DAWN, STUDYING THE PROTOPLANETS VESTA & CERES

Today, The Grandma has received the wonderful visit of Joseph de Ca'th Lon, one of her best friends. 

 

Joseph loves Astronomy and they have been talking about Dawn, the spacecraft that was launched by NASA on a day like today in 2007.

Dawn is a retired space probe that was launched by NASA in September 2007 with the mission of studying two of the three known protoplanets of the asteroid belt: Vesta and Ceres. 

In the fulfillment of that mission -the ninth in NASA's Discovery Program- Dawn entered orbit around Vesta on July 16, 2011, and completed a 14-month survey mission before leaving for Ceres in late 2012. It entered orbit around Ceres on March 6, 2015. 

In 2017, NASA announced that the planned nine-year mission would be extended until the probe's hydrazine fuel supply was depleted.

On November 1, 2018, NASA announced that Dawn had depleted its hydrazine, and the mission was ended. The spacecraft is currently in a derelict, but stable, orbit around Ceres.

Dawn is the first spacecraft to orbit two extraterrestrial bodies, the first spacecraft to visit either Vesta or Ceres, and the first to orbit a dwarf planet.

The Dawn mission was managed by NASA's Jet Propulsion Laboratory, with spacecraft components contributed by European partners from Italy, Germany, France, and the Netherlands.

More information: NASA

It was the first NASA exploratory mission to use ion propulsion, which enabled it to enter and leave the orbit of two celestial bodies. Previous multi-target missions using rockets powered by chemical engine, such as the Voyager program, were restricted to flybys.

The first working ion thruster in the US was built by Harold R. Kaufman in 1959 at NASA's Glenn Research Center in Ohio. The thruster was similar to the general design of a gridded electrostatic ion thruster with mercury as its propellant. Suborbital tests of the engine followed during the 1960s, and in 1964 the engine was tested on a suborbital flight aboard the Space Electric Rocket Test 1 (SERT 1). It successfully operated for the planned 31 minutes before falling back to Earth. This test was followed by an orbital test, SERT-2, in 1970.

Deep Space 1 (DS1), which NASA launched in 1998, demonstrated the long-duration use of a xenon-propelled ion thruster on a science mission, and validated a number of technologies, including the NSTAR electrostatic ion thruster, as well as performing a flyby of an asteroid and a comet. In addition to the ion thruster, among the other technologies validated by the DS1 was the Small Deep Space Transponder, which is used on Dawn for long-range communication.

The Dawn mission was designed to study two large bodies in the asteroid belt in order to answer questions about the formation of the Solar System, as well as to test the performance of its ion thrusters in deep space. 

Ceres and Vesta were chosen as two contrasting protoplanets, the first one apparently "wet" and the other "dry", whose accretion was terminated by the formation of Jupiter. The two bodies provide a bridge in scientific understanding between the formation of rocky planets and the icy bodies of the Solar System, and under what conditions a rocky planet can hold water.

More information: NASA-Jet Propulsion Laboratory

The Dawn mission's goal was to characterize the conditions and processes of the Solar System's earliest eon by investigating in detail two of the largest protoplanets remaining intact since their formation.

Although the mission has finished, the data analyses and interpretations will continue for many years. The primary question that the mission addresses is the role of size and water in determining the evolution of the planets.

Ceres and Vesta are highly suitable bodies with which to address this question, as they are two of the most massive of the protoplanets. Ceres is geologically very primitive and icy, while Vesta is evolved and rocky. Their contrasting characteristics are thought to have resulted from them forming in two different regions of the early Solar System.

There are three principal scientific drivers for the mission. First, the Dawn mission can capture the earliest moments in the origin of the Solar System, granting an insight into the conditions under which these objects formed. Second, Dawn determines the nature of the building blocks from which the terrestrial planets formed, improving scientific understanding of this formation. 

Finally, it contrasts the formation and evolution of two small planets that followed very different evolutionary paths, allowing scientists to determine what factors control that evolution.

More information: NASA

 NASA wanted to assure its ability to examine
the spacecraft in orbit for signs of damage.

Marc Garneau