SELenological And ENgineering Explorer Research Articles

Large Area High-Resolution 3D Mapping of the Von Kármán Crater: Landing Site for the Chang’E-4 Lander and Yutu-2 Rover

We demonstrate the creation of a large area of high-resolution (260 × 209 km2 at 1 m/pixel) DTM mosaic from the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images over the Chang’E-4 landing site at Von Kármán crater using an in-house deep learning-based 3D modelling system developed at University College London, called MADNet, trained with lunar orthorectified images and digital terrain models (DTMs). The resultant 1 m DTM mosaic is co-aligned with the Chang’E-2 (CE-2) and the Lunar Orbiter Laser Altimeter (LOLA)—SELenological and Engineering Explorer (SELENE) blended DTM product (SLDEM), providing high spatial and vertical congruence. In this paper, technical details are briefly discussed, along with visual and quantitative assessments of the resultant DTM mosaic product. The LROC NAC MADNet DTM mosaic was compared with three independent DTM datasets, and the mean differences and standard deviations are as follows: PDS photogrammetric DTM at 5 m grid-spacing had a mean difference of −0.019 ± 1.09 m, CE-2 DTM at 20 m had a mean difference of −0.048 ± 1.791 m, and SLDEM at 69 m had a mean difference of 0.577 ± 94.940 m. The resultant LROC NAC MADNet DTM mosaic, alongside a blended LROC NAC and CE-2 MADNet DTM mosaic and a separate LROC NAC, orthorectified image mosaic, are made publicly available via the ESA planetary science archive’s guest storage facility.

Topographic Correction of the SELENE MI Images with the LOLA DEM around Shackleton Crater

Due to the complicated terrain and extreme illumination condition in the lunar south polar region, topography has an impact on the reflectance of the area. This may result in the misinterpretation of the properties of the lunar surface. Therefore, an image obtained across Shackleton Crater by the Multi-band Imager (MI) onboard the first Japanese lunar orbiter SELENE (SELenological and ENgineering Explorer) was utilized to evaluate the topographic effect on the reflectance of the polar region. Three methods—i.e., b correction, C correction, and Minnaert correction—were applied to the MI image to reduce the topographic effect. It was found that the reflectance result of C correction suffers from overcorrection. The topographic effect is enlarged, rather than suppressed, in the reflectance derived with Minnaert correction. Comparatively, b correction is the more appropriate method for the topographic correction of the MI image across the study area. The reflectance of the sunlit slope of the crater wall in the study area decreased by ~60%. The reflectance of the area outside of the crater, with a gentler slope compared to the crater wall, decreased by ~20%. Meanwhile, according to the correlation of the cosine of the local solar incidence angle and the corrected reflectance, the topographic effect was seemingly not completely eliminated in the MI image. However, by analyzing the spectral absorption features of the 1250 nm band, we can attribute this “residual” effect to the different compositions inside and outside of Shackleton Crater, most likely caused by a high concentration of plagioclase. Topographic correction of the MI images over NASA candidate landing regions was also conducted. The results suggest that the topographic effect can contribute significantly to the reflectance of the sunlit slopes, and should not be neglected in the analysis of the reflectance images. This study highlights the topographic impact on the reflectance of the lunar south pole’s surface. In addition, our results also suggest that the compositional differences under various terrains should be considered in the evaluation of the topographic correction of specific regions, such as Shackleton Crater’s inner walls.

Review for Examining the Oxidation Process of the Moon Using Generative Adversarial Networks: Focusing on Landscape of Moon

Japan Aerospace Exploration Agency (JAXA) has collected and studied the data observed by the lunar probe, SELenological and ENgineering Explorer (SELENE), from 2007 to 2017. JAXA discovered that the oxygen of the upper atmosphere of the Earth is transported to the moon by the tail of the magnetic field. However, this research is still in progress, and more data are needed to clarify the oxidation process. Therefore, this paper supplements the insufficient observation data by using Generative Adversarial Networks (GAN) and proposes a review paper focusing on the methodology, enhancing the level of completion of the preceding research, and the trend of examining the oxidation process and landscape of the moon. We propose using Anokhin’s Conditionally-Independent Pixel Synthesis (CIPS) as a model to be used in future experiments as a result of the review. CIPS can generate pixels independently for each color value, and since it uses a Multi-Layer Perceptron (MLP) network rather than spatial convolutions, there is a significant advantage in scalability. It is concluded that the proposed methodology will save time and costs of the existing research in progress and will help reveal the causal relationship more clearly.

Analysis Based on Onboard Lamp and Lunar Vicarious Calibrations for Sensitivity Degradation of a Hyperspectral Sensor

We assessed the degradation of the radiance lamp in the onboard calibration system of the Spectral Profiler, a hyperspectral sensor onboard the Japanese Selenological and Engineering Explorer (SELENE), which was launched in September 2007 and observed the Moon until June 2009. We found that the output of the radiance lamp soon after launch increased by 3.2%–4.6% as compared with the prelaunch output, after which it decreased over time. The total decrease during the mission lifetime of about 1.5 years after the increase of 3.2%–4.6% was ~1.1%–1.5%, which is slightly larger than the < 1% degradation of the sensitivity of the sensor, as derived from vicarious calibration using the Apollo 16 landing site observations. Thus, we confirmed that the radiance lamp became degraded, but the degree of degradation was within 1% during ~1.5 years. We also found a wavelength dependence in the degradation, in which degradation was larger for shorter wavelengths, especially for wavelengths less than ~ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.8\,\mu \text{m}$ </tex-math></inline-formula> . The trend of the wavelength dependence was shown to be consistent with a model of blackbody radiance with a decrease in temperature of the lamp of about −5 K, suggesting that the degradation of the lamp was mostly due to temperature decrease of about −3 K/yr. Our results may provide an important constraint on the quantitative assessment of the degradation of the sensitivity of remote-sensing sensors using an onboard calibration system, such as the Advanced Spaceborne Thermal Emission and Reflection Radiometer.

Estimation of bulk permittivity of the Moon\u2019s surface using Lunar Radar Sounder on-board Selenological and Engineering Explorer

Site-dependent bulk permittivities of the lunar uppermost media with thicknesses of tens to hundreds meters were estimated based on the data from Lunar Radar Sounder onboard the Selenological and Engineering Explorer (SELENE). It succeeded in sounding almost all over the Moon’s surface in a frequency range around 5 MHz to detect subsurface reflectors beneath several lunar maria. However, it is necessary to estimate the permittivity of the surface regolith of the Moon in order to determine the actual depths to those reflectors instead of apparent depths assuming a speed of light in the vacuum. In this study, we determined site-dependent bulk permittivities by two-layer models consisting of a surface regolith layer over a half-space with uniform, but different physical properties from the layer above. Those models consider the electrical conductivity as well as the permittivity, whose trade-off was resolved by utilizing the correlation between iron–titanium content and measured physical properties of lunar rock samples. Distribution of the iron–titanium content on the Moon’s surface had already been derived by spectroscopic observation from SELENE as well. Four lunar maria, Mare Serenitatis, Oceanus Procellarum, Mare Imbrium, and Mare Crisium, were selected as regions of evident reflectors, where we estimated the following four physical properties of each layer, i.e., bulk permittivity, porosity, loss tangent and electrical conductivity to conclude the actual depths of the reflectors are approximately 200 m on average. The bulk permittivity ranges from 2.96 at Mare Imbrium to 6.37 at Oceanus Procellarum, whereas the porosity takes the values between 1.8 and 41.1% in the respective maria. It was found that although the bulk permittivity of the four lunar maria differs from a mare to a mare, it shows a good correlation with their composition, viz., their iron–titanium content.

Topography of nearside mare graben: Implications for dike-induced or passive extension formation

Graben are a common tectonic landform associated with lunar mare. These graben are hypothesized to have formed either due to subsidence induced flexure resulting from loading of the lithosphere by mare basalt (mascon tectonics) or by dikes related to intrusive volcanism. High-resolution topography derived from data from the Lunar Reconnaissance Orbiter (LRO) and SELenological and Engineering Explorer (SELENE) allow for the detailed analysis of flat-floored mare-radial and mare-concentric graben. Modeling of graben formation from dike-induced dilation predicts rises on graben flanks that decay in relief with distance from the central trough. Graben formation from passive extensional stresses are not expected to produce discernable flank rises. We take a systematic approach to assessing morphology of flat-floored graben in mascon and non-mascon mare settings. Modeling of dilation effects due to intrusion of dikes of realistic dimension and depth indicate that the predicted relief of flank rises are at or below the limits of detection using best available topography. However, it is concluded that the lack of evidence of flank rises indicates nearside graben formed by passive extension. The presence of graben in both mascon (e.g., Mare Humorum) and non-mascon settings (e.g., Oceanus Procellarum) suggests that flexure and extension are strongly influenced by the local thickness and/or strength of the mechanical lithosphere.

An Improved Digital Elevation Model of the Lunar Mons Rümker Region Based on Multisource Altimeter Data

Mons Rümker is the primary candidate region for the lunar landing mission of Chang’E-5. We propose a data processing method that combines multisource altimeter data and we developed an improved digital elevation model (DEM) of the Mons Rümker region with a horizontal resolution of 256 pixels per degree. The lunar orbiter laser altimeter (LOLA) onboard the lunar reconnaissance orbiter (LRO) acquired 884 valid orbital benchmark data with a high precision. A special crossover adjustment of 156 orbital profiles from the Chang’E-1 laser altimeter (LAM) and 149 orbital profiles from the SELenological and ENgineering Explorer (SELENE) laser altimeter (LALT) was applied. The radial residual root mean square (RMS) of the LAM was reduced from 154.83 ± 43.60 m to 14.29 ± 27.84 m and that of the LALT was decreased from 3.50 ± 5.0 m to 2.75 ± 4.4 m. We used the adjusted LAM and LALT data to fill the LOLA gaps and created the merged LOLA + LAM and LOLA + LALT DEMs. The merged LOLA + LAM DEM showed distortions because of the horizontal geolocation errors in the LAM data. The merged LOLA + LALT DEM was closer to the ground truth than the LOLA-only DEM when validated with the images of the LRO camera (LROC).

High-precision co-registration of orbiter imagery and digital elevation model constrained by both geometric and photometric information

The alignment of images to a reference digital elevation model (DEM) has many applications, especially in planetary exploration. In this paper, we propose a novel high-precision co-registration method for pixel-based matching between an image and a reference DEM to rectify the ever-increasing number of orbiter images to DEMs in a unified reference frame automatically. First, the DEM is converted to a simulated image using a hillshading technique based on a photometric model and the illumination conditions of the image. Then, an initial matching between the simulated and input images is performed based on affine scale-invariant feature transform (ASIFT). The rational function model (RFM) of the image is established and used as a geometric constraint. Then, with tie points (TPs) generated by the initial ASIFT matching, the RFM geometric model of the image is refined, and the gross errors in the TP set are iteratively eliminated. Finally, a high-precision co-registration by pixel-based Least-Squares (LS) image matching is performed using the refined geometric model. Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) and SLDEM2015 (a combined product of Lunar Reconnaissance Orbiter Laser Altimeter (LOLA) and a DEM generated by the Japanese Selenological and Engineering Explorer (SELENE) terrain camera) images are used in our experiment. Results using 17 NAC images at different latitudes demonstrate that the proposed co-registration method is effective and can attain an accuracy of 18.3 pixels in the image space and 25.17 m (0.5 pixel of the reference DEM) in the object space. The method offers an automatic and high-precision matching of LRO NAC images to SLDEM2015. It is also applicable to the co-registration of other orbital images to a reference DEM.

Reflection imaging of the Moon's interior using deep‐moonquake seismic interferometry

AbstractThe internal structure of the Moon has been investigated over many years using a variety of seismic methods, such as travel time analysis, receiver functions, and tomography. Here we propose to apply body‐wave seismic interferometry to deep moonquakes in order to retrieve zero‐offset reflection responses (and thus images) beneath the Apollo stations on the nearside of the Moon from virtual sources colocated with the stations. This method is called deep‐moonquake seismic interferometry (DMSI). Our results show a laterally coherent acoustic boundary around 50 km depth beneath all four Apollo stations. We interpret this boundary as the lunar seismic Moho. This depth agrees with Japan Aerospace Exploration Agency's (JAXA) SELenological and Engineering Explorer (SELENE) result and previous travel time analysis at the Apollo 12/14 sites. The deeper part of the image we obtain from DMSI shows laterally incoherent structures. Such lateral inhomogeneity we interpret as representing a zone characterized by strong scattering and constant apparent seismic velocity at our resolution scale (0.2–2.0 Hz).

Investigation of Reflectance Distribution and Trend for the Double Ray Located in the Northwest of Tycho Crater

Analysis of lunar samples returned by the US Apollo missions revealed that the lunar highlands consist of anorthosite, plagioclase, pyroxene, and olivine; also, the lunar maria are composed of materials such as basalt and ilmenite. More recently, the remote sensing approach has enabled reduction of the time required to investigate the entire lunar surface, compared to the approach of returning samples. Moreover, remote sensing has also made it possible to determine the existence of specific minerals and to examine wide areas. In this paper, an investigation was performed on the reflectance distribution and its trend. The results were applied to the example of the double ray stretched in parallel lines from the Tycho crater to the third-quadrant of Mare Nubium. Basic research and background information for the investigation of lunar surface characteristics is also presented. For this research, resources aboard the SELenological and ENgineering Explorer (SELENE), a Japanese lunar probe, were used. These included the Multiband Imager (MI) in the Lunar Imager / Spectrometer (LISM). The data of these instruments were edited through the toolkit, an image editing and analysis tool, Exelis Visual Information Solution (ENVI).

Calibration of NIR 2 of Spectral Profiler Onboard Kaguya/SELENE

The Spectral Profiler (SP) is a visible–near infrared spectrometer onboard the Japanese Selenological and Engineering Explorer (SELENE), which was launched in 2007 and observed the Moon until June 2009. The SP consists of two gratings and three linear-array detectors: VIS (0.5–1.0 $\mu\hbox{m}$ ), NIR 1 (0.9–1.7 $\mu\hbox{m}$ ), and NIR 2 (1.7–2.6 $\mu\hbox{m}$ ). In this paper, we propose a new method for radiometric calibration of NIR 2, specifically for the dark output (background) estimate, which is different from the previous method used for VIS and NIR 1. We show that the reflectance spectra of NIR 2 derived from the new radiometric calibration show less noise than those of the previous method. Based on an analysis of the reflectance spectra at exposure sites of the end-member minerals on the lunar surface, we demonstrated that the spectral features of the 2- $\mu\hbox{m}$ band in the NIR 2 spectra are consistent with those expected from the minerals inferred from the features of the 1- $\mu\hbox{m}$ band in the VIS and NIR 1 spectra. Finally, we examined the repeatability of the radiometric calibration of NIR 2 using the SP data near the Apollo 16 landing site observed at four different times. The typical difference in the reflectance at wavelengths $ was a few percent, which is within the uncertainty due to the error in the background estimate, suggesting that there was no significant change in the sensitivity of NIR 2 over the mission period.

Numerical modelling of impact crater formation associated with isolated lunar skylight candidates on lava tubes

Skylights are openings on subsurface voids as lava tubes and caves. Recently deep hole structures, possibly skylights, were discovered on lunar photo images by the JAXA SELenological and ENgineering Explorer (SELENE)-Kaguya mission, and successively confirmed by the NASA Lunar Reconnaissance Orbiter (LRO) mission. Vertical hole structures and possibly underlying subsurface voids have high potential as resources for scientific study, and future unmanned and manned activities on the Moon. One mechanism proposed for their formation is impact cratering. The collapse of craters is due to the back spallation phenomena on the rear surface of the lava tube roofs. Previous analysis in this topic was based on small-scales laboratory experiments. These have pointed out that (i) the target thickness-to-crater diameter ratio is 0.7, and (ii) the projectile diameter-to-target thickness ratio is 0.16, at the ballistic limit once extrapolated to planetary conditions.We investigate the impact process that might trigger the formation of lunar skylight candidates by numerically simulate the craters associated to the observed hole structures. The Marius Hills hole (MHh, located in a 26m thick target) was formed by a 4m projectile, which originated an impact crater of 40.0±1.6m in diameter. The Mare Tranquillitatis hole (MTh, located in a 47m thick target) was formed by a 7.2m projectile, which originated an impact crater of 75.6±3.0m in diameter. The target thickness-to-crater diameter ratio is 0.65 and 0.62, respectively for MHh and MTh. These values are smaller than the laboratory experiment ballistic limit ratio (0.7), supporting the hypothesis of collapse at the studied sites. The projectile diameter-to-target thickness ratio is 0.15 for both MHh and MTh, which is slightly smaller than we expected. The discrepancy could be due to the model assumption of vertical impact. We derived via modelling the ballistic limit for planetary scales and found that the target thickness-to-crater diameter ratio is 0.87.We discuss the implications of the proposed scenario for skylight formation in terms of future robotic or human exploration of the Moon, as evaluated in COSPAR and ILEWG.

One Moon, Many Measurements 3: Spectral reflectance

Remote-sensing datasets obtained by each instrument aboard Selenological and Engineering Explorer (SELENE) and Chandrayaan-1 have not been compared directly, and the characteristics of each instrument’s data, which may reflect the observation conditions of each instrument and/or residual error in instrument calibration, are unknown. This paper describes the basic characteristics of the data derived by each instrument, briefly describes the data-processing conversion from radiance to reflectance, and demonstrates what we can achieve by combining data obtained by different instruments on different missions (five remote-sensing instruments and an Earth-based telescope). The results clearly demonstrate that the spectral shapes of the instruments are comparable and thus enable us to estimate the composition of each geologic unit, although absolute reflectances differ slightly in some cases.

Band‐limited Bouguer gravity identifies new basins on the Moon

Spectral domain forward modeling is used to generate topography‐implied gravity for the Moon using data from the Lunar Orbiter Laser Altimeter instrument operated on board the Lunar Reconnaissance Orbiter mission. This is subtracted from Selenological and Engineering Explorer (SELENE)‐derived gravity to generate band‐limited Bouguer gravity maps of the Moon so as to enhance the gravitational signatures of anomalous mass densities nearer the surface. This procedure adds evidence that two previously postulated basins on the lunar farside, Fitzgerald‐Jackson (25°N, 191°E) and to the east of Debye (50°N, 180°E), are indeed real. When applied over the entire lunar surface, band‐limited Bouguer gravity reveals the locations of 280 candidate basins that have not been identified when using full‐spectrum gravity or topography alone, showing the approach to be of utility. Of the 280 basins, 66 are classified as distinct from their band‐limited Bouguer gravity and topographic signatures, making them worthy of further investigation.

Integration of Chang'E-1 Imagery and Laser Altimeter Data for Precision Lunar Topographic Modeling

Lunar orbital imagery and laser altimeter data are two major data sources for lunar topographic modeling. Most of the previous work has processed imagery and laser altimeter data separately. Usually though, there are inconsistencies between the topographic models derived from them. This paper presents an endeavor to integrate the Chang'E-1 imagery and laser altimeter data for consistent and precision lunar topographic modeling. A combined adjustment model for the Chang'E-1 imagery and laser altimeter data is developed, in which the participants are the laser altimeter points, image exterior orientation (EO) parameters, and tie points collected from the stereo images. A weighting scheme is designed for the participants in the adjustment, and a local surface constraint is imposed to improve the adjustment performance. The output of the combined adjustment is the refined image EO parameters and laser ground points. Experimental results using the Chang'E-1 data in the Apollo 15 and 16 landing site areas show that the proposed combined adjustment approach can reduce the misregistrations between the imagery and the laser altimeter data by a maximum of 1-18 pixels in image space. The Japanese SELenological and ENgineering Explorer (SELENE) laser altimeter data at the Apollo 15 and 16 landing site areas are employed for comparison analysis. Small shifts between the SELENE and Chang'E-1 laser altimeter data were found. The topography derived from Chang'E-1 data after the combined adjustment shows a relatively consistent trend with the topography determined by the SELENE laser altimeter data.

Orientation of the Geometrically Best fitting Triaxial Lunar Ellipsoid with Respect to the Mean Earth/Polar Axis Reference Frame

Orientation of the Geometrically Best fitting Triaxial Lunar Ellipsoid with Respect to the Mean Earth/Polar Axis Reference FrameThis study provides new estimates for the orientation of a geometrically best fitting lunar triaxial ellipsoid with respect to the mean Earth/polar axis reference frame calculated from the footprint positions of the Chang'E-1 (CE-1), SELenological and ENgineering Explorer (SELENE) laser altimetry measurements and Unified Lunar Control Networks 2005, (ULCN 2005) station coordinates. The semi-principal axes of the triaxial ellipsoid and the coordinates of its geometric center are also calculated simultaneously. All the estimated parameters from all three data sets are found to be consistent. In particular, the RMS differences of the semi-principal axes of the triaxial ellipsoids and the locations of their geometric centers from solutions with and without modeling Euler angles (orientation of the triaxial ellipsoid) using uniformly distributed laser altimetry (LAL) footprints are 29 and 31 m respectively. The misclosures of all the solutions indicate a better fit for the triaxial ellipsoid to the footprint and station coordinates if the Euler angles are included in the models.

Accuracy assessment of lunar topography models

Both the Chang’E-1 and SELenological and ENgineering Explorer (SELENE) lunar missions, launched in 2007, provide an opportunity for significant advances in lunar science. In particular, both orbiters provide refined lunar topography models with unprecedented finer resolution and improved accuracy, especially for the far side and the polar areas of the Moon where fewer valid measurements have been available to date. An evaluation of the derived topography models is essential for the improved interpretation of selenophysics, including a knowledge of the interior of the Moon. This study provides both external and internal accuracy assessments for the derived topographic models (note that different data sets are used, albeit independent). The external comparison, which consists of comparing the topographic models with landmarks established with lunar laser ranging and radio tracking, yields an accuracy estimate of 157 m for the Change’E-1 model and 58 m for the SELENE model (150 m and 55 m if the newly recovered Lunakhod-1 site is included). The internal comparison, consisting of crossover analysis of the altimeter data after the removal of once-per-orbital-revolution errors, yields an accuracy estimate of 206 m and 68 m, respectively. These comparisons allow the establishment of conservative estimates of accuracy of 200 m and 70 m for the Chang’E-1 and SELENE models, respectively. Given the conservative estimates on the accuracy, both models yield significant improvement by factors of 2.5 and 8, respectively, when compared with a contemporary lunar topography model, i.e., the Unified Lunar Control Network 2005 (ULCN2005).

Research Spotlight: Uranium mapped on Moon

Studies of abundances and distribution of radioactive elements can help answer questions about the formation and evolution of the Moon. Using data from instruments on board the Japanese Kaguya spacecraft (also known as Selenological and Engineering Explorer ( SELENE)), Yamashita et al. mapped the global distribution of uranium and the uranium‐thorium ratio on the surface of the Moon. Uranium and thorium are radioactive elements that emit unique gamma ray signatures, which can be identified by Kaguya's gamma ray spectrometer.

Ground Compatibility Tests for Gravity Measurement of SELENE: Accuracies of Two- and Four-Way Doppler and Range Measurements

The Japanese lunar mission Selenological and Engineering Explorer (SELENE) was launched in September 2007 and continued its mission until June 2009, when the main orbiter impacted with the surface of the Moon. SELENE consisted of three satellites: Main, Rstar, and Vstar. Rstar’s tasks were to forward up-link signals from the Usuada Deep Space Center (UDSC) to Main, and to down-link returning signals from Main to UDSC. We refer to this tracking sub-system as a four-way Doppler measurement. In contrast, conventional tracking systems between Rstar and UDSC as well as between Main and ground stations are referred to as two-way Doppler and range measurements. Using Main and Rstar, we successfully observed the gravity field over the farside of the Moon. Because four-way Doppler measurements via a relay sub-satellite were a fundamental experiment in space for Japanese space agencies, compatibility of radiometric instruments onboard Main and Rstar to UDSC were carefully examined at the UDSC using components manufactured for flight models. These tests not only proved the feasibility of the four-way Doppler measurements but also provided biases and variations of the four-way Doppler and two-way Doppler and range measurements that were later taken into account during the processing of tracking data and the analysis of the lunar global gravity field.

Characterization of Multiband Imager Aboard SELENE

The Multiband Imager (MI) is a high-resolution, multi-spectral imaging instrument for lunar exploration. It consists of two cameras, VIS and NIR, and is carried on the SELenological and ENgineering Explorer (SELENE), launched on Sep. 14, 2007. During the observation from January 2008 to June 2009, MI acquired about 450,000 scenes of multispectral image. The radiometric properties of the cameras were characterized using the pre-flight data derived in laboratory experiments with a calibrated integrating sphere. Twelve light source sets were used to examine the S/N ratio, linearity, and saturation level of the cameras. The dark field signal is quite stable in both cameras, having a noise level of less than 1 DN (VIS) and 2 DN (NIR). The fluctuation in the light field is also low (<2 DN), indicating that the spatial nonuniformity in the camera responses can be removed using a flat field. In order to remove the smear signals due to the frame transfer in the VIS data, we developed an iterate algorithm using all bands in the VIS camera. The S/N ratio, which is critical to the precision of the product, is estimated to exceed 160 for the VIS bands and 400 for the NIR bands under low illumination conditions (5% of lunar surface reflectance). Based on the S/N ratio, the radiometric error due to the noise is calculated to be less than 0.7% for VIS and 0.2% for NIR. The relationship between input and output of the VIS camera is linear with a residual of less than 0.6 DN, corresponding to a radiometric error of 0.3%. The NIR exhibits a non-linear response to the input radiance. A cubic function best fits the pre-flight data with an average residual of 8 DN (corresponds to an error of 0.8%). Validation using in-flight data indicated that the instability of the dark output has not changed, but the level of dark output has slightly changed in the NIR bands (less than 6 DN). The pixel-to-pixel sensitivity variation in the orbit has been changed from that in the pre-flight experiment. The difference between the in-flight data and the pre-flight data ranges within ±2%. There is also a small (less than ±1%) but nonnegligible difference between in-flight data of different cycles in both the VIS and NIR bands, suggesting that the coefficient for spatial ununiformity correction needs to be calculated for each cycle.