Thaindian News

Washington, May 4 (ANI): NASA spacecraft Dawn has reached a new phase of its mission to the asteroid Vesta, and will begin using cameras for the first time to aid navigation for an expected July 16 orbital encounter.

At the start of this three-month final approach to this massive body in the asteroid belt, Dawn is 752,000 miles (1.21 million km) from Vesta, or about three times the distance between the Earth and the Moon.

During the approach phase, the spacecraft’s main activity will be thrusting with a special, hyper-efficient ion engine that uses electricity to ionize and accelerate xenon to generate thrust.

The 12-inch-wide ion thrusters provide less thrust than conventional engines, but will provide propulsion for years during the mission and provide far greater capability to change velocity.

“We feel a little like Columbus approaching the shores of the New

World,” said Christopher Russell, Dawn principal investigator, based

at the University of California in Los Angeles (UCLA).

“The Dawn team can’t wait to start mapping this Terra Incognita,” he added.

By analyzing where Vesta appears relative to stars, navigators will pin down its location and enable engineers to refine the spacecraft’s trajectory.

Using its ion engine to match Vesta’s orbit around the sun, the spacecraft will spiral gently into orbit around the asteroid. When Dawn gets approximately 9,900 miles (16,000 kilometers) from Vesta, the asteroid’s gravity will capture the spacecraft in orbit.

“After more than three and a half years of interplanetary travel, we are finally closing in on our first destination,” said Marc Rayman, Dawn’s chief engineer, at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

“We’re not there yet, but Dawn will soon bring into focus an entire world that has been, for most of the two centuries scientists have been studying it, little more than a pinpoint of light,” he said.

Scientists will search the framing camera images for possible moons around Vesta. None of the images from ground-based and Earth-orbiting telescopes have seen any moons, but Dawn will give scientists much more detailed images to determine whether small objects have gone undiscovered.

The gamma ray and neutron detector instrument also will gather information on cosmic rays during the approach phase, providing a baseline for comparison when Dawn is much closer to Vesta.

Simultaneously, Dawn’s visible and infrared mapping spectrometer will take early measurements to ensure it is calibrated and ready when the spacecraft enters orbit around Vesta. (ANI)