Astronomy/Satellite tracks

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Expert: - 7/20/2009


Question
Why are tracks of satellites and other spacecraft appear wavy when shown on a tracking map (up/down wavy track)??

Answer
Hi Jim,
Oh, you mean the sine waves across a flat 2-dimensional map of the entire Earth?  Because that's the actual ground track of a satellite in a fixed orbit around the Earth.  You see, the satellite orbit is fixed with the Earth turning under it at 15 degrees eastward every hour.

So if you take a rotating spherical ball with a satellite in a fixed orbit circling it, and stretch the ball out on a flat surface in
2 dimensions, the ground track of the satellite will project a
sine wave over that surface. And notice that the sine wave migrates
westward across the 2 dimensional map due to the Earth's rotation.

That's an easier projection method than using a 3 dimensional globe with the satellite's fixed orbit suspended over the rotating globe....so that's why they do it that way...for convenience.
(Plus all TV screens are 2 dimensional, not 3 dimensional as yet.
So the 2 D projection is the only way to easily display it.)
Hope this helps,
Clear Skies,
tom

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Tom Whiting

Expertise

Astronomy has been my hobby/pasttime for over 50 years.  Currently own 3 telescopes, the largest of which is a 30 inch Newtonian truss Dob that is portable.I taught Astronomy/Meteorology at the University Level for 13 years before retiring in 1995. Being retired and home most of the time, I am able to answer all questions relatively quickly, unless it's a new moon weekend with good observing conditions.  No astrology questions please, or questions about alleged UFO picture identifications.

Experience

Experience: Astronomy has been my hobby and study for over 50 years. We currently now own a 30 inch portable telescope (Updated - Pennsylvania`s largest portable telescope). It can be seen on our website at:http://www.velocity.net/~bwhiting and also attend several regional starparties during the year, and have been on 5 total solar eclipse expeditions.

Organizations: President, Erie County Mobile Observers Group for over 15 years.

Publications: Wrote the "Over Erie Skies" newspaper article in our local newspaper for 11 years (1975-86).

Education: Masters Degree- Taught at the University level for 13 years. Retired 20 years -USAF Pilot - KC-135 with 180 combat missions;  Also Eagle Scout, Philmont staff 2 Yrs, Order of Arrow Lodge Chief, Ham Radio (inactive).

Awards: two discoveries: The mini-coathanger asterism in Ursa Minor (the little dipper) And the mini-ladle- another asterism in the bowl of Ursa Minor. Clients: Currently President of the ECMOG as mentioned above.

Education/Credentials
BS  Metallurgical Engineering Grove City College, PAMaster's Degree, Gannon University, Erie, PA Also retired USAF pilot, 20 years.

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