Posted on by Fraser Cain

Armadillo Aerospace Rocket Destroyed

Saturday was a perfect day for flying, so we went out to the 100 acres for a boosted hop. We had high expectations for success, since the vehicle had been operating perfectly on all tests so far.

After we loaded up the propellant and pressurized the vehicle, we ran into a problem. When I opened it up to 20% throttle for the warmup it looked like it cleared up fine, but the telemetry was only reading 100C, as if the hot pack hadn?t started heating. We were a long way from the vehicle, so we couldn?t really tell what was going on. I gave it a bunch of slugs of propellant until it finally started going up in temperature properly, but we had blown a lot of propellant out on the ground. Too much.

It finally reached operating temperature and we launched. We had only been operating this engine at hover thrust levels, so we had been a little concerned that it might be rough at full throttle. It was. It flew fine through the roughness, but when it started to throttle down after the two second boost to a 0.5 G positive acceleration level for the stabilization phase, the rough pulses kept passing both above and below the desired acceleration, keeping the engine from throttling down at full speed, resulting in it going a lot higher than intended (just under 600 feet high). It did finally get out of the rough stability zone into clear stabilization, but a couple seconds later, everything got quiet. It ran out of propellant.

It had not hit apogee yet, so the unstable vehicle immediately started rotating, hitting about 50 degrees / second. If the vehicle had been past apogee when it ran out, it probably would have just dropped feet first.

We had telemetry all the way to the time of impact, which matched the video perfectly, landing eight meters from the launch point. The vehicle hit the ground basically sideways, a little tail first. The bottom manway flange broke off the tank, and the 450 pound tank with 180 psi pressure still in it got punted about 200 yards away by the gas release. $35,000 of rocket is now a whole lot of primo Armadillo Aerospace Droppings. There are a few pipe fittings that survived, but that?s about it. Amazingly, even though the on-board camera was destroyed, the tape did survive with only some scuffed sections. It?s a good thing Doom 3 is selling very well?

From analyzing the telemetry (integrating the chamber pressure during the flight), it looks like it wasted two thirds of the propellant on the warmup. If it had lifted off with a normal warmup, it would have landed ok even with the rough throttling, but we would have been in violation of the 15 second burn time limit by the time it landed. There was twice as much propellant loaded as this flight should have required, which I thought was enough to cover any off-nominal conditions, but we obviously should have scrubbed when the warmup didn?t catch after the second or third try. We are going to look into getting a continuous capacitive level sensor next time so we can have a firm no-go line for liftoff. If anyone knows of a peroxide compatible (316 SS / Teflon / viton / eetc) capacitive sensor that runs off of 12v or 5v DC and can handle 300 psi (we may be willing to run past rated pressure if nexessary), let me know. Ideally we would want a 5V or 10V analog out, but we could live with a current sensor, or (with some begrudging) a serial port. We would like to mount it on the bottom of the tank instead of the conventional top location, but we don?t think that will be a problem.

The failure did give us some demonstration data that we always sort of wanted to get (but not that bad). The vehicle is absolutely, positively, NOT going to continue flying nose first when it loses active control. This should be blatantly obvious from the CG, but we had a WSMR engineer pushing us towards a NASA consultant to prove it. When it fails in the air, it just drops like a rock, landing very near the launch site. Rupturing a fiberglass tank doesn?t produce shrapnel, but it does drop kick the tank pretty good. This looked pretty close to an optimal 45 degree launch angle for the tank, so we have a pretty good idea what our safe distances should be.

We probably would have been able to save the vehicle if we had a rocket drawn parachute on board, but we are trying to have a pyro-free vehicle. A pneumatic drogue cannon might have been able to deploy a chute fast enough, but it would be a lot more debatable.

We cut the engine open with the plasma cutter to do a post-mortem, and found what had been causing the engine issues. The combination of the bottom catalyst retaining plate bowing down because it was only welded on the bottom and some catalyst escaping both out the bottom and some out the top (the top screen was burned through in a couple places) left the bottom catalyst not even completely covering the diameter of the engine. When we had the nozzle and cold pack cut off and the engine on its side, you could see right through the hot pack at the top. This explains the apparently clear exhaust at the start while the thermocouple was still reading only 100C, because the thermocouple was fairly short (we used to use a longer one, but the bowing of the retaining plate forced us to use a shorter one so we could still insert it) so it was in a stream around the edges that bypassed most or all of the hot pack catalyst (driving down the highway probably also settled the catalyst on the opposite side from the sensors), while much of the main flow was still being burned. The loosening catalyst is also almost certainly why this engine ?got rough? after we had been using it for a while.

The support plate bowing can be fixed by either making a full depth angle on the sides of the plate so the weld gets full side coverage, or actually weld the plate between two chamber sections, instead of inside a single chamber section. We are making new plates that are made with 1300 quarter inch holes instead of large water jet cut squares that are bridged by screens. This will let us completely avoid the screens altogether, and we are also going to tie the top and bottom plates around the hot pack together by putting quarter inch bolts through some of the quarter inch holes, and welding them together as a unit with the catalyst in between. This should fix the engine behavior.

Everything else operated perfectly, so we still feel good about the general configuration, but we have a number of improvements for robustness and operability that we will be making in the next vehicle we put together. A couple of the necessary items are fairly long lead times, so we are probably grounded for five weeks.

Original Source: Armadillo Aerospace Status Report

Posted on by Fraser Cain

Mars Express Relays Photos from Rovers

ESA?s Mars Express has relayed pictures from one of NASA’s Mars rovers for the first time, as part of a set of interplanetary networking demonstrations. The demonstrations pave the way for future Mars missions to draw on joint interplanetary networking capabilities. ESA and NASA planned these demonstrations as part of continuing efforts to co-operate in space exploration.

On 4 August at 14:24 CEST, as Mars Express flew over one of NASA?s Mars exploration rovers, Opportunity, it successfully received data previously collected and stored by the rover. The data, including 15 science images from the rover’s nine cameras, were then downlinked to ESA?s European Space Operations Centre in Darmstadt (Germany) and immediately relayed to the Mars Exploration Rovers team based at the Jet Propulsion Laboratory in Pasadena, USA.

NASA orbiters Mars Odyssey and Mars Global Surveyor have so far relayed most of the data produced by the rovers since they landed in January. Communication compatibility between Mars Express and the rovers had already been demonstrated in February, although at a low rate that did not convey much data. The 4 August session, at a transmit rate of 42.6 megabits in about six minutes, set a new mark for international networking around another planet.

The success of this demonstration is the result of years of groundwork and was made possible because both Mars Express and the Mars rovers use the same communication protocol. This protocol, called Proximity-1, was developed by the international Consultative Committee for Space Data Systems, an international partnership for standardising techniques for handling space data.

Mars Express was 1400 kilometres above the Martian surface during the 4 August session with Opportunity, with the goal of a reliable transfer of lots of data. Engineers for both agencies plan to repeat this display of international cooperation today, 10 August, with another set of Opportunity images.

?We’re delighted how well this has been working, and thankful to have Mars Express in orbit,? said Richard Horttor of NASA’s Jet Propulsion Laboratory, Pasadena, California, project manager for NASA’s role in Mars Express. JPL engineer Gary Noreen of the Mars Network Office said: ?the capabilities that our international teamwork is advancing this month could be important in future exploration of Mars.?

In addition, Mars Express is verifying two other operating modes with Opportunity and the twin rover, Spirit, from a greater distance. On 3 and 6 August, when Mars Express listened to Spirit, it was about 6000 kilometres above the surface. At this range it successfully tracked a beacon from Spirit, demonstrating a capability that can be used to locate another craft during critical events, such as the descent to a planet?s surface, or for orbital rendez-vous manoeuvres.

?Establishing a reliable communication network around Mars or other planets is crucial for future exploration missions, as it will allow improved coverage and also an increase in the amount of data that can be brought back to Earth,? said Con McCarthy, from ESA?s Mars Express project, ?the tracking mode will enable ESA and NASA to pinpoint a spacecraft?s position more accurately during critical mission phases.?

The final session of the series, scheduled for 13 August with Opportunity, will demonstrate a mode for gaining navigational information from the ?Doppler shift? in the radio signal.

Original Source: ESA News Release

Posted on by Fraser Cain

Cassini’s View of Rhea

This view of Saturn?s icy moon Rhea shows hints of its heavily cratered surface, including a bright feature near the terminator. Cassini was, at the time, speeding away from the Saturn system on its initial long, looping orbit.

The image was taken in visible light with the narrow angle camera on July 15, 2004, from a distance of about 5.1 million kilometers (3.2 million miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 90 degrees. The image scale is 31 kilometers (19 miles) per pixel. The image has been magnified by a factor of two to aid visibility.

The Cassini-Huygens mission 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 Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: CICLOPS News Release

Posted on by Fraser Cain

Japanese Solar Sail Launched

ISAS succeeded in deploying a big thin film for solar sail in space for the first time in the world.
ISAS launched a small rocket S-310-34 from Uchinoura Space Center in Kagoshima, Japan, at 15:15, August 9, 2004 (Japan Standard Time). The launch was the culmination of a historic new technology, the world-first successful full-fledged deployment of big films for solar sail.

A solar sail is a spacecraft without a rocket engine. It is pushed along directly by light particles from the Sun, reflecting off its giant sails. Because it carries no fuel and keeps accelerating over almost unlimited distances, it is the only technology now in existence that can one day take us to the stars.

Although both scientists and science-fiction authors have long foreseen it, no solar sail has ever been launched until now. It is because superlight material for thin film which could bear extremely critical environment in space. Now due to the development of material and production technology, we can utilize promising film materials for solar sail, and the experimental deployment trials toward realization of solar sail have been initiated in some countries.

The S-310 rocket which was launched from Uchinoura Space Center at 15:15 of August 9, 2004, carried two kinds of deploying schemes of films with 7.5 micrometers thickness. A clover type deployment was started at 100 seconds after liftoff at 122 km altitude, and a fan type deployment was started at 169 km altitude at 230 seconds after liftoff, following the jettison of clover type system. Both experiments of two types deployment were successful, and the rocket splashed on the sea at about 400 seconds after liftoff.

Original Source: JAXA News Release

Posted on by Fraser Cain

Hubble Instrument Fails

One of four science instruments aboard NASA’s Hubble’s Space Telescope suspended operations earlier this week, and engineers are now looking into possible recovery options.

The instrument, called the Space Telescope Imaging Spectrograph (STIS), was installed during the second Hubble servicing mission in 1997 and was designed to operate for five years. It has either met or exceeded all its scientific requirements.

Hubble’s other instruments, the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), the Advanced Camera for Surveys, and the Wide Field/Planetary Camera 2 are all operating normally.

The STIS instrument, which went into a suspended mode Tuesday, was not slated for replacement or upgrade as part of any future servicing mission.

NASA has convened an Anomaly Review Board to investigate the cause of the STIS problem and an investigation is underway to determine if the instrument is recoverable.

Preliminary findings indicate a problem with the +5V DC-DC power converter on Side 2, which supplies power to the mechanism’s electronics. STIS suffered a similar electrical malfunction in 2001 that rendered Side 1 inoperable.

A final decision on how to proceed is expected in the coming weeks as analysis of the problem progresses.

In the current observing cycle, STIS accounts for about 30 percent of all Hubble scientific observation programs. A “standby” list of peer reviewed and approved observing programs for the other science instruments on Hubble can be used to fill the observing time now available.

The high sensitivity and spatial resolution of STIS enabled astronomers to search for massive black holes and study star formation, planets, nebulae, galaxies, and other objects in fine detail.

STIS was developed jointly with Ball Aerospace under the direction of principal investigator Dr. Bruce E. Woodgate of the Laboratory for Astronomy and Solar Physics at NASA’s Goddard Space Flight Center, Greenbelt, Md.

Among the major scientific achievements made by scientists using STIS were:

? Independent confirmation of the age of the universe by finding the coolest and hence oldest white dwarf stars that exist in our galaxy
? Conducted an efficient census of galaxies to catalog supermassive black holes. The fraction of galaxies that prove to contain a central massive black hole has proven to be surprisingly large

– Made the first-ever measurements of the chemical composition of the atmosphere of an extrasolar planet
– Saw the magnetic “footprints” of the Jovian satellites in Jupiter aurora, and made clear images of Saturn’s aurora
– Studied the dynamics of circumstellar disks, the region around young stars where planets may form
– Found the first evidence of the high-speed collision of gas in the recent supernova remnant SN1987A

Additional information about STIS is available on the Internet at:

http://hubble.nasa.gov/servicing-missions/sm2.html

Original Source: NASA News Release

Posted on by Fraser Cain

X Prize Contender’s Rocket Explodes

Space Transport Corp., a competitor for the $10 million Ansari X Prize, suffered a major setback on Sunday when their rocket – Rubicon 1 – exploded shortly after takeoff from a launch pad in Northwest Washington State. The 7-metre (23-foot) long spacecraft was supposed to go as high as 6.4 km (4 miles) and reach a speed of 1,800 kph (1,100 mph). One of the rocket’s two engines exploded on the launch pad, but the second still carried it into the air, where it tore itself apart. Rubicon 1 has been developed on a shoestring budget – it only cost $20,000 – and another should be ready to go in the next month or so.

Posted on by Fraser Cain

NASA’s Robonaut Can Move Around Now

Human-like hands, fingers and even television camera eyes have been hallmarks of NASA’s Robonaut, but recent work seeks to give the nimble robot legs, or at least a leg, and even wheels.

Robonaut took its first steps recently during tests at the Johnson Space Center in Houston, using a single “space leg” to move around the outside of a simulated Space Station. Other recent tests put the humanoid robot on wheels, a Segway scooter to be exact, and let it take to the road.

In either configuration, Robonaut?s head, torso, mechanical arms and hands maintain their ability to use the same space tools as humans. In the tests using its “space leg,” Robonaut commuted like a futuristic construction worker hand-over-hand outside a mock spacecraft. Aboard the gryo-stabilized wheels, it glided from one test station to another as its descendants might someday on the surface of the Moon or Mars.

Tests with the leg confirmed that Robonaut could climb around the outside of a spacecraft using handholds and plant its foot at a work site to make repairs or install parts. NASA?s goal is to build robots that could ?live? on the outside of spacecraft, ready for routine maintenance or emergencies. Humans inside the spacecraft would operate Robonaut with wireless controls.

The wheeled tests provided initial proof of concept for planetary Centaurs that merge humanoid robots with rovers. Those tests put Robonaut through its paces while mounted on a Segway Robotic Mobility Platform. They showed that a single teleoperator could simultaneously control both the robot?s mobility and dexterity with a wireless control system.

The climbing tests were a significant step in Robonaut?s development, proving the system?s capability for climbing, stabilizing and handling extravehicular activity (EVA) tools and interfaces in the space environment. The test featured a battery-powered, wireless Robonaut system mounted to an air-bearing sled, floating on a cushion of air, to eliminate friction and emulate the sensations experienced by astronauts working in zero gravity. Robonaut climbed using EVA handrails and plugged its stabilizing ?space leg? into a standard space station WIF (Worksite Interface Fixture) socket, while its operators drove Robonaut?s multiple limbs using innovative new telepresence controls.

?This test proved Robonaut can be operated wirelessly using an interchangeable base for different stabilization and locomotion systems — and it did it in a frictionless, space-like environment,” said Test Conductor Dr. Robert Ambrose of JSC?s Automation, Robotics and Simulation Division. ?These are all key capabilities needed for the development of future ?EVA squads? that leverage the combined talents of humans and robots to make vast improvements in spacewalk productivity.?

The Robonaut Project, which Ambrose leads, is a collaborative effort with the Defense Advanced Research Projects Agency (DARPA), and has been under development at JSC for several years. There are two Robonauts, each with highly dexterous hands that can work with the same tools humans use. Operators remotely control movements of the Robonauts? heads, limbs, hands and twin cameras through a combination of virtual-reality interfaces and verbal commands, relayed either through dedicated cabling or wireless systems.

In order to move about in a zero-gravity environment, a robot must be able to climb by itself, using gaits that smoothly manage its momentum and that minimize contact forces while providing for safety in the event of an emergency. To access worksites aboard the International Space Station and future spacecraft, robots must interact with spacewalking aids designed for humans including tethers, handrails and work anchors.

?The tests were very successful,? Ambrose said. ?The Robonaut team learned which climbing maneuvers are more feasible than others, and tested automated software safety reactions using the robot?s built-in force sensors. We also identified new opportunities for using these sensors in semi-automatic modes that will help operators across short (1-10 second) time delays. Our team will continue to tackle these challenges as NASA looks forward to applying human-robotic interaction to the tasks associated with returning to the Moon and going on to Mars.?

Learn more about Robonaut on the Internet at:

robonaut.nasa.gov

Original Source: NASA News Release

Posted on by Fraser Cain

Envisat Sees the Earth Changing in Real Time

Originally developed to pinpoint attacking aircraft during World War Two, today’s advanced radar technology can detect a very different moving target: shifts of the Earth’s crust that occur as slowly as the growth of your fingernails.

Radar data from satellites such as ESA’s Envisat are used to construct ‘interferograms’ that show millimetre-scale land movements. These rainbow-hued images provide scientists with new insights into tectonic motion, and an enhanced ability to calculate hazards arising when this slow motion speeds up, in the form of earthquakes or volcanic activity.

The ten-instrument payload on Envisat includes an Advanced Synthetic Aperture Radar (ASAR) instrument designed to acquire radar images of the Earth’s surface. Part of Envisat’s assigned ‘background mission’ as it orbits the world every 100 minutes is to prioritise ASAR acquisitions over the seismic belts that cover 15% of the land surface.

“By the time Envisat completes its nominal five-year mission we should have a satisfactory amount of images across all the seismic belts,” said Professor Barry Parsons of the Centre for the Observation and Modelling of Earthquakes and Tectonics at Oxford University.

“To detect the fine ground deformation we are interested in, we require repeated radar images of each site. We then combine pairs of images together using a technique called SAR interferometry, or InSAR for short, to show up any change between acquisitions.” (For more information see link: How does interferometry work?)

To accurately measure the slow build up of strain as tectonic plates move against each other along Earth’s seismic belts, multiple interferograms are combined, requiring many individual SAR images.

“The reason for this is to minimise any atmospheric interference, relative to the small crustal deformation signal we are interested in,” added Parsons. “Using data from Envisat’s predecessor ERS, our group has recently measured tectonic movement across western Tibet with an accuracy of a few millimetres per year. The results show that slip rates across the major faults in the region are much smaller than had been previously thought and that the Tibetan plateau deforms like a fluid.”

InSAR can also be used to analyse much more abrupt ground motion: researchers have recently been employing Envisat data to chart ground deformation associated with the extremely active Piton de la Fournaise volcano on R?union Island in the Indian Ocean, and to identify the fault that caused Iran’s Bam earthquake in December 2003.

Finding fault after the Bam disaster
More than 26000 people were killed on 26 December 2003, when a 6.3 Richter scale earthquake devastated the Iranian oasis town of Bam. Its ancient citadel ? designated a World Heritage site ? collapsed into rubble. The Charter on Space and Major Disasters was activated so that spacecraft including Envisat acquired imagery to support international relief efforts.

Following Envisat’s background mission, a pre-earthquake image had been acquired of the Bam vicinity on 3 December 2003, and this was combined with a post-quake image acquired 7 January 2004 ? the earliest re-acquisition date possible due to Envisat’s 35-day global coverage ? to perform InSAR.

“This is the first time that Envisat data has been used to produce an interferogram following a major earthquake,” said Parsons, part of an international team studying the Bam quake including participants from the Geological Survey of Iran and the US Jet Propulsion Laboratory.

The results were surprising, establishing that while Bam lies in a seismic belt, this particular quake had come from a point no one had expected. Iran is like the filling in a geological sandwich as the Arabian plate advances into Eurasia, and so many seismic faults occur within its territory. Most notably, the Gowk fault located west of Bam has had several large quakes take place on it during the last two decades.

However the Envisat interferogram showed the Bam quake had resulted from the rupture of a previously undetected fault that extends under the southern part of town, its existence missed by ground surveys. The fault showed up as a distinct band of discontinuity in the interferogram, with motion either side of it ranging from around five up to as high as 30 centimetres.

As well as highlighting such surface changes, InSAR results can be used to indirectly peer beneath the ground, with software models calculating what geological occurrences fit the surface events. With Bam they found a slip exceeding two metres had taken place at a mean depth of 5.5 kilometres, along a distinct type of fault.

Coming around again
The more precisely a spacecraft’s position can be controlled, the smaller the InSAR image baseline – the spatial distance between initial and follow-up image acquisitions – and the better the quality of the final interferogram. During Envisat’s initial Bam revisit the baseline was large enough that ERS digital elevation data was needed to subtract topographic effects caused by a shifted view angle.

However for its subsequent revisit, 35 days later, the steering of the spacecraft was so precise that no topographic compensation was required, representing a formidable operational achievement for Envisat.

“Our Flight Dynamics team have computed an accuracy of 93 cm using precise orbit determination results from DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) and laser ranging observations,” stated Envisat Spacecraft Manager Andreas Rudolph.

“Special orbit manoeuvres were required to achieve this accuracy, along with hard work from teams at the European Space Operations Centre (ESOC) here in Germany and the European Space Research Institute (ESRIN) in Italy ? not to mention a bit of luck!”

Surveying an active volcano
Radar interferometry is used to study earthquakes as well as volcanoes – Envisat has been gathering data on one extremely lively example of the latter.

Standing 2631 metres above the Indian Ocean, the Piton de la Fournaise volcano is not situated along seismic belts or the associated ‘Ring of Fire’ but ? like Hawaii on the other side of the planet ? it is sited above a magma ‘hotspot’ in the Earth’s mantle.

The Institut de Physique du Globe de Paris (IPGP) operates an in-situ Volcano Observatory to monitor eruptions and associated activity.

“We have been observing this basaltic volcano for the last 25 years ? it is one of the most active volcanoes in the world,” commented Pierre Briole of IPGP. “In the last six years there have been 13 eruptions, with an average duration of one month. Between 1992 and 1998 was a quiet time, while eight eruptions occurred between 1984 and 1992.”

Deep subterranean processes drive surface volcanic activity ? lava fissures and eruptions occur because of lava channels or ‘dikes’ that extend up from high pressure magma chambers. Ground deformation either up or down in the vicinity of a volcano provides insights into what is taking place underground, but until recently the amount of ground points that could be measured was very limited.

“Back in the time of ground-based geodetic instruments it took several weeks to measure the coordinates of perhaps 20 points, to an accuracy of about one centimetre,” remembered Briole. “Then in the early 1990s came the Global Positioning System (GPS). Using GPS we could increase the number of points measured tenfold during a weeklong campaign, down to half-centimetre accuracy. But the ground deformation caused by an eruption is typically extremely localised in space, and these 200 points are spread out across the volcano’s area.”

It took another space-based technology to improve on GPS: interferograms of Piton de la Fournaise, based on more than 60 Envisat images acquired during the last year. IPGP is part of a team making use of the data that also includes participants from Blaise Pascal (Clermont-Ferrand II) and R?union Universities.

“We are lucky with Piton de la Fournaise, because its remote location in the middle of the ocean means there are no clashes with other potential Envisat targets, and so we get more acquisitions than most of the other users of ASAR imagery,” Briole added. “InSAR from Envisat has proved an extremely powerful tool for us, because it provides a very high density of information across the entire volcano.

“With new eruptions taking place so often our ground campaigns could not keep pace but interferometry gives us data on each eruption. And while the volcano is very difficult place to operate in ? often with poor visibility from the weather and a very steep eastern flank ? all parts of the volcano down to vegetation line are accessible with InSAR.”

InSAR reveals a pattern of ground inflation in the months preceding a new eruption, as pressure in the magma chamber increases. Following an eruption the pressure abates and deflation occurs.

Also revealed are localised deformations that occur as magma dikes propagate and reach the surface. The extent of the deformation associated with a new fissure indicates the depth at which it originates ? the wider the inflation, the deeper down the dike has come from.

InSAR volcanic monitoring was first established using ERS data, producing interferograms showing Italy’s highly-active Mount Etna appearing to ‘breathe’ between eruptions. And interferogram surveys of apparently extinct volcanoes along remote parts of the Andes have shown ground motion indicating some are in fact still active.

“There are plenty of interesting lines of enquiry using this technique, including the question of whether it is possible to predict when a volcano is going to erupt, and – with seismic faults often occurring near volcanoes – the question of whether seismic activity and volcanic eruptions are linked,” Briole added.

“For now our team are interested in characterising Piton de la Fournaise as accurately as we can, to perfect techniques we can later apply to volcanoes elsewhere and if possible to increase the number of acquisitions so as to demonstrate that InSAR monitoring of volcanoes has operational potential, providing early warning for civil protection authorities.”

Original Source: ESA News Release

Posted on by Fraser Cain

Detailed Picture of Stormy Saturn

Details in Saturn?s southern polar region highlight the often turbulent nature of the interfaces that separate the cloud bands on this swirling gaseous globe.

The image was taken with the narrow angle camera on July 13, 2004, from a distance of 5.1 million kilometers (3.2 million miles) from Saturn through a filter sensitive to wavelengths of infrared light centered at 889 nanometers. The image scale is 30 kilometers (19 miles) per pixel. Contrast has been enhanced slightly to aid visibility.

The Cassini-Huygens mission 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 Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: CICLOPS News Release

Posted on by Fraser Cain

Dwarf Galaxies Have Been Through a Lot

Astronomers have shown for the first time that even the smallest galaxies in the Universe have complex structures that indicate a complex history. Using the Subaru Telescope, a team of astronomers from the National Astronomical Observatory of Japan, the Institute of Physics in Lithuania, the University of Durham, Paris Observatory, Kyoto University, Gunma Astronomical Observatory, and the University of Tokyo have discovered an extended halo of stars with a sharp cutoff in the dwarf irregular galaxy Leo A, a member of the Local Group of galaxies that includes the Milky Way. The discovery challenges current scenarios of galaxy formation by showing that instead of being the preservers of pristine building blocks that combined to form larger galaxies, dwarf irregular galaxies have their own history of build-up.

Understanding galaxy formation and evolution on time scales comparable to the age of the Universe is one of astronomy’s greatest challenges. In the scenarios of standard cosmology (Note 1), galaxies are built up via hierarchical merging: small primordial density fluctuations in the smooth distribution of matter in the early Universe grow and combine to form larger structures like the Milky Way. The most numerous type of galaxies in the universe — dwarf irregular galaxies (Note 2) — are supposed to preserve their properties unchanged over billions of years and represent pristine primeval building blocks. This is one reason why astronomers have recently been studying dwarf irregular galaxies with great interest.

The team led by Professors Nobuo Arimoto (National Astronomical Observatory of Japan) and Vladas Vansevicius (Institute of Physics, Lithuania) has studied Leo A — an isolated and extremely gas rich dwarf irregular galaxy with only 0.01% of the mass of the Milky Way and a low fraction chemical elements produced by earlier generations of stars. These characteristics suggest that this galaxy has been evolving without significant interaction with other galaxies. This galaxy has been believed to have quite a simple structure, in contrast to large disk galaxies like the Milky Way. However, this view needs to be changed due to deep imaging of the outer regions of this galaxy with the Subaru Telescope.

Prior to these observations, Leo A was already known to have a large angular size (7′ x 5′; Note 3) and Subaru Telescope equipped with its Prime Focus Camera (Suprime-Cam) was an ideal instrument to study the stars at the galaxy’s outer limits (Fig. 1). A single exposure with Suprime-Cam covers a field of view of 34′ x 27′ (pixel size 0”.2 x 0”.2) with high sensitivity. The team acquired optical images of the dwarf irregular galaxy Leo A with three broad band filters in November 2001. In order to trace the entire extent of the old stars in Leo A, the team employed red giant branch (RGB) stars which are evolved low-mass stars with very high luminosity and are expected to represent well the extended structures of galaxies. They investigated inside an ellipse of semi-major axis a = 12′ which fully covers the galaxy, and detected 1394 RGB stars distributed symmetrically and smoothly within this field.

Fig. 2 shows the radial profile of the surface number density of the red giant stars. The team found significantly larger disk structure (with a semi-major axis of 5.5′) than previously known (3.5′). Moreover, the deep observations permitted the discovery of a new stellar component in dwarf irregular galaxies, which the team calls a ?halo? (5.5′-7.5′), which has a less steep slope in the number density of RGB stars. The halo component ends at 8′ from the center of the galaxy with a sharp cutoff in the RGB star distribution. The existence of such a halo structure in dwarf irregular galaxies had been unconfirmed before these observations.

The size of Leo A revealed by these new observations is twice as large as its previously accepted size, suggesting that even in the nearby universe we see galaxies only as ?tips of icebergs” that are actually a few times more extended.

The newly discovered halo with a sharp stellar cutoff and the disk of the dwarf irregular galaxy Leo A closely resembles the structure as well as stellar and gaseous content found in large full-fledged disk galaxies like the Milky Way. The complicated structure of large massive galaxies has been believed to be a result of the merging of less massive galaxies like dwarf irregular ones. However, this study clearly reveals that the dwarf irregular galaxy Leo A already has disk and halo components, and suggests complex build-up histories for even very low mass galaxies like Leo A, which are supposed to form directly from the primordial density fluctuations in the early universe (Note 1), and challenges contemporary understanding of galaxy evolution. Professors N. Arimoto and V. Vansevicius believe Leo A is a ?Rosetta stone? (Note 4) for understanding the process of galaxy formation and evolution.

The scientific paper on this research has been accepted for publication in the August 20, 2004, Astrophysical Journal Letters (Volume 611, Number 2, L93).

Original Source: Subaru News Release