Landsat-5 Thematic Mapper reflective-band radiometric stability

Four aspects of the radiometry of the Landsat-5 Thematic Mapper were characterized over the 20+ year mission lifetime for the six reflective bands: relative gain (the radiometric gain of each detector within a band relative to other detectors in that band), bias, performance of the Internal Calibrator (IC) system, and noise. Relative gain was found to be stable or slowly varying and could be described as a linear function of time for most detectors; the maximum change was approximately 0.5%/year. These relative gain characterizations provide an alternate source of destriping information that, in general, compares favorably with that obtained from currently used scene-specific methods. Much of the variability in instrument bias levels was found to be related to temperature effects; long-term changes in bias levels were less than 0.5 DN overall. The lamp-based IC system, though stable over the short term, showed both individual lamp phenomena and changes in overall behavior that complicated the ability to monitor the system's stability. Using the best behaved lamp and some assumptions about expected lamp behavior, characterization of response with a simple model was achieved through the year 2000. The model shows an initial 5% to 10% decay in response over the first three years of operation, depending on the band. Noise levels and signal-to-noise ratio in the instrument appear to be stable throughout the lifetime.     

Landsat thematic mapper reflective-band radiometric artifacts

Radiometric "artifacts" are known to be present to varying degrees in the reflective-band imagery from both Landsat-4 and Lansat-5 Thematic Mappers (TMs). The most common artifacts are known as scan-correlated shift (SCS), memory effect (ME), and coherent noise (CN). The characterization and correction of these artifacts has been performed for both the Landsat-4 and Lansat-5 TMs. SCS is a sudden shift in bias that can be as large as 2 DN. However, this artifact can be accurately quantified and easily removed from imagery using a line-by-line bias subtraction. ME causes the detector response to undershoot after a sudden transition from a bright target to a dark target. For large transitions, this can cause a 2% radiometric error. This artifact can be removed through a spatial filtering operation. Lastly, CN is a periodic pattern that is most often seen in homogeneous portions of TM imagery. The amplitude of this noise artifact is quite small, less than 0.5 DN. While CN has been accurately characterized, a correction procedure is not recommended, due to the small amplitude of this artifact. Recommendations are given for proper processing of TM imagery to remove the effects of these artifacts.     

Landsat-5 TM and Landsat-7 ETM+ absolute radiometric calibration using the reflectance-based method

The reflectance-based method of vicarious calibration has been used for the absolute radiometric calibration of the Landsat series of sensors since the launch of Landsat-4. The reflectance-based method relies on ground-based measurements of the surface reflectance and atmospheric conditions at a selected test site nearly coincident with the imaging of that site by the sensor of interest. The results of this approach are presented here for Landsat-5 Thematic Mapper (TM) and Landsat-7 Enhanced Thematic Mapper Plus (ETM+). The data have been collected by two groups, one from the University of Arizona and the other from South Dakota State University. The test sites used by the University of Arizona group for this work are the Railroad Valley Playa, Lunar Lake Playa, and Roach Lake Playa all of which are in Nevada, Ivanpah Playa in California, and White Sands Missile Range, New Mexico. The test site for the South Dakota State group is a grass site in Brookings, SD. The gains derived from dates using these sites spanning the period from 1984 to 2003 are presented for TM and for the period of 1999 to 2003 for ETM+. Differences between the two groups are less than the combined uncertainties of the methods, and the data are thus treated as a single dataset. The results of these vicarious data indicate that there has been no degradation apparent in TM since 1995 and in ETM+ since launch. Agreement between the reflectance-based results and the preflight calibration of ETM+ is better than 4% in all bands, and the standard deviation of the average difference indicates a precision of the reflectance-based method on the order of 3%.     

Landsat sensor performance: history and current status

The current Thematic Mapper (TM) class of Landsat sensors began with Landsat-4, which was launched in 1982. This series continued with the nearly identical sensor on Landsat-5, launched in 1984. The final sensor in the series was the Landsat-7 Enhanced Thematic Mapper Plus (ETM+), which was carried into orbit in 1999. Varying degrees of effort have been devoted to the characterization of these instruments and data over the past 22 years. Extensive short-lived efforts early in the history, very limited efforts in the middle years, and now a systematic program for continuing characterization of all three systems are apparent. Currently, both the Landsat-5 TM and the Landsat-7 ETM+ are operational and providing data. Despite 20+ years of operation, the TM on Landsat-5 is fully functional, although downlinks for the data are limited. Landsat-7 ETM+ experienced a failure of its Scan Line Corrector mechanism in May 2003. Although there are gaps in the data coverage, the data remain of equivalent quality to prefailure data. Data products have been developed to fill these gaps using other ETM+ scenes.     

Landsat-5 TM reflective-band absolute radiometric calibration

The Landsat-5 Thematic Mapper (TM) sensor provides the longest running continuous dataset of moderate spatial resolution remote sensing imagery, dating back to its launch in March 1984. Historically, the radiometric calibration procedure for this imagery used the instrument's response to the Internal Calibrator (IC) on a scene-by-scene basis to determine the gain and offset of each detector. Due to observed degradations in the IC, a new procedure was implemented for U.S.-processed data in May 2003. This new calibration procedure is based on a lifetime radiometric calibration model for the instrument's reflective bands (1-5 and 7) and is derived, in part, from the IC response without the related degradation effects and is tied to the cross calibration with the Landsat-7 Enhanced Thematic Mapper Plus. Reflective-band absolute radiometric accuracy of the instrument tends to be on the order of 7% to 10%, based on a variety of calibration methods.     

FFT Selective and Adaptive Filtering for Removal of Systematic Noise in ETM+ Imageodesy Images

The images of imageodesy derived from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) image pairs across an earthquake event exhibit severe horizontal and vertical striping noise patterns that obscure the desired information relating to earthquake-induced terrain displacements. The periodic noise patterns were analyzed to reveal that the principal cause of these errors was due to the two-way across-track scanning mechanism of the ETM+ instrument in relation to the minor shift of the satellite orbits between two acquisitions. We first focused on the design of selective filters pinpointing the noise frequencies of horizontal striping based on frequency-domain analysis, via fast Fourier transform (FFT). As a result, the horizontal striping patterns have been successfully eliminated, but meanwhile the systematic varying frequency nature of the more complicated wavy vertical striping patterns is better revealed. This has led to the successful design of an adaptive FFT frequency filtering mechanism based on the function characterizing the relationship between angular speed of a scanner imaging system and its corresponding line speed on the curved surface of the Earth. Finally, the horizontal and vertical striping patterns have been successfully eliminated by semiautomatic selective and adaptive filtering procedures without subduing the key information of coseismic displacement     

LANDSAT-4 MSS And Thematic Mapper Data Quality And Information Content Analysis

Landsat-4 Thematic Mapper and Multispectral Scanner data were analyzed to obtain information on data quality and information content. Geometric evaluations were performed to test band-to-band registration accuracy. Thematic Mapper overall system resolution was evaluated using scene objects which demonstrated sharp high contrast edge responses. Radiometric evaluation included detector relative calibration, effects of resampling, and coherent noise effects. Information content evaluation was carried out using clustering, principal components, transformed divergence separability measure, and numerous supervised classifiers on data from Iowa and Illinois. A detailed spectral class analysis (multispectral classification) was carried out on data from the Des Moines, Iowa area to compare the information content of the MSS and TM for a large number of scene classes.     

Landsat-7 ETM+ on-orbit reflective-band radiometric stability and absolute calibration

Launched in April 1999, the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) instrument is in its sixth year of operation. The ETM+ instrument has been the most stable of any of the Landsat instruments. To date, the best onboard calibration source for the reflective bands has been the Full Aperture Solar Calibrator, a solar-diffuser-based system, which has indicated changes of between 1% to 2% per year in the ETM+ gain for bands 1-4 and 8 and less than 0.5%/year for bands 5 and 7. However, most of this change is believed to be caused by changes in the solar diffuser panel, as opposed to a change in the instrument's gain. This belief is based partially on vicarious calibrations and observations of "invariant sites", hyperarid sites of the Sahara and Arabia. Weighted average slopes determined from these datasets suggest changes of 0.0% to 0.4% per year for bands 1-4 and 8 and 0.4% to 0.5% per year for bands 5 and 7. Absolute calibration of the reflective bands of the ETM+ is consistent with vicarious observations and other sensors generally at the 5% level, though there appear to be some systematic differences.     

Characterization of LANDSAT-4 MSS And TM Digital Image Data

Engineering analyses conducted to assess image data quality are described and results are presented for the Landsat-4 Multispectral Scanner (MSS) and Thematic Mapper (TM). Also, coincident data from the two sensors are compared. Macroscopic studies addressed trends and characteristics of full frames of data, while ?microscopic? studies assessed differences between individual detector responses. Raw data, radiometrically corrected data, and fully corrected data were analyzed, as well as special calibration data. The Landsat-4 MSS was found to produce data of high quality, comparable to previous Landsats, except for a low-level coherent noise effect which is unique to the current sensor. Radiometric relationships between Landsat-2 and -3 MSS's and the Landsat-4 MSS were established through empirical analysis of simultaneously acquired data. The TM was found to produce image data of very good spatial resolution and overall good radiometric data quality, showing improvements over MSS. Radiometric equalization of detector responses was found to be close to the theoretical limit of quantization error, except for two relatively low-amplitude artifacts. One is a difference in response that depends on the direction of mirror scan. This produces scan-angle effects superimposed on scene-related effects. The second is a tendency for level shifts to occur between mirror scans at random times but with correlations between detector responses. Two forms or patterns of level shift were identified, corresponding to four system noise states. Preliminary correction models and/or procedures have been developed and recommended for further evaluation.     

Revised Radiometric Calibration Technique for LANDSAT-4 Thematic Mapper Data

A technique for the radiometric correction of Landsat-4 Thematic Mapper (TM) data was proposed by the Canada Centre for Remote Sensing (CCRS) in 1982, and two reports defining the method and discussing preliminary results were presented by CCRS at the Landsat-4 Scientific Characterization Early Results Symposium [1] and [2]. Subsequent detailed observations of raw image data, raw radiometric calibration data, and background measurements extracted from the raw data stream on High Density Tape have highlighted in the proposed method, major shortcomings, which if left uncorrected, can cause severe radiometric striping in the output product. Observations presented here show that there are random fluctuations in the background level for spectral band 1 of magnitudes ranging from 2 to 3.5 digital numbers (DN), depending on detector number. Similar variability is observed in all the other reflective bands, but with smaller magnitude in the range 0.5 to 2.5 DN. More significantly, it is shown how measurements of the dc background level can be correlated with variations in both image data background and calibration samples. The effect on both raw data and on data corrected using the earlier proposed technique is explained, and the correction required for these factors as a function of individual scan line number for each detector is described. It is shown how the revised technique, which includes corrections for a line-dependent offset in addition to the scene-dependent gain and offset, can be incorporated into an operational environment.     

Cross calibration of the Landsat-7 ETM+ and EO-1 ALI sensor

As part of the Earth Observer 1 (EO-1) Mission, the Advanced Land Imager (ALI) demonstrates a potential technological direction for Landsat Data Continuity Missions. To evaluate ALI's capabilities in this role, a cross-calibration methodology has been developed using image pairs from the Landsat-7 (L7) Enhanced Thematic Mapper Plus (ETM+) and EO-1 (ALI) to verify the radiometric calibration of ALI with respect to the well-calibrated L7 ETM+ sensor. Results have been obtained using two different approaches. The first approach involves calibration of nearly simultaneous surface observations based on image statistics from areas observed simultaneously by the two sensors. The second approach uses vicarious calibration techniques to compare the predicted top-of-atmosphere radiance derived from ground reference data collected during the overpass to the measured radiance obtained from the sensor. The results indicate that the relative sensor chip assemblies gains agree with the ETM+ visible and near-infrared bands to within 2% and the shortwave infrared bands to within 4%.     

中巴地球资源一号卫星红外多光谱扫描仪、交叉定标方法研究

建立CBERS—1上搭载的红外多光谱扫描仪(IRMSS)与FY—1C通道4及Landsat-7上ETM 波段6多星星载热红外遥感仪器交叉定标的算法模型，利用美国Landsat-7上搭载的ETM 红外通道6和FY—1C通道4分别对IRMSS热红外通道进行交叉定标，得到二组定标结果．相同地标点对比分析结果表明，二个定标结果得到的目标点亮度温度相对偏差为1．2K；IRMSS交叉定标结果与Landsat-7ETM 热红外通道在轨定标结果独立样本对比分析结果，均方根偏差为1．6K．     

Landsat-5 Thematic Mapper outgassing effects

A periodic 3% to 5% variation in detector response affecting both image and internal calibrator (IC) data has been observed in bands 5 and 7 of the Landsat-5 Thematic Mapper. The source for this variation is thought to be an interference effect due to buildup of an ice-like contaminant film on a ZnSe window, covered with an antireflective coating (ARC), of the cooled Dewar containing these detectors. Periodic warming of the dewar is required in order to remove the contaminant and restore detector response to an uncontaminated level. These effects in the IC data have been characterized over four individual outgassing cycles using thin-film models to estimate transmittance of the window/ARC and ARC/contaminant film stack throughout the instrument lifetime. Based on the results obtained from this modeling, a lookup table procedure has been implemented that provides correction factors to improve the calibration accuracy of bands 5 and 7 by approximately 5%.     

An energy detection receiver for non-coherent IR-UWB

A non-coherent receiver for impulse radio ultra-wide band(IR-UWB)is presented.The proposed receiver front-end consists of a high gain LNA,a high frequency detector and an intermediate frequency(IF)amplifier to amplify the recovered signal and drive an external test instrument.To meet the requirements of high gain and a low noise figure(NF)under moderate power consumption for the LNA,capacitor cross coupled(CCC)and current reuse techniques were adopted.The detector consists of a squarer and an integrator.The overall circuit consumes 41.2mA current with a supply voltage of 1.8 V at a 400 MHz pulse rate.The resulting energy efficiency is 0.19 nJ/pulse.A chip prototype is implemented in 0.18-μm CMOS.The die area is 2.1×1.4 mm~2 and the active area is 1.7×0.98 mm~2.     

Analysis And Processing of LANDSAT-4 Sensor Data Using Advanced Image Processing Techniques And Technologies

Techniques have been developed or improved to calibrate, repair, geometrically correct, and extract information from Landsat-4 satellite data. Statistical techniques to correct data radiometry have been evaluated and have minimized striping and banding. It is shown that unless these statistical techniques are used, striping will result even with perfect calibration parameters. Algorithms have been developed to replace data from failed detectors and to reduce coherent noise. The Landsat-4 data have been geometrically corrected to conform to a 1:100 000 map reference to an accuracy of about 41 m. The data were then recorded onto film, and image products produced that can serve as low-cost accurate map products. To decrease the dimensionality of the Landsat-4 data, principal component transformation of the data to four significant new bands was performed, and the results compared with latest available land use maps. The transformation is useful for land use analysis and in delineating vegetation anomalies which appear to reflect areas underlain by altered serpentinite. A range of image processing systems have been used to process the satellite data, including general purpose, special purpose, and personal computers. These systems are described, along with their processing performance. Index Terms-Digital Image Processing, Thematic Mapper, Multispectral Scanner, Calibration, Geometric Correction, Mapping, Digital Terrain, Enhancement, Noise Removal, Personal Computer, Entropy, Principal Components, Banding, Striping, Information Extraction, Geology, Land Use.     

Atmospheric correction of Landsat ETM+ land surface imagery. I.Methods

To extract quantitative information from the Enhanced Thematic Mapper-Plus (ETM+) imagery accurately, atmospheric correction is a necessary step. After reviewing historical development of atmospheric correction of Landsat Thematic Mapper (TM) imagery, the authors present a new algorithm that can effectively estimate the spatial distribution of atmospheric aerosols and retrieve surface reflectance from ETM+ imagery under general atmospheric and surface conditions. This algorithm is therefore suitable for operational applications. A new formula that accounts for adjacency effects is also presented. Several examples are given to demonstrate that this new algorithm works very well under a variety of atmospheric and surface conditions     

An Algorithm for Computing the Number of Distinct Spectral Vectors in Thematic Mapper Data

A computationally efficient method was developed to compute the number of distinct spectral vectors and their frequency of occurrence in Landsat-4 Thematic Mapper (TM) data. The algorithm first partitions the image into spectrally disjoint subsets and then computes the frequency distribution of distinct spectral vectors within each subset from a multidimensional histogram. The overall frequency distribution is tabulated by accumulating the results from each subset. The number of distinct spectral vectors could be used as a measure of potential storage compaction of alternate data representations for data compression, or as a measure of information content in the comparison of spectral band combinations and/or spatial resolutions for an image. Results from processing three 512 X 512 pixel Landsat-4 TM images and one Landsat-4 Multispectral Scanner (MSS) image are presented as examples. An algorithm for computing the frequency distribution of distinct spectral vectors in MSS data is given in the Appendix.     

Landsat-4/5 Band 6 relative radiometry

Relative radiometric responses for the thematic mapper (TM) band 6 data from Landsat-4 and Landsat-5 were analyzed, and an algorithm has been developed that significantly reduces the striping in Band 6 images due to detector mismatch. The TM internal calibration system as originally designed includes a DC restore circuit, which acts as a feedback system designed to keep detector bias at a constant value. There is a strong indication that the DC restore circuitry implemented in Band 6 does not function as it had been designed to. It operates as designed only during a portion of the calibration interval and not at all during acquisition of scene data. This renders the data acquired during the calibration shutter interval period virtually useless for correction of the individual responses of the four detectors in Band 6. It was observed and statistically quantified that the relative response of each of the detectors to the band average is stable over the dynamic range and throughout the lifetime of the instrument. This allows an alternate approach to relative radiometric correction of TM Band 6 images     

Evaluation and Comparison of the IRS-P6 and the Landsat Sensors

The Indian Remote Sensing Satellite (IRS-P6), also called ResourceSat-1, was launched in a polar sun-synchronous orbit on October 17, 2003. It carries three sensors: the high-resolution Linear Imaging Self-Scanner (LISS-IV), the medium-resolution Linear Imaging Self-Scanner (LISS-III), and the Advanced Wide-Field Sensor (AWiFS). These three sensors provide images of different resolutions and coverage. To understand the absolute radiometric calibration accuracy of IRS-P6 AWiFS and LISS-III sensors, image pairs from these sensors were compared to images from the Landsat-5 Thematic Mapper (TM) and Landsat-7 Enhanced TM Plus (ETM+) sensors. The approach involves calibration of surface observations based on image statistics from areas observed nearly simultaneously by the two sensors. This paper also evaluated the viability of data from these next-generation imagers for use in creating three National Land Cover Dataset (NLCD) products: land cover, percent tree canopy, and percent impervious surface. Individual products were consistent with previous studies but had slightly lower overall accuracies as compared to data from the Landsat sensors.     

Noise Output and Noise Figure of Biased Millimeter-Wave Detector Diodes

The behavior of a dc biased millimeter-wave detector diode was investigated by theoretical analysis and experimental measurement. The results indicate that because of the nonlinearity of the diode, shot noise appearing across the diode increases with dc biasing. For the same reason conversion gain of the detector increases with bias. The increase in gain is faster than the increase in noise for a certain range of bias current. Thus the noise figure of the diode detector and its minimum detectable signal are decreased.