A push broom scanner (along track scanner) is a technology for obtaining images with spectroscopic sensors. It is regularly used for passive remote sensing from space and in spectral analysis on production lines, for example with near-infrared spectroscopy. Push broom scanners are often contrasted with staring arrays (such as a cell phone camera), which are more familiar to most people.
In a push broom sensor, a line of sensors arranged perpendicular to the flight direction of the spacecraft is used. Different areas of the surface are imaged as the spacecraft flies forward. A push broom scanner can gather more light than a whisk broom scanner because it looks at a particular area for a longer time, like a long exposure on a camera. One drawback of pushbroom sensors is the varying sensitivity of the individual detectors. These sensors are also known as survey or wide field devices, comparable to wide angle lenses on conventional cameras.
Example spacecraft cameras using push broom imagers: Mars Express's High Resolution Stereo Camera, Lunar Reconnaissance Orbiter Camera NAC, Mars Global Surveyor's Mars Orbiter Camera WAC, and the Multi-angle Imaging SpectroRadiometer on board the Terra satellite.
The moving scanner line in a traditional photocopier (or a scanner or facsimile machine) is a familiar, everyday example of a push broom scanner.