Launch Coverage

    Welcome to the Dawn Launch Blog
    Dawn lifted off from Cape Canaveral Air Force Station at 7:34 a.m. EDT on Sept. 27, 2007, aboard a Delta II-Heavy rocket. This is how the launch countdown unfolded.

    NASA's Launch Blog was activated: 5:15 a.m. EDT
    NASA's Launch Blog was deactivated: 8:45 a.m. EDT

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    Video highlights from the Dawn countdown are selected from televised coverage provided by NASA TV.
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    8:45 a.m. - The Dawn mission began with a brilliant early-morning liftoff from Cape Canaveral Air Force Station in Florida. The spacecraft was safely headed for the asteroid belt and a rendezvous with an asteroid and dwarf planet. Dawn, propelled by a constant thrust from three ion engines, is to get a gravity assist from Mars in February 2009 and then go into orbit around the asteroid Vesta in August 2011. After about nine months studying Vesta up close, Dawn is to fire its ion engines again and move to the dwarf planet Ceres. Studies will start there in February 2015. The mission is scheduled to close in July 2015. With the spacecraft safely sent to space, the coverage of the launch concludes now.

    8:36 a.m. - Dawn is on its way to the asteroid belt!

    8:31 a.m. - Third-stage burnout. The Dawn spacecraft is to separate from the third stage in about three minutes.

    8:30 a.m. - Third-stage ignition.

    8:28 a.m. - The second-stage engine has switched off as planned and a set of small rockets ignited to spin the Dawn spacecraft and its third stage for stability as the third stage fires.

    8:25 a.m. - The second stage has ignited again as planned to push Dawn out of Earth orbit. The engine will burn for about three minutes before it detaches and the third stage takes over.

    8:07 a.m. - The Dawn spacecraft has been coasting in a temporary orbit. It has another 19 minutes before the second-stage engine is to restart. The engine is to burn for about three minutes.

    7:40 a.m. - Official launch time is 7:34:00 a.m. EDT. The second stage continues to burn as planned. Everything is reported in good shape during Dawn's first climb into space.

    7:39 a.m. – The second stage completed its first firing and the Dawn spacecraft is in a temporary orbit more than 100 miles above the Earth. The second-stage engine will reignite to push Dawn out of Earth orbit. The third stage will complete that job and then Dawn will be on its own.

    7:38 a.m. – The nose cone fairing has separated in two pieces to reveal the Dawn spacecraft. The fairing protected the spacecraft from the intense heat and friction of launch.

    7:38 a.m. – The first-stage engine has shut off as planned and will separate momentarily. The second stage will take over for four minutes.

    7:37 a.m. – The last three solid-fueled boosters have burned out and jettisoned from the Delta II. The first stage main engine is powering the launch and is operating flawlessly.

    7:35 a.m. – Six of the solid-fueled boosters have burned out and fallen away from the Delta II rocket. The three remaining boosters ignited to help speed the Dawn spacecraft on its way.

    7:34 a.m. – The Delta II reached Mach 1 thirty seconds after launch.

    7:34 a.m. - LIFTOFF!

    7:33 a.m. - T- 1 minute and counting . . .

    7:32 a.m. – T- 2 minutes and counting . . .

    7:31 a.m. – Dawn is in the last stage of the countdown. Computers and sensors on the computer and spacecraft are signaling they are ready for launch.

    7:30 a.m. - T-4 minutes and counting . . . Controllers gave their "go" for launch and Dawn remains on schedule for a 7:20 a.m. liftoff.

    7:26 a.m. - The new launch time comes at the end of a collision avoidance window. That means Dawn would have come closer than allowed to an object already in orbit if it had launched between 7:27 a.m. and 7:33 a.m. Because the object is moving at orbital speed, it takes only a few minutes to move out of the way. Meanwhile, the ship that violated the exclusion area has also moved out of the way.

    7:24 a.m. - NEW LAUNCH TIME: 7:34 a.m.

    7:20 a.m. - A ship has entered the exclusion area offshore. The ship is in the area where the solid-fueled boosters would fall. The ship should be out of the area by 7:25 a.m. A new launch time has not been set.

    7:12 a.m. - The final "go" has been issued for launch at 7:20 a.m.

    7:06 a.m. - T-4 minutes and holding . . . The countdown has entered its last planned pause.

    7:00 a.m. - The sun is just coming up over Florida's east coast. Spotlights continue to showcase the Delta II rocket with the Dawn spacecraft tucked under its nose cone. 20 minutes until launch.

    6:55 a.m. - T-15 minutes and counting . . . The planned 20-minute hold has ended and the launch remains on schedule for a 7:20 a.m. liftoff. Another hold of 10 minutes is scheduled for T-4 minutes.

    6:46 a.m. - The Delta II has been a workhorse for NASA's exploration programs. It has dispatched spacecraft to study planets including Mars and Mercury and has sent probes to look at comets up close. The rocket has launched telescopes such as the Spitzer Space Telescope and has catapulted numerous satellites to study Earth from orbit.

    6:35 a.m. - T-15 minutes and holding. This is a planned pause in the countdown and will last 20 minutes. Everything still looks good for an on-time launch at 7:20 a.m. EDT.

    6:22 a.m. - At T-27 minutes and counting, the weather forecast continues to improve and the chance of acceptable weather at liftoff has increased to 80 percent.

    6:09 a.m. - The key to Dawn's success will be three ion engines that use very little fuel to steadily push the spacecraft toward the asteroid belt. The engines will thrust continuously for six years. In the vacuum of space, where there is no resistance, the constant thrusting will slowly build up Dawn's speed. Because the fuel needs are so small for the engines, Dawn did not have to be burdened with heavy fuel tanks. Mission designers say the flight could not be done with conventional thrusters because the fuel would be too heavy.

    6:00 a.m. - The countdown is proceeding smoothly toward a 7:20 a.m. launch. Weather forecasters said rainstorms are coming ashore south of the Cape Canaveral Air Force Station.

    5:56 a.m. - There are two planned holds in the countdown this morning. The first one will come at T-15 minutes and will pause the countdown for 20 minutes. That will begin at 6:35 a.m. The second hold is for 10 minutes and ends four minutes before launch. The holds give controllers a chance to make final evaluations before liftoff.

    5:45 a.m. - The Delta II that will launch Dawn toward the asteroid belt is the largest model available. It uses three stages and nine solid-fueled boosters. The boosters are also the largest available, and each has a four-foot-wide nozzle.

    5:35 a.m. - Supercold liquid oxygen is flowing into the first stage of the Delta II rocket at Launch Pad 17-B. The oxygen will mix with refined kerosene in the main engine during launch to provide thrust during the initial stage of launch. About 10,000 gallons of kerosene have already been loaded into the rocket.

    5:25 a.m. - The NASA launch team gave its go to load supercold liquid oxygen into the first stage.

    5:18 a.m. - The weather is improving, forecasters said during a just-concluded weather briefing. The current forecast remains 60-percent chance for good weather, but that is expected to increase as the countdown proceeds. The primary concern is scattered clouds.

    5:17 a.m. - The Dawn spacecraft is an unmanned probe that will use three ion engines to push past Earth, zip by Mars and orbit a large asteroid called Vesta, then change orbits and study a dwarf planet named Ceres.

    5:15 a.m. - Good morning from Cape Canaveral Air Force Station in Florida. We are counting down toward a 7:20 a.m. launch of the Dawn mission to the asteroid belt. A Delta II-Heavy rocket stands bathed in spotlights and pointed skyward at this hour and there are no technical issues causing concerns. The weather forecast offers a 60-percent chance of acceptable weather.

    Live Coverage Team
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