USGS  : Lunar Calibration, ROLO - Robotic Lunar Observatory : ROLO Facility Telescope
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ROLO Database

In 6+ years of regular operations, ROLO has acquired over 85,000 images of the Moon and several hundred thousand star images. Archived images are formatted in cube pairs of the 23 VNIR and 9 SWIR bands. The archive format is compatible with the USGS ISIS [http://isis.astrogeology.usgs.gov] system.

ALEX Images

Processed radiance images are mapped onto a common 576x576-pixel grid fixed to the selenographic coordinate system that covers all points on the Moon visible from Earth. This process uses a modified Lambert Azimuthal Equal-Area projection, locally termed the “ALEX” projection:

alpha = P_2 sin (theta / P_1)

where α is the radial distance of the projected point from [0,0] in the selenographic coordinate system, and θ is the great-circle distance of a point from [0,0]; parameters P1 and P2 are chosen to give the desired coverage and spatial resolution, respectively. In the sample ALEX image shown below, the white band around the lunar disk is the accommodation for the range of libration angles viewable from Flagstaff. The ROLO ALEX grid extends ±11 degrees beyond the limb in selenographic longitude and latitude.

ROLO image in ALEX projection. This image was acquired 1998 December 30 03:45:06 UTC in the ROLO 550nm band. Phase angle is 40.6°; libration is -0.145° in selenographic longitude, +1.120° in selenographic latitude.

Phase and Libration Coverage
Data Reduction Procedures

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