Sensor Module
The sensor module, developed at Langley Research
Center, houses all GIFTS mission components. This module includes
the imager, a guidance system, cryogenics to protect the module
from potentially damaging events, and a mechanism to synchronize
and package the measurement data.
The GIFTS imager incorporates key elements
of an optical remote sensing system: the large area format focal
plane detector arrays (LFPA) combined with the Fourier Transform
spectrometer (FTS). The LFPA are groups of detectors "tuned"
to specific infrared and visible wavelengths and will provide the
nearly continuous observation of large geographical areas with high,
horizontal resolution.
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The FTS is a spectrometer that "focuses"
photon energy onto the LFPA and looks at different wavelengths of
radiant energy, or the spectrum, to make measurements with an algorithm
tool, the Fourier Transform, for solving physical problems. The
GIFTS FTS is based on a Michelson interferometer, the basic concept
of which was first developed in the late 1800s by Albert Michelson,
a Polish-born American physicist.
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This
imaging FTS is capable of producing an image of the atmosphere that
can be examined at many altitudes. And, if scientists want to see
the amount of water vapor in a given area, the instrument's data
can be used to analyze only the water vapor, to the exclusion of
all other variables. A key to reducing risk in FTS instruments flown
on future Earth science missions is to validate all of these advanced
technologies in the laboratory of space that can't be replicated
in Earth-bound labs.
The self-contained pointing and control system,
called "Star Tracker," measures GIFTS orientation with
respect to the stars. Star Tracker will insure that scientists know
precisely where the instrument is pointed when image and sounding
data is taken.
The sensor module's high-speed, ultra-low-power
signal processor will provide rapid downlink and interpretation
of the data. These techniques and equipment are designed to reduce
downlink requirements while maintaining accurate science information.
The sensor module will be cryogenically cooled,
increasing tensile strength and extending wear resistance.
Control Module
The sensor module's high-speed, ultra-low-power signal processor
will provide rapid downlink and interpretation of the data. These techniques
and equipment are designed to reduce downlink requirements while
maintaining accurate science information. The sensor module will
be cryogenically cooled, increasing tensile strength and extending
wear resistance.
When
the data-acquisition command is received through the spacecraft
command interface, the control module calculates the initial pointing
mirror pattern and positions and transfers data acquisition parameters,
such as spectral resolution, to the sensor module. The sensor module
then initializes these parameters, positions the pointing mirror
and begins scanning and acquiring data. Once the data is acquired,
it is transferred back to the control module. At completion of the
transfer the control module sends a new target to the sensor module.
These steps are repeated until the region of the Earth's surface
that is being studied (local, regional, global) has been covered.
As near-real-time data is collected, GIFTS control module will use
new and improved data compression (shrinking) techniques before
downloading it to ground stations.
Overview | A Joint Mission | The GIFTS Instrument | Instrument Technology Facts
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