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Deep Impact (EPOXI)
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Deep Impact
Deep Impact (EPOXI) Mission to Earth's Moon Deep Impact (EPOXI) Mission to Earth Deep Impact (EPOXI) Mission to Beyond Our Solar System Deep Impact (EPOXI) Mission to Comets

Mission Type: Flyby, Impact
Launch Vehicle: Delta II 7925 with Star 48 upper stage
Launch Site: Cape Canaveral Air Force Station, Florida
NASA Center: Jet Propulsion Laboratory
Spacecraft Mass: Flyby Spacecraft: 601 kilograms (1,325 pounds) at launch, consisting of 515 kilograms (1,135 pounds) spacecraft and 86 kg (190 lbs) fuel
Impactor: 364 kilograms (802 pounds)
Spacecraft Instruments: 1) High-resolution telescope and camera
2) Medium-resolution wide angle telescope and camera
3) Impactor
Spacecraft Dimensions: Flyby Spacecraft: 3.3 meters (10.8 feet) long, 1.7 meters (5.6 feet) wide, and 2.3 meters (7.5 feet) high
Impactor: 1 meter (39 inches) long, 1 meter (39 inches) in diameter
Spacecraft Power: 2.8-meter-by-2.8-meter (9-foot-by-9 foot) solar panel providing up to 92 watts, depending on distance from Sun. Power storage via small 16-amp-hour rechargeable nickel hydrogen battery
Total Cost: Primary Mission: $267 million total (not including launch vehicle), consisting of $252 million
spacecraft development and $15 million mission operations
Deep Impact Launch Press Kit, January 2005

EPOXI Website, University of Maryland,

A radical mission to excavate the interior of a comet, work on Deep Impact began in January 2000, as part of NASA's Discovery Program. The spacecraft launched from Cape Canaveral on 12 January 2005, beginning its 268-million-mile journey to comet 9P/Tempel 1. The two-part spacecraft consisted of a larger flyby spacecraft carrying a smaller impactor spacecraft.

On 2 July 2005, at 11:07 PDT, the impactor was successfully released at a distance of about 547,000 miles from the comet. The battery-powered, 770-lb impactor was designed to operate independently for just one day, taking over its own navigation and maneuvering into the path of the comet.

Nearly 24 hours later, at 10:52 pm PDT on 3 July, traveling at a speed of 23,000 miles per hour, the impactor successfully placed itself into the path of comet Tempel 1. A camera on the impactor captured and relayed images of the comet nucleus as it approached and just before it collided with the comet.

From 300 miles away, the flyby spacecraft observed and recorded the impact and the ejected material blasted from the crater. The collision sent a huge, bright cloud of debris upward and outward from the comet. Scientists were surprised to learn that the cloud was not composed of water, ice and dirt. Instead, Deep Impact's instruments indicated that the huge cloud was made up of very fine, powdery material. Due to the massive amounts of dust, science team members could only estimate the crater's size to be about 325 to 825 feet in diameter.

After Deep Impact's flyby and impact of comet Tempel 1, the spacecraft was repurposed and renamed Deep Impact (EPOXI) and sent to fly by a second comet. (EPOXI stands for, and is a combination of, two acronyms: EPOCh [Extrasolar Planet Observation and Characterization] and DIXI [Deep Impact Extended Investigation]).

The original plan was to conduct a flyby of comet Boethin. Unfortunately, this comet was not found -- scientists believe that this comet broke up into smaller pieces, too small to detect. A new comet was selected for the flyby: comet 103P/Hartley (Hartley 2).

The spacecraft encountered comet Hartley 2 on 4 November 2010 at a distance of 694 km (431 miles). Called hyperactive by the EPOXI mission, comet Hartley 2 spins around one axis, while tumbling around another one. Comet Hartley's core is also not uniform, but is made up of water ice with methanol, carbon dioxide and possibly ethane. The release of these gases occur at different locations on the comet. For example, carbon-dioxide-driven jets shoot from the ends of the comet, with most occurring from the small end. Water vapor is released from the mid-section with very little, or no carbon dioxide or ice. The comet's surface is dotted with glittering blocks that are approximately 50 m (164 feet) high and 80 m (262 feet) wide. These surface features appear to be two to three times more reflective than the surface average.

Beginning on 8 August 2013, ground controllers were unable to communicate with the spacecraft. Mission controllers continued to uplink commands in an attempt to re-establish communications with the spacecraft. In September 2013, the mission was officially ended.


Banner says visit the Deep Impact Legacy Site
Key Dates
12 Jan 2005:  Launch
4 Jul 2005:  Comet Tempel 1 Impact
4 Nov 2010:  Comet Hartley 2 Encounter
8 Aug 2013:  Communication with Spacecraft Lost
Status: Successful
Fast Facts
Deep Impact Facts Deep Impact was the first mission to eject material from a comet's surface.

It is a coincidence that Deep Impact shares its name with a 1998 science fiction disaster film about a comet.

Author Arthur C. Clarke suggested the idea of impacting a comet in his novel 2001: A Space Odyssey

Deep Impact's small probe was the first manmade object to collide with a comet (right).

EPOXI has double meaning. EPO stands for EPOCh the Extrasolar Planet Observation and Characterization phase of mission. XI is short for the spacecraft's extended investigation of comets.

EPOXI is an entirely new mission for a spacecraft already in orbit around our sun.
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Last Updated: 9 Apr 2014