TopHat (Balloon)
Encyclopedia
TopHat was a scientific experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...

 launched from McMurdo Station
McMurdo Station
McMurdo Station is a U.S. Antarctic research center located on the southern tip of Ross Island, which is in the New Zealand-claimed Ross Dependency on the shore of McMurdo Sound in Antarctica. It is operated by the United States through the United States Antarctic Program, a branch of the National...

 in January 2001 to measure the cosmic radiation
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

 produced 300,000 years after the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...

. The balloon was launched on January 2, 2001 and proceeded to fly for 644 hours over the continent of Antarctica before landing on January 31, 2001. The balloon flew over the continent 38 kilometers (125,000 ft) above the ground, giving the telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

 the ability to see the entire continent each day. Its results took over a year to analyze. The working payload was shut down on January 10, 2001 after sufficient measurements were made and the balloon simply circled the continent until it was safe to land, except that the landing missed the targeted ice shelf by around one half mile, and while the discs containing the information were recovered safely using a Twin Otter
De Havilland Canada DHC-6 Twin Otter
The DHC-6 Twin Otter is a Canadian 19-passenger STOL utility aircraft developed by de Havilland Canada and currently produced by Viking Air. The aircraft's fixed tricycle undercarriage, STOL abilities and high rate of climb have made it a successful cargo, regional passenger airliner and MEDEVAC...

, the gondola itself had not been recovered by August 2001.

The telescope was called part of the "Submillileter Astrophysics Experiment" for Dr. Edward Cheng of NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

’s Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...

. It took 6 years to build and in the end weighed 500 pounds (230 kg). It was built in association with NASA’s Goddard Space Flight Center, the University of Chicago
University of Chicago
The University of Chicago is a private research university in Chicago, Illinois, USA. It was founded by the American Baptist Education Society with a donation from oil magnate and philanthropist John D. Rockefeller and incorporated in 1890...

, the University of Wisconsin–Madison
University of Wisconsin–Madison
The University of Wisconsin–Madison is a public research university located in Madison, Wisconsin, United States. Founded in 1848, UW–Madison is the flagship campus of the University of Wisconsin System. It became a land-grant institution in 1866...

 and the Danish Space Research Institute
Danish Space Research Institute
Danish Space Research Institute was the space agency of Denmark from 1966 to 2005. It was a Danish sector research institute formed in 1966 under the Danish Ministry for Education and Research, later the Danish Ministry of Science Technology and Innovation...

. TopHat experiment was the first of its kind in that it placed the telescope on top of the actual balloon, where it rotated at a constant rate around a vertical axis; the first of its kind to do so and covered a 48 degree window of the sky. The placement allowed for the telescope to gain a unique view of the sky, with no obstructions and no light pollution being reflected from the ground. The balloon itself took up 29.47 cubic feet (0.834 m3) of space.

TopHat was built in part to follow up the observations of the BOOMERanG experiment
BOOMERanG experiment
The BOOMERanG experiment measured the cosmic microwave background radiation of a part of the sky during three sub-orbital balloon flights. It was the first experiment to make large, high fidelity images of the CMB temperature anisotropies...

which also studied the cosmic background radiation. TopHat was attempting to detect the clumpiness of matter, how much matter was in the universe, how the universe was expanding, and if it was indeed flat as had been observed by BOOMERANG. Around 300,000 years ago, the temperature of the universe cooled enough so that hydrogen atoms formed and the photons of energy (the radiation of energy from the explosion) were able to escape and travel indefinitely. This oldest form of radiation has a temperature of 2.73 K and is uniform except for one part in 100,000 where the temperature is slightly different. The patchiness of matter indicates the earliest structures being formed in the universe and TopHat was designed to detect this patchiness on an extremely small scale.
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