  Stars of late-M and L spectral types, collectively known as Ultracool Dwarfs
(UCDs), may be excellent targets for searches for extrasolar planets. Owing to
their small radii, the signal from an Earth-size planet transiting a UCD is, in
principle, readily detectable. We present results from a study designed to
evaluate the feasibility of using precise near infrared (NIR) photometry to
detect terrestrial extrasolar planets orbiting UCDs. We used the Peters
Automated InfRared Imaging TELescope (PAIRITEL) to observe a sample of 13 UCDs
over a period of 10 months. We consider several important systematic effects in
NIR differential photometry and develop techniques for generating photometry
with a precision of 0.01 mag and long-term stability. We simulate the planet
detection efficiency of an extended campaign to monitor a large sample of UCDs
with PAIRITEL. We find that both a targeted campaign with a single telescope
lasting several years and a campaign making use of a network of telescopes
distributed in longitude could provide significant sensitivity to terrestrial
planets orbiting UCDs, potentially in the habitable zone.
