[FPSPACE] Dawn Journal for March 8. 2009

[LARRY KLAES]

Dawn Journal 
 
March 8, 2009
 
Dear Dawnlight Saving Times,
 
Now boosted into a new solar orbit courtesy of Mars, Dawn continues its interplanetary journey. The spacecraft is healthy and coasting, keeping its main antenna pointed to Earth, as it will for most of the next 3 months. After that, it will resume its familiar routine of devoting most of the time to gently thrusting with its ion propulsion system, with only a short period each week for communications.

Following the last log, as the probe succumbed to the gravitational pull of the red planet, its trajectory gradually began to change. Flying true to the plan, Dawn swooped close to Mars and then left it behind on a new course, having taken advantage of Mars’s gravity.

The spacecraft plunged to within 542 kilometers (337 miles) of the planet, reaching that lowest altitude at 4:27:58 pm PST on February 17. The last time it had been so close to another solar system body was on September 27, 2007, as it left Earth to begin its long journey to the asteroid belt. In the intervening time, it traveled alone (although always accompanied by the good wishes of space enthusiasts on its home planet and throughout the cosmos) for 1.06 billion kilometers (661 million miles). 
 
The targeting of the encounter was well within acceptable limits. Before embarking on the mission, long before launch, engineers chose 500 kilometers (311 miles) as a convenient initial target altitude for planning purposes. With the extraordinary capability of the ion propulsion system, Dawn easily could accommodate significant deviations from the plan. To accomplish its mission, the probe needed to fly anywhere through a window shaped liked a croquet wicket, extending from more than 750 kilometers (466 miles) above the planet down to 300 kilometers (186 miles). (The lower limit was chosen for safety, maintaining a comfortable distance from the tenuous atmosphere and other threats the spacecraft was not designed to handle.) The width at the bottom of the wicket was almost 670 kilometers (415 miles).

 

Full article here:

 

http://dawn.jpl.nasa.gov/mission/journal_3_08_09.asp

 

 
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