Tag Archives: satellite

Russian BLITS satellite blitzed by Chinese space debris

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Video simulations of Russian BLITS satellite orbiting Earth and then being struck by debris from the Chinese Fengyun 1C

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.

The spreading debris cloud from the Chinese anti-satellite test in 2007. Left: one month after the hit. Right: 6 months later. Credit: NASA Orbital Debris Program Office

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.

BLITS is essentially two spheres (one nested in the other) that measures a mere 6.7 inches in diameter. Half of the outer ball has a reflective coatings. Laser light beamed to the satellite returns to Earth. Timing the pulse gives a precise distance to the satellite. Credit: IPIE

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.

Frame grab from the video showing the impact of Fengyun 1C debris on a collision course with Russia’s BLITS satellite.

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.

The night the Cosmos fell to Earth

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One of Russia’s Cosmos satellites (there are many in a series). Cosmos 1484 gathered data on natural resources from orbit.

Last night around 9:30 p.m. Eastern time, hundreds of residents living along the East Coast of the U.S. were treated to a spectacular, slow-moving, long-lived meteor about as bright as the full moon. But there was something different about this meteor – it was man-made.

To get a feeling for what most of us missed, check out the American Meteor Society’s fireball reporting site. As of this afternoon, over 30 reports from 8 different states have been received that correlate with the time and path of the Russian Cosmos 1484 reconnaissance satellite which was expected to re-enter the atmosphere around that time. The U.S. Strategic Command reported the re-entry or “decay” (in satellite lingo) at 9:38 p.m. EST +/- 17 minutes.


Short video of Cosmos 1484 crossing in front of the moon taken by an amateur astronomer

Cosmos 1484 was launched from Russia’s Baikonur cosmodrome in 1983, the same place Yuri Gagarin, the first human to orbit the Earth, lifted off on April 12, 1961. The Cosmos probe was classified as a “remote sensing” satellite, another way of saying it studied its subject without touching it – from orbit. Using cameras, radar and other sensors, Cosmos gathered information on natural resources like forests, cropland, lakes and seas for use by the-then Soviet Union in planning its economy.

When the sample capsule from the Japanese Hayabusa spacecraft entered Earth’s atmosphere in June 13, 2010, it created a spectacular fireball. The capsule, containing particles from the asteroid Itokawa, landed safely. Click for awesome video. Credit: Takashi-Ozaki, Yomiuri Simbun, AP

Over time, the orbit of 5,500-lb. Cosmos 1484 “decayed” due to the inevitable drag of air molecules. While there aren’t many of them at typical low Earth-orbit altitudes, their effect accumulates and accelerates over time.

Even at 250 miles high, the International Space Station needs to periodically fire its engines to boost its altitude from time to time. Some newer satellites have rockets and controls to counter atmospheric drag and maintain a preferred orbit. Many others, especially the older ones like Cosmos 1484, either don’t or have run out of fuel.

Air drag lowers a satellite’s orbit, which causes it to speed up, which further increases drag, which speeds it up even more in an ever-spiraling process until the satellite finally re-enters the atmosphere in a ball of fire. Satellite re-entry speeds are normally much slower than the cosmic speed of meteors – those bits of asteroid and comet dust – so they take their time crossing the sky as they put on a fiery show.

One of Skylab’s air tanks that made it through re-entry and crashed to the ground. It’s on display at US Space and Rocket Center, Huntsville, Alabama. Credit: Wikipedia

A falling satellite – that’s what you lucky East Coasters saw last night. I’ve only heard of one report of fragments picked up by Doppler weather radar possibly in Georgia. Most satellites completely burn up upon re-entry, but sometimes pieces survive. One notable example was the plunge of NASA’s Skylab Space Station when it re-entered over Australia near Perth on July 11, 1979. After a mouth-dropping show of satellite-frying fireworks, at least two dozen pieces were picked up.

If you’re interested in what satellites will be dropping back to Earth in the near-future, click over to Satview’s Reentry site.

Earth at night glows with lovely and loathsome lights

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This image of the continental United States at night is a composite assembled from data acquired by the Suomi NPP satellite in April and October 2012. City and highway lights, gas flares, wildfires and a bit of reflected moonlight are visible. Click for a huge version. Credit: NASA Earth Observatory/NOAA NGDC

Wherever we go, our lights go with us. If we were more thoughtful about choosing the right type of lighting fixtures, it wouldn’t be such a problem, but we’re generally not. Photos taken late last year by the Suomi NPP satellite of Earth at night show the human footprint in blazing garlands of twinkling orange lights strung along coastlines, cities and highways.

While the sight is beautiful on one level, it’s a disturbing waste of good energy. Much of the electric lighting seen from space spills upward to brighten the night sky instead of being directed at the ground where it’s needed.

Comparison photos of the Bakken oil fields region in the year 2000 before active drilling and in 2012 with drilling going full bore. The photo at left was made by the Defense Meteorological Satellite Program; at right by Suomi NPP. Click to enlarge. Credit: NOAA, NASA

One of the most glaring examples of new light pollution shows up in the Bakken shale fields of northwestern North Dakota. Although one of the least densely-populated areas of the United States, the region has seen widespread oil-drilling and natural gas production in recent years. Most of the bright dots are lights associated with drilling equipment and temporary housing near drilling sites, but some are natural gas flares.

Closeup satellite image of lighting in the Bakken oil fields of northwestern North Dakota. Credit: NASA Earth Observatory/NOAA NGDC

Storage facilities and pipelines haven’t kept up with production, so the excess is burnt off in flares. This may sound like a bad idea, but it’s better than releasing it directly into the atmosphere. Methane is far nastier than carbon dioxide when it comes to the greenhouse effect.

Well-designed fixtures shield and direct light toward the ground. This example is from Manchester, UK.

While we all know lighting is necessary to carry on with tasks at night like driving home or picking up the kids at school, wisely-designed fixtures that contain the light in a box and direct it downward not only provide ample illumination, they also save energy, reduce glare and minimize light pollution of the night sky we all love.

Full moon on September 30, 2012 over the Persion Gulf. You can see both the lights of cities and highways as well as details of the landscape. Click to enlarge. Credit: NASA Earth Observatory/NOAA NGDC

Not all Earth lighting seen from orbit is manmade. Moonlight and aurora cast their natural hues across the planet’s skin, too. The Suomi NPP satellite captured a series of pictures showing dramatic changes in illumination of the Persian Gulf region between September 30 and October 15, 2012 when the moon waned from full to new phase.

With the moon at gibbous phase, the difference in lighting is quickly apparent. Click to enlarge. Credit: NASA Earth Observatory/NOAA NGDC

Notice that as the moon’s phase lessens, the cities become more obvious while the landscape darkens. To see all four panels showing the complete transition from full to new moon, click HERE.

The southern lights swirl over Antarctica in this satellite image taken on July 15, 2012. Look closely and you’ll see details in the ice shelf along the edge of ocean (top) lit up by the aurora. Credit: NASA Earth Observatory image by Jesse Allen and Robert Simmon

We’ll leave you with the choicest image of all – the aurora austrinus or southern lights, counterpart to the aurora borealis. Suomi NPP captured this image on July 15, 2012 over Antarctica’s Queen Maud Land and the Princess Ragnhild Coast. At the time the continent was shrouded in mid-winter darkness with a waning crescent moon providing very little illumination. LIght from the aurora was bright enough however to reveal icebergs and the coastline.

If you like your skies dark, here are some outdoor lighting tips on reducing light pollution around the house. For more on the issue, I highly recommend a visit to the International Dark-Sky Association’s Frequently Asked Questions.

Palm-sized Japanese satellite flashes a greeting from the sky

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The flashing green LEDs of Japan’s FITSAT-1 were photographed as the satellite passed through the constellation Taurus last night. Credit: Tsuyoshi Watanabe

Can we get any more plates spinning?  So far we’ve seen two asteroids fly by Earth, the launch of a North Korean satellite, two meteor showers expected for tomorrow night and now the return of the space station to the evening sky. Flying near the big bird is a tiny new satellite you can watch go blink in the night.

The Japanese satellite called FITSAT-1 and nicknamed Niwaka is a 4-inch (10-cm) cube weighing 3 lbs. It’s the creation of a group of scientists at Fukuoka Institute of Technology (the FIT in FITSAT) and released from the International Space Station into its own orbit near the station.

Professor Takushi Tanaka holds a model of FITSAT or Niwaka at his laboratory in Fukuoka. The 4-inch cubic satellite, which has LED lights on surfaces, was launched from the space station on October 5, 2012. It transmits an LED message in Morse code across the night sky. Credit: AFP photo / Fukuoka Institute of Technology

The palm-sized cube’s purpose is to test a new transmitter that can send JPG images back to Earth within six seconds as well as investigate optical communications via satellite.

Niwaka’s also outfitted with numerous high-intensity LEDs that will flash the greeting Hi De Nikawa Japan (“Hi this is Nikawa Japan”) in Morse code in 200-watt pulses. Mission planners say the flashes may be visible with the naked eye and definitely with binoculars. Ham radio operators can listen in to Niwaka’s radio beacon which transmits at a frequency of 437.250 MHz.

Observers in the northern hemisphere will see the front of the satellite, which is studded with green LEDs, while southern hemisphere observers will see the “backside” with red LEDs.

Photo taken by FITSAT-1 of the International Space Station (ISS) after it was launched into orbit in October. Credit: Fukuoka Institute of Technology

Since darkness is required for viewing the lights, they won’t flash when the satellite is in sunlight – the way we see the space station – but rather once the sun has set on Niwaka.

Japanese mission control planned to activate the lights over Pennsylvania, Ohio, New Jersey and the Virginias early this morning between 1:14 – 1:16 a.m. (EST). So far, I’ve not heard of any sightings.

European/British Isles observers will get their chance for flashes tomorrow Dec. 13 between 10:10 – 10:14 p.m. Greenwich Time. That’s it for now – when the next set of times is announced, I’ll post them here. I’m eager to see this artificial “twinkling star” myself. Maybe I’ll even use my green laser to return the greeting. For maps, times and tracks of FITSAT passes, check out the Visual SAT-Flare Tracker 3D.

Picture of FITSAT-1 along with several other mini-satellites in space against the background of one of the space station’s solar arrays. Credit: Fukuoka Institute of Technology

One satellite you’ll see with ease over the next few weeks is the International Space Station. Times for the Duluth, Minn. region are listed below. To know when to spot it from your town, go to Spaceweather’s Satellite Flybys page or log in to Heavens Above. The latter site not only gives time and direction to look, but if you click on the time link, you’ll be shown a map of the station’s path through the sky.

Times for the Duluth, Minn. region:

* Tonight Dec. 12 starting at 6:25 p.m. A brief pass in the southwestern sky
* Weds. Dec. 13 at 5:35 p.m. across the south
* Thurs. Dec. 14 at  6:20 p.m. Brilliant pass up from the west and then disappearing in Earth’s shadow when highest in the southern sky
* Fri. Dec. 15 at 5:30 p.m. Brilliant pass high in the southern sky. Fades out at 5:35 p.m. right next to Jupiter low in the northeast.
* Sat. Dec. 16 at 6:16 p.m. Another very bright pass across the north, disappearing into Earth’s shadow just above the North Star
* Sun. Dec. 17 at 5:26 p.m. Wonderful high pass across the top of the sky. Brilliant!

Galaxy 11 to Astro Bob – Do you read me?

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The mystery object in Ophiuchus seen last month. It looked like a 3rd magnitude star (one level fainter than the Big Dipper stars) that “didn’t belong” there. Photo: Bob King

One night last month while setting up the telescope for a night of observing I noticed a “new” star in the southern constellation Ophiuchus. I first thought it was a satellite but it appeared stationary and didn’t fade away.  Hmmmm. Could this be a new nova? It was in the Milky Way band where most novae (explosive outbursts of stars) are discovered. Just in case the object proved to be something interesting, I fired off a few photos.

Close up view of Ophiuchus and Galaxy 11. In 30 seconds time, the satellite barely moved while the stars show obvious trails from Earth’s rotation. Photo: Bob King

The longer the light remained the more excited I became until I noticed that it was moving very slowly to the east. Well, there went my novae hypothesis. The mystery object soon began to fade; five minutes later was barely visible to the naked eye.

Feeling slightly deflated, I realized I’d been watched a long, slow flare from a satellite. The sun, satellite and my spot on the hill were lined up just right for sunlight to reflect off an antenna and back to my eye.

Later that night I fished around and discovered my nova was Galaxy 11, an active communications satellite serving both the U.S. and Brazil.

Galaxy 11 is a communications satellite in geosynchronous orbit around Earth.

Galaxy 11 relays TV programming like the Celebrity Shopping Network and National Geographic to widely separated points on Earth.

Most of the satellites we see like the space station are in low-Earth orbit or LEO. Being relatively close to the planet they circle around it faster than the Earth rotates. That’s why we see the 240-mile-high space station cross the sky in only five minutes. Every 90 minutes it completes another orbit.

A satellite in geostationary orbit (shown above) remains in exactly one spot in the sky.  Credit: Francisco Esquembre

The farther a satellite is from Earth, the slower it moves across the sky. If you ever see one slowly creeping its way through the heavens, you know it’s much higher than the space station located some 240 miles up in LEO.

It’s possible to send a satellite far enough away – 22,236 miles to be exact – so that it appears to stay fixed or nearly so in just one place in the sky, hovering over the planet like an all-seeing eye.

Birds at this towering altitude are said to be in geosynchronous orbit. You may have also heard of geostationary satellites. Geostationary is a more specific term and refers to a satellite in a geosynchronous circular orbit directly over the equator. These remain in exactly the same spot in the sky; geosynchronous satellites are in slightly inclined orbits and remain in the same small area of sky.

Arthur c. Clarke at his home in Colombo, Sri Lanka in 2005

It was the late science fiction writer Arthur C. Clarke who in 1945 first suggested that a global communications network would be possible using three equally spaced geostationary satellites orbiting above Earth’s equator. NASA finally tested Clarke’s idea in 1963, and lo and behold in 2012 we can hardly live without them.

Geosynchronous satellites are essential for TV broadcasting, satellite radio, weather forecasting and global communications.

Most geosynchronous satellites are faint because they’re far away and require binoculars or a telescope to see. One in while however they flare in sunlight like Galaxy 11 and become easily visible with the naked eye.

Illustration showing space debris and active satellites orbiting Earth. Geosynchronous satellites responsible for relaying communications around the world define the distinct outer ring. The dense inner circle are satellites in low Earth orbit. Credit: NASA

It’s a real treat to bump into a geosynchronous satellite in the telescope. They hang out near the celestial equator in the sky. Once found, a “geosync” stays put in the field of view while all the other stars drift by, carried along by Earth’s rotation. Even though I didn’t discover a nova that May night, I’m remain in admiration of Clarke’s genius and mankind’s ingenuity.

Beauty at dawn plus tips for happier satellite watching

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An aureole of light surrounds Jupiter as it shines through low clouds last night north of Duluth, Minn. Photo: Bob King

The ailing Russian Phobos probe was a no-show for me last night. You may have had the same luck. Unless satellite flyby engines are updated with the latest orbital changes, the times and paths listed aren’t always reliable. This morning I posted a request to the visual satellite observers group known as Seesat-l for a more reliable, accurate source of satellite predictions. Several people got back to me with two other online flyby calculators that look like excellent, up-to-date tools. One of the easiest to use is CalSky.

When I clicked on the link, it instantly knew my location and plotted a list of Phobos-Grunt passes for the upcoming week. Talk about effortless! Included for each day are links to the satellite’s ground track (overflight path) and a star chart to show its path through the sky.

The second is a very nice, interactive site created by Simone Corbellini called Visual Sat-Flare Tracker 3D. Once you key in your location, it shows predicted passes for the next 24 hours. The big star map is a big plus! Try them out and let me know how they work. And if you have questions on terminology, etc., just use the Comment section in the blog to ask for help.

Last night’s stars didn’t sparkle any less despite Phobos-Grunt’s absence. The fresh snow cover added cheer to the darkness as the Big Dipper settled in for a nap behind the leafless trees. The familiar constellation ebbs lowest in late November and for many disappears altogether until the wheeling of the Earth brings it back into view in the early morning hours. In the south, Jupiter rose to dominate the sky until clouds attempted to quench its radiance. They never succeeded. The planet blasted through even when all the other stars were gone. No one puts Jupiter down.

Look low in the southeastern sky about an hour or so before sunrise Tuesday morning for the delightful trio of moon, Spica and Saturn. Created with Stellarium

Tomorrow morning there will be a very attractive gathering of the thin crescent moon, Virgo’s brightest star Spica and the planet Saturn. If you’ve had any difficulty finding the planet after its recent emergence into the November dawn sky, this is your chance to see it with ease. The map shows the sky around 6 a.m. or about and an hour and 15 minutes before sunrise. Telescope owners are encouraged as always to tote our their instruments and check out one of nature’s more unique creations – the rings of Saturn. I can never seem to get enough of them. The dim, earth-lit portion of the moon to the right of the sun-illuminated crescent should be especially striking. Binoculars will allow you to see darkened lunar seas and even the shapes of several larger craters.

Dat’s dee vay dee kookie krumbles – ROSAT coming down tonight

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The German ROSAT X-ray observatory was used by scientists in the 1990s to study X-ray emitting objects in the sky.Credit: AP

Sometime later today or early tomorrow morning, the German ROSAT X-ray satellite is expected to plunge into the atmosphere as it makes its final orbit around the Earth. According to the U.S. Strategic Command, it will happen at 9:34 p.m. Central time (2:34 GMT) this evening with an accuracy of +/- 7 hours.

Since its orbit takes it over a vast span of planet Earth between the latitudes of 53 degrees north and south, no one knows yet where it will land. What we do know is that 3,750 lbs. in some 30 pieces will survive the heat and pressure of re-entry and strike water or ground when the moment finally comes. If by chance you’re in position to catch the fall, the crumbling ROSAT will make for a series of spectacular fireballs. I’ll keep you updated through the day as times and fall locations are refined.

** UPDATE 4:15 p.m. CDT — Fall at 9:31 p.m. Central time +/- 3 hours
** UPDATE 8:15 p.m. CDT — Fall at 9:04 p.m. Central time + / – 2 hours
** UPDATE 10 p.m. CDT — Just a few minutes ago, officials at the German Aerospace Center confirmed that ROSAT re-entered the atmosphere between 8:45 and 9:15 p.m. CDT. Not known yet if pieces reached the Earth’s surface.

Another one bites the dust – ROSAT satellite coming down soon

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Jupiter and the waning gibbous moon shine between fall trees late last night. Photo: Bob King

Darkness comes early in mid-October. For some, the disappearance of daylight is tough to handle. We feel like moles in a dark tunnel from dinnertime until the next morning’s breakfast. Most people seem to be more in tune with daylight instead of darkness, yet many sky watchers have learned to embrace the night. The stars may be dim but getting to know them and the ragtag galaxies, planets and nebulae is like being in a room with a thousand candles. Their light and energy stimulate a reflective and peaceful state of mind as satisfying in its way as streaming rays of sunshine. As daylight trickles away, I hope you’ll also find light and inspiration in the nights ahead.

Artist view of the German X-ray observatory ROSAT in space. Credit: German Aerospace Center

Looks like we’re in for Satellite Crash Act II. The German science observatory ROSAT, short for Roentgen Satellite, make its fiery plunge to Earth sometime between October 22-24 over a broad zone between latitudes 53 degrees north and south. Like the widely-publicized burn-up of NASA’s Upper Atmosphere Research Satellite (UARS), this satellite will also come down uncontrolled. Satellite trackers will only have a general idea of where it might land hours before it does. As with UARS, you shouldn’t be too worried. Since the Earth is 2/3 covered in water and thankfully still  blessed with a lot of uninhabited land, there’s a good chance it will crash without incident just as UARS did over the South Pacific.

When ROSAT finally does come down, it will be traveling at nearly 17,000 mph. The tremendous heat generated by friction with the air will burn up much of it up, but German scientists estimate 30 pieces will survive. Unlike UARS, ROSAT’s made of specially hardened components, so more of it will remain intact during re-entry – 3,750 lbs. of pieces will shower the ground versus an estimated 1,200 lbs for UARS. There’s  a 1 in 2,000 chance a person will be struck by the debris, which breaks down to a 1 in 14 trillion chance any particular individual will be hit.

An X-ray emitting neutron star (upper left) blinks out as the moon passes in front of it in these photos made by ROSAT. High-energy X-rays are shown in yellow, low energy ones in red. The moon scatters X-rays given off by the sun. Credit: ROSAT, MPE, NASA

ROSAT, an orbiting space telescope optimized to study the sky in X-ray light, is named after William Roentgen, the German scientist who discovered X-rays back in 1895. It operated for over 8 years beginning in 1990 before being shut down in 1999. Many high-energy objects in the universe emit X-rays including neutron stars, black holes, galaxy clusters and debris blasted into space by supernovas called supernova remnants. Since Earth’s atmosphere absorbs X-rays, telescopes made to focus this powerfully energetic light need to be lofted into orbit.

ROSAT created a detailed (for its time) map of the X-ray sky, took the first photos of X-rays bouncing off the moon and discovered X-ray emission in comets. It’s since been superseded by the Chandra X-ray Observatory with its much finer resolution.

This composite view of the entire sky in X-rays was made by ROSAT. The red is radiation emitted by hot gas in the halo of the Milky Way, the yellow from nearby gas bubbles at several millions of degrees and the highest energy blue from supernova remnants. Credit: ROSAT

You can still watch ROSAT track across your sky in the coming week before its plummet. Below are times when it’s visible from the Duluth, Minn. region. For times for your neighborhood, log on to Heavens Above and select your city and then click the ROSAT link. You’ll be shown a list of passes. When you click the date link, a nifty map pops up to help you know exactly where to look. You can also enter your zip code at the Spaceweather Flyby link and get times and general directions.

Like the space station, ROSAT travels from west to east across the sky, but it’s not nearly as bright. Expect to see a steady moving “star” of about 2nd magnitude or similar in brightness to those in the Big Dipper. It zips along fairly quickly now that its orbital altitude has been dropping from friction with the upper atmosphere.

* Tonight Oct. 14 beginning at 7:55 p.m. A brief and faint (magnitude 4) appearance low in the northwestern sky in the Big Dipper.
* Saturday Oct. 15 at 7:41 p.m. A better and brighter show tonight at mag. 2 1/2. Appears in the northwest and moves through the Big Dipper before fading away under the North Star.
* Sunday Oct. 16 at 7:25 p.m. Excellent high pass in the north at mag. 2.2
* Monday Oct. 17 at 7:08 p.m. Similar pass to yesterday. Bright at mag. 2.0

What goes up must come down – the tale of a doomed satellite

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The Upper Atmospher Research Satellite or UARS taught us much about the chemistry of the atmosphere and ozone layer during its 14 years of active life. Credit: NASA

You may have already gotten wind that the NASA’s Upper Atmosphere Research Satellite (UARS) will soon be coming back to Earth … in pieces. The 13,000 lb. satellite was launched from the space shuttle Discovery in 1991 to study the chemical makeup of the atmosphere with particular emphasis on the ozone layer. It also measured winds and temperatures in the stratosphere and monitored ultraviolet light emitted by the sun. UARS played a major role in confirming that chlorofluorocarbons or “CFCs” like those used in Freon, aerosol propellants and solvents lead to ozone depletion and the formation of the Ozone Hole over Antarctica.

After 14  years of good science and its fuel used up, NASA switched off the satellite in December 2005 after a final nudge toward Earth to begin the slow process of “decay” or return through our atmosphere. Since then its orbit has been slowly shrinking year by year. UARS originally orbited 375 miles high, but as of September 16 it swings ’round the planet in an ellipse measuring just 140 x 155 miles.

Rarified as it is, the upper atmosphere increases the drag on the satellite, reducing its speed and bringing it closer to Earth. A big increase in solar activity since early last week also plays a role. Ultraviolet radiation from flares and other solar activity heats and expands the outer atmosphere, increasing drag and hastening the decay of UARS’ orbit.

The Remote Manipulator System holds onto the Upper Atmosphere Research Satellite before being released by the space shuttle Discovery in September 1991. Credit: NASA/ Marshall Space Flight Center

At the moment, NASA scientists predict a fiery re-entry this coming Friday the 23rd, give or take a day. Because the satellite has no fuel left, the point of re-entry can’t be controlled on the way down, but since 2/3 of the Earth is ocean, it will more than likely land there. UARS is a large, heavy satellite weighing 6.3 tons and measuring 35 feet long by 15 feet in diameter. Most of it will vaporize when it plunges in fireball-like fashion through our atmosphere, however some 1,000 lbs. of satellite components are expected to land somewhere on Earth between the latitudes of 57 degrees north and 57 degrees south — the satellite’s overfly zone. That’s a very large area! And that’s why the chances of anyone getting hit by a piece are extremely remote.

There is a 1-in-3,200 chance a piece of debris could injure or kill a person, according to an assessment by NASA. “I hope [people] don’t get too concerned because this is something with a very low probability of anyone being hurt or anyone’s property being damaged,” said Nick Johnson, chief scientist for NASA’s orbital debris program at the Johnson Space Center in Houston. “Unless we build these things out of papermache, we can’t reduce the risk to zero,” he later added.

Illustration showing space debris and active satellites orbiting Earth. Geosynchronous satellites responsible for relaying communications around the world define the distinct outer ring. The dense inner circle are satellites in low Earth orbit. Credit: NASA

To further put your mind at ease, since the dawn of the Space Age some five decades ago, no human has been killed or even hurt by an artificial object falling from the heavens, though in 1997 a piece of debris from a U.S. Atlas II rocket brushed a woman’s shoulder in Oklahoma, the only known instance of a “grazing fall” on a human. Pieces of space junk are falling harmlessly all the time. Last year one satellite-related object per day burned up in our atmosphere according to Johnson.

Ever since UARS was decommissioned, it’s been a little more than another (albeit large) piece of space junk, hence the need to see it through to its ultimate demise. It’s too early yet to know where and exactly when it will land, so NASA will be posting regular updates at this site. I’ll also do the same. If you do see the fall and later find a piece, the agency asks that you not touch it, but contact a local law enforcement agency. I know the chances are small, but I bet many of us are hoping we’ll get a glimpse of the spectacle as UARS takes the final plunge.

10-second time exposure of UARS showing a small flare taken in June 2010 by Dutch satellite observer Marco Langbroek. Click to visit his satellite blog

UARS is an easy satellite to spot, sometimes appearing as bright as the brightest stars though typically it’s more like those in the Big Dipper. If you’d like to catch its last few passes in the morning sky, go to Heavens Above, log in and select the UARS link. For the Duluth, Minn. region, UARS will cruise low across the southwestern sky tomorrow (Monday) morning starting at 6:15 a.m. In tomorrow’s blog, I’ll update with all remaining passes as well as roll out new times to watch the International Space Station, which has once again returned to view at dawn.

Rock out under the space disco ball tonight

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Japan's high-tech disco ball, EGP, revolves around Earth every 116 minutes at an altitude of 900 miles. It's used to pinpoint remote Japanese islands and to study Earth's gravity field and motions of crustal plates. Credit: JAXA

In a Saturday Night Fever mood? Break out the medallions and your best polyester – we’re heading outdoors tonight to spot the 7-foot diameter orbiting disco ball called Hydrangea Flower (Ajisai in Japanese). Known better among satellite watcher by its more formal name – Experimental Geodetic Payload or EGP – this twinking “star” will amaze your eyes as you track it during a typical 18-minute long passage across the sky.

18 minutes is a long time compared to the approximately five minutes it takes for the space station to pass from horizon to horizon. That’s because EGP orbits Earth at an altitude of 900 miles versus the station’s approximately 230 mile orbit. Being farther from Earth, it moves more slowly through the sky.

EGP is a Japanese satellite launched in 1986 with a dual mission: to test a new launch vehicle and determine the exact positions of isolated and remote Japanese islands. And it really does look like a disco ball. The hollow sphere is covered in 318 mirrors and 1436 “cube corners” or retro-reflectors. Retro-reflectors are optical devices that reflect any light falling on them directly back in the direction from which it came. They’re used in everyday things like the insides of red tail-light covers on cars and bicycle reflectors. Even the paint on road signs contains reflectors in the form of tiny glass beads.

Scientists on the ground bounce a laser beam off one of the many mirrors or retro-reflectors on EGP and detect the return beam reflected back. Since the satellite’s orbit is exactly known, the round-trip return time for the beam will yield a location for the observer’s position on the ground accurate to millimeters. Satellite geodesy, as it’s known, is so accurate, it can detect the molasses-like movement of Earth’s crustal plates over short time scales.

A 35-second time exposure with a telephoto lens shows a series of flashes (some in groups of three) from EGP this past Saturday night as the satellite traveled through Draco the Dragon. As sunlight strikes the satellite's many mirrors, we see flashes of light. Details: 100mm lens, f/2.8, 35-seconds at ISO 1600. Photo: Bob King

Two nights ago I watched a pass of EGP. There’s nothing quite like it. With all those mirrors, the satellite flashes rapidly and irregularly like a string of firecrackers going off. The flashes were too faint to see with the naked eye – except from a dark sky site – but extremely easy in any pair of binoculars. The key to finding it is to use the simple maps available on the Heavens-Above satellite observing website.

Once you log on and select your city, look under the Satellites heading and click on Select another satellite. In the U.S. Space Command ID box, type in EGP’s ID number 16908 and click Submit. Clicking on the Ajisai (EGP) link takes you to a info page. At upper right, click on Passes (visible). Now just pick a convenient viewing time. There are many, since EGP is so high up it’s visible late into the night and early morning. I scanned the list of passes and selected the 22:09 (10:09 p.m.) pass tonight for Duluth, Minn. (see below).

For the Duluth, Minn. region tonight, the space disco ball will pass very close to Vega, one of the easiest-to-find bright stars in the sky. At the times shown, Vega will lie almost directly overhead. Created with Stellarium

When you click on the date link for the pass you’d like to see, you’ll be shown two maps. The top one is a wide view of the whole sky showing the entire length of the pass. The bottom one shows the brightest segment of the pass along with tick marks showing where EGP will be at particular times along its path. Pick a pass or a part of EGP’s path that takes it near a bright, easy-to-find star. Note the time when it’s near that star, then go outside five or 10 minutes before EGP’s arrival to let your eyes to get used to the dark.  A minute before it shows up, point your binoculars at your “guide star” and just wait. Pretty soon you’ll see it popping and flashing along.

While watching it Saturday, I counted about two strobe-like flashes per second. Twinkle, twinkle little star, indeed!