Today, their legacy continues as they develop the science infrastructure using NASA’s newest tool in its airborne research fleet, the Global Hawk Unmanned Aircraft System (UAS). "It is NASA's first fully autonomous, high altitude, long endurance UAS. It will give scientists the ability to carry payloads to remote regions of the atmosphere and remain there for long durations collecting key measurements," said Michael Craig, research manager at NASA's Ames and project manager for the first Earth science Global Hawk experiment, known as the Global Hawk Pacific (GloPac) mission.

The Global Hawk has a flight duration of more than 30 hours, a maximum altitude of 65,000 feet, a range of 11,000 nautical miles, and a payload capability of more than 1,500 lbs. of scientific instruments. No other manned or unmanned aircraft can meet these performance capabilities. NASA Dryden Flight Research Center, Edwards, Calif., has acquired three of the first seven Global Hawk aircraft produced for the U.S. Air Force and, through an agreement with the manufacturer, Northrop Grumman Corp., Los Angeles, is modifying them for Earth science operations.

The GloPac mission, now underway at Dryden, has completed its first flights with tremendous success and NASA Ames has played a vital role in providing the management, flight planning, meteorological constraints and science instrument infrastructure and communications required with this new platform. GloPac and the Airborne Science Program are funded by the Earth Science Division of NASA's Science Mission Directorate in Washington.

"It's really amazing to see all these state-of-the-art technologies and hard work come together to create such an outstanding capability," said Craig.

GloPac is being conducted in support of NASA’s Aura and A-Train satellite Earth Observation System constellation. The mission will consist of four to five science flights that will take the aircraft over the Pacific south to the equator, north to the Arctic and to the west past Hawaii. The payload includes 11 science instruments that will collect a wide range of atmospheric data, including trace gases and aerosol composition, as well as meteorological parameters.

"These observations are important for understanding processes that control ozone-depleting substances, greenhouse gases that contribute to climate change and pollution that impacts air quality," explained Craig.

There are over 100 people working on the GloPac mission. This includes managers, pilots, scientists, engineers, aircraft ground crew, and other support staff from NASA, the National Oceanic and Atmospheric Administration (NOAA), several universities and others. The NASA team includes members from Ames Research Center, Dryden Flight Research Center, Goddard Space Flight Center, Greenbelt, Md., Jet Propulsion Laboratory, Pasadena, Calif., and NASA Headquarters, Washington.

"This team is transforming the way Earth Science airborne missions will be performed in the future," said Craig.

Several other teams are developing new research missions and applications for the Global Hawk, and NASA is now working on a mobile control center that will give the aircraft truly global coverage. Later this summer, NASA will use the Global Hawk to monitor hurricane development and intensification. Scientists predict that in future years, the aircraft could be used to monitor a number of natural and human-made changes to our planet, including climate change, ice thicknesses, and ecosystems.

Global Hawk program is a collaborative effort between NASA’s Earth Science, the Northrop Grumman Corp., and NOAA.

The planets had been imaged previously by two of the world's biggest ground-based telescopes -- one of the two 10-meter (33-foot) telescopes of W.M. Keck Observatory and the 8.0-meter (26-foot) Gemini North Observatory, both on Mauna Kea in Hawaii. The planets, which orbit the star HR 8799, were among the very first to be directly imaged, a discovery announced in Nov. of 2008.

The new image of the planets, taken in infrared light as before, was captured using just a 1.5-meter-diameter (4.9-foot) portion of the Hale telescope's mirror. The astronomy team took painstaking efforts to push current technology to the point where such a small mirror could be used. They combined two techniques -- adaptive optics and a coronagraph -- to minimize the glare from the star and reveal the dim glow of the much fainter planets.

The picture is online at http://www.nasa.gov/topics/universe/features/exoplanet20100414-a.html.

"Our technique could be used on larger ground-based telescopes to image planets that are much closer to their stars, or it could be used on small space telescopes to find possible Earth-like worlds near bright stars," said Gene Serabyn, an astrophysicist at JPL and visiting associate in physics at the California Institute of Technology in Pasadena. Serabyn is lead author of a report on the findings in the April 15 issue of the journal Nature.

The three planets, called HR8799b, c and d, are thought to be gas giants similar to Jupiter, but more massive. They orbit their host star at roughly 24, 38 and 68 times the distance between our Earth and sun, respectively (our Jupiter resides at about five times the Earth-sun distance). It's possible that rocky worlds like Earth circle closer to the planets' star, but with current technology, they would be impossible to see under the star's glare.

The star HR 8799 is a bit more massive than our sun, and much younger, at about 60 million years, compared to our sun's approximately 4.6 billion years. It is 120 light-years away in the constellation Pegasus. This star's planetary system is still active, with bodies crashing together and kicking up dust, as recently detected by NASA's Spitzer Space Telescope (http://spitzer.caltech.edu/news/1000-feature09-16-Unsettled-Youth-Spitzer-Observes-a-Chaotic-Planetary-System). Like fresh-baked bread out of the oven, the planets are still warm from their formation and emit enough infrared radiation for telescopes to see.

To take a picture of HR 8799's planets, Serabyn and his colleagues first used a method called adaptive optics to reduce the amount of atmospheric blurring, or to take away the "twinkle" of the star. This technique was optimized by using only a small piece of the telescope. Once the twinkle was removed, the light from the star itself was blocked using the team's coronograph, an instrument that selectively masks out the star. A novel "vortex coronagraph," invented by team member Dimitri Mawet of JPL, was used for this step. The final result was an image showing the light of three planets.

"The trick is to suppress the starlight without suppressing the planet light," said Serabyn.

The technique can be used to image the space lying just fractions of a degree from a star (about one degree divided by roughly 10,000). This is as close to the star as that achieved by Gemini and Keck -- telescopes that are about five and seven times larger, respectively.

Keeping telescopes small is critical for space missions. "This is the kind of technology that could let us image other Earths," said Wesley Traub, the chief scientist for NASA's Exoplanet Exploration Program at JPL. "We are on our way toward getting a picture of another pale blue dot in space."

JPL is a partner with the California Institute of Technology in Pasadena in the Palomar Observatory. Caltech manages JPL for NASA. More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov . More information about the Palomar Observatory is at http://www.astro.caltech.edu/palomar/ .

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The design load limit test will provide engineers with a better understanding of the full structural capabilities of the drogue parachute, currently under development to return next-generation space vehicles safely to Earth.

This was the second in a series of three planned load limit tests designed to place the loads expected in flight on the parachute canopy. The next test series, called overload tests, will subject the parachute canopy to loads greater than what would typically be experienced in flight, to prove the parachute is strong enough to survive some degree of unexpected events.

Future full resolution images of the drogue parachute test will be made publicly available when they are fully processed:

Each team of scientists took advantage of extensive Chandra observations of galaxy clusters, the largest objects in the Universe bound together by gravity. One result undercuts a rival gravity model to General Relativity, while the other shows that Einstein's theory works over a vast range of times and distances across the cosmos.

The first finding significantly weakens a competitor to General Relativity known as "f(R) gravity".

"If General Relativity were the heavyweight boxing champion, this other theory was hoping to be the upstart contender," said Fabian Schmidt of the California Institute of Technology in Pasadena, who led the study. "Our work shows that the chances of its upsetting the champ are very slim."

In recent years, physicists have turned their attention to competing theories to General Relativity as a possible explanation for the accelerated expansion of the universe. Currently, the most popular explanation for the acceleration is the so-called cosmological constant, which can be understood as energy that exists in empty space. This energy is referred to as dark energy to emphasize that it cannot be directly detected.

In the f(R) theory, the cosmic acceleration comes not from an exotic form of energy but from a modification of the gravitational force. The modified force also affects the rate at which small enhancements of matter can grow over the eons to become massive clusters of galaxies, opening up the possibility of a sensitive test of the theory.

Schmidt and colleagues used mass estimates of 49 galaxy clusters in the local universe from Chandra observations, compared them with theoretical model predictions and studies of supernovas, the cosmic microwave background, and the large-scale distribution of galaxies.

They found no evidence that gravity is different from General Relativity on scales larger than 130 million light years. This limit corresponds to a hundred-fold improvement on the bounds of the modified gravitational force's range that can be set without using the cluster data.

"This is the strongest ever constraint set on an alternative to General Relativity on such large distance scales," said Schmidt. "Our results show that we can probe gravity stringently on cosmological scales by using observations of galaxy clusters."

The reason for this dramatic improvement in constraints can be traced to the greatly enhanced gravitational forces acting in clusters as opposed to the universal background expansion of the universe. The cluster-growth technique also promises to be a good probe of other modified gravity scenarios, such as models motivated by higher- dimensional theories and string theory.

A second, independent study also bolsters General Relativity by directly testing it across cosmological distances and times. Up until now, General Relativity had been verified only using experiments from laboratory to Solar System scales, leaving the door open to the possibility that General Relativity breaks down on much larger scales.

To probe this question, a group at Stanford University compared Chandra observations of how rapidly galaxy clusters have grown over time to the predictions of General Relativity. The result is nearly complete agreement between observation and theory.

“Einstein's theory succeeds again, this time in calculating how many massive clusters have formed under gravity's pull over the last five billion years,” said David Rapetti of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and SLAC National Accelerator Laboratory, who led the new study. “Excitingly and reassuringly, our results are the most robust consistency test of General Relativity yet carried out on cosmological scales."

Rapetti and his colleagues based their results on a sample of 238 clusters detected across the whole sky by the now-defunct ROSAT X-ray telescope. These data were enhanced by detailed mass measurements for 71 distant clusters using Chandra, and 23 relatively nearby clusters using ROSAT, and combined with studies of supernovas, the cosmic microwave background, the distribution of galaxies and distance estimates to galaxy clusters.

Galaxy clusters are important objects in the quest to understand the Universe as a whole. Because the observations of the masses of galaxy clusters are directly sensitive to the properties of gravity, they provide crucial information. Other techniques such as observations of supernovas or the distribution of galaxies measure cosmic distances, which depend only on the expansion rate of the universe. In contrast, the cluster technique used by Rapetti and his colleagues measure in addition the growth rate of the cosmic structure, as driven by gravity.

"Cosmic acceleration represents a great challenge to our modern understanding of physics," said Rapetti's co-author Adam Mantz of NASA's Goddard Space Flight Center in Maryland. "Measurements of acceleration have highlighted how little we know about gravity at cosmic scales, but we're now starting to push back our ignorance."

The paper by Fabian Schmidt was published in Physics Review D, Volume 80 in October 2009 and is co-authored by Alexey Vikhlinin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and Wayne Hu of the University of Chicago, Illinois. The paper by David Rapetti was recently accepted for publication in the Monthly Notices of the Royal Astronomical Society and is co- authored by Mantz, Steve Allen of KIPAC at Stanford and Harald Ebeling of the Institute for Astronomy in Hawaii.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

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