Satellite

A new algorithm is formulated for retrieving hourly time series of surface hydrometeorological variables including net radiation, sensible heat flux, and near-surface air temperature aided by hourly visible images from the Geostationary Operational Environmental Satellite (GOES) and in situ observations of mean daily air temperature. The algorithm is based on two unconventional, recently developed methods: the maximum entropy production model of surface heat fluxes and the half-order derivative–integral model that has been tested previously. The close agreement between the retrieved hourly variables using remotely sensed input and the corresponding field observations indicates that this algorithm is an effective tool in remote sensing of the earth system.

This paper presents the detailed design and the key system performance results of a comprehensive laboratory demonstrator for a broadband Ka-band multi-beam satellite system exploiting the new DVB-S2 standard with adaptive coding and modulation (ACM). This complete demonstrator allows in-depth verification and optimization of the ACM techniques applied to large satellite broadband networks, as well as complementing and confirming the more theoretical or simulation-based findings published so far. It is demonstrated that few ACM configurations (in terms of modulation and coding) are able to efficiently cope with a typical Ka-band multi-beam satellite system with negligible capacity loss. It is also demonstrated that the exploitation of ACM thresholds with hysteresis represents the most reliable way to adapt the physical layer configuration to the spatial and time variability of the channel conditions while avoiding too many physical layer configuration changes. Simple ACM adaptation techniques, readily implementable over large-scale networks, are shown to perform very well, fulfilling the target packet-error rate requirements even in the presence of deep fading conditions. The impact of carrier phase noise and satellite nonlinearity has also been measured. Copyright © 2009 John Wiley & Sons, Ltd.

The L2, 3 x-ray emission of Cu metal has been measured using monochromatic synchrotron radiation. The self-absorption effect in the spectra is shown to be very small in our experimental geometry. From the quantitative analysis of spectra recorded at different excitation energies, the L3/L2 emission intensity ratio and the partial Auger width are extracted. High-energy satellite features on the L3 emission line are separated by a subtraction procedure.

Spread spectrum code-division multiple-access (CDMA) systems are currently considered as very attractive alternatives to the more familiar FDMA and TDMA systems, especially in the presence of multipath fading and external interference. The problem of code selection in a CDMA system with a finite number of users is addressed in this paper. A simple and efficient method for the selection of finite code sets with relatively high processing gain from Gold and Kasami code families of relatively large sizes is described in detail. Selected code sets of period 63 are presented along with their overall average performance parameters for different number of users.

The use of communication satellites as a possible way of offering broadband island interconnectivity appears to be a very attractive option, as it will enable the provision of an all-digital, transparent service to a number of ATM islands spanning a wide area, accommodating efficiently a variety of traffic demands. The CATALYST Project (RACE II/R2074) is an attempt to demonstrate the applicability and compatibility of satellite technology with the terrestrial BISDN. In this paper we present an overview of the project and focus on an initial study of the expected user performance through the CATALYST network. Our analysis is based upon mathematical and simulation models and describes the end-system to end-system transfer delay for given message lengths. The protocol profiles assume a mix of Novell NetWare and Network File System client/server architectures, which are supported by either the IEEE 802.3/Ethernet or fibre distributed data interface LANs, which are themselves linked via LAN/ATM/satellite interface units. Areas of further investigation, and the implication of our analysis on the actual network architecture, are discussed.

One of the first steps of feature extraction is edge detection. There are various methods for edge detection such as sobel operator, log method and canny operator. These methods have disadvantages such as create noise and discontinues edge and image smoothing. With the notice of the daily growth multi spectral images processing and describe of these images have become very important. Because of the existence of many details of these images, necessity to robust algorithms caused to present a method to extract feature of an object. In this article An improve method for edge detection has been purposed. In this method edge is detected by morphology’s operator and their combination and with the use of various structure elements of images in satellite and remote sensing.

We comment on some statements in a recent paper by Paolozzi and Ciufolini concerning certain remarks raised by us on the realistic accuracy obtainable in testing the general relativistic Lense–Thirring effect in the gravitational field of the Earth with the newly launched LARES satellite together with the LAGEOS and LAGEOS II spacecraft in orbit for a long time. The orbital configuration of LARES is different from that of the originally proposed LAGEOS-3. Indeed, while the latter one should have been launched to the same altitude of LAGEOS (i.e. about hL=5890 km) in an orbital plane displaced by 180° with respect to that of LAGEOS (IL=110°, IL3=70°), LARES currently moves at a much smaller altitude (about hLR=1440 km) and at a slightly different inclination (ILR=69.5°). As independently pointed out in the literature by different authors, the overall accuracy of a LARES–LAGEOS–LAGEOS II Lense–Thirring test may be unfavorably impacted by the lower altitude of LARES with respect to the expected ≈1% level claimed by Ciufolini et al. because of an enhanced sensitivity to the low-degree even zonal geopotential coefficients inducing orbital precessions competing with the relativistic ones. Concerning the previous tests performed with the combined nodes of only LAGEOS and LAGEOS II, an independent analysis recently appeared in the literature indirectly confirms that the total uncertainty in them is likely far from being as little as 10%.

The possibilities of finer longitude control of a geostationary satellite are studied with a view to providing insight into the problem of co-location of satellites. It is shown that for a three-axis stabilized satellite such as INSAT-1B, placed close to an equilibrium longitude, the propellant expenditure for satellite attitude control is considerably larger than that required for longitude drift control. An experiment was conducted on INSAT-1B in which the forces arising from the attitude control thrusters are optimally used to counteract the force due to the solar radiation pressure thereby reducing the perturbations on the orbital eccentricity vector. This is accomplished by suitably switching between the redundant attitude control thrusters located in the positive and negative roll faces of the satellite. The extent to which the effects of the solar radiation pressure are nullified is quantitatively estimated from the observed behaviour of the eccentricity vector. Without any recurrent propellant expenditure it is shown that it is possible to restrict the longitudinal excursions to nearly half of the normally allocated ±0·1° longitude band.

The need to transmit or store satellite images is growing rapidly with the development of modern communications and new imaging systems. The goal of compression is to facilitate the storage and transmission of large images on the ground with high compression ratios and minimum distortion. In this work, we present a new coding scheme for satellite images. At first, the image will be downloaded followed by a fast Fourier transform FFT. The result obtained after FFT processing undergoes a scalar quantization (SQ). The results obtained after the quantization phase are encoded using entropy encoding. This approach has been tested on satellite image and Lena picture. After decompression, the images were reconstructed faithfully and memory space required for storage has been reduced by more than 80%