Section 10 EO C440.08 – WATCH BLAST! (BALLOON-BORNE LARGE APERTURE SUB-MILLIMETRE TELESCOPE)

Astrophysicists are interested in learning more about how the earliest galaxies and stars were formed. However, these objects are often hidden by gas and dust so they cannot be seen in visible light. Fortunately, star births are fiery events. Heat from the newborn stars warms the surrounding dust, which then emits sub-millimetre radiation—a form of infrared electromagnetic radiation close to visible light. Infrared radiation, having wavelengths that are longer than visible light, can pass through dusty regions of space without being scattered. In order to detect much of this radiation, however, sub-millimetre telescopes must be built.

Water vapour in the Earth's atmosphere absorbs radiation across large parts of the infrared and sub-millimetre wavebands, making ground-based observations at some of these wavelengths impossible. Limited observations can be made from high-altitude balloons, such as BLAST, but space-based observatories such as the European Space Agency's Herschel are the only truly satisfactory solution to this problem.

Show the cadets the slide of Figure A-1 located at Attachment A.

When astronomers look further out into space, they are actually looking further back in time. Light travels incredibly fast and seems instantaneous at short distances on the Earth, but light from distant galaxies takes millions or even billions of years to reach Earth. The further out one looks into space, the longer that light has travelled. Observers are literally seeing the light of events that happened in the remote past. Looking further and further back, astronomers can develop a timeline for the evolution of the universe.

Show the cadets the slide of Figure A-2 located at Attachment A.

Learn more about infrared astronomy in The Cosmic Classroom: The Infrared Universe at http://coolcosmos.ipac.caltech.edu/

Key words: Bolometers. The sensors that detect sub-millimetre light. Gondola. The large metal structure that holds the telescope, motors, and computers. Payload. Anything dangling from the balloon. Star cameras. Cameras that BLAST uses to orient itself in the sky.

Large unmanned helium balloons have long provided NASA with an inexpensive means to place payloads into a near-space environment. The unique capabilities of this program are crucial for the development of new technologies and payloads for NASA's space flight missions. They also offer essential training for the next generation of scientists, as can be seen in BLAST! As well, many important scientific observations are made from long-duration balloon flights.

BLAST used the Sun’s energy to power instruments and took advantage of the Sun’s continuous presence during the summers at the North and South Poles. Flying only in constant daylight, BLAST was ensured a steady source of power and a flight at a stable altitude. If the Sun were to set during the flight, the helium in a balloon would cool and it would drop to a lower altitude. At sunrise, the helium would heat and the balloon would rise.

BLAST needed a way to orient itself and point the telescope in the right direction. Although it had an onboard Global Positioning System (GPS), BLAST relied on the stars for its navigation. On top of the main mirror are two star cameras (long white tubes). These cameras took pictures of stars whose positions in the sky are well known. BLAST’s computers then analyzed these reference points and, through a series of motors and gyroscopes, adjusted its orientation accordingly.

When landing, a remote-controlled system separated BLAST from the balloon and a parachute opened to help slow the telescope’s descent. It took about 45 minutes for BLAST to reach the ground. The parachute was designed to then detach itself from the gondola. The precious hard drive, containing all of the data, had to be physically recovered. Recovery could be very difficult, depending on where BLAST landed.

In 2005, BLAST flew from Sweden to Canada while making moderately successful observations.

Show the cadets the slide of Figure B-1 located at Attachment B.

In 2006, BLAST flew over Antarctica while making very successful observations.

Show the cadets the slide of Figure B-2 located at Attachment B.