NASA’s Dawn spacecraft became humanity’s first mission to orbit a dwarf planet when it was successfully captured by Ceres’ gravity this morning, Friday, March 6, at about 7:39 a.m. EST (4:39 a.m. PST).
Dawn was approximately 38,000 miles (61,000) kilometers distant at the moment it slipped into orbit around Ceres, an icy world which is a fossil remnant dating back to the formation of our Solar System and today features a duo of dauntingly mysterious bright spots smack dab in the middle of a crater that look like a pair of “eyes.”
Successful confirmation of the orbital capture was received by mission controllers at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., when a signal traveling at the speed of light arrived on Earth about an hour later, at 8:36 a.m. EST (5:36 a.m. PST).
The radio signal indicated that Dawn was healthy and that the ion propulsion system was thrusting as planned.
“Confirmed: I am in orbit around Ceres,” the probe tweeted soon thereafter!
Dawn’s primary mission is scheduled to last about 16 months until June 2016 involving snapping high resolution photos, mapping the elemental and mineralogical composition in fabulous detail.
It has taken a long time for Dawn to reach Ceres. The probe has been traveling through space for over seven years and nearly 5 billion kilometers since it was launched on its interplanetary journey on Sept. 27, 2007, on a Delta II Heavy rocket from Cape Canaveral Air Force Station in Florida.
“Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet,” said Marc Rayman, Dawn chief engineer and mission director at JPL.
“Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home.”
Ceres is a huge and mysterious alien world the size of Texas. It measures approximately 590 miles (950 kilometers) in diameter and is nearly round.
It is the largest and most massive object in the main Asteroid Belt, which lies between Mars and Jupiter.
But we know next to nothing about the diminutive world.
As Ceres rotates it reveals a pockmarked world, heavily cratered and featuring multiple bright “white spots” that have mystified and excited the scientists and public alike.
Are the ice volcanoes reflections from surface water ice or salts or something completely different? No one knows. And it’s Dawn’s duty to unravel the mystery.
“We feel exhilarated,” said Chris Russell, principal investigator of the Dawn mission at the University of California, Los Angeles (UCLA). “We have much to do over the next year and a half, but we are now on station with ample reserves, and a robust plan to obtain our science objectives.”
The solar-powered Dawn probe is making space history on several fronts now that it has finally arrived in orbit around Ceres for an up-close investigation.
Dawn is humanity’s first visitor to this utterly alien world, and is now humanity’s first spacecraft ever to visit and orbit two worlds in one mission—rather than just conduct multiple planetary flybys such as accomplished by NASA’s wildly successful twin Voyager probes launched back in the 1970s.
Following orbital capture it will gradually spiral in to an initial target science orbit of about 8,400 miles (13,500 kilometers) by mid-April.
The Dawn mission’s unprecedented feat of surveying two worlds is made possible by the revolutionary use of an exotic ion propulsion system, which is vastly more efficient than chemical propulsion thrusters.
Dawn previously made history when the probe achieved orbit around Vesta in July 2011 to become the first spacecraft from Earth to orbit a body in the main Asteroid Belt. The probe remained in orbit for an extended mission of 14 months, yielding reams of bonus science images and spectral data for the research teams until September 2012.
It has been thrusting using ion propulsion for much of the time since departing Vesta’s orbit over two years ago.
Vesta is the second most massive object in the Asteroid Belt. The odd-shaped world lacks a south pole and has an average diameter of 326 miles (525 kilometers).
In contrast to icy Ceres, Vesta is a rocky world. And Dawn’s science team aims to find out why they vary so greatly in composition, despite being rather close in celestial terms.
The best views of Ceres were captured by NASA’s iconic Hubble Space Telescope (HST) using the Advanced Camera for Surveys (ACS) instrument between December 2003 and January 2004—that is, until sharper views were obtained during Dawn’s final approach phase in late January.
The most recent images received from the spacecraft were taken on March 1 and show Ceres as a crescent, mostly in shadow, because the spacecraft’s trajectory put it on a side of Ceres that faces away from the Sun until mid-April. When Dawn emerges from Ceres’ dark side, it will deliver ever-sharper images as it spirals to lower orbits around the planet, says NASA.
Stay tuned here for continuing updates on Dawn’s orbital capture and science mission at protoplanet Ceres!
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