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The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket-borne observatory
designed to produce ultra-high resolution full-disk images of the Sun. The MSSTA utilizes an
array of Ritchey-Chretien, Cassegrain, and Herschelian normal incidence multilayer x-ray/EUV
telescopes and thin film interference-coated FUV telescopes to produce narrow band solar images
at selected wavelengths in this broad region of the electromagnetic spectrum. This mission places
extremely strenuous requirements upon the imaging detector. The desire for ultra-high resolution
images of the solar disk and corona out to 1.5 R demands an information storage capacity which
can at the present time be met only by the highest quality photographic emulsions. Furthermore,
there exists a tremendous range in intensity levels and contrast of solar x-ray/EUV/FUV emission
features. The MSSTA imaging detectors must have the ability to record extremely bright, high
contrast features associated with flares and active regions without saturating, whicle still maintaining
the capability of capturing very faint, low contrast structures in coronal holes, polar coronal
plumes, network structures and faint ioops in the corona. This very difficult requirement established
the need for very wide latitude photographic emulsions so that these diverse features can be
imaged at appropriate density levels within the range of exposure times that can be accommodated
on a sounding rocket mission.
Furthermore, the films selected for the MSSTA flight must be sensitive over a very broad
and difficult portion of the electromagnetic spectrum. The payload must be evacuated prior to
launch to preserve the integrity of the delicate EUV filters. Hence, the films chosen must also
have low-outgassing rates and possess the ability to be unspooled from the reel and transported
through conventional film cameras while dry, after exposure to high vacuum, without experiencing
the degradation to the images which can result from electrostatic discharges. In this paper we
describe the performance and characteristics required of photographic films for solar observations
in the soft x-ray/EUV and FUV wavelength regimes. We discuss the properties of the important
new emulsions that have been selected for flight on the Multi-Spectral Solar Telescope Array. We
also present exciting and important new data on the response characteristics of a tabular grain
Experimental XUV 100 film and an uncoated Experimental Spectroscopic 649 emulsion based
upon measurements of these films at the SURF II synchrotron facility of the National Institute of
Standards and Technology and at the Space Sciences Laboratory of the University of California,
Berkeley.
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