Like its long-lived cousin the Kepler space telescope, NASA’s Dawn spacecraft has finally used up all its fuel, ending a successful 11-year mission to explore the main belt asteroid Vesta and the dwarf planet Ceres in unprecedented detail.
Dawn was scheduled to check in with NASA’s Deep Space Network on 31 October, but no signal was detected. After flight controllers eliminated other possible reasons for the communications drop out they concluded the spacecraft had finally exhausted its supply of hydrazine fuel.
Without propellant, the spacecraft could no longer orient itself to aim its high-gain antenna back toward Earth or keep its solar panels pointed at the Sun. It remains in a stable orbit around Ceres, but for all intents and purposes, the spacecraft is dead.
“The fact that my car’s license plate frame proclaims ‘my other vehicle is in the main asteroid belt’ shows how much pride I take in Dawn,” said Mission Director and Chief Engineer Marc Rayman at NASA’s Jet Propulsion Laboratory. “The demands we put on Dawn were tremendous, but it met the challenge every time. It’s hard to say goodbye to this amazing spaceship, but it’s time.”
Carol Raymond, the Dawn mission’s principal investigator, said the spacecraft’s treasure trove of data “will be deeply mined by scientists working on how planets grow and differentiate, and when and where life could have formed in our solar system.”
“Ceres and Vesta are important to the study of distant planetary systems, too, as they provide a glimpse of the conditions that may exist around young stars,” she said.
Dawn was launchd on 27 September 2007 from the Cape Canaveral Air Force Station. Using low-power ion propulsion, the spacecraft made a gravity assist flyby of Mars in 2009 and slipped into orbit around Vesta in July 2011.
The spacecraft found that Vesta is the parent of a specific variety of meteorites found on Earth. While small enough to have been deeply scarred by the impact that launched the meteorites, it Vesta is large enough to feature a differentiated iron core with a silicate mantle and igneous crust. Dawn also detected carbon rich compounds on the surface that apparently were deposited by impacting bodies.
After more than a year of close-range observations, Dawn fired up its ion engine and headed for Ceres in September 2012, reaching its second target in March 2015. The spacecraft discovered the asteroid belt’s only dwarf planet was once an ocean world where salts and other deposits indicating a watery past are now exposed on the surface.
“Today, we celebrate the end of our Dawn mission, its incredible technical achievements, the vital science it gave us and the entire team who enabled the spacecraft to make these discoveries,” said Thomas Zurbuchen, NASA’s science administrator. “The astounding images and data that Dawn collected from Vesta and Ceres are critical to understanding the history and evolution of our solar system.”