2008

Detecting Phycocyanin-Pigmented Microbes in Reflected Light

Concentrations are estimated from ratios between spectral radiances.

A recently invented method of measuring concentrations of phycocynanin- pigmented algae and bacteria in water is based on measurement of the spectrum of reflected sunlight. When present in sufficiently high concentrations, phycocynanin- pigmented microorganisms can be hazardous to the health of humans who use, and of animals that depend on, an affected body of water. The present method is intended to satisfy a need for a rapid, convenient means of detecting hazardous concentrations of phycocynanin-pigmented microorganisms. Rapid detection will speed up the issuance of public health warnings and performance of corrective actions.

Image
Reflected Light in These Wavelength Bands is measured, and the measurements are used to estimate concentrations of phycocynanin-pigmented microbes in water.

The method involves the measurement of light reflected from a body of water in at least two, but preferably five wavelength bands. In one version of the method, the five wavelength bands are bands 1, 3, 4, 5, and 7 of the Thematic Mapper (TM) multispectral imaging instrument aboard the Landsat-7 satellite (see table). In principle, other wavelength bands indicative of phycocynanin could be used alternatively or in addition to these five. Moreover, although the method was originally intended specifically for processing Landsat-7 TM data, it is equally applicable to processing of data from other satellite-borne instruments or from airborne, hand-held, buoy- mounted, tower-mounted, or otherwise mounted instruments that measure radiances of light reflected from water in the wavelength bands of interest.

Image
Measured Concentrations of Phycocynanin in water samples (represented by the dots) collected from Lake Erie on September 27, 2000 are compared with concentration estimated by means of the equation in the text (represented by the straight line) incorporating Ki values obtained by correlation with water-sample concentrations measured on July 1, 2000.

The radiance measurements are digitized and used to estimate the concentration of phycocyanin-pigmented microbes by means of the equation X = K1K2R31 + K3R41K4R43K5R53 + K6R73K7R74, where X is the approximate concentration of phycocynanin-pigmented microbes; for any pair of band indices i and j, Rij is the radiance in band i divided by the radiance in band j, calculated after subtraction for atmospheric haze in each band; and the Ki values are chosen to obtain the best correlation between the estimated concentrations and concentrations determined by laboratory analysis of water samples. The figure presents an example of concentrations estimated from a set of Landsat data by use of this equation and the correspond - ing concentrations determined from water samples.

This work was done by Robert K. Vincent of Bowling Green State University for Glenn Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-18202-1.

This Brief includes a Technical Support Package (TSP).

Detecting Phycocyanin-Pigmented Microbes in Reflected Light (reference LEW-18202-1) is currently available for download from the TSP library.

Please Login at the top of the page to download.

 

White Papers

Fundamentals of Vector Network Analysis Primer
Sponsored by Rohde and Schwarz
Sensors For Use In Aerospace, Military and Industrial Markets
Sponsored by Columbia Research
Learn LED Test Techniques
Sponsored by Keithley
SpaceClaim in Manufacturing
Sponsored by SpaceClaim
Finding the Right Manufacturer for Your Design
Sponsored by Sunstone Circuits
Comparison of Interface Pressure Measurement Options
Sponsored by Tekscan

White Papers Sponsored By: