Ground controllers commanded Deep Space 1 to turn off thrusting of its ion engine this week, allowing them to perform critical tests of two of the mission's advanced technologies.

The ion engine was turned off Tuesday, December 8, after a

marathon period of two weeks of thrusting. While operating, the

ion engine ran more than twice as long as it was originally

planned to thrust without interruption at any time during the

mission. By running the ion engine for more than 200 hours and

successfully conducting technology validation of the spacecraft's

solar array and transponder (radio transmitter/receiver), the

team achieved the minimum criteria that NASA established for

overall mission success.

With the ion engine off, the team was able to activate one

of the mission's two advanced science instruments, the Plasma

Experiment for Planetary Exploration (PEPE). This involved a

complex series of activities Tuesday and Wednesday. The advanced

instrument, which has no moving parts, is now fully powered up

and will be left on indefinitely.

The team was also able to test another of the mission's

advanced technologies, the Ka-band solid-state power amplifier.

On Tuesday and Wednesday nights, Deep Space 1 sent data to Earth

in the Ka band at a frequency four times higher than that used

for most communications with solar system exploration spacecraft

today, transmitting to a ground station of the Deep Space Network

at Goldstone, California. Deep Space 1 also sent data in the

lower-frequency X band using its high-gain antenna for the first

time. During the tests, the spacecraft's transponder sent

telemetry at 14 different data rates.

On Friday, the team will command Deep Space 1 to resume ion

engine thrusting. Plans call for the ion engine to operate

nearly continuously until January. The spacecraft will suspend

thrusting from January to March in order to conduct other

technology validation activities and to help shape its flight

path for its flyby of asteroid 1992 KD in July 1999.

Deep Space 1 is now 7.6 million kilometers (4.7 million

miles) from Earth, or more than 19 times as far away from Earth

as the Moon is. Radio signals traveling at the speed of light

take about 50 seconds to make the round trip.