G8 Mapping Venus (On Grade) – 03

 

Remote sensing is a process of obtaining information. In short, remote sensing is the collection of measurements and data of some feature or phenomenon that cannot be touched. Your eyes, ears and nose are tools for remote sensing. You can hear sound that travels through different materials. Your nose reacts to chemical signals via smell. Your eyes help you detect physical properties, such as size, color and shape. Unlike Earth, Venus is covered with a thick layer of clouds. It is impossible to see the surface of Venus. To learn about and map the surface, engineers built Magellan to peer through the thick clouds using radar.

 The radar on the Magellan spacecraft is able to collect data actively by broadcasting an electronic signal, then measures the time it takes and the portion of the signal that is returned. This is similar to how sound waves are used to study the ocean floor.

To learn how remote sensing works, your teacher had you make topographic maps using a long wooden rod. The teacher placed objects inside a shoe box. Your task was to map the objects by inserting the rod into premade holes and measuring how much of the rod was inserted before it hit an object. The wooden rods are a proxy for sound waves. This is similar to how sailors would find the depth of the water using a long rope with weights tied to the end. The knots were tied at six-foot intervals, which represented a fathom. Fathoms are still used by sailors for measuring the depth of water.

Today, scientists use SONAR to make the same measurement. SONAR is an acronym that stands for Sound Navigation and Ranging. A short burst of sound, or “ping”, is sent toward the bottom. The “ping” hits the bottom and is reflected toward the surface. An instrument called a transducer, which is mounted to the bottom of the ship, receives the reflected ping. A timer records the time it takes between the instant the ping is sent until it is received by the transducer.

The depth of the water is calculated by multiplying the time recorded by the speed of sound through water. The distance traveled by the ping is twice the depth from the vessel to the bottom. With this knowledge a topographic map can be made of the sea floor. Sound waves work great in water, but for the dense clouds of Venus, RADAR is needed.

Like soundwaves, RADAR can be used as an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It was first developed in World War II as a way to detect enemy planes. Radar is now used for many purposes such as air traffic control, air defense systems, and for making weather observations.

During its four-year mission, Magellan collected data about Venus’ topography with 10 times more resolution than earlier missions.  At the end of its useful life, Magellan was commanded into a gradual dive into the Venusian atmosphere to obtain information about its properties. It finally burned up on Oct.12, 1994.

Just as you are reading the last of the article below the picture, grandpa enters the room. He explains how he played a small role in all of the spacecraft you see in this room. But, just like grandpa, he turns the conversation towards you. “After breakfast I want you to tell me about the things you would like to do when you grow up,” he says to you. He explains, “No dream is too big, not even going into space.”