NASA's Dawn Spacecraft Fires Past Record for Speed Change

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DC Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown@nasa.gov

NEWS RELEASE: 2010-192 June 7, 2010

NASA'S DAWN SPACECRAFT FIRES PAST RECORD FOR SPEED CHANGE

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-192&cid=release_2010-192

PASADENA, Calif. – Deep in the heart of the asteroid belt, on its way to the first of the belt's two
most massive inhabitants, NASA's ion-propelled Dawn spacecraft has eclipsed the record for velocity
change produced by a spacecraft's engines.

The previous standard-bearer for velocity change, NASA's Deep Space 1, also impelled by ion
propulsion, was the first interplanetary spacecraft to use this technology. The Deep Space 1 record fell
on Saturday, June 5, when the Dawn spacecraft's accumulated acceleration over the mission exceeded
4.3 kilometers per second (9,600 miles per hour).

"We are using this amazing ion-engine technology as a stepping-stone to orbit and explore two of the
asteroid belt's most mysterious objects, Vesta and Ceres," said Robert Mase, Dawn project manager
from NASA's Jet Propulsion Laboratory in Pasadena, Calif.

A spacecraft's change in velocity refers to its ability to change its path through space by using its own
rocket engines. This measurement of change begins only after the spacecraft exits the last stage of the
launch vehicle that hurled it into space.

To get to where it is in both the record books and the asteroid belt, the Dawn spacecraft had to fire its
three engines – one at a time-- for a cumulative total of 620 days. In that time, it has used less than
165 kilograms (363 pounds) of xenon propellant. Over the course of its eight-plus-year mission,
Dawn's three ion engines are expected to accumulate 2,000 days of operation -- 5.5 years of thrusting
-- for a total change in velocity of more than 38,620 kilometers per hour (24,000 miles per hour).

"I am delighted that it will be Dawn that surpasses DS1's record," said Marc Rayman, chief engineer
for the Dawn mission and a previous project manager for Deep Space 1."It is a tribute to all those
involved in the design and operations of this remarkable spacecraft."

At first glance, Dawn's pedal-to-the-metal performance is a not-so-inspiring 0-to-97 kilometers per
hour (0-to-60 miles per hour) in four days. But due to its incredible efficiency, it expends only 37
ounces of xenon propellant during that time. Then take into consideration that after those four days
of full-throttle thrusting, it will do another four days, and then another four. By the end of 12 days,
the spacecraft will have increased its velocity by more than 290 kilometers per hour (180 miles per
hour), with more days and weeks and months of continuous thrusting to come. In one year's time,
Dawn's ion propulsion system can increase the spacecraft's speed by 8,850 kilometers per hour (5,500
miles per hour), while consuming the equivalent of only 16 gallons of fuel.

"This is a special moment for the spacecraft team," said Dawn's principal investigator, Chris Russell of
the University of California Los Angeles. "In only 407 days, our minds will be on another set of
records, the data records that Dawn will transmit when we enter Vesta orbit."

Dawn's 4.8-billion-kilometer (3-billion-mile) odyssey includes exploration of asteroid Vesta in 2011
and 2012, and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness
to much of our solar system's history. By using the same set of instruments at two separate
destinations, scientists can more accurately formulate comparisons and contrasts. Dawn's science
instrument suite will measure shape, surface topography and tectonic history, elemental and mineral
composition, as well as seek out water-bearing minerals. In addition, the way the Dawn spacecraft
orbits both Vesta and Ceres will be used to measure the celestial bodies' masses and gravity fields.

While Dawn surpassed Deep Space 1's record for velocity change, Deep Space 1 will continue to
reign as holder for the longest duration of powered spaceflight for another few months. Dawn is
expected to take over that record on about August 10 of this year.

The Dawn mission to Vesta and Ceres is managed by JPL, a division of the California Institute of
Technology in Pasadena, for NASA's Science Mission Directorate, Washington. The University of
California, Los Angeles, is responsible for overall Dawn mission science. Other scientific partners
include Planetary Science Institute, Tucson, Ariz.; Max Planck Institute for Solar System Research,
Katlenburg-Lindau, Germany; DLR Institute for Planetary Research, Berlin, Germany; Italian
National Institute for Astrophysics, Rome; and the Italian Space Agency, Rome. Orbital Sciences
Corporation of Dulles, Va., designed and built the Dawn spacecraft.

To learn more about Dawn and its mission to the asteroid belt, visit: http://www.nasa.gov/dawn

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