Dawn's Smooth Move   
       
   August 1, 2011: When a NASA spacecraft goes into orbit around a new world for   
   the first time, the control room is usually packed to capacity with   
   scientists, engineers, and dignitaries ready to leap and shout when the   
   retro-rockets fire. It's a big, noisy event.   
       
   July 15, 2011, was one of those days. NASA's Dawn spacecraft approached Vesta   
   and became the first probe from Earth to orbit a main belt asteroid. Dawn's   
   cameras revealed a desolate world of transcendent beauty, thrilling everyone   
   who worked on the project.   
       
   Needless to say, the control room was .... silent?   
       
   "Actually it was empty," says Dawn Chief Engineer Marc Rayman of JPL. "Dawn   
   entered orbit on a Friday night; I myself was out dancing with my wife and   
   friends."   
   [...]   
   Using its framing camera, Dawn obtained this image of Vesta on July 24, 2011,   
   from a distance of about 3,200 miles (5,200 kilometers). The three   
   vertically-aligned craters on the left have been nicknamed "the snowman" by   
   camera team members. Press release:Dawn Begins Science Orbits of Vesta.   
   What gives? Rayman, an avid folk dancer, explains: "Our mission has a unique   
   choreography."   
       
   Indeed, Dawn has its own way of doing things. While most spacecraft blast off   
   Earth atop a firestorm of conventional rocket exhaust, then coast to their   
   destinations with engines turned off to conserve fuel, Dawn was able to   
   continue thrusting throughout its voyage. Fuel-efficient ion engines gently   
   propelled the spacecraft toward Vesta for more than three years, never   
   exerting more force than the weight of a feather held in your open palm yet,   
   over time, gathering enough speed to catch an asteroid racing halfway across   
   the solar system.   
       
   With engines firing almost constantly, mission controllers were able to   
   actively steer the probe, gradually reshaping Dawn's orbit around the sun   
   until it matched the orbit of Vesta itself. Meeting Vesta for orbital   
   insertion wasn't a jarring encounter of mismatched velocities. It was more   
   like two dancers merging in practiced rhythm to a familiar tune.   
       
   "Dawn did not miss a beat as it flew into Vesta's grasp," says Rayman. "The   
   spacecraft moved gently into orbit with the same grace it has displayed during   
   its nearly 1000 days of ion propulsion through the solar system."   
       
   The capture was so smooth, so low-key, that personnel felt no particular need   
   to monitor the probe's operation. "I really was out dancing," says Rayman,   
   "confident that the pas de deux being performed 188 million kilometers away   
   would be executed with graceful beauty and flawless precision."   
       
   Calculations show that the moment of "orbit insertion" occurred on Friday   
   night, July 15th, around 9:47 pm PDT. At that moment, Dawn's orbit around the   
   sun finally was so close to that of Vesta that the protoplanet's gravity could   
   take hold of it. Radio signals picked up on schedule by the Deep Space Network   
   later confirmed that the spaceship and asteroid were truly a pair.   
       
   Dawn will spend the next year circling Vesta in a series of descending passes,   
   bringing the giant asteroid's ancient surface ever closer to Dawn's cameras   
   and other science instruments. Because Vesta is a relic of long-ago planet   
   formation, the history of our solar system could be revealed under Dawn's   
   careful scrutiny.   
       
   "This really beautiful dance," says Rayman, "is just getting started."   
       
       
   Author: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   Dawn -- JPL home page   
       
   Dawn --- NASA HQ home page   
       
   Dawn Spacecraft Begins Science Orbits of Vesta   
       
   Credits: Dawn launched in September 2007. Following a year at Vesta, the   
   spacecraft will depart in July 2012 for Ceres, where it will arrive in 2015.   
   Dawn's mission to Vesta and Ceres is managed by JPL for NASA's Science Mission   
   Directorate in Washington. JPL is a division of the California Institute of   
   Technology in Pasadena. Dawn is a project of the directorate's Discovery   
   Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala.   
   UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp.   
   in Dulles, Va., designed and built the spacecraft. The German Aerospace   
   Center, the Max Planck Institute for Solar System Research, the Italian Space   
   Agency and the Italian National Astrophysical Institute are international   
   partners on the mission team.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.64   
    * Origin: NCS BBS (1:3828/7)