Shop Windows to the Universe

Warnings: The True Story of How Science Tamed the Weather by Mike Smith tells the story of our storm warning system. See our online store book collection.
This drawing shows Mars Global Surveyor taking measurements as it flew through the ionosphere of Mars during an early aerobraking pass. The orbit is shown by the dashed line. The ionosphere is shown by the shaded region circling the planet (not to scale).
Click on image for full size
Image from: NASA/JPL

Aerobraking

The Mars Global Surveyor reached Mars in September of 1997. But it didn't make it into its final mapping orbit until February 1999. What took so long?

Surveyor needed to reach a near-circular, low-altitude orbit in order to map the surface of Mars. In September 1997, the orbit of MGS was far from circular and at its farthest point in orbit, MGS was really far from Mars (56,000 kilometers above the surface)! Mission controllers needed MGS to be only ~400 kilometers above the surface. In order to adjust the orbit of MGS, the controllers used aerobraking.

Controllers were going to send MGS through the atmosphere of Mars to slow it down. During these atmospheric passes, air resistance generated by the solar panels would slow the spacecraft and gradually lower its orbit. Surveyor was to use this aerobraking technique to lower the high point of its orbit from the initial 56,000 kilometers in altitude to about 400 kilometers. This aerobraking would also force the spacecraft into a near-circular orbit. Originally, this was only suppose to take 4 months.

Unfortunately, one of the solar panels (which are used during aerobraking!) broke during the launch of MGS. This solar panel got stuck and wouldn't open all the way. Controllers had to pay special attention to this broken solar panel. But, it was decided that aerobraking could still be used...only things would need to go much slower! That is why it took so long for MGS to reach its correct orbit for mapping.

Aerobraking was started in September 1998 and lasted until early February 1999 - that's almost 700 orbits around the planet! But, finally the mapping orbit was reached on February 4, 1999. Aerobraking was completed on that day and MGS was pulled up out of the atmosphere for good. In 2001, the spacecraft's altitude has ranged from about 310 km - 430 km.

Last modified May 11, 2001 by Jennifer Bergman.

Shop Windows to the Universe Science Store!

Our online store includes fun classroom activities for you and your students. Issues of NESTA's quarterly journal, The Earth Scientist are also full of classroom activities on different topics in Earth and space science!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

The Martian Ionosphere

The Martian ionosphere is a layer of gas that is very high up above Mars and is composed of ions and electrons. It extends from about 75 miles up to several hundred miles up above the surface. It is shown...more

Mars Odyssey

The Mars Odyssey was launched April 7, 2001, from Florida. After a six-month, 285 million-mile journey, the Odyssey arrived at Mars on October 24, 2001. The Odyssey is in its aerobraking phase right now....more

Mars 2005

The Mars 2005 mission is still in the planning stages. It is set to launch in the year 2005. ...more

Aerobraking

The Mars Global Surveyor reached Mars in September of 1997. But it didn't make it into its final mapping orbit until February 1999. What took so long? Surveyor needed to reach a near-circular, low-altitude...more

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. This instrument is called an altimeter, or "altitude-meter". The picture to the left shows Mars Global Surveyor's measurement...more

Mars Global Surveyor Measures Volcano Altitudes

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

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF