Nasa Technology News

NASA's Mars Science Laboratory rover, Curiosity, will carry a next generation, onboard "chemical element reader" to measure the chemical ingredients in Martian rocks and soil. The instrument is one of 10 that will help the rover in its upcoming mission to determine the past and present habitability of a specific area on the Red Planet. Launch is scheduled between Nov. 25 and Dec. 18, 2011, with landing in August 2012.

The Alpha Particle X-Ray Spectrometer (APXS) instrument, designed by physics professor Ralf Gellert of the University of Guelph in Ontario, Canada, uses the power of alpha particles, or helium nuclei, and X-rays to bombard a target, causing the target to give off its own characteristic alpha particles and X-ray radiation. This radiation is "read by" an X-ray detector inside the sensor head, which reveals which elements and how much of each are in the rock or soil.

Identifying the elemental composition of lighter elements such as sodium, magnesium or aluminum, as well as heavier elements like iron, nickel or zinc, will help scientists identify the building blocks of the Martian crust. By comparing these findings with those of previous Mars rover findings, scientists can determine if any weathering has taken place since the rock formed ages ago.

All NASA Mars rovers have carried a similar instrument – Pathfinder's rover Sojourner, Spirit and Opportunity, and now Curiosity, too. Improvements have been made with each generation, but the basic design of the instrument has remained the same.

"APXS was modified for Mars Science Laboratory to be faster so it could make quicker measurements. On the Mars Exploration Rovers [Spirit and Opportunity] it took us five to 10 hours to get information that we will now collect in two to three hours," said Gellert, the instrument's principal investigator. "We hope this will help us to investigate more samples."

Another significant change to the next-generation APXS is the cooling system on the X-ray detector chip. The instruments used on Spirit and Opportunity were able to take measurements only at night. But the new cooling system will allow the instrument on Curiosity to take measurements during the day, too.

The main electronics portion of the tissue-box-sized instrument lives in the rover's body, while the sensor head, the size of a soft drink can, is mounted on the robotic arm. With the help of Curiosity's remote sensing instruments – the Chemistry and Camera (ChemCam) instrument and the Mastcam – the rover team will decide where to drive Curiosity for a closer look with the instruments, including APXS. Measurements are taken with the APXS by deploying the sensor head to make direct contact with the desired sample.

The rover's brush will be used to remove dust from rocks to prepare them for inspection by APXS and by MAHLI, the rover's arm-mounted, close-up camera. Whenever promising samples are found, the rover will then use its drill to extract a few grains and feed them into the rover's analytical instruments, SAM and CheMin, which will then make very detailed mineralogical and other investigations.

Scientists will use information from APXS and the other instruments to find the interesting spots and to figure out the present and past environmental conditions that are preserved in the rocks and soils.

"The rovers have answered a lot of questions, but they've also opened up new questions," said Gellert. "Curiosity was designed to pick up where Spirit and Opportunity left off."

For more information about the mission, visit http://mars.jpl.nasa.gov/msl/ . To watch the spacecraft being assembled and tested, visit http://www.ustream.tv/nasajpl .

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory mission for the NASA Science Mission Directorate, Washington.

The MSL APXS is funded by the Canadian Space Agency, with MDA Corporation as prime subcontractor to build the instrument. Funding for the science team comes from CSA, NASA, and the University of Guelph.

We are the Agency’s one and only entity responsible for working with all 10 NASA Centers, including JPL, to capture, process, disseminate (yes, to the widest practicable audience), store, and safeguard for the future, the published research results from all of the unclassified NASA and NASA-funded research, to include NASA Contractor and Grantee research.

We refer to these published results as scientific and technical information (STI). We have a lot (and I mean a lot) of hard copy documents in our warehouse in Hanover, Maryland, our primary facility, and we are working hard to digitize this “corporate memory” of NASA’s research results. This is our contractor-run facility that we call CASI. (No, it’s not a girl; it’s the Center for AeroSpace Information).

We have a database that CASI runs for NASA that contains the published research results described above, in digital format, searchable through an easy-to-use interface. We have a primary internal database called the NASA Aeronautics and Space Database (NA&SD) (registered access only) and a public database called the NASA Technical Report Server (NTRS). Check them out.

We make sure that the information in this database is protected and archived. In fact, we have a Disaster Recovery (DR) system for this information, and we can deploy it in the event that our primary database is down.

You can follow us on Facebook, Twitter, and we also have some awesome videos on You Tube that provide lots of useful information on using the database described above. Check the links below. They're pretty cool.

And now some statistics for those of you who love that kind of stuff (and you know who you are): We have 4.5 million metadata citations and 432,000 full text documents. The estimated value of the content of the STI database at CASI is conservatively valued at $16B. We have published research results that date back to the first National Advisory Committee for Aeronautics (NACA) annual report (NACA-AR-1) which recapped the activities of NASA's predecessor organization's inaugural year–1915. Really. See it for yourself.

Why It Is Important: Because we, in STIPO, make this important information available to both the Agency and the public (no one else has the full collection). In a paragraph above, I refer to STIPO as being “…the Agency’s one and only…” and that is why what we do is so important. We are doing this for all of NASA (and the public benefit as well). As President Obama said on January 21, 2009, “Information maintained by the Federal Government is a national asset.” You may want to visit this National Asset.

In early January, 2010, the Wide-field Infrared Survey Explorer (WISE) began imaging the entire sky with sensitivities in the mid-Infrared hundreds of times greater than previous surveys. WISE recently completed its first full survey of the sky.

Although WISE itself is an astrophysics mission, NASA's Planetary Science Mission Directorate has funded an enhancement to the WISE project, called "NEOWISE", which is dedicated to discovering and archiving moving objects.

Infrared observations are sensitive to the low albedo objects that are usually missed by optical surveys, and by the end of the mission, NEOWISE is expected to observe ~500 Near-Earth Objects, over 150,000 Main Belt Asteroids, ~100 comets, and ~1500 Trojan asteroids - a vast catalog of information on small bodies in our Solar System that will leave a legacy for decades to come.

In November 2010, the scientific journal Icarus published a paper by astrophysicists John Matese and Daniel Whitmire, who proposed the existence of a binary companion to our sun, larger than Jupiter, in the long-hypothesized "Oort cloud" -- a faraway repository of small icy bodies at the edge of our solar system. The researchers use the name "Tyche" for the hypothetical planet. Their paper argues that evidence for the planet would have been recorded by the Wide-field Infrared Survey Explorer (WISE).

WISE is a NASA mission, launched in December 2009, which scanned the entire celestial sky at four infrared wavelengths about 1.5 times. It captured more than 2.7 million images of objects in space, ranging from faraway galaxies to asteroids and comets relatively close to Earth.

Recently, WISE completed an extended mission, allowing it to finish a complete scan of the asteroid belt, and two complete scans of the more distant universe, in two infrared bands. So far, the mission's discoveries of previously unknown objects include an ultra-cold star or brown dwarf, 20 comets, 134 near-Earth objects (NEOs), and more than 33,000 asteroids in the main belt between Mars and Jupiter.

Following its successful survey, WISE was put into hibernation in February 2011. Analysis of WISE data continues. A preliminary public release of the first 14 weeks of data is planned for April 2011, and the final release of the full survey is planned for March 2012.

Frequently Asked Questions

Q: When could data from WISE confirm or rule out the existence of the hypothesized planet Tyche?

A: It is too early to know whether WISE data confirms or rules out a large object in the Oort cloud. Analysis over the next couple of years will be needed to determine if WISE has actually detected such a world or not. The first 14 weeks of data, being released in April 2011, are unlikely to be sufficient. The full survey, scheduled for release in March 2012, should provide greater insight. Once the WISE data are fully processed, released and analyzed, the Tyche hypothesis that Matese and Whitmire propose will be tested.

Q: Is it a certainty that WISE would have observed such a planet if it exists?

A: It is likely but not a foregone conclusion that WISE could confirm whether or not Tyche exists. Since WISE surveyed the whole sky once, then covered the entire sky again in two of its infrared bands six months later, WISE would see a change in the apparent position of a large planet body in the Oort cloud over the six-month period. The two bands used in the second sky coverage were designed to identify very small, cold stars (or brown dwarfs) -- which are much like planets larger than Jupiter, as Tyche is hypothesized to be.

Q: If Tyche does exist, why would it have taken so long to find another planet in our solar system?

A: Tyche would be too cold and faint for a visible light telescope to identify. Sensitive infrared telescopes could pick up the glow from such an object, if they looked in the right direction. WISE is a sensitive infrared telescope that looks in all directions.

Q: Why is the hypothesized object dubbed "Tyche," and why choose a Greek name when the names of other planets derive from Roman mythology?

A: In the 1980s, a different companion to the sun was hypothesized. That object, named for the Greek goddess "Nemesis," was proposed to explain periodic mass extinctions on the Earth. Nemesis would have followed a highly elliptical orbit, perturbing comets in the Oort Cloud roughly every 26 million years and sending a shower of comets toward the inner solar system. Some of these comets would have slammed into Earth, causing catastrophic results to life.

Recent scientific analysis no longer supports the idea that extinctions on Earth happen at regular, repeating intervals. Thus, the Nemesis hypothesis is no longer needed. However, it is still possible that the sun could have a distant, unseen companion in a more circular orbit with a period of a few million years -- one that would not cause devastating effects to terrestrial life. To distinguish this object from the malevolent "Nemesis," astronomers chose the name of Nemesis's benevolent sister in Greek mythology, "Tyche."

JPL manages and operates the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md.

The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. More information is online at http://www.nasa.gov/wise, http://wise.astro.ucla.edu and http://www.jpl.nasa.gov/wise .

NASA's Mars Science Laboratory rover, Curiosity, will carry a next generation, onboard "chemical element reader" to measure the chemical ingredients in Martian rocks and soil. The instrument is one of 10 that will help the rover in its upcoming mission to determine the past and present habitability of a specific area on the Red Planet. Launch is scheduled between Nov. 25 and Dec. 18, 2011, with landing in August 2012.

The Alpha Particle X-Ray Spectrometer (APXS) instrument, designed by physics professor Ralf Gellert of the University of Guelph in Ontario, Canada, uses the power of alpha particles, or helium nuclei, and X-rays to bombard a target, causing the target to give off its own characteristic alpha particles and X-ray radiation. This radiation is "read by" an X-ray detector inside the sensor head, which reveals which elements and how much of each are in the rock or soil.

Identifying the elemental composition of lighter elements such as sodium, magnesium or aluminum, as well as heavier elements like iron, nickel or zinc, will help scientists identify the building blocks of the Martian crust. By comparing these findings with those of previous Mars rover findings, scientists can determine if any weathering has taken place since the rock formed ages ago.

All NASA Mars rovers have carried a similar instrument – Pathfinder's rover Sojourner, Spirit and Opportunity, and now Curiosity, too. Improvements have been made with each generation, but the basic design of the instrument has remained the same.

"APXS was modified for Mars Science Laboratory to be faster so it could make quicker measurements. On the Mars Exploration Rovers [Spirit and Opportunity] it took us five to 10 hours to get information that we will now collect in two to three hours," said Gellert, the instrument's principal investigator. "We hope this will help us to investigate more samples."

Another significant change to the next-generation APXS is the cooling system on the X-ray detector chip. The instruments used on Spirit and Opportunity were able to take measurements only at night. But the new cooling system will allow the instrument on Curiosity to take measurements during the day, too.

The main electronics portion of the tissue-box-sized instrument lives in the rover's body, while the sensor head, the size of a soft drink can, is mounted on the robotic arm. With the help of Curiosity's remote sensing instruments – the Chemistry and Camera (ChemCam) instrument and the Mastcam – the rover team will decide where to drive Curiosity for a closer look with the instruments, including APXS. Measurements are taken with the APXS by deploying the sensor head to make direct contact with the desired sample.

The rover's brush will be used to remove dust from rocks to prepare them for inspection by APXS and by MAHLI, the rover's arm-mounted, close-up camera. Whenever promising samples are found, the rover will then use its drill to extract a few grains and feed them into the rover's analytical instruments, SAM and CheMin, which will then make very detailed mineralogical and other investigations.

Scientists will use information from APXS and the other instruments to find the interesting spots and to figure out the present and past environmental conditions that are preserved in the rocks and soils.

"The rovers have answered a lot of questions, but they've also opened up new questions," said Gellert. "Curiosity was designed to pick up where Spirit and Opportunity left off."

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory mission for the NASA Science Mission Directorate, Washington.

For more information about the mission, visit http://mars.jpl.nasa.gov/msl/ . To watch the spacecraft being assembled and tested, visit http://www.ustream.tv/nasajpl .

NASA's Stardust spacecraft returned new images of a comet showing a scar resulting from the 2005 Deep Impact mission. The images also showed the comet has a fragile and weak nucleus.

The spacecraft made its closest approach to comet Tempel 1 on Monday, Feb. 14, at 8:40 p.m. PST (11:40 p.m. EST) at a distance of approximately 178 kilometers (111 miles). Stardust took 72 high-resolution images of the comet. It also accumulated 468 kilobytes of data about the dust in its coma, the cloud that is a comet's atmosphere. The craft is on its second mission of exploration called Stardust-NExT, having completed its prime mission collecting cometary particles and returning them to Earth in 2006.

The Stardust-NExT mission met its goals, which included observing surface features that changed in areas previously seen during the 2005 Deep Impact mission; imaging new terrain; and viewing the crater generated when the 2005 mission propelled an impactor at the comet.

"This mission is 100 percent successful," said Joe Veverka, Stardust-NExT principal investigator of Cornell University, Ithaca, N.Y. "We saw a lot of new things that we didn't expect, and we'll be working hard to figure out what Tempel 1 is trying to tell us."

Several of the images provide tantalizing clues to the result of the Deep Impact mission's collision with Tempel 1.

"We see a crater with a small mound in the center, and it appears that some of the ejecta went up and came right back down," said Pete Schultz of Brown University, Providence, R.I. "This tells us this cometary nucleus is fragile and weak based on how subdued the crater is we see today."

Engineering telemetry downlinked after closest approach indicates the spacecraft flew through waves of disintegrating cometary particles, including a dozen impacts that penetrated more than one layer of its protective shielding.

"The data indicate Stardust went through something similar to a B-17 bomber flying through flak in World War II," said Don Brownlee, Stardust-NExT co-investigator from the University of Washington in Seattle. "Instead of having a little stream of uniform particles coming out, they apparently came out in chunks and crumbled."

While the Valentine's Day night encounter of Tempel 1 is complete, the spacecraft will continue to look at its latest cometary obsession from afar.

"This spacecraft has logged over 3.5 billion miles since launch, and while its last close encounter is complete, its mission of discovery is not," said Tim Larson, Stardust-NExT project manager at JPL. "We'll continue imaging the comet as long as the science team can gain useful information, and then Stardust will get its well-deserved rest."

Stardust-NExT is a low-cost mission that is expanding the investigation of comet Tempel 1 initiated by the Deep Impact spacecraft. The mission is managed by JPL for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems in Denver built the spacecraft and manages day-to-day mission operations.

The latest Stardust-Next/Tempel 1 images are online at: http://www.nasa.gov/mission_pages/stardust/multimedia/gallery-index.html

Mission controllers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., have begun receiving the first of 72 anticipated images of comet Tempel 1 taken by NASA's Stardust spacecraft.

The first six, most distant approach images are available at http://www.nasa.gov/stardust and http://www.jpl.nasa.gov. Additional images, including those from closest approach, are being downlinked in chronological order and will be available later in the day.

A news conference will be held at 12:30 p.m. PST (3:30 p.m. EST) to allow scientists more time to analyze the data and images.

Stardust-NExT is a low-cost mission that expands on the investigation of comet Tempel 1 initiated by NASA's Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, manages Stardust-NExT for NASA's Science Mission Directorate, Washington, D.C. Joe Veverka of Cornell University, Ithaca, N.Y., is the mission's principal investigator. Lockheed Martin Space Systems, Denver, built the spacecraft and manages day-to-day mission operations.

Stars at all stages of development, from dusty little tots to young adults, are on display in a new image from NASA's Spitzer Space Telescope.

This cosmic community is called the North American nebula. In visible light, the region resembles the North American continent, with the most striking resemblance being the Gulf of Mexico. But in Spitzer's infrared view, the continent disappears. Instead, a swirling landscape of dust and young stars comes into view.

"One of the things that makes me so excited about this image is how different it is from the visible image, and how much more we can see in the infrared than in the visible," said Luisa Rebull of NASA's Spitzer Science Center at the California Institute of Technology, Pasadena, Calif. Rebull is lead author of a paper about the observations, accepted for publication in the Astrophysical Journal Supplement Series. "The Spitzer image reveals a wealth of detail about the dust and the young stars here."

The new image is online at http://www.nasa.gov/mission_pages/spitzer/multimedia/pia13844.html .

Rebull and her team have identified more than 2,000 new, candidate young stars in the region. There were only about 200 known before. Because young stars grow up surrounded by blankets of dust, they are hidden in visible-light images. Spitzer's infrared detectors pick up the glow of the dusty, buried stars.

A star is born inside a collapsing ball of gas and dust. As the material collapses inward, it flattens out into a disk that spins around together with the forming star like a spinning top. Jets of gas shoot perpendicularly away from the disk, above and below it. As the star ages, planets are thought to form out of the disk -- material clumps together, ultimately growing into mature planets. Eventually, most of the dust dissipates, aside from a tenuous ring similar to the one in our solar system, referred to as Zodiacal dust.

The new Spitzer image reveals all the stages of a star's young life, from the early years when it is swaddled in dust to early adulthood, when it has become a young parent to a family of developing planets. Sprightly "toddler" stars with jets can also be identified in Spitzer's view.

"This is a really busy area to image, with stars everywhere, from the North American complex itself, as well as in front of and behind the region," said Rebull. "We refer to the stars that are not associated with the region as contamination. With Spitzer, we can easily sort this contamination out and clearly distinguish between the young stars in the complex and the older ones that are unrelated."

The North American nebula still has a mystery surrounding it, involving its power source. Nobody has been able to identify the group of massive stars that is thought to be dominating the nebula. The Spitzer image, like images from other telescopes, hints that the missing stars are lurking behind the Gulf of Mexico portion of the nebula. This is evident from the illumination pattern of the nebula, especially when viewed with the detector on Spitzer that picks up 24-micron infrared light. That light appears to be coming from behind the Gulf of Mexico's dark tangle of clouds, in the same way that sunlight creeps out from behind a rain cloud.

The nebula's distance from Earth is also a mystery. Current estimates put it at about 1,800 light-years from Earth. Spitzer will refine this number by finding more stellar members of the North American complex.

The Spitzer observations were made before it ran out of the liquid coolant needed to chill its longer-wavelength instruments. Currently, Spitzer's two shortest-wavelength channels (3.6 and 4.5 microns) are still working. The composite image shows light from both the infrared array camera and multiband imaging processor. Infrared light with a wavelength of 3.6 microns is color-coded blue; 8.0-micron light is green; and 24-micron light is red.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer .

Mission controllers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., watched as data downlinked from the Stardust spacecraft indicated it completed its closest approach with comet Tempel 1. An hour after closest approach, the spacecraft turned to point its large, high-gain antenna at Earth. It is expected that images of the comet's nucleus collected during the flyby will be received on Earth starting at about midnight California time (3 a.m. EST on Tuesday, Feb. 15).

Preliminary data already transmitted from the spacecraft indicate the time of closest approach was about 8:39 p.m. PST (11:39 p.m. EST), at a distance of 181 kilometers (112 miles) from Tempel 1.

This is a bonus mission for the comet chaser, which previously flew past comet Wild 2 and returned samples from its coma to Earth. During this bonus encounter, the plan called for the spacecraft to take images of the comet's surface to observe what changes occurred since a NASA spacecraft last visited. (NASA's Deep Impact spacecraft executed an encounter with Tempel 1 in July 2005).

Stardust-NExT is a low-cost mission that will expand the investigation of comet Tempel 1 initiated by NASA's Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, manages Stardust-NExT for NASA's Science Mission Directorate, Washington, D.C. Lockheed Martin Space Systems, Denver, built the spacecraft and manages day-to-day mission operations.

A bonus round is something one usually associates with the likes of a TV game show, not a pioneering deep space mission.

"We are definitely in the bonus round," said Stardust-NExT Project Manager Tim Larson of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This spacecraft has already flown by an asteroid and a comet, returned comet dust samples to Earth, and now has almost doubled its originally planned mission life. Now it is poised to perform one more comet flyby."

A Successful Prime Mission

NASA's Stardust spacecraft was launched on Feb. 7, 1999, on a mission that would explore a comet as no previous mission had. Before Stardust, seven spacecraft from NASA, Russia, Japan and the European Space Agency had visited comets – they had flight profiles that allowed them to perform brief encounters, collecting data and sometimes images of the nuclei during the flyby.

Like those comet hunters before it, Stardust was tasked to pass closely by a comet, collecting data and snapping images. It also had the ability to come home again, carrying with it an out-of -this-world gift for cometary scientists – particles of the comet itself. Along the way, the telephone booth-sized comet hunter racked up numerous milestones and more than a few "space firsts."

In the first round of its prime mission, Stardust performed observations of asteroid Annefrank, only the sixth asteroid in history to be imaged close up. After that, Stardust racked up more points of space exploration firsts. It became the first spacecraft to capture particles of interstellar dust for Earth return. It was first to fly past a comet and collect data and particles of comet dust (hurtling past it at almost four miles per second) for later analysis. Then, it was first to make the trip back to Earth after traveling beyond the orbit of Mars (a two-year trip of 1.2 billion kilometers, or 752 million miles). When Stardust dropped off its sample return capsule from comet Wild 2, the capsule became the fastest human-made object to enter Earth's atmosphere. The mission was also the first to provide a capsule containing cometary dust specimens, speciments that will have scientists uncovering secrets of comets for years to come.

With such a high tally of "firsts" on its scoreboard, you'd think Stardust could receive a few parting gifts and leave the game. And an important part of the original spacecraft is currently enjoying retirement – albeit a high-profile one: Stardust's 100-pound sample return capsule is on display in the main hall (Milestones of Flight) of the Smithsonian's National Air and Space Museum in Washington. But the rest of NASA's most-seasoned comet hunter is still up there – and there is work still to be done.

"We placed Stardust in a parking orbit that would carry it back by Earth in a couple of years, and then asked the science community for proposals on what could be done with a spacecraft that had a lot of zeros on its odometer, but also had some fuel and good miles left in it," said Jim Green, director of NASA's Planetary Science Division.

Moving into the Bonus Round

In January 2007, from a stack of proposals with intriguing ideas, NASA chose Stardust-NExT (Stardust's Next Exploration of Tempel). It was a plan to revisit comet Tempel 1 at a tenth of the cost of a new, from-the-ground-up mission. Comet Tempel 1 was of particular interest to NASA. It had been the target of a previous NASA spacecraft visit in July 2005. That mission, Deep Impact, placed a copper-infused, 800-pound impactor on a collision course with the comet and observed the results from the cosmic fender-bender via the telescopic cameras onboard the larger part of Deep Impact, a "flyby" spacecraft observing from a safe distance.

"The plan for our encounter is to be more hospitable to comet Tempel 1 than our predecessor," said Joe Veverka, principal investigator of Stardust-NExT from Cornell University in Ithaca, N.Y. "We will come within about 200 kilometers [124 miles] of Tempel 1 and view the changes that took place over the past five-and-a-half years."

That period of time is significant for Tempel 1 -- it is the period of time it takes the comet to orbit the sun once. Not much happens during a comet's transit through the chilly reaches of the outer solar system. But when it nears perihelion (the point in its orbit that an object, such as a planet or a comet, is closest to the sun), things begin to sizzle.

"Comets can be very spectacular when they come close to the sun, but we still don't understand them as well as we should," said Veverka. "They are also messengers from the past. They tell us how the solar system was formed long ago, and Stardust-NExT will help us understand how much they have changed since their formation."

So the spacecraft that had traveled farther afield than any of its predecessors was being sent out again in the name of scientific opportunity. In between spacecraft and comet lay four-and-a-half years, over a billion kilometers (646 million miles), and more than a few hurdles along the way.


Your Mileage May Vary

"One of the challenges with reusing a spacecraft designed for a different prime mission is you don't get to start out with a full tank of gas," said Larson. "Just about every deep-space exploration spacecraft has a fuel supply customized to get the job done, with some held in reserve for contingency maneuvers and other uncertainties. Fortunately, the Stardust mission navigation team did a great job, the spacecraft operated extremely well, and there was an adequate amount of contingency fuel aboard after its prime mission to make this new comet flyby possible – but just barely."

Just how much fuel is in Stardust's tanks for its final act?

"We estimate we have a little under three percent of the fuel the mission launched with," said Larson. "It is an estimate, because no one has invented an entirely reliable fuel gauge for spacecraft. There are some excellent techniques with which we have made these estimates, but they are still estimates."

One of the ways mission planners can approximate fuel usage is to look at the history of the vehicle's flight and how many times and for how long its rocket motors have fired. When that was done for Stardust, the team found their spacecraft's attitude and translational thrusters had fired almost half-a-million times each over the past 12 years.

"There is always a little plus and minus with each burn. When you add them all up, that is how you get the range of possible answers on how much fuel was used," said Larson.

Fuel is not the only question that needs to be addressed on the way to a second comet encounter. Added into the mix is the fact a comet near the sun can fire off jets of gas and dust that can cause a change in its orbit, sometimes in unexpected ways, potentially causing a precisely designed cometary approach to become less precise. Then there are the distances involved. Stardust will fly past comet Tempel 1 on almost the opposite side of the sun from Earth, making deep-space communication truly, well, deep space. Add into the mix the Stardust spacecraft itself. Launched when Bill Clinton was in the White House, Stardust has been cooked and frozen countless times during its trips from the inner to outer solar system. It has also weathered its fair share of radiation-packed solar storms. But while its fuel tank may be running near-empty, that doesn't mean Stardust doesn't have anything left in the tank.

"All this mission's challenges are just that – challenges," said Larson. "We believe our team and our spacecraft are up to meeting every one of them, and we're looking forward to seeing what Tempel 1 looks like these days."

The Final Payoff

Larson, Veverka and the world will get their chance beginning a few hours after the encounter on Monday, Feb. 14, at about 8:56 p.m. PST (11:56 p.m. EST), when the first of 72 bonus-round images of the nucleus of comet Tempel 1 are downlinked.

All images of the comet will be taken by the spacecraft's navigation camera – an amalgam of spare flight-ready hardware left over from previous NASA missions: Voyager (launched in 1977), Galileo (launched in 1989), and Cassini (launched in 1997). Each image will take about 15 minutes to transmit. The first five images to be received and processed on the ground are expected to include a close up of Tempel 1's nucleus. All data from the flyby (including the images and science data obtained by the spacecraft's two onboard dust experiments) are expected to take about 10 hours to reach the ground.

Stardust-NExT is a low-cost mission that will expand the investigation of comet Tempel 1 initiated by NASA's Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, manages Stardust-NExT for the NASA Science Mission Directorate, Washington, D.C. Joe Veverka of Cornell University, Ithaca, N.Y., is the mission's principal investigator. Lockheed Martin Space Systems, Denver Colo., built the spacecraft and manages day-to-day mission operations.

More information about Stardust-NExT is online at: http://stardustnext.jpl.nasa.gov .