Dawn Cruise |
Dawn Cruise |
Sep 27 2007, 12:31 PM
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#1
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Member Group: Members Posts: 100 Joined: 11-October 04 From: Oxford, UK (Glasgow by birth) Member No.: 101 |
Pushing out of Earth orbit now...........
-------------------- "There are 10 types of people in the world - those who understand binary code, and those who don't."
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Aug 30 2008, 01:36 AM
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#2
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Member Group: Members Posts: 340 Joined: 11-April 08 From: Sydney, Australia Member No.: 4093 |
My two cents worth:
Dawn is picking up speed from the flyby. As this happens halfway between periapsis (closest point to sun) and apoapsis (farthest point to sun), both are raised. It also rotates the apsises clockwise, so Dawn will be at periapsis shortly after the Mars encounter. By thrusting then, it efficiently raises the apoapsis further. It also increases the inclination from 1.9 to 6.5 degrees, which I think would be costly to do without a gravity assist. I dont think it makes a difference whether the flyby is inbound or outbound, you gain speed w.r.t. sun as long as you fly behind Mars. Horizons gives the following orbital elements w.r.t. solar system barycenter (Mars flyby as inferred from Horizons data is around Feb 12): CODE 1 Feb 2009 28 Feb 2009 Change
Eccentricity 0.160521 0.132016 orbit gets rounder Periapsis (km) 180,738,278 203,950,288 +23 million km Apoapsis (km) 249,858,224 265,989,955 +16 million km Inclination 1.9249 6.5018 gets steeper -------------------- |
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