Clementine Project Information

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Clementine was a joint project between the Strategic Defense Initiative Organization and NASA. The objective of the mission was to test sensors and spacecraft components under extended exposure to the space environment and to make scientific observations of the Moon and the near-Earth asteroid 1620 Geographos. The observations included imaging at various wavelengths including ultraviolet and infrared, laser ranging altimetry, and charged particle measurements. These observations were originally for the purposes of assessing the surface mineralogy of the Moon and Geographos, obtaining lunar altimetry from 60N to 60S latitude, and determining the size, shape, rotational characteristics, surface properties, and cratering statistics of Geographos.

Clementine was launched on 25 January 1994 at 16:34 UTC (12:34 PM EDT) from Vandenberg AFB aboard a Titan IIG rocket. After two Earth flybys, lunar insertion was achieved on February 21. Lunar mapping took place over approximately two months, in two parts. The first part consisted of a 5 hour elliptical polar orbit with a perilune of about 400 km at 28 degrees S latitude. After one month of mapping the orbit was rotated to a perilune of 29 degrees N latitude, where it remained for one more month. This allowed global imaging as well as altimetry coverage from 60 degrees S to 60 degrees N.

After leaving lunar orbit, a malfunction in one of the on-board computers on May 7 at 14:39 UTC (9:39 AM EST) caused a thruster to fire until it had used up all of its fuel, leaving the spacecraft spinning at about 80 RPM with no spin control. This made the planned continuation of the mission, a flyby of the near-Earth asteroid Geographos, impossible. The spacecraft remained in geocentric orbit and continued testing the spacecraft components until the end of mission.

More information on the Clementine mission, instruments, and early results can also be found in the Clementine special issue of Science magazine, Vol. 266, No. 5192, December 1994.

NASA Satellites Help Lift Cloud of Uncertainty on Climate Change

12.12.07

New data from NASA's CloudSat show that, on average, 13 percent of clouds observed over Earth's oceans at any time are producing rain that reaches the surface, much higher than previously speculated. In this image, blue indicates a low fraction of precipitating clouds, while yellow, orange and red indicate a higher percentage. Image credit: NASA/JPL/The Cooperative Institute for Research in the Atmosphere (CIRA), Colorado State University
› Larger view SAN FRANCISCO - New findings from NASA's CloudSat and other spacecraft in NASA's "A-Train" constellation of five Earth observing satellites offer important insights into this year's record reduction of Arctic sea ice, global rainfall patterns and the effects of pollution on clouds.

The investigations are giving scientists a greater understanding of factors influencing Earth's present climate and an important foundation for better understanding long-term climate change.

Speaking at the fall meeting of the American Geophysical Union in San Francisco, Graeme Stephens, CloudSat principal investigator and professor of atmospheric science at Colorado State University, Fort Collins, Colo., outlined results of several recent studies currently in peer review.

In one study, a team led by Jennifer Kay at the National Center for Atmospheric Research, Boulder, Colo., examined the influence of polar clouds on 2007's record low extent of Arctic sea ice. Using data from CloudSat and NASA's Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite, they found the total cloud cover over the western Arctic, where most of the ice loss occurred, was 16 percent less over the 2007 melt season than in 2006. The resulting clearer skies in 2007 heated the Arctic surface enough to warm ocean waters by 2.4 degrees Celsius (four degrees Fahrenheit) or enough to melt 0.3 meters (one foot) of sea ice. Anomalous clouds, in addition to other weather factors, helped melt ice that had already thinned due to sustained warming in recent years.

The results highlight the importance of weather pattern variability to a warming Arctic environment. "As Arctic sea ice thins, its extent is more sensitive to year-to-year variability in weather and cloud patterns," said Kay. "Our data show that clearer skies this summer allowed more of the sun's energy to melt the vulnerably thin sea ice and heat the ocean surface."

A separate CloudSat study led by John Haynes at Colorado State University found it rains more often and in greater amounts over Earth's oceans than previously estimated. The team found that, on average, 13 percent of clouds over Earth's oceans produce rain that reaches the surface. The difference in total rainfall amount estimates was greatest during winter, when large storms produced much more rainfall than previously estimated.

"These results suggest there is considerably more water falling from our skies, at least over Earth's oceans, than we previously thought," said Haynes. "The implications of these results are substantial and are still being examined, and suggest it may be necessary to reassess climate model estimates of Earth's water cycle intensity. By improving our understanding of present rainfall patterns, scientists can also improve climate model projections of how rainfall will increase or decrease in the future around the world."

CloudSat is providing some of the first, most direct observations of where rainfall occurs on a near-global basis, allowing scientists to see, for the first time, what fraction of Earth's clouds precipitate. It surveys ocean regions where measurements did not previously exist -- regions where the United Nations' Intergovernmental Panel on Climate Change suggests the greatest changes are occurring. It complements NASA's Tropical Rainfall Measuring Mission and offers a test bed for its planned Global Precipitation Measurement mission.

In another study, Colorado State University student Matt Lebsock and Stephens found the first global evidence that pollution of clouds by aerosols -- small particles suspended in the atmosphere -- is indeed making clouds brighter and more reflective, reducing the amount of sunlight available to warm the surface. These indirect aerosol effects are not well understood and create major uncertainties in climate models. The team combined data from CloudSat with the Advanced Microwave Scanning Radiometer-Earth Observing System and Moderate Resolution Imaging Spectroradiometer instruments on NASA's Aqua satellite.

Scientists had previously believed that aerosols indirectly altered sunlight reflected by clouds by altering the sizes of cloud particles. The new observations also show that aerosols might allow clouds to grow deeper, increasing the amount of sunlight reflected from them even more than previously thought.

The Afternoon, or "A-Train" satellite constellation presently consists of five satellites flying in formation around the globe. Each satellite within the A-Train has unique measurement capabilities that greatly complement each other. The combined set of measurements is providing new insights into the global distribution and evolution of clouds that will lead to improvements in weather forecasting and climate prediction.

Background materials for today's briefing are online at: http://www.nasa.gov/mission_pages/cloudsat/news/secret_clouds.html . For more on CloudSat and the A-Train, see: http://www.nasa.gov/cloudsat.

Additional media contacts for this story: Emily Wilmsen, Colorado State University, 970-491-2336, Emily.wilmsen@colostate.edu; and David Hosansky, National Center for Atmospheric Research, 303-497-8611, hosansky@ucar.edu .

From Dave McComas, IBEX Principal Investigator

Throughout November the IBEX team worked to complete spacecraft integration and begin final testing. One of the first tests - spin balance - is shown in the brief video clip. In this test the full spacecraft is spun at rates up to 70 RPM! We spun the spacecraft both in air and in a Helium tent (shown in the video) to simulate the vacuum environment of space (Helium is only 14% as dense as air). Once the initial spinning was done we added little balance masses, very much like the auto shop does when they balance your car tires.

Other critical activities included testing of the flight software. This software provides the "brains" for operating the spacecraft on orbit and covers not just normal operations, but also things like automatic safing in case anything goes wrong during the roughly week-long intervals when the spacecraft will be operating autonomously. This month I'm delighted to introduce Erin Walter from Orbital Sciences. As the IBEX flight software lead, she is responsible for making sure that all of the software works perfectly. Erin has been doing a great job of owning the critical flight software for us.

Erin Walter

By Christine Minerva, Adler Planetarium Educator

If passing a computer class had not been a college graduation requirement, Erin Walter might never have worked on a NASA mission.

Originally a business major at the University of Michigan, Erin enrolled in a computer class because it was mandatory. She soon found the computer curriculum so absorbing that she ignored assignments in her business classes, like accounting. "I had an exam in my accounting class the next day, and a computer class project that was due in about three months. The night before the accounting exam, I stayed up to finish my computer project instead of studying for the exam!" Erin said. It was her first indication that computer programming was a good fit for her interests.

After completing the computer class, Erin switched her major to computer science. The following year, she became one of the few University of Michigan undergraduates to teach other undergraduates as an instructor for the same computer class. She continues to further her education, and is completing a master's degree in software engineering from the University of Michigan, and is in the process of earning another advanced degree in systems engineering at George Washington University.

As a child, Erin had no idea that spacecraft software engineering was in her future. In fact, she aspired to be a lawyer. Born in San Jose, California, Erin moved to the Ann Arbor, Michigan area with her family when she was two years old. She attended Walled Lake Western High School, graduating a semester early before going on to the University of Michigan for college.

She is grateful that her alma mater required her to take classes outside her major. "I think when colleges require students to take classes outside of their majors it provides a tremendous opportunity for students to become interested in areas they never would have imagined or maybe even find their career, like I did. Taking a computer class made me realize that I was going to be happier in another field. I chose to major in business because I didn't know what I wanted, and I thought I could get a job with that degree. But I was never really all that interested in business. Once I took a computer class, I was interested in the logical nature of computers. Computer science made sense to me - it was very natural for me to understand how things worked together to make a computer work," she said.

Erin went on to a varied career in computer software engineering. After college, she worked for a private software company before taking a position to create software for an instrument on NASA's Cassini mission, now orbiting Saturn. Her position there included ground software, flight software, operations and running the lab. Since then, she has moved on to greater challenges as the flight software lead for the MicroStar product line at Orbital Sciences Corporation. The MicroStar is the type of spacecraft "bus", to which the science instruments are attached. "I develop the flight software that essentially runs the MicroStar spacecraft," she said. "The spaceflight software is kind of like if you had to build artificial intelligence to drive a car and manage the hardware aspects as well. The hardware is like the car and you automate the rest, like the steering, the car battery, and all the stuff someone does when they drive a car, through the software." To ensure that everything works correctly, Erin programs the software to correct for problems that may occur. "The software detects flaws. For instance, if we detect that the battery is too low, the software may maneuver the IBEX spacecraft to point towards the Sun to recharge, and it may shut down things that are unnecessary in order to conserve energy," she said.

Her education and software experience prepared her for the work she does now. "I was well prepared for the technical aspects of my job by my education. My prior job experience prepared me for my management role, time management skills, spacecraft knowledge, people skills, etc." In the future, she hopes to take what she has learned and apply it to the management of an entire project.

Erin leads a diverse team of men and women from around the world who write the software that controls IBEX. "They are an incredible good group of people and it really is my privilege to have them on my team" she said. "They are very knowledgeable and experienced on this type of spacecraft," she said.

After she and her team write the software, Erin's job transitions to testing the software and eventually to assisting in operating the spacecraft. In the past month, Erin has been focusing on assisting in testing the IBEX spacecraft to make sure the software will work correctly in space. This has involved creating test procedures and troubleshooting. "During integrating and testing of a spacecraft, certain things might not work the way [the scientists and engineers] want them to. They'll change a requirement or find a bug, so I go ahead and make those changes to the software and redeliver it to the spacecraft. Then, they rerun those tests to make sure that the change they said they wanted works the way they want it to," she said.

When the software is finalized, Erin and her team co-author an operating manual for the spacecraft, and then she is "on call" to help operate IBEX. "As the mission goes on, myself and my team typically become the ones who knows how many things work and how to command the spacecraft to do certain things, so [the scientists] call me up and ask, 'How do I make the spacecraft do x, y, or z?' and I tell them how," Erin said.

She loves the problem-solving aspects of her job. "The best part of my job is helping design the requirements and functionality of the spacecraft based on the requirements, and finding the most optimal solution," she said.

Although software engineering keeps her busy, Erin still finds time to pursue a range of hobbies. "I enjoy pottery, art, going to plays and shows, watching football, reading, scuba diving and always seeking out new experiences," Erin said.