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ESA & ROSCOSMOS - ExoMars Mission patch.

21 February 2018

Slowed by skimming through the very top of the upper atmosphere, ESA’s ExoMars has lowered itself into a planet-hugging orbit and is about ready to begin sniffing the Red Planet for methane.

Aerobraking completed

The ExoMars Trace Gas Orbiter arrived at Mars in October 2016 to investigate the potentially biological or geological origin of trace gases in the atmosphere.

It will also serve as a relay, connecting rovers on the surface with their controllers on Earth.

But before any of this could get underway, the spacecraft had to transform its initial, highly elliptical four-day orbit of about 98 000 x 200 km into the final, much lower and circular path at about 400 km.

Terrifically delicate

“Since March 2017, we’ve been conducting a terrifically delicate ‘aerobraking’ campaign, during which we commanded it to dip into the wispy, upper-most tendrils of the atmosphere once per revolution, slowing the craft and lowering its orbit,” says ESA flight director Michel Denis.

Good progress

“This took advantage of the faint drag on the solar wings, steadily transforming the orbit. It’s been a major challenge for the mission teams supported by European industry, but they’ve done an excellent job and we’ve reached our initial goal.

“During some orbits, we were just 103 km above Mars, which is incredibly close.”

The end of this effort came at 17:20 GMT on 20 February, when the craft fired its thrusters for about 16 minutes to raise the closest approach to the surface to about 200 km, well out of the atmosphere. This effectively ended the aerobraking campaign, leaving it in an orbit of about 1050 x 200 km.

Employing interplanetary experience

“We already acquired experience with aerobraking on a test basis at the end of the Venus Express mission, which was not designed for aerobraking, in 2014,” says spacecraft operations manager Peter Schmitz.

“But this is the first time ESA has used the technique to achieve a routine orbit around another planet – and ExoMars was specifically designed for this.”

ExoMars - Trace Gas Orbiter (TGO)

Aerobraking around an alien planet that is, typically, 225 million km away is an incredibly delicate undertaking. The thin upper atmosphere provides only gentle deceleration – at most some 17 mm/s each second. How small is this?

If you braked your car at this rate from an initial speed of 50 km/h to stop at a junction, you’d have to start 6 km in advance.

Venus Express aerobraking 2014

“Aerobraking works only because we spent significant time in the atmosphere during each orbit, and then repeated this over 950 times,” says Michel.

“Over a year, we’ve reduced the speed of the spacecraft by an enormous 3600 km/h, lowering its orbit by the necessary amount.”

Trimming

In the next month, the control team will command the craft through a series of up to 10 orbit-trimming manoeuvres, one every few days, firing its thrusters to adjust the orbit to its final two-hour, circular shape at about 400 km altitude, expected to be achieved around mid-April.

The initial phases of science gathering, in mid-March, will be devoted to checking out the instruments and conducting preliminary observations for calibration and validation. The start of routine science observations should happen around 21 April.

“Then, the craft will be reoriented to keep its camera pointing downwards and its spectrometers towards the Sun, so as to observe the Mars atmosphere, and we can finally begin the long-awaited science phase of the mission,” says Håkan Svedhem, ESA’s project scientist.

Taking stereo images

The main goal is to take a detailed inventory of trace gases, in particular seeking out evidence of methane and other gases that could be signatures of active biological or geological activity.

A suite of four science instruments will make complementary measurements of the atmosphere, surface and subsurface. Its camera will help to characterise features on the surface that may be related to trace-gases sources, such as volcanoes.

It will also look for water-ice hidden just below the surface, which along with potential trace gas sources could guide the choice for future mission landing sites.

Long-distance calls

April will also see the craft test its data-relay capability, a crucial aspect of its mission at Mars.

A NASA-supplied radio relay payload will catch data signals from US rovers on the surface and relay these to ground stations on Earth. Data relaying will get underway on a routine basis later in the summer.

Relaying calls from rovers

Starting in 2021, once ESA’s own ExoMars rover arrives, the orbiter will provide data-relay services for both agencies and for a Russian surface science platform.

ExoMars is a joint endeavour between ESA and Roscosmos.

ESA's ExoMars: http://www.esa.int/Our_Activities/Space_Science/ExoMars

ExoMars in depth:

ExoMars in depth: http://exploration.esa.int/mars/

Mission operations in depth: http://www.esa.int/Our_Activities/Operations/ExoMars_TGO_operations

Related links:

Mars Express: http://www.esa.int/Our_Activities/Space_Science/Mars_Express

Roscosmos: http://en.federalspace.ru/

ExoMars at IKI: http://exomars.cosmos.ru/

Thales Alenia Space: https://www.thalesgroup.com/en/worldwide/space/space

NASA In 2016 ExoMars orbiter (Electra radio): http://mars.nasa.gov/programmissions/missions/future/exomarsorbiter2016/

Where on Mars?: http://whereonmars.co/

ExoMars for broadcasters: http://www.esa.int/esatv/Transmissions/2016/10/ExoMars_at_Mars_live_coverage

Images, Videos, Text, Credits: ESA/C. Carreau/J. Bauer/University of Bern/ATG medialab.

Best regards, Orbiter.ch

Nearly a Decade After Mars Phoenix Landed, Another Look

NASA - Mars Reconnaissance Orbiter (MRO) logo.

February 21, 2018

Animation above: This animation blinks between two images of NASA's Mars Phoenix Lander hardware around the mission's 2008 landing site on far-northern Mars. By late 2017, dust obscures much of what was visible two months after the landing. The lander is near the top; the back shell and parachute near the bottom. Animation credits: NASA/JPL-Caltech/Univ. of Arizona.

A recent view from Mars orbit of the site where NASA's Phoenix Mars mission landed on far-northern Mars nearly a decade ago shows that dust has covered some marks of the landing.

The Phoenix lander itself, plus its back shell and parachute, are still visible in the image taken Dec. 21, 2017, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. But an animated-blink comparison with an image from about two months after the May 25, 2008, landing shows that patches of ground that had been darkened by removal of dust during landing events have become coated with dust again.

Phoenix Mars Lander. Image Credit: NASA

In August 2008, Phoenix completed its three-month mission studying Martian ice, soil and atmosphere. The lander worked for two additional months before reduced sunlight caused energy to become insufficient to keep the lander functioning. The solar-powered robot was not designed to survive through the dark and cold conditions of a Martian arctic winter.

For additional information about the Phoenix mission, visit:

https://www.nasa.gov/mission_pages/phoenix/main/index.html

For additional information about the Mars Reconnaissance Orbiter mission, visit:

https://mars.nasa.gov/mro/

Image (mentioned), Animation (mentioned), Text, Credits: NASA/JPL/Andrew Good/Guy Webster.

Greetings, Orbiter.ch

New Study Brings Antarctic Ice Loss Into Sharper Focus

NASA logo.

Feb. 20, 2018

Image above: The flow of Antarctic ice, derived from feature tracking of Landsat imagery. Image Credits: NASA Earth Observatory.

A NASA study based on an innovative technique for crunching torrents of satellite data provides the clearest picture yet of changes in Antarctic ice flow into the ocean. The findings confirm accelerating ice losses from the West Antarctic Ice Sheet and reveal surprisingly steady rates of flow from its much larger neighbor to the east.

The computer-vision technique crunched data from hundreds of thousands of NASA-U.S. Geological Survey Landsat satellite images to produce a high-precision picture of changes in ice-sheet motion.

The new work provides a baseline for future measurement of Antarctic ice changes and can be used to validate numerical ice sheet models that are necessary to make projections of sea level. It also opens the door to faster processing of massive amounts of data.

“We’re entering a new age,” said the study’s lead author, cryospheric researcher Alex Gardner of NASA’s Jet Propulsion Laboratory in Pasadena, California. “When I began working on this project three years ago, there was a single map of ice sheet flow that was made using data collected over 10 years, and it was revolutionary when it was published back in 2011. Now we can map ice flow over nearly the entire continent, every year. With these new data, we can begin to unravel the mechanisms by which the ice flow is speeding up or slowing down in response to changing environmental conditions.”

The innovative approach by Gardner and his international team of scientists largely confirms earlier findings, though with a few unexpected twists.

Among the most significant: a previously unmeasured acceleration of glacier flow into Antarctica’s Getz Ice Shelf, on the southwestern part of the continent -- likely a result of ice-shelf thinning.

Speeding up in the west, steady flow in the east

The research, published in the journal “The Cryosphere,” also identified the fastest speed-up of Antarctic glaciers during the seven-year study period. The glaciers feeding Marguerite Bay, on the western Antarctic Peninsula, increased their rate of flow by 1,300 to 2,600 feet (400 to 800 meters) per year, probably in response to ocean warming.

Perhaps the research team’s biggest discovery, however, was the steady flow of the East Antarctic Ice Sheet. During the study period, from 2008 to 2015, the sheet had essentially no change in its rate of ice discharge -- ice flow into the ocean. While previous research inferred a high level of stability for the ice sheet based on measurements of volume and gravitational change, the lack of any significant change in ice discharge had never been measured directly.

The study also confirmed that the flow of West Antarctica’s Thwaites and Pine Island glaciers into the ocean continues to accelerate, though the rate of acceleration is slowing.

In all, the study found an overall ice discharge for the Antarctic continent of 1,929 gigatons per year in 2015, with an uncertainty of plus or minus 40 gigatons. That represents an increase of 36 gigatons per year, plus or minus 15, since 2008. A gigaton is one billion tons.

The study found that ice flow from West Antarctica -- the Amundsen Sea sector, the Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula -- accounted for 89 percent of the increase.

Computer vision

The science team developed software that processed hundreds of thousands of pairs of images of Antarctic glacier movement from Landsats 7 and 8, captured from 2013 to 2015.

These were compared to earlier radar satellite measurements of ice flow to reveal changes since 2008.

“We’re applying computer vision techniques that allow us to rapidly search for matching features between two images, revealing complex patterns of surface motion,” Gardner said.

Instead of researchers comparing small sets of very high-quality images from a limited region to look for subtle changes, the novelty of the new software is that it can track features across hundreds of thousands of images per year -- even those of varying quality or obscured by clouds -- over an entire continent.

“We can now automatically generate maps of ice flow annually -- a whole year -- to see what the whole continent is doing,” Gardner said.

The new Antarctic baseline should help ice sheet modelers better estimate the continent’s contribution to future sea level rise.

“We’ll be able to use this information to target field campaigns, and understand the processes causing these changes,” Gardner said. “Over the next decade, all this is going to lead to rapid improvement in our knowledge of how ice sheets respond to changes in ocean and atmospheric conditions, knowledge that will ultimately help to inform projections of sea level change.”

Related links:

Earth Research Findings: https://www.nasa.gov/subject/7782/earth-research-findings

Climate: https://www.nasa.gov/subject/3127/climate

Ice: https://www.nasa.gov/subject/3132/ice

Image (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Alan Buis/Written by Pat Brennan.

Greetings, Orbiter.ch

Cosmic explosion 10.5 billion years ago

University of Southampton logo.

Feb. 20, 2018

Researchers from Southampton University have spotted the most distant supernova ever discovered. The phenomenon occurred when a massive star ended in a cataclysmic explosion known as the supernova.

A huge 10.5 billion-year-old cosmic explosion: astronomers announce on Tuesday that they have discovered the supernova, an end-of-life star, the most distant ever detected.

Supernova DES16C2nm. Image credits: Mr Smith / DES Collaboration

"DES16C2nm (the name given to this supernova, ed) is extremely distant, extremely brilliant and extremely rare, not the kind of thing that, as an astronomer, one falls on every day," says Mathew Smith, lead author of the study, in a statement from the University of Southampton (UK).

The phenomenon occurred when a massive star coiled in a galaxy far away ended its days in a cataclysmic explosion known as the supernova.

The phenomena that accompany the death of a star are very violent because the material component of the star is ejected at speeds of several thousand kilometers per second. Due to the incredible amount of energy released, the event shines as much as ... 200 million suns and can be seen from Earth.

Astronomers reveal secrets of most distant supernova ever detected. Image Credit: NASA

The light emitted by the celestial phenomenon reached our planet 10.5 billion years after it took place and was detected for the first time in August 2016. Its distance and extreme brightness were then confirmed in October 2017 by three separate telescopes.

The international team of astronomers led by the University of Southampton and the origin of the study published Tuesday in the Astrophysical Journal ranked the youngest among the "super bright supernovas (SLSN)", the class of supernovas the brightest and the rarest. "In addition to being a very exciting discovery, the extreme distance of DES16C2nm gives us a unique insight into the nature of super bright supernovas," says Mathew Smith.

"The ultraviolet light emitted by this supernova tells us about the amount of metal produced in the explosion and the temperature of the explosion itself, two essential information to understand the causes, the engines, of these cosmic explosions", adds -t it.

Southampton University: https://www.southampton.ac.uk/

Super bright supernovas (SLSN): http://www.rochesterastronomy.org/snimages/

Images (mentioned), Text, Credits: AFP/Orbiter.ch Aerospace/Roland Berga.

Best regards, Orbiter.ch

James Webb Space Telescope to Reveal Secrets of the Red Planet

NASA - James Webb Space Telescope (JWST) patch.

Feb. 20, 2018

The planet Mars has fascinated scientists for over a century. Today, it is a frigid desert world with a carbon dioxide atmosphere 100 times thinner than Earth’s. But evidence suggests that in the early history of our solar system, Mars had an ocean’s worth of water. NASA’s James Webb Space Telescope will study Mars to learn more about the planet’s transition from wet to dry, and what that means about its past and present habitability.

NASA - Measuring Mars'Ancient Ocean

Video above: Hydrogen atoms escape from the Mars upper atmosphere, while water containing heavy hydrogen (deuterium) remains trapped on the planet. The escape of hydrogen helped to turn Mars from a wet planet 4.5 billion years ago into a dry world today. Video Credit: NASA.

Mars will be targeted as part of a Guaranteed Time Observation (GTO) project led by Heidi Hammel, a planetary astronomer and executive vice president of the Association of Universities for Research in Astronomy (AURA) in Washington, D.C. The GTO program provides dedicated time to the scientists who have worked with NASA to craft the science capabilities of Webb throughout its development. Hammel was selected by NASA as a JWST Interdisciplinary Scientist in 2003. Mars will be visible to Webb from May to September 2020 during its first year of operations, known as Cycle 1.

“Webb will return extremely interesting measurements of chemistry in the Martian atmosphere,” noted Hammel. “And most importantly, these Mars data will be immediately available to the planetary community to enable them to plan even more detailed Mars observations with Webb in future cycles.”

“We are all looking forward to Webb’s observations of Mars. I just know they will be fantastic, with the potential for immediate scientific discoveries,” said Jim Green, director of NASA’s Planetary Science Division, NASA Headquarters, Washington, D.C.

Webb’s advantages and challenges

Mars has been visited by more missions than any other planet in our solar system. It is currently orbited by six active spacecraft, while two rovers trundle across its surface. Webb offers several capabilities that complement these up-close missions.

One key asset is Webb’s ability to take a snapshot of the entire disk of Mars at once. Orbiters, in contrast, take time to make a full map and therefore can be affected by day-to-day variability, while rovers can only measure one location. Webb also benefits from excellent spectral resolution (the ability to measure small differences in wavelengths of light) and a lack of interfering atmosphere that plagues ground-based measurements from Earth.

Mars (Credits mentioned on the image)

That said, observing Mars with Webb will not be easy. “Webb is designed to be able to detect extremely faint and distant targets, but Mars is bright and close,” explained Geronimo Villanueva of NASA’s Goddard Space Flight Center, Mars lead on the GTO project. As a result, the observations will be carefully designed to avoid swamping Webb’s delicate instruments with light.

“Very importantly, observations of Mars will also test Webb’s capabilities in tracking moving objects across the sky, which is of key importance when investigating our solar system,” said Stefanie Milam at NASA’s Goddard Space Flight Center, Greenbelt, Md. who is coordinating the solar system program with Webb.

Water and methane

Much of the water Mars once held was lost over time due to ultraviolet light from the Sun breaking apart water molecules. Researchers can estimate how much water vanished by measuring the abundance of two slightly different forms of water in Mars’ atmosphere – normal water (H2O) and heavy water (HDO), in which one hydrogen atom is replaced by naturally occurring deuterium. The preferential escape of lighter hydrogen over time would then lead to a skewed ratio of H2O to HDO on Mars, indicative of how much water has escaped into space. Webb will be able to measure this ratio at different times, seasons and locations.

Detection of Methane and Water Vapor in Mars Atmosphere

Video above: Researchers using ground-based observatories have detected increased concentrations of both methane and water vapor in the Martian atmosphere during the northern hemisphere summer. Video Credit: NASA.

“With Webb, we can obtain a real and accurate measurement of the ratio of H2O to HDO across Mars, permitting us to determine how much water was truly lost. We also can determine how water is exchanged between polar ice, the atmosphere, and the soil,” said Villanueva.

Although most of the water on Mars is locked up in ice, the possibility remains that some liquid water could exist in underground aquifers. These potential reservoirs could even host life. This intriguing idea received a boost in 2003, when astronomers detected methane in the Martian atmosphere. Methane could be generated by bacteria, although it could also come from geological processes. Data from Webb could provide new clues to the origin of these methane plumes.

The James Webb Space Telescope is the world’s premier infrared space observatory of the next decade. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, the European Space Agency (ESA) and the Canadian Space Agency (CSA).

For more information about Webb, visit http://www.nasa.gov/webb or http://www.webbtelescope.org/.

Image (mentioned), Videos (mentioned), Text, Credits: NASA/Lynn Jenner/Space Telescope Science Institute, by Christine Pulliam.

Best regards, Orbiter.ch

Pulsating Aurora Mysteries Uncovered with Help from NASA’s THEMIS Mission

NASA - THEMIS Mission patch.

Feb. 20, 2018

Sometimes on a dark night near the poles, the sky pulses a diffuse glow of green, purple and red. Unlike the long, shimmering veils of typical auroral displays, these pulsating auroras are much dimmer and less common. While scientists have long known auroras to be associated with solar activity, the precise mechanism of pulsating auroras was unknown. Now, new research, using data from NASA’s Time History of Events and Macroscale Interactions during Substorms — or THEMIS — mission and Japan’s Exploration of energization and Radiation in Geospace — shortened to ERG, or also known as Arase — satellite, has finally captured the missing link thought responsible for these auroras. The answer lies in chirping waves that rhythmically pulse the particles that create the auroras.

Image above: Illustration of three THEMIS satellites and Earth's magnetosphere. Image Credit: NASA.

Earth’s magnetic bubble — the magnetosphere — protects the planet from high-energy radiation coming from the Sun and interstellar space, but during particularly strong solar events, particles can slip through. Once inside, the particles and the energy they carry are stored on the nightside of the magnetosphere, until an event, known as a substorm, releases the energy. The electrons are then sent speeding down into Earth’s upper atmosphere where they collide with the other particles and produce the characteristic glow.

Pulsating auroras, however, have a slightly different cause. The magnetosphere is home to a type of plasma wave known as whistler mode chorus. These waves have characteristic rising tones — reminiscent of the sounds of chirping birds — and are able to efficiently disturb the electrons. When these waves make their appearance within the magnetosphere, some of the electrons scattered by the wave careen down into Earth’s atmosphere, causing the pulsating auroras.

Illustration of the ERG satellite in orbit. Image Credits: ISAS/JAXA

While scientists have long believed this mechanism to be responsible for pulsating auroras, they had no definitive proof until now. The multipoint observations from the ERG satellite and ground-based all-sky cameras from the THEMIS mission allowed scientists to pinpoint the cause and effect, seeing the event from start to end. The results were published in the journal Nature.

Research done with NASA’s ground-based camera and Japan’s spacecraft in the near-Earth laboratory has applications further afield. Chorus waves have been observed around other planets in the solar system, including Jupiter and Saturn. Likely, the processes observed around Earth can help explain auroral features on these gas giants as well as on planets around other stars. The results also help scientists better understand how plasma waves can influence electrons — something that occurs in processes across the universe.

Related Links:

Journal Nature: https://www.nature.com/articles/nature25505

Learn more about the THEMIS Mission: https://www.nasa.gov/mission_pages/themis/main/index.html

Learn more about NASA’s research on the Sun-Earth environment: https://www.nasa.gov/mission_pages/sunearth/index.html

Images (mentioned), Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Mara Johnson-Groh.

Greetings, Orbiter.ch

Final Frontier

NASA - Cassini Mission to Saturn patch.

Feb. 20, 2018

This view of Saturn looks toward the planet's night side, lit by sunlight reflected from the rings. A mosaic of some of the very last images captured by Cassini’s cameras, it shows the location where the spacecraft would enter the planet's atmosphere hours later. The oval marks the entry site. While this area was on the night side of the planet at the time, it would rotate into daylight by the time Cassini made its final dive into Saturn's upper atmosphere, ending its remarkable 13-year exploration of Saturn.

Images taken using red, green and blue spectral filters were combined to show the scene in near natural color. The images were taken with Cassini’s wide-angle camera on Sept. 14, 2017, at a distance of approximately 394,000 miles (634,000 kilometers) from Saturn.

The Cassini spacecraft ended its mission on Sept. 15, 2017.

Cassini Grand Finale. Animation Credits: NASA/JPL-Caltech

The Cassini mission is a cooperative project of NASA, ESA (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 mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and https://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org and ESA's website: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Image, Text, Credits: NASA/Tony Greicius/JPL-Caltech/Space Science Institute.

Greetings, Orbiter.ch