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Proceedings Paper

Spectral band calibration of the Total Ozone Mapping Spectrometer (TOMS) using a tunable laser technique
Author(s): Robert E. Haring; Frederick L. Williams; Ulli G. Hartmann; Doug Becker; Gary C. Vanstone; Hongwoo Park; Pawan K. Bhartia; Richard D. McPeters; Glen Jaross; Matthew Kowalewski
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Paper Abstract

The Total Ozone Mapping Spectrometer (TOMS) provides daily global mapping of the total column ozone in the earth’s atmosphere. It does this by measuring the solar irradiance and the backscattered solar radiance in 6 spectral bands falling within the range from 308.6 nm to 360 nm. The accuracy of the ozone retrieval is highly dependent on the knowledge of the transfer characteristics and center wavelength for each spectral band. A 0.1 nm wavelength error translates to a 1.6% error in ozone. Several techniques have historically been used to perform the wavelength calibration of the TOMS instruments. These methods include the use of film and reference spectra from low-pressure spectral line lamps and the use of continuum sources with a narrow-band scanning monochromator. The spectral transfer characteristic of the Flight Model 5 instrument for the QuikTOMS mission was calibrated using a new technique employing a frequency doubled tunable dye laser. The tunable laser has several advantages that include a very narrow spectral bandwidth; accurate wavelength determination using a wavemeter; and the ability to calibrate the instrument system level of assembly (prior methods required that the calibration be performed at the monochromator sub assembly level). The technique uses the output from a diode-pumped solid state Nd:V04 laser that is frequency doubled to provide a continuous wave 532 nm pump laser beam to a Coherent Model 899-01 frequency doubled ring dye laser. The output is directed into the entrance port of a 6-inch diameter Spectralon integrating sphere. A GaP photodiode is used to monitor the sphere wall radiance while a Burleigh Wavemeter (WA-1500) is used to monitor the wavelength of the visible output of the dye laser. The TOMS field of view is oriented to view the exit port of the integrating sphere. During the measurement process the response of the instrument is monitored as the laser source is stepped in 0.02-nm increments over each of the six TOMS spectral bands. Results of the new technique allow establishing the wavelength center to a precision of better than 0.1 nm. In addition to the spectral band measurements, the laser provided a means to calibrate the radiometric linearity of the QuikTOMS instrument and yield new insights into the stray light performance of the complete optical system.

Paper Details

Date Published: 15 November 2000
PDF: 11 pages
Proc. SPIE 4135, Earth Observing Systems V, (15 November 2000); doi: 10.1117/12.494208
Show Author Affiliations
Robert E. Haring, Orbital Sciences Corp. (United States)
Frederick L. Williams, Orbital Sciences Corp. (United States)
Ulli G. Hartmann, Orbital Sciences Corp. (United States)
Doug Becker, Orbital Sciences Corp. (United States)
Gary C. Vanstone, Orbital Sciences Corp. (United States)
Hongwoo Park, NASA Goddard Space Flight Ctr. (United States)
Pawan K. Bhartia, NASA Goddard Space Flight Ctr. (United States)
Richard D. McPeters, NASA Goddard Space Flight Ctr. (United States)
Glen Jaross, Raytheon ITSS (United States)
Matthew Kowalewski, Raytheon ITSS (United States)

Published in SPIE Proceedings Vol. 4135:
Earth Observing Systems V
William L. Barnes, Editor(s)

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