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Saturday, September 24, 2011

Remembering the Skylab - ‘UARS’ – about to fall…..

It is making more news than it did during its active life spanning 7317 days !  Do you know Henny Penny or the small town of Oaken Oaks where Zach Braff rings the school bell  ??     Decades back, there  was so much of hype  and every one started confounding theory that ‘what goes up must come down’ (why this never happens to spiralling gold price ?  Those objects in orbit  including Satellites experience drag as they move through the outer reaches of Earth's atmosphere.

Those of us who are 40+ of age, would well remember the high drama, tension and sensation caused in July 1979.   In India, it captured first page in all vernacular dailies – all vying each other trying to predict when and where it would occur and how the World could be brought to an end, or at least how a Continent or a Nation or a City could be wiped out of the map forever.  People started fearing for their lives and started hoarding their most valuables in secretive places !!

-----   those were not the days of newschannels of 24X7 – still the demise of Skylab was a big International media event, with merchandising, wagering on the time and place of re-entry.   The San Francisco Examiner offered a $10,000 prize for the first piece of Skylab delivered to its offices; the competing Chronicle offered $200,000 if a subscriber suffered personal or property damage.   Special teams were readied to head to any country hit by debris and requesting help.  Now perhaps not much attention is paid to the fragment of  Skylab recovered after its re-entry through Earth's atmosphere, on display at the U.S. Space & Rocket Center.

Ground controllers adjusted Skylab's orientation for ideal re-entry dynamics at approximately 16:37 UTC 11 July 1979. They aimed the station at a spot 810 miles (1,300 km) south southeast of Cape Town, South Africa. The station did not burn up as fast as NASA expected; due  to a 4% calculation error, debris landed southeast of Perth, Western Australia.   The  Miss Universe pageant was  held a few days later, on 20 July 1979 in Perth and a large piece of Skylab debris was displayed on the stage.  Skylab was a space station launched and operated by NASA. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. Numerous scientific experiments were conducted aboard Skylab during its operational life, and crews were able to confirm the existence of coronal holes in the Sun. Thousands of photographs of Earth were taken, and records for human time spent in orbit were extended.

Now the World’s attention on UARS ‘Upper Atmosphere Research Satellite’ heading toward re-entry into Earth's atmosphere. The satellite was predicted to re-enter sometime on the afternoon of Friday, Sept. 23, 2011, but it hasn't been easy to precisely determine the path and pace of UARS despite the fact that scientists well understand how satellites move through space.

Artist impression of UARS – source NASA

UARS  is an orbital observatory whose mission was to study the Earth’s atmosphere, particularly the protective ozone layer. The 5,900-kilogram satellite was deployed from Space Shuttle Discovery during the STS-48 mission in September 1991. UARS entered orbit on 15 September 1991 at an operational altitude of 600 kilometers, with an orbital inclination of 57 degrees.  The original mission duration was to be only three years, but in June 2005, 14 years after the satellite's launch, six of its ten instruments were still operational. UARS was decommissioned in 2005, and a final orbit-lowering burn was performed, followed by the passivation of the satellite's systems, in early December 2005. On October 26, 2010, the International Space Station performed a debris-avoidance maneuver in response to a conjunction with UARS.    Currently, the satellite is expected to fall from orbit during the early morning of September 24, 2011, Eastern Daylight Time.

For our easier understanding, UARS / Skylab are not alone, there are many other objects on sky which could descend on you at any point of time !  

Known as Orbital debris, they are any man-made object in orbit about Earth which no longer serves a useful purpose.   This would include derelict  spacecraft and upper stages of launch vehicles, carriers for multiple payloads, debris intentionally released during spacecraft separation from its launch vehicle or during mission operations, debris created as a result of spacecraft or upper stage explosions or collisions, solid rocket motor effluents, and tiny flecks of paint released by thermal stress or small particle impacts.   According to NASA, more than  22,000 objects larger than 4 inches (10 cm) are currently tracked by the U.S. Space Surveillance Network. Only about 1,000 of these represent operational spacecraft; the rest are orbital debris.  Most orbital debris reside within 1,250 miles (2,000 km) of Earth's surface.   In low Earth orbit (below 1,250 miles, or 2,000 km), orbital debris circle the Earth at speeds of between 4 and 5 miles per second (7 to 8 km/s). However, the average impact speed of orbital debris with another space object will be approximately 6 miles per second (10 km/s). Consequently, collisions with even a small piece of debris will involve considerable energy.    The higher the altitude, the longer the orbital debris will typically remain in Earth orbit.

Not all of them pose danger to Earth and humans.  A significant amount of debris does not survive the severe heating which occurs during re-entry. Components which do survive are most likely to fall into the oceans or other bodies of water or onto sparsely populated regions like the Canadian Tundra, the Australian Outback, or Siberia in the Russian Federation. During the past 50 years an average of one cataloged, or tracked, piece of debris fell back to Earth each day. No serious injury or significant property damage caused by re-entering debris has been confirmed.   There are official policies of United States and Space agencies of other countries to minimize the creation of new orbital debris.

Now the official time of falling of the satellite  is 12:45 a.m., Sept. 24, Eastern Daylight Time (3:45 a.m. to 4:45 a.m. GMT) whence UARS will be passing over Canada and Africa, as well as vast areas of the Pacific, Atlantic and Indian oceans. The risk to public safety is very remote.

As you walk or drive down on the street, be aware and look to the skies for the falling satellite !!!!!!

Chicken Little is a 2005 computer-animated science fiction family comedy film produced by Walt Disney,  loosely based on the fable The Sky Is Falling.    Henny Penny, also known as Chicken Licken or Chicken Little, is a fable in the form of a cumulative tale about a chicken who believes the world is coming to an end. The phrase The sky is falling! features prominently in the story, and has passed into the English language as a common idiom indicating a hysterical or mistaken belief that disaster is imminent.

In the small town of Oakey Oaks, Chicken Little (Zach Braff) rings the school bell and cries for everyone to run for their lives. This sends the whole town into a frenzied panic. Eventually they calm down enough to ask him what's wrong, and Chicken Little explains that a piece of the sky shaped like a stop sign had fallen on his head when he was sitting under the big Oak tree in the town square. However, he's unable to find the piece. His father, Buck Cluck, assumes that this "piece of sky" was just an acorn that had fallen off the tree and had hit him on the head. Chicken Little becomes the laughing stock of the town………………………………….

With regards – S. Sampathkumar.

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