Doppler Radar, Scatterometers, and Radar Altimeters are examples of active remote sensing instruments that use microwave frequencies. Radar technology is considered an active remote sensing system because it actively sends a microwave pulse and senses the energy reflected back. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio ACTIVE REMOTE SENSING The Japanese Advanced Microwave Scanning Radiometer for EOS (AMSR-E) instrument onboard NASA's Aqua satellite can acquire high-resolution microwave measurements of the entire polar region every day, even through clouds and snowfall. The ability of microwaves to pass through clouds enables scientists to monitor conditions underneath a hurricane. This scatterometer measures changes in the energy of the microwave pulses and can determine speed and direction of wind near the ocean surface. The SeaWinds instrument onboard the Quick Scatterometer (QuikSCAT) satellite uses radar pulses in the Ku-band of the microwave spectrum. Microwaves that penetrate haze, light rain and snow, clouds, and smoke are beneficial for satellite communication and studying the Earth from space. Here we see a computerenhanced radarimage of some mountains on the edge of Salt Lake City, Utah. It also used awavelengthin the L-band of the microwave spectrum. RIGHT: This is a radar image acquired from the Space Shuttle. CENTER: The JERS satellite uses wavelengths about 20 cm in length (L-band).This is an image of the Amazon River in Brazil.
LEFT: The ERS-1 satellite sends out wavelengths about 5.7 cm long (C-band).This image shows sea ice breaking off the shores of Alaska. Most communication satellites use C-, X-, and Ku-bands to send signals to a ground station. L-band microwaves, like those used by a Global Positioning System (GPS) receiver in your car, can also penetrate the canopy cover of forests to measure the soil moisture of rain forests. Medium-length (C-band) microwaves penetrate through clouds, dust, smoke, snow, and rain to reveal the Earth's surface. Different wavelengths of microwaves (grouped into "sub-bands") provide different information to scientists. Microwaves are a portion or "band" found at the higher frequency end of the radio spectrum, but they are commonly distinguished from radio waves because of the technologies used to access them. The interaction of these molecules undergoing forced rotation creates heat, and the food is cooked. Microwave ovens work by using microwave about 12 centimeters in length to force water and fat molecules in food to rotate.
RULE THE WAVES PATCH TV
You may be familiar with microwave images as they are used on TV weather news and you can even use microwaves to cook your food. Shown here is Hurricane Claudette's eye-wall making landfall. This Doppler-radar image seen on TV weather news uses microwaves for local weather forecasting.
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