Lecture 6 (10/14)METR 1111 Satellites Doing Something Different
What are satellites? • Satellite – Any object that orbits around another object • (You’ve got to like these intensive definitions)
What can satellites do? • Man-made satellites are designed to carry out a wide range of tasks • Take images, relay signals, etc • First introduced over 40 years ago with the Russian satellite Sputnik • Currently, over 8000 satellites orbiting Earth • Most are not much bigger than a softball, but some are the size of a small car.
4 Main Types of Satellites • Geosynchronous Orbiting – stays over same spot on earth (rotates at same speed as land under it) • Polar Orbiting – pole to pole orbit • Low Earth Orbiting – very low orbit • Elliptical Orbiting – elongated pole to pole orbit
Geosynchronous Orbiting • Geosynchronous – a satellite in an equatorial or near equatorial orbit • Has the same angular velocity of the earth • Geostationary satellite - a type of geosynchronous satellite that is in a west to east orbit at an altitude of 35,786 km above the equator. • Why can it only be at this altitude?
Geostationary Satellites • Ans: At this altitude it encircles the earth once every 24 hours, making its speed in orbit synchronous (or in sync) with earth’s rotation • Balance between gravitational force pulling it towards Earth and centripetal force away from it • Stays over same geographic area 24/7 • Examples: GOES East and West – take images of clouds from space from same vantage point.
GOES • GOES – Geostationary Operational Environmental Satellite • Observes the atmosphere in different wavelengths • Visible – captures visible light (useless at night but valuable during day) • Infrared – captures emitted long and short wave radiation • Water Vapor – Just an infrared detector that’s extra-sensitive to water vapor
Current GOES Images http://www.rap.ucar.edu/weather/satellite/
Polar Orbiting Satellites • Polar-Orbiting Satellite – a satellite with an orbit that lies in a plane passing through the center of the earth that traverses polar latitudes. • POES (Polar-Orbiting Operational Environmental Satellite)
More on POES • Polar orbiting satellites orbit earth in a couple hours. • They cover the entire earth with data breaks between paths • 2 or 3 polar orbiting satellites can work together to minimize data breaks.
Another Interesting Satellite • TRMM – Tropical Rainfall Measuring Mission • First satellite to carry a weather radar • Main web site: http://trmm.gsfc.nasa.gov/ • Images: http://trmm.gsfc.nasa.gov/images_dir/hurricane.html • Animations: http://trmm.gsfc.nasa.gov/images_dir/anim_hurricane.html
Satellite derived winds: • can track a cloud’s movement and get approx. winds at an estimated height. • Not as reliable as rawinsondes but it gives us more observations • http://cimss.ssec.wisc.edu/tropic/real-time/europe/winds/winds.html
Satellite Derived Indices • Great for forecasting severe weather and precipitation • Based on soundings that GOES makes • Not as accurate as rawinsondes, but again, it helps fill data voids and gives big picture • http://orbit-net.nesdis.noaa.gov/goes/soundings/html/fields.html
Satellite-Derived Soundings • Gives you soundings every hour instead of every 12 hours • http://orbit-net.nesdis.noaa.gov/goes/soundings/skewt/html/
For next time • Read Ch 9 – Hurricanes - REAL WEATHER! (I’m wishing for something interesting) • Homework 6 is posted • Reminder: Your grade is affected by your attendance. This is my one call to make sure you turn in anything you have not given me yet