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/soundi

ngs/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