Fast Fourier Transform Telescope
Encyclopedia
Fast Fourier Transform Telescope is Tegmark
and Zaldarriaga
's name for a design for an all-digital
synthetic-aperture
telescope
. It is a type of interferometer designed to be cheaper than standard telescope interferometers currently in use.
In 1868, Hippolyte Fizeau
realized that the lenses and mirrors in a telescope
perform a physical approximation of a Fourier transform
. He noted that by using an array of small instruments it would be possible to measure the diameter of a star with the same precision as a single telescope which was as large as the whole array — a technique which later became known as astronomical interferometry. See History of astronomical interferometry.
In a 2008 paper, Tegmark and Zaldarriaga proposed a telescope design that dispenses altogether with the lenses and mirrors, relying instead on computers fast enough to perform all the necessary transforms. His concept is an all-digital telescope with an antenna consisting of a rectangular grid. Building radio telescope
s this way should become feasible within a few years if Moore's law
continues to hold. Eventually optical telescope
s could also be built this way. This technique is already being used in radar
applications.
This paper refers to an earlier telescope design from 1993 which took direct images of the Crab nebula
at radio wavelengths using an eight-by-eight-pixel
two-dimensional spatial FFT processor.
Max Tegmark
Max Tegmark is a Swedish-American cosmologist. Tegmark is a professor at the Massachusetts Institute of Technology and belongs to the scientific directorate of the Foundational Questions Institute.-Early life:...
and Zaldarriaga
Matias Zaldarriaga
Matias Zaldarriaga is an Argentine cosmologist. Born in Coghlan neighbourhood, Buenos Aires, at the present time he works in the Institute for Advanced Study located in Princeton, New Jersey, United States. He is known especially for his work on the cosmic microwave background...
's name for a design for an all-digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
synthetic-aperture
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...
telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
. It is a type of interferometer designed to be cheaper than standard telescope interferometers currently in use.
In 1868, Hippolyte Fizeau
Hippolyte Fizeau
Armand Hippolyte Louis Fizeau was a French physicist.-Biography:Fizeau was born in Paris. His earliest work was concerned with improvements in photographic processes. Following suggestions by François Arago, Léon Foucault and Fizeau collaborated in a series of investigations on the interference of...
realized that the lenses and mirrors in a telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
perform a physical approximation of a Fourier transform
Fourier transform
In mathematics, Fourier analysis is a subject area which grew from the study of Fourier series. The subject began with the study of the way general functions may be represented by sums of simpler trigonometric functions...
. He noted that by using an array of small instruments it would be possible to measure the diameter of a star with the same precision as a single telescope which was as large as the whole array — a technique which later became known as astronomical interferometry. See History of astronomical interferometry.
In a 2008 paper, Tegmark and Zaldarriaga proposed a telescope design that dispenses altogether with the lenses and mirrors, relying instead on computers fast enough to perform all the necessary transforms. His concept is an all-digital telescope with an antenna consisting of a rectangular grid. Building radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...
s this way should become feasible within a few years if Moore's law
Moore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
continues to hold. Eventually optical telescope
Optical telescope
An optical telescope is a telescope which is used to gather and focus light mainly from the visible part of the electromagnetic spectrum for directly viewing a magnified image for making a photograph, or collecting data through electronic image sensors....
s could also be built this way. This technique is already being used in radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
applications.
This paper refers to an earlier telescope design from 1993 which took direct images of the Crab nebula
Crab Nebula
The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus...
at radio wavelengths using an eight-by-eight-pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
two-dimensional spatial FFT processor.
See also
- Aperture synthesisAperture synthesisAperture 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...
- Interferometric synthetic aperture radarInterferometric synthetic aperture radarInterferometric synthetic aperture radar, also abbreviated InSAR or IfSAR, is a radar technique used in geodesy and remote sensing. This geodetic method uses two or more synthetic aperture radar images to generate maps of surface deformation or digital elevation, using differences in the phase of...
- Inverse synthetic aperture radarInverse synthetic aperture radarInverse synthetic aperture radar is a technique to generate a two-dimensional high resolution image of a target.ISAR technology utilizes the movement of the target rather than the emitter to create the synthetic aperture...
- List of telescope types
- Synthetic aperture radarSynthetic aperture radarSynthetic-aperture radar is a form of radar whose defining characteristic is its use of relative motion between an antenna and its target region to provide distinctive long-term coherent-signal variations that are exploited to obtain finer spatial resolution than is possible with conventional...
Further reading
- Jan Hamann, Steen Hannestad, Martin S. Sloth, Yvonne Y. Y. Wong (2008), "Observing trans-Planckian ripples in the primordial power spectrum with future large scale structure probes", Journal of Cosmology and Astroparticle Physics, arxiv 0807.4528
- Jonathan R. Pritchard, Elena Pierpaoli (2008), "Constraining massive neutrinos using cosmological 21 cm observations", Phys.Rev.D78:065009,2008, arxiv 0805.1920
- Yi Mao, Max Tegmark, Matthew McQuinn, Matias Zaldarriaga, Oliver Zahn (2008), "How accurately can 21 cm tomography constrain cosmology?", Phys. Rev. D 78, 023529 (2008), arxiv 0802.1710
- Kendrick M. Smith, Asantha Cooray, Sudeep Das, Olivier Doré, Duncan Hanson, Chris Hirata, Manoj Kaplinghat, Brian Keating, Marilena LoVerde, Nathan Miller, Graça Rocha, Meir Shimon, Oliver Zahn (2008), "CMBPol Mission Concept Study: Gravitational Lensing", arxiv 0811.3916
- Eli Visbal, Abraham Loeb, Stuart Wyithe (2008 preprint), "Cosmological Constraints from 21 cm Surveys After Reionization", arxiv 0812.0419
- Vernon Barger, Yu Gao, Yi Mao, Danny Marfatia, (2008 preprint), "Inflationary Potential from 21 cm Tomography and Planck", arxiv 0810.3337
- Y Mao (2008 preprint), "Constraining Gravitational and Cosmological Parameters with Astrophysical Data", arxiv 0808.2063