Deep impact extended mission heads for Comet Hartley Two

December 15th, 2007 - 2:18 pm ICT by admin  

College Park (Maryland, USA), Dec.15 (ANI): NASA has given a University of Maryland-led team of scientists the green light to fly the Deep Impact spacecraft to the Comet Hartley 2 on a two-part extended mission known as EPOXI.
The spacecraft will fly by Earth on New Year’s Eve at the beginning of a more than two-and-a-half-year journey to Hartley 2.
The EPOXI Mission is actually two new missions in one. During the first six months of the journey to Hartley 2, the Extra-solar Planet Observations and Characterization (EPOCh) mission will use the larger of the two telescopes on the Deep Impact spacecraft to search for Earth-sized planets around five stars selected as likely candidates for such planets.
Upon arriving at the comet the Deep Impact extended Investigation (DIXI) will conduct an extended flyby of Hartley 2 using all three of the spacecraft’s instruments (two telescopes with digital colour cameras and an infrared spectrometer).
“It’s exciting that we can send the Deep Impact spacecraft on a new mission that combines two totally independent science investigations, both of which can help us better understand how solar systems form and evolve,” said Deep Impact leader and University of Maryland astronomer Michael A’Hearn, who is principal investigator (PI) for both the overall EPOXI mission and its DIXI Component.
The EPOXI mission brings back the Deep Impact partnership between the University of Maryland, NASA’s Jet Propulsion Laboratory (JPL) and Ball Aerospace and Technologies Corporation, and adds NASA’s Goddard Space Flight Center.
“One of the great surprises of comet explorations has been the wide diversity among the different cometary surfaces imaged to date,” said A’Hearn.
“We want a close look at Hartley 2 to see if the surprises of Tempel 1 are more common than we thought, or if Tempel 1 really is unusual,” he added.
When the Deep Impact/EPOXI spacecraft passes by Earth on December 31, 2007, it will use the pull of our planet’s gravity to direct and speed itself toward comet Hartley 2.
In doing this the spacecraft is aimed toward an encounter with comet Hartley 2 at a time when tracking stations in two different locations on Earth can “see” the spacecraft to receive data from it and send commands to it. In late December 2007, the spacecraft’s instruments will be recalibrated using the Moon as a target.
Hartley 2 was not the original destination of the new mission. It was selected in October following the surprising realization that despite tremendous efforts by many observatories and observers, the scientists could not reliably identify their first choice, Comet Boethin, and its orbit in time to plan the mission flyby of Earth.
The team then recommended to NASA that it be allowed to fly to the backup target, comet Hartley 2.
“Hartley 2 is scientifically just as interesting as Comet Boethin since both have relatively small, active nuclei,” said A’Hearn.
“As we have worked the details of the Comet Hartley 2 encounter, we are confident that the observations will turn out to be even better than Boethin.”
The first part of the Deep Impact extended mission — the search for alien worlds — will begin in late January as the spacecraft cruises toward Hartley 2.
More than 200 alien (extra-solar) planets have been discovered till date. Most of these are detected indirectly, by the gravitational pull they exert on their parent star.
Directly observing extra-solar planets by detecting the light reflected from them is very difficult, because a star’s brilliance obscures light coming from any planets orbiting it.
However, sometimes the orbit of an extra-solar world is aligned so that it eclipses its star as seen from Earth. In these rare cases, light from that planet can be seen directly.
EPOCH will also observe the Earth in visible and infrared wavelengths to allow comparisons with future discoveries of Earth-like planets around other stars.
The mission will observe five nearby stars with “transiting extra-solar planets,” so named because the planet transits, or passes in front of, its star.
“Since Deep Impact will be able to stare at these stars for long periods, we can observe multiple transits and compare the timing to see if there are any hidden worlds,” said Deming, a member of the research team.
In June of 2008, the extended mission will end its EPOCH portion and transition to a long, quiet journey to comet Hartley 2.
The total trip — measured from its December 31, 2007 flyby of Earth to its closest encounter with the comet on October 11, 2010 — will be roughly 1.6 billion miles or some 18 times the distance from the Earth to the sun. It will take the spacecraft three trips around the sun before it can intercept the comet, which at that time will be at a distance of some 12.4 million miles from Earth. (ANI)

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