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High-resolution spectral imaging of the Sun in the far ultraviolet

The Transition Region and Coronal Explorer instrument (TRACE) will use narrow-band interference filters together with other appropriate band limiting elements to make high resolution images of the Sun in the C IV lines at 154.8 and 155.0 nm. Filter observations of solar C IV emission are complicated by the presence of UV Continuum and nearby chromospheric lines because of the relatively wide bandpasses of the narrowest currently available interference filters. TRACE will use a series of filters to estimate the effects of the UV continuum and the long-wavelength `leaks' in the blocking filters which we show are the most important contaminants in the C IV images. Further improvements in filtergraph performance may be realized through the use of tunable Fabry-Perot etalons, which have been under development at Lockheed-Martin. We present test data from a cultured quartz etalon designed for 155 nm, and will discuss the prospects for etalons operation at substantially shorter wavelengths.