Spitzer Spies an Odd, Tiny Asteroid

NASA - Spitzer Space Telescope logo.

June 20, 2014

Astronomers using NASA's Spitzer Space Telescope have measured the size of an asteroid candidate for NASA's Asteroid Redirect Mission (ARM), a proposed spacecraft concept to capture either a small asteroid, or a boulder from an asteroid. The near-Earth asteroid, called 2011 MD, was found to be roughly 20 feet (6 meters) in size, and its structure appears to contain a lot of empty space, perhaps resembling a pile of rubble. Spitzer's infrared vision was key to sizing up the asteroid.

I Spy a Little Asteroid With My Infrared Eye

Image above: This image of asteroid 2011 MD was taken by NASA's Spitzer Space Telescope in Feb. 2014, over a period of 20 hours. The long observation, taken in infrared light, was needed to pick up the faint signature of the small asteroid (center of frame). Image credit: NASA/JPL-Caltech/Northern Arizona University/SAO.

"From its perch up in space, Spitzer can use its heat-sensitive infrared vision to spy asteroids and get better estimates of their sizes," said Michael Mommert of Northern Arizona University, Flagstaff, lead author of a new study appearing today, June 19, in the Astrophysical Journal Letters. David Trilling, also of Northern Arizona University, leads the team of astronomers.

Image above: How to Measure the Size of an Asteroid Observations of infrared light coming from asteroids provide a better estimate of their true sizes than visible-light measurements. Image credit: NASA/JPL-Caltech.

The Spitzer results confirm that asteroid 2011 MD has characteristics suitable for the ARM proposal, elevating it to the "valid candidate" level. Valid candidates are those asteroids with the right size, mass and rotation rate to be feasibly captured by the robotic spacecraft. Two other valid candidates have been identified so far. (The proposal to capture a boulder from an asteroid involves a different set of criteria.) NASA continues to search for and find new potential candidates using its ground-based asteroid survey programs.

Prior to the Spitzer study, the size of 2011 MD was only very roughly known. It had been observed in visible light, but an asteroid's size cannot be determined solely from visible-light measurements. In visible light alone, for example, a white snowball in space could look just as bright as a dark mountain of cosmic rock. The objects may differ in size but reflect the same amount of sunlight, appearing equally bright.

Image above: The Spitzer Space Telescope whizzes in front of a brilliant, infrared view of the Milky Way galaxy's plane in this artistic depiction. Image credit: NASA/JPL-Caltech.

Infrared light, on the other hand, is a better indicator of an object's true size. This is because an object's infrared glow depends largely on its temperature, not its reflectivity.

From the new Spitzer data, the team was able to measure the size of asteroid 2011 MD. When the infrared and visible-light observations were combined, the asteroid's density and mass could also be measured. The density of 2011 MD is remarkably low -- about the same as water, which agrees with a separate analysis of observations taken in 2011. Since rock is about three times more dense than water, this implies that about two-thirds of the asteroid must be empty space.

What does an asteroid with that much empty space look like? The team doesn't know, but proposes two possible solutions: it might be a collection of loosely bound rocks, like a fleet of flying boulders, or a solid rock with surrounding fine debris.

A similar "rubble-pile" type of composition was also found for asteroid 2009 BD, another valid candidate for ARM. Trilling and colleagues used Spitzer to help pin down the size of that asteroid to roughly 10 to 13 feet (3 or 4 meters).

Image above: Solid as a Rock? Porosity of Asteroids. Asteroids can differ in the degree of porosity, or the amount of empty space that makes up their structures. Image credit: NASA/JPL-Caltech.

In both studies, Spitzer stared at the asteroids for about 20 hours. Such long observations are scheduled more often in Spitzer's "warm" mission, a phase that began in 2009 when the spacecraft ran out of coolant, as planned. Spitzer, which still has two infrared channels that operate without coolant, now specializes in longer, targeted observing campaigns.

"With Spitzer, we have been able to get some of the first measurements of the sizes and compositions of tiny asteroids," said Trilling. "So far, we've looked at two asteroids and found both of them to be really weird -- not at all like the one solid rock that we expected. We're scratching our heads."

The team says the small asteroids probably formed as a result of collisions between larger asteroids, but they do not understand how their unusual structures could have come about. They plan to use Spitzer in the future to study more of the tiny asteroids, both as possible targets for asteroid space missions, and for a better understanding of the many asteroid denizens making up our solar system.

Other authors of the Spitzer paper are: D. Farnocchia, P. Chodas and S. R. Chesley of NASA's Jet Propulsion Laboratory, Pasadena, California; J. L. Hora, G. G. Fazio and H.A. Smith of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts; M. Mueller of the SRON Netherlands Institute for Space Research, Netherlands; and A. W. Harris of the DLR Institute for Planetary Research, Germany.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

Through its Asteroid Initiative, NASA is developing a first-ever mission to identify, capture and redirect a near-Earth asteroid to a stable orbit around the moon with a robotic spacecraft. Astronauts aboard an Orion spacecraft, launched by a Space Launch System rocket, will explore the asteroid in the 2020s, returning to Earth with samples. Experience in human spaceflight beyond low-Earth orbit through this Asteroid Redirect Mission will help NASA test new systems and capabilities needed to support future human missions to Mars. The Initiative also includes an Asteroid Grand Challenge, which is seeking the best ideas to find all asteroid threats to human populations and accelerate the work NASA already is doing for planetary defense.

JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.

More information about asteroids and near-Earth objects is available at:

http://neo.jpl.nasa.gov

http://www.jpl.nasa.gov/asteroidwatch/

More information about Spitzer is at:

http://spitzer.caltech.edu

http://www.nasa.gov/spitzer

Images (mentioned), Text, Credits: NASA / JLP / Whitney Clavin.

Cheers, Orbiter.ch

NASA's Swift Satellite Tallies Water Production of Mars-bound Comet

NASA - SWIFT Mission patch.

June 19, 2014

In late May, NASA's Swift satellite imaged comet Siding Spring, which will brush astonishingly close to Mars later this year. These optical and ultraviolet observations are the first to reveal how rapidly the comet is producing water and allow astronomers to better estimate its size.

"Comet Siding Spring is making its first passage through the inner solar system and is experiencing its first strong heating from the sun," said lead researcher Dennis Bodewits, an astronomer at the University of Maryland College Park (UMCP). "These observations are part of a two-year-long Swift campaign to watch how the comet's activity develops during its travels."

"Fresh" comets like Siding Spring, which is formally known as C/2013 A1, contain some of the most ancient material scientists can study. The solid part of a comet, called its nucleus, is a clump of frozen gases mixed with dust and is often described as a "dirty snowball." Comets cast off gas and dust whenever they venture near enough to the sun.

Image above: This composite of C/2013 A1 (Siding Spring) merges Swift UVOT images taken between May 27 and 29, 2014. Sunlight reflected from the comet's dust, which produces most of the light in this image, appears yellow; violet shows ultraviolet light produced by hydroxyl (OH), a molecular fragment of water. Image Credit: NASA/Swift/D. Bodewits (UMD), DSS.

What powers this activity is the transformation of frozen material from solid ice to gas, a process called sublimation. As the comet approaches the sun and becomes heated, different gases stream from the nucleus, carrying with them large quantities of dust that reflect sunlight and brighten the comet. By about two and a half times Earth's distance from the sun (2.5 astronomical units, or AU), the comet has warmed enough that water becomes the primary gas emitted by the nucleus.

Between May 27 and 29, Swift's Ultraviolet/Optical Telescope (UVOT) captured a sequence of images as comet Siding Spring cruised through the constellation Eridanus at a distance of about 2.46 AU (229 million miles or 368 million km) from the sun. While the UVOT cannot detect water molecules directly, it can detect light emitted by fragments formed when ultraviolet sunlight breaks up water -- specifically, hydrogen atoms and hydroxyl (OH) molecules.

"Based on our observations, we calculate that at the time of the observations the comet was producing about 2 billion billion billion water molecules, equivalent to about 13 gallons or 49 liters, each second," said team member Tony Farnham, a senior research scientist at UMCP. At this rate, comet Siding Spring could fill an Olympic-size swimming pool in about 14 hours. Impressive as it sounds, though, this is relatively modest water emission compared to other comets Swift has observed.

NASA's Swift spacecraft. Image Credit: NASA's Goddard Space Flight Center

Based on these measurements, the team concludes that the icy nucleus of comet Siding Spring is only about 2,300 feet (700 meters) across, placing it at the lower end of a size range estimated from earlier observations by other spacecraft.

The comet makes its closest approach to Mars on Oct. 19, passing just 86,000 miles (138,000 km) from the Red Planet -- so close that gas and dust in the outermost reaches of the comet's atmosphere, or coma, will interact with the atmosphere of Mars.

For comparison, the closest recorded Earth approach by a comet was by the now-defunct comet Lexell, which on July 1, 1770, swept to within 1.4 million miles (2.3 million km) or about six times farther than the moon. During its Mars flyby, comet Siding Spring will pass more than 16 times closer than this. 

Scientists have established that the comet poses no danger to spacecraft now in orbit around Mars. These missions will be pressed into service as a provisional comet observation fleet to take advantage of this unprecedented opportunity.

The Swift observations are part of a larger study to investigate the activity and evolution of new comets, which show distinct brightening characteristics as they approach the sun not seen in other comets. Bodewits and his colleagues single out comets that can be observed by Swift at distances where water has not yet become the primary gas and repeatedly observe them as they course through the inner solar system. This systematic study will help astronomers better understand how comet activity changes with repeated solar heating.

Related links:

Comet to Make Close Flyby of Red Planet in October 2014:
http://orbiterchspacenews.blogspot.ch/2013/03/comet-to-make-close-flyby-of-red-planet.html

NASA's Hubble Space Telescope Spots Mars-Bound Comet Sprout Multiple Jets:
http://orbiterchspacenews.blogspot.ch/2014/03/hubble-space-telescope-spots-mars-bound.html

NASA's Swift Monitors Departing Comet Garradd (4.13.2012):
http://www.nasa.gov/mission_pages/swift/bursts/comet-garradd.html

Swift’s Comet Tally Highlighted in Observatory Webcast (04.03.2009)
http://www.nasa.gov/mission_pages/swift/bursts/observatory_webcast.html

NASA's Swift Spies Comet Lulin (02.20.2009):
http://www.nasa.gov/mission_pages/swift/bursts/lulin.html

NASA's Swift Looks to Comets for a Cool View (12.03.2008):
http://www.nasa.gov/mission_pages/swift/bursts/cool_comet.html

Images (mentioned), Text, Credits: NASA's Goddard Space Flight Center / Francis Reddy.

Greetings, Orbiter.ch

Rosetta’s comet: expect the unexpected

ESA - Rosetta Mission patch.

19 June 2014

An image snapped earlier this month by ESA’s Rosetta spacecraft shows its target comet has quietened, demonstrating the unpredictable nature of these enigmatic objects.

Comet on 4 June

The picture was captured on 4 June by Rosetta’s scientific camera, and is the most recent full-resolution image from the narrow-angle sensor. It has been used to help fine-tune Rosetta’s navigation towards comet 67P/Churyumov–Gerasimenko, which was 430 000 km away at the time.

Strikingly, there is no longer any sign of the extended dust cloud that was seen developing around nucleus at the end of April and into May, as shown in our last image release. Indeed, monitoring of the comet has shown a significant drop in its brightness since then.

“The comet is now almost within our reach – and teaching us to expect the unexpected,” says the camera’s Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research in Germany.

“After its onset of activity at the end April, our images are currently showing a comet back at rest.”

Comet on 30 April

While it is not uncommon for comets to display varying levels of activity, it is the first time that scientists have witnessed changes in dust production from such a close distance.

A comet’s ‘coma’ develops as it moves along its orbit progressively closer to the Sun, the increasing warmth causing surface ices to sublimate and gas to escape from its rock–ice nucleus.

As the gas flows away from the nucleus, it also carries a cloud of tiny dust particles out into space, which slowly expands to create the coma.

The warming continues and activity rises as the comet moves ever closer to the Sun. Eventually, pressure from the solar wind causes some of the material to stream out into a long tail.

As comets are non-spherical and lumpy, this process is often unpredictable, with activity waxing and waning as they warm. The observations made over the six weeks from the end of April to early June show just how quickly the conditions at a comet can change.

Since Rosetta’s instruments were reactivated earlier this year after a long hibernation, the scientific and navigation cameras have been regularly acquiring images to help define Rosetta’s trajectory to the comet.

Using this information, the spacecraft has been making a series of manoeuvres that will slowly bring it in line with the comet before their rendezvous in the first week of August.

Four manoeuvres have been completed already – the most recent was yesterday – with six more to go. The last in the sequence is planned for 6 August, when Rosetta will be 100 km from the comet and will embark on a series of complex manoeuvres to bring it closer still.

Rosetta spacecraft

But today, even six weeks and about 165 000 km out, Rosetta’s science instruments have already started collecting data on the comet’s environment and its evolution. 

For example, Rosetta is capable of measuring the coma and determining the rates at which water and gases such as carbon dioxide are being produced, and how those rates change with time. These measurements will provide insight into the chemical makeup of the comet’s surface and interior.

The plasma environment of the comet can also be assessed as the coma develops and interacts with particles in the solar wind.

Later, as it gets even closer, Rosetta will start collecting gas and dust particles from the coma, and analysing them in its miniaturised onboard laboratories.

“It’s great to have started regularly receiving science data, especially after a long 10 year journey towards our destination,” says Matt Taylor, ESA’s Rosetta project scientist. “The variable activity of the comet shows it definitely has personality, which makes us all the more eager to get there to learn just how it ticks.”

Today, the roughly 4 km-wide comet scales to about one pixel in the narrow-angle camera – meaning no details of the nucleus can be discerned. But within a few weeks, Rosetta will be close enough to see far more: by early July, it should span five pixels and by the start of August, 500 pixels.

With that in mind, we will now begin publishing images on a more regular basis. The next image is foreseen on or around 3 July, and then on a weekly basis until rendezvous on 6 August. The images will be published in the Rosetta image gallery and via the Rosetta mission blog.

One thing seems certain: as Rosetta comes ever closer to its destination, more exciting surprises surely await us.

More about Rosetta: http://www.esa.int/Our_Activities/Space_Science/Rosetta/More_about_Rosetta

More about OSIRIS: http://www.esa.int/Our_Activities/Space_Science/Rosetta/More_about_OSIRIS

Rosetta image gallery: http://www.esa.int/spaceinimages/Missions/Rosetta/(class)/image

Rosetta mission blog: http://blogs.esa.int/rosetta/

Related links:
Rosetta at Astrium: http://www.astrium.eads.net/en/programme/rosetta-1go.html

Rosetta at DLR: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10394/

Ground-based comet observation campaign: http://www.rosetta-campaign.net/home

Images, Text, Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

Best regards, Orbiter.ch

Swarm reveals Earth’s changing magnetism

ESA - SWARM Mission logo.

June 19, 2014

Magnetic field changes

The first set of high-resolution results from ESA’s three-satellite Swarm constellation reveals the most recent changes in the magnetic field that protects our planet.

Launched in November 2013, Swarm is providing unprecedented insights into the complex workings of Earth’s magnetic field, which safeguards us from the bombarding cosmic radiation and charged particles.

Earth's ever-changing magnetic field

This animation above shows changes in Earth’s magnetic field from January to June 2014 as measured by ESA’s Swarm trio of satellites.

The magnetic field protects us from cosmic radiation and charged particles that bombard Earth, but it is in a permanent state of flux. Magnetic north wanders, and every few hundred thousand years the polarity flips so that a compass would point south instead of north. Moreover, the strength of the magnetic field constantly changes – and it is currently showing signs of significant weakening.

The field is particularly weak over the South Atlantic Ocean – known as the South Atlantic Anomaly. This weak field has indirectly caused many temporary satellite ‘hiccups’ (called Single Event Upsets) as the satellites are exposed to strong radiation over this area. Video Credits: ESA/Dot2Dot.

Measurements made over the past six months confirm the general trend of the field’s weakening, with the most dramatic declines over the Western Hemisphere.

But in other areas, such as the southern Indian Ocean, the magnetic field has strengthened since January.

June 2014 magnetic field

The latest measurements also confirm the movement of magnetic North towards Siberia.

These changes are based on the magnetic signals stemming from Earth’s core. Over the coming months, scientists will analyse the data to unravel the magnetic contributions from other sources, namely the mantle, crust, oceans, ionosphere and magnetosphere.

This will provide new insight into many natural processes, from those occurring deep inside our planet to space weather triggered by solar activity. In turn, this information will yield a better understanding of why the magnetic field is weakening.

Earth's magnetic field

“These initial results demonstrate the excellent performance of Swarm,” said Rune Floberghagen, ESA’s Swarm Mission Manager.

“With unprecedented resolution, the data also exhibit Swarm’s capability to map fine-scale features of the magnetic field.”

The first results were presented today at the ‘Third Swarm Science Meeting’ in Copenhagen, Denmark.

Sofie Carsten Nielsen, Danish Minister of Higher Education and Science, highlighted the Danish contribution to the mission. Swarm continues the legacy of the Danish Ørsted satellite, which is still operational, as well as the German Champ mission. Swarm’s core instrument – the Vector Field Magnetometer – was provided by the Technical University of Denmark.

Swarm constellation

Denmark’s National Space Institute, DTU Space, has a leading role – together with 10 European and Canadian research institutes – in the Swarm Satellite Constellation Application and Research Facility, which produces advanced models based on Swarm data describing each of the various sources of the measured field.

“I’m extremely happy to see that Swarm has materialised,” said Kristian Pedersen, Director of DTU Space.

For more information about SWARM mission, visit: http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm/

Third Swarm science meeting: http://congrexprojects.com/2014-events/Swarm/home

Images, Video (mentioned), Text, Credits: ESA/DTU Space/ATG Medialab.

Cheers, Orbiter.ch

Small but significant

ESA - Hubble Space Telescope logo.

19 June 2014

Astronomers use Hubble to study bursts of star formation in the dwarf galaxies of the early Universe

GOODS field containing distant dwarf galaxies forming stars at an incredible rate

They may only be little, but they pack a star-forming punch: new observations from the NASA/ESA Hubble Space Telescope show that starbursts in dwarf galaxies played a bigger role than expected in the early history of the Universe.

GOODS field containing distant dwarf galaxies forming stars at an incredible rate (annotated)

Although galaxies across the Universe are still forming new stars, the majority of the stars were formed between two and six billion years after the Big Bang. Studying this early epoch of the Universe's history is key in order to fully understand how these stars formed, and how galaxies have grown and evolved since.

Concept illustration of a grism image

A new study using data from Hubble's Wide Field Camera 3 (WFC3) has allowed astronomers to take a new step forward in understanding this crucial era by peering at a sample of dwarf galaxies in the early Universe and, in particular, a selection of starburst galaxies within this sample. These starburst galaxies form stars at a furiously fast rate, far above the "normal" star formation rate expected of galaxies. Previous studies of starburst galaxies have focussed on analysing mid-range or high-mass galaxies, leaving out the huge number of dwarf galaxies that existed in this era of prolific star formation.

 Zoom into GOODS field containing distant dwarf galaxies forming stars at an incredible rate

It was not previously possible to study these distant small galaxies closely. Astronomers could only observe small galaxies at smaller distances or larger galaxies at greater distances. The highly sensitive infrared capabilities of WFC3 and its unique grism spectroscopy mode [1] have now allowed astronomers to peer at low-mass dwarf galaxies in the distant Universe and to deduce the contribution of the starburst galaxies to the total star formation within dwarf galaxies at that time.

Pan of GOODS field containing distant dwarf galaxies forming stars at an incredible rate

"We already suspected that dwarf starbursting galaxies would contribute to the early wave of star formation, but this is the first time we’ve been able to measure the effect they actually had," says Hakim Atek of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, lead author of the new paper. "They appear to have had a surprisingly significant role to play during the epoch where the Universe formed most of its stars."

Using grism to find faint dwarf galaxies furiously forming stars

"These galaxies are forming stars so quickly that they could actually double their entire mass of stars in only 150 million years — this sort of gain in stellar mass would take most normal galaxies 1-3 billion years," adds co-author Jean-Paul Kneib, also of EPFL.

This result contributes to a decade-long investigation to understand the links between galaxies' mass and their star-forming activity, and helps to paint a consistent picture of events in the early Universe.

Artist’s impression of starburst regions

As well as adding new insight into how and where the stars in our Universe formed, this new finding will certainly help to unravel the secrets of galactic evolution. It is unusual to find a galaxy in a state of starburst, implying that they are the result of some strange incident, such as a merger, a tidal interaction with another galaxy, or the shockwave from a supernova. By studying these galaxies more closely and understanding how they formed and behaved in their earliest years, astronomers hope to discover the cause of these violent bursts and learn more about galactic evolution throughout the Universe.

A paper based on this research will be published online in The Astrophysical Journal on 19 June 2014.

Notes:

[1] The grism splits up the light from the galaxies, revealing the distribution of brightness and colour in the Universe. This allows scientists to deduce facts about their chemical composition and distance from Earth that would not be possible without such a detailed view from Hubble's space-based perspective.

Notes for editors:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

[1] The international team of astronomers in this study consists of Hakim Atek (EPFL, Switzerland); Jean-Paul Kneib (EPFL, Switzerland); Camilla Pacifici (Yonsei University Observatory, Republic of Korea); Matthew Malkan (University of California, USA); Stephane Charlot (Institut d’Astrophysique de Paris,France); Janice Lee(Space Telescope Science Institute,USA); Alejandro Bedregal ( Minnesota Institute for Astrophysics, USA); Andrew J. Bunker (University of Oxford, UK); James W. Colbert (Spitzer Science Center, USA); Alan Dressler (Observatories of the Carnegie Institution for Science, USA); Nimish Hathi(Aix Marseille University, France); Matthew Lehnert (Institut d’Astrophysique de Paris, France); Crystal L. Martin (Dep’t. of Physics, Univ. of Calif, USA); Patrick McCarthy (Observatories of the Carnegie Institution for Science, USA); and Marc Rafelski (Spitzer Science Center, USA); Nathaniel Ross (University of California, USA); Brian Siana (University of California Riverside, USA); and Harry I. Teplitz (Caltech, USA)
More information

Links:

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

Hubblecast 75: Dwarf Galaxies that Pack a Punch: http://www.spacetelescope.org/videos/heic1412a/

For images and more information about Hubble, visit: http://www.nasa.gov/hubble and http://www.spacetelescope.org/

Images, Text, Credits: NASA, ESA, the GOODS Team and M. Giavalisco (STScI/University of Massachusetts)/Acknowledgement: H.Atek (EPFL, Switzerland) and J-P.Kneib (EPFL, Switzerland)/Videos: ESA/Hubble, NASA, Martin Kornmesser (ESA/Hubble).

Best regards, Orbiter.ch

NASA Astronauts David Leestma and Andrew Thomas Retire

NASA patch.

June 19, 2014

NASA has bid farewell to two veteran astronauts who have retired after a combined 66 years of federal service.

David Leestma has retired after more than 44 years of government service. A veteran of three spaceflights, Leestma served as a space shuttle mission specialist on STS-41G in 1984, STS-28 in 1989 and STS-45 in 1992.

Before joining NASA, Leestma served in the U.S. Navy as a pilot and flew missions in the Mediterranean/North Atlantic areas while assigned to the USS John F. Kennedy. He was selected to join the astronaut corps in 1980. After flying in space, Leestma held multiple technical and leadership assignments, including director of Flight Crew Operations. In his last role, Leestma led the Technical Transfer and Commercialization Efforts office at NASA's Johnson Space Center in Houston.

Image above: NASA astronauts David Leestma and Andrew Thomas are retiring from the astronaut corps after a combined 66 years in federal service. Image Credit: NASA.

"From the day we came together as astronaut classmates, Dave stood out as a remarkable leader, friend, and loyal teammate," said NASA Administrator Charles Bolden, who flew with Leestma on shuttle Atlantis' STS-45 mission. "He possessed seemingly infinite wisdom of the space shuttle and all its systems and never ceased to amaze me with his performance. We wish him the best."

Leestma holds a Bachelor of Science degree from the United States Naval Academy, Annapolis, Maryland, and a Master of Science degree from the Naval Postgraduate School in Monterey, California.

A retired Navy captain, Leestma has logged more than 3,500 flight hours. He ends his NASA career having logged more than 23 days in space on three shuttle missions.

Andrew Thomas also has retired from NASA after more than 22 years of service to the agency.

Thomas, who holds a doctorate in mechanical engineering, was selected to join NASA's astronaut corps in 1992. Before joining NASA, Thomas worked in private industry as a research scientist responsible for designing vehicle aerodynamics, flight controls and propulsion systems.

"Andy is an extraordinary researcher, engineer and astronaut who has done it all in his 22 years as a NASA astronaut," said Janet Kavandi, director of Flight Crew Operations at Johnson. "In his 177 days in space over four missions, Andy served as the payload commander for a dedicated research mission, lived aboard the Russian Mir space station, conducted a spacewalk during an International Space Station assembly mission and served a vital role as a crew member on our crucial Return to Flight mission, STS-114, following the tragic Columbia accident. Since his last flight, Andy has helped shape NASA's future through his tireless work supporting the development of future exploration technology. We will miss him deeply."

Thomas traveled to Mir in 1998 to assist in the transition to space station operations. He was the last American to live on Mir and performed numerous life and physical sciences experiments during the course of his stay. His research aboard Mir provided the framework for the multinational cooperation and collaborative research on today's International Space Station.

Thomas held multiple technical and leadership assignments during his NASA career, including deputy chief of the Astronaut Office.

For Leestma's complete biography, visit: http://www.jsc.nasa.gov/Bios/htmlbios/leestma.html

For Thomas' complete biography, visit: http://www.jsc.nasa.gov/Bios/htmlbios/thomas-a.html

Image (mentioned), Text, Credits: NASA / Joshua Buck / Johnson Space Center / Jay Bolden.

Greetings, Orbiter.ch

Five Things We’ll Learn from Orion’s First Flight Test

NASA - Orion Multi-Purpose Crew Vehicle patch.

June 18, 2014

Image above: This computer-generated art shows the launch abort system still attached and the jettison of the service module fairing panels. Image Credit: NASA.

All the superlatives associated with Orion's first mission this year – farthest a spacecraft for humans has gone in 40 years, largest heat shield, safest vehicle ever built – can be dazzling, no doubt. But the reason engineers are chomping at the bit for Orion's first mission is the promise of crucial flight test data that can be applied to the design for future missions.  Orion only has two flight test opportunities before astronauts climb aboard for the first crewed mission in 2021 – so gleaning the maximum information possible from Exploration Flight Test (EFT)-1 in December (and later, Exploration Mission-1 in 2017) is of the highest priority. Here are the top five things the engineers will be paying attention to:

1. Launch Abort System Separation – The launch abort system (LAS) is a key reason that Orion is intended to become the safest spacecraft ever built. In an emergency it could activate to pull the crew module and the astronauts it will carry away from the launch pad and the rocket in milliseconds. Hopefully it’s never needed, and since no crew will fly on EFT-1 the rescue system won’t be active.

NASA Orion Exploration Mission 1 Animation

But even when a launch goes perfectly, the 904-pound LAS jettison motor has to perform flawlessly. If it doesn’t get rid of the LAS 6 minutes and 20 seconds into the mission, there will be no landing – the LAS protects the crew module during ascent, but to do so, it blocks the parachutes that allow Orion to safely splashdown.

Image above: The three panels or fairings encapsulating a stand-in for Orion’s service module successfully detach and fall into the Fairing Catch System during a test Nov. 6, 2013 at Lockheed Martin’s facility in Sunnyvale, Calif. Image Credit: Lockheed Martin.

The Launch Abort System separation is just the first of 17 separations or jettisons that have to happen exactly as planned for the mission to be successful.

2. Parachute Deployment – For EFT-1, Orion will travel 3,600 miles above the Earth so that when it performs its deorbit burn, it will come screaming back into the Earth’s atmosphere at almost 20,000 miles per hour. Before it splashes down in the Pacific Ocean, it needs to slow down to 1/1000th of its entry speed – a relatively gentle 20 miles per hour.

Image above: A test version of NASA’s Orion spacecraft touches down in the Arizona desert after its most complicated parachute test to date. Image Credit: NASA.

Earth’s atmosphere does its part to put on the brakes, but to make landing survivable, Orion relies on its parachute system – primarily two drogue parachutes and three massive mains that together would cover almost an entire football field. They’ve been tested on Earth; test versions of Orion have been dropped from airplanes with a multitude of failure scenarios programmed into the parachute deployment sequence in an effort to make sure that every possibly problem is accounted for.

NASA Tests Orion Spacecraft Parachute Jettison Over Arizona

But the sheer number of possible problems to be tested indicates how complicated the system is – each parachute must deploy at the exact right time, open to the exact right percentages in the exact right stages, and be cut away exactly as planned. And no test on Earth can exactly simulate what the spacecraft will really experience on its return from space.

3. Heat Shield Protection – Before the parachutes even get a chance to deploy, Orion has to make it safely through Earth’s atmosphere. The reason that Orion is traveling so far and coming back in so fast is to give the heat shield a good workout – the idea is to get as close as possible to the temperatures Orion would experience during a return from Mars. At the speed it will be traveling, the temperature should reach almost 4,000 degrees Fahrenheit. At that same temperature, a nuclear reactor would melt down.

Image above: This computer-generated art depicts Orion's heat shield protecting the crew module as it enters the Earth's atmosphere. Image Credit: NASA.

Standing between the crew module and all that heat is no more than 1.6 inches of Avcoat, a material that’s designed to burn away rather than transfer the temperatures back to Orion. Some 20 percent of the Avcoat will erode during the spacecraft’s journey back to Earth, and although it’s not the first time the materials has been used for this purpose, at 16.5 feet wide, Orion’s heat shield is the largest ever built. Technicians filled with Avcoat each of the 320,000 honeycomb cells that make up the shield’s structure by hand, then machined them to the precise fractions of inches called for by the design. Getting it exactly right is all that will get Orion through one of the most dynamic periods of its mission.

4. Radiation Levels – Traveling 15 times farther into space than the International Space Station will take Orion beyond the radiation protection offered by Earth’s atmosphere and magnetic field. In fact, the majority of EFT-1 will take place inside the Van Allen Belts, clouds of heavy radiation that surround Earth. No spacecraft built for humans has passed through the Van Allen Belts since the Apollo missions, and even those only passed through the belts – they didn’t linger.

Future crews don’t plan to spend more time than necessary inside the Van Allen Belts, either, but long missions to deep space will expose them to more radiation than astronauts have ever dealt with before. EFT-1’s extended stay in the Van Allen Belts offers a unique opportunity to see how Orion’s shielding will hold up to it. Sensors will record the peak radiation seen during the flight, as well as radiation levels throughout the flight, which can be mapped back to geographic hot spots.

Image above: The Orion crew module for Exploration Flight Test-1 is shown in the Final Assembly and System Testing (FAST) Cell, positioned over the service module just prior to mating the two sections together. Image Credit: NASA/Rad Sinyak.

5. Computer Function – Orion’s computer is the first of its kind to be flown in space. It can process 480 million instructions per second. That’s 25 times faster than the International Space Station’s computers, 400 times faster than the space shuttle’s computers and 4,000 times faster than Apollo’s.

But to operate in space, it has to be able to handle extreme heat and cold, heavy radiation and the intense vibrations of launches, aborts and landings. And it has to operate through all of that without a single mistake. Just restarting the computer would take 15 seconds; and while that might sound lightning fast compared to your PC, you can cover a lot of ground in 15 seconds when you’re strapped to a rocket.

For more information about the Orion program, visit: http://www.nasa.gov/exploration/systems/mpcv/

Images (mentioned), Videos, Text, Credit: NASA.

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