Algonquin 46m radio telescope

Algonquin 46m radio telescope

Observatory	Algonquin Radio Observatory
Location(s)	Algonquin Provincial Park ,
Coordinates	45°57′20″N 78°04′23″W / 45.955503°N 78.073042°W / 45.955503; -78.073042Coordinates: 45°57′20″N 78°04′23″W / 45.955503°N 78.073042°W / 45.955503; -78.073042
Organization	Thoth Technology Inc.
Built	1964–1966 (1964–1966)
First light	May 1966
Telescope style	radio telescope, Gregorian telescope, parabolic reflector
Diameter	45.7 m (149 ft 11 in)
Collecting area	1,640 m2 (17,700 sq ft)
Focal length	18.3 m (60 ft)
Mounting	Altazimuth mount
Website	www.arocanada.com
Location of Algonquin 46m radio telescope
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The Algonquin 46m radio telescope (ARO) is a radio telescope at the Algonquin Radio Observatory, Canada. This radio telescope is historically famous for taking part in the first successful very long baseline interferometry experiment in the 1960s, where it was experimentally arrayed with the 26-metre Telescope at the Dominion Radio Astrophysical Observatory near Penticton, British Columbia.

In 1961, the site was selected by the National Research Council of Canada as suitable for the construction of a 120 ft (37 m) fully steerable antenna. By 1962, plans showed that the main instrument had grown to a 150 ft (46 m) antenna.

Construction of the 150 ft (46 m) telescope started in the spring of 1964. The concrete base weighed 300 tons, the steel dish and the its rotating mount another 900 tons. An equatorial mount in the base, only five feet high, positioned the instrument. The telescope was designed to operate at higher frequencies than existing instruments, requiring much of it to be constructed of flat plates instead of an open mesh in order to accurately focus these signals. The surface was built to be accurate to 1/5 of a centimeter, allowing it to accurately focus wavelengths to around 1.5 cm. Construction was completed in early 1966, and the telescope started operations in May 1966. Work was also completed a polar mounted paraboloid microwave horn and an 11 m equatorial mount dish north of the main antenna complex.

One of the earliest extended projects carried out on the instrument was the first successful very long baseline interferometry (VLBI) experiment. Long Baseline Interferometry compares the signals from two or more telescopes, using the differences in phase between the signals to resolve the objects. Earlier experiments had used direct electrical links or microwave relays to extend the distance between the two telescopes, while still allowing real-time comparison of the phase of the two signals in a common instrument. However this limited the distance between the two instruments, to the distance the signal could travel while still remaining in-phase. The NRC invented a new technique that eliminated the need to directly compare the signals in real-time. Their technique used 2 inch Quadruplex videotape to record the signals along with a clock signal from an atomic clock. The clock signal allowed the two signals to be later compared with the same accuracy that had formerly required direct realtime connections. NRC funded the installation of identical instruments at the ARO and a smaller telescope at DRAO. Combining the signals would simulated a single 3,074 km diameter radio telescope.