Some people imagine that the moon is made of cheese, and some think of ROLO as a kind of caramel candy, but in reality ROLO is the RObotic Lunar Observatory, an active project worked diligently by Tom Stone of the USGS Astrogeolgy team. A goal of the project is to determine the precise brightness of the Moon and use it as an absolute radiance calibration standard for Earth-orbiting satellite imaging instruments.
Earth-orbiting spacecraft and their instruments, such as the Sea-viewing Wide Field-of-view Sensor (SeaWiFS); Moderate Resolution Imaging Spectroradiometer (MODIS); Advance Land Imager (ALI); and Geostationary Environmental Satellites (GOES), use data provided by ROLO as part of a calibration reference to monitor the Earth’s brightness levels and its changes.
One might wonder why ROLO uses the Moon as a calibration source. “The surface of the moon has extremely stable reflectance, much more stable than any hardware that can be flown on an ‘on-board’ calibration system” says Tom Stone, Project Scientist.
On clear nights for more than 6 years, twin telescopes on a fork mount have recorded some 85,000 images of the Moon from first quarter to last quarter phase in 32 bands from 350-2500 nm. However, routine observations stopped in September 2003, and intermittent observations continue.
The ROLO project was started as a collaboration between Hugh Kieffer, formerly of the U.S. Geological Survey, who now serves as a consultant on the project, and Robert Wildey, who was then employed with Northern Arizona University (but came to work for U.S. Geological Survey). Robert Wildey developed the acronym ROLO and it is used in his memory; he was a critical part of ROLO from its inception until his death in 1998.
The ultimate goal of project ROLO is to establish the Moon as a spectral radiance standard with an accuracy of 1-2 % absolute, traceable to SI units (Système International d'unités). Another project goal to precisely measure satellite instrument changes has been achieved and is in use by satellite instrument teams.
Link: USGS Astrogeology - ROLO website