Dawn brings enlightenment to Ceres

Deep in the asteroid belt an object 590 miles in diameter flies in orbit of the sun.

This “minor planet” — as the term goes — is Ceres, the largest object in the asteroid belt. It lies in between the orbits of Mars and the gas giant Jupiter and it is so big that its own gravity has rounded it much like our own moon.

It is a mix of rock and ice that has been around since formation of the solar system, which we all in habit, alone in the darkness of deep space.

Enter now the Dawn in a blaze of ion blue. No, not the dawn of the sunrise, the Dawn of the space probe of that name. Its final approach for orbital insertion is this Friday, March 6th.

Already pictures beamed back from Dawn’s cameras have been providing some mystery in the form of two bright spots in a single crater on the surface of Ceres. Just what are they along with fainter spots elsewhere on this tiny world is one of a million questions scientists are asking and hoping to find answers to.

Ceres was discovered in 1801 by Giuseppe Piazzi of Palermo, Italy. But it was only in the late 20th century with the advent of the Hubble space telescope that Ceres really became interesting. The Hubble took some of the first pictures of it. And now, with Dawn coming onto the scene, that has been stepped up a bunch of notches on the interesting scale to +10 and a half. With its high-resolution cameras, Dawn will shed light on the moon, to pardon the pun.

Dawn is no rookie in space exploration. Since it’s launch in 2007 the Dawn spacecraft has flown to the asteroid belt with aid of a brand new technology in powered space flight: three Ion drive engines that power Dawn with a blaze of blue across the void like something from a science fiction movie. Far from fiction, it is a real fact in space travel.

Ion propulsion is fairly new and only another has used it to fly in space before Dawn. That was Deep Space 1, the world’s first ion-powered spacecraft.

But what is Ion propulsion? In Dawn’s case, an electrical charge from its solar power array accelerates ions from its xenon gas fuel supply to 7-10 times that of chemical rocket engines. It can be throttled up or down in thrust in each engine. Two are used to maintain flight. The third is a spare.

Unlike chemical rockets, which peter out of fuel after a few minutes of un-adjustable thrust, Dawn flies onward for days, weeks, months and indeed years in powered flight. And it gets great gas mileage, too. About 3.25 milligrams of xenon per second or about 10 ounces every 24 hours at full thrust. (Dawn has 937 pounds of compressed Xenon in her tanks.)

Now if Dawn was on one our earthly highways it would take it four days at maximum thrust to go from 0 to 60 mph. But in space that is another story.

Dawn was boosted to space by a Delta II rocket from the surface of Earth to speeds of thousands of miles per hour. Ion powered flight is the way to go into the depths of space taking that boost to new highs in fully controlled, powered flight. This is something not even Voyagers 1& 2 can boast of. They were really interplanetary gliders armed with small thrusters for course changes only. They completely depended on the rules of Newtonian physics and gravity assists from the planets they passed by.

Dawn is a veteran of space. She already has entered the orbit of another giant asteroid Vesta in July of 2011. Dawn hung out with the huge rock until September of 2012, taking all sort of measurements and images that thrilled many down here on earth including this writer.

Now, three years later, Dawn is fixing to thrill yet again the scientific community as well as millions of everyday earth people as it enters the final approach to orbit around Ceres. The engines will power down, instruments will warm up and the cameras will focus on a new world for us to explore via its eyes in the dark, bringing the light of knowledge to the human race as to the origins of our solar system. And maybe Dawn will shedd light on just what those two bright spots on Ceres really are. Dawn is aptly named for its mission of space exploration.

To see what is going on with Dawn, visit dawn.jpl.nasa.gov.

Wasilla resident Daniel D. Grota retired from the U.S. Army after more than 21 years of service.