[Deep Impact Movie Mp4 Download
Sharif Garmon
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So yesterday, after covering the Deep Impact press conference at JPL and recording for Planetary Radio, my husband and I drove to his parents' house for an Independence Day barbeque. My in-laws asked me about what had been going on this weekend that had kept me working through the holiday. When I explained the nature of the Deep Impact mission my mother-in-law exclaimed, "What! What gives you the right to go around smashing up a comet that was minding its own business?"
I am sure that there are some people reading this who will find her question silly, but I didn't. Behind my mother-in-law's exclamation is a respect and honor for the natural world, rooted deeply in her culture and religion, and a notion that humans should not lightly visit destruction on any part of it. Those are all admirable motives, not to be dismissed. I wish more people had those motives.
What I told my mother-in-law was that, yes, Deep Impact did commit a destructive act. However, although the impact was a violent and energetic one by human standards, it was a weak one by Solar System standards, and, it was not strong enough to affect the course of the comet in any detectable way. Furthermore, I told her, such a mission would not likely have been undertaken on any of the culturally significant, naked-eye comets, like Halley. Tempel 1, though it does have a name, is a tiny comet, one of millions, visible only to select people with strong-enough telescopes. On the other side, the mission provided -- we hope -- a window into the earliest origins of the solar system, and clues to our beginnings.
The analogy I have been using when I talk to people is that the Deep Impact comet crash is very much like a paleoecologist wandering into an ancient forest, selecting one among the many trees in the forest, and using her tiny drill to extract a pencil-wide core from the tree in order to study its rings and understand some things about the history of the Earth's climate. The act is a destructive one -- it drills a hole into a natural object previously undisturbed by humans. But it does not destroy the tree. It does not even significantly impact the health of the tree. Likewise, the Deep Impact mission produced a new hole in a comet in order to see what was inside, but it did not destroy the comet, change its course, or even produce any permanent effect in its outward appearance.
But there is one significant way in which my analogy breaks down. Over the past few decades, tree ring cores have been taken from thousands of trees, producing a huge international database illuminating fine local changes in climate over the past thousands of years. But no one has ever cored a comet before. Tempel 1 was the very first. And that massively increases its cultural significance. Deep Impact possibly gave us the first glimpse humanity has ever had of materials preserved since the very beginnings of our solar system. (I say 'possibly' because after all the science results are not out yet, and the science team has not yet confirmed that they achieved what they hoped for.) Attempting to understand our origins is a powerful motive for study and research, shared across diverse human cultures.
Those of us who were writing about this event for the public tended to focus on the extremes of the event -- the speeds, the power, the technological achievements. In the end, though, the ultimate goals of the mission had to do with understanding our beginnings. I hope that, as the scientific results of the mission come out over the coming weeks and months, the focus will shift from the violence of the event itself to the yield of new understandings of how the Solar System came to be, and what was the nature of the ingredients for the first life on Earth -- the water and organic molecules that were likely contributed to our newborn planet by myriad little comets like Tempel 1.
So, I explained this stuff to my mother-in-law. She thought about it for a minute, then chuckled and said, "All right, I suppose I will let you do this thing!" Which was good, because it had already been done!
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The goals of the Deep Impact mission were to rendezvous with comet 9P/Tempel 1 and launch a projectile into the comet nucleus. Observations were made of the ejecta, much of which represented pristine material from the interior of the comet, the crater formation process, the resulting crater, and outgassing from the nucleus, particularly the newly exposed surface. The scientific objectives of the mission are to: improve the knowledge of the physical characteristics of cometary nuclei and directly assess the interior of cometary nucleus; determine properties of the surface layers such as density, strength, porosity, and composition from the crater and its formation; study the relationship between the surface layers of a cometary nucleus and the possibly pristine materials of the interior by comparison of the interior of the crater with the surface before impact; and improve our understanding of the evolution of cometary nuclei, particularly their approach to dormancy, by comparing the interior and the surface. This project was selected as a Discovery class mission in July, 1999. After the primary mission, Deep Impact was selected for a two-part extended mission designated EPOXI.
The spacecraft consists of a 370 kg cylindrical copper impactor attached to a 650 kg flyby bus. The spacecraft is a box-shaped honeycomb aluminum framework with a flat rectangular Whipple debris shield mounted on one side to protect components during comet close approach. Body mounted on the framework are one high- and one medium-resolution instrument, each of which consists of an imaging camera and an infrared spectrometer which will be used to observe the ejected ice and dust, much of which will be exposed to space for the first time in over 4 billion years. The medium resolution camera has a field of view (FOV) of 0.587 degrees and a resolution of 7 m/pixel at 700 km distance and is used for navigation and context images. The high resolution camera has a FOV of 0.118 degrees and a resolution of 1.4 m/pixel at 700 km. The infrared spectrometers cover the range from 1.05 to 4.8 micrometers with FOV of 0.29 degrees (hi-res) and 1.45 degrees (lo-res). The total flyby bus instrument payload has a mass of 90 kg and will use an average of 92 W during encounter.
The flyby spacecraft measures approximately 3.2 m x 1.7 m x 2.3 m, is three-axis stabilized and uses a blowdown hydrazine primary propulsion system with 5000 N-s RCS total impulse providing a total delta-V of 190 m/s. Communications with the ground from the flyby bus are via X-band (8.000 MHz) through a 1 meter diameter parabolic dish antenna mounted on a 2-axis gimbal or through a fixed low-gain antenna. Communication between the impactor and flyby spacecraft is in S-band. The uplink data rate will be 125 bps, downlink will be at 175 kbps. Power of 620 W at the encounter is provided by a 7.2 square meter solar array and stored in a small NiH2 battery. The spacecraft control system consists of four hemispherical resonator gyros, two star trackers, reaction wheels, and hydrazine thrusters. Pointing accuracy is 200 microradians with 65 microradian knowledge. Thermal control is achieved by insulating blankets, surface radiators, finishes, and heaters. The spacecraft has two redundant RAD750 computers with 309 MB each of memory for scientific data.
The impactor projectile is made of primarily copper (49%) and only 24% aluminum so it will be easily identifiable and minimize contamination in the spectra after the projectile is largely vaporized and mixed in with the comet ejecta on impact. The impactor is a short hexagonal cylinder built above the copper cratering mass. It has a small hydrazine propulsion system for targeting which can provide delta-V of 25 m/s. Targeting is accomplished using a high-precision star-tracker, auto-navigation algorithms, and the Impactor Targeting Sensor (ITS), a camera which provides images for autonomous control and targeting. The ITS will operate until impact, and images will be sent back to Earth via the flyby spacecraft. Damage to the instrument due to dust in the coma may make imaging impossible duing the last minute or so before impact. Communication with the flyby spacecraft is via S-band. The impactor is mechanically and electrically connected to the flyby spacecraft until 24 hours prior to encounter. After separation it runs on internal battery power.
Deep Impact launched on 12 January 2005 at 18:47:08.574 UT (1:47:08 p.m. EST) on a Delta II. The spacecraft transferred into a heliocentric orbit and will rendezvous with comet P/Tempel 1 in July 2005. Deep Impact was 880,000 km from the comet on 3 July 2005 moving at a velocity of 10.2 km/s relative to the comet. The projectile was released at this point and shortly after release the flyby spacecraft executed a maneuver to slow down relative to the impactor by 120 m/s and divert by 6 m/s. On 4 July the impactor struck the sunlit side of the comet nucleus 24 hours after release, at 5:52 UT (1:52 a.m. EDT). At 10.2 km/s velocity, the impactor had an impact energy of about 19 gigajoules, and hit at an oblique angle of approximately 25 degrees. Material from the nucleus was ejected into space and the impactor and much of the ejecta was vaporized.
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