The Lunar Reconnaissance Orbiter Camera (LROC) consists of two imaging systems that provide synoptic and high resolution imaging of the lunar surface. The Wide Angle Camera (WAC) is a seven color push frame imager with a 90° field of view in monochrome mode and 60° field of view in color mode. From the nominal 50 km polar orbit, the WAC acquires images with a nadir pixel scale of 75 m for each visible band and 384 m for the two ultraviolet bands. The Narrow Angle Camera (NAC) consists of two identical cameras capable of acquiring images with a pixel scale of 0.5 to 1.0 m from a 50 km orbit. Each camera was geometrically calibrated prior to launch at Malin Space Science Systems in San Diego, California. Using thousands of images acquired since launch in June of 2009, improvements to the relative and absolute pointing of the twin NACs were made allowing images on the surface to be projected with an accuracy of 20 meters. Further registration of WAC and NAC images allowed the derivation of a new distortion model and pointing updates for the WAC, thus enabling sub-pixel accuracy in projected WAC images.

Characterization and calibration are vital for instrument commanding and image interpretation in remote sensing. The Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) takes 500 Mpixel greyscale images of lunar scenes at 0.5 meters/pixel. It uses two nominally identical line scan cameras for a larger crosstrack field of view. Stray light, spatial crosstalk, and nonlinearity were characterized using flight images of the Earth and the lunar limb. These are important for imaging shadowed craters, studying ∼1 meter size objects, and photometry respectively. Background, nonlinearity, and flatfield corrections have been implemented in the calibration pipeline. An eight-column pattern in the background is corrected. The detector is linear for \(\mathrm{DN} = 600\mbox{--}2000\) but a signal-dependent additive correction is required and applied for \(\mathrm{DN}<600\). A predictive model of detector temperature and dark level was developed to command dark level offset. This avoids images with a cutoff at \(\mathrm{DN}=0\) and minimizes quantization error in companding. Absolute radiometric calibration is derived from comparison of NAC images with ground-based images taken with the Robotic Lunar Observatory (ROLO) at much lower spatial resolution but with the same photometric angles.

The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) has acquired more than 250,000 images of the illuminated lunar surface and over 190,000 observations of space and non-illuminated Moon since 1 January 2010. These images, along with images from the Narrow Angle Camera (NAC) and other Lunar Reconnaissance Orbiter instrument datasets are enabling new discoveries about the morphology, composition, and geologic/geochemical evolution of the Moon. Characterizing the inflight WAC system performance is crucial to scientific and exploration results. Pre-launch calibration of the WAC provided a baseline characterization that was critical for early targeting and analysis. Here we present an analysis of WAC performance from the inflight data. In the course of our analysis we compare and contrast with the pre-launch performance wherever possible and quantify the uncertainty related to various components of the calibration process. We document the absolute and relative radiometric calibration, point spread function, and scattered light sources and provide estimates of sources of uncertainty for spectral reflectance measurements of the Moon across a range of imaging conditions.

The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) and Narrow Angle Cameras (NACs) are on the NASA Lunar Reconnaissance Orbiter (LRO). The WAC is a 7-color push-frame camera (100 and 400 m/pixel visible and UV, respectively), while the two NACs are monochrome narrow-angle linescan imagers (0.5 m/pixel). The primary mission of LRO is to obtain measurements of the Moon that will enable future lunar human exploration. The overarching goals of the LROC investigation include landing site identification and certification, mapping of permanently polar shadowed and sunlit regions, meter-scale mapping of polar regions, global multispectral imaging, a global morphology base map, characterization of regolith properties, and determination of current impact hazards.

The NASA Lunar Reconnaissance Orbiter Camera (LROC) is comprised of three cameras (Figs 1 and 3): a Wide-Angle Camera (WAC) and two identical Narrow Angle Cameras, called NAC-L and NAC-R. The instruments and electronics were built by Malin Space Science Systems with heritage from the successful cameras MARCI and CTX onboard MRO [1]. The WAC is a push-frame camera with two UV and five visible wavelength filters (321, 360, 415, 566, 604, 643 and 689 nm). Its visible and the UV channels have separate optics providing a spatial resolution of 100 m/pixel and 400 m/pixel, respectively. The focal lengths are 6.0 mm (visible) and 5.04 mm (UV), the F/# is 5.06 for the visible and 5.66 for the UV. The system modulation transfer function (MTF) is 0.3. The WAC will be operated in two modes: multicolor for mineralogical mapping and monochrome to provide a global large-incidence angle basemap and a time-lapse movie of illumination conditions at the poles [2]. Ground calibration was performed to characterize the system response for each camera and a calibration pipeline is now awaiting data from the Moon.