A reflectance spectra-based approach to mapping salt fields using PCA-fused Landsat TM data

In this paper a method based on in situ measured reflectance spectra was developed for accurately mapping salt fields in the Taibei Salt Farm in Lianyungang City of East China. After radiometric correction and geometric rectification, six multispectral ETM+ bands were fused with the panchromatic band via principal components analysis (PCA). The fused data were used to map salt fields in the farm. Salt fields were mapped 91.95% correctly in comparison with ground statistics from raw multispectral bands. This accuracy level rose to 96.4% with the use of the panchromatic band (15 m resolution). However, PCA-fused data produced the highest accuracy of 98.8%. At the zone level, coarse resolution data resulted in an accuracy of 98.93% for crystallization ponds, but only 82.68% for condensation ponds. Use of the panchromatic band alone improved the accuracy for condensation ponds but decreased the accuracy for crystallization and evaporation ponds. Results derived from PCA-fused data are highly consistent with the ground statistics at a discrepancy between 0.35% for evaporation zone and 1.80% for condensation zone. It is concluded that a fine spectral resolution is important to separation of ponds of a varying salt content while a fine spatial resolution is important to their mapped area. Ponds of a lower salt content can be mapped more accurately from fused data than from raw spectral bands.     

The Burst Alert Telescope (BAT) on the SWIFT Midex Mission

he burst alert telescope (BAT) is one of three instruments on the Swift MIDEX spacecraft to study gamma-ray bursts (GRBs). The BAT first detects the GRB and localizes the burst direction to an accuracy of 1–4 arcmin within 20 s after the start of the event. The GRB trigger initiates an autonomous spacecraft slew to point the two narrow field-of-view (FOV) instruments at the burst location within 20–70 s so to make follow-up X-ray and optical observations. The BAT is a wide-FOV, coded-aperture instrument with a CdZnTe detector plane. The detector plane is composed of 32,768 pieces of CdZnTe (4×4×2 mm), and the coded-aperture mask is composed of ∼52,000 pieces of lead (5×5×1 mm) with a 1-m separation between mask and detector plane. The BAT operates over the 15–150 keV energy range with ∼7 keV resolution, a sensitivity of ∼10⁻⁸ erg s⁻¹ cm⁻², and a 1.4 sr (half-coded) FOV. We expect to detect > 100 GRBs/year for a 2-year mission. The BAT also performs an all-sky hard X-ray survey with a sensitivity of ∼2 m Crab (systematic limit) and it serves as a hard X-ray transient monitor.     

Benefits and challenges of voluntary contribution to GEOSS

The vision of the Global Earth Observation System of Systems (GEOSS) is the achievement of societal benefits through voluntary contribution and sharing of data, metadata and products at no or minimum cost. Such undertakings, where contribution provides positive externalities, benefiting contributors and non-contributors alike, are often described as ‘social dilemmas’, usually resulting in small levels of voluntary contribution. We investigate the benefits and challenges of voluntary contribution to GEOSS, surveying economic and game theoretic literature and examining how the concepts of social dilemmas apply to the provision of GEOSS. We conduct an exploratory survey among individuals involved in the Group on Earth Observation (GEO) to understand their perception of voluntarily contribution. Even though contribution to GEOSS was perceived as rather low, e.g. because of a perceived lack of funds, commitment or organization, survey respondents also perceived many (exclusive) benefits of contribution, e.g. networking, visibility for their work or collaborating with motivated individuals. To increase participation, respondents suggested increasing financial support and raising awareness of GEOSS. We conclude that communicating the efficacy of individuals' contributions, the personal benefits of contribution and strengthening of group identity and knowledge about fellow participants' work can constitute incentives for future voluntary contribution. This could be facilitated by an externally established institution providing a framework for cooperation, or by institutions, agreements or frameworks agreed upon by contributors themselves.     

Calibration and flight results for the Ares I-X 5-hole probe

Flight and calibration results are presented for the Ares I-X 5-hole probe. The probe is calibrated by using a combination of wind tunnel, CFD, and other numerical modeling techniques. This is then applied to the probe flight data and comparisons are made between the vanes and 5-hole probe. Using this and other data it is shown the probe was corrupted by water rendering that measurement unreliable.     

Deriving a sea surface temperature record suitable for climate change research from the along-track scanning radiometers

We describe the approach to be adopted for a major new initiative to derive a homogeneous record of sea surface temperature for 1991–2007 from the observations of the series of three along-track scanning radiometers (ATSRs). This initiative is called (A)RC: (Advanced) ATSR Re-analysis for Climate. The main objectives are to reduce regional biases in retrieved sea surface temperature (SST) to less than 0.1 K for all global oceans, while creating a very homogenous record that is stable in time to within 0.05 K decade⁻¹, with maximum independence of the record from existing analyses of SST used in climate change research. If these stringent targets are achieved, this record will enable significantly improved estimates of surface temperature trends and variability of sufficient quality to advance questions of climate change attribution, climate sensitivity and historical reconstruction of surface temperature changes. The approach includes development of new, consistent estimators for SST for each of the ATSRs, and detailed analysis of overlap periods. Novel aspects of the approach include generation of multiple versions of the record using alternative channel sets and cloud detection techniques, to assess for the first time the effect of such choices. There will be extensive effort in quality control, validation and analysis of the impact on climate SST data sets. Evidence for the plausibility of the 0.1 K target for systematic error is reviewed, as is the need for alternative cloud screening methods in this context.     

Climatic variations in the outgoing longwave radiation of the past decade as observed from NOAA polar orbiting satellites

Components of the earth radiation budget have been calculated on a regular basis since June 1974 (except for a 10 month gap in data in 1978) based on measurements by the scanning radiometers and the advanced very high resolution radiometers on the operational NOAA polar orbiting satellites. A new base set of monthly and seasonal averages of outgoing longwave radiation has been prepared by NOAA's Climate Analysis Center (CAC) for the entire period of record through November 1983. Anomalies relative to these new normals have now been constructed for each month and season in the entire record.In this presentation, some of the more prominent anomalies of outgoing longwave radiation over the past decade are discussed. A major concentration is on the tropics and subtropics where there have been very substantial radiation variations associated with major shifts in convective cloudiness accompanying El Niño/Southern Oscillation events.     

Bacillus subtilis spores on artificial meteorites survive hypervelocity atmospheric entry: implications for Lithopanspermia

An important but untested aspect of the lithopanspermia hypothesis is that microbes situated on or within meteorites could survive hypervelocity entry from space through Earth's atmosphere. The use of high-altitude sounding rockets to test this notion was explored. Granite samples permeated with spores of Bacillus subtilis strain WN511 were attached to the exterior telemetry module of a sounding rocket and launched from White Sands Missile Range, New Mexico into space, reaching maximum atmospheric entry velocity of 1.2 km/s. Maximum recorded temperature during the flight was measured at 145 degrees C. The surfaces of the post-flight granite samples were swabbed and tested for recovery and survival of WN511 spores, using genetic markers and the unique DNA fingerprint of WN511 as recovery criteria. Spore survivors were isolated at high frequency, ranging from 1.2% to 4.4% compared with ground controls, from all surfaces except the forward-facing surface. Sporulation-defective mutants were noted among the spaceflight survivors at high frequency (4%). These experiments constitute the first report of spore survival to hypervelocity atmospheric transit, and indicate that sounding rocket flights can be used to model the high-speed atmospheric entry of bacteria-laden artificial meteorites.     

基于Modelica和Dymola的航空发动机燃气发生器的建模与性能仿真

基于对压气机、涡轮与燃烧室共同工作条件的分析,建立了1种快速简便的单轴燃气发生器性能仿真模型;用Modelica语言和Dymola编译器实现了单轴燃气发生器的性能仿真,验证了该模型的有效性。结果表明:该模型能够模拟单轴燃气发生器的性能,并能实现非设计转速小流量工况下的性能仿真。     

基于Modelica和Dymola的压气机系统的建模与仿真方法

基于压气机性能方程推导出一种新的压气机级的数学模型，并在这一模型基础上用Modelica语言和Dymola编译器建立了计算机仿真模型，编成了压气机系统仿真程序。还描述了压气机仿真程序建模系统和面向对象的体系结构，介绍了压气机系统特性分析的应用例子，并进行了仿真验证。结果表明，采用建立的仿真模型能够用来模拟压气机性能。     

基于Modelica和Dymola的航空发动机建模与性能仿真

本文介绍了Modelica/Dymola软件的主要特点,航空发动机模块划分的原则和方法,以及利用Modelica/Dymola软件开发的航空发动机通用模型库中主要部件的建模方法,并采用己建立的部件模型,搭建了双轴涡扇发动机的系统级模型,对其起动过程进行了仿真.结果表明,仿真结果符合实际情况,该模型库对于航空发动机的概念设计和初步设计具有重要意义和实用价值.