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  Hello VestaJul 19, 2011 7:01 AM PDT | url
 
Added 1 new A* page:Thanks to an A* reader on Facebook for pointing me to updates on the Dawn spacecraft, which over the past few days successfully entered the first human-engineered orbit of an asteroid--the giant asteroid Vesta in the Mars-Jupiter asteroid belt--and then returned the first detailed photo of Vesta ever released from an orbital distance of about 15,000 kilometers:
 
Image
image by NASA/JPL-Caltech/UCLA/MPS/DLR/IDA (source)
 
Let the speculation begin: is Vesta, at 530 km in diameter, rounded enough by the pull of its own gravity to quality as a dwarf planet? Looks pretty irregular along the right side in that photo, but I have no idea exactly how regular it would have to be--hopefully the smart people will be figuring that out shortly, although I wouldn't be surprised if any official status change takes a while.
 
That second article mentions that Dawn "also accomplished the largest propulsive acceleration of any spacecraft, with a change in velocity of more than 4.2 miles per second (6.7 kilometers per second)..." The Wikipedia page clarifies the significance somewhat:
 
To get to Vesta, Dawn is allocated 275 kg (606 lb) xenon, with another 110 kg (243 lb) to reach Ceres, out of a total capacity of 425 kg (937 pounds) of on-board propellant. With the propellant it carries, it can perform a velocity change of over 10 km/s, far more than any other spacecraft has done with onboard propellant after separation from the launch rocket. Dawn is NASA’s first purely exploratory mission to use ion propulsion engines.

Because those ion engines are so efficient, Dawn is capable of far more independent propulsion than any other spacecraft. For instance, Dawn began "long-term cruise propulsion" on December 17th, 2007, and completed that first thrusting phase on October 31, 2008; "Dawn spent 270 days, or 85% of this phase, using its thrusters," and "expended less than 72 kilograms (158 pounds) of xenon propellant for a total change in velocity of 1.81 kilometers per second (4050 miles per hour)." Hm! Now they gotta get some you can use from cars on long freeway trips, and we'll have this energy crisis all taken care of.
 
 
 
 
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