[FPSPACE] Dawn's one year anniversary in space

[LARRY KLAES]

Just one month late.

>From the Dawn Journal by Chief Engineer Dr. Marc Rayman:

September 27, 2008

Dear Dawnniversaries,

On the first anniversary of its departure from Earth, Dawn continues with 
what it has been doing for most of its time in space: with the greatest 
patience it is gently reshaping its orbit around the Sun with its ion 
propulsion system.

In its first year of travels, the spacecraft has thrust for a total of about 
253 days, or 69% of the time. Dawn has been in powered flight for 85% of the 
time since the beginning of its interplanetary cruise phase in December 2007 
and about 0.000000005% of the time since the Big Bang. While for most 
spacecraft, firing a thruster to change course is a special event, it is 
Dawn's wont. All this thrusting has cost the craft only 67 kilograms (148 
pounds) of its supply of xenon propellant, which was 425 kilograms (937 
pounds) 1 year ago.

The thrusting so far in the mission has achieved the equivalent of 
accelerating the probe by 1.68 kilometers per second (3760 miles per hour). 
As the preceding log described, because of the principles of motion for 
orbital flight, whether around the Sun or any other gravitating body, Dawn 
is not actually traveling this much faster than when it launched. But the 
effective change in speed remains a useful measure of the effect of any 
spacecraft's propulsive work. Having accomplished only one-eighth of the 
thrust time planned for its entire mission, Dawn has already exceeded the 
velocity change required by many spacecraft. (For a comparison with probes 
that enter orbit around Mars, visit the red planet yourself or refer to a 
previous log.)

Full article here:

http://dawn.jpl.nasa.gov/mission/journal_9_27_08.asp