  Efforts to detect ultrahigh energy neutrinos are driven by several
objectives: What is the origin of astrophysical neutrinos detected with
IceCube? What are the sources of ultrahigh energy cosmic rays? Do the ANITA
detected events point to new physics? Shedding light on these questions
requires instruments that can detect neutrinos above $10^7$ GeV with sufficient
sensitivity - a daunting task. While most ultrahigh energy neutrino experiments
are based on the detection of a radio signature from shower particles following
a neutrino interaction, we believe that the detection of Cherenkov and
fluorescence light from shower particles is an attractive alternative. Imaging
air showers with Cherenkov and fluorescence light is a technique that is
successfully used in several ultrahigh energy cosmic ray and very-high energy
gamma-ray experiments. We performed a case study of an air-shower imaging
system for the detection of earth-skimming tau neutrinos. The detector
configuration we consider consists of an imaging system that is located on top
of a mountain and is pointed at the horizon. From the results of this study we
conclude that a sensitivity of $3\cdot10^{-9}$ GeV cm$^{-2}$s$^{-1}$sr$^{-1}$
can be achieved at $2\cdot10^8$ GeV with a relatively small and modular system
after three years of observation. In this presentation we discuss key findings
of our study and how they translate into design requirements for an imaging
system we dub Trinity.
