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The HeliNet project has been funded by the European Union for the period 2000-2002, and concerns the development of a network of stratospheric platforms for telecommunications, navigation and remote sensing. The first year of activity has lead to the definition of the long-tern system objectives, as well as preliminary specifications of the platform structure and payloads. In particular, in this paper we give an overview of the current status of the project. We address system integration issues, which involve interfacing the payloads and the aeronautical structure; moreover, we report current activities in a few major application domains, namely navigation and remote sensing.

The international community agrees that the new technology based on the use of Unmanned Air Vehicles High Altitude Very long Endurance (UAV-HAVE) could play an important role for the development of remote sensing and telecommunication applications. A UAV-HAVE vehicle can be described as a low- cost flying infrastructure (compared with satellites) optimized for long endurance operations at an altitude of about 20 km. Due to such features, its role is similar to satellites, with the major advantages of being less expensive, more flexible, movable on demand, and suitable for a larger class of applications. According to this background, Politecnico di Torino is involved as coordinator in an important project named HeliNet, that represent one of the main activities in Europe in the field of stratospheric platforms, and is concerned with the development of a network of UAV-HAVE aircraft. A key point of this project is the feasibility study for the provision of several services, namely traffic monitoring, environmental surveillance, broadband communications and navigation. This paper reports preliminary results on the HeliNet imaging system and its remote sensing applications. In fact, many environmental surveillance services (e.g. regional public services for agriculture, hydrology, fire protection, and more) require very high-resolution imaging, and can be offered at a lower cost if operated by a shared platform. The philosophy behind the HeliNet project seems to be particularly suitable to manage such missions. In particular, we present a system- level study of possible imaging payloads to be mounted on- board of a stratospheric platform to collect Earth observation data. Firstly, we address optical payloads such as multispectral and/or hyperspectral ones, which are a very short-term objective of the project. Secondly, as an example of mid-term on-board payload, we examine the possibility to carry on the platform a light-SAR system. For both types of payload, we show how intelligent processing algorithms for environmental data can be run on-board in real-time, in order to make data analysis and transmission more effective, and designed to match the constrains imposed by a UAV-HAVE platform. The results of the study lead to the conclusion that the stratospheric technology seems to be a competitive infrastructure (with respect to the satellites) in the remote sensing scenarios described above.

This paper deals with the automatic detection of Objects of Interest (OOIs) in SAR (Synthetic Aperture Radar) still images. A particular scenario in which a Light-SAR is part of the payload for HALE (High Altitude Long Endurance) platform, named Heliplat, currently under development at the Politecnico di Torino. This unmanned, solar powered aeronautical vehicle is especially tailored for operations at altitudes between 15 and 25 Km with a potential endurance of weeks to months. It could provide a wide range of potential applications within telecommunication and remote sensing: in this paper a particular surveillance application, the reconnaissance over sea regions, has been focused.

This paper deals with the problem of automatic recognition of music. Segments of digitized music are processed by means of a Continuous Wavelet Transform, properly chosen so as to match the spectral characteristics of the signal. In order to achieve a good time-scale representation of the signal components a novel wavelet has been designed suited to the musical signal features. particular care has been devoted towards an efficient implementation, which operates in the frequency domain, and includes proper segmentation and aliasing reduction techniques to make the analysis of long signals feasible. The method achieves very good performance in terms of both time and frequency selectivity, and can yield the estimate and the localization in time of both the fundamental frequency and the main harmonics of each tone. The analysis is used as a preprocessing step for a recognition algorithm, which we show to be almost independent on the instrument reproducing the sounds. Simulations are provided to demonstrate the effectiveness of the proposed method.

In this paper the use of permutations as a mean of spreading the spectrum of the frequency channels in a general multicarrier modulation scheme is presented. Our first objective is to demonstrate how signature waveforms suitable for multiple access communications can be generated by applying permutation transformations to orthogonal channels generated with filterbanks or DFT techniques. The second objective is to motivate the use of such techniques as a mean of achieving immunity to timing errors, which can cause severe Adjacent Channel Interference in multicarrier systems, due to large spectral overlap among adjacent channels. An efficient implementation of the interleaver implementing the considered permutations is also described.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.