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Across-Track Scanner

Definition

An across-track scanner (whiskbroom sensor) captures data perpendicular to a platform’s motion (e.g., satellite), scanning Earth’s surface line by line. It uses rotating mirrors or sensors to collect reflected/emitted radiation across a swath, often providing higher spatial resolution but slower coverage than along-track systems.

Application

Used in multispectral imaging for environmental monitoring (e.g., Landsat’s Thematic Mapper). Agricultural applications include crop health assessment via NDVI. Geological surveys use it to map mineral compositions. Due to mechanical complexity, these scanners are being phased out in favor of pushbroom (along-track) sensors but remain valuable for historical data analysis.

FAQ

1. How does an across-track scanner differ from a pushbroom scanner?

Across-track uses moving parts to scan side-to-side; pushbroom uses a linear sensor array.

2. What are limitations of across-track scanners?

Lower swath width, mechanical wear, and slower data acquisition.

3. Which satellites used across-track technology?

Landsat 1-7, SPOT 1-4.

4. Are they still relevant today?

Mostly for legacy data, as pushbroom systems dominate modern missions.