Keeping an Eye on Space Rocks
Part IV: The Early Bird

Star chart
Star chart
As soon as a near-Earth object is discovered, scientists around the world begin tracking its orbital path.

Several days of observations are required before reliable and precise information on its orbit can be developed.

In the event that we do observe a near-Earth object whose future motion shows it to be a threat, understanding the objects size, shape composition and structure will help find the best way to avoid an impact.


Space surveillance, Maui, Hawaii spacer Oschin telescope spacer Lowell observatory spacer Steward observatory
Space surveillance in Maui, Hawaii. Oschin telescope. Palomar Mountain, California. Image courtesy: Alain Maury. Lowell observatory. Near-Earth object survey, Flagstaff, Arizona. Steward observatory. Kitt Peak, Arizona.

Near-Earth objects
White arrows indicate movement of a near-Earth object with respect to the stars.

NASAs goal over the next few years is to discover at least 90 percent of all near-Earth objects with diameters larger than one kilometer (a little more than one-half mile ). Several teams around the world routinely search the skies for as-yet undiscovered asteroids and comets. If a near-Earth object with a potentially hazardous orbital path is discovered, it may be initially classified as a risk until further observations are available. With these additional observations, a better estimation of its orbital path usually occurs a few days after discovery, and the initial risk is then downgraded. Scientists calculate the orbital motions of all newly discovered objects for 100 years or more into the future.


Stopping an asteroid with rockets
Artist's concept of a possible diversion technique for an Earth-threatening object.

If an object were to threaten Earth, it would only be necessary to move the object by one Earth radius, a very small distance in space terms. One idea suggested for a smaller asteroid is to anchor a shuttle-type engine onto the moving space rock and gently speed it up or slow it down. Another possible strategy would be to attach solar sails to a potentially hazardous body and allow the gentle pressure of sunlight to deflect the threatening asteroid away from Earth.





Leonid meteor shower spacer model of the asteroid, Vesta spacer Ceres spacer Artist concept of Deep Impact
Artist concept of the Dawn spacecraft, which launched in 2007. Dawn will be studying the solar system's largest asteroid, Vesta.The image above is a model of Vesta. Dawn will also be studying a "dwarf" planet called Ceres. By design, Deep Impact’s impactor was “run over” by comet Tempel 1’s nucleus in 2005.

Comet Tempel one impact spacer Artist's concept of Stardust spacer Capsule being carried spacer Samples of cometary material
The impact gave scientists information on what makes up a comet. The Deep Impact spacecraft will continue on its journey and fly past comet Hartley 2 in 2010. Stardust flew through the cloud of dust surrounding comet Wild 2. The Stardust spacecraft will continue on its journey and fly past comet Tempel 1 in 2011 and examine the crater created by the Deep Impact mission. The Stardust return capsule is being taken to a nearby facility. Samples of the cometary material were returned to Earth for study in 2006.

Artist concept of Japan's Hayabusa spacecraft spacer Artist concept of Rosetta spacecraft spacer Artist concept of Rosetta spacecraft landing spacer  
In the Fall of 2005, Japan's Hayabusa spacecraft made scientific observations of asteroid Itokawa. The European Space Agency's Rosetta spacecraft is traveling to comet 67P/Churyumov-Gerasimenko. Rosetta will reach the comet in 2014 and eventually land on it.  

Missions to comets and asteroids help explain the composition and structure of these bodies. Findings from the missions help us better understand the solar systems formation, the potential use of asteroids and comets in future interplanetary exploration, and the best methods for deterring objects with potentially hazardous orbit paths.

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