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What recent developments are happening in Low Earth Orbit?
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Russian BLITS satellite blitzed by Chinese space debris
Russia’s really getting beat up on lately. First the fireball and now one of its satellites gets whacked by a piece of Chinese space junk. In 2007 China performed an anti-satellite weapons test destroying its Fengyun 1C weather satellite leaving in its place thousands of fragments of Earth-orbiting shrapnel.
NASA estimates the test created some 950 objects 4 inches (10 cm) or larger in a debris cloud extending from 125 to nearly 2,300 miles (200-3,850 km) high covering all of low-Earth orbit where a great many satellites – including the space station – circle the planet. At the 1/2-inch level, the garbage totals up to more than 35,000 bits and bolts.
This miasmic cloud of human hubris represents the single greatest danger to orbiting satellites since the beginning of the space age. Much of it is hundreds of miles high and will take many years to “decay” or re-enter Earth’s atmosphere.
The Russian Ball Lens in The Space (BLITS) nanosatellite, a small 16-lb. satellite used for laser-ranging studies, had been functioning properly when on January 22, 2013 it was hit by Chinese satellite debris according to an analysis by the Colorado-based Center for Space Standards and Innovation. Scientists noticed a sudden change in its orbit, spin period (amount of time it take to turn around its axis) and orientation in space. By Feb. 28 they knew the culprit: a chunk of Fengyun 1C debris.
Satellites need to rotate at a precise rate and orientation to maintain contact with Earth as well as serve as useful platforms for experiments. BLITS, now shattered into at least two pieces, tumbles about like a leaf. The satellite was equipped with mirrors called retroreflectors that reflected back brief pulses of laser light shot from an Earth station. By precisely measuring the time for light takes to make the two-way trip, scientists can determine the satellite’s distance to millimeter accuracy.
With that data, they’re able to measure Earth’s gravity field and seasonal height variations of the atmosphere, map the surface of the oceans and even tap into the structure of Earth’s interior.
Pity it was likely destroyed. We can only hope this serves as a lesson to other nations who might contemplate similar anti-satellite tests. Littering is bad whether on Earth or in orbit. Read more about the collision HERE.
A meteor streaked across the sky and exploded over Russia’s Ural Mountains with the power of an atomic bomb
February 15, 2013
A meteor streaked across the sky and exploded over Russia’s Ural Mountains with the power of an atomic bomb Friday, its sonic blasts shattering countless windows and injuring about 1,100 people.
The spectacle deeply frightened many Russians, with some elderly women declaring that the world was coming to an end. Many of the injured were cut by flying glass as they flocked to windows, curious about what had produced such a blinding flash of light.
The meteor — estimated to be about 10 tons and 49 feet wide — entered the Earth’s atmosphere at a hypersonic speed of at least 33,000 mph and shattered into pieces about 18-32 miles above the ground, the Russian Academy of Sciences said in a statement. But even small asteroids pack a tremendous punch, explained Andrew Cheng of the Johns Hopkins Applied Physics Laboratory.
“It doesn’t take a very large object. A 10-meter size object already packs the same energy as a nuclear bomb,” Cheng, who led a 2000-2001 mission for NASA to orbit and land on an asteroid, told FoxNews.com.
Read more from FoxNews!
This Is Our Planet – NASA Timelapse Video
July 7, 2012
The Sun in Planetary Proportions
January 26, 2012
Early this week, the most intense solar flare in seven years sent a flurry of particles toward the Earth. In light of that event, we decided to release our February cover story a bit ahead of time. The article discusses the vulnerability of electrical grids and telecommunications networks to the fluctuations in the Earth’s magnetic field caused by such solar tempests. Researchers fear that an upswing in solar storm activity—as is predicted for later this year—has the potential to cause a global blackout. In a video interview, John Kappenman, the feature’s author, puts the magnitude of this week’s solar storm in perspective.
Comet Lovejoy Survives Fiery Plunge Through Sun, NASA Says
December 16, 2011
A newfound comet defied long odds on Thursday (Dec. 15), surviving a suicidal dive through the sun’s hellishly hot atmosphere, according to NASA scientists.
Comet Lovejoy plunged through the sun’s corona at about 7 p.m. EST (midnight GMT on Dec. 16), coming within 87,000 miles (140,000 kilometers) of our star’s surface. Temperatures in the corona can reach 2 million degrees Fahrenheit (1.1 million degrees Celsius), so most researchers expected the icy wanderer to be completely destroyed.
But Lovejoy proved to be made of tough stuff. A video taken by NASA’s Solar Dynamics Observatory (SDO) spacecraft showed the icy object emerging from behind the sun and zipping back off into space.
“Breaking News! Lovejoy lives! The comet Lovejoy has survived its journey around the sun to reemerge on the other side,” SDO researchers tweeted.
SDO is one of many instruments that scientists — eager to record and study the comet’s presumed demise — trained on Lovejoy as it streaked toward the sun.
“We have here an exceptionally rare opportunity to observe the complete vaporization of a relatively large comet, and we have approximately 18 instruments on five different satellites that are trying to do just that,” Karl Battams, a scientist at the Naval Research Laboratory in Washington, D.C., wrote on the Sungrazing Comets website, before Lovejoy’s closest solar approach.
Battams runs the website, which is devoted to comets discovered by two different spacecraft: NASA’s Solar Terrestrial Relations Observatory (STEREO) and the Solar and Heliospheric Observatory (SOHO), which is operated jointly by NASA and the European Space Agency (ESA).
Battams greeted news of Lovejoy’s improbable escape with surprise and delight. [Photos of Death-Defying Comet Lovejoy]
“I expected a diffuse dust tail to survive (for several hours) before fading away but NOT any kind of nucleus!” he tweeted. “I’ve worked with sungrazers for 8yrs; today was the most amazing day I’ve ever had with them!”
Preparing for the end
Lovejoy has a core about 660 feet (200 meters) wide. It belongs to a class of comets known as Kreutz sungrazers, whose orbits bring them very close to the sun.
All Kreutz sungrazers are thought to be the remnants of a single giant comet that broke apart several centuries ago. They’re named after the 19th-century German astronomer Heinrich Kreutz, who first showed that such comets are related.
Comets plunge into the sun on a regular basis, but they rarely give much advance notice of their suicidal intentions. That’s why scientists were so excited about Lovejoy. Australian amateur astronomer Terry Lovejoy discovered the icy wanderer on Nov. 27, giving researchers plenty of time to map out their observation campaign.
And that campaign has been intense, involving five different spacecraft. In addition to SDO, SOHO and STEREO, scientists planned to use Japan’s Hinode satellite and ESA’s Proba spacecraft to track Lovejoy’s movements, Battams wrote.
NASA also created a website providing updates about the comet’s pass through the corona, as well as images of the event beamed down by SDO. It can be found here: http://sdo.gsfc.nasa.gov/data/lovejoy.php
For his part, Terry Lovejoy said he was happy to have made a contribution, and he marveled a bit at all the attention the comet has been getting.
“It’s been tremendous,” Lovejoy told SPACE.com. “Apparently it’s all over Facebook, and I don’t use Facebook. But there’s a lot of interest. I think a lot of people like the name — the Lovejoy name seems to strike a chord with people.”
A dramatic escape
Lovejoy is quite large for a sungrazing comet, and experts expected it to die an impressive death. The website Spaceweather.com, for example, predicted Lovejoy would blaze as brightly as Jupiter or Venus in the sky as it neared the sun.
Battams also expected a good show, saying the comet might even be visible from the ground around sunset today in the Northern Hemisphere.
“I do think that it will put on a spectacular show for us and will be the brightest Kreutz-group comet that SOHO has ever observed,” Battams wrote last week.
Though the early returns are still coming in, those forecasts appear to be on the money. Observations from various spacecraft do indeed show Lovejoy flaring up significantly as it neared our star.
Researchers will keep analyzing the images to better understand the comet’s daring solar approach. And now skywatchers apparently have another shot to catch a glimpse of the resilient Lovejoy on Friday morning (Dec. 16).
For observers in North America, the comet will rise approximately 5 to 10 minutes before dawn and will be situated to the upper right of the sun. If Lovejoy is still shining at least as brightly as Venus, it may be visible, experts say.
You could also try to spot Lovejoy after the sun comes up, if you’re exceedingly careful. Block the rising sun behind a distant building and focus on the part of the sky 3 to 4 degrees above and to the right of the sun (your clenched fist held at arm’s length is equal to roughly 10 degrees). CAUTION: Never point binoculars or a telescope at or near the sun, and never look directly at our star with the naked eye. Serious eye damage can result.
And don’t get your hopes up, either. The comet may well be too faint to see, experts say.
Paul Allen Unveils Proposal for New Space Launch System
December 13, 2011
Scientists find Monster Black Holes, biggest yet
December 6, 2011
Scientists have found the biggest black holes known to exist — each one 10 billion times the mass of our sun. A team led by astronomers at the University of California, Berkeley, discovered the two gigantic black holes in clusters of elliptical galaxies more than 300 million light years away. That’s relatively close on the galactic scale.”They are monstrous,” Berkeley astrophysicist Chung-Pei Ma told reporters. “We did not expect to find such massive black holes because they are more massive than indicated by their galaxy properties. They’re kind of extraordinary.”The previous black hole record-holder is as large as 6 billion suns.
In research released Monday by the journal Nature, the scientists suggest these black holes may be the leftovers of quasars that crammed the early universe. They are similar in mass to young quasars, they said, and have been well hidden until now.The scientists used ground-based telescopes as well as the Hubble Space Telescope and Texas supercomputers, observing stars near the black holes and measuring the stellar velocities to uncover these vast, invisible regions.
Black holes are objects so dense that nothing, not even light, can escape. Some are formed by the collapse of a super-size star. It’s uncertain how these two newly discovered whoppers originated, said Nicholas McConnell, a Berkeley graduate student who is the study’s lead author.
To be so massive now means they must have grown considerably since their formation, he said.Most if not all galaxies are believed to have black holes at their center. The bigger the galaxy, it seems, the bigger the black hole.Quasars are some of the most energized and distant of galactic centers. The researchers said their findings suggest differences in the way black holes grow, depending on the size of the galaxy.Ma speculates these two black holes remained hidden for so long because they are living in quiet retirement — much quieter and more boring than their boisterous youth powering quasars billions of years ago.”For an astronomer, finding these insatiable black holes is like finally encountering people nine feet tall whose great height had only been inferred from fossilized bones. How did they grow so large?”
Ma said in a news release. “This rare find will help us understand whether these black holes had very tall parents or ate a lot of spinach.”Oxford University astrophysicist Michele Cappellari, who wrote an accompanying commentary in the journal, agreed that the two newly discovered black holes “probably represent the missing dormant relics of the giant black holes that powered the brightest quasars in the early universe.”One of the newly detected black holes weighs 9.7 billion times the mass of the sun. The second, slightly farther from Earth, is as big or even bigger.Even larger black holes may be lurking out there. Ma said that’s the million-dollar question: How big can a black hole grow?The researchers already are peering into the biggest galaxies for answers.”If there is any bigger black hole,” Ma said, “we should be able to find them in the next year or two. Personally, I think we are probably reaching the high end now. Maybe another factor of two to go at best.”
NASA Telescope Confirms Alien Planet in Habitable Zone
December 5, 2011
NASA’s planet-hunting Kepler spacecraft has confirmed the discovery of its first alien world in its host star’s habitable zone — that just-right range of distances that could allow liquid water to exist — and found more than 1,000 new explanet candidates, researchers announced today (Dec. 5). The new finds bring the Kepler space telescope’s total haul to 2,326 potential planets in its first 16 months of operation.These discoveries, if confirmed, would quadruple the current tally of worlds known to exist beyond our solar system, which recently topped 700.
The potentially habitable alien world, a first for Kepler, orbits a star very much like our own sun. The discovery brings scientists one step closer to finding a planet like our own — one which could conceivably harbor life, scientists said.
“We’re getting closer and closer to discovering the so-called ‘Goldilocks planet,'” Pete Worden, director of NASA’s Ames Research Center in Moffett Field, Calif., said during a press conference today. The newfound planet in the habitable zone is called Kepler-22b. It is located about 600 light-years away, orbiting a sun-like star.
Kepler-22b’s radius is 2.4 times that of Earth, and the two planets have roughly similar temperatures. If the greenhouse effect operates there similarly to how it does on Earth, the average surface temperature on Kepler-22b would be 72 degrees Fahrenheit (22 degrees Celsius). The $600 million Kepler observatory launched in March 2009 to hunt for Earth-size alien planets in the habitable zone of their parent stars, where liquid water, and perhaps even life, might be able to exist.
Kepler detects alien planets using what’s called the “transit method.” It searches for tiny, telltale dips in a star’s brightness caused when a planet transits — or crosses in front of — the star from Earth’s perspective, blocking a fraction of the star’s light. The finds graduate from “candidates” to full-fledged planets after follow-up observations confirm that they’re not false alarms. This process, which is usually done with large, ground-based telescopes, can take about a year. The Kepler team released data from its first 13 months of operation back in February, announcing that the instrument had detected 1,235 planet candidates, including 54 in the habitable zone and 68 that are roughly Earth-size. Of the total 2,326 candidate planets that Kepler has found to date, 207 are approximately Earth-size. More of them, 680, are a bit larger than our planet, falling into the “super-Earth” category. The total number of candidate planets in the habitable zones of their stars is now 48.
To date, just over two dozen of these potential exoplanets have been confirmed, but Kepler scientists have estimated that at least 80 percent of the instrument’s discoveries should end up being the real deal. The newfound 1,094 planet candidates are the fruit of Kepler’s labors during its first 16 months of science work, from May 2009 to September 2010. And they won’t be the last of the prolific instrument’s discoveries.
“This is a major milestone on the road to finding Earth’s twin,” Douglas Hudgins, Kepler program scientist at NASA headquarters in Washington, D.C., said in a statement.
Mission scientists still need to analyze data from the last two years and on into the future. Kepler will be making observations for a while yet to come; its nominal mission is set to end in November 2012, but the Kepler team is preparing a proposal to extend the instrument’s operations for another year or more. Kepler’s finds should only get more exciting as time goes on, researchers say.
“We’re pushing down to smaller planets and longer orbital periods,” said Natalie Batalha, Kepler deputy science team lead at Ames.
To flag a potential planet, the instrument generally needs to witness three transits. Planets that make three transits in just a few months must be pretty close to their parent stars; as a result, many of the alien worlds Kepler spotted early on have been blisteringly hot places that aren’t great candidates for harboring life as we know it.
Given more time, however, a wealth of more distantly orbiting — and perhaps more Earth-like — exoplanets should open up to Kepler. If intelligent aliens were studying our solar system with their own version of Kepler, after all, it would take them three years to detect our home planet.
“We are getting very close,” Batalha said. “We are homing in on the truly Earth-size, habitable planets.”
Defunct 6-ton Satellite falls to Earth
September 24, 2011
WASHINGTON— NASA’s dead 6-ton satellite fell to Earth early Saturday morning, starting its fiery death plunge somewhere over the vast Pacific Ocean.
Details were still sketchy, but the U.S. Air Force’s Joint Space Operations Center and NASA say that the bus-sized satellite first penetrated Earth’s atmosphere somewhere over the Pacific Ocean. That doesn’t necessarily mean it all fell into the sea. NASA’s calculations had predicted that the former climate research satellite would fall over a 500-mile swath.
The two government agencies say the 35-foot satellite fell sometime between 11:23 p.m. EDT and 1:09 a.m. EDT. NASA said it didn’t know the precise time or location yet.
Some 26 pieces of the satellite — representing 1,200 pounds of heavy metal — were expected to rain down somewhere. The biggest surviving chunk should be no more than 300 pounds.
The Upper Atmosphere Research Satellite is the biggest NASA spacecraft to crash back to Earth, uncontrolled, since the post-Apollo 75-ton Skylab space station and the more than 10-ton Pegasus 2 satellite, both in 1979.
Russia’s 135-ton Mir space station slammed through the atmosphere in 2001, but it was a controlled dive into the Pacific.
Before UARS fell, no one had ever been hit by falling space junk and NASA expected that not to change. NASA put the chances that somebody somewhere on Earth would get hurt at 1-in-3,200. But any one person’s odds of being struck were estimated at 1-in-22 trillion, given there are 7 billion people on the planet.
Huge Defunct Satellite Falling to Earth Faster than Expected, NASA Says
Source: Space.com, September 16, 2011
NASA space junk experts have refined the forecast for the anticipated death plunge of a giant satellite, with the U.S. space agency now predicting the 6 1/2-ton climate probe will plummet to Earth around Sept. 23, a day earlier than previously reported.
The defunct bus-size spacecraft is NASA’s Upper Atmospheric Research Satellite (UARS), which launched in 1991 and was shut down in 2005 after completing its mission. The satellite was expected to fall to Earth sometime this year, with experts initially pegging a weeks-long window between late September and early October, then narrowing it to the last week of this month.
That window, NASA now says, has been trimmed to just three days.
“Re-entry is expected Sept. 23, plus or minus a day. The re-entry of UARS is advancing because of a sharp increase in solar activity since the beginning of this week,” NASA officials wrote in a status update today (Sept. 16). The projection is a day earlier than a previous forecast released by NASA yesterday.
NASA spokeswoman Beth Dickey confirmed with SPACE.com earlier today that the reason UARS is expected to fall early in its re-entry window is because of the sharp uptick in solar activity. Solar effects from the sun can create an extra drag on satellites in space because they can heat the Earth’s atmosphere, causing it to expand, agency officials have said.
Where will UARS fall?
But exactly where the UARS spacecraft will fall is still unknown.
NASA expects at least 26 large pieces of the massive satellite to survive the scorching temperatures of re-entry and reach Earth’s surface. Titanium pieces and onboard tanks could be among that debris, but the UARS satellite carries no toxic propellant (NASA used up all the fuel in 2005).
The debris is expected to fall over a swath of Earth about 500 miles (804 kilometers) long, NASA officials said. [Video: Where Could UARS Satellite Debris Fall?]
There is a 1-in-3,200 chance of satellite debris hitting a person on the ground, odds that NASA says are extremely remote. Outside experts agree.
“Look at how much of Earth is covered with water,” Victoria Samson, the Washington Office Director of the Secure World Foundation, an organization dedicated to the peaceful use of outer space, told SPACE.com this week. “There’s a really good chance it’s going to go straight into the ocean.”
Constant satellite watch
NASA officials expect the UARS satellite to fall over a region somewhere between the latitudes of northern Canada and southern South America, which leaves a vast swath of the world open as a possible re-entry point. About 75 percent of the Earth’s surface is covered in water, which makes an ocean splashdown likely, NASA and experts have said.
NASA and the Joint Space Operations Center of U.S. Strategic Command at Vandenberg Air Force Base, Calif., are keeping a close watch on the falling satellite, but will only be able to pinpoint its actual crash zone to within about 6,000 miles (10,000 km) about two hours before re-entry.
As of Thursday, the UARS satellite was flying in an orbit of between 143 and 158 miles (230 to 255 km) above Earth. That orbit is dropping lower each day, NASA officials said. [Infographic: NASA’s Falling UARS Satellite Explained]
NASA has advised the public not to touch any debris that may reach the surface, should it be discovered. Instead, the space agency says that anyone who finds satellite debris should contact their local law enforcement agency.
The $750 million UARS mission was designed to measure ozone and other chemical compounds found in Earth’s ozone layer in order to better understand how the upper atmosphere affects our planet. It also recorded wind speeds and temperatures in the stratosphere, as well as the energy Earth received from the sun.
Time to Think about Cleaning Up Space Junk, Study Says
Source: LA Times, September 2, 2011
WASHINGTON — Space junk has made such a mess of Earth’s orbit that experts say we may need to think seriously about cleaning it up.
That may mean vacuuming up debris with weird space technology — cosmic versions of nets, magnets and giant umbrellas, according to the chairman of an expert panel that issued a report on the problem Thursday.
There are 22,000 objects in orbit that are big enough for officials on the ground to track and countless more smaller ones that could do damage to human-carrying spaceships and valuable satellites. The International Space Station has to move out of the way of debris from time to time.
“We’ve lost control of the environment,” said retired NASA senior scientist Donald Kessler, who led the National Academy of Sciences report.
Since the space age began 54 years ago, civilization has littered the area just above Earth’s atmosphere with leftover boosters and other parts that come off during launches, as well as old satellites. When scientists noticed that this could be a problem, they came up with agreements to limit new space junk, and those plans had been working.
Those agreements are intended to make sure what is sent into orbit eventually falls back toward Earth and burns up.
But two events in the last four years — a 2007 Chinese anti-satellite weapon test and a 2009 crash in orbit of two satellites — put so much new junk in space that everything changed, the report said. The widely criticized Chinese test used a missile to smash an aging weather satellite into 150,000 pieces of debris larger than four-tenths of an inch, and 3,118 pieces can be tracked by radar on the ground, the report said.
“Those two single events doubled the amount of fragments in Earth orbit and completely wiped out what we had done in the last 25 years,” Kessler said.
The study only briefly mentions the cleanup possibility, raising technical, legal and diplomatic hurdles. But it refers to a report this year by a Defense Department science think tank that outlines other unusual techniques. The report by the Defense Advanced Research Projects Agency is called Catcher’s Mitt, and it mentions harpoons, nets, tethers, magnets and even a giant dish or umbrella-shaped device that would sweep up tiny pieces of debris.
Though the new report doesn’t recommend using the technology, Kessler said it was needed. NASA officials said they were examining the study.
Astronauts May Evacuate Space Station in November, NASA says
Source: Space.com, August 29, 2011
The International Space Station may have to start operating without a crew in November if Russian engineers don’t figure out soon what caused a recent rocket failure, NASA officials announced today (Aug. 29).
The unmanned Russian cargo ship Progress 44 crashed just after its Aug. 24 launch to deliver 2.9 tons of supplies to the orbiting lab. The failure was caused by a problem with the Progress’ Soyuz rocket, which is similar to the one Russia uses to launch its crew-carrying vehicle — also called Soyuz — to the station.
Currently, six astronauts reside on the space station. They shouldn’t be unduly affected by the Progress crash, NASA officials said, because they have enough supplies to last a while on orbit.
But three of these astronauts are due to return to Earth next month, and the rest are scheduled to come back in mid-November. At the moment, the Soyuz is the only way to get astronauts to and from the station. So if the rocket anomaly isn’t identified and fixed soon, a fresh crew won’t be able to reach the orbiting lab before the last three spaceflyers head for home.
Unmanned for the first time in a decade?
That situation would leave the $100 billion orbiting lab unmanned for the first time since 2001. Still, it wouldn’t be a disaster, according to NASA officials.
“We know how to do this,” NASA’s space station program manager Mike Suffredini told reporters today. “Assuming the systems keep operating, like I’ve said, we can command the vehicle from the ground and operate it fine, and remain on orbit indefinitely.”
NASA would of course prefer to keep some crew aboard the orbiting lab, Suffredini added. Leaving the space station unmanned would cut back significantly on the scientific research being done 240 miles (386 kilometers) above the Earth. In the wake of the space shuttle’s retirement last month, NASA has repeatedly stressed the importance of that research, and the scientific potential of the station.
But the timing just might not work out. Two Soyuz spacecraft are currently docked to the station to take its six astronauts home. The vehicles are only rated to spend about 200 days in space, so they’ll have to depart soon.
Light at the landing site
Lighting conditions at the Soyuz’s Kazakhstan landing site are also an issue. NASA and the Russian space agency mandate that landings must occur at least one hour after dawn and one hour before dusk, to facilitate better search and rescue operations should any be required.
The lighting window closes for about five weeks on Sept. 19 for the first crew and around Nov. 19 for the second. Waiting for a new window to open would stretch the Soyuz spacecraft beyond their 200-day ratings in both cases, Suffredini said.
So all six astronauts on the space station will almost certainly have left the orbiting lab by mid-November. Russian engineers are working hard to give crewed Soyuz launches the best chance to meet that deadline; the next one is slated to blast off Sept. 21, but that’s almost certainly not going to happen, Suffredini said.
Russia has formed a commission to determine the cause of the Progress crash, and to figure out how to fix it. But NASA says it won’t rush anything, as astronaut safety is its chief priority.
“We’ll just see how it plays out,” Suffredini said.
NASA won’t put any crews on a Soyuz until the rocket has had several successful unmanned launches, he added. Those could happen relatively soon. Russia plans to use Soyuz boosters to launch a commercial payload and another Progress supply ship by late October.
The Progress crash marked the latest in a string of Russian launch failures over the last 10 months. This series of mishaps has caused some concern among U.S. lawmakers and experts, since NASA will rely on Russia to loft its astronauts to orbit until private American crew-carrying spaceships come online. That could start happening by 2015, officials have said.
Growing need for space trash collectors
Greenhouse gas, solar slowdown are lengthening the lifetime of space debris — increasing its threat to satellites and astronauts.
Source: Science News, August 15, 2011
On April 2, 2011 for the fifth time in less than three years, the International Space Station fired its engines to dodge a piece of orbital debris that appeared on a collision path. Other spacecraft also regularly scoot out of the way of rocket and satellite debris. Such evasive action will be needed increasingly frequently, a new study finds.
Friction between the atmosphere and materials passing through it, known as drag force, offers the only natural means for culling detritus left in orbit by space launches. But the thermosphere — a large region of the upper atmosphere — is cooling. A resulting drop in its density is also cutting its drag force, thereby increasing the lifetime of orbiting trash (including pieces in that heavily populated band at 800 to 1,000 kilometers).
Space agencies around the world have been discussing a need to actively remove aerospace debris. One reason: The number of pieces has been steadily rising, driven in part by collisions between orbiting pieces of trash or trash and spacecraft. Among the biggest debris multipliers: a spectacular 2009 crash between the dead Russian Kosmos 2251 spacecraft and the U.S. Iridium-33 telecommunications satellite.
Two years ago, aerospace engineer Hugh Lewis of the University of Southampton, England, and his colleagues calculated that within a few decades, space agencies would have to begin culling perhaps five major pieces of debris annually to slow this collision-enhanced growth in the number of orbiting trash particles. But in a paper in the Journal of Geophysical Research, posted online Aug. 10, the Southampton team now doubles that number, pointing out that the thermosphere’s falling density renders the old trash-pickup requirements obsolete.
The thermosphere does not behave as a gas, explains Lewis. Molecules originating on or near Earth’s surface are propelled upward based on their energy, he observes. With cooling, fewer of them reach satellite (and associated debris) heights.
Growing emissions of carbon dioxide, a greenhouse gas, contribute to the thermosphere’s cooling, the Southampton team points out. The mechanism, Lewis says, appears to be collisions between CO2and atomic oxygen at high altitudes. Those collisions release heat in the form of infrared energy, which radiates out into space — removing warmth from Earth’s atmosphere.
A drop in the sun’s activity will also cool the thermosphere. Although the new JGR analysis assumed that solar cycles during the next 70 years would roughly match those seen over the past 30, this may prove an overly conservative assumption, Lewis acknowledges. This spring and summer, scientists have been reporting that the current solar cycle is particularly anemic. And solar activity might remain lackluster for the indefinite future.
Upper atmospheric increases in carbon dioxide “is the primary cooling agent of the thermosphere,” observes thermosphere climate scientist John Emmert of the Naval Research Laboratory in Washington, D.C. The Southampton team’s new analyses, he says, “demonstrate for the first time that space climate change has significant consequences for orbital debris proliferation and for debris mitigation strategies.”
Trash collection realities
Although actively removing space trash from orbit “is absolutely desirable,” focusing on how many pieces to remove annually “is sort of a moot point, since we don’t know how to clean up even one,” says Nicholas Johnson, chief scientist of NASA’s Orbital Debris Program Office, at the Johnson Space Center in Houston.
There’s also the issue of relative risk, he says. “Although there is a sort of sandblasting going on in space all of the time, both from man-made and natural debris, we’ve only had two operational spacecraft ever hit by man-made debris (that we know of) that sustained any major damage.” One was the Iridium-33 catastrophe, the other a French satellite hit in 1996 which was temporarily disabled. While not wishing to dismiss the risk of a possible catastrophic impact, Johnson notes that the risk of a spacecraft-killing collision remains rare — and that “even two times a small number is still a small number.”
But even if space engineers were given the go ahead to develop a waste-collection service for space, succeeding would likely take a very long time. “There is nothing on the horizon that either DOD or NASA believes can do the job [space-trash removal] from either a technical standpoint or from a financial one,” Johnson notes. Still, that won’t stop U.S. researchers from formally brainstorming solutions — and on Uncle Sam’s dime.
Johnson notes that the President’s new national space policy, announced last year, for the first time directs NASA and the Defense Department to develop technologies for removing threatening debris. Their challenge is complicated by the fact that no one has decided which trash to target first. And the issue isn’t as simple as it might at first seem.
There is debris in low Earth orbit — between 400 km and perhaps 1,000 km — where the Hubble Space Telescope, International Space Station and some other satellites reside. Then there’s the geosynchronous Earth orbit regime at altitudes of perhaps 36,000 km. Protecting craft orbiting at such vastly different altitudes will require different strategies.
Engineers also will have to decide whether to focus on protecting today’s operational spacecraft over the next decade or two or protecting craft that may orbit a century from now.
If the focus is going to be on protecting future generations, Johnson says, then the priority should be ridding the skies of big pieces of trash — perhaps the car-size multi-ton behemoths that can break up into hundreds (if not thousands) of shards. Shifting the emphasis to current-generation spacecraft, he says, will argue for getting rid of small debris. “If we’re going to lose spacecraft in the next two decades,” he explains, “statistically, we’re going to lose them to small things we can’t track.”
Government agencies are already tracking thousands of large debris particles in low Earth orbit. Another half million smaller ones, between 1 and 10 centimeters, also pose threats. Uncertainties in their paths currently prompt satellite managers to be overly conservative, maneuvering spacecraft to new paths more frequently than is truly necessary, Johnson notes. The only way to limit that, he says, is to improve the tracking of trajectories for small, but potentially spacecraft-killing debris.
A Note on Active Debris Removal
July 2011, Courtesy of NASA Orbital Debris Quarterly News
The idea of orbital debris removal was first suggested almost 30 years ago . Since that time, concepts for the removal of small or large orbital debris have been proposed by various groups on a regular basis. However, due to the tremendous technical challenges and the potential high cost, orbital debris removal has never been viewed as practical. In addition, there has been a lack of modeling tools to illustrate the need for debris removal and to quantify the necessary actions and the corresponding benefits for the environment. The two major breakups since 2007 and recent modeling analyses, confirming the instability of the debris population in low Earth orbit (LEO, the region below 2000 km altitude), have certainly re-energized discussions on the subject. The statement in the 2010 National Space Policy of the United States, to pursue research and technology development to remove on-orbit debris, also provides a top-level directive for NASA and DoD to engage in these activities .
Active debris removal (ADR) means to remove debris from orbit beyond the guidelines of the currently-adopted mitigation measures. The term ADR applies to all objects in orbit, including those that already exist in the current environment but lack the capability for deorbit per mitigation guidelines. The planning, technology development, and routine operations of ADR will require a significant amount of resources. Therefore, top-level mission objectives need to be established early to define a well-focused roadmap. Several key questions must be addressed at the beginning of any ADR planning. They include (1) where is the most critical region for ADR, (2) what are the mission objectives, (3) which debris should be removed first, (4) what are the benefits to the environment, and finally, (5) how to carry out the operations. The answers to these questions will drive top-level requirements, necessary technology development, and implementation of ADR operations. They will also pave the way for a clear, efficient, and cost-effective effort to maximize the benefits to the environment and to better protect operational spacecraft in the future.
Recent environmental studies have indicated that the instability of the debris population in the upcoming centuries is only limited to LEO [3-5]. Although there is no atmospheric drag to clean up the environment in the medium Earth orbit (MEO) and geosynchronous orbit (GEO) regions, the buildup of debris there is progressing at a slower rate. Once the critical region for ADR is identified, mission objectives are needed to set the measures for success. Common mission objectives, such as maximizing the benefit-to-cost ratio and following practical mission constraints (in altitude, inclination, size, class, etc.) are always applicable to any ADR concepts. Specific mission objectives, on the other hand, are very diverse and will lead to very different forward paths. These objectives include, for example, controlling the LEO population growth, limiting collision activities, mitigating impact risks (damage, not necessarily catastrophic destruction) for selected spacecraft, or mitigating risks for human space activities. Once a specific mission objective is selected, it needs to be further quantified (e.g., limiting the population growth or reducing mission-ending threats to some pre-set level) to better define the mission requirements.
Which debris objects should be removed first depends on the specific mission objective. The root cause of future LEO debris population growth will likely be accidental collisions involving large and massive intact objects (rocket bodies, R/Bs, or spacecraft) . In general, they are at least several meters in size. If the ADR mission objective is to stabilize the debris population or to reduce major catastrophic collisions in the future environment, then these objects should be targeted for removal.
The LEO-crossing debris population below 10 cm roughly follows a power-law size distribution – meaning there are far more smaller debris than larger ones. This means the main mission-ending threat for operational spacecraft in the environment always comes from debris just above the threshold of the vehicle’s impact protection shields. The critical debris size will vary between spacecraft, since they all have different configurations and shielding designs. For most operational spacecraft, however, any impact by debris between 5 mm and 1 cm is likely to cause mission-ending damage. The chances of similar damage diminish if the vehicle is impacted by smaller debris and increase if impacted by larger debris. Because of the power-law size distribution, debris in the 5-mm-to-1-cm regime represent about 80% of all objects larger than 5 mm. Therefore, if the ADR objective is to reduce the mission-ending threat for most operational spacecraft, then the removal operations should focus on the 5-mm- to-1-cm debris.
Space Debris Risks Increasing
Source: Physics Today, November 2009
A growing storm of debris flying around in space is dramatically increasing the risk of orbital crashes, and steps to avoid them will add greatly to the costs of future spaceflight, UK space experts say.
Their study predicts that near misses between debris and spacecraft in orbit will rise by 50% in the next 10 years and by 250% by 2059, to more than 50,000 a week.
“The time to act is now, before the situation gets too difficult to control,” said Hugh Lewis of the University of Southampton’s school of engineering science, who led the study. “The number of objects in orbit is going to go up, and there will be impacts from that.”