Tsuneo Matsunaga

A temperature and emissivity separation algorithm for Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scanner on NASAs Earth Observing System (EOS)-AM1 satellite (launch scheduled for 1998) will collect five bands of thermal infrared (TIR) data with a noise equivalent temperature difference (NE/spl Delta/T) of /spl les/0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTERs TES algorithm hybridizes three established algorithms, first estimating the normalized emissivities and then calculating emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES should be able to recover temperatures within about /spl plusmn/1.5 K and emissivities within about /spl plusmn/0.015. Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations. The main sources of uncertainty in the output temperature and emissivity images are the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTERs precision, calibration, and atmospheric compensation.

The global distribution of pure anorthosite on the Moon

It has been thought that the lunar highland crust was formed by the crystallization and floatation of plagioclase from a global magma ocean, although the actual generation mechanisms are still debated. The composition of the lunar highland crust is therefore important for understanding the formation of such a magma ocean and the subsequent evolution of the Moon. The Multiband Imager on the Selenological and Engineering Explorer (SELENE) has a high spatial resolution of optimized spectral coverage, which should allow a clear view of the composition of the lunar crust. Here we report the global distribution of rocks of high plagioclase abundance (approaching 100 vol.%), using an unambiguous plagioclase absorption band recorded by the SELENE Multiband Imager. If the upper crust indeed consists of nearly 100 vol.% plagioclase, this is significantly higher than previous estimates of 82–92 vol.% (refs 2, 6, 7), providing a valuable constraint on models of lunar magma ocean evolution.

Long-Lived Volcanism on the Lunar Farside Revealed by SELENE Terrain Camera

We determined model ages of mare deposits on the farside of the Moon on the basis of the crater frequency distributions in 10-meter-resolution images obtained by the Terrain Camera on SELENE (Selenological and Engineering Explorer) (Kaguya). Most mare volcanism that formed mare deposits on the lunar farside ceased at ∼3.0 billion years ago, suggesting that mare volcanism on the Moon was markedly reduced globally during this period. However, several mare deposits at various locations on the lunar farside also show a much younger age, clustering at ∼2.5 billion years ago. These young ages indicate that mare volcanism on the lunar farside lasted longer than was previously considered and may have occurred episodically.

Temperature and emissivity separation from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images

The ASTER scanner on NASAs EOS-AM1 satellite (launch: 1998) will collect five channels of TIR data with an NE(Delta) T of less than or equal to 0.3 degrees Kelvin to estimate surface kinetic temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTERs TES algorithm hybridizes three established algorithms, first estimating the temperature by the normalized emissivity method, and then using it to calculate emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast (min-max difference: MMD) of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES can recover temperatures within about plus or minus 1.5 degrees Kelvin, and emissivities within about plus or minus 0.015. Limitations arise from the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTERs precision, calibration and atmospheric correction. Improvements of TES before launch will focus on refining the MMD relationship.

Curie point depth in northeast Japan and its correlation with regional thermal structure and seismicity

Heat flow measurements are high on the back arc side and low on the forearc side of the Tohoku arc, but convective heat transfer in volcanic areas affects the heat flow measurements, complicating the determination of the thermal structure from heat flow measurements alone. Curie point depths deduced from previous magnetic analyses show a sudden change of the Curie isotherm between the volcanic front and the Japan Trench. A magnetic belt extends from west Hokkaido to the eastern limit of Tohoku. The location is west of and parallel to the Cretaceous subduction zone. To determine the geometry of the source of the magnetic belt, detailed magnetic analyses were carried out using forward modeling and recently developed spectral analysis techniques. The magnetic analyses indicate that sources of the magnetic belt extend to significant depths. The result reveals that the Curie isotherm varies from 10 km in the back arc to 20 km or deeper at the eastern limit of Tohoku. The boundary between seismic and aseismic zones in the overriding plate correlates with the inferred Curie isotherm, indicating that seismicity in the overriding plate is related to temperature.

Vicarious calibration of ASTER thermal infrared bands

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on the Terra satellite has five bands in the thermal infrared (TIR) spectral region between 8-12 /spl mu/m. The TIR bands have been regularly validated in-flight using ground validation targets. Validation results are presented from 79 experiments conducted under clear sky conditions. Validation involved predicting the at-sensor radiance for each band using a radiative transfer model, driven by surface and atmospheric measurements from each experiment, and then comparing the predicted radiance with the ASTER measured radiance. The results indicate the average difference between the predicted and the ASTER measured radiances was no more than 0.5% or 0.4 K in any TIR band, demonstrating that the TIR bands have exceeded the preflight design accuracy of <1 K for an at-sensor brightness temperature range of 270-340 K. The predicted and the ASTER measured radiances were then used to assess how well the onboard calibration accounted for any changes in both the instrument gain and offset over time. The results indicate that the gain and offset were correctly determined using the onboard blackbody, and indicate a responsivity decline over the first 1400 days of the Terra mission.

Performance and scientific objectives of the SELENE (KAGUYA) Multiband Imager

The Multiband Imager (MI) is one of the 14 instruments for the Japanese SELENE (KAGUYA) mission. Goal of the SELENE (KAGUYA) mission is to understand origin and evolution of the Moon by obtaining global element and mineral compositions, topological structure, gravity field of the whole Moon, and electromagnetic and particle environment of the Moon. MI is designed to be a high-resolution multiband imaging camera with a spatial resolution in visible bands of 20 m and a spatial resolution in near-infrared bands of 62 m from the 100 km SELENE (KAGUYA) orbit altitude. The MI flight model has been manufactured and integrated. MTF, viewing vector, over-all sensibility, sensor linearity and electrical noise level (S/N estimation test) were measured, and the results indicate that the MI will provide sufficient MTF and low-noise data, just as estimated in the MI design phase. Operation and data analyses plans have been established, and related tools and algorithms have been developed and checked. One of MI scientific objectives is to investigate small but scientifically very important areas such as crater central peaks and crater walls and to investigate magnesian anorthosites.

ASTER preflight and inflight calibration and the validation of Level 2 products

Describes the preflight and inflight calibration approaches used for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The system is a multispectral, high-spatial resolution sensor on the Earth Observing Systems EOS-AM1 platform. Preflight calibration of ASTER uses well-characterized sources to provide calibration and preflight round-robin exercises to understand biases between the calibration sources of ASTER and other EOS sensors. These round-robins rely on well-characterized, ultra-stable radiometers. An experiment field in Yokohama, Japan, showed that the output from the source used for the visible and near-infrared (VNIR) subsystem of ASTER may be underestimated by 1.5%, but this is still within the 4% specification for the absolute, radiometric calibration of these bands. Inflight calibration will rely on vicarious techniques and onboard blackbodies and lamps. Vicarious techniques include ground-reference methods using desert and water sites. A recent joint field campaign gives confidence that these methods currently provide absolute calibration to better than 5%, and indications are that uncertainties less than the required 4% should be achievable at launch. The EOS-AM1 platform will also provide a spacecraft maneuver that will allow ASTER to see the Moon, allowing further characterization of the sensor. A method for combining the results of these independent calibration results is presented. The paper also describes the plans for validating the Level 2 data products from ASTER. These plans rely heavily upon field campaigns using methods similar to those used for the ground-reference, vicarious calibration methods.

Lack of Exposed Ice Inside Lunar South Pole Shackleton Crater

The inside of Shackleton Crater at the lunar south pole is permanently shadowed; it has been inferred to hold water-ice deposits. The Terrain Camera (TC), a 10-meter-resolution stereo camera onboard the Selenological and Engineering Explorer (SELENE) spacecraft, succeeded in imaging the inside of the crater, which was faintly lit by sunlight scattered from the upper inner wall near the rim. The estimated temperature of the crater floor, based on the crater shape model derived from the TC data, is less than ∼90 kelvin, cold enough to hold water-ice. However, at the TCs spatial resolution, the derived albedo indicates that exposed relatively pure water-ice deposits are not on the crater floor. Water-ice may be disseminated and mixed with soil over a small percentage of the area or may not exist at all.

Vicarious Calibration of the GOSAT Sensors Using the Railroad Valley Desert Playa

Japans Greenhouse Gases Observing Satellite (GOSAT) was successfully launched into a sun-synchronous orbit on January 23, 2009 to monitor global distributions of carbon dioxide ( CO2) and methane (CH4). GOSAT carries two instruments. The Thermal And Near-infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) measures reflected radiances in the 0.76 μm oxygen band and in the weak and strong CO2 bands at 1.6 and 2.0 μm. The TANSO Cloud and Aerosol Imager (TANSO-CAI) uses four spectral bands at 0.380, 0.674, 0.870, and 1.60 μm to identify clear soundings and to provide cloud and aerosol optical properties. Vicarious calibration was performed at Railroad Valley, Nevada, in the summer of 2009. The site was chosen for its flat surface and high spectral reflectance. In situ measurements of geophysical parameters, such as surface reflectance, aerosol optical thickness, and profiles of temperature, pressure, and humidity, were acquired at the overpass times. Because the instantaneous field of view of TANSO-FTS is large (10.5 km at nadir), the spatially limited reflectance measurements at the field sites were extrapolated to the entire footprint using independent satellite data. During the campaign, six days of measurements were acquired from two different orbit paths. Spectral radiances at the top of the atmosphere were calculated using vector radiative transfer models coupled with ground in situ data. The agreement of the modeled radiance spectra with those measured by the TANSO-FTS is within 7%. Significant degradations in responsivity since launch have been detected in the short-wavelength bands of both TANSO-FTS and TANSO-CAI.