posted 12-13-2007 09:27 PM               

NASA Sends Spacecraft on Mission to Comet Hartley 2

NASA has approved the retargeting of the EPOXI mission for a flyby of comet Hartley 2 on Oct. 11, 2010. Hartley 2 was chosen as EPOXI's destination after the initial target, comet Boethin, could not be found. Scientists theorize comet Boethin may have broken up into pieces too small for detection.

The EPOXI mission melds two compelling science investigations -- the Extrasolar Planet Observation and Characterization and the Deep Impact Extended Investigation. Both investigations will be performed using the Deep Impact spacecraft.

In addition to investigating comet Hartley 2, the spacecraft will point the larger of its two telescopes at nearby exosolar planetary systems in late January 2008 to observe several previously discovered planetary systems outside our solar system. It will study the physical properties of giant planets and search for rings, moons and planets as small as three Earth masses. It also will look at Earth as though it were an exosolar planet to provide data that could become the standard for characterizing these types of planets.

"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 the small half-mile-wide comet will be about 620 miles. The spacecraft will employ the same suite of two science instruments the Deep Impact spacecraft used during its prime mission to guide an impactor into comet Tempel 1 in July 2005.

If EPOXI's observations of Hartley 2 show it is similar to one of the other comets that have been observed, this new class of comets will be defined for the first time. If the comet displays different characteristics, it would deepen the mystery of cometary diversity.

"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, Calif.

Mission controllers at JPL began directing EPOXI towards Hartley 2 on Nov. 1. They commanded the spacecraft to perform a three-minute rocket burn that changed the spacecraft's velocity. EPOXI's new trajectory sets the stage for three Earth flybys, the first on Dec. 31, 2007. This places the spacecraft into an orbital "holding pattern" until time for the optimal encounter of comet Hartley 2 in 2010.

"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.

EPOXI's low mission cost of $40 million is achieved by taking advantage of the existing Deep Impact spacecraft.

JPL manages EPOXI for NASA's Science Mission Directorate, Washington. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

posted 10-08-2010 12:28 AM               

NASA Mission 'E-Minus' One Month to Comet Flyby

Fans of space exploration are familiar with the term T-minus, which NASA uses as a countdown to a rocket launch. But what of those noteworthy mission events where you already have a spacecraft in space, as with the upcoming flyby of a comet?

"We use 'E-minus' to help with our mission planning," said Tim Larson, EPOXI mission project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The 'E' stands for encounter, and that is exactly what is going to happen one month from today, when our spacecraft has a close encounter with comet Hartley 2."

The EPOXI mission's Nov. 4 encounter with Hartley 2 will be only the fifth time in history that a comet has been imaged close-up. At point of closest approach, the spacecraft will be about 700 kilometers (435 miles) from the comet.

"Hartley 2 better not blink, because we'll be screaming by at 12.3 kilometers per second (7.6 miles per second), said Larson.

One month out, the spacecraft is closing the distance with the comet at a rate of 976,000 kilometers (607,000 miles) per day. As it gets closer, the rate of closure will increase to a little over 1,000,000 kilometers (620,000 miles) per day.

For those interested in what the "T-minus" stands for in a NASA countdown to a rocket launch – it translates to "Time-minus." For example, when a rocket is getting ready for liftoff, it will be lifting off at a specific time. If that time is 45 seconds away, it is said to be "T-minus 45 seconds and counting."

EPOXI is an extended mission that utilizes the already "in-flight" Deep Impact spacecraft to explore distinct celestial targets of opportunity. The name EPOXI itself is a combination of the names for the two extended mission components: the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft will continue to be referred to as "Deep Impact."

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the EPOXI mission for NASA's Science Mission Directorate, Washington. The University of Maryland, College Park, is home to the mission's principal investigator, Michael A'Hearn. Drake Deming of NASA's Goddard Space Flight Center, Greenbelt, Md., is the science lead for the mission's extrasolar planet observations. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

posted 10-14-2010 11:47 PM               

Encounter Schedule

Here is a timeline for the remainder of the EPOXI mission, updated on Oct. 14, 2010. Note that special event times, like press telecons and USTREAM events, are subject to change. The official EPOXI website, epoxi.umd.edu, will have the most up to date changes to the schedule.

• 10/01/10: The E-34 to E-8 day imaging sequence was initiated. During this period, the Deep Impact spacecraft acquires images every 5 minutes and spectral scans every 30 minutes. This phase is characterized by the spacecraft slewing to an image attitude for 16 hours/day and then slewing to a COMM attitude to downlink images. The spacecraft is expected to remain at the COMM attitude between 5.5 to 7.5 hours before returning to an image attitude. Select image and science result releases will be available at epoxi.umd.edu.

• 10/20/10: Comet Hartley 2 will pass within 0.12 AU of the Earth.

• 10/27/10: The E-8 day Trajectory Correction Maneuver (TCM-21) is planned to execute today at 11:00 am PDT. This brings the E-34 to E-8 day observing sequence to a close. The spacecraft is now 8.5 million km away from the comet.

• 10/28/10: First thing today, Hartley 2 will pass through perihelion. Observations resume with the start of the E-7 to E-1 day imaging sequence. The spacecraft will image the comet every 2 minutes, with gas band images interspersed, and spectral scans every hour. The observing occurs for 16 hours/day with an 8 hour/day downlink.

• 10/30/10: At E-4 days, a Go/No-Go Management Decision will be made as to whether TCM-22 needs to be implemented. If the spacecraft trajectory is within mission limits, the TCM is not required.

• 11/02/10: At 3:00 pm PDT, the TCM-22 burn will occur if needed. The spacecraft is now 1.8 million km from the comet.

• 11/03/10: Final preparation begins for the start of the critical sequence. The last pre-encounter data download will occur today. A decision will be made by the management team as to whether a pointing update or commanded time offset needs to be executed prior to closest approach while the spacecraft is still 1 million km from the comet. The E-18 hour to E+30 minute high resolution encounter observation sequence will commence at 12:50 pm PDT with all data of the encounter stored onboard the spacecraft because the high gain antenna (HGA) is pointed away from the Earth and not capable of downlinking data during the encounter sequence.

• 11/04/10: AutoNav is expected to be enabled at E-50 minutes and fly the spacecraft through closest approach. The cometary nucleus will be resolved ~1 hour out with the spacecraft 45,000 km away from its target. **Closest approach of comet Hartley 2 is expected to occur at ~6:50 am PDT at a distance of 700 km.** Hartley 2 will be 1.064 AU from the Sun and 0.156 AU from the Earth at this time. The spacecraft will be approaching the comet at a phase angle of 86 degrees. The MRI pixel scale at closest approach will be 7 m/pixel, giving a nuclear diameter of ~170 pixels in the highest resolution images. NASA TV will be covering the EPOXI Flight and Science Teams at JPL from 6:30 am - 8:10 am PDT. The first data downlink after encounter is scheduled to start at E+30 minutes, once the spacecraft's HGA is pointed to the Earth. The data will continue to download from the spacecraft through 11/06/10.

  A post-encounter live press briefing is scheduled for 1:00 pm PDT at JPL and will include members from the Flight and Science Teams as well as a NASA HQ representative. Prior to the press conference, 5 raw images from closest approach will be released on the EPOXI website, epoxi.umd.edu, as soon as they are available from the spacecraft. Processed versions of these images will be presented during the press conference. The press conference will be aired live on NASA TV.

• 11/06/10: The encounter data downlink will have completed and the E+2 to E+12 day post-encounter observations will begin with continuous imaging and downlink. Imaging will occur every 2 minutes and spectral scans will be collected every 15 minutes.

• 11/16/10: The E+12 to E+21 day sequence is kicked off. These observations have a reduced acquisition frequency, with both imaging and spectra collected every 30 minutes.

• 11/30/10: The last EPOXI observations will take place with a post-encounter cruise calibration. The EPOXI Science Team will continue to analyze data from Hartley 2 for several months. Key science results will be posted to the EPOXI website, epoxi.umd.edu, as they are released.

posted 11-04-2010 01:57 PM               

NASA Mission Successfully Flies by Comet Hartley 2

NASA's EPOXI mission successfully flew by comet Hartley 2 at about 7 a.m. PDT (10 a.m. EDT) today, and the spacecraft has begun returning images. Hartley 2 is the fifth comet nucleus visited by a spacecraft.

Image credit: NASA/JPL-Caltech/UMD

Comet Hartley 2 can be seen in glorious detail in this image from NASA's EPOXI mission. It was taken as the spacecraft flew by around 6:59 a.m. PDT (9:59 a.m. EDT), from a distance of about 700 kilometers (435 miles). The comet's nucleus, or main body, is approximately 2 kilometers (1.2 miles) long and .4 kilometers (.25 miles) at the "neck," or most narrow portion. Jets can be seen streaming out of the nucleus.

Scientists and mission controllers are currently viewing never-before-seen images of Hartley 2 appearing on their computer terminal screens.

"The mission team and scientists have worked hard for this day," said Tim Larson, EPOXI project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It's good to see Hartley 2 up close."

Mission navigators are working to determine the spacecraft's closest approach distance. Preliminary estimates place the spacecraft close to the planned-for 700 kilometers (435 miles). Eight minutes after closest approach, at 6:59:47 a.m. PDT ( 9:59:47 a.m. EDT), the spacecraft's high-gain antenna was pointed at Earth and began downlinking vital spacecraft health and other engineering data stored aboard the spacecraft's onboard computer during the encounter. About 20 minutes later, the first images of the encounter made the 37-million-kilometer (23-million-mile) trip from the spacecraft to NASA's Deep Space Network antennas in Goldstone, Calif., appearing moments later on the mission's computer screens.

"We are all holding our breath to see what discoveries await us in the observations near closest approach," said EPOXI principal investigator Michael A'Hearn of the University of Maryland, College Park.

posted 11-05-2010 05:54 AM               

NASA EPOXI Flyby Reveals New Insights Into Comet Features

NASA's EPOXI mission spacecraft successfully flew past comet Hartley 2 at 10 a.m. EDT Thursday. Scientists say initial images from the flyby provide new information about the comet's volume and material spewing from its surface.

"Early observations of the comet show that, for the first time, we may be able to connect activity to individual features on the nucleus," said EPOXI principal investigator Michael A'Hearn of the University of Maryland, College Park. "We certainly have our hands full. The images are full of great cometary data, and that's what we hoped for."

EPOXI is an extended mission that uses the already in-flight Deep Impact spacecraft. Its encounter phase with Hartley 2 began at 4 p.m. EDT on Nov. 3, when the spacecraft began to point its two imagers at the comet's nucleus. Imaging of the nucleus began one hour later.

"The spacecraft has provided the most extensive observations of a comet in history," said Ed Weiler, associate administrator for NASA's Science Mission Directorate at the agency's Headquarters in Washington. "Scientists and engineers have successfully squeezed world class science from a re-purposed spacecraft at a fraction of the cost to taxpayers of a new science project."

Images from the EPOXI mission reveal comet Hartley 2 to have 100 times less volume than comet Tempel 1, the first target of Deep Impact. More revelations about Hartley 2 are expected as analysis continues.

Initial estimates indicate the spacecraft was about 435 miles from the comet at the closest-approach point. That's almost the exact distance that was calculated by engineers in advance of the flyby.

"It is a testament to our team's skill that we nailed the flyby distance to a comet that likes to move around the sky so much," said Tim Larson, EPOXI project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "While it's great to see the images coming down, there is still work to be done. We have another three weeks of imaging during our outbound journey."

The name EPOXI is a combination of the names for the two extended mission components: the Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft has retained the name Deep Impact. In 2005, Deep Impact successfully released an impactor into the path of comet Tempel 1.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the EPOXI mission for NASA's Science Mission Directorate. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., in Boulder, Colo.

posted 09-10-2013 06:54 PM               

The spacecraft's handlers lost contact with Deep Impact — which slammed an impactor into Comet Tempel 1 in 2005, made a close flyby of Comet Hartley 2 in 2010 and recently observed ISON, a "comet of the century" candidate — sometime between Aug. 11 and Aug. 14, mission team members announced Sept. 3.

"The last communication was on August 8. After considerable effort, the team on August 30 determined the cause of the problem," principal investigator Mike A'Hearn of the University of Maryland wrote in a brief mission update Tuesday. "The team is now trying to determine how best to try to recover communication."

posted 09-20-2013 10:20 AM               

NASA's Deep Space Comet Hunter Mission Comes to an End

After almost 9 years in space that included an unprecedented July 4th impact and subsequent flyby of a comet, an additional comet flyby, and the return of approximately 500,000 images of celestial objects, NASA's Deep Impact mission has ended.

The project team at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., has reluctantly pronounced the mission at an end after being unable to communicate with the spacecraft for over a month. The last communication with the probe was Aug. 8. Deep Impact was history's most traveled comet research mission, going about 4.7 billion miles (7.58 billion kilometers).

"Deep Impact has been a fantastic, long-lasting spacecraft that has produced far more data than we had planned," said Mike A'Hearn, the Deep Impact principal investigator at the University of Maryland in College Park. "It has revolutionized our understanding of comets and their activity."

Deep Impact successfully completed its original bold mission of six months in 2005 to investigate both the surface and interior composition of a comet, and a subsequent extended mission of another comet flyby and observations of planets around other stars that lasted from July 2007 to December 2010. Since then, the spacecraft has been continually used as a space-borne planetary observatory to capture images and other scientific data on several targets of opportunity with its telescopes and instrumentation.

Launched in January 2005, the spacecraft first traveled about 268 million miles (431 million kilometers) to the vicinity of comet Tempel 1. On July 3, 2005, the spacecraft deployed an impactor into the path of comet to essentially be run over by its nucleus on July 4. This caused material from below the comet's surface to be blasted out into space where it could be examined by the telescopes and instrumentation of the flyby spacecraft. Sixteen days after that comet encounter, the Deep Impact team placed the spacecraft on a trajectory to fly back past Earth in late December 2007 to put it on course to encounter another comet, Hartley 2 in November 2010.

"Six months after launch, this spacecraft had already completed its planned mission to study comet Tempel 1," said Tim Larson, project manager of Deep Impact at JPL. "But the science team kept finding interesting things to do, and through the ingenuity of our mission team and navigators and support of NASA's Discovery Program, this spacecraft kept it up for more than eight years, producing amazing results all along the way."

The spacecraft's extended mission culminated in the successful flyby of comet Hartley 2 on Nov. 4, 2010. Along the way, it also observed six different stars to confirm the motion of planets orbiting them, and took images and data of the Earth, the Moon and Mars. These data helped to confirm the existence of water on the Moon, and attempted to confirm the methane signature in the atmosphere of Mars. One sequence of images is a breathtaking view of the Moon transiting across the face of Earth.

In January 2012, Deep Impact performed imaging and accessed the composition of distant comet C/2009 P1 (Garradd). It took images of comet ISON this year and collected early images of comet ISON in June.

After losing contact with the spacecraft last month, mission controllers spent several weeks trying to uplink commands to reactivate its onboard systems. Although the exact cause of the loss is not known, analysis has uncovered a potential problem with computer time tagging that could have led to loss of control for Deep Impact's orientation. That would then affect the positioning of its radio antennas, making communication difficult, as well as its solar arrays, which would in turn prevent the spacecraft from getting power and allow cold temperatures to ruin onboard equipment, essentially freezing its battery and propulsion systems.

"Despite this unexpected final curtain call, Deep Impact already achieved much more than ever was envisioned," said Lindley Johnson, the Discovery Program Executive at NASA Headquarters, and the Program Executive for the mission since a year before it launched. "Deep Impact has completely overturned what we thought we knew about comets and also provided a treasure trove of additional planetary science that will be the source data of research for years to come."

The mission is part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. JPL manages the Deep Impact mission for NASA's Science Mission Directorate in Washington. Ball Aerospace & Technologies Corp. of Boulder, Colo., built the spacecraft.