Crater Holden and Uzboi Vallis on Mars

140-km wide crater Holden, taken by Mars Express. Image credit: ESA. Click to enlarge.
This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA?s Mars Express spacecraft, shows the outlet channel of the Uzboi Vallis system into Crater Holden on Mars.

The HRSC obtained this image during orbit 511 with a ground resolution of approximately 45 metres per pixel. The scene shows the region of Noachis Terra, over an area centred at about 26? South and 325? East.

The valley of Uzboi Vallis begins in the region of Argyre Planitia and crosses the southern highlands in the direction of the northern lowlands. It connects several large impact craters, such as the 140 kilometre-wide Crater Holden seen in the main image.

Due to a layer of haze close to the base of Holden, the area within the crater appears lighter coloured and slightly less detailed than the surrounding area.

A small, dark dune-field can be seen in the eastern half of the crater floor. It indicates the role of wind in the morphological evolution of Crater Holden.

The terrain within Crater Holden is the result of a long and varied evolution. The numerous smaller craters inside Holden indicate that the crater is old.

Many smaller craters on the floor of Holden are covered with sediments, which were deposited after the formation of these craters and indicate that they are older than the unfilled small craters.

The central mount of Holden is partly hidden, because it has also been covered by sediments. The rim of the crater has been cut by gullies, which sometimes form small valley networks.

In the southern part of Crater Holden, well-preserved ?alluvial fans? (fan-shaped deposits of water-transported material) are visible at the end of some gullies (see close-up left).

In other parts of the crater rim, the alluvial fans are less distinct and partly covered by younger ?talus? cones (cone-shaped piles of debris from rock falls at the base of slopes).

Uzboi Vallis enters Crater Holden from the south-west. Two distinct phases of its development can be seen. In the first phase, a valley was formed up to 20 kilometres wide.

Later, a smaller channel was cut into the valley floor. The end of the small channel has been blocked by a landslide from the crater rim (see close-up 2).

The deepest parts of the valley floor are more than 1600 metres below the surrounding area. The numerous valleys at the flanks of Uzboi Vallis indicate that water probably played a major role in the formation and evolution of this region. Most of the valleys have been covered by younger sediments, indicating they have been inactive in recent geological time.

Original Source: ESA News Release

Deployment of Second MARSIS Boom Delayed

The MARSIS boom on Mars Express will help search for underground sources of water. Image credit: ESA. Click to enlarge.
The deployment of the second antenna boom of the Mars Express Sub-Surface Sounding Radar Altimeter (MARSIS) science experiment has been delayed pending investigation of an anomaly found during deployment of the first antenna boom.

The anomaly was discovered on 7 May towards the end of the first deployment operations. Deployment of the first boom started on Wednesday 4 May. The problem with the boom was confirmed by flight control engineers working at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany, on 7 May, after which further activity was stopped pending a full assessment of the situation.

The decision to delay deployment of Boom 2 pending clarification of the situation and implications was made on 8 May.

Mission controllers were able to determine that 12 of the 13 boom segments of Boom 1 were correctly locked into position. However, one of the final segments, possibly No. 10, had deployed but was not positively locked into position.

It was determined that deployment of the second boom should be delayed in order to determine what implications the anomaly in the first boom may have on the conditions for deploying the second.

This decision is in line with initial plans which had allowed for a delay should any anomalous events occur during the first boom deployment.

Mission staff will now take the time necessary to investigate the boom situation. Foreseen outcomes include confirming that all segments of Boom 1 have been locked into place and determining how the deployment of Boom 1 may affect that of Boom 2.

All efforts will be made to ensure the safety of the spacecraft overall and to minimise any effects on the operations of ongoing science activity on board Mars Express.

The MARSIS experiment is to map the Martian sub-surface structure to a depth of a few kilometres. The instrument’s 40-metre long antenna booms will send low frequency radio waves towards the planet, which will be reflected from any surface they encounter.

MARSIS is one of seven science experiments carried on board Mars Express, one of the most successful missions ever flown to the Red Planet. Mars Express was launched on 2 June 2003 and entered Mars orbit in December 2003.

Original Source: ESA News Release

Did Phoebe Come from the Outer Solar System?

Saturn’s moon Phoebe, imaged by Cassini when it first arrived. Image credit: NASA/JPL/SSI. Click to enlarge.
Saturn’s battered little moon Phoebe is an interloper to the Saturn system from the deep outer solar system, scientists have concluded. The new findings appear in the May 5 issue of the journal Nature.

“Phoebe was left behind from the solar nebula, the cloud of interstellar gas and dust from which the planets formed,” said Dr. Torrence Johnson, Cassini imaging team member at NASA?s Jet Propulsion Laboratory, Pasadena, Calif. “It did not form at Saturn. It was captured by Saturn’s gravitational field and has been waiting eons for Cassini to come along.”

Cassini flew by Phoebe on its way to Saturn on June 11, 2004. Little was known about Phoebe at that time. During the encounter, scientists got the first detailed look at Phoebe, which allowed them to determine its makeup and mass. With the new information they have concluded that it has an outer solar system origin, akin to Pluto and other members of the Kuiper Belt.

“Cassini is showing us that Phoebe is quite different from Saturn’s other icy satellites, not just in its orbit but in the relative proportions of rock and ice. It resembles Pluto in this regard much more than it does the other Saturnian satellites,” said Dr. Jonathan Lunine, Cassini interdisciplinary scientist from the University of Arizona, Tucson.

Phoebe has a density consistent with that of the only Kuiper Belt objects for which densities are known. Phoebe?s mass, combined with an accurate volume estimate from images, yields a density of about 1.6 grams per cubic centimeter (100 pounds per cubic foot), much lighter than most rocks but heavier than pure ice, which is about 0.93 grams per cubic centimeter (58 pounds per cubic foot). This suggests a composition of ice and rock similar to that of Pluto and Neptune’s moon Triton. Whether the dark material on other moons of Saturn is the same primordial material as on Phoebe remains to be seen.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA’s Science Mission Directorate, Washington, D.C. For Phoebe images and more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

Original Source: NASA/JPL News Release

Mars Polar Lander Found?

Is this the Mars Polar Lander? Image credit: NASA/JPL. Click to enlarge.
The loss of Mars Polar Lander in December 1999 was a traumatic experience not only for those of us intimately involved in the mission, but also for the U. S. Mars Exploration Program. Following the failure, exhaustive reviews of what happened and why led to major shifts in the way planetary exploration was implemented. Without telemetry, the cause of the failure could only be surmised. It would be extremely important if, through some observation, it were possible to confirm the failure mode.

Shortly after the loss of Mars Polar Lander (MPL), the Mars Global Surveyor MOC was employed to acquire dozens of 1.5 m/pixel images of the landing uncertainty ellipses, looking for any evidence of the lander and its fate. The criteria we used in searching for MPL required a bright feature of irregular or elongated shape (the parachute) within about 1 kilometer (0.62 miles) of a location that included a dark area (rocket-disturbed martian dirt) and a small, bright spot near its center (the lander). In 2000, we found one example (see figure) that met these criteria, but in the absence of any substantive, corroborating evidence, the interpretation that this was MPL and its parachute were considered to be extremely speculative.

Observations by MGS MOC in 2004 of the Mars Exploration Rover (MER) landing sites provided guidance for a re-examination of the previously identified MPL candidate. For example, the material from which the MPL and MER parachutes are made is similar, and its brightness in MOC images can be calculated, at least in a relative sense, as a function of sun angle. The brightness of the candidate “parachute” in the MPL candidate location image turns out to be consistent with it being the same material. The brightness difference of the ground disturbed by rocket blast at the MER sites is similar to the brightness difference seen in the MPL candidate image, again adjusted for the difference in illumination and viewing angles. These consistencies lend credibility to this tentative identification.

If these features really are related to the MPL landing, what can we surmise about that landing from the image? First, we can tell that MPL’s descent proceeded more-or-less successfully through parachute jettison and terminal rocket firing. The relative location of the candidate parachute and lander is consistent with the slight west-to-east wind seen in dust cloud motion in the area around the date of landing. The blast-disturbed area is consistent with the engines continuing to fire until the vehicle was close to the ground. How close is not known. The larger MER retrorockets fired at about 100 m altitude and continued firing until the engines were about 20-25 m above the surface; the candidate MPL disturbance is roughly the same size, but whether this means the engines were firing as close to the ground as the MER rockets cannot be determined. These interpretations are consistent with the proposed MPL mode of failure: the engines fired at the correct time and altitude and continued firing until the flight software checked to see if an electronic message indicated that the landing leg contact switch had been set. Since the initial leg deployment several kilometers above the surface apparently induced sufficient motion to trigger this message, the software stopped the engines as soon as the check was made, about 28-30 seconds into the 36-40 second burn. MPL was probably at an altitude of about 40 m, from which it freely fell. This is equivalent to a fall on Earth from a height of about 40 feet. The observation of a single, small “dot” at the center of the disturbed location would indicate that the vehicle remained more-or-less intact after its fall.

What is important about having a candidate for the Mars Polar Lander site? It gives the MOC team a place to target for a closer look, using the compensated pitch and roll technique known as “cPROTO.” Examples of cPROTO images and a description of this capability, developed by the MGS team in 2003 and 2004, were discussed in a MOC release on 27 September 2004. Without a candidate for targeting a cPROTO image, it would take more than 60 Earth years to cover the entire Mars Polar Lander landing ellipse with cPROTO images, because the region spends the better part of each Mars year covered with carbon dioxide frost, part of each winter is spent in darkness, and, because of several uncertainties involved with the technique, it often takes two, three, or more tries before a cPROTO image hits a specific target. Now that a candidate site for Mars Polar Lander has been identified, we have a cPROTO target, which may permit us to obtain an image of about 0.5 meters per pixel (allowing objects approximately 1.5-2.5 meters in size to be resolved) during southern summer this year. At the present time (May 2005), the landing site is just beginning to lose its cover of seasonal carbon dioxide frost.

Original Source: Malin News Release

Plankton Bloom in the Bay of Biscay

Envisat image of a plankton bloom of the coast of Spain. Image credit: ESA. Click to enlarge.
A break in the clouds in an Envisat observation of the west coast of Europe this week reveals a striking marine phytoplankton bloom currently dominating the Bay of Biscay.

Phytoplankton are microscopic marine plants that drift on or near the surface of the sea, by far the most abundant type of life found in the ocean. Just like plants on land they employ green-pigmented chlorophyll for photosynthesis – the process of turning sunlight into chemical energy.

While individually microscopic, phytoplankton chlorophyll collectively tints the surrounding ocean waters, providing a means of detecting these tiny organisms from space with dedicated ‘ocean colour’ sensors.

As if dye had been placed in the water, the greenish colour highlights whirls of ocean currents. Floating freely in the water, phytoplankton are sensitive not just to available sunlight but also to local environmental variations such as nutrient levels, temperature, currents and winds. Favourable conditions lead to concentrated ‘blooms’ like the one we see here.

Monitoring phytoplankton is important because they form the base of the marine food web ? sometimes known as ‘the grass of the sea’.

On a local level, out-of-control blooms can devastate marine life, de-oxygenating whole stretches of water, while some species of phytoplankton and marine algae are toxic to both fish and humans. It is useful that fishermen, fish farmers and public health officials know about such events as soon as possible.

Globally, phytoplankton are a major influence on the amount of carbon in the atmosphere, and hence need to be modelled into calculations of future climate change.

Phytoplankton blooms occur frequently at this time of year in the Bay of Biscay. This ‘spring bloom’ takes place as cold, nutrient-rich waters are finally exposed to sufficient sunlight to trigger rapid phytoplankton growth. The bloom is signaling a new cycle of biological production, important for the local fishing industry – the Bay of Biscay being a rich fishery.

Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument is optimised for ocean colour detection, but also returns detailed multispectral information on land cover, clouds and atmospheric aerosols.

MERIS acquires continuous daytime observations in Reduced Resolution mode as part of its background mission. This is a detail from a MERIS Reduced Resolution image was acquired on 2 May 2005. The full version, viewable by clicking the high-resolution image, has a spatial resolution of 1200 metres and covers an area of 838 by 2277 km.

Original Source: ESA News Release

Solar Minimum Doesn’t Mean a Calm Sun

A huge solar explosion in 2001. Image credit: SOHO. Click to enlarge.
There’s a myth about the sun. Teachers teach it. Astronomers repeat it. NASA mission planners are mindful of it.

Every 11 years solar activity surges. Sunspots pepper the sun; they explode; massive clouds of gas known as “CMEs” hurtle through the solar system. Earth gets hit with X-rays and protons and knots of magnetism. This is called solar maximum.

There’s nothing mythical about “Solar Max.” During the most recent episode in 2000 and 2001, sky watchers saw auroras as far south as Mexico and Florida; astronomers marveled at the huge sunspots; satellite operators and power companies struggled with outages.

Now the sun is approaching the opposite extreme of its activity cycle, solar minimum, due in 2006. We can relax because, around solar minimum, the sun is quiet. Right?

“That’s the myth,” says solar physicist David Hathaway of the NASA Marshall Space Flight Center. The truth is, solar activity never stops, “not even during solar minimum.”

To show that this is so, Hathaway counted the number of X-class solar flares each month during the last three solar cycles, a period spanning 1970 to the present. X-flares are the most powerful kind of solar explosions; they’re associated with bright auroras and intense radiation storms. “There was at least one X-flare during each of the last three solar minima,” says Hathaway.

This means astronauts traveling through the solar system, far from the protection of Earth’s atmosphere and magnetic field, can’t drop their guard–ever.

Recent events bear this out: Rewind to January 10, 2005. It’s four years since solar maximum and the sun is almost blank–only two tiny sunspots are visible from Earth. The sun is quiet.

The next day, with stunning rapidity, everything changes. On January 11th, a new ‘spot appears. At first no more than a speck, it quickly blossoms into a giant almost as big as the planet Jupiter. “It happened so quickly,” recalls Hathaway. “People were asking me if they should be alarmed.”

Between January 15th and 20th, the sunspot unleashed two X-class solar flares, sparked auroras as far south as Arizona in the United States, and peppered the Moon with high-energy protons. Lunar astronauts caught outdoors, had there been any, would’ve likely gotten sick.

So much for the quiet sun.

It almost happened again last month. On April 25, 2005, small sunspot emerged and–d?j? vu–it grew many times wider than Earth in only 48 hours. This time, however, there were no eruptions.

Why not? No one knows.

Sunspots are devilishly unpredictable. They’re made of magnetic fields poking up through the surface of the sun. Electrical currents deep inside our star drag these fields around, causing them to twist and tangle until they become unstable and explode. Solar flares and CMEs are by-products of the blast. The process is hard to forecast because the underlying currents are hidden from view. Sometimes sunspots explode, sometimes they don’t. Weather forecasting on Earth was about this good … 50 years ago.

Researchers like Hathaway study sunspots and their magnetic fields, hoping to improve the woeful situation. “We’re making progress,” he says.

Good thing. Predicting solar activity is more important than ever. Not only do we depend increasingly on sun-sensitive technologies like cell phones and GPS, but also NASA plans to send people back to the Moon and then on to Mars. Astronauts will be “out there” during solar maximum, solar minimum and all times in between.

Will the sun be quiet when it’s supposed to be? Don’t count on it.

Original Source: Science@NASA Article

More Sunlight is Hitting the Earth

Global map of brightness increases. Yellow represents an increase, brown is decreasing. Image credit: PNL. Click to enlarge.
Earth’s surface has been getting brighter for more than a decade, a reversal from a dimming trend that may accelerate warming at the surface and unmask the full effect of greenhouse warming, according to an exhaustive new study of the solar energy that reaches land.

Ever since a report in the late 1980s uncovered a 4 to 6 percent decline of sunlight reaching the planet’s surface over 30 years since 1960, atmospheric scientists have been trying out theories about why this would be and how it would relate to the greenhouse effect, the warming caused by the buildup of carbon dioxide and other gasses that trap heat in the atmosphere.

Meanwhile, a group led by Martin Wild at the Swiss Federal Institute of Technology in Zurich, home of the international Baseline Surface Radiation Network (BSRN) archive, had gone to work collecting surface measurements and crunching numbers.

“BSRN didn’t get started until the early ’90s and worked hard to update the earlier archive,” said Charles N. Long, senior scientist at the Department of Energy’s Pacific Northwest National Laboratory and co-author of a BSRN report in this week’s issue (Friday, May 6) of the journal Science.

“When we looked at the more recent data, lo and behold, the trend went the other way,” said Long, who conducted the work under the auspices of DOE’s Atmospheric Radiation Measurement (ARM) program.

Data analysis capabilities developed by ARM research were crucial in the study, which reveals the planet’s surface has brightened by about 4 percent the past decade. The brightening trend is corroborated by other data, including satellite analyses that are the subject of another paper in this week’s Science.

Sunlight that isn’t absorbed or reflected by clouds as it plunges earthward will heat the surface. Because the atmosphere includes greenhouse gasses, solar warming and greenhouse warming are related.

“The atmosphere is heated from the bottom up, and more solar energy at the surface means we might finally see the increases in temperature that we expected to see with global greenhouse warming,” Long said.

In fact, he said, many believe that we have already been seeing those effects in our most temperature-sensitive climates, with the melting of polar ice and high altitude glaciers.

The report’s authors stopped short of attributing a cause to the cycle of surface dimming and brightening, but listed such suspects as changes in the number and composition of aerosols?liquid and solid particles suspended in air?and how aerosols affect the character of clouds. Over the past decade, the ARM program has built a network of instrumentation sites to sample cloud characteristics and energy transfer in a variety of climates, from tropical to polar.

“The continuous, sophisticated data from these sites will be crucial for determining the causes,” Long said.

Long also pointed out that 70 percent of the planet’s surface is ocean, for which we have no long-term surface brightening or dimming measurements.

PNNL (www.pnl.gov) is a DOE Office of Science laboratory that solves complex problems in energy, national security, the environment and life sciences by advancing the understanding of physics, chemistry, biology and computation. PNNL employs more than 4,000 staff, has a $650 million annual budget, and has been managed by Ohio-based Battelle since the lab’s inception in 1965.

Original Source: PNL News Release

Artificial Gravity Will Help Astronauts Handle Spaceflight

The Short Radius Centrifuge will test human’s ability to withstand gravity. Image credit: NASA. Click to enlarge.
NASA will use a new human centrifuge to explore artificial gravity as a way to counter the physiologic effects of extended weightlessness for future space exploration.

The new research will begin this summer at the University of Texas Medical Branch (UTMB) at Galveston, overseen by NASA’s Johnson Space Center (JSC) in Houston. A NASA-provided Short-Radius Centrifuge will attempt to protect normal human test subjects from deconditioning when confined to strict bed rest.

Bed rest can closely imitate some of the detrimental effects of weightlessness on the body. For the first time, researchers will systematically study how artificial gravity may serve as a countermeasure to prolonged simulated weightlessness.

“The Vision for Space Exploration includes destinations beyond the moon,” said Dr. Jeffrey Davis, director of JSC’s Space Life Sciences Directorate. “This artificial gravity research is an important step in determining if spacecraft design options should include artificial gravity. The collaboration between NASA, the National Institutes of Health (NIH), UTMB and Wyle Laboratories demonstrates the synergy of government, academic and industry partnerships,” he added.

For the initial study this summer, 32 test subjects will be placed in a six-degree, head-down, bed-rest position for 21 days to simulate the effects of microgravity on the body. Half that group will spin once a day on the centrifuge to determine how much protection it provides from the bed-rest deconditioning. The “treatment” subjects will be positioned supine in the centrifuge and spun up to a force equal to 2.5 times Earth’s gravity at their feet for an hour and then go back to bed.

“The studies may help us to develop appropriate prescriptions for using a centrifuge to protect crews and to understand the side effects of artificial gravity on people,” said Dr. Bill Paloski, NASA principal scientist in JSC’s Human Adaptation and Countermeasures Office and principal investigator for the project. “In the past, we have only been able to examine bits and pieces. We’ve looked at how artificial gravity might be used as a countermeasure for, say, cardiovascular changes or balance disorders. This will allow us to look at the effect of artificial gravity as a countermeasure for the entire body,” he added.

The research will take place in UTMB’s NIH-sponsored General Clinical Research Center. The study supports NASA’s Artificial Gravity Biomedical Research Project.

“Physicians and scientists from all over the world will travel to UTMB to study the stresses that spaceflight imposes on cardiovascular function, bone density, neurological activity and other physiological systems,” said Dr. Adrian Perachio, executive director of strategic research collaborations at UTMB. “This is an excellent example of collaboration among the academic, federal and private sectors in research that will benefit the health of both astronauts and those of us on Earth,” he added.

The centrifuge was built to NASA specifications by Wyle Laboratories in El Segundo, Calif. It was delivered to UTMB in August 2004 and will complete design verification testing, validation of operational procedures and verification of science data this spring. The centrifuge has two arms with a radius of 10 feet (3 meters) each. The centrifuge can accommodate one subject on each arm.

Paloski has assembled a team of 24 investigators who designed the study. The first integrated research program is expected to end in the fall of 2006.

Original Source: NASA News Release

Eta Aquarid Meteor Shower Peaks on May 6

Look towards the Aquarius constellation in the early morning on May 6. Image credit: NASA. Click to enlarge.
The eta Aquarid meteor shower peaks on May 5th and 6th. The best time to look, no matter where you live, is during the hours before local sunrise on both days.

This is mainly a southern hemisphere shower, but northern observers can see it, too. In the United States, for example, observers far from city lights might see 5 to 10 meteors per hour. In Australia or South America, rates are better, between 15 and 60 meteors per hour.

This year (2005) the eta Aquarid meteors will be streaming from a point in the sky coincidentally close to Mars. The red planet, which is approaching Earth for a close encounter in October 2005, is already eye-catching.

Eta Aquarid meteors come from the most famous comet of all: Halley’s Comet. Our planet passes close to the orbit of Halley’s Comet twice a year. Although the comet itself is very far away [diagram] tiny pieces of Halley are still moving through the inner solar system. They’re leftovers from the comet’s many close encounters with the Sun. Each time Halley returns (every 76 years) solar heating evaporates about 6 meters of ice and rock from its nucleus! Debris particles called meteoroids, usually no bigger than grains of sand, gradually spread along the comet’s orbit forming an elongated stream of space dust. Earth passes through the debris stream once in May and again in October.

The eta Aquarids are named after a star in the constellation Aquarius. The star has nothing to do with the meteor shower except that the shower’s radiant happens to lie nearby. (The radiant of a meteor shower is a point in the sky from which the meteors appear to stream.) The eta Aquarid’s sister shower in October is called the Orionids, after the constellation Orion.

The eta Aquarid radiant never climbs very far above the horizon in the northern hemisphere. That’s why it is a better shower south of the equator. Most years northerners count about 10 eta Aquarid meteors per hour, while southerners see 3 to 6 times that many.

Northern sky watchers sometimes spot spectacular “Earth grazers,” while the active eta Aquarid radiant is low on the horizon. These are meteors that skim horizontally through the upper atmosphere. “Earth grazers” are typically slow and dramatic, streaking far across the sky. The best time to look for Earthgrazers is 2:00 to 2:30 a.m. local time.

Middle-latitude sky watchers in both hemispheres will see the eta Aquarid radiant rise over the eastern horizon at approximately 2:30 a.m. local time. Aquarius is a fairly dim constellation. The nearest bright star is 1st magnitude Fomalhaut in the constellation Piscis Austrini. Fomalhaut is a good finder star for sky watchers in the south, but it’s not much use to northerners because of its low altitude. In Sydney, Australia, for example, Fomalhaut will be visible at 4 a.m. at an elevation of +25 degrees, just above and westward of the shower’s radiant.

Experienced meteor watchers suggest the following viewing strategy: Dress warmly. Bring a reclining chair, or spread a thick blanket over a flat spot of ground. Lie down and look up somewhat toward the east. Meteors can appear in any part of the sky, although their trails will tend to point back toward the radiant.

Original Source: NASA Spaceweather

High Resolution Global Map in Development

Envisat will build up the most detailed map of the entire Earth. Image credit: ESA. Click to enlarge.
The most detailed portrait ever of the Earth’s land surface is being created with ESA’s Envisat environmental satellite. The GLOBCOVER project aims at producing a global land cover map to a resolution three times sharper than any previous satellite map.

It will be a unique depiction of the face of our planet in 2005, broken down into more than 20 separate land cover classes. The completed GLOBCOVER map will have numerous uses, including plotting worldwide land use trends, studying natural and managed ecosystems and modelling climate change extent and impacts.

Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument is being systematically used in Full Resolution Mode for the project, acquiring images with a spatial resolution of 300 metres, with an average 150 minutes of acquisitions occurring daily.

The estimate is that up to 20 terabytes of imagery will be needed to mosaic together the final worldwide GLOBCOVER map ? an amount of data equivalent to the contents of 20 million books. The image acquisition strategy is based around regional climate patterns to minimise cloud or snow cover. Multiple acquisitions are planned for some regions to account for seasonal variations in land cover.

Other Envisat sensors will work in synergy with MERIS. The Advanced Synthetic Aperture Radar (ASAR) instrument will be used to differentiate between similar land cover classes, such as wetlands and humid tropical rainforests. And information from the satellite’s Advanced Along Track Scanning Radiometer will be used to correct for atmospheric distortion and to perform ‘cloud masking’, or the elimination of cloud pixels.

An international network of partners is working with ESA on the two-year GLOBCOVER project, which is taking place as part of the Earth Observation Data User Element (DUE).

Participants include the United Nations Environment Programme (UNEP), the Food and Agriculture Organisation (FAO), the European Commission’s Joint Research Centre (JRC), the International Geosphere-Biosphere Programme (IGBP) and the Global Observations of Forest Cover and Global Observations of Land Dynamics (GOFC-GOLD) Implementation Team Project Office.

“UNEP anticipates being able to put the GLOBCOVER map to good use within its programme of assessment and early warning of emerging environmental issues and threats, particularly those of a trans-boundary nature,” said Ron Witt of UNEP. “Changes in land cover patterns, effects of environmental pollution and loss of biodiversity often do not respect national or other artificial boundaries. “An updated view of such problems – or their effects – from interpreted space imagery should offer a large boost to UNEP’s effort to monitor the health of the planet and our changing environment.”

Located at Friedrich-Schiller University in Jena, Germany, the GOFC-GOLD Implementation Team Project Office is responsible for developing international standards and methodology for global observations, and is advising GLOBCOVER on classification issues.

The GLOBCOVER classification system is being designed to be compatible with the Global Land Cover map previously produced for the JRC for the year 2000, a one-kilometre resolution map produced from SPOT-4 Vegetation Instrument data and known as GLC 2000.

GLOBCOVER will also serve to update and improve the European Environment Agency’s CORINE 2000 database, a 300-metre resolution land cover map of the European continent based on a combination of updated land cover maps and satellite imagery.

Once worldwide MERIS Full Resolution coverage is achieved, there will actually be two GLOBCOVER maps produced. The first, GLOBCOVER V1, will be produced automatically by mosaicking images together in a standardised way.

The JRC is then utilising its GLC2000 experience to produce the more advanced GLOBCOVER V2 in the second year, taking a regionally-tuned approach to the data. Some 30 teams worldwide will participate in analysing and validating GLOBCOVER products.

Acquired in a standardised 15 bands, the MERIS images are going to be processed with an upgraded algorithm that includes an ortho-rectification fool, correcting for altitude based on a digital elevation model (DEM) derived from the Radar Altimeter-2 (RA-2), another Envisat instrument.

Original Source: ESA News Release