Dr. Richard L. L. Lachance Profile

Dr. Richard L. L. Lachance

at Bluefield Technologies

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Publications (7)

Proceedings Article | 14 December 2016 Presentation

HATS (High Altitude Thermal Sounder): a passive sensor solution to 3D high-resolution mapping of upper atmosphere dynamics (Conference Presentation)

Larry Gordley, Benjamin Marshall, Richard Lachance

Proceedings Volume 10000, 100001D (2016) https://doi.org/10.1117/12.2242923

KEYWORDS: Modulation, Doppler effect, Sensors, Atmospheric sensing, Spectral resolution, Principal component analysis, Earth's atmosphere, Carbon dioxide, Passive sensors, Infrared sensors

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This presentation introduces a High Altitude Thermal Sensor (HATS) that has the potential to resolve the thermal structure of the upper atmosphere (cloud top to 100km) with both horizontal and vertical resolution of 5-7 km or better. This would allow the complete characterization of the wave structures that carry weather signature from the underlying atmosphere. Using a novel gas correlation technique, an extremely high-resolution spectral scan is accomplished by measuring a Doppler modulated signal as the atmospheric thermal scene passes through the HATS 2D FOV. This high spectral resolution, difficult to impossible to achieve with any other passive technique, enables the separation of radiation emanating at high altitudes from that emanating at low altitudes. A principal component analysis of these modulation signals then exposes the complete thermal structure of the upper atmosphere. We show that nadir sounding from low earth orbit, using various branches of CO2 emission in the 17 to 15 micron region, with sufficient spectral resolution and spectral measurement range, can distinguish thermal energy that peaks at various altitudes. By observing the up-welling atmospheric emission through a low pressure (Doppler broadened) gas cell, as the scene passes through our FOV, a modulation signal is created as the atmospheric emission lines are shifted through the spectral position of the gas cell absorption lines. The modulation signal is shown to be highly correlated to the emission coming from the spectral location of the gas cell lines relative to the atmospheric emission lines. This effectively produces a scan of the atmospheric emission with a Doppler line resolution. Similar to thermal sounding of the troposphere, a principal component analysis of the modulation signal can be used to produce an altitude resolved profile, given a reasonable a priori temperature profile. It is then shown that with the addition of a limb observation with one CO2 broadband channel (similar to methods employed with sensors like LIMS on Nimbus 7, HIRDLS on Aura, and SABER on TIMED), a limb temperature profile can be retrieved and used as the a priori profile, nearly eliminating uncertainty due to a priori inaccuracy. Feasibility studies and proposed instrument designs are presented. A tutorial for a similar technique proposed for measuring winds and temperature with limb observations can be found at http://www.gats-inc.com/future_missions.html

Proceedings Article | 19 September 2013 Paper

ACE-FTS on SCISAT: 10th year on-orbit anniversary

Richard Lachance, Henry Buijs, Marc-André Soucy

Proceedings Volume 8867, 88670J (2013) https://doi.org/10.1117/12.2024985

KEYWORDS: Interferometers, Space operations, Sensors, Satellites, Signal to noise ratio, Fourier transforms, Earth's atmosphere, Ozone, Mirrors, Infrared radiation

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The Atmospheric Chemistry Experiment (ACE) is a mission on-board the Canadian Space Agency’s (CSA) SCISAT-1. ACE is composed of a suite of instruments consisting of an infrared Fourier Transform Spectrometer (FTS) coupled with an auxiliary imager monitoring aerosols based on the extinction of solar radiation using two filtered detectors (visible and near infrared). A suntracker is also included to provide fine pointing during occultation. A second instrument, MAESTRO, is a spectrophotometer covering the near ultra-violet to the near infrared. In combination, the instrument payload covers the spectral range from 0.25 to 13.3 μm. The ACE mission came about from a need to better understand the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere, with particular emphasis on the Arctic region. Measurement of the vertical distribution of molecular species in these portions of the atmosphere permits elucidation of the key chemical and dynamical processes. The ACE-FTS measures the vertical distributions of trace gases as well as polar stratospheric clouds, aerosols, and temperature by a solar occultation technique from low earth orbit. By measuring solar radiation at high spectral resolution as it passes through different layers of the atmosphere, the absorption thus measured provides information on vertical profiles of atmospheric constituents, temperature, and pressure. Detailed and sensitive vertical distribution of trace gases help to better understand the chemical processes not only for ozone formation and destruction but also for other dynamic processes in the atmosphere. The ACE/SCISAT-1 satellite was successfully launched by NASA on August 12, 2003, and has been successfully operating since, now celebrating its 10^th year on-orbit anniversary. This paper presents a summary of the heritage and development history of the ACE-FTS instrument. Design challenges and solutions are related. The actual on-orbit performance is presented, and the health status of the instrument payload is discussed. Potential future follow-on missions are finally introduced.

Proceedings Article | 19 November 2012 Paper

PCW/PHEOS-WCA: quasi-geostationary Arctic measurements for weather, climate, and air quality from highly eccentric orbits

Richard Lachance, John McConnell, C. Tom McElroy, Norm O'Neill, Ray Nassar, Henry Buijs, Peyman Rahnama, Kaley Walker, Randall Martin, Chris Sioris, Louis Garand, Alexander Trichtchenko, Martin Bergeron

Proceedings Volume 8533, 85330O (2012) https://doi.org/10.1117/12.974795

KEYWORDS: Fourier transforms, Ultraviolet radiation, Aerosols, Carbon dioxide, Environmental sensing, Satellites, Imaging systems, Near infrared, Climatology, Spatial resolution

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Proceedings Article | 1 November 2012 Paper

Infrared measurements throughout polar night using two AERIs in the Arctic

Z. Mariani, K. Strong, M. Wolff, P. Rowe, V. Walden, P. Fogal, T. Duck, G. Lesins, D. Turner, C. Cox, E. Eloranta, J. Drummond, C. Roy, R. Lachance, D. Hudak, I. Lindenmaier

Proceedings Volume 8534, 85340H (2012) https://doi.org/10.1117/12.974683

KEYWORDS: Clouds, Calibration, Black bodies, Infrared radiation, Gases, Interferometers, Data acquisition, Sensors, Crystals, Spectroscopy

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Proceedings Article | 17 February 2003 Paper

Fiber Bragg gratings and chromatic dispersion

Richard Lachance, Yves Painchaud, Aidan Doyle

Proceedings Volume 4833, (2003) https://doi.org/10.1117/12.473966

KEYWORDS: Dispersion, Fiber Bragg gratings, Reflectivity, Wavelength division multiplexing, Picosecond phenomena, Optical networks, Optical filters, Modulation, Apodization, Telecommunications

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Proceedings Article | 6 August 1998 Paper

Gaseous emanation detection algorithm using a Fourier transform interferometer operating in differential mode

Richard Lachance, Jean-Marc Theriault, Claude Lafond, Andre Villemaire

Proceedings Volume 3383, (1998) https://doi.org/10.1117/12.317642

KEYWORDS: Detection and tracking algorithms, Interferometers, Sensors, Signal processing, Fourier transforms, Algorithm development, Gases, Absorbance, Remote sensing, Atmospheric sensing

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Proceedings Article | 23 July 1997 Paper

Radiometric calibration of FT-IR remote sensing instrument

Andre Villemaire, Martin Chamberland, Jean Giroux, Richard Lachance, Jean-Marc Theriault

Proceedings Volume 3082, (1997) https://doi.org/10.1117/12.280921

KEYWORDS: Calibration, Black bodies, Sensors, Temperature metrology, FT-IR spectroscopy, Remote sensing, Interferometers, Computed tomography, Spectroscopy, Beam splitters

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