JPL NEWS RELEASE: 2005-107 July 1, 2005 NASA'S Deep Impact Spacecraft Preps for July 4 Fireworks NASA's Deep Impact spacecraft continues to sail through its final checkout, as it hurtles toward comet Tempel 1. Impact with the comet is scheduled for 1:52 a.m. EDT, July 4 (10:52 p.m. PDT, July 3). "The time of comet encounter is near and the major mission milestones are getting closer and closer together," said Rick Grammier, Deep Impact project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "After all the years of design, training and simulations, we are where we want to be. The flight and science teams are working the mission plan, and we are good to go for encounter." Deep Impact consists of a subcompact-car-sized flyby spacecraft and an impactor, about the size of a washing machine. The dual spacecraft carry three imaging instruments, two on the flyby and one on the impactor. Several major mission milestones occurred during the past week. The mission's third trajectory correction maneuver was successfully executed on June 23. The burn of the spacecraft's motors changed Deep Impact's speed by 13 miles per hour. Another trajectory correction for final targeting before impactor release is scheduled for 8:00 p.m. EDT July 2 (5:00 p.m. PDT). Mission planners separated the spacecraft's flight operations into six mission phases. The phases are launch, commissioning, cruise, approach, encounter and playback. The five-day encounter phase incorporates the final approach to the comet and transmission to Earth of collected data. "We've completed the final pre-release checkout of the impactor. The impactor probe will have a short, 24 hour life from release to impact, but an incredibly important role," said Dave Spencer, Deep Impact mission manager at JPL. The impactor has an auto-navigation system that will make final corrections to its flight path just minutes before the scheduled collision. Scientists hope the resulting crater will expose fresh material from below the comet's surface and subsurface. "That is the whole point of Deep Impact," said mission principal investigator and University of Maryland astronomer Dr. Michael A'Hearn. "We want to find out what are the guts of a comet." The flyby spacecraft will use medium and high resolution imagers and an infrared spectrometer to collect and send to Earth pictures and spectra of the event. Spaceborne science platforms will also be watching Deep Impact. These include NASA's Hubble and Spitzer space telescopes, the Chandra X-ray Observatory, the Swift and Submillimeter Wave Astronomy satellites, the European Space Agency's XMM-Newton X-ray observatory and Rosetta spacecraft. Observatories on Earth will view the impact and its aftermath. The final prelude to impact begins early on July 3 EDT (July 2 PDT), when the flyby spacecraft releases the impactor into the path of the onrushing comet. The release is scheduled at 1:52 a.m. EDT, 24 hours before impact (10:52 p.m. PDT). The 820-pound impactor will collide with the comet's nucleus at a closing speed of 37,000 kilometers per hour (23,000 miles per hour). Scientists expect the impact to create a large crater. The impact will eject ice, dust and gas from the crater and reveal the pristine material beneath. The impact will have no significant effect on the comet's orbit, which poses no threat to Earth. The University of Maryland, College Park, conducts overall mission science for Deep Impact. JPL handles project management and mission operations. For information about Deep Impact on the Web, visit: http://www.nasa.gov/deepimpact Watch Deep Impact's Comet Collision Via Webcast By Tariq Malik Staff Writer, Space.com, 1 July 2005 You donıt have to be a scientist to grab a front row seat when the NASAıs Deep Impact spacecraft bears down on a comet between July 3 and 4. Live webcasts of the event will be provided by NASA and several observatories, large and small, to offer skywatchers a digital view to thecometary collision. NASAıs Deep Impact mission is slated to crash an 820-pound (371-kilogram) Impactor probe into Comet Tempel 1 and record the event via a Flyby mothership, orbital observatories like the Hubble and Spitzer space telescope, and a myriad of ground-based telescopes from around the world. The impact is expected to take place at 1:52 a.m. EDT (0552 GMT) on July 4. Hereıs a handy list to track Deep Impactıs progress on the web: NASA has arranged to webcast a series of press briefings leading up to Deep Impactıs crash day, and will provide live mission coverage between July 3 and 4 on NASA TV. The Kitt Peak National Observatory in Tucson, Arizona will provide a live webcast of the collision beginning about an hour before the comet collision. In Bathurst, Australia, astronomers with the Charles Stuart Universityıs Remote Telescope will broadcast live Deep Impact observations from sunset to midnight local time. Atop Hawaiiıs Mauna Kea, the W.M. Keck Observatory will post near-real time images of Deep Impactıs Tempel 1 crash as seen through a Celestron 11-inch CGE telescope. In addition to live webcasts, Deep Impact mission scientists have set up image cache where both professional and amateur astronomers can post their own observations of Comet Tempel 1. Astronomers Ready for Show By Glennda Chui San Jose Mercury News, June 29, 2005 Starting Sunday night, every major telescope on Earth and in space -- and quite a few of the little ones -- will point at one spot in the sky. They'll watch for a flash as an 820-pound projectile smashes into a comet half the size of Manhattan at 23,000 mph. Then they'll look for a growing glow as the comet's guts spill into space. Scientists hope this faraway crash, the climax of NASA's Deep Impact mission, will produce a Roman candle of gas and dust -- our first look at the innards of a comet, the most primitive and pristine stuff in the solar system. Not since 1994, when a string of comet chunks crashed into Jupiter, have astronomers from all over the world been so fixated on a single event. "We've never done this before, so we don't know exactly what will happen," said Richard Puetter, leader of a team that will be watching the impact from Lick Observatory east of San Jose. "Possibly the flash will be bright enough to see by eye." Or maybe not: The probe could sink into the comet and disappear, like a bullet fired into styrofoam. Many experts think it is unlikely that the average person on the ground will see anything, unless they're in a very dark place with a good-size telescope pointed in exactly the right direction. One thing's for sure, scientists said: The impact will not shatter the comet or knock it off course. Since it's 83 million miles away, there's no danger that Comet Tempel 1 will menace the Earth in any way. "This is very much like a mosquito running into an 18-wheeler," said crater expert Peter Schultz of Brown University, one of the mission scientists. Whether Deep Impact ends with a bang or with a whimper, researchers hope it will tell them how comets are put together. Why does it matter? Because comets are leftovers from the birth of the solar system, the most primitive objects known. Scientists think that comets falling into the early Earth contributed critical materials, from carbon-based compounds to water, that helped create conditions conducive to life. "They represent the raw junk out of which everything was made, way back when," said Scott Sandford of NASA's Ames Research Center in Mountain View. From that standpoint, he said, comets are more interesting than planets. Comets are mixtures of ice, dust and rock. Each time they loop around the sun, some of the ice melts, releasing gas and dust that glow in reflected sunlight and form the comet's tail. Over time, the surface of the comet turns dark, like chicken left too long on the barbecue. But scientists don't know whether this surface is soft and fluffy or hard and crusty. They would like to figure this out; in the extremely unlikely event that a comet veered toward Earth, it would help them decide whether to try to deflect it or blow it up. "What we want to do is blast into the comet and knock out some of the material from the inside, which is pristine," said Puetter, an astrophysicist from the University of California-San Diego. "If it's really fluffy, like snow, then the impact will bury itself deep in the comet, and all the energy will get deposited deep in the comet and we won't see anything," he said. "On the other hand, if it's really hard, all the energy will deposit on the surface of the comet, and it will blow off a crater." Simulations show the crater could be as big as 650 feet wide and 150 feet deep and leak gas, dust, ice and rock for a long time to come. Deep Impact was launched Jan. 12 from Cape Canaveral. On Saturday the spacecraft is scheduled to release a probe the size of a washing machine into the path of the comet, then maneuver into a safe position to watch what happens. The impact, which was timed to occur on the East Coast on the Fourth of July, will take place about 10:52 p.m. PDT. The first signals from the spacecraft, which will hover nearby to take pictures and data, should arrive on Earth seven minutes and 26 seconds later. Steven Chesley, an astronomer at NASA's Jet Propulsion Laboratory in Pasadena, has been continually recalculating the path of the comet, which can change as plumes of gas burst from its surface, nudging it like so many little rocket engines. "Right now it looks like we'll be able to forecast the time of impact within about 30 seconds," he said. Today will be his last chance to make corrections in the comet's course. But Chesley said he isn't worried about the probe hitting its target, because it has a camera and can steer in the right direction, "like driving a car." At least nine other spacecraft, including the Hubble Space Telescope, will be monitoring the impact, including one brought out of hibernation for the occasion. The crash will be visible only from the West Coast and Hawaii. But astronomers throughout the world will be ready to observe the aftermath as the globe turns and the comet rolls into view. They will be connected to an extraordinary degree by daily video conferences, a teleconference line and a Web site where observers will immediately post information, said astronomer Karen Meech of the University of Hawaii-Manoa, who will coordinate the network from the summit of Mauna Kea. "I would be very surprised if there was any place on Earth that wasn't observing," she said. "I think a lot of the interesting science is going to develop in the two or three days following the impact," with scientists analyzing the composition of the gases and dust leaking from the wounded comet. Puetter's team will watch from Lick Observatory on Mount Hamilton. They will use the biggest telescope on the mountain, the three-meter Shane, as well as a smaller, 40-inch scope. Diane Wooden, an astrophysicist at NASA/Ames, will watch from a telescope on 14,000-foot Mauna Kea, bundled in wool against the cold. "It's definitely not a comfortable environment," she said. "But I find one of the most exciting aspects is to go up there and look, and all these telescopes have their domes open, their mouths open to the universe." Deep Impact Spacecraft Observes Massive Comet Outburst By SPACE.com Staff, 28 June 2005 NASA's Deep Impact spacecraft has observed a massive, short-lived outburst of ice or other particles from comet Tempel 1 just days before the craft will release a probe to slam into the comet. The outburst, which occurred June 22 and was announced today, was larger than one photographed recently by the Hubble Space Telescope. The latest eruption temporarily expanded the size and reflectivity of the cloud of dust and gas, called a coma, that surrounds the comet nucleus. "This most recent outburst was six times larger than the one observed on June 14, but the ejected material dissipated almost entirely within about a half day," said University of Maryland astronomer Michael A'Hearn, who leads the Deep Impact mission. The Deep Impact mission is designed to carve a crater in the comet, releasing primordial material for study in an effort to learn specifically what comets are made of. The spacecraft's instruments found that during the June 22 outburst, the amount of water vapor in the coma doubled, while the amount of other gases, including carbon dioxide, increased even more. "Outbursts such as this may be a very common phenomenon on many comets, but they are rarely observed in sufficient detail to understand them because it is normally so difficult to obtain enough time on telescopes to discover such phenomena," A'Hearn said. "We likely would have missed this exciting event, except that we are now getting almost continuous coverage of the comet with the spacecraft's imaging and spectroscopy instruments." Two eruptions in as many weeks suggests the activity is common. Deep Impact co-investigator Jessica Sunshine, with Science Applications International Corporation (SAIC), agreed that observing such activity twice in one week suggests outbursts are fairly common. "We must now consider them as a significant part of the processing that occurs on comets as they heat up when approaching the Sun," said Deep Impact co-investigator Jessica Sunshine, with Science Applications International Corporation. The latest event was observed with the spacecraft's spectrometer, which splits light into its constituent parts for chemical analysis. "The spectrometer is working very well and we already are able to see changes in the makeup of the fresh material extruded from the comet," Sunshine said. "We are still a long way from the comet, so this bodes very well for our ability to observe and characterize changes in the comet's materials, before, during, and after our impact." Eruptions like this are believed to be associated with the heating of comet material by the Sun. Comet Tempel 1 is near perihelion, or the point in its orbit at which it is closest to the Sun. "For the June 22 event, it is the rapid dispersal of this outburst that raises the most questions," said A'Hearn. "It looks as though the puff was nearly instantaneous and that simple radial expansion is not enough to make the brightness go down as fast as it did. Thus the particles must also either be vaporizing, and thus disappearing, or getting much darker after release, and 'disappearing' in that way." "This adds to the level of excitement as we come down to the final days before encounter," said Rick Grammier, Deep Impact project manager at NASA's Jet Propulsion Lab in Pasadena, Calif. "But this comet outburst will require no modification to mission plan and in no way affects spacecraft safety." NASA News Release: 2005-098 June 9, 2005 NASA Announces Spectacular Day of the Comet After a voyage of 173 days and 431 million kilometers, NASA's Deep Impact spacecraft will get up-close and personal with comet Tempel 1 on July 4 (EDT). The first of its kind, hyper-speed impact between space-borne iceberg and copper-fortified probe is scheduled for approximately 1:52 a.m. EDT on Independence Day (10:52 p.m. PDT on July 3). The potentially spectacular collision will be observed by the Deep Impact spacecraft, and ground and space-based observatories. "We are really threading the needle with this one," said Rick Grammier, Deep Impact project manager at NASAıs Jet Propulsion Laboratory, Pasadena, Calif. "In our quest of a great scientific payoff, we are attempting something never done before at speeds and distances that are truly out of this world." During the early morning hours of July 3 (EDT), the Deep Impact spacecraft will deploy a 1-meter-wide impactor into the path of the comet, which is about half the size of Manhattan Island, N.Y. Over the next 22 hours, Deep Impact navigators and mission members located more than 133 million kilometers away at JPL, will steer both spacecraft and impactor toward the comet. The impactor will head into the comet and the flyby craft will pass approximately 500 kilometers below. Tempel 1 is hurtling through space at approximately 37,100 kilometers per hour. At that speed you could travel from New York to Los Angeles in less than 6.5 minutes. Two hours before impact, when mission events will be happening so fast and so far away, the impactor will kick into autonomous navigation mode. It must perform its own navigational solutions and thruster firings to make contact with the comet. "The autonav is like having a little astronaut on board," Grammier said. "It has to navigate and fire thrusters three times to steer the wine cask-sized impactor into the mountain-sized comet nucleus closing at 23,000 miles per hour." The crater produced by the impact could range in size from a large house up to a football stadium, and from two to 14 stories deep. Ice and dust debris will be ejected from the crater, revealing the material beneath. The flyby spacecraft has approximately 13 minutes to take images and spectra of the collision and its result before it must endure a potential blizzard of particles from the nucleus of the comet. "The last 24 hours of the impactor's life should provide the most spectacular data in the history of cometary science," said Deep Impact Principal Investigator Dr. Michael A'Hearn of the University of Maryland, College Park. "With the information we receive after the impact, it will be a whole new ballgame. We know so little about the structure of cometary nuclei that almost every moment we expect to learn something new." The Deep Impact spacecraft has four data collectors to observe the effects of the collision. A camera and infrared spectrometer, which comprise the High Resolution Instrument, are carried on the flyby spacecraft, along with a Medium Resolution Instrument. A duplicate of the Medium Resolution Instrument on the impactor will record the vehicle's final moments before it is run over by Tempel 1. "In the world of science, this is the astronomical equivalent of a 767 airliner running into a mosquito," said Dr. Don Yeomans, a Deep Impact mission scientist at JPL. "The impact simply will not appreciably modify the comet's orbital path. Comet Tempel 1 poses no threat to the Earth now or in the foreseeable future." Deep Impact will provide a glimpse beneath the surface of a comet, where material from the solar system's formation remains relatively unchanged. Mission scientists expect the project will answer basic questions about the formation of the solar system, by offering a better look at the nature and composition of the frozen celestial travelers we call comets. The University of Maryland is responsible for overall Deep Impact mission management, and project management is handled by JPL. The spacecraft was built for NASA by Ball Aerospace & Technologies Corporation, Boulder, Colo. For more information about Deep Impact on the Internet, visit: http://www.nasa.gov/deepimpact. |
