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GCSO2-1 Gas Camera
The Resonance GCSO2-1 is a UV-sensitive camera that compares images in two spectral bands to produce concentration maps of SO2 plumes. This method is based on differential optical absorption spectroscopy (DOAS) for remote sensing of atmospheric gases (Refs 1-13).  A unique feature of the GCSO2-1 is that it simultaneously captures two images of the target plume in bands centered on 310 and 320 nm with only one CMOS UV camera. Offsets due to changes between two imaging chips or moving filters are eliminated. Another unique feature is the use of a 3- mirror system which mirrors the two images about the optical axis of the camera.   This configuration when combined with Resonance’s powerful software eliminates the imbalances caused by distortion and edge dimming.   Calibration across the entire field is obtained by use of a PC- controlled SO2 gas cell wheel.  Field tests on volcanoes and smelter stacks have demonstrated that the concentration maps from GCSO2-1 are highly specific to SO2 and are insensitive to changes in the spectrum of daylight due to solar elevation.  The camera is delivered as a complete system ready to observe volcanoes or industrial stacks right out of the box.
Gas Camera at Aso in March 2016. Insert image shows SO2 in parts per million x metres
Features Produces quantitative images of SO2 in plumes from volcanoes and stacks that can be used to determine SO2-mass fluxes in tonnes per day Captures simultaneous images at 310 and 320 nm Single UV lens for image stability Single detector to eliminate drift between 2 detectors Mirrors used to cancel pincushion and barrel distortion Calibration with COSPEC SO2 cells Automatic dark subtraction Uses Ratio-of-Ratios technique for calibrated ppm-m image map Alignment easily adjusted in field Ethernet for crash-proof operation with laptop Operates off of external battery pack, car battery or AC outlet Rainproof enclosure Camera with laptop, batteries and tripod weighs less than 10kg Can be backpacked to remote loacations and operated for >6 hours Laptop with high-brightness screen Batteries for >6 hours continuous operation are allowable in carry-on luggage
Resonance Gas Camera at Unzen, March 2016
Resonance Gas Camera at Sakurajima, March 2016
Resonance Gas Camera image of SO2 at Vale Super Stack, Sudbury Ontario
Quantitative profile normal to plume velocity
SO2 captured under good conditions at Sakurajima on March 24, 2016.  Four time lapse images of SO2 45 seconds apart.
GCSWU_072616 A1 Software Features (alpha version released July 26, 2016): Recording time lapse SO2 image data:   Time lapse data stored in an Excel and Matlab compatible format for later analysis and presentation.  This data will facilitate later refined analysis of plume dynamics for velocity determination using DW-CWT or Farneback algorithms. Raw data capture:  Recording of Raw Reference, Dark and Signal frames as aids for future data analysis Alignment cursors:  Symmetric cursors to allow quick fine tuning optical alignment. Filter correction:  Corrects for transmission profile shifts in Bandpass filters caused by variation of field angle with correction matrices derived from frames taken through gas cells. Scan box integration:  Collects Profile data PPM-M vs. x or y in N user-defined boxes.  This time-stamped data is stored in a matrix with meta data for later analysis. Profile display and capture:   Profiles are displayed as a function of distance and saved. Scan box averages display and capture:  This integrated profile data is displayed a time series and saved. Real time plume flux estimates:  Uses cross-correlation plume velocity measurements and plume profiles to produce approximate SO2 fluxes in real-time.
W. H. Morrow, “Filter Correlation Spectrometers For Remote Sensing Of Tropospheric Gases,” Ph.D. Dissertation, York University, Toronto, ON, Canada, 2002. W. H. Morrow, R. W. Nicholls, J. Stix,  "Remote Sensing of Volcanic Plumes of Orbit", Geological Society of America, 97 Cordilleran Section Meeting, Kailua-Kona, Hawaii, May 21-23 1997 No. 16333 W. H. Morrow, J. Stix, R.W. Nicholls,  "Infrared Remote Sensing of Volcanic Gas Using Ground-Based And Satellite-Based Non-Dispersive Gas Correlation Radiometry", IAVCEI Commission on the Chemistry of Volcanic Gases, 6th Field Workshop, Kilauea Volcano Hawaii, May 16-20, 1997 W. H. Morrow, "MicroMAPS -a Lower Cost Orbital Remote Sensor for the Detection of CO and N2O", SPIE Proceedings Volume 2553 paper 51, Infrared Space borne Remote Sensing III, San Diego CA., Volume 25, 53, pp 116-125 (1995). 5.     W. H. Morrow, G. Walberg, G. K. Lee, "MicroMAPS: A Micro-controller‑Based Sensor For Measuring Carbon Monoxide In The Atmosphere", Geological Society of America, 97 Cordilleran Section Meeting, No. 16328, Kailua‑Kona, Hawaii, May 21‑23 (1997)   6.     G. D. Walberg,, W. H. Morrow, J. Stix, Global Monitoring of SO2 from a Small Low-Cost Satellite, Published by AIAA, Copyright North Carolina State University (1998). 7.     Morrow W. H., Nicholls R. W., "A Gas Filter Correlation Spectrometer for Remote Sensing of Trace Atmospheric Contaminants", Technical Digest pp4 Optical Society of America Topical Meeting on Atmospheric Remote Sensing of the Atmosphere, Incline Village Nevada, Jan. (1985) 8.     Stix, W. H. Morrow, R. Nicholls, A. Charland, "Infrared Remote Sensing of CO and COS Gas emitted by the Galeras Volcano, Colombia, January 8‑10, 1993", Canadian Journal of Remote Sensing, 22:297-304, (September 1996). Dalton, M. P., Watson, I. M., Nadeau, P. A., Werner, C., Morrow, W., and Shannon, J. M.: Assessment of the UV camera sulfur dioxide retrieval for point source plumes, J. Volcanol. Geoth. Res., 188, 358–366, doi: 10.1016/j.jvolgeores.2009.09.013, 2009   10.  G.J.S. Bluth, J.M. Shannon, I.M. Watson,  A. J.  Prata, V.J. Realmuto. 2007. Development of an ultra-violet digital camera for volcanic SO2 imaging. J Volcanology and Geothermal Research 161: 47–56 Taras M., Brown J., McGlashan A., SO2 Camera Final Thesis Report, Niagara College, April 22, 2009 T. Mori, M. Burton. 2006. The SO2 camera: A simple, fast and cheap method for ground-based imaging of SO2 in volcanic plumes. Geophysical Research Letters Vol. 33.
References
GCSO-1 Software - Update