory is ideal for observing stellar occultation events since it can fly to the optimum position in the world to observe them.

7.5.1 Kuiper Airborne Observatory

The first airborne observations were made in the 1960s, but airborne IR observations really came of age with the commission of NASA's Kuiper Airborne Observatory (KAO) named after the American planetary scientist Gerard P. Kuiper (1905-1973). The Kuiper aircraft (Figure 7.17) was a Lockheed C-141A jet transport plane with a range of 6,000 nautical miles and was capable of conducting research operations to

Figure 7.17. The Kuiper Airborne Astronomy (KAO) aircraft. Courtesy of NASA.

45,000 feet (14 km). The aircraft was modified to carry a 0.91 m aperture Cassegrain IR telescope operating in the 1 ^m to 500 ^m spectral range and which observed through a hole cut in the side of the aircraft at an elevation of between 35° and 75° (Figure 7.18). The KAO flew out of NASA Ames Research Center, at Moffett Field, California, and began operating in 1971, finally finishing service in 0ctober 1995.

The telescope was mounted such that it moved independently from the aircraft and an automatic system kept the telescope pointed at the selected target even when the aircraft moved in turbulence. The telescope mirrors were cooled with liquid nitrogen, and other cryogenic liquids were used to reduce their background IR emission.

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