[/caption]We know that atoms are parts of an element that can not naturally be broken down any further. What is the atom structure, though? The concept that atoms existed was first written about in ancient India in the 6th century B.C. The theory stayed just that, a theory, until the late 19th century. As microscopes and spectrometers developed, scientists were better able to develop their theories and finally observe the small scale structure of elements.
Atoms are made up of three particles: protons, electrons, and neutrons. Electrons are the smallest and lightest of the the three particles and they have a negative charge. The protons are much heavier and larger than electrons. Protons have a positive electrical charge. Neutrons are as large and massive as protons, but do not have an electrical charge at all. Every atom contains these particles in varying numbers. To understand exactly how small an atom is, you have to know that a single hydrogen atom is 5 x 10-8mm in diameter. It would take at least 60 million hydrogen atoms to fill the space of any one of the letters on this page.
The simplest atom is that of hydrogen: 1 electron and one proton. In every stable, neutrally charged atom there is the exact same number of protons as electrons. These particles work together like two magnets with the opposite electrical charges attracting each other. The reason that they do not crash together is that the electron is constantly revolving around the nucleus(usually a proton/neutron combination, but hydrogen, uniquely, does not contain any neutrons). The centrifugal force of the electron keeps it in place at a constant distance from the nucleus. Actually, representing the electron as spinning around the nucleus is somewhat misleading. Electrons act like waves. That is how they are seen on a spectrometer. It is just easier to think of them as spinning around.
Atoms can have an electrical charge, positive or negative. This happens when an atom gains or loses electrons. The number of protons never changes in an atom. More electrons means a negative charge and fewer means a positive charge. Once an atom has an electrical charge it is called an ion. In an ion the atomic number and atomic mass do not change from the original. If an atom were to gain or lose neutrons it becomes an isotope. Remember the hydrogen atom I mentioned earlier. It did not have a neutron attached to its proton. If it gains a neutron it become an isotope called deuterium. Since the atomic mass is the total of the number of protons and neutrons, an isotope would have a different atomic mass, but the same atomic number as the original atom.
Alright, that is a very basic rendition of atom structure. The University of Colorado has an interesting website to help you understand more complex versions of atoms. Here on Universe Today we have a great article about the many theorized models of the atom. We discussed ions. Astronomy Cast offers a good episode about interstellar travel using ion propulsion.
Naiad is one of the 13 moons of Neptune. Neptune was not discovered until 1989 through studying photos taken by the Voyager 2 probe. Thus, the Voyager Science Team is credited with its discovery. It was the last moon discovered by the probe, which helped scientists find five moons altogether. The last five new moons were discovered in the first decade of the 21st century.
The satellite was given its official name on September 16, 1991. At first the satellite was designated S/1989 N 6. Neptune’s moons are named after figures from mythology that have to do with the Roman god Neptune – or its Greek equivalent Poseidon – or the oceans. The irregular satellites of Neptune are named after the Nereids, which are the daughters of Nereus and Doris, who are Neptune’s attendants in Roman mythology. Naiad was named after a type of nymph in Greek mythology that presided over brooks, streams, wells, springs – all fresh water things.
Naiad is the closest satellite to the planet Neptune. It orbits about 48,230kilometers from the top of the planet’s atmosphere. Naiad is a very small satellite with a diameter of only approximately 58 kilometers. That is about one-sixtieth the size of the Earth’s Moon. Naiad’s mass is so small that it is only 0.00001% of the Moon’s mass. It takes Naiad less than one day – seven hours and six minutes to be precise – to orbit Neptune because of its proximity to its planet. With a decaying orbit, the satellite may crash into Neptune or be ripped apart and become part of one of its planetary rings. This may happen soon.
Naiad is an irregularly shaped satellite, which some have compared to a potato. In one of the pictures Voyager 2 took of it, the moon appears to be elongated because of smearing in the picture. Astronomers believe that the moon is made up of fragments from Neptune’s original satellites, some of which were destroyed when Neptune’s gravity captured Triton as a satellite. They do not think the moon has changed at all geologically since it was formed.
After the Voyager 2 probe passed by Neptune, the planet and its satellites have been studied by many observatories as well as the Hubble Space Telescope and the Keck telescope. Although scientists have been trying to observe Naiad and some of the other smaller irregular moons, scientists still do not know very much about the satellite. This is especially true because Naiad and similar satellites are so small.
Falcon 9 now vertical on the launchpad at Cape Canaveral. Credit: Chris Thompson/SpaceX
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Is the future here? Over the weekend, SpaceX rolled their Falcon 9 launch vehicle out to the launchpad at Space Launch Complex 40, Cape Canaveral. If all systems check out, SpaceX looks to do an engine test sometime this week, which should provide some dramatic rumbling and shaking here in Florida. The rocket measures 47 meters long (154 feet) and 4 meters (12 feet) wide, and for the upcoming test launch (date currently not set), the payload will be a dummy of the company’s Dragon capsule being developed to carry equipment to the International Space Station for NASA.
Falcon 9 at Cape Canaveral. Credit: SpaceX
The word around Cape Canaveral is that the range has been reserved for March 8, but SpaceX won’t provide any specific potential launch dates; instead giving a range of sometime between March and May. SpaceX founder Elon Musk has said the Range date is “just a placeholder for the earliest possible countdown attempt.” In an article in Spaceflightnow.com, Musk said the launch likely won’t occur until April at the earliest.
SpaceX said that Falcon 9 is now undergoing a checkout of the critical flight connections including fuel, liquid oxygen, and gas pressure systems. Once all system interfaces are verified, the launch team will execute a full tanking test of both first and second stages (wet dress) followed by a brief ~3.5 static fire of the first stage. “SpaceX has not set specific dates for wet dress or static fire as schedule will be driven by the satisfactory completion of all test objectives and a thorough review of the data,” the company said in a press release.
Here’s a look at the launch complex 40. Launch comples 40. Credit: SpaceX
ISS astronaut Soichi Noguchi has been sharing lots of amazing pictures he’s taken in space via Twitter, but this one is extra special. Noguchi was able to capture the plasma trail produced by space shuttle Endeavour as it streaked through Earth’s atmosphere. “Space Shuttle Endeavour making S-turn during atmospheric re-entry,” Noguchi wrote on his Twitpic page, where he post his space photos from Twitter, @Astro_Soichi. “The first time it was photographed from Space Station Cupola. Priceless.”
Just think of the precision it took to be able to take this image. Noguchi and the space station were flying about 354 km (220 miles) above Earth, going about 28,163 kph (17,500 mph), and the shuttle was likely flying just under Mach 25 — the speed it is going as it enters Earth’s atmosphere. Priceless indeed!
To start your working week, here’s a little something to help you sharpen your brain (OK, it’s already the end of the day for our viewers in New Zealand and Australia, so for you a little pick-me-up after a hard day’s work).
As with last week’s Universe Puzzle, something that cannot be answered by five minutes spent googling, a puzzle that requires you to cudgel your brains a bit, and do some lateral thinking. And a reminder: this is a puzzle on a “Universal” topic – astronomy and astronomers; space, satellites, missions, and astronauts; planets, moons, telescopes, and so on.
There are no prizes for the first correct answer – there may not even be just one correct answer! – posted as a comment (the judge’s decision – mine! – will be final!), but I do hope that you’ll have lots of fun.
What’s the next number in the sequence? 1655, 1671, 1672
Post your guesses in the comments section, and check back on Wednesday at this same post to find the answer. To make this puzzle fun for everyone, please don’t include links or extensive explanations with your answer, until after the answer has been given. Good luck!
PS There’s an open question on last week’s puzzle too (scroll down to the bottom of the comments).
UPDATE: Answer has been posted below.
Was this too easy perhaps? Maybe only five minutes’ spent googling was all that was needed to find the answer?
Christiaan Huygens discovered the first known moon of Saturn. The year was 1655 and the moon is Titan.
Giovanni Domenico Cassini made the next four discoveries: Iapetus (in 1671), Rhea (in 1672), …
… and Dione (in 1684), and Tethys (also in 1684).
What about Cassini’s discovery of the Cassini Division, in 1675?
Well, the discovery in 1655 was not made by Cassini, the rings of Saturn were discovered by Galileo (in 1610), and so on.
So, no, 1675 is not the next number in the sequence.
It’s amazing to reflect on how much more rapid astronomical discovery is, today, than back then; 45 years from the discovery of Saturn’s rings to Titan, another 20 to the discovery of the Cassini Division; 16 years between the discovery of Titan and Iapetus; … and 74 years from the rings to Dione and Tethys.
And today? Two examples: 45 years ago, x-ray astronomy was barely a toddler; and 74 years ago radio astronomy had just begun. Virtually all branches of astronomy outside the visual waveband went from scratch to today’s stunning results in less time than elapsed between the discovery of Saturn’s rings and its fourth brightest moon!
Endeavour lands at Kennedy Space Center. Image Credit: Alan Walters
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Space shuttle Endeavour loudly announced its arrival with twin sonic booms, then two minutes later emerged like a phantom out of the darkness to touch down beautifully on runway 15 at Kennedy Space Center. The landing at 10:20 p.m. EST Sunday ended the two-week STS-130 mission to the ISS. After early concerns about the weather, conditions were almost ideal for landing.
“STS-130 is mission complete, and we’re safe on deck” said Commander George Zamka, speaking on the runway after the crew disembarked from Endeavour. “The Cupola is beautiful in both design and function, and Endeavour was perfect throughout the flight… Now it’s time for us to hit the showers and get used to life on Earth again.”
“It was really exciting to land on the first opportunity,” said astronaut Bob Behnken, “and we’re happy to put this capstone on such a great mission.”
Part of the convoy of vehicles heading out to service Endeavour after landing. Credit: Alan Walters
The STS-130 crew delivered the “room with a view” to the ISS – the Node 3, or Tranquility module with the attached Cupola that will provide astronauts with 360 degree views of Earth, space and robotic operations outside the space station.
At the post-landing press conference, mission managers echoed the astronauts’ sentiments.
“It was a fantastic landing day, and Endeavour’s landing here tonight at KSC capped off a perfect mission on orbit,” said Mike Moses launch integration manager for the space shuttle program. “The vehicle performed absolutely flawlessly, the crew did outstanding job,… the installation of Node 3 and Cupola all went perfectly. This just illustrates the great job the all the teams did. Just a spectacular mission.”
Space shuttle launch director Mike Leinbach also looked to what is ahead for the space shuttle program.
“One of the most magical things we get to do here is to walk around the space shuttle on the runway after a mission,” he said. “The shuttle looks outstanding out there, and we’re going to start the final processing flow of Endeavour tonight. So that will be a milestone for the space shuttle program, and we will go into that with our heads held high and we’re going to process the vehicle as we always do and be ready to fly her last mission. A little bit of a sad note, but a great ending to a great mission and we’re looking forward to the next one.”
With this mission the ISS is now 98% mass complete.
Next up for the shuttle and ISS programs is Discovery’s STS-131 mission, currently slated to launch on April 5, 2010.
While this marks the end of this mission — which Ken Kremer and I have been reporting on live from KSC — I will still be hanging around the Space Coast for a few more weeks, so look for more news (and launches!) coming up. And we hope to have photographer Alan Walters on location at KSC for Universe Today covering the final flights of the space shuttle program.
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This image is a software-calibrated image with high signal-to-noise ratio at a frequency of 120 MHz, of the radio sky above Effelsberg, Germany, on November10, 2009. It has North at the top and East at the left, just as a person would have seen the entire sky when lying on their back on a flat field near Effelsberg late in the afternoon on November 10, if their eyes were sensitive to radio waves.
The two bright (yellow) spots are Cygnus A – a giant radio galaxy powered by a supermassive black hole – near the center of the image, and Cassiopeia A – a bright radio source created by a supernova explosion about 300 years ago – at the upper-left in the image. The plane of our Milky Way galaxy can also be seen passing by both Cassiopeia A and Cygnus A, and extending down to the bottom of the image. The North Polar Spur, a large cloud of radio emission within our own galaxy, can also be seen extending from the direction of the Galactic center in the South, toward the western horizon in this image. “We made this image with a single 60 second “exposure” at 120 MHz using our high-band LOFAR field in Effelsberg”, says James Anderson, project manager of the Effelsberg LOFAR station.
“The ability to make all-sky images in just seconds is a tremendous advancement compared to existing radio telescopes which often require weeks or months to scan the entire sky,” Anderson went on. This opens up exciting possibilities to detect and study rapid transient phenomena in the universe.
LOFAR, the LOw Frequency ARray, was designed and developed by ASTRON (Netherlands Institute for Radio Astronomy) with 36 stations centered on Exloo in the northeast of The Netherlands. It is now an international project with stations being built in Germany, France, the UK and Sweden connected to the central data processing facilities in Groningen (NL) and the ASTRON operations center in Dwingeloo (NL). The first international LOFAR station (IS-DE1) was completed on the area of the Effelsberg radio observatory next to the 100-m radio telescope of the Max-Planck-Institut für Radioastronomie (MPIfR).
Operating at relatively low radio frequencies from 10 to 240 MHz, LOFAR has essentially no moving parts to track objects in the sky; instead digital electronics are used to combine signals from many small antennas to electronically steer observations on the sky. In certain electronic modes, the signals from all of the individual antennas can be combined to make images of the entire radio sky visible above the horizon. IS-DE1: Some of the 96 low-band dipole antennas, Effelsberg LOFAR station (foreground); high-band array (background) (Credit: James Anderson, MPIfR)
LOFAR uses two different antenna designs, to observe in two different radio bands, the so-called low-band from 10 to 80 MHz, and the high-band from 110 to 240 MHz. All-sky images using the low-band antennas at Effelsberg were made in 2007.
Following the observation for the first high-band, all-sky image, scientists at MPIfR made a series of all-sky images covering a wide frequency range using both the low-band and high-band antennas at Effelsberg. Effelsberg sky through LOFAR eyes (Credit: James Anderson, MPIfR)
The movie of these all-sky images has been compiled and is shown above. The movie starts at a frequency of 35 MHz, and each subsequent frame is about 4 MHz higher in frequency, through 190 MHz. The resolution of the Effelsberg LOFAR telescope changes with frequency. At 35 MHz the resolution is about 10 degrees, at 110 MHz it is about 3.4 degrees, and at 190 MHz it is about 1.9 degrees. This change in resolution can be seen by the apparent size of the two bright sources Cygnus A and Cassiopeia A as the frequency changes.
Scientists at MPIfR and other institutions around Europe will use measurements such as these to study the large-sky structure of the interstellar matter of our Milky Way galaxy. The low frequencies observed by LOFAR are ideal for studying the low energy cosmic ray electrons in the Milky Way, which trace out magnetic field structures through synchrotron emission. Other large-scale features such as supernova remnants, star-formation regions, and even some other nearby galaxies will need similar measurements from individual LOFAR telescopes to provide accurate information on the large-scale emission in these objects. “We plan to search for radio transients using the all-sky imaging capabilities of the LOFAR telescopes”, says Michael Kramer, director at MPIfR, in Bonn. “The detection of rapidly variable sources using LOFAR could lead to exciting discoveries of new types of astronomical objects, similar to the discoveries of pulsars and gamma-ray bursts in the past decades.”
“The low-frequency sky is now truly open in Effelsberg and we have the capability at the observatory to observe in a wide frequency range from 10 MHz to 100 GHz”, says Anton Zensus, also director at MPIfR. “Thus we can cover four orders of magnitude in the electromagnetic spectrum.”
ISS as seen by the departing Endeavour crew on STS-130. Credit: NASA
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The main computer on the International Space Station failed early Sunday, and subsequent multiple computer anomalies prompted communication blackouts. The one main computer has two backup systems, and NASA reported that the three command & control computers are switching between prime, backup and standby. A software issue is suspected, and diagnosis continues. The computer system is critical to all aspects of space station operation.
NASA reported that despite the computer issues, all ISS systems are performing normally and there are no concerns for the safety of the crew.
Bill Harwood at CBS News reported that the station’s command and control software was updated before the shuttle Endeavour’s flight to account for the new Tranquility module and it’s possible the computer failures, or transitions, are software related. Issues with computers in Tranquility also have been noted, but it’s not yet clear whether they are related to the command and control issues.
ISS Commander Jeff Williams called Mission Control at 9:55 a.m. EST “and confirmed there had been a primary and backup failure of the command and control computer,” said NASA TV commentator Pat Ryan. At that time, all indications were that two of the three computers were healthy. But then later, about 11 a.m. EST, there new data indicated there had been another computer transition, this time still with just two computers healthy.
Another transition occurred an hour later.
“But we are still in a situation currently where all three computers are healthy but the team here in mission control is still scratching its head and trying to determine what’s been causing the repeated transitions,” Ryan said. “There has been no impact to station life support systems while this was going on and the crew is in good shape.”
“We’re thinking we might need another day off,” said Williams, apparently in good spirits.
“Copy and concur, Jeff,” replied Stan Love in Houston. “We are talking in the room, we still do not know what has been causing these transitions. We are toying with the idea there might be something related to commanding. But we are not sure, it’s just speculation at this point.”
X-ray emission in the COSMOS field (XMM-Newton/ESA)
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Galaxy density in the Cosmic Evolution Survey (COSMOS) field, with colors representing the redshift of the galaxies, ranging from redshift of 0.2 (blue) to 1 (red). Pink x-ray contours show the extended x-ray emission as observed by XMM-Newton.
Dark matter (actually cold, dark – non-baryonic – matter) can be detected only by its gravitational influence. In clusters and groups of galaxies, that influence shows up as weak gravitational lensing, which is difficult to nail down. One way to much more accurately estimate the degree of gravitational lensing – and so the distribution of dark matter – is to use the x-ray emission from the hot intra-cluster plasma to locate the center of mass.
And that’s just what a team of astronomers have recently done … and they have, for the first time, given us a handle on how dark matter has evolved over the last many billion years.
COSMOS is an astronomical survey designed to probe the formation and evolution of galaxies as a function of cosmic time (redshift) and large scale structure environment. The survey covers a 2 square degree equatorial field with imaging by most of the major space-based telescopes (including Hubble and XMM-Newton) and a number of ground-based telescopes.
Understanding the nature of dark matter is one of the key open questions in modern cosmology. In one of the approaches used to address this question astronomers use the relationship between mass and luminosity that has been found for clusters of galaxies which links their x-ray emissions, an indication of the mass of the ordinary (“baryonic”) matter alone (of course, baryonic matter includes electrons, which are leptons!), and their total masses (baryonic plus dark matter) as determined by gravitational lensing.
To date the relationship has only been established for nearby clusters. New work by an international collaboration, including the Max Planck Institute for Extraterrestrial Physics (MPE), the Laboratory of Astrophysics of Marseilles (LAM), and Lawrence Berkeley National Laboratory (Berkeley Lab), has made major progress in extending the relationship to more distant and smaller structures than was previously possible.
To establish the link between x-ray emission and underlying dark matter, the team used one of the largest samples of x-ray-selected groups and clusters of galaxies, produced by the ESA’s x-ray observatory, XMM-Newton.
Groups and clusters of galaxies can be effectively found using their extended x-ray emission on sub-arcminute scales. As a result of its large effective area, XMM-Newton is the only x-ray telescope that can detect the faint level of emission from distant groups and clusters of galaxies.
“The ability of XMM-Newton to provide large catalogues of galaxy groups in deep fields is astonishing,” said Alexis Finoguenov of the MPE and the University of Maryland, a co-author of the recent Astrophysical Journal (ApJ) paper which reported the team’s results.
Since x-rays are the best way to find and characterize clusters, most follow-up studies have until now been limited to relatively nearby groups and clusters of galaxies.
“Given the unprecedented catalogues provided by XMM-Newton, we have been able to extend measurements of mass to much smaller structures, which existed much earlier in the history of the Universe,” says Alexie Leauthaud of Berkeley Lab’s Physics Division, the first author of the ApJ study. COSMOS-XCL095951+014049 (Subaru/NAOJ, XMM-Newton/ESA)
Gravitational lensing occurs because mass curves the space around it, bending the path of light: the more mass (and the closer it is to the center of mass), the more space bends, and the more the image of a distant object is displaced and distorted. Thus measuring distortion, or ‘shear’, is key to measuring the mass of the lensing object.
In the case of weak gravitational lensing (as used in this study) the shear is too subtle to be seen directly, but faint additional distortions in a collection of distant galaxies can be calculated statistically, and the average shear due to the lensing of some massive object in front of them can be computed. However, in order to calculate the lens’ mass from average shear, one needs to know its center.
“The problem with high-redshift clusters is that it is difficult to determine exactly which galaxy lies at the centre of the cluster,” says Leauthaud. “That’s where x-rays help. The x-ray luminosity from a galaxy cluster can be used to find its centre very accurately.”
Knowing the centers of mass from the analysis of x-ray emission, Leauthaud and colleagues could then use weak lensing to estimate the total mass of the distant groups and clusters with greater accuracy than ever before.
The final step was to determine the x-ray luminosity of each galaxy cluster and plot it against the mass determined from the weak lensing, with the resulting mass-luminosity relation for the new collection of groups and clusters extending previous studies to lower masses and higher redshifts. Within calculable uncertainty, the relation follows the same straight slope from nearby galaxy clusters to distant ones; a simple consistent scaling factor relates the total mass (baryonic plus dark) of a group or cluster to its x-ray brightness, the latter measuring the baryonic mass alone.
“By confirming the mass-luminosity relation and extending it to high redshifts, we have taken a small step in the right direction toward using weak lensing as a powerful tool to measure the evolution of structure,” says Jean-Paul Kneib a co-author of the ApJ paper from LAM and France’s National Center for Scientific Research (CNRS).
The origin of galaxies can be traced back to slight differences in the density of the hot, early Universe; traces of these differences can still be seen as minute temperature differences in the cosmic microwave background (CMB) – hot and cold spots.
“The variations we observe in the ancient microwave sky represent the imprints that developed over time into the cosmic dark-matter scaffolding for the galaxies we see today,” says George Smoot, director of the Berkeley Center for Cosmological Physics (BCCP), a professor of physics at the University of California at Berkeley, and a member of Berkeley Lab’s Physics Division. Smoot shared the 2006 Nobel Prize in Physics for measuring anisotropies in the CMB and is one of the authors of the ApJ paper. “It is very exciting that we can actually measure with gravitational lensing how the dark matter has collapsed and evolved since the beginning.”
One goal in studying the evolution of structure is to understand dark matter itself, and how it interacts with the ordinary matter we can see. Another goal is to learn more about dark energy, the mysterious phenomenon that is pushing matter apart and causing the Universe to expand at an accelerating rate. Many questions remain unanswered: Is dark energy constant, or is it dynamic? Or is it merely an illusion caused by a limitation in Einstein’s General Theory of Relativity?
The tools provided by the extended mass-luminosity relationship will do much to answer these questions about the opposing roles of gravity and dark energy in shaping the Universe, now and in the future.
Sources: ESA, and a paper published in the 20 January, 2010 issue of the Astrophysical Journal (arXiv:0910.5219 is the preprint)
NASA astronaut George Zamka, STS-130 commander, is pictured in a window of the newly-installed Cupola of the International Space Station while space shuttle Endeavour remains docked with the station.
[/caption](Editor’s Note: Ken Kremer is at the Kennedy Space Center for Universe Today covering the flight of Endeavour)
The first landing attempt is set for 10:20 PM EST on Orbit 217 with the de-orbit burn planned for 9:14 PM. See landing track below. A second opportunity is available at 11:55 PM. There are two additional opportunities available overnight at Edwards Air Force Base, Calif., at 1:25 AM EST Monday and 3:00 AM. The Spaceflight Meteorology Group and local news forecasts here in Florida predict deteriorating weather at KSC on Monday with increasing chances of rain.
The crew will berth the robotic arm and conduct the standard pre-landing check out of re-entry systems for the flight control surfaces. They will test the hydraulic power units and elevons and test fire all the steering jets during their last planned full day in space.
Landing ground track for 1st landing opportunity at 10:20 PM on Sunday, Feb. 21 at KSC. Credit: NASA
Eight Xenon lights will illuminate the SLF for the night time shuttle landing. Four xenons will be positioned at both ends of the runway to illuminate the touchdown and rollout area from behind the shuttle. Each Xenon light emits 1 billion candlepower, or 20 kilowatts.
Endeavour undocked from the ISS on Friday (Feb 19) at 7:54 PM EST while orbiting 208 miles high above the Atlantic Ocean after a completely successful period of joint operations with the Expedition 22 crew totaling nine days, 19 hours and 48 minutes. Shuttle pilot Terry Virts performed a fly-around of the station, enabling his crewmates to conduct a photo survey of the complex. The crew also conducted the now standard final check for any signs of damage to the heat shield tiles on Endeavour’s belly and the reinforced carbon carbon (RCC) panels on the wing leading edges and nose cap using the Orbiter Boom Sensor System attached to the shuttles robotic arm in order to ensure a safe reentry.
During the two week flight, the STS 130 crew brought aloft and installed the Tranquility habitation module and the Cupola observation dome and conducted three spacewalks. Tranquility houses critical life support systems. The Cupola possesses 7 spectacular windows affording dazzling vistas of the earth below and the cosmos above.
The station is now 98 percent complete by volume and 90 percent complete by mass. The station itself exceeds 800,000 pounds and the combined weight with the shuttle exceeds 1 million pounds for the first time.
Earlier STS 130/ISS and SDO articles by Ken Kremer
