Digitized Data

[grid] Infrared radiation is collected by the KAO telescope and focused onto a detector. The detector has 60 infrared sensors arranged like this array. (The four corners of the array do not have sensors.) Each sensor measures the radiation falling on its area of the detector.

Above left is an infrared image of the center of the M33 - Each little square in the picture is called a "pixel." (picture element) It is difficult for the human eye to identify in object with only 64 pixels. Try to identify the 64 pixel image directly to the left.

1.[1.] 2.[2.] 3.[3.]
In image 1, Jupiter has thousands of data points. Notice the detail in the cloud hands and belts as well as the Great Red Spot. Image 2 is the same photo with only 32 pixels across and 32 down (1024 total pixels). How does detail change? Image 3 is also 32 pixels by 32 pixels. Back away from the paper until your eyes turn the pixels into an image. How will the KAO images compare in detail to images in visible light?

Can you read the image above? Back away and try again.

Sizing up the field

In infrared observations made at 60 microns, the detector array covers only 2 arc minutes (or 120 arc seconds) on each side.

The Ring Nebula (to the left) is 70 arc seconds wide and is scaled in this photo to be the size that the KAO detector will see.

Some objects like the M33 galaxy (to right), are much too large for the detector. The white square in the photo shows the relative size of the IR detector array. Astronomers will have to choose what part of the object to observe. The entire galaxy is 60 arc minutes by 40 arc minutes. Draw ten little boxes around the areas where you would collect data in M33.

At a wavelength of 100 microns, the array sees an area 3.5 arc minutes on a side. At 160 microns. the array covers 6 arc minutes on a side. If the box above is 2 arc minutes wide, draw a box that would show the field at I 00 microns and at 160 microns. Astronomers on the KAO will report which wavelengths they are measuring during the flight.

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