Earth Science Technology Research Articles

Advanced precipitation Radar antenna: array-fed offset membrane cylindrical reflector antenna

As part of the overall NASA earth science technology research effort, a half-size prototype model of light-weight, dual-frequency and wide-swath scanning antenna for the next generation of spaceborne precipitation radar has recently been developed. It operates radar channels at both 13.6 and 35 GHz for improved rainfall retrieval accuracy. The antenna for proposed spaceborne precipitation radar is an offset parabolic cylindrical reflector fed by two linear arrays. This design is adopted, instead of a double-curved offset reflector, because it provides the required wide scan angle in the cross-track plane at both the Ku and Ka band operating frequencies. To demonstrate the technological readiness of the concept, the focus is on a half-scale model of 2.65 m operating at Ku and Ka band. In this paper, the technology development status on this Advanced Precipitation Radar Antenna will be presented. Design and characterization of the 2.65 m antenna is detailed by presenting the features of various components of the antenna, including simulation of the performance, 2/spl times/166 Ku and 4/spl times/166 Ka element feed array designs and evaluation and the design concept of the membrane reflector. Measurement results of the entire antenna system using a compact range facility will also be summarized.

Earth-science technology needs for the future

Earth-science technology needs for the future

Policy Issues Related to Curriculum Development and Implementation for Gifted Education in Science in Korea

The article examines admission policy issues related to curriculum development and implementation for the gifted education in science at special high schools in Korea. High school admission policies provided a means to identify and select a population of the scientifically gifted with certain characteristics and gave major directions for curriculum development while university admission policies had significant influences on curriculum implementation in special high schools. The admission policies for science high schools in Korea selected a homogeneous group of high achievers in all subject areas while special high schools for the gifted tended to select a heterogeneous group of the scientifically gifted in various areas of science including physics, chemistry, biology, earth science or information technology. University admission policies seemed to function as a parameter to achieve successful curriculum implementation.

Development of a 4–15 μm infrared GaAs hyperspectral QWIP imager

In the on-going evolution of GaAs quantum well infrared photodetectors (QWIPs) we have developed a four band, 640 × 512, 23 μm × 23 μm pixel array which we have subsequently integrated with a linear variable etalon (LVE) filter providing over 200 spectral bands across the 4–15.4 μm wavelength region. This effort was a collaboration between NASA’s Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory (JPL) and the Army Research Laboratory (ARL) sponsored by the Earth Science Technology Office of NASA. The QWIP array was fabricated by graded molecular beam epitaxial (MBE) growth that was specifically tailored to yield four distinct bands (FWHM): Band 1; 4.5–5.7 μm, Band 2; 8.5–10 μm, Band 3; 10–12 μm and Band 4; 13.3–14.8 μm. Each band occupies a swath that comprises 128 × 640 elements. The addition of the LVE (which is placed directly over the array) further divides the four “broad” bands into 209 separate spectral bands ranging in width from 0.02 μm at 5 μm to 0.05 μm at 15 μm. The detector is cooled by a mechanical cryocooler to 46 K. The camera system is a fully reflective, f/4.2, 3-mirror system with a 21° × 25° field of view. The project goals were: (1) develop the 4 band GaAs QWIP array; (2) develop the LVE and; (3) implement a mechanical cryocooler. This paper will describe the efforts and results of this undertaking with emphasis on the overall system characteristics.

Applications of GaAs quantum well infrared photoconductors at the NASA/Goddard Space Flight Center

Prior to 1990 large format, hybridized GaAs quantum well infrared photoconductors (QWIP) arrays had not been fabricated. In a unique collaboration between the Goddard Space Flight Center, ATT/Bell Labs and the Rockwell Science Center we designed and built a 128×128 element GaAs/AlGaAs QWIP array, developed a continuous flow liquid helium cooler/camera system and successfully performed airborne imaging test flights over the Wallops Flight Facility. As a result of work performed at Lockheed Martin of Dallas, Texas a 256×256 QWIP was developed and Goddard obtained a unit for a second-generation camera system. A more compact imaging system was developed which could operate with a liquid nitrogen dewar. This instrument was used as part of the joint NASA/Southern African Fire-Atmosphere Research Initiative campaign to gather airborne terrestrial science information. This system was also used to evaluate the emission/reflectance properties of commercially available pyrgeometers and pyranometers. These radiometers rely on constants for the filter dome and the detector which are key in making absolute measurements. In an effort to improve the optical coupling efficiency and also to develop QWIPs with sensitivity beyond 11 μm a partnership has been established between Goddard and the Army Research Laboratory (ARL). By corrugating the surface of the QWIP array, normal incidence radiation is deflected almost horizontally allowing for absorption in the quantum wells. Most recently, a joint Goddard/Jet Propulsion Laboratory/ARL proposal to develop a four band, hyperspectral, 512×640 QWIP array has been funded by the Earth Science Technology Office of NASA. This three year effort will focus on expanding the integrated QWIP spectral imaging capability, utilizing a new Sunpower, Inc. cryocooler and developing a linear variable etalon to produce the hyperspectral image from 3 to 15.4 μm. The four IR bands are (1) 3–5 μm, (2) 8.5–10 μm, (3) 10–12 μm and (4) 14–15.4 μm. These four bands are spectrally subdivided into approximately 200 bands. This paper will discuss these efforts in general with an emphasis on the system performance.

Introduction to the Special Issue on “Leading Edge of Earth Science Technology”

Introduction to the Special Issue on “Leading Edge of Earth Science Technology”

The Role of Pressure Transient Analysis in Reservoir Characterization - An Integrated Approach

SUMMARY Most reservoirs exhibit complex variations of sand continuity, thickness, structural patterns, and pore space attributes (permeability, porosity, and capillary pressure properties). The most effective way to identify and quantify rock framework and pore-space variations, is through the deliberate and integrated use of engineering and earth-science technology. The development of the pressure derivative technique of well test interpretation, has greatly improve the identification of features that are often not evident on a Horner plot. This paper illustrates, with several field cases, how an adequate model of the reservoir can be diagnosed by complementing the transient response analysis, based on the pressure derivative method, with the existing geological, openhole, core analysis and performance data.

Synergism in Reservoir Management The Geologic Perspective

Improved hydrocarbon recovery can be obtained through the coordinated use of engineering, geology, and geophysics. Particularly in synergistic studies, geologists must be able to identify the rock properties that will be significant to oil and gas recovery. This paper presents an overview of geologic technology and the concepts and principles that guide its use. Introduction Rather than being homogeneous tanks or uniformly layered entities, most reservoirs exhibit complex variations of reservoir continuity and thickness patterns and of pore-space attributes (porosity, permeability, and capillary-pressure properties). The reservoir interval is commonly subdivided vertically and areally into "pay zones" that are separated by impermeable rock units; the pay zones themselves often contain thin shale or tight pay zones themselves often contain thin shale or tight carbonate streaks. Thickness distributions of pay zones may be sheet-like or linear and, within the rock framework, pore-space attributes may vary in a predictable or random manner. It is this complexity of rock framework and pore-space variation that challenges petroleum scientists to apply their technology and experience in reservoir description, with the aim of improving recovery. The best way to identify and quantify rock framework and pore-space variations is through the deliberate and integrated use of engineering and earth-science technology. Reservoir studies are more effective when geologists and engineers determine jointly, at the outset, the course of investigation, the work-area responsibility for each professional on the description team, and the target dates for combining results. Such an approach to reservoir description requires an understanding of the technology used by other professionals and an awareness of the principles and concepts upon which the technology is based. Furthermore, this understanding and awareness will promote the free exchange of ideas - a fundamental facet of synergistic activities. This paper presents an overview of geologic technology and the concepts and principles that guide its use. Four topics are covered. First, the geologic procedures used in reservoir description are presented together with a brief discussion of the emphasis required for different recovery projects. The next two topics deal with the details of the technology and guiding principles and concepts used to describe sandstone and carbonate reservoirs. Finally, synergy needs for the future are discussed. Geologic Activities in Reservoir Studies General Activities The steps commonly followed by the geologists are indicated in Fig. 1, together with some work areas where the geologist needs to combine his efforts with those of the engineer. These steps are listed in their general order of accomplishment, although sometimes it is worthwhile to "look ahead" before completing a particular step. Rock studies involve using cuttings, cores, well logs, and routine core-analysis data to identify the rock types (both potential reservoir and nonreservoir types that make up the reservoir interval) and to interpret the depositional origin of the interval. These data provide fundamental information for predicting reservoir continuity and thickness patterns and variations in pore-space properties. Typical of the information developed in this step properties. Typical of the information developed in this step are core-description graphs and porosity-permeability cross-plots. Framework studies determine the geometric configuration of the trap and the vertical and lateral distribution of the rock types identified previously. JPT P. 761