The University of Hawaiʻi 88-inch (2.24-meter) telescope —called UH88 , UH2.2 , or simply 88 by members of the local astronomical community—is situated at the Mauna Kea Observatories and operated by the University's Institute for Astronomy . It was constructed in 1968, and entered service in 1970, at which point it was known as "The Mauna Kea Observatory". It became one of the first professional telescopes to be controlled by a computer. The telescope was built with funding from NASA, to support Solar System missions, and is controlled by the University of Hawaiʻi . The success of the telescope helped demonstrate the value of Mauna Kea for astronomical observations.
17-457: On December 4, 1984 it became the first telescope to make optical closure phase measurements on an astronomical source using an aperture mask . UH88 is a Cassegrain reflector tube telescope with an f/10 focal ratio , supported by a large open fork equatorial mount . It was the last telescope on Mauna Kea to use a tube design rather than an open truss, and is the largest in the complex to use an open fork mount , with neighboring telescopes in
34-484: A 1 cos θ {\displaystyle x_{1}=a_{1}\cos \theta } , x 2 = a 2 cos θ {\displaystyle x_{2}=a_{2}\cos \theta } , and x 3 = ( a 1 + a 2 ) cos θ {\displaystyle x_{3}=(a_{1}+a_{2})\cos \theta } . When one mixes signals from two of antennas (compensating for
51-517: A delay for the angle θ 0 {\displaystyle \theta _{0}} ) one observes interference signal with phase x ( θ ) − x ( θ 0 ) . {\displaystyle x(\theta )-x(\theta _{0}).} Taking into account that signals may come from several sources, the complex interference signal is the Fourier transform P {\displaystyle P} of
68-546: A radio interferometer, but it became widely used for long baseline radio interferometry only in 1974. A minimum of three antennas are required. This method was used for the first VLBI measurements, and a modified form of this approach ("Self-Calibration") is still used today. The "closure-phase" or "self-calibration" methods are also used to eliminate the effects of astronomical seeing in optical and infrared observations using astronomical interferometers . A minimum of three antennas are required for closure phase measurements. In
85-402: Is positive for small x {\displaystyle x} , one can fully map how the sign changes, and calculate P ( x ) {\displaystyle P(x)} . Aperture masks are often used on single telescopes to allow the extraction of closure phases from the images. Kernel-phases can be seen as a generalization of closure phase for redundant arrays in cases where
102-428: Is then computed as the argument of this bispectrum: This method of computation is robust to noise and allow to perform averaging even if the noise dominates the phase signal. Example: even when power distribution of the source is symmetric, so P ( x ) {\displaystyle P(x)} is real, measuring | P ( x ) | {\displaystyle |P(x)|} still leaves
119-507: The 3-meter class using English mount designs. As the only research telescope controlled solely by the University, UH88 has long been the primary telescope used by its professors, postdoctoral scholars, and graduate students, and, as a result, the site of numerous discoveries. David C. Jewitt and Jane X. Luu discovered the first Kuiper belt object, 15760 Albion , using UH88, and a team led by Jewitt and Scott S. Sheppard discovered 45 of
136-435: The complex visibilities are actually multiplied together to form the triple product instead of simply summing the visibility phases. The phase of the triple product is the closure phase. In optical interferometry, the closure phase was first introduced by the bispectrum speckle interferometry , the principle of which is to compute the closure phase from the complex measurement instead of the phase itself: The closure phase
153-668: The known moons of Jupiter , as well as moons of Saturn, Uranus and Neptune. The Institute for Astronomy also makes agreements with other organizations for portions of available observing time. Currently, the National Astronomical Observatory of Japan uses UH88 for some research projects for which its far larger and more expensive Subaru Observatory , also on Mauna Kea, would be overkill. The Nearby Supernova Factory project, based at Lawrence Berkeley National Laboratory , also has its Supernova Integrated Field Spectrograph (SNIFS) instrument mounted on UH88. In June 2011,
170-483: The power density of the sources. The phases of the complex visibility of the radio source corresponding to baselines a 1 , a 2 and a 3 are denoted by ϕ 1 {\displaystyle \phi _{1}} , ϕ 2 {\displaystyle \phi _{2}} and ϕ 3 {\displaystyle \phi _{3}} respectively. These phases will contain errors resulting from ε B and ε C in
187-408: The signal phases. The measured phases for baselines x 1 , x 2 and x 3 , denoted ψ 1 {\displaystyle \psi _{1}} , ψ 2 {\displaystyle \psi _{2}} and ψ 3 {\displaystyle \psi _{3}} , will be: Jennison defined his observable O (now called the closure phase ) for
SECTION 10
#1732855123961204-424: The signs unknown. The closure phase allows finding the sign of P ( x 1 + x 2 ) {\displaystyle P(x_{1}+x_{2})} when signs of P ( x 1 ) {\displaystyle P(x_{1})} , P ( x 2 ) {\displaystyle P(x_{2})} are known. Since P ( x ) {\displaystyle P(x)}
221-467: The simplest case, with three antennas in a line separated by the distances a 1 and a 2 shown in diagram at the right. The radio signals received are recorded onto magnetic tapes and sent to a laboratory such as the Very Long Baseline Array . The effective baselines for a source at an angle θ {\displaystyle \theta } will be x 1 =
238-542: The source. While | P ( x ) | {\displaystyle |P(x)|} may be measured directly, and the phase of P ( x ) {\displaystyle P(x)} cannot be found from 2-antennas VLBI, using 3 antennas one can find the phase of P ( x 1 ) P ( x 2 ) P ∗ ( x 1 + x 2 ) . {\displaystyle P(x_{1})P(x_{2})P^{*}(x_{1}+x_{2}).} In most real observations,
255-461: The telescope and its weather station were struck by lightning, damaging many systems and disabling it, but the telescope was repaired by August 2011. Some of the systems at the observatory were 41 years old at the time of the damage and had to be reverse engineered to be fixed. The weather station is currently under development. Closure phase The closure phase is an observable quantity in imaging astronomical interferometry , which allowed
272-408: The three antennas as: As the error terms cancel: The closure phase is unaffected by phase errors at any of the antennas. Because of this property, it is widely used for aperture synthesis imaging in astronomical interferometry . For a point source, O {\displaystyle O} is 0; so O {\displaystyle O} carries information on the spatial distribution of
289-740: The use of interferometry with very long baselines . It forms the basis of the self-calibration approach to interferometric imaging . The observable which is usually used in most "closure phase" observations is actually the complex quantity called the triple product (or bispectrum ). The closure phase is the phase ( argument ) of this complex quantity. Roger Jennison developed this novel technique for obtaining information about visibility phases in an interferometer when delay errors are present. Although his initial laboratory measurements of closure phase had been done at optical wavelengths, he foresaw greater potential for his technique in radio interferometry . In 1958 he demonstrated its effectiveness with
#960039