The Infrared Spatial Interferometer (ISI) is an astronomical interferometer array of three telescopes operating in the mid-

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

. The telescopes are fully mobile and their current site on Mount Wilson allows for placements as far as apart, giving the resolution of a telescope of that diameter. The signals are converted to radio frequencies through

heterodyne A heterodyne is a signal frequency that is created by combining or mixing two other frequencies using a signal processing technique called ''heterodyning'', which was invented by Canadian inventor-engineer Reginald Fessenden. Heterodyning is u ...

circuits and then combined electronically using techniques copied from

radio astronomy Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation comin ...

. ISI is run by the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

Space Sciences Laboratory The Space Sciences Laboratory (SSL) is an Organized Research Unit (ORU) of the University of California, Berkeley. Founded in 1959, the laboratory is located in the Berkeley Hills above the university campus. It has developed and continues t ...

. The longest () baseline provides a resolution of 0.003 arcsecond at a

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...

of 11

micrometre The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

s. On 9 July 2003, ISI recorded the first

closure phase The closure phase is an observable quantity in imaging astronomical interferometry, which allowed the use of interferometry with very long baselines. It forms the basis of the self-calibration approach to interferometric imaging. The observable ...

aperture synthesis Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. At each separation and ...

measurements in the mid infrared.

References

{{Portal, Spaceflight

External links

* https://web.archive.org/web/20071215183003/http://isi.ssl.berkeley.edu/ Infrared telescopes Interferometric telescopes