Posted on by Fraser Cain

NASA Assesses the Damage From Frances

NASA teams are surveying the Kennedy Space Center (KSC) for damage caused by Hurricane Frances. Initial assessments show KSC weathered the storm fairly well. There are no reports of any injured KSC workers, and there does not appear to be damage to the Space Shuttles Discovery, Atlantis, and Endeavour.

“Our initial feeling is we dodged a real bullet,” said Kennedy Space Center Director Jim Kennedy. “Even though this was the worst storm ever to hit KSC, I feel very fortunate.”

KSC will remain closed Tuesday for most employees. Workers who need to report to work will be notified. A more detailed damage assessment is expected Tuesday.

The most serious damage reported so far is to the center’s landmark structure, the Vehicle Assembly Building (VAB), and to the facility that manufactures Space Shuttle Thermal Protection System tiles and blankets.

Sustained wind of more than 70 mph was recorded during the storm. Approximately 1,000 panels were blown off the VAB. In some places, exterior panels and underlying sub-panels are missing, leaving the interior of the building exposed to the elements. There are several holes, including one estimated to be 50 feet by 50 feet, in the building. Emergency operations personnel have not entered the VAB, as several loose panels are still hanging from the building and present a safety hazard.

The KSC Space Shuttle tile and blanket facility’s roof is partially torn off, and there is significant wall damage. Damage to the facility and its effect on the Space Shuttle Return to Flight effort is not yet known. The building housing International Space Station hardware and modules appears to be in good shape. KSC was powered down last week as Frances approached. Emergency operations teams are working to restore electricity and phone service to the center. NASA will provide new information as available.

Original Source: NASA News Release

Posted on by Fraser Cain

Final Helios Report Released

The board that investigated the loss of the remotely operated Helios Prototype aircraft during a test flight last summer released its final report today.

The board determined that the mishap resulted from the inability to predict, using available analysis methods, the aircraft?s increased sensitivity to atmospheric disturbances such as turbulence, following vehicle configuration changes required for the long-duration flight demonstration.

The Helios Prototype aircraft involved in the mishap was a proof-of-concept solar electric- powered flying wing designed to operate at high altitudes for long duration flight. The failure occurred during a flight from the U.S. Navy?s Pacific Missile Range Facility (PMRF) on the Hawaiian island of Kauai on June 26, 2003.

The propeller-driven aircraft had been flying under guidance of ground-based controllers from AeroVironment, Inc., of Monrovia, Calif., the plane?s builder and operator, with assistance from NASA Dryden Flight Research Center personnel. The aircraft was destroyed when it sustained structural failure and fell into the Pacific Ocean. No other property damage or any injuries occurred as a result of the mishap.

The lightweight, highly flexible flying wing took off at 10:06 a.m. local time. At 10:22 and 10:24 a.m., the aircraft encountered atmospheric turbulence, typical of conditions expected by the test crew, causing abnormally high wing dihedral (upward bowing of both wingtips). Unobserved mild pitch oscillations began, but quickly diminished, according to post-test data analysis.

At about 10:36 a.m., the aircraft again experienced normal turbulence and transitioned into an unexpected, persistent high wing dihedral configuration. As a result, the aircraft became unstable, exhibiting growing pitch oscillations. Airspeed deviated from the normal flight speed, with the deviations rapidly increasing with every cycle of the oscillation. The aircraft?s design speed was subsequently exceeded. The resulting high dynamic pressures caused the wing leading edge secondary structure on the outer wing panels to fail and the solar cells and skin on the upper surface to rip off. The remotely piloted aircraft came down within the confines of the Pacific Ocean test range, northwest of PMRF.

?The mishap underscores our need to assess carefully our assumptions as we push the boundaries of our knowledge,? said Dr. Victor Lebacqz, Associate Administrator for NASA?s Office of Aeronautics. ?It should not, however, diminish the significant progress AeroVironment and NASA have made over the past 10 years in advancing the capabilities of this unique class of aircraft on many successful flights, including Helios’ record setting flight to just under 97,000 feet altitude in August 2001. It is important that we learn from this experience, and apply the board’s findings and recommendations to help ensure the payoffs of such vehicles are fully realized.?

The report is available on the Web at: http://www.nasa.gov/pdf/64317main_helios.pdf

Original Source: NASA News Release

Posted on by Fraser Cain

Astronauts Complete Final Spacewalk

Smoothly and ahead of schedule, Expedition 9 Commander Gennady Padalka and NASA Science Officer Mike Fincke completed the fourth and final spacewalk of their six-month mission today. Padalka and Fincke spent five hours, 21 minutes outside completing mainenance tasks and installing antennas to prepare for the initial arrival of a new European cargo ship next year.

Wearing Russian Orlan spacesuits, Padalka and Fincke began the spacewalk at 11:43 a.m. CDT, emerging from the Pirs airlock affixed to the Zvezda Service Module. It was Padalka?s sixth career spacewalk and the fourth for Fincke, all of his conducted during this expedition. The spacewalk was supervised by Russian flight controllers at the Mission Control Center in Korolev, outside Moscow.

After setting up tools and tethers, Padalka and Fincke quickly went to work. On the Zarya module, they replaced a pump control panel that measures the module’s coolant levels. They then installed a series of tether guides on four handrails. The guides are intended to prevent future spacewalkers? tethers from becoming snagged.

As the Station moved into orbital darkness, the spacewalkers took a rest break. During the break, flight controllers in Houston collected data on the orientation of the outpost. The information will help determine if the cooling systems of the Russian spacesuits contribute to changes in the Station?s orientation. Throughout today’s spacewalk, the Station remained in predicted orientations. No unanticipated measures were needed to maintain its stability.

Padalka and Fincke spent two and a half hours on the exterior of Zvezda, installing three communications antennas at its aft end. Those antennas, along with other equipment installed during an Aug. 3 spacewalk, will be used next year. They will guide the European Space Agency?s unpiloted Automated Transfer Vehicle (ATV), the “Jules Verne” cargo ship, to its maiden docking with the Station. Three more ATV navigation antennas will be installed by the next Station crew, Expedition 10, in February. The Expedition 11 crew will install ATV communications gear inside Zvezda as well.

Padalka and Fincke returned to Pirs and installed protective handrail covers at one of the two airlock hatches. The covers will ensure tethers do not inadvertently wrap around the handrails.

Fincke also photographed a suitcase-sized tray of Japanese commercial experiments mounted on Zvezda to measure the effect of micrometeoroids on a variety of materials. Called Micro-Particle Capturer and Space Environment Exposure Devices, they were installed on Zvezda almost three years ago.

With their work done, Padalka and Fincke returned to the airlock and closed the hatch at 5:04 p.m. CDT. The spacewalk was the 56th in support of Station assembly and maintenance and the 31st based from the Station. In all, Padalka and Fincke have spent 15 hours and 45 minutes outside the Station during their four spacewalks together. To date, spacewalkers have spent more than 338 hours outside the Station for maintenance and assembly work.

For information on the crew’s activities aboard the Space Station, future launch dates, as well as a list of opportunities to see the Station from anywhere on the Earth, visit:

http://spaceflight.nasa.gov/

For details on Station science operations provided by the Payload Operations Center at NASA’s Marshall Space Flight Center in Huntsville, Ala., visit:

http://scipoc.msfc.nasa.gov/

Original Source: NASA News Release

Posted on by Fraser Cain

Hubble Sees the Stingray Nebula

This is the Stingray Nebula (Henize 1357), the youngest known planetary nebula, as seen by the NASA/ESA Hubble Space Telescope. Twenty five years ago, the nebulous gas entombing the dying star at the centre was not hot enough to glow.

This image shows a rare moment in the final stages of a star’s life: a shell of gas cast off by a dying star which then begins to glow like a neon light bulb. Images of planetary nebulae in their formative years like this can yield new insights into the last moments of ordinary stars like our Sun.

A planetary nebulae forms after an aging, low-mass star swells to become a ‘red giant’ and blows off some of its outer layers of material. As the nebula expands away from the star, the star’s remaining core gets hotter and heats the gas until it glows. A fast wind – material propelled outward from the hot central star ? compresses the gas and pushes the gas bubble outward.

The Stingray Nebula is an ‘infant’ in relative terms, because only within the past 25 years did its central star rapidly heat up enough to make the nebula glow. While stars typically exist for millions of years, the transition to a visible planetary nebula takes only about 100 years ? the blink of an eye compared to a star’s lifetime – which is why no younger planetary nebulae have ever been identified.

Named because its shape resembles a stingray fish, the nebula is one-tenth the size of most planetary nebulae and is 18 000 light-years away in the direction of the southern constellation Ara (the Altar). Because of its small size, no details of the Stingray Nebula were visible before Hubble observations were first carried out in 1993. Those images were the first to show the structure of the nebula. This image was taken in 1997.

Original Source: ESA News Release

Posted on by Fraser Cain

Saturn’s Cool… Well, Its Rings Are

The Cassini spacecraft has taken the most detailed temperature measurements to date of Saturn’s rings. Data taken by the composite infrared spectrometer instrument on the spacecraft while entering Saturn’s orbit show the cool and relatively warm regions of the rings.

This false-color image shows that the temperatures on the unlit side of Saturn’s rings vary from a relatively warm 110 Kelvin (-261 degrees Fahrenheit, shown in red), to a cool 70 Kelvin (-333 degrees Fahrenheit, shown in blue). The green represents a temperature of 90 Kelvin (-298 degrees Fahrenheit). Water freezes at 273 Kelvin (32 degrees Fahrenheit).

The data show that the opaque region of the rings, like the outer A ring (on the far right) and the middle B ring, are cooler, while more transparent sections, like the Cassini Division (in red just inside the A ring) or the inner C ring (shown in yellow and red), are warmer. Scientists had predicted this might be the case, because the opaque ring areas would let less light through, and the transparent areas, more. These results also show, for the first time, that individual ringlets in the C ring and the Cassini Division are cooler than the surrounding, more transparent regions.

The temperature data were taken on July 1, 2004, shortly after Saturn orbit insertion. Cassini is so close to the planet that no pictures of the unlit side of the rings are available, hence the temperature data was mapped onto a picture of the lit side of the rings. Saturn is overexposed and pure white in this picture. Saturn?s moon Enceladus is visible below the rings, toward the center.

The composite infrared spectrometer, one of 12 instruments on Cassini, will measure infrared emissions from atmospheres, rings and surfaces. This spectrometer will create vertical profiles of temperature and gas composition for the atmospheres of Titan and Saturn. During Cassini?s four-year tour, the instrument will also gather information on the thermal properties and composition of Saturn?s rings and icy moons.

Cassini-Huygens is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science and Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA’s Goddard Space Flight Center, Greenbelt, Md.

For this image and for the latest news about the Cassini-Huygens mission, visit http://www.nasa.gov/cassini. For in-depth mission information, visit http://saturn.jpl.nasa.gov. For more information on the Composite Infrared Spectrometer, visit http://cirs.gsfc.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Getting Gravity Probe B Ready Was Tough

It’s “all systems go” for one of the most ambitious physics experiments ever attempted.

On August 27th, after four months in orbit, NASA’s Gravity Probe B satellite began its year-long hunt for signs of a subtle space-time vortex around Earth predicted by Einstein’s theory of relativity. The search isn’t going to be easy, but for scientists involved, one of the hardest parts is already over: months of delicately starting up and checking out the satellite, when one wrong move could have ruined the experiment before it ever got started.

“It’s a long and tortuous story,” says Francis Everitt, principal investigator for Gravity Probe B (GP-B) and a professor at Stanford University.

One of the key parts of GP-B is an onboard telescope that locks on to the star IM Pegasus, which serves as a fixed point of reference in the sky. Everitt and his colleagues had figured that pointing the telescope at that star would be quick and painless, taking only three days after the launch.

Instead it took weeks.

First, sunlight reflecting off floating dust particles confused the satellite’s star-tracking sensors. These sensors use the locations of constellations to orient the spacecraft, and the tiny shining specs looked like stars. The dust eventually cleared, but then another problem arose: Cosmic radiation in the form of high-speed protons peppered the telescope’s light sensor, causing false signals. Mission scientists had to tweak the satellite’s software to ignore these pulses. And on it went like this for weeks; scientists would solve one problem only to encounter another.

“Now it has become very routine, and we only take about a minute to acquire the star as we come up over the horizon,” Everitt says. (The satellite loses sight of the guide star during each orbit because it passes behind the Earth, so it must reacquire the star as it comes back into sight.)

The purpose of the telescope and the guide star is to help scientists keep track of four spinning spheres, or gyros, onboard the satellite. These gyros, which will be listed in a forthcoming edition of the Guinness Book of World Records as the roundest objects ever manufactured, are the heart of the experiment. In the beginning, their spin axes are aligned with IM Pegasus. If space-time around Earth is really twisted, as Einstein says, the gyros will wobble, slowly drifting out of alignment with the distant star during GP-B’s one-year mission.

“One of the things all of us were terribly worried about was getting some dirt in the gyro housings,” Everitt says. The gyros float a near-perfect vacuum, and only a thousandth-of-an-inch gap separates the spheres from their casings.

“The gyros were cleaned before they went up, but we gave this thing a tremendous vibration during launch. Wouldn’t you expect a piece of dirt to come in through one of the pump-out ports, land right on one of the gyros and jam it?” he says. “That would be the end of that gyro.”

This time all the worrying was for nothing. “The gyros have all been as clean as a whistle,” he says. They’re suspended in their casings, aligned with the guide star, and spinning thousands of times per minute. “Amazing, delightful.”

Now the gathering of science data begins. The satellite’s onboard computers should be able to handle this phase of the mission automatically. Still, at least one person will be on duty monitoring GP-B at all times throughout the year, Everitt says. “It should run itself, but you can never relax.”

After more than 40 years of methodical planning and four months of intense troubleshooting, GP-B’s scientists feel “a real sense of gladness,” he says. “What a difference it makes to be up there and operating. How thrilling that is. We all feel that.”

“Some people,” laughs Everitt, “are talking about taking a week or two of well-deserved vacation.”

Original Source: NASA Science News

Posted on by Fraser Cain

Envisat Watches Hurricane Frances

Hurricanes are one of those forces of nature that can only fully be captured by satellite imagery. For Hurricane Frances, currently thundering towards the United States coast, ESA’s Envisat is going one better, peering through the hurricane from top to bottom, even helping to ‘see’ under the waves to map hidden forces powering the storm.

As its 235-km-per-hour winds passed the Bahamas, Frances was heading for landfall on the Florida coast some time on Saturday, and three quarters of a million Americans are in the process of evacuating their homes. To wait and watch for Frances might be suicidal for human beings, but space-based observers such as Envisat observe its passage without danger.

“Because of Envisat’s multi-sensor capability, we can slice right through the hurricane with just a single satellite,” explained Jos? Achache, ESA Director of Earth Observation Programmes.

“Effectively Frances is taken apart for meteorologists to study. The data returned by Envisat includes cloud structure and height at the top of the hurricane, wind and wave fields at the bottom, sea surface temperature and even sea height anomalies indicative of upper ocean thermal conditions that influence its intensity.”

Important processes occur at a range of altitudes and locations throughout a hurricane – basically a large powerful storm centred around a zone of extreme low pressure.

Strong low-level surface winds and bands of intense precipitation combine with strong updrafts and outflows of moist air at higher altitudes, with energy released as rainy thunderstorms. Until now, the only reliable source of such high-resolution measurements at different altitudes was from aircraft flown directly through the hurricane.

Envisat carries both optical and radar instruments, enabling researchers to observe high-atmosphere cloud structure and pressure in the visible and infrared spectrum, while at around the same time using radar backscatter to measure roughness of the sea surface and so derive the wind fields just over it.

Those winds converging on the low-pressure eye of the storm are what ultimately determine the spiralling cloud patterns that are characteristic of a hurricane.

Florida-based scientists have begun to take advantage of this unique single-spacecraft combination of instruments ? the Medium Resolution Imaging Spectrometer (MERIS) and Advanced Synthetic Aperture Radar (ASAR) ? as hurricane season gets into full swing.

The University of Miami’s Centre for Southeastern Tropical Advanced Remote Sensing (CSTARS) ground station has an agreement to acquire ASAR and MERIS data direct from Envisat, with ERS-2 wind scatterometer data set to follow in the near future. Their access to Envisat data has come just as the second hurricane in less than a month is heading towards the Florida coast.

“With MERIS and ASAR, Envisat can image both the ocean and atmosphere pretty much simultaneously, which is a very useful capability during hurricane season,” said Hans Graber, Professor of Applied Marine Physics at the University of Miami and Co-Director of CSTARS.

While MERIS returns detail on the swirling clouds at the top of the hurricane, ASAR pierces right through the clouds to show the wind-wracked face of the sea beneath the storm.

“Specifically in terms of Frances, the eye of the hurricane seems to be rolling a lot right now from the top of the clouds, looking quite unstable, the information from an ASAR image should help localise its size and position on the ocean,” Graber said. “And wind fields around the eye wall can be derived from ASAR data ? right now all we have to go on are measurements from the hurricane hunter planes that fly right through the storm.”

Simultaneous MERIS and ASAR acquisitions are planned for Friday by CSTARS, even as the storm comes closer to predicted landfall the following morning.

“Our current activity is along the lines of a shakedown ? we’re investigating how this can be used,” added Graber. “Our final goal is to get this working on an operational basis during hurricane season. We have a deal to use radar data from the Canadian Space Agency, and also have access to other satellite resources for high temporal coverage of the affected region.

“The potential is there to extract a large amount of useful information which can help the US National Hurricane Center increase the accuracy of their hurricane predictions and reduce danger to the public.”

Another instrument aboard Envisat is being used to take the temperature of Frances, both down at the surface of the ocean and at the heights of its towering clouds.

Water temperatures are the main underlying energy reservoir powering Frances; together with the correct atmospheric conditions, they need to exceed 26?C in order to form and maintain a tropical cyclone. Envisat’s Advanced Along Track Scanning Radiometer (AATSR) works like a space-based thermometer, acquiring the temperature of the sea surface down to a fraction of a degree.

Meanwhile AATSR also returns useful atmospheric data, measuring the temperature of the top of hurricane clouds ? the higher into the atmosphere they extend, the colder they are – and also deriving their ice content.

“We produced a combined AATSR sea surface temperature and cloud top temperature image, which shows the sea surface temperature to be as high as 29?C in the area,” remarked Carsten Brockmann of Brockmann Consult, a German company processing both MERIS and AATSR hurricane imagery. “This two-sensor combination gives meteorologists a lot of information to help them understand the dynamics of the hurricane and better predict its development.”

AATSR information can be correlated with MERIS data cloud height and development to gain a good estimate of the hurricane’s precipitation potential, and improve understanding of how this relates to its overall intensity. Condensation of water vapour releases latent heat, which warms the vicinity of the hurricane eye. This in turn evaporates more surface water and feeds the heat engine powering the hurricane.

Studying hidden depths that fuel the storm
The thermal energy of warm water, which partly powers a hurricane, is known as tropical cyclone heat potential (TCHP).

Oceanic features, such as warm core rings, eddies, and the Gulf Stream, represent a source of enhanced heat fluxes to the atmosphere that may cause the strengthening of tropical cyclones, such as hurricanes.

Warm waters may extend to at least 100 meters beneath the surface in many of these oceanic features, representing waters of very high heat content. Several hurricanes have intensified when their tracks pass over eddies or other masses of warm water with high TCHP values.

For example, in 1995 Hurricane Opal suddenly intensified in the Gulf of Mexico after passing over a warm ring with TCHP values of up to six times the threshold to sustain a tropical cyclone.

Previously, researchers used sea surface temperature alone to estimate the role of the upper ocean thermal conditions on hurricane intensification. The problem with this is that the sea surface temperature measured by AATSR or comparable satellite instruments may not by themselves show these warm upper ocean features, particularly during summer months in tropical regions.

In the past these upper ocean features have gone unseen by satellite-based temperature sensors because they are effectively camouflaged beneath a very shallow and stable layer of warmer water.

Tropical cyclone wind forces easily erode this thin upper layer by mixing the upper waters to depths that may go down to 100 meters, giving the tropical cyclones the potential to absorb ocean thermal energy, if conditions are appropriate. Now, estimates of TCHP based on satellite observations of sea surface temperature and sea surface height can detect these features.

Researcher Gustavo Goni, Joaquin Trinanes and Peter Black of the US National Oceanic and Atmospheric Administration’s Atlantic Oceanographic and Meteorological Laboratory (NOAA/AOML) are working on this original methodology to detect these warm water masses and to compute their tropical cyclone heat potential values using several satellite sensors including one on Envisat.

“These water features are critical for identifying regions of high TCHP values that may potentially contribute to the intensification of a hurricane?, Goni explained. “These regions of high TCHP values provide the hurricanes with the opportunity to absorb much more thermal energy if overall conditions are right. My research is taking advantage of the fact that these warm water masses cause an upward elevation in ocean height of up to 30 cm. Such sea height anomalies can then be mapped with space-based radar altimeter data.”

Radar altimeters, such as the Radar Altimeter-2 instrument on Envisat, fire hundreds of radar pulses down to Earth every second, and by timing their return down the nanosecond can measure sea height to a maximum accuracy of two centimetres from hundreds of kilometres above the Earth.

The US Naval Research Laboratory (NRL) combines Envisat RA-2 data with data from similar radar altimeters aboard the Jason-1 and GFO satellites to enhance overall accuracy and spatial and temporal coverage, forming the source for altimetry products which, in turn, form the basis for NOAA/AOML-produced maps of tropical cyclone heat potential depicting the upper ocean thermal conditions, shown here overlaid against Hurricane Frances’ track so far.

“At this time I use this product only for research purposes, providing an enhanced understanding of the life of a hurricane. However, analogous products are being produced and used operationally for forecasting by the National Hurricane Center”, Goni concluded.

Altimetry-based wind speed and wave height products are also distributed by the French firm Collecte Localisation Satellites (CLS), and can reveal sea surface features related to the presence of hurricanes.

Envisat results to be revealed
Launched in March 2002, ESA’s Envisat satellite is an extremely powerful means of monitoring the state of our world and the impact of human activities upon it. Envisat carries ten sophisticated instruments to observe and monitor the Earth’s atmosphere, land, oceans and ice caps, maintaining continuity with the Agency’s ERS missions started in 1991.

After two and a half years in orbit, more than 700 scientists from 50 countries are about to meet at a special symposium in Salzburg in Austria to review and discuss early results from the satellites, and present their own research activities based on Envisat data.

Starting on Monday, the Envisat Symposium will address almost all fields of Earth science, including atmospheric chemistry, coastal studies, radar and interferometry, winds and waves, vegetation and agriculture, landslides, natural risks, air pollution, ocean colour, oil spills and ice.

There are over 650 papers being presented at the Symposium, selected by peer review. Presentations will include results on the Prestige oil spill, last year’s forest fires in Portugal, the Elbe flooding in 2002, the evolution of the Antarctic ozone hole, the Bam earthquake and pollution in Europe.

Numerous demonstrations are planned during the week in the ESA Exhibit area. An industrial consortium exhibit on the joint ESA-European Commission Global Monitoring for Environment and Security (GMES) initiative is also planned.

Original Source: ESA News Release

Posted on by Fraser Cain

Be Safe Florida

At the time I’m writing this, Hurricane Frances is bearing down on Florida, and should make landfall within the next 36 hours. More than a million people have been ordered to evacuate their homes to avoid what could be the worst hurricane in more than a decade to strike the coast. Unfortunately, it looks like NASA’s Kennedy Space Center is right on target for the storm, and it could be hit by the most powerful part, called the “north wall”. KSC has been evacuated, but the three space shuttles are secured in a building designed to survive winds of 168 kph (105 mph) – Frances has gotten to 233 kph (145 mph). It’s going to be a nailbiter.

If you live in the area, definitely follow the evacuation instructions. I hope everyone stays as safe as possible.

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Hot and Hotter

One of the Sun’s greatest mysteries is about to be unravelled by UK solar astrophysicists hosting a major international workshop at the University of St Andrews from September 6-9th 2004. For years scientists have been baffled by the ‘coronal heating problem’: why it is that the light surface of the Sun (and all other solar-like stars) has a temperature of about 6000 degrees Celsius, yet the corona (the crown of light we see around the moon at a total eclipse) is at a temperature of two million degrees?

Understanding our nearest star is important because its behaviour has such an immense impact on our planet. This star provides all the light, heat and energy required for life on Earth and yet there is still much about the Sun that is shrouded in mystery.

“The problem is like an Astrophysics X-file! It is totally counter intuitive that the Sun’s temperature should rise as you move away from the hot surface,” explains Dr Robert Walsh of the University of Central Lancashire and co-organiser of the workshop. “It is like walking away from a fire and suddenly hitting a hotspot, thousands of times hotter than the fire itself.”

Using the joint ESA/NASA satellite, the Solar and Heliospheric Observatory (SOHO), along with another NASA mission called TRACE, researchers have gathered enough data to form two rival theories to explain what has been termed ‘coronal heating’. It is now believed that the Sun’s strong magnetic field is the culprit behind this unique phenomenon. At this SOHO workshop, scientists from the UK and around the world will look at the evidence for these two explanations and try to untangle the clues we now have available to us.

Walsh continues, “SOHO’s contribution to the research has been so important because for the first time we can take simultaneous magnetic and extreme ultraviolet images of the Sun’s atmosphere, allowing us to study the changes in the magnetic field at the same time as the corresponding effect in the corona. Then, using sophisticated computer simulations, we have constructed 3d models of the coronal magnetic field that can be compared with SOHO’s observations.”

One possible mechanism for coronal heating is called ‘wave heating’. Prof Alan Hood from the Solar and Magnetospheric Theory Group at St. Andrews explains: “The Sun has a very strong magnetic field which can carry waves upwards from the bubbling solar surface. Then these waves dump their energy in the corona, like ordinary ocean waves crashing on a beach. The energy of the wave has to go somewhere and in the corona it heats the electrified gases to incredible temperatures.”

The other rival mechanism is dependent on twisting the Sun’s magnetic field beyond breaking point. Prof Richard Harrison of the UK’s Rutherford Appleton Laboratory says “The Sun’s magnetic field has loops, known to be involved in the processes of sun spots and solar flares. These loops reach out into the Sun’s corona and can become twisted. Like a rubber band, they can become so twisted that eventually they snap. When that happens, they release their energy explosively, heating the coronal gases very rapidly”.

The Sun is the only star astronomers can study in close detail and many questions remain. The workshop will also look forwards to future missions such as Solar-B, STEREO and Solar Orbiter that all have important UK involvement through PPARC.

Original Source: PPARC News Release

Posted on by Fraser Cain

Rover’s Grinder Working Again After Glitch

NASA’s Mars Exploration Rover Opportunity has resumed using its rock abrasion tool after a pebble fell out that had jammed the tool’s rotors two weeks ago.

The abrasion tool successfully spun a wire brush late Monday to scrub dust off two patches of a rock inside “Endurance Crater,” and engineering data received Tuesday confirmed that the tool is fully recovered. Rover wranglers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., plan to use the tool’s grinding rotor next to cut a hole exposing the interior of the rock.

“We’re delighted to be using Opportunity’s rock abrasion tool again,” said Dr. Stephen Gorevan of Honeybee Robotics, New York, lead scientist for that tool on both rovers. “We had planned to kick out that pebble by turning the rotors in reverse, but just the jostling of the rover’s movements seems to have shaken it loose even before we tried that. The rock abrasion tool has functioned beyond engineering expectations as a window for Mars Exploration Rover science. The new imaging consultation makes it clear that not only does the tool appear to be undamaged, but also that its teeth have not worn very much at all.”

Opportunity and its twin, Spirit, have each conducted more than four months of bonus exploration and discoveries after successfully completing their three-month primary missions on Mars. Opportunity’s rock abrasion tool has now been used 18 times to grind into rocks and five times to brush rocks. Spirit’s tool has ground nine times and brushed 28 times. The criteria set in advance for successful use of the abrasion tools was for each rover to grind at least one rock.

Mars and Earth are approaching the point in their orbits when Mars, on Sept. 16, will pass nearly behind the Sun, a geometry called “conjunction.” For several days around conjunction, the energetic environment close to the Sun will interfere with radio communications between the two planets. Rover operators have planned a hiatus in sending up daily commands. The rovers will use longer-term instructions to continue doing daily research and to attempt daily communications until the conjunction period is over.

“Based on experience with other spacecraft, we expect that when the Mars-Sun-Earth angle is 2 degrees or less, the ability to successfully communicate degrades rapidly,” said JPL systems engineer Scott Doudrick, who has been organizing conjunction operations for both rovers. “To be cautious, we’re allowing three days on either side of that period.”

The planned gap in sending daily plans runs for about 12 days beginning Sept. 8 for Spirit and Sept. 9 for Opportunity. The rovers will be instructed ahead of time to continue doing atmospheric operations and Moessbauer spectrometer readings daily during that period. No movements of the wheels or the robotic arms are in the conjunction-period plans, but the camera masts may move for making observations. The rovers also will continue communicating daily with NASA’s Mars Odyssey orbiter and will also attempt to communicate directly with Earth.

“The science team gets some time off from the daily planning cycle, but we will have a full spacecraft team every day, so we will be able to respond quickly if the rovers communicate a problem to us and there’s a good reason for emergency commands,” Doudrick said.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Science Mission Directorate, Washington. Additional information about the project is available from JPL at http://marsrovers.jpl.nasa.gov/ and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.

Original Source: NASA/JPL News Release