Proceedings PaperBolometric imager for solar irradiance studies
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We are presently developing a solar imager with spectrally uniform photometric response over all wavelengths between the UV and IR. Such a Solar Bolometric Imager (SBI) will be capable of accurately measuring heat flow inhomogeneities at the sun's photosphere and will provide an innovative new tool for identifying mechanisms of long-term solar luminosity variation. Our work builds on recent advances in uncooled, relatively high-definition thermal arrays. We have shown that the spectral absorptance of these arrays can be modified by deposition of gold blacks, to provide spectrally uniform response over at least the wavelength range between about 0.3(mu) and 2.5(mu) containing over 95 percent of the total solar irradiance. Our ongoing work is intended to show that quantitative photometry of the solar disc can be performed with such a modified array. We are constructing a breadboard SBI for immediate use with an 8-bit ferro- electric camera, developing a 12-bit camera to make full use of the ferro-electric array's capabilities, and optimizing our process of gold-blacking the TI arrays. Much of the science potential of the SBI could be realized in a balloon experiment. The combination of the SBI and a cavity radiometer would also constitute an excellent SMEX experiment to address a key challenge identified in the Sun- Earth Connection Roadmap recently issued by NASA/OSS.