Exoplanet population studies indicate that small rocky planets may be common around very low-mass stars and brown dwarfs: "ultra-cool" dwarfs. Temperate rocky planets around ultra-cool dwarf stars could be the best targets for detecting the atmospheric signatures of extrasolar life with the James Webb Space Telescope: because of a favourable star-to-planet contrast ratio and very short orbital periods in the habitable zone that allow frequent observing opportunities. The seven-rocky-planet planet system around the ultra-cool dwarf TRAPPIST-1 is the best — and so far only — such known example. With James Webb launching in two years and with a nominal mission lifetime of only five years, we urgently need to discover more temperate planets around nearby ultra-cool dwarfs.

We are conducting a large Spitzer Space Telescope program to search for exoplanets around 15 ultra-cool dwarfs. Our sample is optimized for transit planet discoveries by including only stars inferred to rotate nearly equator-on. The observed near-ubiquitous spin-orbit alignment between the host stars and the planets in multi-planet systems dictate that any planetary systems around our selected ultra-cool dwarfs should also be oriented nearly edge-on. We will describe our survey and will present preliminary findings.