[meteorite-list] Dawn Journal - September 30, 2007

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 2 Oct 2007 08:40:37 -0700 (PDT)
Message-ID: <200710021540.IAA18354_at_zagami.jpl.nasa.gov>

http://dawn.jpl.nasa.gov/mission/journal_9_30_07.asp

Dawn Journal
Dr. Marc Rayman
September 30, 2007

Dear Dawnitsways,

The Dawn project welcomes you to deep space! Dawn is operating smoothly
on the fourth day of its 8-year adventure. Like new parents, its
extremely proud and greatly sleep-deprived Earthbound mission operations
team is carefully monitoring its every move.

Launch had been targeted for September 26, but during its last few days
on Earth, Dawn continued to be subjected to the vagaries of the weather
on that dynamic planet. The second stage of the Delta II 7925H-9.5
rocket had been scheduled to have its second stage filled with
propellants on September 23. The nitrogen tetroxide was pumped in before
bad weather prevented further activities at Cape Canaveral's Space
Launch Complex 17B, so Dawn waited patiently and safely inside the
protective payload fairing, or nose cone, of the rocket. On September 24
a delicious blend of hydrazine and unsymmetrical dimethylhydrazine
(together known as Aerozine-50) was loaded as the countdown resumed,
targeted for launch on September 27 at the 7:20 am EDT opening of the
launch window.

This writer arrived at JPL at 11:30 pm PDT on September 26. The security
guards, although recognizing him (and his car), diligently verified his
identification in the chilly autumn evening and received the
enthusiastic greeting, "We're going to the asteroid belt tonight!" Upon
hearing, "All right!!" your loyal correspondent was ready to head into
mission control.

The countdown continued smoothly until shortly before launch when a ship
was discovered to have entered a restricted zone in the waters east of
the launch site. This required an unplanned hold.

The Delta rocket does not account for the changing position of the
launch pad in space as Earth rotates, so a launch delay would place the
spacecraft on a different trajectory. Most interplanetary missions have
launch windows of only 1 second because they have too little maneuvering
capability to compensate for the altered trajectory of the rocket.
Dawn's ion propulsion system gives it much greater flexibility, so its
launch window on September 27 was 29 minutes long. That proved to be
more than enough to allow the Coast Guard to invite the ship to depart
and then continue to ensure that no one would be at risk of being harmed
as the launch vehicle flew overhead.

The countdown resumed, no other glitches occurred, the rocket roared to
life, and Dawn's voyage began at 7:34:00.372 am EDT. It was propelled
off the launch pad not only by nearly 890,000 pounds of thrust (which
grew within 1 second to about 1,070,000 pounds) but also by the
enthusiasm of the people who designed and built it, those who will fly
it and will analyze the data it returns, and the vastly greater number
of people who share in the yearning to know the cosmos.

The rocket and all downrange tracking systems performed extremely well,
and Dawn's ride to space was very much what had been foretold in
prophecy. This was the 76th consecutive successful launch of a Delta II.
Following separation from the third stage at 8:36 am, Dawn went to work,
and the Deep Space Network at Goldstone, California began receiving its
radio transmissions at about 9:43 am.

Since then, the mission operations team at JPL has kept it company
constantly, albeit from an increasingly remote location. Even as the
cheers of hearing from the probe were echoing in mission control, the
team began a prompt assessment of Dawn's health. It was evident quickly
that it was in good condition, and operators were pleased to see that
the myriad problems they had trained to handle were now little more than
a fond recollection from simulations.

Upon conducting more detailed analyses of Dawn's telemetry, engineers
found that it handled itself quite admirably, operating completely on
its own, in space for the first time. As it was programmed to do, it
dealt with the few minor unexpected conditions it encountered with the
skill of a seasoned pro.

Over the subsequent days, the team gradually reconfigured the spacecraft
subsystems to prepare for the extensive testing and checkout scheduled
to conclude in mid December. By the time this report was filed, the team
had sent 148 sets of commands to Dawn and had scrutinized thousands of
measurements of temperatures, pressures, voltages, currents, data buffer
volumes, valve and switch positions, and many many other parameters. Now
the spacecraft is ready to be put through its paces before it begins its
ion propelled voyage past Mars and then on to the uncharted and distant
worlds Vesta and Ceres.

After years of planning, designing, building, and testing, the Dawn
mission is underway. While the fulfillment of its scientific objectives
remains well in the future, the craft finally is in space, and a far far
more exciting and challenging phase of the project is beginning.

Dawn is 1,158,000 kilometers (720,000 miles) from Earth or 3 times
farther than the moon. Radio signals, traveling at the universal limit
of the speed of light, take almost 8 seconds to make the round trip.
Received on Tue 02 Oct 2007 11:40:37 AM PDT