EPOXI
Encyclopedia
EPOXI is a NASA
unmanned space mission led by the University of Maryland
using the existing Deep Impact vehicle to begin a new series of observations. It first investigated extrasolar planet
s and, on November 4, 2010, it performed a close approach to the comet
103P/Hartley
(alternately named Hartley 2). The new mission was originally announced on 3 July 2007 as including flyby of comet 85P/Boethin
, but Boethin was too small and faint for its orbit to be calculated accurately, so the mission was subsequently retargeted for a 103P/Hartley flyby. NASA and the University of Maryland confirmed funding for the 103P/Hartley flyby in news releases issued on December 13, 2007.
EPOXI combines two targets: the Deep Impact Extended Investigation (DIXI), and the Extrasolar Planet Observation and Characterization (EPOCh). Deep Impact will conduct both missions, the Extrasolar Planet Observation and Characterization during the cruise phase to 103P/Hartley, and the Deep Impact Extended Investigation at flyby. The spacecraft was also used as a test platform for a delay-tolerant networking transmission while at a distance of 20 million miles from Earth.
As of November 2011, there will be a senior review of all operating planetary exploration missions at NASA. That will likely include a review of the status of the Deep Impact Flyby spacecraft to determine whether an additional extended mission should be approved. Decisions will not occur until early 2012.
NASA's Jet Propulsion Laboratory
, in Pasadena
, California., manages EPOXI for NASA's Science Mission Directorate, Washington. The Principal Investigator
is Michael A'Hearn
.
s in an attempt to find other such stars nearby. The larger of the spacecraft's two telescopes attempts to find the planets using the transit method.
The initial plan was for a December 5, 2008 flyby of Comet Boethin, with the spacecraft coming within 435 miles (700.1 km). The spacecraft did not carry a second impactor to collide with the comet and would observe the comet to compare it to various characteristics found on 9P/Tempel
. A'Hearn, the Deep Impact team leader reflected on the upcoming project at that time: "We propose to direct the spacecraft for a flyby of Comet Boethin to investigate whether the results found at Comet Tempel 1 are unique or are also found on other comets." He explained that the mission would provide only about half of the information collected during the collision with Tempel 1 but at a fraction of the cost. (EPOXI’s low mission cost of $40 million is achieved by reusing the existing Deep Impact spacecraft.) Deep Impact would use its spectrometer
to study the comet's surface composition and its telescopes for viewing the surface features.
However, as the Earth gravity assist approached, astronomers were unable to locate Comet Boethin, which is too faint to be observed. Consequently, its orbit could not be calculated with sufficient precision to permit a flyby. Instead, the team decided to send Deep Impact to comet 103P/Hartley
requiring an extra two years. NASA approved the additional funding required and retargeted the spacecraft. Mission controllers at the Jet Propulsion Laboratory began redirecting EPOXI on November 1, 2007. They commanded the spacecraft to perform a three-minute rocket burn that changed the spacecraft's velocity. EPOXI’s new trajectory set the stage for three Earth flybys, the first on December 31, 2007. This placed the spacecraft into an orbital "holding pattern" so that it could encounter comet 103P/Hartley in 2010.
"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 in December 2007 Deep Impact leader and University of Maryland astronomer Michael A'Hearn
who is principal investigator for both the overall EPOXI mission and its DIXI component.
In June 2009, EPOXI's spectrometer scanned the Moon on its way to Hartley, and discovered traces of "water or hydroxyl", confirming a Moon Mineralogy Mapper
observation — a discovery announced in late September, 2009.
s from January to August 2008. The goal of photometric
observations is to measure the quantity of light, not necessarily resolve an image. An aberration in the primary mirror of the HRI allowed the HRI to spread the light from observations over more pixels without saturating the CCD, effectively obtaining better data. A total of 198,434 images were exposed. EPOCh's goals were to study the physical properties of giant planets and search for rings, moons and planets as small as three Earth masses. It also looked at Earth as though it were an extrasolar planet to provide data that could characterize Earth-type planets for future missions, and it imaged the Earth over 24 hours to capture the Moon passing in front on 2008-05-29.
"The search for exosolar planetary systems is one of the most intriguing explorations of our time," said Drake Deming, EPOXI deputy principal investigator at NASA's Goddard Space Flight Center, Greenbelt, Md. "With EPOXI we have the potential to discover new worlds and even analyze the light they emit to perhaps discover what atmospheres they possess."
The mission's closest approach to 103P/Hartley occurred at 10 am EDT on 4 November 2010, passing to within 694 kilometres (431.2 mi) of this small comet. The flyby speed was 12.3 km/s. The spacecraft employed the same suite of three science instruments—two telescopes and an infrared spectrometer—that the Deep Impact spacecraft used during its prime mission to guide an impactor into comet Tempel 1 in July 2005 and observe the results.
Early results of the observations show that the comet is powered by dry ice
, not water vapor as was previously thought.The images were clear enough for scientists to link jets of dust and gas with specific surface features.
"When comet Boethin could not be located, we went to our backup, which is every bit as interesting but about two years farther down the road," said Tom Duxbury, EPOXI project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "Hartley 2 is scientifically just as interesting as comet Boethin because both have relatively small, active nuclei," said Michael A'Hearn
, principal investigator for EPOXI at the University of Maryland, College Park.
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
unmanned space mission led by the University of Maryland
University of Maryland, College Park
The University of Maryland, College Park is a top-ranked public research university located in the city of College Park in Prince George's County, Maryland, just outside Washington, D.C...
using the existing Deep Impact vehicle to begin a new series of observations. It first investigated extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
s and, on November 4, 2010, it performed a close approach to the comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
103P/Hartley
103P/Hartley
Comet Hartley 2, designated as 103P/Hartley by the Minor Planet Center, is a small periodic comet with an orbital period of 6.46 years. It was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit, Siding Spring Observatory, Australia...
(alternately named Hartley 2). The new mission was originally announced on 3 July 2007 as including flyby of comet 85P/Boethin
85P/Boethin
Comet Boethin is a periodic comet discovered in 1975 by Reverend Leo Boethin. It appeared again in 1986 January as expected...
, but Boethin was too small and faint for its orbit to be calculated accurately, so the mission was subsequently retargeted for a 103P/Hartley flyby. NASA and the University of Maryland confirmed funding for the 103P/Hartley flyby in news releases issued on December 13, 2007.
EPOXI combines two targets: the Deep Impact Extended Investigation (DIXI), and the Extrasolar Planet Observation and Characterization (EPOCh). Deep Impact will conduct both missions, the Extrasolar Planet Observation and Characterization during the cruise phase to 103P/Hartley, and the Deep Impact Extended Investigation at flyby. The spacecraft was also used as a test platform for a delay-tolerant networking transmission while at a distance of 20 million miles from Earth.
As of November 2011, there will be a senior review of all operating planetary exploration missions at NASA. That will likely include a review of the status of the Deep Impact Flyby spacecraft to determine whether an additional extended mission should be approved. Decisions will not occur until early 2012.
NASA's Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
, in Pasadena
Pasadena, California
Pasadena is a city in Los Angeles County, California, United States. Although famous for hosting the annual Rose Bowl football game and Tournament of Roses Parade, Pasadena is the home to many scientific and cultural institutions, including the California Institute of Technology , the Jet...
, California., manages EPOXI for NASA's Science Mission Directorate, Washington. The Principal Investigator
Principal investigator
A principal investigator is the lead scientist or engineer for a particular well-defined science project, such as a laboratory study or clinical trial....
is Michael A'Hearn
Michael A'Hearn
Michael F. A'Hearn is an astronomer and professor at the University of Maryland who is the principal investigator for the NASA EPOXI mission. He was the principal investigator for the NASA Deep Impact mission. He received his bachelors in science at Boston College and his Ph. D in Astronomy at the...
.
Mission
The Deep Impact mission was finished with the visit to comet Tempel 1. But the spacecraft still had plenty of maneuvering fuel left, so NASA approved a second mission, called EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation), which included a visit to a second comet (DIXI component) as well as observations of extrasolar planets (EPOCh component).Comet Boethin lost
On July 21, 2005, Deep Impact executed a trajectory correction maneuver that placed the spacecraft on course to fly past Earth on December 31, 2007. The maneuver allowed the spacecraft to use Earth's gravity to begin a new mission in a path towards another comet. In January 2008 Deep Impact began studying the stars with several known extrasolar planetExtrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
s in an attempt to find other such stars nearby. The larger of the spacecraft's two telescopes attempts to find the planets using the transit method.
The initial plan was for a December 5, 2008 flyby of Comet Boethin, with the spacecraft coming within 435 miles (700.1 km). The spacecraft did not carry a second impactor to collide with the comet and would observe the comet to compare it to various characteristics found on 9P/Tempel
9P/Tempel
Tempel 1 , is a periodic comet discovered by Wilhelm Tempel in 1867. It currently completes an orbit of the Sun every 5.5 years. Tempel 1 was the target of the Deep Impact space mission, which photographed a deliberate high-speed impact upon the comet in 2005...
. A'Hearn, the Deep Impact team leader reflected on the upcoming project at that time: "We propose to direct the spacecraft for a flyby of Comet Boethin to investigate whether the results found at Comet Tempel 1 are unique or are also found on other comets." He explained that the mission would provide only about half of the information collected during the collision with Tempel 1 but at a fraction of the cost. (EPOXI’s low mission cost of $40 million is achieved by reusing the existing Deep Impact spacecraft.) Deep Impact would use its spectrometer
Spectrometer
A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
to study the comet's surface composition and its telescopes for viewing the surface features.
103P/Hartley
Comet Hartley 2, designated as 103P/Hartley by the Minor Planet Center, is a small periodic comet with an orbital period of 6.46 years. It was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit, Siding Spring Observatory, Australia...
requiring an extra two years. NASA approved the additional funding required and retargeted the spacecraft. Mission controllers at the Jet Propulsion Laboratory began redirecting EPOXI on November 1, 2007. They commanded the spacecraft to perform a three-minute rocket burn that changed the spacecraft's velocity. EPOXI’s new trajectory set the stage for three Earth flybys, the first on December 31, 2007. This placed the spacecraft into an orbital "holding pattern" so that it could encounter comet 103P/Hartley in 2010.
"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 in December 2007 Deep Impact leader and University of Maryland astronomer Michael A'Hearn
Michael A'Hearn
Michael F. A'Hearn is an astronomer and professor at the University of Maryland who is the principal investigator for the NASA EPOXI mission. He was the principal investigator for the NASA Deep Impact mission. He received his bachelors in science at Boston College and his Ph. D in Astronomy at the...
who is principal investigator for both the overall EPOXI mission and its DIXI component.
In June 2009, EPOXI's spectrometer scanned the Moon on its way to Hartley, and discovered traces of "water or hydroxyl", confirming a Moon Mineralogy Mapper
Moon Mineralogy Mapper
The Moon Mineralogy Mapper is one of two instruments that NASA contributed to India's first mission to the Moon, Chandrayaan-1, launched October 22, 2008...
observation — a discovery announced in late September, 2009.
EPOCh
Before the 2008 flyby to re-orient for the comet 103P/Hartley encounter, the spacecraft used High Resolution Instrument, the larger of its two telescopes, to perform photometric observations of previously discovered transiting extrasolar planetExtrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
s from January to August 2008. The goal of photometric
Photometry (astronomy)
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation...
observations is to measure the quantity of light, not necessarily resolve an image. An aberration in the primary mirror of the HRI allowed the HRI to spread the light from observations over more pixels without saturating the CCD, effectively obtaining better data. A total of 198,434 images were exposed. EPOCh's goals were to study the physical properties of giant planets and search for rings, moons and planets as small as three Earth masses. It also looked at Earth as though it were an extrasolar planet to provide data that could characterize Earth-type planets for future missions, and it imaged the Earth over 24 hours to capture the Moon passing in front on 2008-05-29.
| Star Star A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth... |
Constellation Constellation In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky.... |
Distance (ly) | Planet Planet A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,... |
|---|---|---|---|
| XO-2 XO-2 XO-2 may refer to:*XO-2b - An extrasolar planet orbiting the star XO-2 in the constellation Lynx*XO-2 - A star with exoplanet XO-2b in orbit around it*OLPC XO-2 - A design study of the One Laptop per Child computer... |
Lynx Lynx (constellation) Lynx is a constellation in the northern sky, introduced in the 17th century by Johannes Hevelius. It is named after the lynx, a genus of cat. It is a very faint constellation; its brightest stars form a zigzag line.-History:... |
486 | b XO-2b XO-2b is an extrasolar planet orbiting the star XO-2 in the constellation Lynx. This planet was found by transit method in 2007 by Burke et al... |
| Gliese 436 | Leo Leo (constellation) Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is . Leo lies between dim Cancer to the west and Virgo to the east.-Stars:... |
33.48 | b Gliese 436 b Gliese 436 b is a Neptune-sized extrasolar planet orbiting the red dwarf star Gliese 436. It was among the smallest known transiting planets in mass and radius until the much smaller Kepler discoveries started coming in 2010.-Discovery:... |
| BD+36°2593 BD+36°2593 |- bgcolor="#FFFAFA"| Equatorial [ g ] || ~136,5 m/s2HAT-P-4 is a yellow dwarf star in the constellation of Boötes. It is also designated BD+36°2593.- Planetary System :... |
Boötes Boötes Boötes is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from the Greek Βοώτης, Boōtēs, meaning herdsman or plowman... |
1010 | HAT-P-4b HAT-P-4b HAT-P-4b is an extrasolar planet orbiting the star HAT-P-4 over 1000 light years away in Boötes constellation. It was discovered by transit on October 2, 2007, which looks for slight dimming of stars caused by planets that passed in front of them... |
| GSC 03089-00929 GSC 03089-00929 GSC 03089-00929 is a magnitude 12 star located approximately 1300 light-years away in the constellation of Hercules. This star is a G type main sequence star that is similar to but slightly cooler than our sun.... |
Hercules Hercules (constellation) Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations today... |
1300 | TrES-3 TrES-3 TrES-3b is an extrasolar planet orbiting the star GSC 03089-00929. It has an orbital period of just 31 hours and is undergoing orbital decay due to tidal effects. It has nearly twice the mass of Jupiter.... |
| WASP-3 WASP-3 WASP-3 is a magnitude 10 yellow-white dwarf star located about 727 light-years away in the Lyra constellation.-Planetary system:The extrasolar planet WASP-3b was detected by the SuperWASP project in 2007.... |
Lyra | 727 | b WASP-3b WASP-3b is an extrasolar planet orbiting the star WASP-3 located over 727 light-years away in the constellation Lyra. It was discovered via the transit method by SuperWASP, and follow up radial velocity observations confirmed that WASP-3b is a planet. The planet's mass and radius indicate that it... |
| GSC 03549-02811 GSC 03549-02811 GSC 03549-02811 A is a yellow main-sequence star similar to our Sun. This star is located approximately 718 light-years away in the constellation of Draco. The apparent magnitude of this star is 11.41, which means it is not visible to the naked eye but can be seen with a medium-sized amateur... |
Draco Draco (constellation) Draco is a constellation in the far northern sky. Its name is Latin for dragon. Draco is circumpolar for many observers in the northern hemisphere... |
718 | TrES-2 TrES-2 TrES-2b is an extrasolar planet orbiting the star GSC 03549-02811 located 718 light years away from our solar system. The planet has been identified in 2011 as the darkest known exoplanet, reflecting less than 1% of any light that hits it. The planet's mass and radius indicate that it is a gas... |
| HAT-P-7 HAT-P-7b HAT-P-7b is an extrasolar planet discovered in 2008. It orbits very close to its parent star GSC 03547-01402, and is both larger and more massive than Jupiter. Due to the extreme heat it receives from its star, the dayside temperature is predicted to be 2730 K... |
Cygnus Cygnus (constellation) Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross... |
1044 | b HAT-P-7b HAT-P-7b is an extrasolar planet discovered in 2008. It orbits very close to its parent star GSC 03547-01402, and is both larger and more massive than Jupiter. Due to the extreme heat it receives from its star, the dayside temperature is predicted to be 2730 K... |
"The search for exosolar planetary systems is one of the most intriguing explorations of our time," said Drake Deming, EPOXI deputy principal investigator at NASA's Goddard Space Flight Center, Greenbelt, Md. "With EPOXI we have the potential to discover new worlds and even analyze the light they emit to perhaps discover what atmospheres they possess."
Comet flyby
The spacecraft used Earth's gravity for the second gravity assist in December 2008 and made two distant flybys of Earth in June and December 2009. On May 30, 2010 it successfully fired its engines for an 11.3 second trajectory correction maneuver, for a velocity change (ΔV) of 0.1 metre per second (0.22369362920544 mph), in preparation for the third Earth flyby on June 27. Observations of 103P/Hartley began on September 5 and ended November 25, 2010. For a diagram of the EPOXI solar orbits see here.The mission's closest approach to 103P/Hartley occurred at 10 am EDT on 4 November 2010, passing to within 694 kilometres (431.2 mi) of this small comet. The flyby speed was 12.3 km/s. The spacecraft employed the same suite of three science instruments—two telescopes and an infrared spectrometer—that the Deep Impact spacecraft used during its prime mission to guide an impactor into comet Tempel 1 in July 2005 and observe the results.
Early results of the observations show that the comet is powered by dry ice
Dry ice
Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...
, not water vapor as was previously thought.The images were clear enough for scientists to link jets of dust and gas with specific surface features.
"When comet Boethin could not be located, we went to our backup, which is every bit as interesting but about two years farther down the road," said Tom Duxbury, EPOXI project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "Hartley 2 is scientifically just as interesting as comet Boethin because both have relatively small, active nuclei," said Michael A'Hearn
Michael A'Hearn
Michael F. A'Hearn is an astronomer and professor at the University of Maryland who is the principal investigator for the NASA EPOXI mission. He was the principal investigator for the NASA Deep Impact mission. He received his bachelors in science at Boston College and his Ph. D in Astronomy at the...
, principal investigator for EPOXI at the University of Maryland, College Park.