NASA Launches Dawn Spacecraft on Asteroid Mission

[Hum]

CAPE CANAVERAL, FL (AP) -- NASA's Dawn spacecraft rocketed away Thursday toward an unprecedented double encounter in the asteroid belt. Scientists hope the mission sheds light on the early solar system by exploring the two largest bodies in the belt between Mars and Jupiter: an asteroid named Vesta and a dwarf planet the size of Texas named Ceres.

Dawn's mission is the world's first attempt to journey to a celestial body and orbit it, then travel to another and circle it as well. Ion-propulsion engines, once confined to science fiction, are making it possible.

''To me, this feels like the first real interplanetary spaceship,'' said Marc Rayman, chief engineer. ''This is the first time we've really had the capability to go someplace, stop, take a detailed look, spend our time there and then leave.''

The 3 billion-mile trip began a little after sunrise. The Delta II rocket thundered through a clear blue sky and headed southeast above the thick clouds over the horizon. A harvest moon was faintly visible in the west.

''Dawn, you're on your way. Good luck,'' Launch Control said once Dawn separated from its third rocket stage an hour later, right on cue. Already, the spacecraft was 4,000 miles from Earth.

Dawn won't reach Vesta, its first stop, until 2011, and Ceres, its second and last stop, until 2015.

Scientists chose the two targets not only because of their size but because they are so different from one another.

Vesta, an asteroid about the length of Arizona and not quite spherical, is dry and rocky and appears to have a surface of frozen lava. It's where many of the meteorites found on Earth came from. Ceres, upgraded to a dwarf planet just last year, is nearly spherical, icy and may have frost-covered poles. Both formed around the same time some 4 1/2 billion years ago.

Spacecraft have flown by asteroids before -- albeit much smaller -- and even orbited and landed on them, and more asteroid missions are on the horizon. But none has attempted to orbit two on the same mission, until Dawn.

''While these other asteroid missions are, I think, very exciting, I hope one doesn't confuse the kind of asteroids that Dawn is going to with the near-Earth asteroids and these other small bodies,'' said Rayman, who is based at Jet Propulsion Laboratory in Pasadena, Calif. ''I think many people think of asteroids as kind of little chips of rock. But the places that Dawn is going to really are more like worlds.''

Dawn has cameras, an infrared spectrometer and a gamma ray and neutron detector to probe the surfaces of Vesta and Ceres from orbit. It also has solar wings that measure nearly 65 feet from tip to tip, to generate power as it ventures farther from the sun.

Most importantly, Dawn has three ion engines that will provide a gentle yet increasingly accelerating thrust. Electrons will bombard Dawn's modest supply of xenon gas, and the resulting ions will shoot out into space, nudging the spacecraft along.

Even ''Star Wars'' had only twin ion engines with its T.I.E. Fighters, Rayman noted with a smile earlier in the week.

The mission costs $357 million, excluding the unpublicized price of the rocket.

source

[DocM]

Apparently Dawns ion propulsion got it to this point a tad early.

By the way: Delta II Heavy 7925 - around $200M a pop.

http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_070111.asp

July 7, 2011 - PASADENA, Calif. -- NASA's Dawn spacecraft obtained this image with its framing camera on July 1, 2011. It was taken from a distance of about 62,000 miles (100,000 kilometers) away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 5.8 miles (9.3 kilometers).

Dawn spacecraft

[neoadorable]

how long has it taken Dawn to get to Vesta? and what is New Horizons up to these days?

[DocM]

Dawn was launched on Sept. 27, 2007 using a Delta II-H - a little light for fast planetary missions. The ion drive makes up a bit for that and lets it break Vesta orbit to go to Ceres and stay there a while - the real cherry on this tree.

If it had a VASIMR drive things would have been a LOT faster, but we aren't quite there yet.

New Horizons is working fine and is past the orbit of Uranis at 20.44 AU from the Sun, 19.44 AU from Earth, and 11.75 AU to go before getting to Pluto. She's moving at about 15.60 km/s.

The New Horisins imager has been tested and it works. Below is a look-back shot it took after passing Jupiter....

[neoadorable]

thanks for the info Doc. getting a close look at Ceres will be neat, i remember when i was a kid it was still described and imagined as a rock-like asteroid, when now we know it's basically a small planet. good going Dawn!

ditto for New Horizons...didn't realize the gal was past Uranus! she's fast, or at least faster than anything else we've ever launched...so Pluto in a couple of years?

[LittleNeutrino Veteran]

exciting days, too bad the manned space program is almost dead.

[neoadorable]

it's about to get very lively again in the next few years, don't worry.

[Jason S. Global Moderator]

im realizing now how fast this satellite is w/ its ion engine, but just how much faster is it compared to "traditional" propulsion systems?

[DocM]

A traditional outer planet mission like the Voyagers or whatever would get a big kick from its chemical booster then coast all the way with no further acceleration. New Horizons and future missions will use smaller boosters and ion or plasma engines that thrust lightly but continuously, adding speed slowly but it adds up bigtime.

This ups efficiency considerably, which means you can carry far less fuel. The measure of rocket efficiency is specific impulse - ISP, which is measured in seconds and increases with efficiency. Your typical chemical rocket has an ISP of between 200 and about 450. Ion engines go to about 3,000 and VASIMR 3,000 - 50,000+ (variable: high thrust/low ISP or low thrust/high ISP)

Voyager 1 is still the fastest probe at 17.26 km/s, and New Horizons is at 15 km/s and using its engines to slow down for the Pluto encounter - this isn't a horse race. If it were New Horizons would pass Voyager 1 like it were standing still and be at that point far sooner than Voyager 1 took to get there.

The typical VASIMR Mars mission would do something like this too; spiraling around Earth to gain speed for a few weeks, then slingshot to Mars - thrusting continuously. Half-way there it would turn around and thrust away from Mars to decelerate - otherwise it would scoot by too fast to enter Mars orbit without large/heavy chemical rockets. It would then spiral in to a lower Mars orbit.

[Jason S. Global Moderator]

awesome post docm! good stuff (Y)

[DocM]

Dawn arrives at Vesta Saturday, and this New Scientist article dealves into the comppex orbital mechanics that cause it and Ceres to have an effect on Earth's orbit -

Link....

[neoadorable]

awesome that we made it to Vesta, really good news! but where are the photos, this is all NASA has on it i think http://www.nasa.gov/mission_pages/dawn/news/dawn20110716.html

[DocM]

It'll take a while to get pics of any quality - they're busy getting it into the orbit they want and the pics need digital processing before release.

[neoadorable]

yeah, i keep thinking taking photos in space and from telescopes is like using my phone...i need to remind myself it's not that simple! i'll be patient, hopefully we'll have something in a couple of days. i need them for my desktop background :laugh:

[DocM]

Here we go...

4 Vesta. Mound is a crater peak.

This anaglyph (stereo 3D) image of the asteroid Vesta was taken on July 9, 2011 by the framing camera instrument aboard NASA's Dawn spacecraft

Comparison to other asteroids

[neoadorable]

heh heh Vesta looks like a cookie in those pics...yum...thanks for posting these Doc, truly historic and incredible. i'm proud of Dawn and the folks behind her. Vesta's a big place, right? i mean, without looking it up, i'd guess what, 300 miles across?

[DocM]

4 Vesta's mean diameter is about 530 km or 330 miles.

[neoadorable]

yeee-haw! i'm still good for something! i was just 30 miles off and this was without looking it up! thanks for the confirmation Doc!

[DocM]

NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011. It was taken from a distance of about 3,200 miles (5,200 kilometers). Dawn entered orbit around Vesta on July 15, and will spend a year orbiting the body. The Dawn mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The framing cameras were built by the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, and the German Aerospace Center (DLR) Institute of Planetary Research, Berlin. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The Dark Side of Vesta Captured by Dawn

NASA's Dawn spacecraft obtained this image over the northern hemisphere with its framing camera on July 23, 2011. It was taken from a distance of about 3,200 miles (5,200 kilometers) away from the giant asteroid Vesta. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

[DocM]

Taken by Dawn's framing camera....

[guru]

Thanks Doc and lol at your sig

Wings on a spacecraft are like wheels on a boat.

[neoadorable]

great video of Vesta, man those track marks really speak of a major event in her past...she must have rubbed against something massive!

[DocM]

[neoadorable]

nice pics Doc, thanks a lot for posting them!

[DocM]

Dawn has lose a second reaction wheel (fine steering device.) Sounds like the bearing failed. They also say that without reaction wheels they can steer using the ion engines using differential thrust.