Space Station

James Webb Space Telescope First Flight Mirror Completes Cryogenic Testing

Fri, 10 Apr 2009 08:09:33 GMT

The first mirror segment that will fly on the James Webb Space Telescope, built by Northrop Grumman Corporation, has completed its first series of cryogenic temperature tests in the X-ray and Cryogenic Facility at the Marshall Space Flight Center in Huntsville, Ala.

"We�re excited that we can support the James Webb Space Telescope with our world class cryogenic and x-ray telescope test facility," said Helen Cole, project manager for the Webb Telescope activities at NASA's Marshall Space Flight Center, Huntsville, Ala. "The test performed here are crucial to the success of the program since they�ll ensure the mirrors and components will be able to withstand the extreme cold temperatures of space."

The mirror segment is the first of 18 flight mirror segments that will be joined to make a giant, 6.5-meter diameter (21.3 ft.) hexagonal mirror. The segments will be subject to temperatures of -414 degrees Fahrenheit in a 7,600 cubic-foot helium-cooled vacuum chamber at NASA Marshall.

Engineers will measure how the mirror changes shape going from room temperature to cryogenic (frigid) temperatures, as the metal expands and contracts. They can model these changes to some extent, but not perfectly. The mirrors will be polished to about 100 nanometers (a human hair is approximately 60,000 to 120,000 nanometers) accuracy at room temperature, based on the expected changes. Then it will be cooled down to cryogenic temperatures and engineers will measure the mirror's surface, creating a "hit map" of unexpected changes.

"This is what we have done so far with the first flight mirror segment," said Jonathan Gardner, Webb Telescope Deputy Project Scientist at NASA Goddard Space Flight Center, Greenbelt, Md. "Now, engineers will warm it up and polish out the "hit map" areas to get the mirror to 20 nanometer accuracy - a process which will take months. The mirrors will then be brought back down to cryogenic temperatures to verify the increased accuracy." In addition to this testing, engineers also did some "cryo cycling." That means going up and down in temperature (without polishing in between) to test the repeatability of the changes.

Since there are 18 mirror segments, each measuring about 1.5 meters (4.9 ft.) in diameter, they will be tested in batches of six and chilled to cryogenic temperatures four times in a six-week time span. It takes approximately five days to cool a mirror segment to cryogenic temperatures. All flight mirror tests are expected to be completed in June 2011. The Webb telescope is scheduled for launch in 2013.

Northrop Grumman is the prime contractor for the Webb telescope, leading a design and development team under contract to NASA�s Goddard Space Flight Center.

"It has taken years of intense effort for the Webb Telescope team to begin flight mirror cryotesting and we�re gratified that testing was successful," said Martin Mohan, Webb telescope program manager for Northrop Grumman�s Aerospace Systems sector, Redondo Beach, Calif. "Along the way, we�ve had to invent entire manufacturing and measurement processes because no one has ever built a telescope this large that has to operate at temperatures this extreme."

The James Webb Space Telescope is the next-generation premier space observatory, exploring deep space phenomena from distant galaxies to nearby planets and stars. The Webb Telescope will give scientists clues about the formation of the universe and the evolution of our own solar system, from the first light after the Big Bang to the formation of star systems capable of supporting life on planets like Earth.

Satellite Images Depict Thinning Arctic Ice

Wed, 08 Apr 2009 10:34:04 GMT

The latest Arctic sea ice data from NASA and the National Snow and Ice Data Center show that the decade-long trend of shrinking sea ice cover is continuing. New evidence from satellite observations also shows that the ice cap is thinning as well.

Arctic sea ice works like an air conditioner for the global climate system. Ice naturally cools air and water masses, plays a key role in ocean circulation, and reflects solar radiation back into space. In recent years, Arctic sea ice has been declining at a surprising rate.

Scientists who track Arctic sea ice cover from space announced today that this winter had the fifth lowest maximum ice extent on record. The six lowest maximum events since satellite monitoring began in 1979 have all occurred in the past six years (2004-2009).

Until recently, the majority of Arctic sea ice survived at least one summer and often several. But things have changed dramatically, according to a team of University of Colorado, Boulder, scientists led by Charles Fowler. Thin seasonal ice -- ice that melts and re-freezes every year -- makes up about 70 percent of the Arctic sea ice in wintertime, up from 40 to 50 percent in the 1980s and 1990s. Thicker ice, which survives two or more years, now comprises just 10 percent of wintertime ice cover, down from 30 to 40 percent.

According to researchers from the National Snow and Ice Data Center in Boulder, Colo., the maximum sea ice extent for 2008-09, reached on Feb. 28, was 5.85 million square miles. That is 278,000 square miles less than the average extent for 1979 to 2000.

"Ice extent is an important measure of the health of the Arctic, but it only gives us a two-dimensional view of the ice cover," said Walter Meier, research scientist at the center and the University of Colorado, Boulder. "Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover. As the ice cover in the Arctic grows thinner, it grows more vulnerable to melting in the summer."

The Arctic ice cap grows each winter as the sun sets for several months and intense cold sets in. Some of that ice is naturally pushed out of the Arctic by winds, while much of it melts in place during summer. The thicker, older ice that survives one or more summers is more likely to persist through the next summer.

Sea ice thickness has been hard to measure directly, so scientists have typically used estimates of ice age to approximate its thickness. But last year a team of researchers led by Ron Kwok of NASA's Jet Propulsion Laboratory in Pasadena, Calif., produced the first map of sea ice thickness over the entire Arctic basin.

Using two years of data from NASA's Ice, Cloud, and land Elevation Satellite (ICESat), Kwok's team estimated thickness and volume of the Arctic Ocean ice cover for 2005 and 2006. They found that the average winter volume of Arctic sea ice contained enough water to fill Lake Michigan and Lake Superior combined.

The older, thicker sea ice is declining and is being replaced with newer, thinner ice that is more vulnerable to summer melt, according to Kwok. His team found that seasonal sea ice averages about 6 feet in thickness, while ice that had lasted through more than one summer averages about 9 feet, though it can grow much thicker in some locations near the coast.

Kwok is currently working to extend the ICESat estimate further, from 2003 to 2008, to see how the recent decline in the area covered by sea ice is mirrored in changes in its volume.

"With these new data on both the area and thickness of Arctic sea ice, we will be able to better understand the sensitivity and vulnerability of the ice cover to changes in climate," Kwok said.

NASA Astronaut Tweets Provide Inside Look at Mission Training

Wed, 08 Apr 2009 10:32:30 GMT

NASA astronaut Mike Massimino is using Twitter to provide a unique, behind the scenes peek at the last weeks of his training for the fifth and final shuttle servicing mission to NASA's Hubble Space Telescope.

Massimino, whose Twitter username is Astro_Mike (@Astro_Mike), will fly aboard space shuttle Atlantis as a mission specialist and spacewalker during the STS-125 mission, targeted to launch May 12. Atlantis' 11-day flight will include five spacewalks to refurbish and upgrade Hubble with state-of-the-art science instruments. After the astronaut's visit, Hubble's capabilities will be expanded and its lifetime extended through at least 2014.

This will be Massimino's second trip to space. He first flew on the STS-109 mission to Hubble in 2002. During that flight, he performed two spacewalks.

Along with Massimino, the crew of Atlantis includes Commander Scott Altman, Pilot Gregory C. Johnson and Mission Specialists Andrew Feustel, Michael Good, John Grunsfeld and Megan McArthur.

To follow Massimino's Twitter, visit:

http://twitter.com/Astro_Mike

Follow NASA mission activities on Twitter @NASA, and for a complete list of all agency missions on Twitter, visit:

http://www.nasa.gov/collaborate

For information about the STS-125 mission and its crew, visit:

http://www.nasa.gov/shuttle

Cassini Top 10 Science Highlights

Tue, 07 Apr 2009 08:32:32 GMT

While touring the Saturn system in 2008, Cassini enabled great scientific studies and observations. Below is captured the Top 10 Science Highlights of the year as selected by the science teams.

Identification of liquid ethane in a lake on Titan
Polar storms on Saturn
Strong inference of a liquid water layer in Titan's interior
The likelihood of dusty rings around Rhea
The possibility of plate-tectonic-like spreading in the Enceladus south polar region
Water vapor jets inside the plume of gas leaving Enceladus
Moonlet population in and around the F ring
New insights into Saturn's aurora
Three belts of sub-moonlets in the A ring (propellers)
Six month-old lightning storm shatters record for longevity

1) Identification of liquid ethane in a lake on Titan

NASA scientists have concluded that at least one of the large lakes observed on Saturn's moon Titan contains liquid hydrocarbons, and have positively identified the presence of ethane. This makes Titan the only body in our solar system beyond Earth known to have liquid on its surface.

Scientists made the measurements using data from an instrument aboard the Cassini spacecraft. The instrument identified chemically different materials based on the way they absorb and reflect infrared light. Before Cassini, scientists thought Titan would have global oceans of methane, ethane and other light hydrocarbons. More than 40 close flybys of Titan by Cassini show no such global oceans exist, but hundreds of dark, lake-like features are present. Until now, it was not known whether these features were liquid or simply dark, solid material.

Also see:
NASA Confirms Liquid Lake on Saturn Moon

Cassini Finds Hydrocarbon Rains May Fill Titan Lakes

2) Polar storms on Saturn

Cassini scientists revisited the north polar hexagon last year. This huge polygonal pattern in the clouds was first seen by Voyager in 1980. In 2008, Cassini found that the aurora glows at infrared wavelengths at the same latitude as the hexagon, suggesting a connection over a huge range of altitudes.

In addition, Cassini found a hot spot resembling the eye of a hurricane, but it is locked to the north pole at the center of the hexagon, with swirling cyclonic winds signifying a low pressure center. The hot spot is confined to latitudes above 88 degrees, while the corners of the hexagon are at 75 degrees.

The north polar hot spot resembles one in the south that was imaged in exquisite detail in 2008 These findings cast light on how large vortices - swirling masses of gas - behave in planetary atmospheres throughout the solar system.

The new-found cyclone at Saturn�s north pole is only visible in the near-infrared wavelengths because the north pole is in winter, thus in darkness to visible-light cameras. At these wavelengths, about seven times greater than light seen by the human eye, the clouds deep inside Saturn�s atmosphere are seen in silhouette against the background glow of Saturn�s internal heat.

Peak winds exceed 450 kilometers per hour (280 mph, or 130 m/s) near 88 degrees latitude. New measurements by Cassini show that clouds within the hexagonal feature located near 77 degrees north latitude zoom around the �race track� of the hexagon at this same high speed -- 460 kilometers per hour (127 meters per second, or 285 mph) -- while the hexagonal �race track� itself stays nearly stationary in Saturn�s atmosphere.

3) Strong inference of a liquid water layer in Titan's interior

NASA's Cassini spacecraft has found evidence that points to the existence of an underground ocean of water and ammonia on Saturn's moon Titan. The findings, made using radar measurements of Titan's rotation, appeared in the March 21 issue of the journal Science.

"With its organic dunes, lakes, channels and mountains, Titan has one of the most varied, active and Earth-like surfaces in the solar system," said Ralph Lorenz, lead author of the paper and Cassini radar scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Md., "Now we see changes in the way Titan rotates, giving us a window into Titan's interior beneath the surface."

Subsequent data has suggested that these radar observations may be related to precession, only indirectly related to the presence of an ocean, but other geophysical evidence continues to point to a subsurface ocean. Titan continues to amaze and confound!

4) The likelihood of dusty rings around Rhea

NASA's Cassini spacecraft has found evidence of material orbiting Rhea, Saturn's second largest moon. This is the first time rings may have been found around a moon.

A broad debris disk and at least one ring appear to have been detected by a suite of six instruments on Cassini specifically designed to study the atmospheres and particles around Saturn and its moons.

5) The possibility of plate-tectonic-like spreading in the Enceladus south polar region

The closer scientists look at Saturn's small moon Enceladus, the more they find evidence of an active world. The most recent flybys of Enceladus made by NASA's CAssini spacecraft have provided new signs of ongoing changes on and around the moon. The latest high-resolution images of Enceladus show signs that the south polar surface changes over time.

Close views of the southern polar region, where jets of water vapor and icy particles spew from vents within the moon's distinctive "tiger stripe" fractures, provide surprising evidence of Earth-like tectonics. They yield new insight into what may be happening within the fractures. The latest data on the plume -- the huge cloud of vapor and particles fed by the jets that extend into space -- show it varies over time and has a far-reaching effect on Saturn's magnetosphere.

6) Water vapor jets inside the plume of gas leaving Enceladus

Scientists continue to search for the cause of the geysers on Saturn's moon Enceladus. The geysers are visible as a large plume of water vapor and ice particles escaping the moon. Inside the plume are jets of dust and gas. What causes and controls the jets is a mystery. The Cassini spacecraft continues to collect new data to look for clues.

At the heart of the search is the question of whether the jets originate from an underground source of liquid water. Some scientists working on the Cosmic Dust Analyzer (CDA) have suggested that the sodium found present in the E ring can be traced back to liquid in Enceladus. Some other theories offer models where the jets could be caused by mechanisms that do not require liquid water. Painstaking detective work by Cassini scientists is testing the possibilities to get closer to an answer.

7) Moonlet population in and around the F ring

A team of scientists led from the UK has found that the rapid changes in Saturn's F ring can be attributed to small moonlets causing perturbations. Their results are reported in Nature (June 5, 2008).

Saturn's F ring has long been of interest to scientists as its features change on timescales from hours to years and it is probably the only location in the solar system where large scale collisions happen on a daily basis. Understanding these processes helps scientists understand the early stages of planet formation.

Models have been developed which clearly imply a population of perhaps hundreds of unseen objects with sizes between 100 meters and 1 kilometer or so, both lying within and also criss-crossing through the narrow F ring core and causing havoc in the orbits of its particles.

Stellar occultations also found a number of clumps and opaque objects, measuring their size directly to be in the few hundred meter size range.

8) New insights into Saturn's aurora

Saturn has its own unique brand of aurora that lights up the polar cap, unlike any other planetary aurora known in our solar system. This odd phenomenon revealed itself to one of the infrared instruments on NASA's Cassini spacecraft.

Also see:
Cassini Finds Mysterious New Aurora on Saturn

9) Three belts of sub-moonlets in the A ring (propellers)

A new comprehensive study established the existence and orbital properties of an order of magnitude more objects of 100-300 metersacross buried in the rings than previously known. These objects have been dubbed "propellors" because of the shape of the surrounding material they disturb. The greatly improved statistics revealed that these large objects occupy three distinct belts in the A ring, which correlate with nearby resonances or gaps in no obvious way. No evidence for such objects has been found in other rings.

It remains unknown if the objects are primordial "shards" or locally grown, but it is now clear that the mass in this population is much smaller than in the visible ring particles themselves.

10) Six month-old lightning storm shatters record for longevity

Two instruments on Cassini regularly team up to monitor lightning storms in Saturn's atmosphere. The RPWS detects radio pulses from the electrical discharges, and the ISS images the storms. The RPWS only detects the electrical discharges when the storm is on the side of Saturn facing the spacecraft or just over the horizon on the night side.

Often a year goes by when there are no discharges, during which time the ISS does not see the storms. Then suddenly the radio signals begin and a new storm appears in the atmosphere. One such storm was identified on November 27, 2007, probably within a day of its birth. Unlike past storms, which lasted for a few weeks at best, this one lasted for 7.5 months and thereby set a new record for longevity of lightning storms throughout the solar system.

"Signatures in Space" Connects Kids to Space Day Celebrations

Mon, 06 Apr 2009 08:37:26 GMT

NASA and Lockheed Martin's Student Signatures in Space (S3) program will be one of the highlighted projects during this year's Space Day, celebrated annually on the first Friday in May. The mission of Space Day is to use space-related activities to inspire and prepare young people for careers in science, technology, engineering and mathematics.

Student Signatures in Space began in 1997 as a way to draw kids into space studies by giving them a personal connection to space. Participating schools are sent large posters for students to sign on Space Day. NASA and Lockheed Martin, of Bethesda, Md., are currently accepting school names for participation. The program is open to elementary, middle, and high schools, as well as science museums and regional Boy Scout and Girl Scout councils.

After schools return the posters to Lockheed Martin, the signatures are scanned onto a disk and flown aboard a space shuttle mission. Schools also receive lesson plans and information about the mission their signed posters are flying on.

Upon completion of the shuttle flight, the posters are returned to the schools along with a photo of the astronaut crew that took the signatures to space and a NASA flight certification verifying that the signatures flew in space. Schools are allowed to participate in the signatures program once every six years.

The project is free to participants. Program partners cover all program costs, including shipping expenses for return of the signed posters. Schools and other organizations may request a sign-up form by e-mailing S3 Program Manager April Tensen at signatures@mindspring.com

Student Signatures in Space is limited to 500 schools per year, and schools are registered on a first-come, first-served basis. Schools that sign up after the maximum capacity is reached will be put on a list to participate in the following year's program.

For information on Space Day or Student Signatures in Space, visit:

http://www.spaceday.org

For information about NASA education programs, visit:

http://www.nasa.gov/education

Racers Get Ready! NASA's Off-world Racing Begins April 3 at 16th Annual Great Moonbuggy Race

Sat, 04 Apr 2009 09:41:19 GMT

Approximately 75 high school and college teams from around the world will converge on Huntsville April 3-4 for off-world racing in NASA's 16th annual Great Moonbuggy Race. Racing begins at 7:30 a.m. CDT each day and continues throughout the day.

> Media Advisory
> News Release
> Photos and Past Race Results

Active Galaxies Flare and Fade in Fermi Telescope All-Sky Movie

Sat, 04 Apr 2009 09:41:18 GMT

The gamma-ray sky comes alive in a movie made from data acquired by NASA's Fermi Gamma-ray Space Telescope during its first three months of operations. Gamma rays from sources near and far turn the sky into a hypnotic froth. The sun arcs serenely across the northern sky as active galaxies called blazars flare up and fade out.

The movie, made from the first 87 days of data from Fermi's Large Area Telescope (LAT), was revealed today during a live 24-hour video webcast called "Around the World in 80 Telescopes." Organized by the European Southern Observatory headquartered in Garching, Germany, the webcast is part of the 100 Hours of Astronomy project, a worldwide celebration of astronomy running through April 5.

"The movie shows counts of gamma rays seen by Fermi's LAT, and each frame shows the gamma rays collected in one day," said presenter Elizabeth Hays, an astrophysicist on the Fermi team. Only gamma rays with energies greater than 300 million electron volts -- or 150 million times more than that of visible light -- are shown. Brighter colors indicate greater numbers of detected gamma rays and thus the locations of bright gamma-ray sources.

The movie shows the entire sky as northern and southern halves, with the plane of our galaxy, the Milky Way, running along the circular edges. "This presentation provides a better view of sources outside our galaxy," Hays noted, "but it's an unusual way to view the sky." The northern view includes the familiar constellation Ursa Major, part of which forms the Big Dipper. The southern view includes the constellations Cetus and Pegasus.

"One of the first things to notice in the movie is the source that arcs across the northern galactic sky. That's the sun moving along the ecliptic plane," Hays said. The sun appears to move through the sky because the Earth revolves around it. This is the same reason constellations progress through the sky during the year.

However, Fermi's LAT isn't detecting gamma rays produced directly by the sun -- at least not yet. "The LAT sees the sun because cosmic rays -- nuclei traveling close to the speed of light -- strike the sun's gas and the light it emits. These collisions produce gamma rays," Hays explained. The LAT will sense the sun directly when a sufficiently powerful solar eruption occurs, but the sun is now in a quiet portion of its activity cycle.

Another striking aspect of the movie is that, even far from the brightest gamma-ray sources, the sky is not dark. "We see a general background of gamma rays over the whole sky," Hays said. Some of this glow is the result of cosmic rays colliding with gas and light in our own galaxy and producing gamma rays. But some of this emission originates from beyond our galaxy. "Although we don't know exactly where all of these gamma rays are coming from, we know that some of them must be the collective radiation from galaxies we are not detecting directly," she explained. It's possible that something more exotic could also be contributing to this background glow, and Fermi is making measurements to test such ideas.

One galactic source lies far enough from the Milky Way's plane that it stands out in the movie. "That's PSR J1836+5925, one of the new class of pulsars discovered by Fermi," Hays said. The pulsar is a fast-spinning neutron star that sends a broad fan of gamma rays toward us with each rotation. Neutron stars pack twice the mass of the sun into a sphere the size of Manhattan and can spin thousands of times in one second. "It looks steady in the movie because we have to add up gamma rays from many rotations to see the pulses," she noted.

Most of the other bright sources in the movie are actually distant galaxies. Each of these active galaxies, called blazars, hosts a central black hole with a mass of a million suns. Somehow, the black hole produces extremely fast-moving jets of matter, and with blazars we're looking almost directly down the jet. "The strong variations in brightness that you see during the movie tell us that something about these jets has changed," Hays said.

One example is the blazar AO 0235+164, located 7.5 billion light-years away in the constellation Aries. "The flares we are seeing happened when the universe was about half of its current age," she explained. "The LAT sees a very strong flare. The gamma rays increase by 30 to 40 times in a single day. On that day, AO 0235 became one of the brightest gamma-ray sources in the sky."

Fermi's LAT became the first gamma-ray telescope to see the blazar called PKS 1502+106. The galaxy, located 10 billion light-years away in the constellation Bo�tes, appeared suddenly, flared in brightness for a few days, and then faded away.

Such rapid and dramatic change underscores one of the most valuable things the Fermi team does. "We watch the sky all the time and alert other telescopes, in space and on the ground, when something interesting is going on," Hays said. This gives other astronomers the chance to watch these events at other wavelengths, such as visible light, infrared, radio, ultraviolet, X-ray, and even gamma rays above the energy the LAT can detect.

"The broader the wavelength coverage, the better our understanding of the event will be," Hays adds. "We have to be quick to catch these flares before they fade away."

How Low Can It Go? Sun Plunges into the Quietest Solar Minimum in a Century

Fri, 03 Apr 2009 12:33:35 GMT

The sunspot cycle is behaving a little like the stock market. Just when you think it has hit bottom, it goes even lower.

2008 was a bear. There were no sunspots observed on 266 of the year's 366 days (73 percent). To find a year with more blank suns, you have to go all the way back to 1913, which had 311 spotless days. Prompted by these numbers, some observers suggested that the solar cycle had hit bottom in 2008.

Maybe not. Sunspot counts for 2009 have dropped even lower. As of March 31st, there were no sunspots on 78 of the year's 90 days (87 percent).

It adds up to one inescapable conclusion: "We're experiencing a very deep solar minimum," says solar physicist Dean Pesnell of NASA�s Goddard Space Flight Center in Greenbelt, Md.

"This is the quietest sun we've seen in almost a century," agrees forecaster David Hathaway of NASA�s Marshall Space Flight Center in Huntsville, Ala.

Quiet suns come along every 11 years or so. It's a natural part of the sunspot cycle, discovered by German astronomer Heinrich Schwabe in the mid-1800s. Sunspots are planet-sized islands of magnetism on the surface of the sun, and they are sources of solar flares, coronal mass ejections, and intense UV radiation. Plotting sunspot counts, Schwabe saw that peaks of solar activity were always followed by valleys of relative calm�a clockwork pattern that has held true for more than 200 years.

The current solar minimum is part of that pattern. In fact, it's right on time. But is it supposed to be this quiet?

Measurements by the Ulysses spacecraft reveal a 20 percent drop in solar wind pressure since the mid-1990s�the lowest point since such measurements began in the 1960s. The solar wind helps keep galactic cosmic rays out of the inner solar system. With the solar wind flagging, more cosmic rays penetrate the solar system, resulting in increased health hazards for astronauts. Weaker solar wind also means fewer geomagnetic storms and auroras on Earth.

Careful measurements by several NASA spacecraft have also shown that the sun's brightness has dimmed by 0.02 percent at visible wavelengths and a whopping 6 percent at extreme UV wavelengths since the solar minimum of 1996. These changes are not enough to reverse global warming, but there are some other, noticeable side-effects.

Earth's upper atmosphere is heated less by the sun and it is therefore less "puffed up." Satellites in Earth orbit experience less atmospheric drag, extending their operational lifetimes. That�s the good news. Unfortunately, space junk also remains in orbit longer, posing an increased threat to useful satellites.

Finally, radio telescopes are recording the dimmest "radio sun" since 1955. After World War II, astronomers began keeping records of the sun's brightness at radio wavelengths, particularly 10.7 cm. Some researchers believe that the lessening of radio emissions during this solar minimum is an indication of weakness in the sun's global magnetic field. No one is certain, however, because the source of these long-monitored radio emissions is not fully understood.

All these lows have sparked a debate about whether the ongoing minimum is extreme or just an overdue market correction following a string of unusually intense solar maxima.

"Since the Space Age began in the 1950s, solar activity has been generally high," notes Hathaway. "Five of the ten most intense solar cycles on record have occurred in the last 50 years. We're just not used to this kind of deep calm."

Deep calm was fairly common a hundred years ago. The solar minima of 1901 and 1913, for instance, were even longer than what we're experiencing now. To match those minima in depth and longevity, the current minimum will have to last at least another year.

In a way, the calm is exciting, says Pesnell. "For the first time in history, we're getting to observe a deep solar minimum." A fleet of spacecraft � including the Solar and Heliospheric Observatory (SOHO), the twin probes of the Solar Terrestrial Relations Observatory (STEREO), and several other satellites � are all studying the sun and its effects on Earth. Using technology that didn't exist 100 years ago, scientists are measuring solar winds, cosmic rays, irradiance and magnetic fields and finding that solar minimum is much more interesting than anyone expected.

Modern technology cannot, however, predict what comes next. Competing models by dozens of solar physicists disagree, sometimes sharply, on when this solar minimum will end and how big the next solar maximum will be. The great uncertainty stems from one simple fact: No one fully understands the underlying physics of the sunspot cycle.

Pesnell believes sunspot counts should pick up again soon, "possibly by the end of the year," to be followed by a solar maximum of below-average intensity in 2012 or 2013.

But like other forecasters, he knows he could be wrong. Bull or bear? Stay tuned for updates.

NASA Joins 'Around the World in 80 Telescopes'

Fri, 03 Apr 2009 09:55:51 GMT

A collection of NASA missions will be involved in a live event Friday, April 3, that will allow the public to get an inside look at how these missions are run. "Around the World in 80 Telescopes" is a 24-hour webcast that is part of the "100 Hours of Astronomy" event for the International Year of Astronomy 2009.

During the webcast, viewers will be able to visit some of the most advanced telescopes on and off the planet. For NASA's space-based missions, the webcast will be broadcast from control centers throughout the United States. To view the webcast, visit http://www.100hoursofastronomy.org/component/content/article/34/75 .

As part of the webcast, most of the missions will release a never-before-seen image from the telescope or observatory. The new images can be found on the Web sites listed below. Please note these times correspond to the beginning of each mission's segment on the live webcast and when each new image will be available.

The NASA missions participating in the webcast, in chronological order, are (times are Pacific Daylight Time, April 3):

Hubble Space Telescope: 10:20 a.m. http://hubblesite.org/news/2009/14

Swift Gamma-ray Burst Explorer: 10:40 a.m. http://www.nasa.gov/swift

Fermi Gamma-ray Space Telescope: 11 a.m. http://www.nasa.gov/fermi

SOHO and TRACE: 12:20 p.m. http://sohowww.nascom.nasa.gov/ and http://sunland.gsfc.nasa.gov/smex/trace/

STEREO: 12:40 p.m. http://stereo.gsfc.nasa.gov/

Galaxy Evolution Explorer: 1:20 p.m. http://www.galex.caltech.edu/ and www.nasa.gov/galex

Chandra X-ray Observatory: 1:40 p.m. http://www.chandra.harvard.edu/photo/2009

Spitzer Space Telescope: 2:20 p.m. http://www.spitzer.caltech.edu/spitzer/index.shtml www.nasa.gov/spitzer

Kepler: 12:05 a.m. (April 4) http://kepler.nasa.gov

For information about the International Year of Astronomy, visit http://astronomy2009.nasa.gov/ .

For more information about NASA and agency programs, visit http://www.nasa.gov .

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, also in Pasadena. Caltech manages JPL for NASA. Graphics and more information about Spitzer are online at http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer .

Caltech leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. JPL manages the mission and built the science instrument. The mission was developed under NASA's Explorers ProgramSpace Flight Center, Greenbelt, Md. Researchers sponsored by Yonsei University in South Korea and the Centre National d'Etudes Spatiales (CNES) in France collaborated on this mission. Graphics and additional information about the Galaxy Evolution Explorer is online at http://www.galex.caltech.edu and http://www.nasa.gov/galex/ . and managed by the Goddard

NASA Flies to Greenland to Extend Polar Science

Wed, 01 Apr 2009 10:21:56 GMT

Imagine a piece of ice 1,000 miles long, 400 miles wide, and 2 miles thick in the center. That's the Greenland ice sheet. But that island-sized piece of ice is melting, so NASA researchers are flying to the Arctic this week to learn more about the nature of those changes.

Researchers led by William Krabill of NASA's Wallops Flight Facility in Wallops Island, Va., embark this week on a month-long airborne campaign to measure ice sheet and glacier thickness. They are using NASA's P-3B aircraft -- designed for heavy lifting and low-altitude flying -- outfitted with an array of science instruments. The plane is scheduled to transit March 30 from Virginia to Thule Air Base, Greenland. Weather permitting, the P-3B will make near-daily 8-hour flights over Greenland while pointing laser and radar instruments at targets until the mission's end on May 7.

Nearly every spring since 1991 Krabill has flown NASA research planes about 2,000 feet over Greenland to collect measurements of ice thickness. Now, as Krabill and colleagues return to update their measurements, their mission has become more extensive and more urgent because of global interest in the Arctic and the aging of a key ice-observing NASA satellite.

Measurements recorded by the radars and lasers will be compared and calibrated with measurements from the Ice, Cloud and land Elevation Satellite (ICESat), which makes regular, large-scale surface elevation measurements of polar ice sheets. Launched in January 2003, ICESat is already three years beyond its primary mission lifetime, so NASA scientists and engineers are making plans to bridge the anticipated gap until the launch of ICESat-II several years from now.

"It's research like this on sea ice and the Greenland ice sheet that we use to understand how the polar regions are connected to global climate change and discover what changes are going on in atmospheric and ocean circulations," said Tom Wagner, cryosphere program manager at NASA Headquarters in Washington, D.C.

Krabill pioneered observing techniques that have created a continuous record of ice sheet changes. He first came to Wallops as a summer student in 1967, and eventually worked with a group of engineers on early radar and laser systems and on research uses for the Global Positioning System (GPS). Krabill is credited with being the first to combine the two technologies and put them on an airplane to measure changes in ice thickness.

"I realized the capability of the instruments and saw a research need we could fulfill," Krabill said.

So far, flights led by Krabill have found evidence that, in general, ice along Greenland's coast is thinning while some areas inland are thickening. Still, the net change points to an overall loss. There's enough ice and snow in Greenland to raise sea level by about 7 meters (23 feet) if it were to all melt.

To determine long-term trends in the ice, scientists need sustained, highly accurate and well-calibrated measurements of thickness. Past and present observations combined with climate models are critical to understanding the future behavior of the Greenland ice sheet.

To achieve the thickness measurements, researchers use a combination of laser and radar instruments. Laser light from the Airborne Topographic Mapper is pulsed in circular scans on the ground, which reflect back to the aircraft and are converted into elevation maps of the ice surface. Meanwhile, the Pathfinder Airborne Radar Ice Sounder instrument, to be flown by researchers from the Johns Hopkins University Applied Physics Laboratory, emits radio signals that penetrate and "see" all the way through the ice, measuring the elevation of the land surface below. By combining elevation data for the top and base of the ice, and taking into account the aircraft's position using precise Global Positioning System (GPS) data, researchers can determine ice thickness at any given location.

A similar technique will be used to measure the thickness of a different target -- sea ice floating around Greenland and across the Arctic Ocean during a flight to Fairbanks, Alaska. Combining elevation data for the top of sea ice with sea level, researchers can use the known density difference between the sea and ice to estimate sea ice thickness.

"The big fear is that a lot of the multiyear ice is gone," Wagner said. "We hear stories about sea ice growing back. Well, it has grown back every winter, but it's really thin and may not last during the summer."

Krabill and colleagues will be joined on the flights by researchers from the University of Kansas, who are flying a "snow radar" that measures how snow builds up over time on ice, how that layer becomes compacted, and how it is changing.

The P-3B will fly routes that take it directly under the path of ICESat, allowing the satellite and plane to measure the same features. Each has its benefits: the satellite provides regular, continental-scale coverage of Greenland and hard-to-reach regions like Antarctica, while the aircraft can make more detailed surveys of areas where scientists expect to see rapid change.

"We need to do both because they both work together," Wagner said. Comparing the data collected simultaneously by aircraft and satellite also will help researchers use future aircraft flights to bridge the anticipated gap in satellite coverage should the ICESat mission end before ICESat-II is launched.