Wednesday, July 06, 2005

Deep Impact

After 172 days and 431 million kilometers (268 million miles) of deep space stalking, Deep Impact successfully reached out and touched comet Tempel 1. The collision between the coffee table-sized impactor and city-sized comet occurred at 1:52 a.m. EDT. (14/7/2005)

Intro:
Comets are time capsules that hold clues about the formation and evolution of the solar system. They are composed of ice, gas and dust, primitive debris from the solar system's distant and coldest regions that formed 4.5 billion years ago. Deep Impact, a NASA Discovery Mission, is the first space mission to probe beneath the surface of a comet and reveal the secrets of its interior.

(artist impression)

The Deep Impact mission lasts six years from start to finish. Planning and design for the mission took place from November 1999 through May 2001. The mission team is proceeding with the building and testing of the two-part spacecraft. The larger "flyby" spacecraft carries a smaller "impactor" spacecraft to Tempel 1 and releases it into the comet's path for a planned collision. The spacecraft will be launched to air space with the help of Boeing Delta II rocket.

On July 4, 2005, the Deep Impact spacecraft arrives at Comet Tempel 1 to impact it with a 370-kg (~820-lbs) mass. On impact, the crater produced is expected to range in size from that of a house to that of a football stadium, and two to fourteen stories deep. Ice and dust debris is ejected from the crater revealing fresh material beneath. Sunlight reflecting off the ejected material provides a dramatic brightening that fades slowly as the debris dissipates into space or falls back onto the comet. Images from cameras and a spectrometer are sent to Earth covering the approach, the impact and its aftermath.








Sixty-nine days before it gets up-close-and-personal with a comet, NASA's Deep Impact spacecraft successfully photographed its quarry, comet Tempel 1, at a distance of 39.7 million miles. The image, taken on April 25, 2005, is the first of many comet portraits Deep Impact will take leading up to its historic comet encounter on July 4.


This image shows comet Tempel 1 as seen through the clear filter of the medium-resolution camera on NASA's Deep Impact spacecraft. It was taken on July 1, 2005, when the spacecraft was 2,446,529.1 kilometers (1,520,273 miles) away from the comet. Five images were combined together, and a logarithmic stretch was applied to enhance the coma of the comet.


This display shows highly processed images of the outburst of comet Tempel 1 between June 22 and 23, 2005. The images were taken by Deep Impact's medium-resolution camera. An average image of the comet has been subtracted from each picture to provide an enhanced view of the outburst. The intensity has also been stretched to show the faintest parts. This processing enables measurement of the outflow speed and the details of the dissipation of the outburst. The left image was taken when the comet was very close to its normal, non-bursting state, so almost nothing is visible.



A picture of Tempel 1(left) taken by Deep Impact's medium-resolution camera is shown next to data of the comet taken by the spacecraft's infrared spectrometer. This instrument breaks apart light like a prism to reveal the "fingerprints," or signatures, of chemicals. Even though the spacecraft was over 10 days away from the comet when these data were acquired, it detected some of the molecules making up the comet's gas and dust envelope, or coma. The signatures of these molecules - including water, hydrocarbons, carbon dioxide and carbon monoxide - can be seen in the graph, or spectrum.



This false-color image shows comet Tempel 1 as seen by Chandra X-ray Observatory on June 30, 2005, Universal Time. The comet was bright and condensed. The X-rays observed from comets are caused by an interaction between highly charged oxygen in the solar wind and neutral gases from the comet. The observatory detected X-rays with an energy of 0.3 to 1.0 kilo electron Volts. The bulk of the X-rays were between 0.5 and 0.7 kilo electron Volts.


This plot consists of data taken by the Deep Impact's medium-resolution instrument before the mission's scheduled collision with comet Tempel 1. It shows the total brightness of the comet versus time until impact. Two outbursts of the comet can be seen as sharp peaks. One occurred three and two-third days before impact, and another just less than two days before. The large-scale, more gradual peaks are due to the rotation of the elongated comet nucleus. One rotation period is 41.85 hours. These data were acquired by the mission's navigation team.



These water maps of Tempel 1 show the location of water molecules around the comet. Each image corresponds to a different time interval - two before a comet outburst (left), one near the peak of an outburst (middle), and one after the outburst (right). The outward motion of the water during the outburst can be seen. This information will be used to understand the process by which outbursts occur.



This image shows comet Tempel 1 approximately 5 minutes before Deep Impact's probe smashed into its surface. It was taken by the probe's impactor targeting sensor. The Sun is to the right of the image and reveals terrain varying in brightness by a factor of two. Shadows and bright areas indicate surface topography. Smooth regions with no features (lower left and upper right) are probably younger than rougher areas with circular features, which are most likely impact craters. The probe crashed between the two dark-rimmed craters near the center and bottom of the comet.


This movie shows Deep Impact's impactor probe approaching comet Tempel 1. It is made up of images taken by the probe's impactor targeting sensor. The probe collided with the comet at 10:52 p.m. Pacific time, July 3 (1:52 a.m. Eastern time, July 4).




This image from NASA TV is a view from Deep Impact's flyby showing the impactor colliding with comet Tempel 1.



This image shows the initial ejecta that resulted when NASA's Deep Impact probe collided with comet Tempel 1 at 10:52 p.m. Pacific time, July 3 (1:52 a.m. Eastern time, July 4). It was taken by the spacecraft's high-resolution camera 13 seconds after impact. The image has been digitally processed to better show the comet's nucleus

Source: NASA