Today many electronic gadgets like a television, cell phone are able to transfer pictures from one place to far off place without wires. All this has become possible because of transmission via radio waves which does not need a medium to travel. The spacecraft sends pictures taken in the outer space to earth much in a similar way. The only difference being the need for a much bigger and powerful antenna to receive radio waves.
The cameras inside the spacecraft are much like the digital cameras without any film. They have millions of tiny light sensitive cells called picture elements or pixels. Pixels are very tiny in size. While taking pictures, each pixel captures the brightness of a tiny part of the object viewed. These tiny pixels in millions make up an electronic device called charge coupled device (CCD). This CCD is a circuit that can store and display data. CCDs present in the camera converts the picture taken by each tiny pixel into corresponding number. For example, dull or no light could be represented as 0 and very bright light could be 100. Any other shade with varying brightness could range between 0 and 100. For taking color pictures, different colored filter are present inside the camera. A red filter would only let red color to pass through; a blue and green filter works the same way.
The output from these three filters help produce color images. The data in number format is transmitted to the earth where the computers convert the number back to pixels displaying the entire picture of the object viewed by the camera.
Camera in a spacecraft :Basics of functioning
The cameras inside the spacecraft are much like the digital cameras without any film. They have millions of tiny light sensitive cells called picture elements or pixels.