This spectacular image of comet Tempel 1 was taken 67 seconds after it obliterated Deep Impact's impactor spacecraft. The image was taken by the high-resolution camera on the mission's flyby craft. Scattered light from the collision saturated the camera's detector, creating the bright splash seen here. Linear spokes of light radiate away from the impact site, while reflected sunlight illuminates most of the comet surface. The image reveals topographic features, including ridges, scalloped edges and possibly impact craters formed long ago.
This composite image was built up from scaling all images to 5 meters/pixel, and aligning images to fixed points. Each image at closer range, replaced equivalent locations observed at a greater distance. The impact site has the highest resolution because images were acquired until about 4 sec from impact or a few meters from the surface.
Although the entire nucleus was not imaged - the spacecraft flew past and not completely around the comet - enough was seen to give a good idea of the shape. Using data collected from the instruments, co-Investigator Peter Thomas of Cornell University has worked with his team to derive the shape. The MRI imaged about 25% of the nucleus. Discernible features, usually circular ones, that can be recognized in multiple images (red + signs, left frame) are marked as 'control points.' Input to the grid-making program typically uses 189 control points from 70 images. The control points are then pieced together into a shape model consisting of plates that define the three dimensional figure of the nucleus. There are gaps of course, because we didn't see the entire nucleus. The right frame shows the grid representing the shape of the nucleus. From this model we then have some dimensions. The mean radius is 3.0 ± 0.1 km, the longest dimension is 7.5 km and the shortest is 5.0 km. In addition to the shape, Dr. Thomas also derived the orientation of the comet's spin pole, which points to a place in the sky designated at Right Ascension 293.8° and declination 72.6° with an uncertainty of ±5° (these are equivalent to latitude and longitudes on the celestial sphere).
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.
This image from the High-Resolution Instrument on NASA's EPOXI mission spacecraft shows part of the nucleus of comet Hartley 2. The sun is illuminating the nucleus from the right. A distinct cloud of individual particles is visible. This image was obtained on Nov. 4, 2010, the day the EPOXI mission spacecraft made its closest approach to the comet.
After more than a month of communications silence from the Deep Impact spacecraft, NASA on Friday formally declared an end to its nine-year, comet-exploring mission.
The spacecraft made considerable impact in 2005 when it smashed a comet with a projectile to give scientists a peek at the interior. Though it completed its original mission in just six months, Deep Impact went on to rendezvous with two more comets and served as a spaceborne planetary observatory.
"Deep Impact has been a fantastic, long-lasting spacecraft that has produced far more data than we had planned," Mike A'Hearn, the mission's principal investigator at the University of Maryland in College Park, said in a statement. "It has revolutionized our understanding of comets and their activity."
Timothy Larson, the project manager for Deep Impact at Pasadena's Jet Propulsion Laboratory, told KPCC that the mission was a "great example of how NASA gets the most they can out of all of their spacecraft that they send up." He also acknowledged that the decision came as a disappointment for many who worked on the project over the years.
"Some of the folks we've had working with the project have been on it off and on since it launched back in 2005, so people have developed a strong attachment to the spacecraft and what it can do, so everybody's a little sad to see it go," Larson said.
Last month, engineers lost contact with Deep Impact and unsuccessfully tried to regain communications. The cause of the failure was unknown, but NASA suspects the spacecraft lost control, causing its antenna and solar panels to be pointed in the wrong direction.
During the mission, Deep Impact beamed back 500,000 images including of comet Ison, which could shine as bright as the moon when it makes a close approach in November.
This series of images of comet C/2012 S1 (ISON) was taken by the Medium-Resolution Imager of NASA's Deep Impact spacecraft over a 36-hour period on Jan. 17 and 18, 2013. At the time, the spacecraft was 493 million miles (793 million kilometers) from the comet. | Credit: NASA Jet Propulsion Laboratory
The spacecraft also helped scientists gain a better understanding of where comets come from and the stuff they're made of.
"One big finding out of the original impact of comet Tempel 1 is how porous and loosely packed the comet nucleus is. ... It's been likened to the consistency of a pretty dry, fluffy snowbank," Larson said.
Watch an animation of Deep Impact's original mission to study Tempel 1:
This animation chronicles the travels of NASA's Deep Impact spacecraft, from its launch in January of 2005 to its dramatic impact 172 days later with comet Tempel 1. The times were updated on July 2, 2005, and differ from those referred to in the animation. | NASA/JPL-Caltech via ItsARandomChannel on YouTube
Another development: measurements of the amount of carbon dioxide and water on the comets lead some scientists to believe some comets may have formed much closer to the center of the solar system rather than far on the outer reaches, Larson said.
Since there's no way for ground controllers to talk to Deep Impact, the spacecraft will continue on its path around the sun until it runs out of fuel.
And for anyone wondering, the spacecraft's name did not come from the eponymous 1998 film about a comet on a deadly collision course with Earth — it's just a coincidence, Larson said.