A ten-year-long peak of the X-ray flux from the burster 4U 1724-307 in the globular cluster Terzan 2: Evolution of the donor star or the influence of a third star?

We analyze observations of the burster 4U 1724-307 (1E 1724-3045) in the globular cluster Terzan 2 from 1971 until 2001. Uhuru, OSO-8, Einstein, and EXOSAT observations are used. In addition, we analyze data from the TTM telescope onboard the Mir/Kvant observatory and from the ASM and PCA instruments onboard the RXTE observatory. Based on PCA/RXTE scanning observations, we have mapped the sky in the Galactic-center region. The derived light curve of the burster 4U 1724-307 shows the source to be variable on a time scale of 30 years: over the first 20 years of observations (1970–1990), the source flux was approximately constant, while in the 1990s, it rose over ～5 years and declined over approximately the same period, approaching its original value. We discuss several scenarios to explain the behavior of the light curve, including the evolution of the mass outflow rate from the donor-star surface, the episodic appearance of a second source in the globular cluster, and gravitational microlensing. As one of the scenarios, we also consider the possibility that the passage of a third star affects the accretion rate in the binary 4U 1724-307. We show that if this event is responsible for the 10-year-long rise in the luminosity of the burster 4U 1724-307, then the size and period of this binary can be estimated.     

Using SNAP for Galactic &; extragalactic astronomy

SNAP, the SuperNova Acceleration Probe, is planned as a space-based telescope designed specifically to search for and monitor cosmological supernovae and weak lensing. In this paper we propose some other mission objectives which are of great importance in the fields of Galactic and extragalactic astronomy and which can be done as by-products with the same instrumentation and survey strategy as currently proposed for the main SNAP mission.     

The tools of climate adaptation policy: analysing instruments and instrument selection

Governments have a key role to play in the process of climate adaptation, through the development and implementation of public policy. Governments have access to a diverse array of instruments that can be employed to adapt their operations and influence the behaviour of individuals, organizations, and other governments. However, the choice of policy instrument is political, because it affects the distribution of benefits and costs, and entrenches institutional procedures and resources that are difficult to redeploy. This article identifies four key governing resources that governments employ in the service of adaptation and analyses these resources using criteria drawn from the policy studies literature. For each category, specific policy instruments are described, and examples are provided to illustrate how they have been used in particular jurisdictions. The article also discusses instrument selection, focusing on trade-offs among the instrument attributes, processes for setting the stage for instrument choice, jurisdictional constraints on instrument selection, and ways to avoid negative vertical and horizontal policy interplay.

Policy relevance

Adaptation is a nascent field of public policy, and courses of action to reduce vulnerability and build adaptive capacity are in their infancy. This article contributes to policy development and analysis by identifying the range of policy instruments available to governments and analysing concrete ways in which they are employed to implement adaptation policy objectives. Taking stock of these adaptation tools and comparing their behavioural assumptions and attributes helps to illuminate potential policy options, and to evaluate their technical viability, political acceptability, and economic feasibility. Providing examples of how these instruments have been implemented successfully in other jurisdictions offers ideas and lessons for public officials.     

The short history of infrared space telescopes

While astronomical telescopes developed rather slowly over the last four centuries, infrared telescopes made a fast career in only four decades from high mountains to aircraft, balloons and satellites. They cover the huge wavelength region from 1 to 350 μ m and have uncovered the cold and dust hidden universe. While until today all infrared space telescopes had diameters of <1 m, cooled infrared observatories with 3.5 to 6.5m mirrors will be sent into heliocentric orbits at L2 within the next few years (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The trend,seasonal cycle,and sources of tropospheric NO<Subscript>2</Subscript> over China during 1997–2006 based on satellite measurement

The characteristics of spatial and temporal distribution of tropospheric NO2 column density concentration over China are presented, on the basis of measurements from the satellite instruments GOME and SCIAMACHY. From these observations, monthly averaged tropospheric NO2 variations are determined for the period of 1997 to 2006. The trend and seasonal cycle are also investigated. The possible source of tropospheric NO2 over megacity area is discussed in this paper. The results show a large growth of tropospheric NO2 over eastern China, especially above the industrial areas with a fast economical growth, such as, Yangtze Rive Delta region and Pearl River Delta region because of the prominent anthropogenic activity. There is a rapid increase of tropospheric NO2 over megacities in China. For instance, Shanghai had a linear significant increase in NO2 columns of ～20% per year (reference year 1997) in the period of 1997-2006, which is the rapidest increase among all the selected cities. The seasonal pattern of the NO2 concentration shows a difference between the east and west in China. In the eastern part of China, an expected winter maximum in seasonal cycle is found because of the prominent anthropogenic activity and meteorological conditions. In the western part this cycle shows a NO2 maximum in summer time, which is attributed to natural emissions, especially soil emissions and lightning. A quickly increasing vehicle population may contribute to the increase of tropospheric NO2 over megacities in China for the remarkable correlation for vehicle population with tropospheric NO2.     

The trend, seasonal cycle, and sources of tropospheric NO_2 over China during 1997―2006 based on satellite measurement

The characteristics of spatial and temporal distribution of tropospheric NO2 column density concen-tration over China are presented,on the basis of measurements from the satellite instruments GOME and SCIAMACHY.From these observations,monthly averaged tropospheric NO2 variations are deter-mined for the period of 1997 to 2006.The trend and seasonal cycle are also investigated.The possible source of tropospheric NO2 over megacity area is discussed in this paper.The results show a large growth of tropospheric NO2 over eastern China,especially above the industrial areas with a fast eco-nomical growth,such as,Yangtze Rive Delta region and Pearl River Delta region because of the prominent anthropogenic activity.There is a rapid increase of tropospheric NO2 over megacities in China.For instance,Shanghai had a linear significant increase in NO2 columns of ～20% per year(ref-erence year 1997) in the period of 1997―2006,which is the rapidest increase among all the selected cities.The seasonal pattern of the NO2 concentration shows a difference between the east and west in China.In the eastern part of China,an expected winter maximum in seasonal cycle is found because of the prominent anthropogenic activity and meteorological conditions.In the western part this cycle shows a NO2 maximum in summer time,which is attributed to natural emissions,especially soil emissions and lightning.A quickly increasing vehicle population may contribute to the increase of tropo-spheric NO2 over megacities in China for the remarkable correlation for vehicle population with tropospheric NO2.     

Sensor Calibration in Support for NOAA’s Satellite Mission

Sensor calibration, including its definition, purpose, traceability options, methodology, complexity, and importance, is examined in this paper in the context of supporting NOAA’s satellite mission. Common understanding of sensor calibration is essential for the effective communication among sensor vendors, calibration scientists, satellite operators, program managers, and remote sensing data users, who must cooperate to ensure that a nation’s strategic investment in a sophisticated operational environmental satellite system serves the nation’s interest and enhances the human lives around the world. Examples of calibration activities at NOAA/NESDIS/ORA are selected to further illustrate these concepts and to demonstrate the lessons learned from the past experience.     

Imaging of structures in the high-latitude ionosphere: model comparisons

The tomographic reconstruction technique generates a two-dimensional latitude versus height electron density distribution from sets of slant total electron content measurements (TEC) along ray paths between beacon satellites and ground-based radio receivers. In this note, the technique is applied to TEC values obtained from data simulated by the Sheffield/UCL/SEL Coupled Thermosphere/Ionosphere/Model (CTIM). A comparison of the resulting reconstructed image with the input modelled data allows for verification of the reconstruction technique. All the features of the high-latitude ionosphere in the model data are reproduced well in the tomographic image. Reconstructed vertical TEC values follow closely the modelled values, with the F-layer maximum density (NmF2) agreeing generally within about 10%. The method has also been able successfully to reproduce underlying auroral-E ionisation over a restricted latitudinal range in part of the image. The height of the F2 peak is generally in agreement to within about the vertical image resolution (25 km).     

Analysis of hot springs and associated deposits in Yellowstone National Park using ASTER and AVIRIS remote sensing

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Airborne Visible/IR Image Spectrometer (AVIRIS) data were used to characterize hot spring deposits in the Lower, Midway, and Upper Geyser Basins of Yellowstone National Park from the visible/near infrared (VNIR) to thermal infrared (TIR) wavelengths. Field observations of these basins provided the critical ground-truth for comparison with the remote sensing results. Fourteen study sites were selected based on diversity in size, deposit type, and thermal activity. Field work included detailed site surveys such as land cover analysis, photography, Global Positioning System (GPS) data collection, radiometric analysis, and VNIR spectroscopy. Samples of hot spring deposits, geyser deposits, and soil were also collected. Analysis of ASTER data provided broad scale characteristics of the hot springs and their deposits, including the identification of thermal anomalies. AVIRIS high spectral resolution short-wave infrared (SWIR) spectroscopy provided the ability to detect hydrothermally altered minerals as well as a calibration for the multispectral SWIR ASTER data. From the image analysis, differences in these basins were identified including the extent of thermal alteration, the location and abundance of alteration minerals, and a comparison of active, near-extinct, and extinct geysers. We determined the activity level of each region using a combination of the VNIR-SWIR-TIR spectral differences as well as the presence of elevated temperatures, detected by the TIR subsystem of ASTER. The results of this study are applicable to the exploration of extinct mineralized hydrothermal deposits on both Earth and Mars.     

编码与测绘仪器

编码作为现代信息学的重要基础 ,在测绘仪器领域有着越来越广泛的应用。本文对其在电子水准仪、电子经纬仪和GPS上的应用进行了较为深入的探讨。