Transcript Lecture 7 (10/15) METR 1111

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
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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/hurrican
e.html
• Animations:
http://trmm.gsfc.nasa.gov/images_dir/anim_hurric
ane.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/realtime/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://orbitnet.nesdis.noaa.gov/goes/soundings/html/fie
lds.html
Satellite-Derived Soundings
• Gives you soundings every hour instead of
every 12 hours
• http://orbitnet.nesdis.noaa.gov/goes/soundings/skewt/h
tml/
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