NASA to Launch Asteroid Mission


Lightning Prompts Launch Delay for NASA's Asteroid Probe
By Tariq Malik
Staff Writer
posted: 5 July 2007
1:13 p.m. ET

NASA's beleaguered Dawn asteroid probe will have to wait at least one more day to launch after lightning prevented workers from fueling the spacecraft's rocket Thursday.

Initially targeted for a Saturday afternoon liftoff, Dawn is now set to launch from Florida's Cape Canaveral Air Force Station on Sunday, July 8 at 4:04 p.m. EDT (2004 GMT). Current forecasts predict a 60 percent chance that poor weather will prevent the weekend space shot.

A lightning advisory prevented launch pad workers from fueling the second stage of Dawn's Delta 2 booster, NASA spokesperson D.C. Agle told from the agency's Kennedy Space Center spaceport in Cape Canaveral. The United Launch Alliance rocket's payload fairing was also too warm to begin loading the Delta 2 with the super-chilled oxidizer for its propellant, NASA officials said, adding that fueling operations should resume by Friday.

The delay is the latest in a series of difficulties for NASA while preparing Dawn for its $449 million mission to study the asteroids Vesta and Ceres.

In recent weeks, the mission managers have repaired last-minute damage to the spacecraft's solar arrays, weathered the late delivery of rocket parts that delayed Dawn's planned June 20 liftoff, and wrestled with a malfunctioning crane while assembling the probe's Delta 2 booster. Mission managers also needed more time to study the impact of higher than expected loads on parts of the Delta 2's solid rocket motors and substitute a launch tracking ship with an aircraft.

The Dawn spacecraft, too, has traveled a rocky road to the launch pad. NASA initially canceled the asteroid-bound mission in March 2006 due to cost overruns and technical challenges with the probe's xenon-powered ion engine. But the space agency reinstated the mission a few weeks later after an in-depth study into those hurdles.

Researchers hope the 2,684-pound (1,217-kilogram) Dawn spacecraft will answer questions on the formation of Vesta, which sports signs of lava flows on its surface, and potentially water ice-harboring Ceres. The probe is due to swing by Vesta in October 2011 and then rendezvous with Ceres in February 2015.

NASA's window to launch Dawn closes on July 11, when the space agency will shift over to prelaunch preparations for the Mars Phoenix lander and the shuttle Endeavour. Phoenix is slated to launch on Aug. 3 and be followed by Endeavour's STS-118 mission to the International Space Station on Aug. 7.

If Dawn misses its July launch window, it would be delayed until later this fall and cost an extra $25 million due to the need to replace the spacecraft's Delta 2 rocket's second stage, mission managers have said.


Wednesday, Jul. 11, 2007


(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

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.


Dawn asteroid probe back on the launch pad again

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.


Dawn was attached to the rocket a few hours after its pad arrival. Credit: NASA
  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.


An artist's concept of the Dawn mission. Credit: NASA
  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.

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

Launch Countdown Coverage for NASA's Dawn Mission
By Justin Ray

posted: 27 September 2007
Spaceflight Now Plus
Additional coverage for subscribers:


1515 GMT (11:15 a.m. EDT)

Photos from this morning's launch are posted here.

1325 GMT (9:25 a.m. EDT)

"With the launch of Dawn, ULA is continuing to show its dedication to providing safe, cost-effective, reliable access to space for U.S. government missions," said Mark Wilkins, vice president of Delta Programs at United Launch Alliance. "ULA has brought together the most talented professionals in the launch industry and we are honored to launch spacecraft, such as Dawn, supporting NASA's critical national mission to explore the universe."

1250 GMT (8:50 a.m. EDT)

"The Delta 2-Heavy has performed well. We're exactly where we want to be," NASA launch manager Omar Baez says. "The first stage, the second stage and the third stage were all nominal - nothing funny in the data so far. And from what see in the orbits we're right on the money."

This is the 76th consecutive successful Delta 2 rocket launch dating back to May 1997. The Delta 2's overall history since debuting in 1989 has achieved 129 successes in 131 flights.

Three more Delta 2 launches are planned this year beginning with a Global Positioning System satellite deployment mission for the Air Force on October 17 from Cape Canaveral. The launch of an Italian radar Earth-imaging craft for civilian and military uses is set for December 5 from Vandenberg Air Force Base, California. Another GPS satellite launch is targeted for December 20 from the Cape.

1240 GMT (8:40 a.m. EDT)

Spaceflight Now Plus subscribers can watch a movie of this morning's launch here.

To learn more about this service, click here.

1235 GMT (8:35 a.m. EDT)

T+plus 61 minutes, 58 seconds. SPACECRAFT SEPARATION! NASA's Dawn asteroid explorer has been released from the Delta 2 rocket's third stage, completing today's launch!

The probe will encounter Mars in 2009 to 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.

"Visiting both Vesta and Ceres enables a study in extraterrestrial contrasts," said Dawn principal investigator Christopher Russell of the University of California, Los Angeles. "One is rocky and is representative of the building blocks that constructed the planets of the inner solar system. The other may very well be icy and represents the outer planets. Yet, these two very diverse bodies reside in essentially the same neighborhood. It is one of the mysteries Dawn hopes to solve."

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.

1232 GMT (8:32 a.m. EDT)

T+plus 58 minutes. The rocket is flying northeastward across Australia. Release of the Dawn spacecraft is about four minutes away.

1231 GMT (8:31 a.m. EDT)

T+plus 57 minutes, 19 seconds. The Star 48B third stage has burned out of its solid fuel, ending the Delta 2 rocket's powered flight for the launch of dawn.

1230 GMT (8:30 a.m. EDT)

T+plus 56 minutes, 20 seconds. Good chamber pressure reported from the third stage.

1229 GMT (8:29 a.m. EDT)

T+plus 55 minutes, 58 seconds. Third stage ignition! The upper stage motor has been lit to propel Dawn out of Earth orbit.

1229 GMT (8:29 a.m. EDT)

T+plus 55 minutes, 30 seconds. Stage separation confirmed.

1228 GMT (8:28 a.m. EDT)

T+plus 54 minutes, 25 seconds. SECO 2. The second stage has completed its second burn of this launch. In the next minute, tiny thrusters on the side of the rocket will be fired to spin up the vehicle in preparation for release of the third stage.

1226 GMT (8:26 a.m. EDT)

T+plus 52 minutes, 30 seconds. Good chamber pressure reported from the second stage engine. Also, good flow rates of the fuel and oxidizer.

1225 GMT (8:25 a.m. EDT)

T+plus 51 minutes, 43 seconds. The second stage engine has ignited to resume the powered flight of this morning's Dawn launch.

1225 GMT (8:25 a.m. EDT)

T+plus 51 minutes, 34 seconds. Second stage hydraulics have been activated.

1225 GMT (8:25 a.m. EDT)

T+plus 51 minutes, 20 seconds. Dongara has picked up the rocket's signal as it flies over the Indian Ocean off the west coast of Australia.

1215 GMT (8:15 a.m. EDT)

T+plus 41 minutes. The next firing by the Delta rocket's second stage is coming up in 10 minutes. The Dongara tracking station in Australia should acquire the rocket about a minute before ignition. The site will relay the rocket's signal back to the Cape to provide confirmation of the second stage burn.

1209 GMT (8:09 a.m. EDT)

T+plus 35 minutes. As the rocket coasts in this parking orbit, it performs a "BBQ roll" maneuver to keep the thermal conditions on the vehicle equal. This maneuver was scheduled to start at about T+plus 15 minutes and conclude at T+plus 49 minutes.

1204 GMT (8:04 a.m. EDT)

T+plus 30 minutes. Delta is crossing Africa now. A map of the rocket's planned flight path is available here.

1154 GMT (7:54 a.m. EDT)

T+plus 20 minutes. The official liftoff time this morning was 7:34:00.372 a.m.

1146 GMT (7:46 a.m. EDT)

T+plus 12 minutes. The rocket has flown out of range from the Antigua tracking station. The next communications will come when Delta approaches the west coast of Australia.

1145 GMT (7:45 a.m. EDT)

T+plus 11 minutes. The rocket has successfully achieved a parking orbit with an apogee of 100.6 miles, perigee of 99.99 miles and inclination of 28.6 degrees. That is right on the pre-planned orbit parameters.

"Can't get better than that," says launch telemetry commentator Marc Lavigne.

1143 GMT (7:43 a.m. EDT)

T+plus 9 minutes, 4 seconds. SECO 1. The second stage engine cutoff has occurred, completing the motor's first firing of the day. The Delta 2 rocket and Dawn have arrived in a preliminary orbit around Earth following launch this morning from Cape Canaveral. The vehicle will coast for more than 40 minutes before the second stage is re-ignited.

1142 GMT (7:42 a.m. EDT)

T+plus 8 minutes. The second stage engine is consuming a hydrazine propellant mixture and nitrogen tetroxide oxidizer. This burn is needed to achieve a parking orbit around Earth.

1141 GMT (7:41 a.m. EDT)

T+plus 7 minutes, 40 seconds. Good chamber pressure reported on the second stage engine.

1141 GMT (7:41 a.m. EDT)

T+plus 7 minutes, 15 seconds. Delta is 97 miles in altitude, 908 miles downrange from the launch pad and traveling at 15,500 mph.

1140 GMT (7:40 a.m. EDT)

T+plus 6 minutes, 45 seconds. The Air Force's downrange tracking station on Antigua Island has acquired the rocket's signal.

1140 GMT (7:40 a.m. EDT)

T+plus 6 minutes. The vehicle continues to accelerate on the power provided by the second stage engine.

1139 GMT (7:39 a.m. EDT)

T+plus 5 minutes, 30 seconds. Delta is 80 miles in altitude, 538 miles downrange from the launch pad and traveling at nearly 14,500 mph.

1138 GMT (7:38 a.m. EDT)

T+plus 4 minutes, 48 seconds. The rocket's 9.5-foot diameter nose cone enclosing the spacecraft has been jettisoned.

1138 GMT (7:38 a.m. EDT)

T+plus 4 minutes, 40 seconds. The Delta's second stage engine has ignited following jettison of the spent first stage.

1138 GMT (7:38 a.m. EDT)

T+plus 4 minutes, 32 seconds. MECO. Main engine cutoff is confirmed. The first stage has completed its firing.

1138 GMT (7:38 a.m. EDT)

T+plus 4 minutes, 12 seconds. First stage systems continue to look good. The chamber pressures in the main engine and the twin vernier steering thrusters are normal.

1137 GMT (7:37 a.m. EDT)

T+plus 3 minutes, 40 seconds. Delta is 52 miles in altitude, 207 miles downrange from the launch pad and traveling at nearly 9,700 mph.

1136 GMT (7:36 a.m. EDT)

T+plus 2 minutes, 41 seconds. The three air-ignited solid rocket boosters have burned out and separated. The rocket is now flying solely on the power generated by the liquid-fueled first stage main engine.

1135 GMT (7:35 a.m. EDT)

T+plus 1 minute, 55 seconds. The air-lit boosters continue to burn along with the main engine. The vehicle is 19 miles in altitude, 44 miles downrange, traveling at 4,000 mph.

1135 GMT (7:35 a.m. EDT)

T+plus 1 minute, 23 seconds. All six ground-start solid rocket boosters have burned out of propellant and separated from the Delta 2's first stage. A moment before the jettison occurred, the three remaining motors strapped to rocket ignited to continue assisting the rocket's RS-27A main engine on the push to space.

1135 GMT (7:35 a.m. EDT)

T+plus 60 seconds. One minute into the flight.

1134 GMT (7:34 a.m. EDT)

T+plus 50 seconds. The rocket has flown through the area of maximum aerodynamic pressure in the lower atmosphere.

1134 GMT (7:34 a.m. EDT)

T+plus 35 seconds. Delta has broken the sound barrier. The first stage main engine and six strap-on solid motors are burning well.

1134 GMT (7:34 a.m. EDT)

T+plus 20 seconds. Dawn is rising aboard the 12-story Delta rocket on a spectacular sunrise ascent from Cape Canaveral.

1134 GMT (7:34 a.m. EDT)

LIFTOFF! Liftoff the Delta 2-Heavy rocket launching the Dawn spacecraft on a three-billion-mile trek to the uncharted worlds of Vesta and Ceres in the heart of the asteroid belt.

1133 GMT (7:33 a.m. EDT)

T-minus 30 seconds. SRB ignitors will be armed at T-minus 11 seconds.

The launch ignition sequence will begin in the final two seconds of the countdown when a ULA engineer pushes the engine start switch. The process begins with ignition of the two vernier engines and first stage main engine start. The six ground-lit solid rocket motors then light at T-0 for liftoff.

1133 GMT (7:33 a.m. EDT)

T-minus 1 minute. Sixty seconds from launch. The vehicle's second stage hydraulic pump has gone to internal power after its pressures were verified acceptable.

1132 GMT (7:32 a.m. EDT)

T-minus 75 seconds. The Air Force's Eastern Range has given the all-clear to launch.

1132 GMT (7:32 a.m. EDT)

T-minus 90 seconds. Topping of the liquid oxygen tank to the 100 percent level is underway.

1132 GMT (7:32 a.m. EDT)

T-minus 2 minutes. Pressurization of the first stage liquid oxygen is now beginning. Puffs of vapor from a relief valve on the rocket will be seen in the remainder of the countdown as the tank pressure stabilizes.

1131 GMT (7:31 a.m. EDT)

T-minus 2 minutes, 15 seconds. The Dawn spacecraft has been declared "go" for launch.

1131 GMT (7:31 a.m. EDT)

T-minus 3 minutes and counting. The rocket's third stage safe and arm devices are being armed. The third stage will boost Dawn out of Earth orbit for the voyage to the asteroid belt.

1130 GMT (7:30 a.m. EDT)

T-minus 3 minutes, 45 seconds. The Delta 2 rocket's systems are now transferring to internal power for launch.

1130 GMT (7:30 a.m. EDT)

T-minus 4 minutes and counting! Clocks are running again for the final minutes to liftoff of the United Launch Alliance Delta 2 rocket that will propel NASA's Dawn spacecraft on its eight-year mission. Launch will occur at 7:34 a.m. from pad 17B at Cape Canaveral Air Force Station in Florida.

1129 GMT (7:29 a.m. EDT)

One minute away from picking up the countdown.

1127 GMT (7:27 a.m. EDT)

The ship has cleared the hazard zone.

1125 GMT (7:25 a.m. EDT)

The countdown will come out of this hold at 7:30 a.m. for launch at 7:34 a.m.

1121 GMT (7:21 a.m. EDT)

NEW LAUNCH TIME. Liftoff has been reset for 7:34 a.m. EDT.

1118 GMT (7:18 a.m. EDT)

The Dawn spacecraft is going back to external power during this extra wait.

1117 GMT (7:17 a.m. EDT)

The constraint to launch is a ship in the restricted waters of the Atlantic where the solid rocket boosters fall. The Coast Guard is making contact with the vessel to get it cleared from the hazard zone.

1115 GMT (7:15 a.m. EDT)

HOLD EXTENDED. The countdown will not resume as planned. The Range has gone to a "no go" status.

1114 GMT (7:14 a.m. EDT)

Two minutes remain in the built-in hold.

1111 GMT (7:11 a.m. EDT)

All systems are reported "ready" by the launch team. There are no technical problems standing in the way of liftoff at 7:20 a.m. EDT.

1111 GMT (7:11 a.m. EDT)

The final pre-flight poll of the launch team is underway.

1110 GMT (7:10 a.m. EDT)

Now 10 minutes from launch.

1109 GMT (7:09 a.m. EDT)

NASA launch manager Omar Baez just polled his agency team and gave a "go" to proceed with the count.

1107 GMT (7:07 a.m. EDT)

The Dawn spacecraft atop the Delta 2 rocket is switching to internal power for launch.

1106 GMT (7:06 a.m. EDT)

T-minus 4 minutes and holding. The countdown has entered the final planned built-in hold. This is a scheduled 10-minute pause leading to today's liftoff at 7:20 a.m. for the Delta 2 rocket and Dawn spacecraft.

During the hold, officials will poll the various team members in the "soft blockhouse," Range Operations Control Center and Mission Directors Center.

1104 GMT (7:04 a.m. EDT)

The launch weather officer reports conditions are "go" for liftoff.

1101 GMT (7:01 a.m. EDT)

Now 19 minutes from liftoff. The first stage kerosene fuel tank is being pressurized.

1055 GMT (6:55 a.m. EDT)

T-minus 15 minutes and counting. The countdown has resumed following the planned hold. Clocks will tick down to T-minus 4 minutes where the final hold is scheduled. Liftoff of the Delta rocket from Cape Canaveral is slated to occur at 7:20 a.m. EDT this morning.

1051 GMT (6:51 a.m. EDT)

A launch team poll for a "ready" status to resume the countdown reported no constraints to continuing onward this morning.

1050 GMT (6:50 a.m. EDT)

Now 30 minutes to launch.

1045 GMT (6:45 a.m. EDT)

Now half-way through this built-in hold at T-minus 15 minutes. Once the countdown resumes, clocks will tick down to the T-minus 4 minute mark where a 10-minute hold is planned. Activitites are going smoothly for this morning's 7:20 a.m. liftoff of the Delta 2-Heavy rocket with the Dawn spacecraft.

Today's launch will be:

  • The 327th Delta rocket launch since 1960
  • The 131st Delta 2 rocket mission since 1989
  • The 5th of 2007

1035 GMT (6:35 a.m. EDT)

T-minus 15 minutes and holding. The countdown has entered a planned 20-minute built-in hold. The pause is designed to give the launch team a chance to work any problems or catch up on activities that might be running behind schedule. Engineers will also have time to examine all the data from the just-completed steering tests.

1030 GMT (6:30 a.m. EDT)

The first stage steering checks just finished, completing these slew tests for today's countdown.

1026 GMT (6:26 a.m. EDT)

Slews of the second stage engine are complete.

1025 GMT (6:25 a.m. EDT)

Technicians are starting the "slew" or steering checks of the first and second stage engines. These are gimbal tests of the nozzles on the first stage main engine and twin vernier engines and second stage engine to ensure the rocket will be able to steer itself during launch.

1022 GMT (6:22 a.m. EDT)

The official weather forecast has improved to an 80 percent chance of good conditions this morning. The revised outlook calls for just a few clouds at 3,000 feet, good visibility and northerly winds. The isolated rain showers in the area are staying to the southeast.

1020 GMT (6:20 a.m. EDT)

Sixty minutes from the start of the eight-year, three-billion-mile mission of the Dawn spacecraft.

1016 GMT (6:16 a.m. EDT)

Range Safety is performing inhibited checks of the command destruct receivers. The CRDs would be used in destroying the Delta rocket should the vehicle veer off course or malfunction during the launch.

1004 GMT (6:04 a.m. EDT)

Loading of the Delta 2 rocket's first stage liquid oxygen tank just concluded. The tank will be replenished through the countdown to replace the supercold liquid oxygen that naturally boils away.

The rocket now stands fully fueled for liftoff at 7:20 a.m. The vehicle's first stage was successfully loaded with RP-1 kerosene fuel along with the liquid oxygen over the past hour-and-a-half. The second stage was filled with its storable nitrogen tetroxide and Aerozine 50 fuels earlier this week. The nine strap-on booster rockets and third stage use solid propellants.

1002 GMT (6:02 a.m. EDT)

The first stage liquid oxygen tank just reached the 95 percent full level. The "rapid load" valve was closed, with the slower "fine load" phase continuing to fill the tank.

0950 GMT (5:50 a.m. EDT)

Now 90 minutes to launch. All systems are "go" for liftoff at 7:20 a.m. EDT this morning from Cape Canaveral.

0946 GMT (5:46 a.m. EDT)

Now 10 minutes into this approximate 25-minute process to fill the first stage liquid oxygen tank. The outer skin of the rocket is beginning to ice over as the supercold oxidizer pumps into the vehicle.

0936 GMT (5:36 a.m. EDT)

Cryogenic liquid oxygen, chilled to Minus-298 degrees F, has started flowing from the storage reservoir at Complex 17, through plumbing and into the bottom of the ULA Delta 2 rocket. The LOX will be consumed by the first stage main engine during the first four-and-a-half minutes of flight along with the 10,000 gallons of RP-1 kerosene already loaded aboard the vehicle.

0931 GMT (5:31 a.m. EDT)

The official "go" has been given by the launch director to start filling the rocket's first stage with liquid oxygen.

0930 GMT (5:30 a.m. EDT)

Preps for liquid oxygen loading are starting.

0924 GMT (5:24 a.m. EDT)

NASA launch manager Omar Baez just polled the agency's management team to verify there are no constraints with proceeding into liquid oxygen loading. No technical issues with rocket systems, the spacecraft or Range are being worked and weather is acceptable right now. There had been one Range issue under discussion but that has been resolved.

0919 GMT (5:19 a.m. EDT)

The launch weather officer says none of the weather rules are being violated right now. He says the odds of favorable weather this morning could be increased from the current 60 percent chance once the weather reconnaissance aircraft gets airborne to survey the clouds and showers around the Cape this morning.

0914 GMT (5:14 a.m. EDT)

The launch team has completed work to turn on and configure the Delta's onboard guidance computer.

0905 GMT (5:05 a.m. EDT)

The launch time weather forecast continues to predict scattered clouds at 3,000 and 10,000 feet, isolated rain showers in the area, northerly winds and a temperature around 77 degrees F. There is a 60 percent chance that weather will be acceptable for liftoff this morning. The cloud cover and showers are the concerns.

Should the launch be delayed to Friday for any reason, tomorrow's weather outlook calls for an 80 percent chance of good conditions.

0904 GMT (5:04 a.m. EDT)

The first stage fuel tank of the Delta 2 rocket has been fully loaded for today's launch. The tank was filled with a highly refined kerosene, called RP-1, during a 19-minute, 18-second process that concluded at 5:04:22 a.m. local time.

The next major task in the count will be loading super-cold cryogenic liquid oxygen into the first stage starting in about 30 minutes.

The kerosene and liquid oxygen will be consumed by the stage's Pratt & Whitney Rocketdyne RS-27A main engine and twin vernier steering thrusters during the initial four-and-a-half minutes of flight.

0901 GMT (5:01 a.m. EDT)

Rapid-loading of the RP-1 tank has concluded with 9,750 gallons already aboard the rocket. Fine load is continuing to finish filling the tank.

0857 GMT (4:57 a.m. EDT)

The launch team has computed that today's full load for the first stage fuel tank is 9,947 gallons.

Once the tank is filled to 98 percent or 9,750 gallons, the "rapid load" valve will be closed and the slower "fine load" phase will continue to top off the tank.

0853 GMT (4:53 a.m. EDT)

The first stage tank is half full, with 5,000 gallons aboard now.

0850 GMT (4:50 a.m. EDT)

Launch of the Delta rocket with the Dawn asteroid orbiter is two-and-a-half hours away.

0845 GMT (4:45 a.m. EDT)

Fueling just commenced. About 10,000 gallons of the kerosene propellant are pumping into the base of the rocket from storage tanks at pad 17B as fueling of the Delta 2's first stage begins for today's launch.

0840 GMT (4:40 a.m. EDT)

Preparations for loading the Delta 2 rocket's first stage RP-1 fuel tank are starting. After verifying valves, sensors, flow meters and equipment are ready, the highly refined kerosene fuel will start flowing into the vehicle a few minutes from now.

0825 GMT (4:25 a.m. EDT)

The launch team is starting pressurization steps for the first and second stage helium and nitrogen systems and second stage fuel tanks. And activation of the rocket's Redundant Inertial Flight Control Assembly guidance computer is beginning now.

0820 GMT (4:20 a.m. EDT)

BEGIN COUNT. The Terminal Countdown has been initiated for today's launch of the Dawn spacecraft aboard the Delta 2 rocket. No technical concerns have been reported by the launch team and activities are progressing on schedule. The odds of acceptable weather is 60 percent.

The next three hours will be spent fueling the rocket, activating systems and performing final testing before liftoff at 7:20 a.m. EDT from pad 17B at Cape Canaveral Air Force Station in Florida.

Workers have cleared the Complex 17 area in advance of the hazardous portion in today's launch operation. But a warning horn is now being sounded three times at the seaside complex as a precaution to alert any remaining personnel in the vicinity that they should leave immediately.

The pad clear status will allow the start of activities such as pressurizing the helium and nitrogen storage tanks inside the rocket's first and second stages, along with the second stage fuel and oxidizer tanks.

The countdown clocks currently stand at T-minus 150 minutes and counting. Two planned holds -- at the T-minus 15 minute and the T-minus 4 minute points -- will give the launch team some time to catch up on any work running behind. The first hold will last 20 minutes in duration, the second extends 10 minutes.

0811 GMT (4:11 a.m. EDT)

The launch team has been polled to ensure all stations are manned and systems are prepared to proceed with the countdown. Everyone reported "ready."

Liftoff of the Delta 2 rocket remains targeted to occur ontime at 7:20 a.m. local time.

0750 GMT (3:50 a.m. EDT)

Now 30 minutes through this scheduled hour-long hold in the countdown.

The Delta rocket today will be flying in its configuration known as the 7925-Heavy vehicle. The three-stage launcher is fitted with nine strap-on solid-propellant motors that are slightly larger than ones normally flown on Delta 2 rockets, giving the vehicle added power.

0720 GMT (3:20 a.m. EDT)

T-minus 150 minutes and holding. The countdown has just entered a planned 60-minute built-in hold at Cape Canaveral Air Force Station. The Terminal Countdown will begin once this hold is concluded.

0335 GMT (11:35 p.m. EDT Wed.)

Tower rollback to the launch position is being completed. Now, workers will turn their attention to configuring the pad and putting the final touches on equipment and the rocket before clearing Complex 17 overnight. The three-hour Terminal Countdown will begin at 4:20 a.m.

0246 GMT (10:46 p.m. EDT Wed.)

The pad 17B mobile service gantry has started slowly rolling away from the Delta 2-Heavy rocket.

0050 GMT (8:50 p.m. EDT Wed.)

Launch pad technicians are busy at work tonight preparing the mobile service tower for its rollback to reveal the Delta 2-Heavy rocket at Complex 17. The gantry is expected to be retracted before midnight.

The tower was used to stack the multi-stage vehicle atop the pad's launch mount, attach the nine strap-on solid motors and hoist the payload aboard the rocket. This cocoon-like structure wraps around the Delta to offer weather protection and full access for workers during the pre-launch campaign.

Liftoff remains on schedule for 7:20 a.m. EDT Thursday morning from Cape Canaveral's pad 17B.


NASA is poised to launch an innovative spacecraft Thursday that will use ultra-efficient ion engines to reach and orbit the two largest members of the asteroid belt between Mars and Jupiter. The unprecedented mission is, quite literally, a "blue light special" in the realm of interplanetary exploration.

Read our preview story.