(LOS ANGELES) — NASA this weekend is set to launch a spacecraft that will journey to the asteroid belt that lies between Mars and Jupiter, a mission that involves a rendezvous with two of the solar system's largest asteroids.
Seeking clues about the birth of the solar system, the Dawn spacecraft will first encounter Vesta, the smaller of the two bodies, four years from now. In 2015, it will meet up with Ceres, which carries the status of both asteroid and, like Pluto, dwarf planet.
"We're trying to go back in time as well as to go out there in space," said planetary scientist Christopher Russell of University of California, Los Angeles, who is heading up the mission.
Weather permitting, Dawn is set to blast off Sunday afternoon from Cape Canaveral, Fla., on a Delta II rocket. The launch caps a tumultuous effort in which the $344 million mission was killed last year because of cost overruns and technical problems.
Ultimately, though, the Jet Propulsion Laboratory in Pasadena, which manages the spacecraft, appealed to NASA Administrator Michael Griffin and got the project revived.
Adding to the drama, Ceres briefly flirted with planethood during last summer's scientific debate about whether Pluto is a planet. Both Pluto and Ceres were finally classified dwarf planets.
Vesta and Ceres are believed to have evolved in different parts of the solar system more than 4.5 billion years ago around the same time as the formation of the rocky planets including Mercury, Venus, Earth and Mars. Scientists believe the asteroids' growth was stunted by Jupiter's gravitational pull and never had the chance to become full-fledged planets.
Images by the Hubble Space Telescope show Vesta and Ceres as geologically diverse.
Mysteries abound: Why are Vesta and Ceres so different? How do size and water affect planet formation? What does the evolution of the asteroids say about Earth's formation?
Vesta, which measures 326 miles across, is dry and pocked with a deep impact crater in its southern hemisphere. By contrast, Ceres, about twice as large as Vesta, has a dusty surface covered by what appears to be an ice shell and may even contain water inside.
When Dawn reaches each asteroid, first Vesta in 2011, it will orbit each body, photographing the surface and studying the asteroid's interior makeup, density and magnetism. Pictures and data will be sent back to Earth.
Dawn will be powered by ion propulsion instead of conventional rocket fuel, making it more fuel-efficient and allowing it to cruise between the asteroids and lower itself to about 125 miles above the surface to study them in depth.
Although previous spacecraft have explored smaller asteroids, researchers hope Dawn will shed light on the solar system's origins.
"If you want to understand the Earth, it's important to understand how it came to be and that's where asteroids come in. They're the building blocks," said Jay Melosh, a planetary geologist at the University of Arizona who has no role of the Dawn mission.
| NASA's
Asteroid Probe Set for Monday Launch By Tariq Malik Staff Writer posted: 6 July 2007 3:43 p.m. ET |
NASA is hoping for a Monday liftoff for the Dawn spacecraft, a probe bound to visit the two largest asteroids in the solar system.
Dawn is now set to ride a United Launch Alliance Delta 2 rocket into space July 9 at 3:56 p.m. EDT (1956 GMT) after new issues scrapped plans for a Sunday liftoff.
Mechanical difficulties with a telemetry relay aircraft, combined with the unavailability of a tracking ship and an unfavorable weather forecast for rocket fueling, delayed plans for a Sunday launch, NASA officials said. Weather forecasts for Monday improve to a 60 percent chance of favorable liftoff conditions, they added.
Dawn's planned Monday launch will kick off an eight-year trip to Vesta and Ceres, the two largest space rocks in the Asteroid Belt that rings the Sun between the planets Mars and Jupiter. The $449 million mission will mark NASA's first to orbit two different planetary bodies, and will study space rocks that formed about 4.6 billion years ago while the solar system was still young.
"What's exciting to me is that this is comparative planetology at its best," said David Lindstrom, NASA's Dawn program scientist, during a Friday briefing. "We truly are going back in time; back to the dawn of the solar system."
Powered by an ion drive, Dawn is due to enter orbit around Vesta in October 2011 and use three onboard instruments to study the space rock's surface before heading off towards a February 2015 orbital rendezvous with Ceres.
Vesta is a dense body scarred by an ancient impact that, researchers believe, sent a myriad of small meteorites falling to Earth. Ceres, with its spherical shape and a diameter about 600 miles (almost 1,000 kilometers) wide, is so large it is considered to be a dwarf planet and may sport a subterranean cache of ice or water, mission scientists added.
Examining the differences between dense, bright Vesta and the dimmer, less-dense Ceres may yield new answers for researchers studying the formation of planets, NASA officials said.
Dawn's ability to shift from one target to another hinges on its three xenon ion-driven thrusters, which allow the probe to maneuver with less propellant than that required for chemical-based rockets.
"We couldn't do this mission without the ion drive," said Mark Sykes, a Dawn mission co-investigator from the Planetary Science Institute at the University of Arizona. "It's an extremely flexible way of moving around the solar system."
NASA now has until July 19, a window eight days longer than first announced, to launch Dawn before standing down to allow preparations for the planned Aug. 3 liftoff of Phoenix, the space agency's next Mars lander mission.
"We're kind of just threading the needle with these two launches," Kurt Lindstrom, NASA's Dawn program executive, told SPACE.com.
The next opportunity to launch the mission arises this fall. By the end of October the distance between Vesta and Ceres - which are currently relatively close to one another - will begin increasing, mission managers said, adding that the two space rocks will near each other again in 15 years.
TRYING AGAIN
Dawn asteroid probe back
on the launch pad again
BY JUSTIN RAY
SPACEFLIGHT NOW
Posted: September 11, 2007
The long-awaited voyage of NASA's Dawn space probe to
rendezvous with a pair of small worlds in the asteroid belt has returned
to the launching pad for departure from Earth in two weeks' time.
"From here, the only way to go is up," said Keyur Patel, Dawn project manager at the Jet Propulsion Laboratory. "We are looking forward to putting some space between Dawn and Mother Earth and making some space history."
The eight-year, 3.2-billion-mile mission is scheduled for liftoff from Florida's east-central coast on Wednesday, September 26 at 7:25 a.m. EDT. The morning's available launch period will extend to 7:54 a.m.
After being grounded earlier this summer by an assortment of factors, Dawn was pulled off its United Launch Alliance Delta 2-Heavy rocket at Cape Canaveral's pad 17B two months ago. The spacecraft was placed in protective storage while engineers proceeded to launch the Mars-bound Phoenix lander atop another Delta rocket from neighboring pad 17A in early August.
Rocket-related delays, troubles arranging downrange tracking assets to monitor the launch and a rapidly closing launch window in July forced NASA officials to make the unusual decision of postponing the Dawn liftoff after the satellite was already on the pad. Senior agency managers opted to go with the Phoenix launch first, putting Dawn second in NASA's launch lineup.
See our
story from July that recounts the issues prompting the unusual
delay.
Now, the new launch opportunity for Dawn is about to open. In the wee hours Tuesday morning, Dawn was transported from the Astrotech processing complex near Titusville to the Delta pad. A caravan of vehicles made the 15-mile trip, arriving at the seaside pad at 5:10 a.m. The gantry crane then hoisted the payload into the pad tower for mating with the awaiting rocket. A NASA spokesman reported that Dawn was bolted to the launcher at 8:01 a.m. EDT.
The Delta 2-Heavy to launch Dawn is a three-stage rocket, with a kerosene-fueled first stage, nine strap-on solid boosters, a hydrazine second stage and solid-fuel third stage. The 12-story vehicle is the most powerful version of the venerable Delta 2 family, owing its extra thrust to slightly larger strap-on boosters.
The Heavy has flown three times, successfully lofting the Mars rover Opportunity, Spitzer Space Telescope and the MESSENGER orbiter now en route to Mercury.
Key testing and final preparations for the launch are planned over the next two weeks. The flight program verification, a readiness test between the Dawn spacecraft and the Delta rocket to simulate launch events, is scheduled for Thursday. Installation of the rocket's nose cone to shroud Dawn during ascent through the atmosphere is planned for next Wednesday, September 19.
Also next week, another Delta 2 rocket is targeted for liftoff from California's Vandenberg Air Force Base carrying a sophisticated commercial Earth-imaging satellite. Our coverage of that launch will be available here.
Dawn's launch window to begin its journey into the asteroid belt will feature daily liftoff opportunities between September 26 and October 15.
The probe will be dispatched on a trajectory to encounter Mars where it will use the Red Planet's gravity in a sling-shot maneuver for the trek into the asteroid belt for reconnaissance of the massive asteroid Vesta in 2011 and "dwarf planet" Ceres in 2015.
Scientists want up-close studies of Vesta and Ceres to learn more about the processes and conditions during the solar system's formation four-and-a-half-billion years ago. The spacecraft will orbit at increasingly lower altitudes above the two diverse objects during multi-month visits to determine the composition, internal structure and evolutionary history of the bodies.
"Dawn is also a journey back in time," says Chris Russell, the scientist leading the mission. "Ceres and Vesta have been altered much less than other bodies. The Earth is changing all the time; the Earth hides its history, but we believe that Ceres and Vesta, formed more than 4.6 billion years ago, have preserved their early record. They're revealing information that was frozen into their ancient surfaces."
Vesta is believed to be solid rock. The oval-shaped object has an average diameter of approximately 320 miles. But Ceres could harbor water or ice beneath its rocky crust. The "baby planet" has an average diameter of about 600 miles.
SUNDAY, SEPTEMBER 23, 2007
2030 GMT (4:30 p.m. EDT)
Stormy weather at Cape Canaveral prevented technicians from completing
work to load storable hypergolic propellants into the Delta 2 rocket at
launch pad 17B today, prompting a one-day postponement for this week's
liftoff of the Dawn asteroid orbiter.
Launch had been planned for Wednesday. But this slip in the pad schedule means the liftoff will be delayed to Thursday morning at 7:20 a.m. EDT