Thursday, April 01, 2010

50 years of weather satellites

Fifty years ago today, the world’s first weather satellite lifted off from Cape Canaveral, Fla., and opened a new and exciting dimension in weather forecasting. 
Read the full NOAA story, including pictures from the first weather satellite, TIROS, and the recently launched NOAA-19  satellite.

I found it very interesting that TIROS, a polar-orbiting satellite, was launched from Cape Canaveral, FL instead of Vandenberg, CA.

Here's a blurb I wrote October 2009 for my daughter's 5th grade class.  (In California, 5th graders study both space and meteorology so this was a perfect topic.)

"If you look at the current launch manifest (schedule of worldwide launches), you can see that there will be two visible launches this month, Worldview 2 and DMSP 18.

Satellites in a series are numbered.  Thus, worldview 2 is the second in the series.  DMSP, the Defense Meteorological Satellite Program, is run jointly by the Air Force and the Navy.  DMSP 18 is the 18th satellite in the series.

Satellites bound for polar (over the poles) orbits tend to be launched at VAFB. It has a beach with nothing but ocean to the south. That makes it ideal, because there will be no people in harm's way in
case of a mishap.

People who are interested in watching the satellites/rockets fly by should monitor the Spaceflight Now website for last minute changes.

It gives launch window times in Greenwich mean time and EDT.  For example, DMSP should launch at about 12:12 EDT or 9:12 PDT.  It will fly by us a couple of minutes after takeoff.  I see on Spaceflight Now that they have a twitter feed.  Or spectators can do it the old fashioned way by viewing the website  on their iphones. ;-)

Perhaps the class wants to have an unofficial meetup at the Manhattan Beach Pier for the  DMSP launch? It's on a Sunday morning.

You might want to mention to the kids that a sunsynchronous orbit means that the satellite will fly in the same local time plane (same relative position to the sun) all the time. (Really 2 local times, one dayside, one nightside.)

So DMSP, which launches at 9:12, will always stay close to 9:12 in the morning or evening. Worldview, which launches around noon, will always fly around noon and midnight. That's because a global imaging mission like Worldview gets the best view when directly overhead, at noon. The DMSP satellite wants to view the early morning and evening changes in the ionosphere, which is critical for the USAF which runs GPS and Milsatcom. Those satellites are very sensitive to changes in the ionosphere.

Satellites bound for geosynchronous and low inclination (equatorial) orbits tend to launch from Cape Canaveral in FL or Kwajalein Island.

I want the kids to understand that there are different types of orbits.  The function of the satellite determines the orbit, and that the desired orbit determines the launch site and time.  That should be enough for a 5th grader.

The meteorologist in me wants the kids to also learn that there are two main types of weather satellites. There are high-flying geosynchronous ones like GOES East and West, that fly above the equator and look over the same spot all the time.  And there are lower-flying ones that go over the poles, like DMSP-## and NOAA-##.  The lower ones give more detail, but view a much smaller region."

The distance from earth also determine the wavelengths that the satellites can monitor (but that is a more advanced concept, best saved for HS or college students).

You can view satellites with your children quite easily, even without a telescope, if you can get away from the city lights.

I've explained in DIY Satellite Tracking how to predict when satellites will be viewable.  Pick a polar-orbiting satellite that flies in the early evening.  They will be in the sun about 70% of their orbit.  In the early evening, the sky will be dark, but the satellite will be sunlit.  Weather satellites are perfect for this, because their ~100 minute orbit is slow enough for you to view, but fast enough so they won't be mistaken for a star.  Have fun!

1 comment:

  1. Thanks for posting this. My son is studying this in his college classes right now


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