Northrop Grumman (NG) is developing a photonic waveguide-based imaging spectrometer that promises to dramatically reduce instrument size, weight and power and enable image acquisition in modes not possible with current hyperspectral imagers (HSIs). The objective of our current effort is to develop this novel hyperspectral technology for eventual application to the NASA Sustainable Land Imaging (SLI) mission. For more than 40 years the Landsat program has provided the Earth science community with highly accurate global multispectral imagery (MSI) to monitor our planet and ecosystems. Through extensive modeling and simulation NG has demonstrated that a versatile HSI sensor can meet the goals for a sustainable land imager. Our photonic spectrometer represents a step forward for hyperspectral imaging, providing a path to an extremely compact instrument that will provide fully co-registered spectral and spatial data across the instrument’s field of view.
We present parallel algorithms for fast subpixel detection of targets in hyperspectral imagery produced by our
Hyperspectral Airborne Tactical Instrument (HATI-2500). The HATI-2500 hyperspectral imaging system has a
blue-enhanced visible-near-IR (VNIR) and a full short-wave IR (SWIR) range response from 400 to 2500 nm.
It has an industry-leading spectral resolution that ranges from 6 nm down to 1.5 nm in the VNIR region.
The parallel detection algorithm selected for processing the hyperspectral data cubes is based on the adaptive
coherence/cosine estimator (ACE). The ACE detector is a robust detector that is built upon the theory of generalized
likelihood ratio testing (GLRT) in implementing the matched subspace detector to unknown parameters
such as the noise covariance matrix. Subspace detectors involve projection transformations whose matrices can
be efficiently manipulated through multithreaded massively parallel processors on modern graphics processing
units (GPU). The GPU kernels developed in this work are based on the CUDA computing architecture. We
constrain the detection problem to a model with known target spectral features and unstructured background.
The processing includes the following steps: 1) scale and offset applied to convert the data from digital numbers
to radiance values, 2) update the background inverse covariance estimate in a line-by-line manner, and 3) apply
the ACE detector for each pixel for binary hypothesis testing. As expected, the algorithm is extremely effective
for homogeneous background, such as open desert areas; and less effective in mixed spectral regions, such as
those over urban areas. The processing rate is shown to be faster than the maximum frame rate of the camera
(100 Hz) with a comfortable margin.
Northrop Grumman Aerospace Systems (NGAS) has a long
legacy developing and fielding hyperspectral sensors,
including airborne and space based systems covering the
visible through Long Wave Infrared (LWIR) wavelength
ranges. Most recently NGAS has developed the
Hyperspectral Airborne Terrestrial Instrument (HATI) family
of hyperspectral sensors, which are compact airborne
hyperspectral imagers designed to fly on a variety of
platforms and be integrated with other sensors in NGAS's
instrument suite. The current sensor under development is
the HATI-2500, a full range Visible Near Infrared (VNIR)
through Short Wave Infrared (SWIR) instrument covering the
0.4 - 2.5 micron wavelength range with high spectral
resolution (3nm). The system includes a framing camera
integrated with a GPS/INS to provide high-resolution
multispectral imagery and precision geolocation. Its compact
size and flexible acquisition parameters allow HATI-2500 to
be integrated on a large variety of aerial platforms. This
paper describes the HATI-2500 sensor and subsystems and its
expected performance specifications.
Northrop Grumman Aerospace Systems (NGAS) has developed the Hyperspectral Airborne Tactical Instrument (HATI), a compact
airborne hyperspectral imager designed to fly on a variety of platforms and to be integrated with other sensors in the NGAS
instrument suite. HATI has taken part in a variety of missions and flown in conjunction with other NGAS airborne sensors including
the recently-developed NGAS 3-D flash ladar system to demonstrate a multi-sensor data fusion approach. HATI is a push-broom
sensor which gathers information in the 400 nm to 1700 nm wavelength range. Its compact size allows HATI to be mounted on
commercial-of-the-shelf (COTS) aerial photography stabilization platforms and on a large variety of aerial platforms. In its most
recent flight season, the HATI sensor was used to gather data for applications including remote classification of vegetation, forests,
and man-made materials. The HATI instrument has undergone laboratory and in-situ performance validation and radiometric
calibration. This paper describes the HATI sensor and recent data collection campaigns.
Northrop Grumman Space Technology (NGST) completed building and testing its Long Wave Hyperspectral Imaging Spectrometer (LWHIS) at the end of 2003. The instrument is a pushbroom sensor that operates in the 8 to 12.5 micron band, providing up to 256 contiguous spectral channels with 35 nm of dispersion per pixel. LWHIS was designed to operate from both ground and airborne platforms and to meet rigorous requirements for instrument performance and calibration. Since its completion, the instrument has undergone laboratory performance validation and has taken part in a number of ground and airborne imaging experiments. These experiments have led to system upgrades which have significantly improved the instrument's performance. This paper will describe the current LWHIS system, including upgrades, data correction and calibration processes, data processing rates, and demonstrate system performance using gas release experiments conducted at ground level.
The TRW Imaging Spectrometer III (TRWIS III) airborne hyperspectral sensor collects imagery in 384 contiguous spectral channels covering the 400 nm to 2450 nm wavelength range. TRWIS III has been used to gather data for a number of remote sensing applications including classification of desert vegetation, forest species, and man-made materials. Analysis has also been performed on TRWIS III agricultural images. This paper will describe the subspace projection technique that was used to process agricultural imagery. An example will be shown in which data dimensionality is reduced by projecting test data onto the space spanned by training data. A minimum Mahalanobis distance measure from the means of the training data class clusters is used as the pixel classification criterion.
The TRW Imaging Spectrometer III airborne hyperspectral imager was competed in 1996. The spectrometer is a pushbroom sensor that gathers information in 384 contiguous spectral channels covering the 400nm to 2450nm wavelength range. TRWIS III was designed to fly on many different aircraft platforms and to meet critical performance requirements for image quality, co-registration of spectral samples, spectral calibration, noise and radiometric accuracy. Along with its first several seasons of operational demonstrations, the instrument has undergone laboratory performance validation, radiometric calibration, and system upgrades. This paper will describe the current TRWIS III system, the data calibration and correction system, and the instrument's applications to remote sensing.
The tremendous potential for hyperspectral imagery as a remote sensing tool has driven the development of TRW's TRWIS III hyperspectral imager. This instrument provides 384 contiguous spectral channels at 5 nm to 6.25 nm spectral resolution covering the 400 nm to 2450 nm wavelength range. The spectra of each pixel in the scene are gathered simultaneously at signal to noise ratios of several hundred to one for typical Earth scenes. Designed to fly on a wide range of aircraft and with variable frame rate, the ground resolution can be varied from approximately 50 cm to 11 m depending on the aircraft altitude and speed. Meeting critical performance requirements for image quality, co- registration of spectral samples, spectral calibration, noise, and radiometric accuracy are important to the success of the instrument. TRWIS III performance has been validated and the instrument has been radiometrically calibrated using TRW's Multispectral Test Bed. This paper discusses the characterization and calibration process and results of the measurements. An example of results from a flight at the end of 1996 is included.