Exelis Inc.

Grant Matthews

A method of calibrating a spectrometer, while orbiting the Earth, includes the steps of (a) determining a period of time in which the Moon is within a field of view (FOV) of the spectrometer and (b) stopping the FOV of the spectrometer during this period of time. During this period of time, multiple 'free views' of the Moon are available, in which lunar IR intensities may be received by the spectrometer that are comparable to intensity levels obtained from an internal calibration test (ICT) on a satellite. The method measures the IR radiance from the Moon during this period of time. After filtering the lunar IR radiances by an integral function, the spectrometer is calibrated using the 'free views' as a benchmark.

Method for using the moon's thermal output to track calibration drifts in instruments on board satellites observing the earth

A program is implemented on a processor for executing the following steps: receiving images of a scene comprising successive frames from a camera, each frame including an array of pixels; filtering intensities of the array of pixels in a respective frame by using a Bessel Filter to compute a constant value for the respective frame; and summing a predetermined number of respective frames from the camera to determine rapid motion in the scene. The filter includes a Bessel filter, which is an n-pole recursive digital filter, where n is a positive integer.

Real-time recursive filter to identify weather events using traffic CCTV video

A system for correcting infrared (IR) radiances includes an imager for receiving IR radiances and outputting intensity data corresponding to pixels in the imager. Also included is a stray light estimator for receiving the intensity data and estimating stray light in the intensity data. The stray light estimator includes a Bessel filter for low pass filtering the estimated stray light and providing corrected intensity data as an output to a user. The Bessel filter is an n-pole recursive digital filter, which is expressed as a ratio between (a) an (n&#x2212;1) order polynomial of a complex number and (b) an n order polynomial of a complex number, where n is a positive integer. The Bessel filter includes an infinite response curve, in which the response curve monotonically decreases in amplitude as a function of frequency per pixels.

Recursive Bessel filter for stray light corrections in an imager

A system for calibrating a broadband detector includes a first narrowband telescope for viewing a celestial body, and an earth viewing telescope. The broadband detector is selectively coupled to the first narrowband telescope or the earth viewing telescope. A first narrowband filter is selectively inserted in an optical path of the first narrowband telescope, or the earth viewing telescope. A processor is configured to calibrate the broadband detector based on viewing the celestial body with the first narrowband telescope or the earth viewing telescope, and selectively inserting the first narrowband filter in the optical path. The first narrowband telescope includes a first narrowband filter inside its optical train. The first narrowband filter, which is selectively inserted in the optical path, is spectrally similar to the first narrowband filter inside the optical train of the first narrowband telescope. In addition, a second narrowband telescope, which receives a different wavelength from the first narrowband telescope includes a second narrowband filter inside its optical train. In addition, a second narrowband filter, which is selectively inserted in the optical path of the second narrowband telescope, is spectrally similar to the second narrowband filter inside the optical train of the second narrowband telescope. By using the first and second narrowband telescopes and the first and second narrowband filters, the broadband detector may be calibrated at two different wavelengths.

Narrowband solar calibration system for a radiometric system

A system assesses a column of gas in an atmosphere. The system includes an optical transmitter for transmitting (a) an online signal tuned to an online wavelength of gas, (b) an offline signal tuned to an offline wavelength of the gas, and (c) an optical signal for providing altimetry data. A modulator is included for modulating the online signal with a first stepped chirp waveform and modulating the offline signal with a second stepped chirp waveform. A processor assesses the column of gas, after receiving a returned online signal, a returned offline signal and a returned optical signal. A lock-in amplifier is included for (a) multiplying a returned signal with the first stepped chirp waveform to obtain a detected online signal, and (b) multiplying the returned signal with the second stepped chirp waveform to obtain a detected offline signal. The processor is configured to remove ground reflections from the optical signal to obtain scattered noise, and assess the column of gas based on the scattered noise. The processor is also configured to (a) multiply an estimated returned online signal with the first stepped chirp waveform to obtain a simulated cloud only online signal, and (b) multiply an estimated returned offline signal with the second stepped chirp waveform to obtain a simulated cloud only offline signal. In addition, the processor is configured to assess the column of gas by performing regression between the detected online and offline signals and the simulated online and offline signals.

Stepped chirp lidar system and method

A method for calibrating a spectrometer, while orbiting a celestial body, includes the steps of: (a) obtaining an estimate of radiance emanating from the celestial body; (b) raster scanning the celestial body using the spectrometer; (c) measuring filtered radiance of the celestial body based on step (b); and (d) determining gain of the spectrometer using steps (a) and (c). A calibrated spectrometer of the present invention is based on the determined gain of step (d). The method includes the step of: (e) raster scanning another celestial body to determine the albedo radiance of the other celestial body, after determining gain of the spectrometer in step (d). The celestial body may be the moon and the other celestial body may be the Earth.

Method of calibrating earth, lunar and solar spectrometers

A system for calibrating a spectrometer includes wide field-of-view (WFOV) optics providing a first light path to a WFOV spectrometer, and narrow field-of-view (NFOV) optics providing a second light path to a NFOV spectrometer. A de-focusing optic is selectively positioned in the first or second light paths. A scan controller selectively controls the WFOV or NFOV optics to scan a celestial body. A processor is configured to calibrate the de-focusing optic, while the WFOV optics scan the celestial body. First, the WFOV optics scan the celestial body without the de-focusing optic positioned in the first light path. Second, the WFOV optics scan the celestial body with the de-focusing optic positioned in the first light path. Next, the processor calibrates the NFOV spectrometer, while the NFOV optics and the de-focusing optic scan the celestial body. After the NFOV spectrometer is calibrated, the NFOV spectrometer may be used to measure the albedo of the earth.

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Fort Wayne, IN, United States of America

Grant Matthews