NASA begins testing of new spectrograph on SOFIA observatory

June 3, 2014
EXES, the Echelon-Cross-Echelle Spectrograph, made its first light flight on April 7, 2014. The instrument is a mid-infrared spectrograph and is shown mounted to SOFIA's telescope. Credit: NASA/SOFIA/EXES/Mathew Richter

( —Astronomers are eagerly waiting to begin use of a new instrument to study celestial objects: a high-resolution, mid-infrared spectrograph mounted on NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA), the world's largest flying telescope.

This new instrument, the Echelon-Cross-Echelle Spectrograph (EXES), can separate wavelengths of light to a precision of one part in 100,000. At the core of EXES is an approximately 3-foot (1 meter) bar of aluminum called an echelon grating, carefully machined to act as 130 separate mirrors that split light from the telescope into an infrared "rainbow."

SOFIA is a heavily modified Boeing 747 Special Performance jetliner that carries a telescope with an effective diameter of about 8-feet (2.5-meters) at altitudes of 39,000 to 45,000 feet (12 to 14 km), above more than 99 percent of Earth's . Lower in the atmosphere, at altitudes associated with most ground-based observatories, water vapor obscures much of what can be learned when viewed in the infrared spectrum.

"The combination of EXES's high spectral resolution and SOFIA's access to infrared radiation from space provides an unprecedented ability to study at wavelengths unavailable from ground-based telescopes," said Pamela Marcum, a program scientist at the SOFIA Science Center and Program Office in Moffett Field, California. "EXES on SOFIA will provide data that cannot be obtained by any other astronomical facility on the ground or in space, including all past, present or those observatories now under development."

EXES successfully carried out its first two flights on SOFIA on the nights of April 7 and 9, according to Matthew Richter, leader of the team that is developing the instrument at the University of California, Davis, Physics Department. EXES is a collaboration between U.C. Davis and NASA's Ames Research Center in Moffett Field.

"During the two flights, EXES made observations to investigate and characterize the instrument's performance. All the main goals of these observations were successful, although further commissioning flights are required to test EXES in all of its modes," said Richter.

On the first commissioning flight, EXES observed emissions from Jupiter's atmosphere in two molecular hydrogen lines. These observations will be used to understand how gas rises from deep in Jupiter's interior and mixes into the planet's upper atmosphere.

During the second commissioning flight, EXES observed a young, massive star in the constellation Cygnus that is still embedded in its natal cocoon. The star, known as AFGL 2591, warms up the surrounding interstellar dust and causes ice coatings on the dust to evaporate. The warmed dust provides an excellent background infrared "lamp" to probe the chemical make-up of the intervening gas.

New stars and planets are forming from that material through processes similar to the ones that made the sun and Earth. These observations are designed to study water vapor around the protostar, and demonstrate that EXES can detect absorption from the lowest energy level of water molecules despite interference from from Earth's atmosphere.

"Of the observations obtained during the instrument's first flights, only one can be done from the ground, albeit with some difficulty, and the others are impossible from even the best ground-based telescope sites because the water in Earth's atmosphere is opaque at these wavelengths," Richter said. "While space observatories are above Earth's atmosphere, the massive optical equipment required to separate the light as finely as EXES does – EXES weighs almost 1,000 pounds – would be a challenge to launch into space. In these observations, the spectral features we are studying are narrow, and finely dividing the to detect them is exactly what EXES was designed to do."

Explore further: GREAT spectrometer readied for flight on SOFIA

Related Stories

GREAT spectrometer readied for flight on SOFIA

March 31, 2011

( -- Scientists recently completed a series of nighttime, ground-based testing of the German Receiver for Astronomy at Terahertz Frequencies, or GREAT, spectrometer in preparation for a series of astronomical ...

NASA's airborne observatory views star forming region W40

November 22, 2011

A new image from NASA's Stratospheric Observatory for Infrared Astronomy, or SOFIA, provides the highest resolution mid-infrared image taken to date of the massive star formation region in our galaxy known as W40.

SOFIA peers in to the heart of the Orion nebula

December 20, 2011

( -- A new image from NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) shows a complex distribution of interstellar dust and stars in the Orion nebula. Interstellar dust, composed mostly of ...

NASA selects science instrument upgrade for flying observatory

April 18, 2012

NASA has selected a science instrument upgrade to the Stratospheric Observatory for Infrared Astronomy (SOFIA) airborne observatory. The instrument, the High-resolution Airborne Wideband Camera (HAWC), will provide a sensitive, ...

SOFIA set to begin cycle two astronomy observations

November 6, 2013

NASA, the German Aerospace Center (DLR), the SOFIA Science Center, and the German SOFIA Institute (DSI) have announced the selection of 51 investigations to study the universe using the Stratospheric Observatory for Infrared ...

Recommended for you

The hottest white dwarf in the Galaxy

November 25, 2015

Astronomers at the Universities of Tübingen and Potsdam have identified the hottest white dwarf ever discovered in our Galaxy. With a temperature of 250,000 degrees Celsius, this dying star at the outskirts of the Milky ...

Hubble captures a galactic waltz

November 26, 2015

This curious galaxy—only known by the seemingly random jumble of letters and numbers 2MASX J16270254+4328340—has been captured by the NASA/ESA Hubble Space Telescope dancing the crazed dance of a galactic merger. The ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.