Earth Observation
Earth observation is one of the most commercially and scientifically valuable uses of space. Satellites equipped with optical and radar sensors monitor agricultural yields, urban growth, deforestation, disaster zones, and military activity from hundreds of kilometers overhead. The key performance dimensions — spatial resolution, spectral bands, revisit frequency, and coverage area — define what each system can see and how often.
Terms in this Category
SAR (Synthetic Aperture Radar)
A radar imaging technique that produces high-resolution imagery regardless of daylight or many cloud conditions.
Multispectral Imaging
A remote sensing technique that captures image data across multiple distinct wavelength bands, from visible to infrared, enabling analysis beyond what the human eye can see.
Ground Sampling Distance (GSD)
The distance between the centers of adjacent pixels in a satellite image, measured on the ground — the fundamental metric for spatial resolution.
Revisit Time
The frequency with which a satellite or constellation can image the same point on Earth, measured in days, hours, or minutes.
SmallSat
A broad class of smaller spacecraft including CubeSats, microsats, and minisats.
CubeSat
A standardized small-satellite format based on modular units, often used for research, demonstrations, and commercial missions.
Constellation
A coordinated group of satellites designed to operate as a system.
Frequently Asked Questions
What is the difference between SAR and optical imaging?
SAR (Synthetic Aperture Radar) uses active radar pulses to create images day or night and through clouds. Optical imaging relies on sunlight and is blocked by cloud cover.
What is Ground Sampling Distance?
GSD is the distance between adjacent pixel centers on the ground. A 30 cm GSD means each pixel covers 30×30 cm. Lower numbers mean finer detail.
How often can a satellite image the same spot?
Revisit time depends on the constellation size. A single LEO satellite may revisit every 5-16 days; large constellations can achieve daily or sub-hourly coverage.