The Col-OSSOS project aims to determine the surface properties of Trans-Neptunian Objects (TNOs) by studying a magnitude limited sample of ~100 objects. These objects are m_r =< 23.6, selected from the Outer Solar System Origins Survey (OSSOS) discovery project. OSSOS was a large program on Canada-France-Hawaii Telescope (CFHT) which discovered and tracked 840 TNOs, with careful discovery and followup methods. The discovery biases (limiting magnitude, rate of object motion, etc.) were carefully measured for each discovery field. As a result, this sample has entirely known selection effects. The Col-OSSOS sample, which is a sub-sample of this survey, is the first color survey of classified TNOs which has known selection biases and can be used to determine the underlying properties of the Trans-Neptunian region.

All TNOs observed by Col-OSSOS will be measured in g, r, and J bands using Gemini-North GMOS and NIRI. These colors form the core of our observing program. The majority of targets are also observed in u band using CFHT Megacam, using a ToO approach. The u band observations are executed simultaneously by CFHT during the Gemini observations. This ensures that the rotational variability has a minimal effect on the measured brightness. Approximately a third of the sample was also observed in z band, using either Subaru Suprime-Cam or Gemini GMOS. The combination of these filters has proved extremely powerful in classifying different surface classes in the Kuiper belt.