A space mission that has been nearly 20 years in the making is about to reach its destination 143 million miles from Earth.

"It's been a long trip," said Christopher T. Russell, a UCLA professor of geophysics and space physics, who has been in charge of the mission since its inception in 1992. "Finally, the moment of truth is about to arrive."

The Dawn spacecraft, a small satellite loaded with cameras and multiple types of spectrometers launched in 1997, will arrive at Vesta, a small protoplanet in the asteroid belt that separates Mars and Jupiter, in July.

Scientists hope the data that Dawn gathers will provide more information about the early formation of the solar system.

Once Dawn reaches Vesta, it will begin the process of entering into Vesta’s orbit. By September, Dawn will orbit Vesta some 400 miles from its surface, scanning the planet and snapping pictures.

In November, Dawn will move in closer, about 125 miles from Vesta’s surface. Russell expects to begin receiving photos and data in January 2012.

According to Russell, Vesta is similar to many of the planets around, and including, Earth in terms of its features and structures, but lacks the gravity necessary to maintain atmosphere.

Russell expects to find a surface pummeled with craters, similar to the moon’s.

"We know there is an enormous crater at the south pole that we can see with the Hubble Space Telescope. That crater, some 280 miles across, has released material into the asteroid belt."

Meteorites from Vesta have fallen into Earth’s atmosphere, allowing Russell to learn much about the planet before Dawn even arrived. These meteorites indicate that Vesta formed from galactic dust during the solar system's first 3 million to 10 million years.

"We're going back in time to the early solar system," Russell said.

After Dawn finishes orbiting Vesta for a year, it will travel for three years to a dwarf planet named Ceres and perform the same type of data gathering as it did with Vesta.

The Dawn mission is managed by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, Calif., for NASA's Science Mission Directorate. Team members include scientists from JPL, the NASA Goddard Space Flight Center, the Planetary Science Institute, the Massachusetts Institute of Technology and other institutions.