NASA’s QWIP-based Thermal Infrared Sensor to be integrated into
15 February 2012
A new satellite instrument made by the US National Aeronautics
and Space Administration (NASA) that uses gallium arsenide (GaAs)-based
quantum-well infrared photodetector (QWIP) technology has
arrived at Orbital Sciences Corp in Gilbert, AZ, USA, where it
will be integrated into the next Landsat satellite, the Landsat
Data Continuity Mission (LDCM).
Picture: Aleksandra Bogunovic reaches across the TIRS instrument
to affix the corners of a Multi-Layer Insulation blanket.
(Credit: NASA Goddard/Rebecca Roth).
The Thermal Infrared Sensor (TIRS) instrument will measure the
Earth’s temperature with technology that applies quantum physics
to detect heat. The engineering team at NASA’s Goddard Space
Flight Center in Greenbelt, MD completed TIRS on an accelerated
schedule, going from plans on paper to building the instrument
in an unprecedented 43 months. “That’s a full year ahead of a
typical schedule for a new space-borne instrument,” notes TIRS
instrument manager Betsy Forsbacka.
The achievement has been enabled by the use of detector arrays
that LDCM had on-hand, since Goddard played a major role in
developing the technology, says LDCM project scientist James
Irons. “TIRS will be the first time this technology is used in
space,” he adds.
TIRS uses QWIP devices to detect long wavelengths of light
emitted by the Earth with an intensity that depends on surface
temperature. The thermal infrared wavelengths are well beyond
the range of human vision and, while devices for thermal
infrared night ‘vision’ have long been available, QWIPs offer a
new lower-cost alternative to conventional infrared technology.
Also, QWIP arrays are designed for sensitivity to specific
The QWIP’s design operates on the principles of quantum
mechanics. GaAs chips trap electrons in an energy state ‘well’
until the electrons are elevated to a higher state by thermal
infrared light of a certain wavelength. The elevated electrons
create an electrical signal that can be read out and recorded to
create a digital image. The QWIPs that TIRS uses are sensitive
to two thermal infrared wavelength bands, helping it separate
the temperature of the Earth’s surface from that of the
TIRS was added to the satellite mission when it became clear
that state water resource managers rely on the highly accurate
measurements of Earth’s thermal energy obtained by NASA
satellites (such as LDCM’s predecessors Landsat 5 and Landsat 7)
to track how land and water are being used. “For example,
irrigated fields are cooler than those suffering from a lack of
moisture,” says TIRS thermal engineer Veronica Otero. With
nearly 80% of the fresh water in the Western USA being used to
irrigate crops, TIRS will become an invaluable tool for managing
water consumption, says Rick Allen, director of water resources
research at the University of Idaho, in Kimberly, ID.
LDCM is scheduled to launch in January 2013 from Vandenberg Air
Force Base in California. On board will be two instruments: TIRS
and the Operational Land Imager (OLI) imaging sensor built by
Ball Aerospace & Technologies Corp of Boulder, CO, which
collects data in the visible, near-infrared and short-wave
LDCM is the eighth satellite in the Landsat series, which began
in 1972 with the launch of Landsat 1, and extends the world’s
longest-running satellite program for global land observations.
Landsat is jointly managed by NASA and the US Department of the
Interior through the US Geological Survey (USGS, which preserves
a 40-year archive of Landsat images, with free distribution of
data over the Internet). Because of this freely available data
of more than 3 million current and archived images of Earth,
Landsat data is the basis for thousands of university research
papers, the foundation for commercial innovations like Google
Earth, and a cornerstone of US space cooperation with foreign
nations. More than 20 nations on six continents operate local
receiving stations for Landsat data.
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