Signal detection
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Signal detection Objects at higher temperatures than 0K emit E-M radiation. Receivers in radio telescopes have to be cooled to almost absolute zero to avoid the equipment in them emitting too much radiation and drowning out the A radio receiver converts radio waves into electronic signals. Radio waves from astronomical sources are very weak telescope receivers and so must be highly sensitive. Image Courtesy of M. Crofts Image Courtesy of M. Crofts THE IMAGE TRACKING As the Earth rotates the sky appears to move. Telescopes use carefully controlled motors to follow the motion of objects in the sky. Radio telescopes don’t take colour pictures (remember colours are different wavelengths). Instead, the data from the telescope has to be made into an image with a computer. A contour map draws lines between points of equal intensity, just like the isobars on a weather map. False colour images use differen t colours to represen t differen t levels of intensit y. Image courtesy of NRAO/AUI Image courtesy of NRAO/AUI The galaxy to the right is NGC1275. At its centre is a bright radio source, Image HST Large counterweights balance the telescope on its mount. Radio Telescopes Wire mesh can be used to reflect radio waves. This is possible if the wavelength of the radio waves we want to detect is at least ten times the size of the mesh spacing. Building a telescope with a mesh reflecting surface is much cheaper. The dishes will also weigh less. Light can be focused using a curved mirror like a lens. Signal collection Radio waves can also be focused using a curved surface. The reflecting surface has to be much larger though, since radio wavelengths are about 100,000 times longer than visible light. After focusing, the radio waves are reflected back to a receiver. very faint signals from astronomical sources. Schools @ Lord’sBridge
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Signal collection. Light can be focused using a curved mirror like a lens. Wire mesh can be used to reflect radio waves. This is possible if the wavelength of the radio waves we want to detect is at least ten times the size of the mesh. - PowerPoint PPT Presentation
Transcript of Signal detection
Signal detection
Objects at higher temperatures than 0K emit E-M radiation. Receivers in radio telescopes have to be cooled to almost absolute zero to avoid the equipment in them emitting too much radiation and drowning out the
A radio receiver converts radio waves into electronic signals. Radio waves from astronomical sources are very weak telescope receivers and so must be highly sensitive.
Image C
ourtesy of M. C
rofts
Imag
e C
ourt
esy
of M
. Cro
fts
THE IMAGE TRACKING
As the Earth rotates the sky appears to move. Telescopes use carefully controlled motors to follow the motion of objects in the sky.
Radio telescopes don’t take colour pictures (remember colours are different wavelengths). Instead, the data from the telescope has to be made into an image with a computer.
A contour map draws lines between points of equal intensity, just like the isobars on a weather map.
False colour images use different colours to represent different levels of intensity.
Image courtesy of N
RA
O/A
UI
Image courtesy of NRAO/AUI
The galaxy to the right is NGC1275. At its centre is a bright radio source,
Imag
e H
ST
Large counterweights balance the telescope on its mount.
Radio Telescopes
Wire mesh can be used to reflect radio waves. This is possible if the wavelength of the radio waves we want to detect is at least ten times the size of the mesh
spacing. Building a telescope with a mesh reflecting surface is much cheaper. The dishes will also weigh less.
Light can be focused using a curved mirror like a lens.
Signal collectionRadio waves can also be focused using a curved surface. The reflecting surface has to be much larger
though, since radio wavelengths are about 100,000 times longer than visible light. After focusing, the radio waves are reflected back to a receiver.
very faint signals from astronomical sources.
Schools @ Lord’s Bridge
