Lunar Reflectance Research Articles

Photometric recovery of Apollo metric imagery with Lunar-Lambertian reflectance

The scene radiance of the lunar surface, the reflectance of which depends on the topographical configuration is reconstructed from Apollo orbital imagery. The pixel value is determined by the camera response of sensor exposure which is proportional to scene radiance, lunar reflectance and exposure time. Based on the Lunar-Lambertian reflectance model, the point-wise reflectance is pre-calculated from the Apollo metadata and digital elevation models. The surface radiance, exposure time and camera response are estimated by the maximum likelihood method for sensor exposure which follows a continuous Poisson distribution with the mean of surface radiance. An alternating parameter scheme is proposed to determine the one family of parameters from the others. The photometric recovery of ortho-images derived from Apollo 15 metric camera imagery is presented to show the validity of the proposed method.

A Dynamic Lunar Spectral Irradiance Data Set for NPOESS/VIIRS Day/Night Band Nighttime Environmental Applications

In anticipation of the first fully calibrated nighttime low-light measurements from the National Polar-orbiting Operational Environmental Satellite System's Visible/Infrared Imager/Radiometer Suite (VIIRS) Day/Night Band (DNB), a simple model has been developed for quantifying the highly variable top-of-atmosphere spectral irradiance (in watts per square meter per micrometer) from Earth's only natural satellite-the Moon. Based on the state-of-the-art in solar source observations, lunar spectral albedo data, and an account for the time-varying Sun/Earth/Moon geometry and lunar phase, the model produces 1-nm resolution irradiance spectra over the interval [0.3, 1.2 mum] for a given date and time. Convolving the spectra with the sensor response function of the VIIRS/DNB allows for the conversion from measurements of upwelling radiance to equivalent lunar reflectance [i.e., 0%-100%]-enabling quantitative nighttime multispectral applications that have heretofore been restricted to the daytime hours for lack of visible reflectance information. In the interest of advancing research in nighttime environments, we present here the development and validation of a lunar spectral irradiance database, supply auxiliary data and tools necessary for computing temporally dependent values, and discuss some of the environmental applications enabled by this utility.

Ten Years of TRMM/VIRS On-Orbit Calibrations and Multiyear Comparisons of VIRS and MODIS

Abstract After 10 years of successful operation of the Tropical Rainfall Measuring Mission (TRMM)/Visible Infrared Scanner (VIRS), based on sensor performance, the authors have reexamined the calibration algorithms and identified several ways to improve the current VIRS level-1B radiometric calibration software. This study examines the trends in VIRS on-orbit calibration results by using lunar measurements to enable separation of the solar diffuser degradation from that of the VIRS Earth-viewing sensor and by comparing the radiometric data with two nearly identical Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on board the NASA Earth Observing System (EOS) Terra and Aqua satellites. For the VIRS, with spectral bands quite similar to several of the MODIS bands, the integrated lunar reflectance data were measured, from January 1998 to March 2007, at phase angles ranging from 0.94° to 121.8°. The authors present trending of the lunar data over periods of 4 yr (Aqua/MODIS), 6 yr (Terra/MODIS), and 10 yr (TRMM/VIRS) and use these observations to examine instrument radiometric stability. The VIRS-measured lunar irradiances are compared with the MODIS-measured lunar irradiances at phase angles around 54°–56°. With the upcoming modified VIRS level-1B version 7 calibration algorithm, the VIRS, along with MODIS, should provide better references for intercalibrating multiple Earth-observing sensors.

Automated detection of lunar craters based on object-oriented approach

The object-oriented approach is a powerful method in making classification. With the segmentation of images to objects, many features can be calculated based on the objects so that the targets can be distinguished. However, this method has not been applied to lunar study. In this paper we attempt to apply this method to detecting lunar craters with promising results. Craters are the most obvious features on the moon and they are important for lunar geologic study. One of the important questions in lunar research is to estimate lunar surface ages by examination of crater density per unit area. Hence, proper detection of lunar craters is necessary. Manual crater identification is inefficient, and a more efficient and effective method is needed. This paper describes an object-oriented method to detect lunar craters using lunar reflectance images. In the method, many objects were first segmented from the image based on size, shape, color, and the weights to every layer. Then the feature of “contrast to neighbor objects” was selected to identify craters from the lunar image. In the next step, by merging the adjacent objects belonging to the same class, almost every crater can be taken as an independent object except several very big craters in the study area. To remove the crater rays diagnosed as craters, the feature of “length/width” was further used with suitable parameters to finish recognizing craters. Finally, the result was exported to ArcGIS for manual modification to those big craters and the number of craters was acquired.

Estimation of the lunar reflectance by ground-based observation using a tunable liquid-crystal filter telescope

Abstract Lunar reflectance data are useful not only for lithological identification of the lunar surface but also for radiometric calibration and determination of exposure time for optical sensors of lunar probes. To gain data on lunar reflectance, we acquired multi-band images (five bands: 650, 750, 900, 950, and 1000 nm) of the lunar surface and those of some standard stars using a liquid-crystal tunable filter (LCTF) telescope located on the peak of Mt. Haleakala (Hawaii, USA). The data obtained indicate that the reflectance data of Clementine UV/VIS is too high and that the correction factor is 0.59±0.06 at 950 nm. Our new reflectance data are available to the public at the web site of one of authors (K.S.). We report here our method of deriving the lunar reflectance images from the ground-based observation with a hyperspectral telescope for the users of our reflectance data. The results suggest that ground-based observation is more suitable for the radiometric calibration of the sensor of a lunar probe than laboratory data.

Four Years of TRMM/VIRS On-Orbit Calibrations and Characterization Using Lunar Models and Data fromTerra/MODIS

Abstract Four years of on-orbit solar calibration data have been used to quantify the temporal degradation of the two reflected solar bands of the Visible and Infrared Scanner (VIRS) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite. Solar calibrations, performed using an onboard solar diffuser, show no significant changes in the VIRS 1.61-μm data. The responsivity (digital counts per radiance unit) of the 0.62-μm band has changed and, as a function of days since 1998, is given by R1(day) = 69.782 − 0.0022 × day, with an annual degradation of 1.15%. Four years of on-orbit lunar measurements were also examined in an attempt to quantify any degradation in the solar diffuser. The integrated lunar reflectance with phase angles ranging from 1.6° to 106° were fit with the lunar photometric model of Hapke. A good fit was made to the 0.62-μm data, but overall, the quality of the data did not support efforts to quantify any diffuser degradation. The quality of the VIRS radiometry was also examined by...

First Results from the On-Orbit Calibrations of the Visible and Infrared Scanner for the Tropical Rainfall Measuring Mission

Abstract This work presents the first on-orbit calibration results using the Moon, the Sun, and cold deep space as inputs to the Visible and Infrared Scanner (VIRS) on board the Tropical Rainfall Measuring Mission (TRMM) satellite. The authors have developed lunar reflectance curves using VIRS data for phase angles ranging from 1.6° to 82°. Comparisons with modeled reflectance curves show that the VIRS lunar data are as predicted. Specifically, the six-parameter model of Helfenstein and Veverka provides a good description of the VIRS 0.62-μm data. The lunar reflectance data will be used to discern long-term changes in VIRS response. Solar calibrations, performed using an onboard solar diffuser, show fluctuations of the VIRS responsivity of less than 1.3% and no indication of any systematic change during 11 months. Using the deep-space calibration implemented via a spacecraft maneuver on three different dates—7 January, 8 January, and 2 September 1998—the authors have measured the dependence of the scan mi...

Lunar reflectivity from Extreme Ultraviolet Explorer imaging and spectroscopy of the full moon

We present new imaging and spectroscopic observations obtained with the Extreme Ultraviolet Explorer (EUVE). Our 200 Å image shows high contrast (33%) and complete albedo reversal, i.e., contrast is reversed relative to the Moon in visible light. The high contrast at 200 Å suggests the potential of the EUV spectral region for surface compositional studies. The 600 Å image is surprisingly bland (<3% contrast). We derive surface reflectivities (geometric albedos) of individual surface regions for the first time with values of 0.11–0.15% at 200 Å, and 2.5% at 600 Å. Reflectivities derived from the medium‐ (MW) and long‐wavelength (LW) spectra (140–380 Å and 280–760 Å) show that lunar reflectivity decreases by a factor of approximately 60 over the 700 to 150 Å range. Our data further suggest that the Moon's brightness vs phase may behave differently than at longer wavelengths, and that surface fluorescence may contribute to the observed EUV brightness.

A test of Radio Interferometry by Lunar reflection

AbstractWe discuss the use of the moon as a passive reflector for radio interferometry experiments with baselines on the order of the radius of the orbit of the moon. Because of the extreme loss in the lunar interferometer path, only exceptionally strong point sources are candidates for this kind of interferometry. As the moon is far from an ideal reflector due to the irregular surface, the data processing necessary to optimize the fringe detectability is rather complicated. What we present here is a very brief summary of a paper describing the lunar interferometer in the Astrophysical Journal (Hagfors, Phillips and Belkora, 1990) and an experiment currently underway at Arecibo to test the lunar interferometer using Jupiter’s strong bursts at 25 MHz as a source. All references pertaining to the lunar interferometer are to be found in the Astrophysical Journal paper; this summary includes references concerning the test of the interferometer at Arecibo.

Radio interferometry by lunar reflections

view Abstract Citations (2) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radio Interferometry by Lunar Reflections Hagfors, T. ; Phillips, J. A. ; Belkora, L. Abstract The use of the moon as a passive reflector for radio interferometry experiments with baselines on the order of the radius of the orbit of the moon is discussed. Because of the extreme loss in the lunar interferometer path, only exceptionally strong point sources are candidates for this kind of interferometry. As the moon is far from an ideal reflector due to the irregular surface, the data processing necessary to optimize the fringe detectability is rather complicated. The optimum processing procedure is given and the signal-to-noise ratio for these processors is computed. Two specific applications are discussed, one being the spatial resolution of Jupiter bursts, the other the resolution of the H2O maser at 22 GHz in Orion. Both experiments are definitely possible with existing (Arecibo) or currently planned telescopes (Green Bank). Publication: The Astrophysical Journal Pub Date: October 1990 DOI: 10.1086/169267 Bibcode: 1990ApJ...362..308H Keywords: Lunar Albedo; Lunar Surface; Radio Echoes; Radio Interferometers; Radio Sources (Astronomy); Data Processing; Interstellar Masers; Signal To Noise Ratios; Spatial Resolution; Water Masers; Astronomy; INTERFEROMETRY; RADIO SOURCES: GENERAL full text sources ADS |

The Near-Space Unwanted RF Environment as Observed Using VHF Lunar Reflections

Man-made terrestrial radio leakage as reflected off the Moon has been observed with the 305-m Aercibo antenna. The nature and intensity of this leakage gives one some indication of the unwanted radiofrequency (RF) environment for operations in space in the 150-500 MHz range. The experiment consisted of observing both on the Moon and on a nearby patch of blank sky (as a way to identify local sources of interference) for three nights at a variety of VHF frequencies. As predicted in a previous model, we find that the military radars and television (TV) transmitters are main contributors. With regard to the question of possible contact with extraterrestrial intelligence, the Earth indeed is revealing itself to any interstellar eavesdropper who uses the equivalent of an Arecibo antenna at distances up to 30 light years, or who uses a Cyclops system (1000 100-m dishes) up to fifteen times farther away.

The limits of correctness

On October 5, 19601, the American Ballistic Missile Early–Warning System station at Thule, Greenland, indicated a large contingent of Soviet missiles headed towards the United States2. Fortunately, common sense prevailed at the informal threat–assessment conference that was immediately convened: international tensions weren’t particularly high at the time. The system had only recently been installed. Kruschev was in New York, and all in all a massive Soviet attack seemed very unlikely. As a result no devastating counter–attack was launched. What was the problem? The moon had risen, and was reflecting radar signals back to earth. Needless to say, this lunar reflection hadn’t been predicted by the system’s designers. Over the last ten years, the Defense Department has spent many millions of dollars on a new computer technology called “program verification” a branch of computer science whose business, in its own terms, is to “prove programs correct”. Program verification has been studied in theoretical computer science departments since a few seminal papers in the 1960s3, but it has only recently started to gain in public visibility, and to be applied to real world problems. General Electric, to consider just one example, has initiated verification projects in their own laboratories: they would like to prove that the programs used in their latest computer–controlled washing machines won’t have any “bugs” (even one serious one can destroy their profit margin)4. Although it used to be that only the simplest programs could be “proven correct” — programs to put simple lists into order, to compute simple arithmetic functions –slow but steady progress has been made in extending the range of verification techniques. Recent papers have reported correctness proofs for somewhat more complex programs, including small operating systems, compilers, and other material of modern system design. 5 What, we do well to ask, does this new technology mean? How good are we at it? For example, if the 1960 warning system had been proven correct (which it was not), could we have avoided the problem with the moon? If it were possible to prove that the programs being written to control automatic launch–on–warning systems were correct, would that mean there could not be a catastrophic accident? In systems now being proposed computers will make launching decisions in a matter of seconds, with no time for any human intervention (let alone for musings about

Comparison of lunar ultraviolet reflectivity with that of terrestrial rock samples

The ultraviolet and visible albedos of a number of terrestrial basalts, gabbros and anorthosites have been investigated over the wavelength range 800 A to 8000 A and compared with previously reported measurements of the lunar albedo. For most of the terrestrial samples the albedo changed only slightly between visible and middle ultraviolet wavelengths in striking contrast to the Moon where the ultraviolet albedo is about a factor of five or ten less than it is in the visible. Some of the lighter coloured terrestrial anorthositic samples were however found to have albedo curves that fairly closely approximate the ultraviolet darkening of the Moon. The general shape of the lunar ultraviolet albedo may be caused by a layer of anorthositic fragments on the Moon such as have been found to be a very abundant component of the Apollo ‘coarse-fines’.

Spectrophotometry (0.3 to 1.1�) of visited and proposed apollo lunar landing sites

The study uses information gained by analysis of the spectral properties of lunar samples in the laboratory, and telescope spectra of over 100 lunar areas, to provide information regarding the composition and mineralogy of each proposed lunar landing site. Attention is given to (1) the presence of pyroxenes which cause an absorption band near 0.95 micron in the lunar reflection spectrum, (2) the proportion of crystalline to glassy material present in the soil which is derived from the slope of the reflectivity curve between 0.4 and 0.7 micron and the strength of the 0.95 micron absorption band, and (3) the presence of Ti(3+) ions in the glasses on the lunar surface, which affects the reflection spectrum at blue and ultraviolet wavelengths.

Reflection Spectra of Lunar Dust Grains with Amorphous Coatings

The suggestion of Bibring et al. (1971) that the low albedos and reddish spectra observed in some lunar fines are caused by a low density amorphous substance which coats the fines is disputed. It is shown that these coatings have only a marginal effect on lunar reflectivity.

Lunar reflectivity at 0.86-centimeter wavelength

Measurement of backscattering of 0.86-cm circularly polarized radiation by 29 regions on the moon. Both circular polarizations were received. At a given angle of incidence, power received in the 'expected' polarization was greater for the highland regions than for the seas by roughly 1 dB. For moderately large angles of incidence phi, this return diminishes more rapidly than cosine phi, although perhaps not as rapidly as it does at longer wavelengths. The cross section of the whole moon is 5 plus or minus 2% of the geometric cross section; about 80% of the cross section is ascribable to diffuse scattering. The polarization ratio for the echoes varies smoothly with the angle of incidence, from 0.7 at the subradar point to 0.4 at 70 deg. The depolarization is the same for marial and highland regions, and at large angles of incidence it is the same as has been found at 23 and 68 cm by other workers.

Time Dependence of Lunar Differential Color

Lunar surface spectral reflectivity variations with time, noting phase angle effects on color contrast

Lunar surface composition and particle size: Implications from laboratory and lunar spectral reflectance data

Lunar albedo and color data are compatible with participate rock of basic composition such as basalt, but not with crystalline acidic rock such as rhyolite, or with rock glass such as obsidian, or pumice. Laboratory experiments suggest that albedo differences on the moon could be accounted for by variations in mean particle size. According to this model there need not be major compositional differences between highland and maria regions; however, compositional inhomogeneities within the basic-rock family are implied by areal color differences within the dark maria. The reddening of lunar features with increasing phase angle and a broad minimum in the lunar reflectance spectrum at 1.0 μ are duplicated in the laboratory with basalt powders.

Mapping of lunar radar reflectivity at 70 centimeters

Radar observations of the lunar surface were made using the 10′ beamwidth antenna at Arecibo, Puerto Rico, at a wavelength of 70cm (430 Mc/s). Resolution of the surface of the order of 20 by 30km was achieved, first, by resolving the echo in time delay and Doppler frequency shift and, second, by using the narrow antenna beamwidth to remove the ambiguity between hemispheres. Echo strengths measured in delay and frequency coordinates were then mapped onto photographs of the moon. The following were determined: (1) The lunar highlands of the southwest quadrant of the moon backscatter 1½ to 2 times as effectively per unit area as the mare regions of the east and northeast quadrants of the moon. (2) The mountain ranges which surround the circular maria backscatter 1½ to 2 times as much power as the adjacent mare regions. (3) Some craters were found to backscatter as much as 10 times as much power as their environs. The craters which had enhanced backscattering were bright under a full moon illumination and were nearly always young.

A Comparison of the Infrared Spectra of the Moon and Simulated Lunar Surface Materials

view Abstract Citations (7) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Comparison of the Infrared Spectra of the Moon and Simulated Lunar Surface Materials Wattson, Richard B. ; Hapke, Bruce W. Abstract Reflection spectra of selected rock powders in the 1-2.5- wavelength range are compared with the Stratoscope II spectrum of Mare Tranquilitatis. The spectra of natural powders are too bright and too flat to match the lunar reflectivity, which increases with wavelength in this range. However, irradiation by 2-keV H+ ions equivalent to approximately 100 years of solar-wind bombardment on the Moon decreased the albedo and reddened the powders markedly in the infrared. Similar effects have been previously observed in the visible. A sample of powdered chondrite was not reddened by irradiation. The infrared reflectivities of the powders are too high even after irradiation, although their visible albedos are similar to the Moon's; a possible explanation is that the radiation-altered layer is optically thick in the infrared on the lunar surface but not on the laboratory samples. Publication: The Astrophysical Journal Pub Date: April 1966 DOI: 10.1086/148610 Bibcode: 1966ApJ...144..364W full text sources ADS |