Posted on by Nancy Atkinson

Where In The Universe Challenge #19

Here’s another “Where In The Universe” challenge, and in keeping with the Mission:Impossible theme from the previous post, your mission, should you choose to accept, is to identify where in the universe this image was taken. Give yourself extra points if you can name the spacecraft responsible for the image. Does everyone have their watches synchronized and secret decoder image detectors ready? It’s fairly certain this website will not self destruct in five seconds, so take your time looking at the image. As always, no peeking below before you make your guess.

This is an image of a dune field on Mars in Wirtz Crater, and yes, the white material is actually frost on the dunes. It was taken by the HiRISE Camera on the Mars Reconnaissance Orbiter. I came across this image while searching for more evidence of frost on Mars, other than what the Phoenix and Viking Landers had imaged. Just to make sure I wasn’t seeing things, I checked in with Nathan Bridges from JPL and the HiRISE Team about this image. He explains, “The white material is frost, composed of water and/or carbon dioxide. When this image was taken, it was winter in this part of Mars and it gets cold enough for water to condense out of the atmosphere and even for the atmosphere itself to freeze (the atmosphere is made of CO2) The color is approximately what you would see on Mars, but is enhanced to bring out detail.”

This image was taken on January 7, 2007 at about 3:50 in the afternoon, Mars local time, as HiRISE was 254 km (158.7 miles) above Mars’ surface. Wirtz Crater is located at -48 degrees latitude and 334.6 degrees longitude east.

For more information about this image, or to get higher resolution versions of the entire image swath, check out HiRISE’s website.

Posted on by Nancy Atkinson

Asteroid Imposters

Are some asteroid masked of their true identity?

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A frequent plot device in the old “Mission: Impossible” television show was the special masks the IMF team used so they could impersonate anyone. Viewers were often surprised to find out who ended up being an imposter. Similarly, astronomers and planetary scientists are considering that a fair amount of Near Earth Objects (NEOs) aren’t what they appear: they could be comets impersonating asteroids. Paul Abell, from the Planetary Science Institute says between five and ten percent of NEOs could be comets that are being mistaken for asteroids, and Abell is working on ways to make unmasking them a mission that’s possible.

Some NEOs could be dying comets, those that have lost most of the volatile materials that create their characteristic tails. Others could be dormant and might again display comet-like features after colliding with another object, said Abell. He is using NASA’s Infrared Telescope Facility at the Mauna Kea Observatories in Hawaii and the MMT telescope on Mount Hopkins, south of Tucson, Ariz., to uncover observational signatures that separate extinct/dormant comets from near-Earth asteroids.

This is important for a couple of reasons. First, dormant comets in near-Earth space could become supply depots to support future exploration activities with water and other materials. Second, like other NEOs, they could pose a threat to Earth if they are on a collision course with our planet. Third, they can provide data on the composition and early evolution of the solar system because they are thought to contain unmodified remnants of the primordial materials that formed the solar system.
Comet Tempel 1. Credit: NASA/U of Maryland
Unlike rocky asteroids that blast out craters when they slam into Earth, comets are structurally weak and likely to break up as they enter the atmosphere, leading to a heat and shockwave blast that would be much more devastating than the impact from an asteroid of the same size.

Low-activity, near-earth comets flashed onto the planetary-science radar screen in 2001, when NEO 2001 OG108 was discovered by the Lowell Observatory Near Earth Asteroid Search telescope. It had an orbit similar to comets coming in from the Oort Cloud, but had no cometary tail. But in early 2002 when it came closer to the sun, the heat vaporized some of the comet’s ice to create the clouds of dust and gas that make up the comet’s coma and tail. It was then reclassified as a comet.

“That’s what started me on this line of reasoning and scientific investigation,” Abell said.
By combining orbital data with spectra and the albedos (brightness) of these objects, Abell hopes to identify which are low-activity comets and where they are coming from.
“Are all these comets made of the same type of material or are they different?” Abell asked. “If they’re composed of different materials, they may have different spectral signatures, and our preliminary work on Jupiter-family comets and Halley-type comets shows that this may be true. Why is that? Is it something to do with the initial conditions of their formation regions? Or is it due to the different environments in which they spend most of their time?”

“All this is important to understanding their internal makeup, which will give us data on the material composition and evolution of the early solar system,” he added.

Source: PSI Press Release

Posted on by Nancy Atkinson

Astronomers Link Telescopes to Zoom In On Milky Way’s Black Hole

Computer simulation of what a "hot spot" of gas orbiting a black hole would look like in an extremely high-resolution image. Credit: Avery Broderick (CITA) & Avi Loeb (CfA)

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An international team of astronomers has obtained the closest views ever of what is believed to be a super-massive black hole at the center of the Milky Way galaxy. The astronomers linked together radio dishes in Hawaii, Arizona and California to create a virtual telescope more than 2,800 miles across that is capable of seeing details more than 1,000 times finer than the Hubble Space Telescope. The target of the observations was the source known as Sagittarius A* (“A-star”), long thought to mark the position of a black hole whose mass is 4 million times that of the sun.

Using a technique called Very Long Baseline Interferometry (VLBI), the astronomers studied the radio waves coming from Sagittarius A*. In VLBI, signals from multiple astronomy telescopes are combined to create the equivalent of a single giant telescope, as large as the separation between the facilities. As a result, VLBI yields exquisitely sharp resolution.

They detected structure at a tiny angular scale of 37 micro-arcseconds – the equivalent of a baseball seen on the surface of the moon, 240,000 miles distant. These observations are among the highest resolution ever done in astronomy.

“This technique gives us an unmatched view of the region near the Milky Way’s central black hole,” said Sheperd Doeleman of MIT, first author of the study that will be published in the Sept. 4 issue of the journal Nature.

Computer animation illustrating a spinning black hole. Credit: NASA
Computer animation illustrating a spinning black hole. Credit: NASA

Though Sagittarius A* was discovered three decades ago, the new observations for the first time have an angular resolution, or ability to observe small details, that is matched to the size of the black hole “event horizon” — the region inside of which nothing, including light, can ever escape.

With three telescopes, the astronomers could only vaguely determine the shape of the emitting region. Future investigations will help answer the question of what, precisely, they are seeing: a glowing corona around the black hole, an orbiting “hot spot,” or a jet of material. Nevertheless, their result represents the first time that observations have gotten down to the scale of the black hole itself, which has a “Schwarzschild radius” of 10 million miles.

The concept of black holes, objects so dense that their gravitational pull prevents anything including light itself from ever escaping their grasp, has long been hypothesized, but their existence has not yet been proved conclusively. Astronomers study black holes by detecting the light emitted by matter that heats up as it is pulled closer to the event horizon. By measuring the size of this glowing region at the Milky Way center, the new observations have revealed the highest density yet for the concentration of matter at the center of our galaxy, which “is important new evidence supporting the existence of black holes,” said Doeleman.

“This result, which is remarkable in and of itself, also confirms that the 1.3-mm VLBI technique has enormous potential, both for probing the galactic center and for studying other phenomena at similar small scales,” said co-author Jonathan Weintroub.

The team plans to expand their work by developing novel instrumentation to make more sensitive 1.3-mm observations possible. They also hope to develop additional observing stations, which would provide additional baselines (pairings of two telescope facilities at different locations) to enhance the detail in the picture. Future plans also include observations at shorter, 0.85-mm wavelengths; however, such work will be even more challenging for many reasons, including stretching the capabilities of the instrumentation, and the requirement for a coincidence of excellent weather conditions at all sites.

Source: Harvard Smithsonian press release

Posted on by Nancy Atkinson

Understanding the “Superotation” Winds of Venus

Venus observed by Venus Express. Credit: ESA

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Astronomers observing Venus back in the 1960’s discovered that the top level of Venusian cloud layers moved very rapidly, orbiting the planet in only four Earth days, compared to the planet’s own rotation of 243 Earth days. This phenomenon is called the “superotation” of Venus. The winds carrying these clouds travel at 360 km/hr, while winds at the planet’s surface are just a breeze at a few km/hr, and there have been indications that at times there’s no wind on Venus’ surface. This unique characteristics have been perplexing, but new observations carried out with ESA’s Venus Express, in orbit around Venus since April 2006, are offering insights to the planet’s atmosphere. Scientists have been able to determine in detail the global structure of the winds on Venus at the different levels of clouds while, at the same time, observe unexpected changes in the wind speeds, and which will help to interpret this mysterious phenomenon.

Venus is similar to Earth in size, and sometimes is called Earth’s sister planet. Nevertheless, it is quite different in other aspects. It’s slow rotation is also retrograde, or in the opposite direction to that of our planet, i.e. from East to West. It’s dense atmosphere of carbon dioxide with surface pressures 90 times that of Earth (equivalent to what we find at 1000 meters below the surface of our oceans), causes a runaway greenhouse effect that raises the surface temperatures up to 450ºC, to such as extent that metals like lead are in a liquid state on Venus.

At a height of between 45 km and 70 km above the surface there are dense layers of sulfuric acid clouds which totally cover the planet. Our continued explorations and observations of Venus seemed to indicate that the “superotation” was a permanent phenomenon. A team led by scientists and the University of Basque Country used images recorded by both day and night on Venus with the VIRTIS spectral camera on board the Venus Express, to measure these clouds over several months and have discovered new aspects of the “superotation.”

First, between the equator and the median latitudes of the planet there dominates a superotation with constant winds blowing from East to West. The wind speeds within the clouds decrease with height, from 370 km/h to 180 km/h. At these median latitudes, the winds decrease to a standstill at the pole, where an immense vortex forms. Other aspects of the superotation are that wind movements from north to south, or meridional, are very weak, about 15 km/h.

Second, unlike what was previously believed, the superotation appears to be not so constant over time. “We have detected fluctuations in its speed that we do not yet understand,” said the team of scientists, led by Agustín Sánchez Lavega. Moreover, for the first time they observed “the solar thermal tide” effect at high latitudes on Venus. “The relative movement of the Sun on the clouds and the intense heat deposited on them makes the superotation more intense at sunset than at sunrise”, they stated in their paper, which was published in Geophysical Research Letters.

“Despite all the data brought together, we are still not able to explain why a planet than spins so slowly has hurricane global winds that are much more intense than terrestrial ones and are, moreover, concentrated at the top of its clouds,” said Lavega. “This study has enabled advances to be made in a precise explanation of the origin of superotation in Venusian winds as well as in the knowledge of the general circulation of planetary atmospheres.”

Source: University of Basque Country press release

Posted on by Tammy Plotner

Observing Alert: Possible New Dwarf Nova In Andromeda

NvAnd08

[/caption]According to AAVSO Special Notice #122 prepared by M. Templeton, there’s a possible new WZ Sge-type dwarf nova located in Andromeda. The alert was posted yesterday and intial observations were sent in within the last 48 hours. For more information, read on…

AAVSO Special Notice #122

Multiple observers have confirmed the detection of an optical transient in Andromeda whose photometric behavior is thus far consistent with its classification as a WZ Sge-type dwarf nova system. The object was submitted to the CBAT unconfirmed objects list (D. Green, editor) by an unidentified observer on 2008 September 01.6.

A comprehensive list of the numerous follow-up observations made in Russia was published and an announcement of apparent very short period superhumps (P ~ 0.055 days) was made in vsnet-alert 10478. A comparison of the field with archival POSSII plates by D. Denisenko et al suggests the progenitor is very faint, with a blue magnitude of 21 or fainter. The reported outburst magnitudes of approximately V=12.5 then suggest an amplitude of at least 8 magnitudes.

M. Andreev (Terskol, Russia) obtained the following coordinates for the object using a 28-cm telescope:

RA: 02h 00m 25.42s , Dec: +44d 10m 18.4s (J2000)

Finder Chart
Finder Chart

Several other sets of coordinates have been published by Russian observers on the page noted above, and most are within a few tenths of an arcsecond.

Observations of this new object, including time-series photometry, are encouraged. The object has not been formally named, and the WZ Sge classification has not been definitively confirmed. Observers are asked to follow the object during the next several weeks. The object may fade and rebrighten, so please submit all observations including “fainter-than” estimates. Instrumental time-series observations are also encouraged to confirm the presence of superhumps and (if possible) define the period.

Please submit all data to the AAVSO using the name and/or AUID pair VSX J020025.4+441018 , AUID 000-BFT-799.

Nova Andromeda Photo courtesy of AstroAlert.

Posted on by Tammy Plotner

NGC 7023 – ‘Iris From The Dust’ by Kent Wood

NGC 7023 - Kent Wood

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As the very last of the summer flowers bloom in the dusty grasses of the northern hemisphere, so a cosmic flower blooms in the dusty star fields of the northern constellations. While this image conjures up a vision of an iris delicately opening its 6 light year wide petals some 1300 light years away in Cepheus, this bit of flora is anything but a pretty little posey…

NGC 7023 was first discovered by Sir William Herschel on October 18, 1794 and since that time it has had a rather confusing catalog history. As usual, Herschel’s notes made the correct assumption of “A star of 7th magnitude. Affected with nebulousity which more than fills the field. It seems to extend to at least a degree all around: (fainter) stars such as 9th or 10th magnitude, of which there are many, are perfectly free from this appearance.” So where did the confusion come in? It happened in 1931 when Per Collinder decided to list the stars around it as a star cluster Collinder 429. Then along came Mr. van den Berg, and the little nebula became known as van den Berg 139. Then the whole group became known as Caldwell 4! So what’s right and what isn’t? According to Brent Archinal, “I was surprised to find NGC 7023 listed in my catalog as a star cluster. I assumed immediately the Caldwell Catalog was in error, but further checking showed I was wrong! The Caldwell Catalog may be the only modern catalog to get the type correctly!”

But what isn’t wrong is the role molecular hydrogen plays in formations like the Iris nebula. In a gas rich interstellar region near a a hot central object such as the Herbig Be star HD 200775, atomic and molecular excitation occurs. The resulting fluorescence produces a rich ultraviolet and infrared spectrum… and interstellar emissions. Just what kind of interstellar emissions might occur from a region like the Iris Nebula? According to the 2007 Micron Spitzer Spectra Research done by Sellgren (et al) at Ohio State: “We consider candidate species for the 18.9 µm feature, including polycyclic aromatic hydrocarbons, fullerenes, and diamonds.”

Now, we’re not only bringing you space flowers… but diamonds in the rough.

The discovery of aromatic hydrocarbons, diamonds, and fullerenes in interstellar space is a new puzzle to space science. According to the work of K. Sellgren; “Emission from aromatic hydrocarbons dominates the mid-infrared emission of many galaxies, including our own Milky Way galaxy. Only recently have aromatic hydrocarbons been observed in absorption in the interstellar medium, along lines of sight with high column densities of interstellar gas and dust. Much work on interstellar aromatics has been carried out, with astronomical observations and laboratory and theoretical astrochemistry. In many cases, the predictions of laboratory and theoretical work are confirmed by astronomical observations but, in other cases, clear discrepancies exist that provide problems to be solved by a combination of astronomical observations, laboratory studies, and theoretical studies. …Studies are needed to explain astrophysical observations, such as a possible absorption feature due to interstellar ‘diamonds’ and the search for fullerenes in space.”

What this comes down to is carbon nanoparticles are out there in the interstellar medium. Polycyclic aromatic hydrocarbons – or PAHs – are molecules constructed of benzene rings that look like segments of single layers of graphite. If you were here on Earth? You’d find them everywhere… coming out of your car’s exhaust, stuck to the top of your grill, coating the inside of your fireplace. Apparently we’re picking up the signature of PAHs in Unidentified Infra-Red emission bands, Diffuse Interstellar Bands and a UV extinction bump in NGC 7023 – but what the heck is it doing there?

According to research, it’s entirely possible these PAHs may have formed in the dust when the grains collided and fractured – releasing free PAHs. They could have grown between smaller unsaturated hydrocarbon molecules and radicals in the remnants of carbon rich stars. Science just doesn’t really know. But one thing they do know… Once a PAH is there, it is extremely stable and extremely efficient at rapidly re-emitting the absorbed energy at infra-red wavelengths.

Take the time to view the Iris Nebula yourself. Located in Cepheus (RA 21:00.5 Dec +68:10) and around magnitude 7, this faint nebula can be achieved in dark skies with a 114-150mm telescope, but larger aperture will help reveal more subtle details since it has a lower surface brightness. Take the time at lower power to reveal the dark dust “lacuna” around it reported so many years ago, and to enjoy the true beauty of this Caldwell gem. Remember your astronomy lesson, too! According to O. Berne, who also studied NGC 7023 just this year, “Unveiling the composition, structure and charge state of the smallest interstellar dust particles remains one of today’s challenges in astrochemistry.”

We would like to thank AORAIA member, Ken Wood for this incredibly inspiring image!

Posted on by Ian O'Neill

Russian Progress Supply Ship is Dropped from Space Station to Burn Next Week

A previous Progress approach to the Space Station over Earth (NASA)

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In a dress rehearsal for the disposal of the European Automated Transfer Vehicle (ATV) in two days time, the Russian Progress 29 resupply ship was undocked from the International Space Station (ISS) on Monday from its Earth-facing berth on the station’s Russian Zarya control module. The vessel, having performed its resupply duties back in May, has now been filled with waste from the crew and sent on its week-long journey toward a fiery re-entry. But the tough automated resupply ship still has some work to do, it will carry out some experimental rocket tests before it makes its final plunge over the Pacific Ocean…

The Russian automated resupply vessel has been overlooked recently. This unmanned craft has a long history of space supply tasks, ferrying food, water, equipment and other supplies to the orbital crews and then being filled with rubbish to be disposed of during re-entry. The current expendable Progress vehicle, the Progress M (interestingly based on the manned Soyuz design), was first launched in 1989 to service the Mir Space Station. 43 flights later, it was chosen as the principal resupply vehicle for the ISS. The current Progress mission, Progress 29, marks the 29th Progress flight to the orbital outpost, but unfortunately, like all the Progress flights before it the ship has undocked and it will begin deorbit manoeuvres to burn up in the atmosphere.

According to NASA, the undocking procedure was completed as expected at 3:46 pm EDT, Monday afternoon. “It went very well, exactly as planned,” stated NASA spokesperson Kelly Humphries at the Johnson Space Center in Houston. Russian Federal Space Agency officials added that Progress 29 will remain in orbit until September 9th to carry out experiments on the plasma environment surrounding its engines. Once complete, the craft will be instructed to begin its final kamikaze task and plunge into the atmosphere over the South Pacific. Should any charred remains be left over after the burn, the debris will fall safely into a pre-designated area of the ocean.

Progress 29 was launched on May 14th and docked with the ISS two days later. This mission replaced Progress 28, which in April had also been unceremoniously dropped from space. Progress 29 delivered 2.3 tonnes of supplies to the ISS crew which currently include cosmonauts Sergei Volkov and Oleg Kononenko with astronaut Greg Chamitoff.

But this is only the first part of ISS dumping duties this week. On Friday, ESA Jules Verne will end its work (the first ever ATV mission), be filled with station trash and also dropped from orbit. I’m sure the ATV looked down nervously on Progress 29 as it disappeared from view knowing it’s only two days from the long drop back to Earth…

Source: Space.com

Posted on by Nancy Atkinson

Explosions on the Moon

Meteor strike on Moon recorded by Robert Spellman on August 9, 2008

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Meteor showers are great fun. The streaks and flashes create a special type of astronomical fireworks. But there are some people out there who enjoy meteor showers in a different way. They don’t watch the meteors. Instead, they watch the moon. There are fireworks there, too, in the form of explosions — equivalent to about 100 pounds of TNT — when meteors hit the lunar surface.

On August 9th, during the Perseid meteor shower, a couple of amateur astronomers fixed their cameras on the Moon and watched meteoroids slam into the lunar surface. Silent explosions produced flashes of light visible a quarter of a million miles away on Earth. It was a good night for “lunar Perseids.”

Meteor strike on the moon imaged by George Varros.
Meteor strike on the moon imaged by George Varros.

“I love watching meteor showers this way,” says George Varros, who recorded the impact shown above from his home in Mt. Airy, Maryland. The flash, which lit up a nighttime patch of Mare Nubium (the Sea of Clouds), was a bit dimmer than 7th magnitude, which Varros said was “an easy target for my 8-inch telescope and low-light digital video camera.”

Hours later, another Perseid struck, on the western shore of Oceanus Procellarum (the Ocean of Storms). This time it was Robert Spellman of Azusa, California, who caught the flash. “It’s exciting to witness these explosions in real time,” he says. “I used a 10-inch telescope and an off-the-shelf Supercircuits video camera.” Spellman has a website about his observations.

NASA’s Meteoroid Environment Office watches the moon during meteor showers, too. Rob Suggs at the Marshall Space Flight Center and his team have recorded more than 100 lunar explosions since 2005. “We monitor lunar meteors in support of NASA’s return to the Moon,” Suggs says. “The Moon has no atmosphere to protect the surface, so meteoroids crash right into the ground. Our program aims to measure how often that happens and answer the question, what are the risks to astronauts?”

But NASA’s official lunar meteor observatories in Alabama and Georgia were both off-line on August 9, so the NASA team didn’t see how many Perseids were hitting the Moon that night.

“This shows how amateur astronomers can contribute to our research,” points out Suggs. “We can’t observe the Moon 24-7 from our corner of the USA. Clouds, sunlight, the phase of the Moon—all these factors limit our opportunities. A global network of amateur astronomers monitoring the Moon could, however, approach full coverage.”

Suggs hopes other amateurs will take up this hobby of watching the moon during meteor showers, not only to improve NASA’s lunar impact statistics, but also to support the agency’s LCROSS mission: In 2009, the Lunar CRater Observation and Sensing Satellite (LCROSS) will intentionally dive into the Moon, producing a flash akin to a natural lunar meteor. Unlike natural meteoroids, which hit the Moon in random locations, LCROSS will carefully target a polar crater containing suspected deposits of frozen water. If all goes as planned, the impact will launch debris high above the lunar surface where astronomers can search the ejecta for signs of H2O. The impact flash (if not hidden by crater walls) and the debris plume may be visible to backyard telescopes on Earth. Here’s more details on the LCROSS impact.

If you’re interested in watching for meteor impacts on the moon, NASA has a FAQ page, and telescope tips.

News Source: Science@NASA

Posted on by Nancy Atkinson

Pushing the Polite Boundaries of Science About Dark Matter

Hubble and Chandra composite image showing possible dark matter. Credit: X-ray(NASA/CXC/Stanford/S.Allen); Optical/Lensing(NASA/STScI/UC Santa Barbara/M.Bradac)

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Rumors are spinning faster than a neutron star about the possibility that a European satellite mission called PAMELA may have made a direct detection of dark matter, the mysterious particles thought to make up as much of 85% of all matter in the Universe. Word got out in August at a conference about dark matter in Stockholm, Sweden where the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) team presented their preliminary findings to a few selected physicists. What information has leaked out says the satellite has detected more positrons than can be explained by known physics and that this excess exactly matches what dark matter particles would produce if they were annihilating each other at the center of the galaxy. But the PAMELA team is not allowing any more information to be made public, until they re-analyze their data and allow other scientists to evaluate and verify the findings. This is good, if not wonderful, in all respects – making sure their findings are peer reviewed before publishing their work and going public. (Does anyone remember the cold fusion debacle?) But in what seems to cross the line of good science — as well pushing the boundaries of what is just plain polite, two other scientists have published an abstract based on what was revealed to them at the conference.

Ever since cosmologists “concocted” dark matter to explain the matter that was obviously missing from the universe’s equation, scientists have speculated, worked, created models and worked some more to determine exactly what dark matter is. Recent findings (see here and here)seem to be bringing us closer to finding this mysterious substance, providing clues to what this stuff might be. The PAMELA data seems to point towards positrons, or anti-electrons.

Marco Cirelli from the CEA near Paris in France and Alessandro Strumia from the Università di Pisa in Italy presented their own analysis of the PAMELA data in this abstract. They say the data agrees with their own model called Minimal Dark Matter in which the particle responsible is called the “Wino.” They do reference their own work but interestingly, many of their references are from talks given at the conference on August 18-22. At one point they note, “The preliminary data points for positron and antiproton fluxes plotted in our figures have been extracted from a photo of the slides taken during the talk, and can thereby slightly differ from the data that the PAMELA collaboration will officially publish.”

Is this just a desire to “publish” something first, or is this real science?

Sources: ArXiv, ArXiv blog, Nature

Posted on by Nancy Atkinson

Countdown to Asteroid Flyby

Artist impression of Rosetta and Asteroid 2867 Steins. Credit: ESA

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Time critical is approaching for the Rosetta spacecraft and it’s flyby of the asteroid 2867 Steins. Closest approach is expected on September 5, at 20:58 CEST, (Central European Summer Time), 2:58 pm EDT (US Eastern Daylight Time). To help the public follow the flyby, the Rosetta team now has a blog available, and a timeline has also been posted. At the time of closest approach, Rosetta is planned to be 800 km from the asteroid, passing by at a speed of 8.6 km/s relative to Steins. Both Rosetta and Steins will be illuminated by the Sun, providing an excellent opportunity for science observations.

Although most scientific observations will take place in the few hours around closest approach, several instruments will be switched on for a longer time around the event.

Between 40 and 20 minutes before closest approach, Rosetta will be flipped and the spacecraft will switch to a specially designed asteroid fly-by mode, an optimal configuration that supports the intensive observation and tracking activity of the on-board instruments. The first images and results will be available for presentation to the media during a press conference on Saturday, September 6 at 12:00 CEST.

Asteroid Steins orbit. Credit: ESA
Asteroid Steins orbit. Credit: ESA

The timeline is as follows (more details are available in the Rosetta Blog — all times CEST (Central European Summer Time):

1 September
02:20 Instruments switched on (except OSIRIS which was already on for the navigation campaign)

4 September
07:20-11:20 Slot for possible trajectory correction manoeuvre (36 hours before closest approach)
13:20-18:20 Last opportunity to acquire images for optical navigation campaign

5 September
07:20-10:20 Slot for possible trajectory correction manoeuvre (12 hours before closest approach)
10:20 Navigation cameras switch to tracking mode – initially both used, then use CAM ‘A’ only (to be decided)
11:00 Uplink fly-by commands for asteroid fly-by mode (AFM)
Includes an update to the command profile already on board & the final updated AFM commands (only if 1 CAM at least is tracking)
20:18-20:38 Spacecraft flip over
20:39 Spacecraft switches automatically to asteroid fly-by mode
20:56 Sun illuminates Rosetta from the back and the asteroid fully
20:58 Closest approach, at a planned distance of 800 km from the asteroid
22:27 First post-fly-by acquisition of signal (AOS) – telemetry received via NASA’s Goldstone ground station
22:30 Start of science data download via Goldstone

6 September
12:00 Live streaming of Rosetta Steins fly-by press conference from the European Space Operations Centre begins
13:00 Images from fly-by published on ESA web
15:00 End of press conference streaming
16:01 End of reception of first set of science data

News Source: ESA