In the 21st century, scientists who study the heavens can call upon an array of Earth- and space-based observatories to advance our knowledge of the cosmos – and all of us are beneficiaries.  Think of the spectacular images and publicly available information we can peruse by simply following a few links on our computers to Web sites maintained by government agencies, academic and research institutions, the mainstream astronomy press, and blogs like SpaceRip.com.

With all the well-earned attention that space telescopes such as Hubble and ground-based facilities such as the European Southern Observatory receive, it is understandable that many non-professional stargazers might have overlooked a third type of platform for astronomical inquiry:  the airborne observatory.

Up, Up and Away

Long before it was possible to position astronomical instruments in space, astronomers sought ways to break through the limitations inherent to ground-based telescopes.  They were especially interested in developing telescopes that could capture the full spectrum of light radiation, not just the wavelengths that can penetrate Earth’s atmosphere.

Two means of accomplishing the goal were balloons and rockets, but both have significant limitations of their own.  Balloons are reusable, can rise to very high altitudes, and can stay up there for long periods, but they drift with the winds and can too easily wind up in unintended places.  Rockets can fly even higher, but their missions are extremely costly one-offs and of very short duration.

NASA's super pressure balloon high above Antarctica seen through telescope lens. (Credit: Columbia Scientific Balloon Facility)

Flying the Friendly Skies

The third option, of course, is airplanes.  In 1965, NASA began flying a fleet of specially converted jets on astronomical missions.  The aircraft were far more versatile and adaptive than balloons or rockets, carried astronomers on board, and could be upgraded and replaced by successive generations of platforms.

The Galileo Observatory's modified Convair 990 aircraft.

The largest and most successful NASA plane of the time was a Convair 990 jetliner dubbed the Galileo Observatory.  Outfitted with infrared telescopes and other instruments, the Galileo jet helped advance our knowledge of the Solar System simply by getting astronomers and their tools a little closer to space.  Among its most notable discoveries was that the clouds of Venus are not made of water vapor.  The Galileo program came to a tragic end when the plane was destroyed in a mid-air collision, in 1973.

To replace Galileo, NASA modified a C-141 Starlifter cargo jet for infrared astronomy.  The Starlifter was much larger than its predecessor, which allowed for a heavier, more diverse payload of instruments.  The Kuiper Airborne Observatory (KAO) discovered the rings of Uranus, studied the origin and distribution of water in star-forming regions, and helped astronomers understand how heavy elements are created in supernovae, among many other important contributions.

The KAO's telescope peered through a door behind the C-141's cockpit. (Credit: NASA)

Bigger Is Better

Today, NASA partners with the German Aerospace Center to operate the Strategic Observatory for Infrared Astronomy (SOFIA) on a heavily modified Boeing 747SP, which features a large door in the fuselage that can be opened in flight.  Behind the door is a 100-inch telescope dish that currently uses eight scientific instruments to study the Universe at infrared wavelengths.  The instruments can be readily switched-out for new state-of-the-art technologies as they are developed, giving SOFIA unparalleled flexibility for future airborne missions.

SOFIA's 100-inch infrared telescope in the too-bright light of day. (Credit: NASA)

NASA has just announced plans for SOFIA’s Science Cycle 5.  During this program, which will commence in February 2017 and run through January 2018, the observatory will devote hundreds of hours to a set of cutting-edge astronomical studies, including:

  • Follow-up of the Hubble Space Telescope’s recent discovery of water plumes rising from Jupiter’s moon Europa;
  • Observations of Neptune’s moon Triton;
  • The search for previously unseen molecules in the Orion star-forming region, especially organic compounds, water, ethylene, ethane, and acetylene;
  • Study of the region around the Milky Way’s nucleus, including readings on the supermassive black hole thought to lurk at the galaxy’s center;
  • Detection of comets and asteroids orbiting other stars in our galaxy.
A SOFIA infrared image of the W43 star-forming region about 20,000 light years from Earth. (Credit: NASA/JPL-Caltech/2MASS)

Astronomy’s international triad of land-, air-, and space-based observatories are crucial to our understanding of the mysteries and wonders of the Universe.  Perhaps one day, far in the future, they will be supplemented by telescopes based on planets or their moons elsewhere in the Solar System.  In a time of great uncertainty here on Earth, at least we can dream peacefully of that kind of progress.