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The Mars Global Surveyor spacecraft measures The Tharsis Ridge.
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NASA/JPL

Altimetry

Altimetry is a term which describes a method of measuring the altitudes of things with spacecraft. It is usually performed with a laser. Lasers bounce beams of light from the surface and back to the spacecraft to measure the heights of mountains and depths of valleys on distant planets. This is even done for our own planet. The figure shown here shows altimeter results from the Mars Global Surveyor spacecraft. The red line shows the relative heights of the ground underneath the spacecraft.

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Cool It! Game

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Mars Global Surveyor Measures Olympus Mons

Mars Global Surveyor carries an instrument which measures the heights of things. This instrument is called an altimeter, or "altitude-meter". The graph to the left shows the results returned from Mars...more

Mars Global Surveyor Measures Martian Global Hemispheres

Mars Global Surveyor carries an instrument which measures the heights of things. The picture to the left shows Mars Global Surveyor's measurement of the size of the giant cliff which separates the southern...more

Mars Global Surveyor Measures Volcano Altitudes

Mars Global Surveyor carries an instrument which measures the heights of things. The picture to the left shows the results returned from Mars Global Surveyor's measurement of the size of some of the Martian...more

Instruments of the Mars Global Surveyor Mission

It has been more than 30 years since America's first missions to Mars. Here are some of the instruments carried by the Mars Global Surveyor (called MGS for short). These instruments are designed to study...more

AU

AU stands for Astronomical Units. It is an easy way to measure large distances in space. It is the distance between the Earth and the Sun, which is about 93 million miles. For really big distances, we...more

The Spiral of the IMF

The solar wind is formed as the Sun's top layer blows off into space. It carries magnetic fields still attached to the Sun. Streams appear to flow into space as if they are spiraling out from the Sun,...more

Spiral Path of Material

For a planet to be affected by a blob of material being ejected by the sun, the planet must be in the path of the blob, as shown in this picture. The Earth and its magnetosphere are shown in the bottom...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA