2:10 AM PST

Too early! But despite the small hours of the morning here I am very excited for the big launch of the Dawn spacecraft planned for this morning. NASA TV playing in Windows Media Player, the oven heating for some waffles, and a groggy yet excited brain…here we go!

2:18 AM PST

Launch is still planned for 7:20 AM PST (4:20 AM EST.)

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 2:24 AM PST

2:38 AM PST

The launch vehicle is a Delta II Heavy 2925H (modified Delta II) that will lift 1,217.7 kilograms (2,684.6 pounds) of spacecraft plus fuel. Right now technicians are adding liquid oxygen in preparation for launch. Launch will be from Cape Canaveral Air Force Station in Florida, USA.

Dawn will visit the two largest objects in the Asteroid Belt: asteroid Vesta and dwarf planet Ceres. This is not just a flyby mission; Dawn will actually approach and then go into orbit around each body, meaning that after it finishes with its exploration of Vesta, it will need to restart its ion propulsion engine to leave orbit and travel on to Ceres. Dawn should reach Vesta in September 2011 and Ceres in February 2015.

Other coverage:

• Dawn Mission Home Page
• Space.com
• The Planetary Society Weblog

2:54 AM PST

Image Caption: “Hubble Images of Asteroids Help Astronomers Prepare for Spacecraft Visit”
Credits for Vesta: NASA, ESA, and L. McFadden (University of Maryland)
Credits for Ceres: : NASA, ESA, and J. Parker (Southwest Research Institute)

Notice that Ceres is large enough to be roughly spherical in shape. Vesta is just slightly too small to be a sphere. The Hubble images are some of the best images taken of these bodies to date. The journey from discovery of a light in the sky followed by improving telescope images culminating in close up images by spacecraft is the reason why I find planetary science so fascinating. Just take a moment to appreciate what we do not know about Ceres and Vesta, and what we do know, captured in these blurry images. In just a few years, pending a successful launch, we will finally gain a much clearer perspective of these mysterious planetary bodies when their surfaces are revealed in great detail by Dawn.

3:09 AM PST

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 3:07 AM PST – venting oxygen vapor

3:22 AM PST

The operations teams heard during launch coverage sound like well-oiled machines, checking off items on their checklists with great confidence and professionalism. This indicates both the complexity of the logistics involved with any launch and the experience and abilities of highly skilled humans. A highlight of NASA TV coverage is when, at particular intervals in the activity leading up to launch, various teams report in that their subsystems are “Go!” This same sequence of “Go!” pronouncements just prior to launch was a highlight for those of us on the HiRISE team who attended the launch of Mars Reconnaissance Orbiter. Sometimes we try to do the same thing at work, to liven up the place, to various degrees of success.

3:32 AM PST

A built-in hold of 20 minutes is coming up soon, followed by the restart of countdown, a 10 minute hold, and then, potentially on schedule, launch!

3:35 AM PST

T minus 15 minutes and holding for twenty minutes…

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 3:35 AM PST – Logos through vapor

3:45 AM PST

The Dawn Mission website has a wealth of images, graphics, and video, including this graphic of the spacecraft:

Image Credit: Orbital Sciences Corporation – “Dawn Spacecraft“

3:55 AM PST

The countdown clock has restarted with 15 minutes and one last built-in hold expected prior to launch. Weather is reported to be good. And dawn is breaking behind Dawn!

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 3:53 AM PST – Dawn breaks behind Dawn

4:02 AM PST

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 3:59 AM PST – Engineering

4:05 AM PST

Next built-in hold of ten minutes has begun, at T minus 4 minutes.

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:05 AM PST – Dawn nears launch

4:14 AM PST

The hold has been extended, possibly because of a small aircraft or boat nearby.

4:16 AM PST

According to NASA TV, a ship has been spotted in the area. The Coast Guard has contacted the ship, to make sure it moves out of the way of falling solid rocket boosters. The ship should be out of the area in a few minutes.

4:20 AM PST

New launch time: 7:34 AM EST (4:34 AM PST.)

4:27 AM PST

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:24 AM PST

4:30 AM PST

T minus 4 minutes to launch!

4:31 AM PST

“Go!” for launch…everything seems to be ready…

4:34:00.372 AM PST

Launch!

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:34 AM PST – Launch!

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:34 AM PST – Launch

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:34 AM PST – Column rising

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:34 AM PST

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:34 AM PST

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:35 AM PST

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 4:35 AM PST – Solid motors jettison

4:38 AM PST

All seems to be well, with events happening as expected. Dawn is racing away up through the atmosphere and away from the Earth.

4:44 AM PST

Dawn has reached Earth orbit. It will coast there for 40 minutes before the second and third stage engines sends Dawn on its way to its first stop: Vesta.

5:10 AM PST

The second stage should reignite around 5:14 AM, followed by the third stage. Separation should occur 62 minutes after launch and then the solar arrays will begin deployment. Confirmation that everything is fine and Dawn is successfully on its way may not come until one hour and 34 minutes after launch, or later. Necessary Dawn autonomous actions mean that the spacecraft will be out of contact with the Earth for much of that time.

5:25 AM PST

Telemetry has been reacquired and all is well. Second stage restart has just occurred. Operations is following along with an animation of events created from telemetry.

5:33 AM PST

The second stage fired, shut down, and separated from the upper stages successfully.

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 5:26 AM PST – Second stage firing animation

Image Credit: NASA TV screen capture – Dawn Launch Coverage as of 5:29 AM PST – Second stage separation animation

5:37 AM PST

The third stage fired and separated successfully, and Dawn is on its way!

A spacecraft health check should occur in a few hours, followed by a press conference at 1:00 PM EST (10:00 AM PST.)

The launch period between September 26 and October 15, 2007 will allow Dawn to reach both Asteroid Vesta and recently reclassified dwarf planet Ceres as planned. Dawn has been repeatedly postponed due to a slew of other mission launches this summer and fall. These delays follow the cancellation and surprise reinstatement of the mission after earlier cost concerns were capped and technical issues were addressed.

The Dawn mission is unique because a single spacecraft will enter orbit around two separate bodies. Dawn will use an advanced ion propulsion system to enter orbit around Vesta in 2011 and then Ceres in 2014. Vesta and Ceres are the two largest objects in the Asteroid Belt and are expected to give planetary scientists a glimpse at the early history of the solar system. Scientists believe Vesta and Ceres have had very different histories despite similar beginnings.

NASA TV will broadcast the launch live.

More Information

• Dawn Mission Home Page