Deep Impact (spacecraft)

• 1. Mission Genesis And Design

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  A comet-impact mission first appeared on NASA's desk in 1996. Engineers at the agency were skeptical that a probe could hit such a moving target. They needed to prove the concept before committing resources. A revised proposal arrived three years later, in 1999. This version won funding under NASA's Discovery Program for low-cost spacecraft. The total cost of developing the spacecraft and completing its mission reached an unspecified amount, but it was designed to be affordable compared to other deep space projects.

  Ball Aerospace & Technologies built the two main sections in Boulder, Colorado. One part was the copper-core Smart Impactor. It weighed 372 kg and contained a payload called the Cratering Mass. This mass was 100% copper and weighed 113 kg. Copper formed 49% of the total mass of the Impactor. Scientists chose this metal because they did not expect to find copper on a comet. Using copper meant they could ignore its signature in spectrometer readings. The other section was the Flyby spacecraft. It measured about 1 meter long, 1 meter wide, and 1 meter high. It carried solar panels and science instruments for imaging and navigation.

  The software took 18 months to develop. The application code consisted of 20,000 lines spread across 19 different threads. Rick Grammier served as the project manager at NASA's Jet Propulsion Laboratory. He oversaw the integration of these complex systems. The mission required precise calculations to ensure the probe would reach its destination.

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• 2. The Tempel 1 Impact Event

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  Deep Impact launched from Cape Canaveral Air Force Station pad SLC-17B at 18:47 UTC on the 12th of January 2005. A Delta II rocket carried it into space. The spacecraft traveled 174 days to reach comet Tempel 1. On the 3rd of July 2005, it separated into the Impactor and Flyby sections. The Impactor used thrusters to move into the path of the comet. It impacted 24 hours later at a relative speed of 10.2 km/s.

  Impact occurred at 05:52 UTC on the morning of the 4th of July 2005. The energy from the collision was similar in size to exploding five tons of dynamite. Most data captured was stored on board the Flyby spacecraft. It radioed approximately 4,500 images from the HRI, MRI, and ITS cameras to Earth over the next few days. Mission control did not become aware of the success until five minutes later at 05:57 UTC. Don Yeomans confirmed the results for the press, stating they hit the target exactly where planned.

  The impact generated an unexpectedly large and bright dust cloud. This cloud obscured the view of the new crater. Photographs taken by the spacecraft showed the comet to be more dusty and less icy than expected. The entire event was also photographed by Earth-based telescopes including Hubble and Chandra. Cameras aboard Europe's Rosetta spacecraft observed the gas and dust cloud kicked up by the impact.

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• 3. Scientific Discoveries And Results

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  Initial results surprised the science team. Material excavated by the impact contained more dust and less ice than had been expected. Scientists compared the material to talcum powder rather than sand. Analysis of data from the Swift X-ray telescope showed that the comet continued outgassing from the impact for 13 days. A total of 2 million tonnes of water and between 1 million and 2 million tonnes of dust were lost from the impact.

  Observations revealed that the comet was about 75% empty space. One astronomer compared the outer layers of the comet to a snow bank. Clays and carbonates usually require liquid water to form. Sodium is rare in space but appeared in the samples. Astronomers hypothesized that the comet formed in the Uranus and Neptune Oort cloud region of the Solar System. A comet which forms farther from the Sun is expected to have greater amounts of ices with low freezing temperatures, such as ethane.

  Because the quality of the images of the crater formed during the Deep Impact collision was not satisfactory, NASA approved the New Exploration of Tempel 1 mission on the 3rd of July 2007. The Stardust spacecraft passed by Tempel 1 at a distance of approximately 180 kilometers on the 15th of February 2011. This provided an opportunity to better observe the crater created by Deep Impact. The crater is estimated to be 100 meters in diameter.

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• 4. Public Engagement And Media Coverage

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  The mission coincided with celebrations in the Los Angeles area marking the 50th anniversary of Rock Around the Clock by Bill Haley & His Comets becoming the first rock and roll single to reach No. 1 on the recording sales charts. Within 24 hours of the mission's success, a 2-minute music video produced by Martin Lewis had been created using images of the impact itself combined with computer animation. On the 5th of July 2005, the surviving original members of The Comets performed a free concert for hundreds of employees of the Jet Propulsion Laboratory.

  A promotional campaign called Send Your Name To A Comet invited visitors to submit their names between May 2003 and January 2004. Some 625,000 names were gathered and burnt onto a mini-CD attached to the Impactor. Dr. Don Yeomans stated this was an opportunity to become part of an extraordinary space mission. More than 10,000 people watched the collision on a giant movie screen at Hawaii's Waikīkī Beach one day before impact.

  One day after the impact, Marina Bay, a Russian astrologer, sued NASA for $1 million for having ruined the natural balance of forces in the universe. Her lawyer asked the public to volunteer to help in the claim. On the 9th of August 2005, the Presnensky Court of Moscow ruled against Bay. One Russian physicist said that the change to the orbit of the comet after the collision was only about 10 cm.

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• 5. EPOXI Extended Mission Phase

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  In November 2007 the JPL team targeted Deep Impact toward Comet Hartley 2. This required an extra two years of travel including Earth gravity assists in December 2007 and December 2008. On the 28th of May 2010, a burn of 11.3 seconds was conducted to enable the June 27 Earth fly-by to be optimized for the transit to Hartley 2. On the 4th of November 2010, the probe returned images from comet Hartley 2 coming within 700 kilometers of the nucleus.

  The probe also observed Comet Garradd from February 20 to the 8th of April 2012 using its Medium Resolution Instrument. It found that outgassing from the comet varies with a period of 10.4 hours. The dry ice content of the comet was measured and found to be about ten percent of its water ice content by number of molecules.

  On the 3rd of September 2013, a mission update stated communication with the spacecraft was lost some time between August 11 and August 14. The last communication was on August 8. The team determined the cause of the problem on August 30. Controllers believed the computers on the spacecraft were continuously rebooting themselves and so were unable to issue any commands to the vehicle's thrusters. This made communication difficult because the orientation of the antennas was unknown.

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• 6. System Failure And Mission Termination

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  to chief scientist A'Hearn, the reason for the software malfunction was a Y2K-like problem. the 11th of August 2013, at 00:38:49.6 was 232 tenth-seconds from the 1st of January 2000. A system on the craft tracked time in one-tenth second increments since the 1st of January 2000 and stored it in an unsigned 32-bit integer which then overflowed at this time. On the 20th of September 2013, NASA abandoned further attempts to contact the spacecraft.

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