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Why So Far? Sep23, 1999
By Greg Clark
Staff Writer
posted: 09:47 am ET
23 September 1999
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Although Mars moves in an elliptical orbit that averages about 141 million miles (228 million kilometers) from the sun, the Mars Climate Orbiter traveled some 416 million miles on its way to Mars from EarthAlthoughMars moves in an elliptical orbit that averages about 141 million miles(228 million kilometers) from the sun, the Mars Climate Orbiter traveledsome 416 million miles on its way to Mars from Earth.When the Mars Climate orbiterwas launched on December 11 last year, Earth and Mars were just 136.6 millionmiles from each other. Why then did the orbiter have to go so far to getthere? Did it take the long way around? Actually, yes. Because both planets aremoving, it is impossible to fire a spacecraft on a direct line to Marsand have it arrive at the planet. A spacecraft launched on such a trajectorywould get to a point in space 136.6 million miles from where Earth wasat launch, and find Mars long gone, having sped ahead in its orbit aroundthe sun. Calculating the distancetraveled to Mars requires an addition that figures not just the distancebetween the two planets, but the distance the craft travels around thesolar system on its way.Its like driving down thehighway and tossing an orange to your buddy who is in the bed of a pickuptruck driving next to you. Although the truck may be only 10 feet away,you have to add the distance the orange moved down the highway while itwas in the air. The same goes for the spacecraft. In this case, to get toMars, the climate orbiter needed to travel more than half way around thesun during its journey. Clickhere to go to space.com's Mars page
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