The Robotic Lunar Observatory (ROLO) was an astronomical observatory funded by NASA and located at the United States Geological Survey Flagstaff Science Campus atop McMillan Mesa in Flagstaff, Arizona. Its purpose was to enable the Moon to be used as a radiance calibration source for Earth-orbiting remote-sensing spacecraft. The program ceased observations in September of 2003, but the facility is maintained for calibration and instrument characterization purposes. It consists of two 20 cm (7.9 in) Ritchey-Chrétien telescopes attached to an equatorial mount made by DFM Engineering. One telescope is fitted with a sensor optimized for visible and near-infrared (VNIR) wavelengths, while the other is tuned to short-wavelength infrared (SWIR).