Does a push broom scanner scan a path perpendicular to the direction of satellite travel? I am confused because its detectors are arranged across track even though it scans along track.
Does the image of the pushbroom scans a path perpendicular to the direction of satellite travel?
Not really. There is no "scanning" in a push broom sensor. A push broom sensor does not have any moving parts; compare with the related whisk broom sensor which does indeed scan a path perpendicular to the satellite's motion. The difference between the two is that a push broom sensor has multiple identical sensors arranged in a line (orthogonal to the nominal direction of travel) while a whisk broom sensor has but one sensor. The line of sensors in a push broom sensor eliminates the need for scanning.
Both types of sensors form an image by forming image lines and then pasting those image lines, one after another, into an image buffer. A push broom sensor forms an image line by exposing all of the sensors to light simultaneously. A whisk broom sensor forms an image line by taking a series of snapshots, rotating the sensor a bit between each snapshot. With both kinds of sensors, the satellite's motion between capturing individual lines is what enables an image to be formed.