Douglas Isbell
Headquarters, Washington, DC                   July 28, 1999
(Phone:  202/358-1547)

John G. Watson
Jet Propulsion Laboratory, Pasadena, CA 
(Phone:  818/354-0474)

RELEASE:  99-84

CLOSEST-EVER ASTEROID FLYBY SET FOR JULY 29

     With its technology tests almost complete, NASA's Deep Space 
1 mission is about to undertake the closest encounter with an 
asteroid ever attempted when it flies within 10 miles (15 
kilometers) of the newly named asteroid Braille on July 29. 

     Deep Space 1 will rely on its experimental autonomous 
navigation system, called AutoNav, to guide the spacecraft past 
the mysterious space rock at 12:46 a.m. EDT at a relative speed of 
nearly 35,000 mph (56,000 kilometers per hour).

     "Deep Space 1's main purpose is to test advanced technologies 
for the benefit of future missions, so we view the flyby and its 
science return as a bonus," said Dr. Marc Rayman, Deep Space 1's 
chief mission engineer and deputy mission manager.  "This 
ambitious encounter is a high-risk endeavor and its success is by 
no means guaranteed.  But  should there be significant data 
return, the findings will be of great interest to the science 
community."

     Asteroid Braille was previously known as 1992 KD.  The new 
name was announced today by the Planetary Society, Pasadena, CA, 
as the result of a contest that focused on inventor themes and 
drew more than 500 entries from around the world.  The name honors 
Louis Braille (1809-1852), the blind French educator who developed 
the system of printing and writing named for him and used 
extensively by the blind.   

     The winning entry was submitted by Kerry Babcock of Port 
Orange, FL.  Eleanor Helin, who co-discovered the asteroid with 
fellow astronomer Kenneth Lawrence, made the final decision on the 
name.  Helin and Lawrence are astronomers at NASA's Jet Propulsion 
Laboratory (JPL), Pasadena, CA, which also manages Deep Space 1. 

     During the encounter, Deep Space 1 will be in the ecliptic 
plane (the plane in which Earth and most other planets orbit the 
Sun), moving more slowly than the asteroid, which will be 
progressing up through the ecliptic plane from below.  It may well 
be more appropriate to say that the asteroid will zoom by Deep 
Space 1 than the reverse.

     The flyby will allow final testing of AutoNav, which enables 
the spacecraft to use images of distant stars and asteroids within 
our Solar System to keep track of its location in space and to 
guide trajectory changes.  Deep Space 1 has successfully completed 
tests of its 11 other new technologies. 

     The asteroid and the space environment surrounding it make 
scientifically interesting targets for two advanced science 
instruments aboard Deep Space 1.  During the flyby, a spectrometer 
and imaging instrument will send back black-and-white photographs 
and images taken in infrared light, while a second instrument 
observes the three-dimensional distribution of ions and electrons, 
or plasma, in the area.

     In addition to their value for designing future missions, the 
images and other data returned from this encounter will greatly 
assist scientists in understanding the fundamental properties of 
asteroids.  Although scientists believe Braille's diameter is 
approximately 0.6 to 3 miles (1 to 5 kilometers), they know little 
else about it.  With this flyby, they can learn more about its 
shape, size, surface composition, mineralogy and terrain.

     Launched on Oct. 24, 1998, from Cape Canaveral Air Station, 
FL, Deep Space 1 marked the first launch of NASA's New Millennium 
Program, which tests and validates new technologies for future 
space and Earth-observing missions.  The technologies that have 
been tested on Deep Space 1 will help make future science 
spacecraft smaller, less expensive and capable of more independent 
decision-making so that they rely less on ground controllers.

     The mission has exceeded almost all of its technology 
validation requirements by conducting more extensive tests than 
had been planned.  As one dramatic example, the spacecraft's 
experimental xenon ion engine, which was required to thrust for a 
minimum of 200 hours, has been operated for nearly 1,800 hours.

     Deep Space 1 is budgeted at $152 million, including design, 
development, launch and operations.  The mission is managed for 
NASA's Office of Space Science by JPL, a division of the 
California Institute of Technology.