Artist concept showing the Dawn spacecraft with Ceres and Vesta.
Image: William K. Hartmann Courtesy of UCLA
In Brief
On February 17 at about 7:28 P.M. Eastern Standard Time, the spacecraft Dawn received a speed boost and a change of direction in the form of a gravity-assist from Mars. The craft slingshot past the planet, using it (rather than its own precious fuel) to adjust its trajectory, and will continue to the first stop in its journey, the asteroid Vesta. The Dawn mission has gone so smoothly that after almost a year and a half of travel, it required no course correction as it neared the Red Planet. Now that it has passed Mars, it will coast for about four months before powering up its ion drive engine and traveling another 26 months to Vesta.
Mission controllers have compared the Dawn mission with that of the fictional space voyages depicted on Star Trek. Dawn project system engineer Marc Rayman says, "Dawn is like the first real interplanetary spaceship! Many spacecraft have gathered data at multiple bodies, but Dawn will be the first to go somewhere, go into orbit, and be able to linger there, and then travel to another body and do the same thing." To do this, Dawn is powered by an ion plasma propulsion engine. Unlike on the starship Enterprise, however, where venting plasma was sometimes a bad sign, Dawn will rely on the controlled venting of its plasma thrust to continuously accelerate toward Vesta. On its way, the spacecraft's ion engine will speed it up to about 24,600 miles per hour (11 kilometers per second), far more than any spacecraft has ever achieved.
Dawn will place itself in orbit around Vesta in August 2011 and will spend some nine months collecting data that will help us to better understand the origin of our solar system. It will then leave orbit and begin the second, and longest, leg of its trip: a two-year, nine-month journey to the dwarf planet Ceres, the largest body in the asteroid belt. After several more months of gathering data, the Dawn mission will come to an end.
And what will happen to Dawn? According to Rayman, "because of the possibility of there being a substantial inventory of water at that mysterious body, we have 'planetary protection' requirements." (Did someone say "Prime Directive"?)
Essentially this means that Dawn will not be sent hurtling into Ceres. Rayman continues: "Now there is no reason whatsoever to believe there is life on Ceres, but there may be chemistry occurring there that is related to the chemistry that preceded the development of life on Earth—and perhaps elsewhere! Therefore, to protect that fascinating environment, we are currently required to leave the spacecraft in an orbit in which it will not crash into Ceres for at least 20 years."
Will Dawn, then, go out with a whimper? Maybe not. If more funding became available, and there is enough leftover xenon fuel in the ion engine's tank, new objectives for Dawn might be considered—perhaps to again boldly go on where no spacecraft has gone before.
On February 17 at about 7:28 P.M. Eastern Standard Time, the spacecraft Dawn received a speed boost and a change of direction in the form of a gravity-assist from Mars. The craft slingshot past the planet, using it (rather than its own precious fuel) to adjust its trajectory, and will continue to the first stop in its journey, the asteroid Vesta. The Dawn mission has gone so smoothly that after almost a year and a half of travel, it required no course correction as it neared the Red Planet. Now that it has passed Mars, it will coast for about four months before powering up its ion drive engine and traveling another 26 months to Vesta.
Mission controllers have compared the Dawn mission with that of the fictional space voyages depicted on Star Trek. Dawn project system engineer Marc Rayman says, "Dawn is like the first real interplanetary spaceship! Many spacecraft have gathered data at multiple bodies, but Dawn will be the first to go somewhere, go into orbit, and be able to linger there, and then travel to another body and do the same thing." To do this, Dawn is powered by an ion plasma propulsion engine. Unlike on the starship Enterprise, however, where venting plasma was sometimes a bad sign, Dawn will rely on the controlled venting of its plasma thrust to continuously accelerate toward Vesta. On its way, the spacecraft's ion engine will speed it up to about 24,600 miles per hour (11 kilometers per second), far more than any spacecraft has ever achieved.
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Dawn will place itself in orbit around Vesta in August 2011 and will spend some nine months collecting data that will help us to better understand the origin of our solar system. It will then leave orbit and begin the second, and longest, leg of its trip: a two-year, nine-month journey to the dwarf planet Ceres, the largest body in the asteroid belt. After several more months of gathering data, the Dawn mission will come to an end.
And what will happen to Dawn? According to Rayman, "because of the possibility of there being a substantial inventory of water at that mysterious body, we have 'planetary protection' requirements." (Did someone say "Prime Directive"?)
Essentially this means that Dawn will not be sent hurtling into Ceres. Rayman continues: "Now there is no reason whatsoever to believe there is life on Ceres, but there may be chemistry occurring there that is related to the chemistry that preceded the development of life on Earth—and perhaps elsewhere! Therefore, to protect that fascinating environment, we are currently required to leave the spacecraft in an orbit in which it will not crash into Ceres for at least 20 years."
Will Dawn, then, go out with a whimper? Maybe not. If more funding became available, and there is enough leftover xenon fuel in the ion engine's tank, new objectives for Dawn might be considered—perhaps to again boldly go on where no spacecraft has gone before.
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7 Comments
Add CommentPretty impressive that there weren't any course corrections needed over such a long journey. Hopefully, the rest of the mission goes just as smoothly.
Reply | Report Abuse | Link to thisWhat purpose is there in letting the spacecraft orbiting Ceres for about 20 years instead of letting it fall immediately into the dwarf planet? Of course we want to keep intact the environment in Ceres or go to lengths to disturb it in the least possible way. I do not think we are going to go there and retrieve it before it crashes onto the planet. Also I do not think the designers of the project are irresponsible. There should be a reason I can not elucidate with the information at hand.
Reply | Report Abuse | Link to this11 Km/s is Earth's escape velocity. The figure is likely to be wrong, and is _certainly_ not the fastest ever reached by space probes: Voyager 1 is flying at 17Km/s, and New Horizons is currently traveling at nearly 17 Km/s as well.
Reply | Report Abuse | Link to thisOh, for crying out loud. If crashing a tiny spacecraft into Ceres causes enough of a catastrophe to wipe out any burgeoning life there, then solar flares and micrometeroid bombardment have already done the work for us.
Reply | Report Abuse | Link to thisCan we just let go of this syndrome where castrate ourselves to protect some fictional pristine wilderness that never did and never will exist outside of some treehugger's mushroom induced hallucination?
Well said, frgough. i'm with you on that one.
Reply | Report Abuse | Link to thisVery interesting.
Reply | Report Abuse | Link to this"Therefore, to protect that fascinating environment, we are currently required to leave the spacecraft in an orbit in which it will not crash into Ceres for at least 20 years."
Reply | Report Abuse | Link to thisOK, then, we understand that it's important not to destroy that "fascinating environment" now, but it's OK 20 years from now - which is less than an eye-blink over any reasonable timescale where evolution might be happening.
But hey, right now, "environment" is the holy of holies. No matter where it is - here, there, everywhere - we must only approach it with the utmost reverence, and even then, while beating our breasts in admission of the terrible guilt of having caused global warming and vile pollution on this planet.