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WE KNOW THE FOCAL LENGTH OF THE LENS AND THE ALTITUDE OF THE SHUTTLE. IN A FILM CAMERA, THE “SIZE ACROSS/THE DETECTOR” IS JUST THE SIZE OF THE FILM (E.G. 35 MM FOR REGULAR 35MM CAMERA); IN THE KIDSAT CAMERA, IT’S THE PHYSICAL SIZE OF THE DETECTOR. THE SIZE OF THE DETECTOR IN THE FOCAL PLANE OF THE KIDSAT CAMERA IS/SHOWN BELOW:

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IN THIS CASE, THE DETECTOR IS RECTANGULAR, SO IT PRODUCES A RECTANGULAR IMAGE. THIS MEANS THAT THE KIDSAT/CAMERA PHOTOGRAPHS A RECTANGULAR PIECE OF GROUND. TO FIND OUT THE DISTANCE ALONG ONE SIDE OF THE PHOTO, USE ONE DIMENSION OF THE DETECTOR (E.G. 28 MM) IN THE EQUATION; TO FIND THE DISTANCE ALONG THE OTHER SIDE, USE THE OTHER DIMENSION.

FOR EXAMPLE, IF THE 50MM LENS IS ATTACHED TO THE CAMERA, THE PHOTOGRAPH WILL COVER ABOUT 111 X 71/MILES (ASSUMING THE SHUTTLE IS 200 MILES ABOVE THE EARTH). THE FOLLOWING TABLE SHOWS THE LENGTH AND WIDTH OF THE “FOOTPRINT“ AT TWO DIFFERENT SHUTTLE HEIGHTS. 200 MILES IS TYPICAL OF THE SHUTTLE ALTITUDE/BEFORE THE DOCKING WITH MIR.

Altitude = 200 miles = 322 km
focal length | length | width
50 mm        | 111 mi | 71 mi
180 mm       | 31 mi  | 20 mi

Altitude = 250 miles = 402 km
focal length | length | width
50 mm        | 140 mi | 90 mi
180 mm       | 39 mi  | 25 mi

NOTICE THAT THE SIZE OF THE FOOTPRINT INCREASES (FOR A GIVEN LENS) IF THE SHUTTLE ALTITUDE increases. (YOU CAN DEMONSTRATE THIS EFFECT BY TAKING A FLASHLIGHT, HOLDING IT A CERTAIN HEIGHT ABOVE A PIECE OF PAPER, MARKING THE SIZE OF THE ILLUMINATED AREA, THEN RAISING THE FLASHLIGHT. THE NEW ILLUMINATED AREA WILL BE LARGER.

07/22/96      Page 4.8

Transcription Notes:
Why all caps?