Lunar explorers will need GPS system
http://www.msnbc.msn.com/id/24390142/ [2008-7-21]
Tag : communication relay
One potential path a lunar communication satellite (com-sat) couldtake is by following a "frozen orbit" around the moon. In such anorbit the satellite's orbital characteristics remain constantdespite prods from the moon's lumpy gravity field .
This uneven gravity field is due to mascons, large concentrationsof mass in the lunar crust.
"You can think of it (a frozen orbit) as a roller coaster ride overthe lunar mascons. If you pick the path just right, the tugs andpulls of the mascons will end up cancelling each other out. At theend, the spacecraft will be right back where it started in theorbit," Hill told SPACE.com .
An alternative to the bumpy ride of the frozen orbit is to place acom-sat in a halo orbit around a region known as a Lagrange point.
There are five Lagrange points in the Earth-moon system marking the region where a spacecraft canremain stationary relative to the Earth and moon.
One potential path a lunar communication satellite (com-sat) couldtake is by following a "frozen orbit" around the moon. In such anorbit the satellite's orbital characteristics remain constantdespite prods from the moon's lumpy gravity field .
This uneven gravity field is due to mascons, large concentrationsof mass in the lunar crust.
"You can think of it (a frozen orbit) as a roller coaster ride overthe lunar mascons. If you pick the path just right, the tugs andpulls of the mascons will end up cancelling each other out. At theend, the spacecraft will be right back where it started in theorbit," Hill told SPACE.com .
An alternative to the bumpy ride of the frozen orbit is to place acom-sat in a halo orbit around a region known as a Lagrange point.
There are five Lagrange points in the Earth-moon system marking the region where a spacecraft canremain stationary relative to the Earth and moon.
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