This week was a disappointing one for NASA and fans of space exploration, as the space agency announced that two pioneering projects, the Kepler Space Telescope, and the Dawn spacecraft asteroid explorer, have run out of fuel and both will be left to drift in space.
The announcements, which were made two days apart, mark the end of two missions which have massively influenced our understanding of our universe and will shape space-exploration for decades to come.
Farewell to the Kepler Space Telescope
The Kepler space telescope reached the end of its nine-year-mission to search for Earth-like worlds despite originally only being expected to run for four years. The telescope has made an impressive contribution to our knowledge of exoplanets outside the solar-system, responsible for the discovery of an impressive 2,662 of the 3,800 exoplanets discovered thus far.
The Kepler operating team will beam a signal to the telescope that begins a built-in programme that will shut –down the telescope’s operating systems including its radio transmitter and on-board fault-protection system.
The receipt of this signal will essentially leave Kepler a floating chunk of inert scrap metal.
“Kepler is currently trailing the Earth by about 94 million miles and will remain the same distance from the Earth for the foreseeable future,” Charlie Sobeck, project system engineer at NASA’s Ames Research Center in Moffett Field, California, said during a teleconference with reporters.
Kepler, launched on March 7th, 2009, currently occupies a heliocentric orbit trailing Earth surveying the Milky Way searching for Earth-like exo-planets in habitable zones. The telescope has a fixed-field of view in which it monitors the brightness of approximately 150,000 main-sequence stars. Referred to as the transit method, a dimming of the brightness of these stars imply the passing of an exoplanet around its host star.
One of Kepler’s most astounding achievements was the observation of Earth from its vantage point 94-million-miles away as seen in the image above.
NASA has ruled out a potential rescue or refueling mission similar to those performed several times on the Hubble space telescope, achievable due to its low-Earth-orbit. Earth will approach the telescope in 2060 due to out faster orbit, but it is expected that the planet’s gravity will push Kepler closer to the Sun keeping it out of reach.
Kepler has had close-shaves before and managed to survive. In 2013 the telescope lost one of its four stabilizing reaction-wheels but team-members were able to use the remaining three-wheels and radiation pressure from the Sun to achieve restabilization. The revitalization of Kepler was referred to as the K2 mission beginning in 2014 and enabled the discovery of a further 354 exoplanets.
Even though Kepler’s mission is over, discoveries from its operation remain, over 2,900 exoplanet ‘candidates’ remain to confirmed by follow-up analysis and observation.
Unfortunately, Kepler was not the only NASA mission that bit the space-dust this week.
The Break of Dawn
NASA’s Dawn spacecraft, which orbited Vesta and Ceres, two of the largest objects in the Asteroid belt, has also run out of fuel. NASA made the announcement on November 1st making this a bad week for space-exploration.
“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,” Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate said in a statement.
Dawn launched in 2007 designated to study protoplanet Vesta and dwarf planet Ceres, believed to be remnants from the solar system’s formation, hence the name ‘Dawn’.
Dawn held its orbit around Vesta for fourteen months beginning in July 2011, discovering that water once ran across its surface and picturing its highest peak located at its south pole.
Following this, in September 2012, Dawn made its way to Ceres, arriving in March 2015, where it became the first spacecraft to orbit a dwarf planet as well as the first to orbit a two-body system other than the moon and Earth.
Once at Ceres, Dawn discovered bright-spots under the planet’s surface, which its operating team believed to be salts left behind when a briny sub-surface body of water burned away due to exposure. Ceres has also detected organic molecules on Ceres’ surface. These elements make Ceres a tempting target for astrobiologists.
Dawn’s operators discovered it had run out of its Hydrazine fuel on October 31st meaning that the spacecraft can no-longer reorientate itself, preventing it from recharging using solar-energy and from sending data back to Earth, when it failed to check-in.
Sad though these ‘deaths’ are, NASA had expected both. The contributions both Kepler space telescope and the Dawn spacecraft have made to science, space-exploration and astrobiology will live on much longer than the technology itself.