Push broom scanner

A push broom scanner, also known as an along-track scanner, is a device for obtaining images with spectroscopic sensors. The scanners are regularly used for passive remote sensing from space, and in spectral analysis on production lines, for example with near-infrared spectroscopy used to identify contaminated food and feed.^[1] The moving scanner line in a traditional photocopier (or a scanner or facsimile machine) is also a familiar, everyday example of a push broom scanner. Push broom scanners and the whisk broom scanners variant (also known as across-track scanners) are often contrasted with staring arrays (such as in a digital camera), which image objects without scanning, and are more familiar to most people.

In orbital push broom sensors, 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 push broom sensors is the varying sensitivity of the individual detectors. Another drawback is that the resolution is lower than a whisk broom scanner because the entire image is captured at once.

Examples of spacecraft cameras using push broom imagers include Mars Express's High Resolution Stereo Camera,^[2] Lunar Reconnaissance Orbiter Camera NAC,^[3][4] Mars Global Surveyor's Mars Orbiter Camera WAC,^[2] and the Multi-angle Imaging SpectroRadiometer on board the Terra satellite.^[2]

• Time delay and integration
• Whisk broom scanner

• Earth Observing-1 (NASA), with animated whisk broom and push broom illustrations
• Airborne Pushbroom Line Scan (PDF) – overview article
• Linear Pushbroom Cameras (PDF) – detailed modelling theory

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