Development of a compact imaging spectrometer form for the solar reflective spectral region.

Current imaging spectrometer forms for terrestrial remote sensing in the visible, near-, and shortwave infrared (VNR/SWIR) spectral range have been implemented in hardware and achieve a high level of performance in terms of both aberration control and signal-to-noise level. These forms are compact, relative to prior art, but more size, weight, and power optimization, while maintaining performance, is desirable for usage on small satellite platforms. Pursuant to that goal, we have developed a compact breadboard prototype VNIR/SWIR imaging spectrometer that maintains the current aberration control and has a large number of spatial samples. The new form utilizes a catadioptric lens and a flat dual-blaze immersion grating yielding a compact design that is relatively easy to manufacture.

Linking climate to incidence of zoonotic cutaneous leishmaniasis (L. major) in pre-Saharan North Africa.

Shifts in surface climate may have changed the dynamic of zoonotic cutaneous leishmaniasis (ZCL) in the pre-Saharan zones of North Africa. Caused by Leishmania major, this form multiplies in the body of rodents serving as reservoirs of the disease. The parasite is then transmitted to human hosts by the bite of a Phlebotomine sand fly (Diptera: Psychodidae) that was previously fed by biting an infected reservoir. We examine the seasonal and interannual dynamics of the incidence of this ZCL as a function of surface climate indicators in two regions covering a large area of the semi-arid Pre-Saharan North Africa. Results suggest that in this area, changes in climate may have initiated a trophic cascade that resulted in an increase in ZCL incidence. We find the correlation between the rainy season precipitation and the same year Normalized Difference Vegetation Index (NDVI) to be strong for both regions while the number of cases of ZCL incidence lags the precipitation and NDVI by 2 years. The zoonotic cutaneous leishmaniasis seasonal dynamic appears to be controlled by minimum temperatures and presents a 2-month lag between the reported infection date and the presumed date when the infection actually occurred. The decadal increase in the number of ZCL occurrence in the region suggests that changes in climate increased minimum temperatures sufficiently and created conditions suitable for endemicity that did not previously exist. We also find that temperatures above a critical range suppress ZCL incidence by limiting the vector's reproductive activity.

Design, calibration, and characterization of a field radiometer using light-emitting diodes as detectors.

The Remote Sensing Group at the University of Arizona has developed multispectral ground-viewing radiometers that use light-emitting diodes as detectors. This work describes the optical design, electrical design, and laboratory calibration of a three-channel radiometer that operates in the visible and near-infrared region of the spectrum. The optical and electrical design of the radiometer is introduced, and then the calibration and characterization of the radiometer are described. Laboratory measurements include the spectral responsivity for each channel of the radiometer, the temperature dependence of the total responsivity for each channel, system linearity, field of view, and finally, the absolute radiometric calibration. A solar-radiation-based calibration is used to determine the absolute responsivity.

Analytical solution for integrating sphere spectral efficiency inclusive of atmospheric attenuation.

An analytical solution to the attenuation of flux within an integrating sphere due to spherical integrating source coating, exit port escape, and atmospheric absorption is derived employing a geometric probability distribution of completed sphere transits. This is used to determine the mean number of completed sphere transits and its variance. Equations that provide the attenuation ratios for the three extinction mechanisms are derived using the energy balance and summation of reflection methods. The mean length of a transit of the sphere and its variance are presented and used to derive expressions for the mean and variance of photon path lengths in the sphere.

Automated statistical approach to Langley evaluation for a solar radiometer.

We present a statistical approach to Langley evaluation (SALE) leading to an improved method of calibration of an automated solar radiometer. Software was developed with the SALE method to first determine whether a day is a good calibration day and then to automatically calculate an intercept value for the solar radiometer. Results from manual processing of calibration data sets agree with those of the automated method to within the errors of each approach.