The Thermal Infrared Sensor (TIRS) on Landsat 8 is the latest thermal sensor in that series of missions. Unlike the previous single-channel sensors, TIRS uses two channels to cover the 10–12.5 micron band. It is also a pushbroom imager; a departure from the previous whiskbroom approach. Nevertheless, the instrument requirements are defined such that data continuity is maintained. This paper describes the design of the TIRS instrument, the results of pre-launch calibration measurements and shows an example of initial on-orbit science performance compared to Landsat 7.
The science-focused mission of the Landsat 8 Thermal Infrared Sensor (TIRS) requires that it have an accurate radiometric calibration. A calibration methodology was developed to convert the raw output from the instrument into an accurate at-aperture radiance. The methodology is based on measurements obtained during component-level and instrument-level characterization testing. The radiometric accuracy from the pre-flight measurements was estimated to be approximately 0.7%. The calibration parameters determined pre-flight were updated during the post-launch checkout period by utilizing the on-board calibration sources and Earth scene data. These relative corrections were made to adjust for differences between the pre-flight and the on-orbit performance of the instrument, thereby correcting large striping artifacts observed in Earth imagery. Despite this calibration correction, banding artifacts (low frequency variation in the across-track direction) have been observed in certain uniform Earth scenes, but not in other uniform scenes. In addition, the absolute calibration performance determined from vicarious measurements have revealed a time-varying error to the absolute radiance reported by TIRS. These issues were determined to not be caused by the calibration process developed for the instrument. Instead, an investigation has revealed that stray light is affecting the recorded signal from the Earth. The varying optical stray light effect is an ongoing subject of evaluation and investigation, and a correction strategy is being devised that will be added to the calibration process.Remote Sens. 2014, 6 8804
The Landsat Data Continuity Mission ('LDCM), a joint NASA and USGS mission, is scheduled for launch in December, 2012. The LRCM instrument payload will consist of the Operational Land Imager (OLI), provided by Ball Aerospace and Technology Corporation (BATC } under contract to NASA and the Thermal Infrared Sensor (TIRS), provided by NASA's Goddard Space Hight Center (GSFC). This paper outlines the design of the TIRS instrument and gives an example of its application to monitoring water consumption by measuring evapotranspiration.Inter Terms-TIRS, LDCM, evapotranspiration I\TROD[ CT1ONAs is implied in the mission name, one element of the LDCM project is to provide continuity with past Landsat sensors. Another element is to provide improvernents in sensors where possible. The Thematic: Mapper (TM), Enhanced Thematic iMapper (ETXl), and Enhanced Thematic Mapper Plus (ETM-) sensors are good examples of this philosophy as the thermal infrared band improved in spatial resolution from 120 to 60 rn for the single-band, whiskbroom-approach systems (See [2] and references therin). While such data have proved important in providing land-use information, volcanic and lire-monitoring, data, and resource management guidance, a dual-band sensor at lower spatial resolution but with improved sensitivity would maintain continuity and provide valuable data for water resource management and agricultural studies. TIRE on LRCM is a 100 meter (I20 meter requirement) spatial resolution push-broorn imager whose two spectral channels, centered at near I0.8 and 12 microns. split the spectral range of the single TM and ETMt thermal band while still providing thermal band data continuity with previous Landsat missions. The push-broom implementation increases s ystem sensitivity by allowing longer integration times than whiskbroom sensors. The two channels allow the use of the split-window" technique to aid in atmospheric correction. The TIRS focal plane operates near 43 K and consists of three Quantum Well Infrared Photodetector (QWIP) arrays to span the 185 km swath width [5]. Infrared filters are used to define the spectral coverage of the two channels. The imaging telescope is a 4-element refractive leas system. A scene select mechanism (SSIvI ) rotates a scene mirror (SM) to change the field of regard from a nadir Earth view to either an on-board blackbody calibrator or a deep space view. The blackbod y is a full aperture calibrator whose temperature may be varied from 270 to 330 K. Figure I shows a model of the TIRS sensor unit with the major elements identified. TIRS DESIGN OVERVIEWIn a pushbroom instrument, an n row by m column 2..D image of a scene is built-up by concatenating; n successive single rove measurements each containin g m pixels. For TIRS on LDCNI, with its 185 knt swath wilh and 100 meter ground sample distance, a single row consists of 1850 pixels (m-1850). Because the orbital motion of the LDC1.1 spacecraft is about 7 kirtrsec it takes approximatel y 0.01 4 second to move the row by 100 meters, and 70 rows of...
Summary TextThe Thermal Infrared Sensor (TIRS) instrument, provided by NASA's Goddard Space Flight Center and the Operational Land Imager (OLI) provided by Ball Aerospace and Technology Corporation (BATC) will form the payload for the Landsat Data Continuity Mission (LDCM). This paper will describe the design, capabilities and status of both the OLI and the TIRS instrument. AbstractThe Landsat Data Continuity Mission (LDCM), a joint NASA and United States Geological Survey (USGS) mission, is scheduled for launch in December, 2012. The LDCM instrument payload will consist of the Operational Land Imager (OLI), provided by Ball Aerospace and Technology Corporation (BATC) under contract to NASA and the Thermal Infrared Sensor (TIRS), provided by NASA's Goddard Space Flight Center (GSFC). This paper will describe the design, capabilities and status of the OLI and TIRS instruments.
The Landsat Data Continuity Mission consists of a two-sensor platform with the Operational Land Imager and Thermal Infrared Sensor (TIRS). Much of the success of the Landsat program is the emphasis placed on knowledge of the calibration of the sensors relying on a combination of laboratory, onboard, and vicarious calibration methods. Rigorous attention to NIST-traceability of the radiometric calibration, knowledge of out-of-band spectral response, and characterizing and minimizing stray light should provide sensors that meet the quality of Landsat heritage. Described here are the methods and facilities planned for the calibration of TIRS which is a pushbroom sensor with two spectral bands (10.8 and 12 micrometer) and the spatial resolution 100 m with 185-km swath width. Testing takes place in a vacuum test chamber at NASA GSFC using a recently-developed calibration system based on a 16-aperture black body source to simulate spatial and radiometric sources. A two-axis steering mirror moves the source across the TIRS field while filling the aperture. A flood source fills the full field without requiring movement of beam providing a means to evaluate detector-to-detector response effects. Spectral response of the sensor will be determined using a monochromator source coupled to the calibration system. Knowledge of the source output will be through NIST-traceable thermometers integrated to the blackbody. The description of the calibration system, calibration methodology, and the error budget for the calibration system shows that the required 2% radiometric accuracy for scene temperatures between 260 and 330 K is well within the capabilities of the system.
We present computational methods for simulating electrical conduction in cardiac ventricles on parallel machines. We used the network model approach to describe the tissue geometry and biophysically detailed models of ion currents and membrane transporters in cardiac ventricular myocytes. Simulations of biophysically detailed ionic models with anatomically detailed tissue geometries are computationally very expensive. We investigated the use of high performance computers to reduce execution time. Experiments have shown that we can adapt and optimize our existing models of electrical activity in heart tissue for the High Performance Computers. The solution was implemented on the IBM R p690, a shared memory machine and on a cluster of workstations, a distributed memory machine. An efficient algorithm was designed to partition the data and to pass messages between processors using Message Passing Interface (MPI). The algorithm was highly scalable to the problem size as well as the number of processors used, and could easily be ported to other parallel architectures. We were able to achieve speedup of up to 13.5 on the p690 and 27 on the cluster of workstations. Using the method developed, the simulated pattern of electrical activation agreed with the experimental data.
The Landsat series of satellites provides the longest running continuous data set of moderate-spatial-resolution imagery beginning with the launch of Landsat 1 in 1972 and continuing with the1999 launch of Landsat 7 and current operation of Landsats 5 and 7[1]. The Landsat Data Continuity Mission (LDCM) will continue this program into a fourth decade providing data that are keys to understanding changes in land-use changes and resource management. LDCM consists of a two-sensor platform comprised of the Operational Land Imager (OLI) and Thermal Infrared Sensors (TIRS). A description of the applications and design of the TIRS instrument is given as well as the plans for calibration and characterization. Included are early results from preflight calibration and a description of the inflight validation.
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