Space debris is becoming a very important and urgent problem for present and future space activities. For that reason many public and private Institutions in the world are being involved in order to monitor and control the debris population increase and to understand which facilities can be used for improving the surveillance and tracking capabilities. In this framework in 2014 we performed some preliminary observations in a beam parking, CW mode and a bistatic configuration, with a transmitter of 4 kW of the Italian Air Force and the SRT (Sardinia Radio Telescope) a 64 meters radiotelescope used as a receiver. We performed the observations in P band at 410 MHz, receiving the signal diffused from some debris of different sizes and distances in LEO orbit, in order to understand the performances and capabilities of the system. In this article we will describe the results of this observations campaign, the simulation work done for preparing it, the RCS (radar cross section) observed, the level of the received signals, the Doppler measurements, and the work we are doing for developing a new and higher performing digital back end, able to process the data received.
Proc. SPIE. 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII
KEYWORDS: Principal component analysis, Zinc, Fourier transforms, Interference (communication), Field programmable gate arrays, Space telescopes, Signal processing, Galactic astronomy, Signal detection, Stochastic processes
SETI, the Search for ExtraTerrestrial Intelligence, is the search for radio signals emitted by alien civilizations living in the Galaxy. Narrow-band FFT-based approaches have been preferred in SETI, since their computation time only grows like N*lnN, where N is the number of time samples. On the contrary, a wide-band approach based on the Kahrunen-Lo`eve Transform (KLT) algorithm would be preferable, but it would scale like N*N. In this paper, we describe a hardware-software infrastructure based on FPGA boards and GPU-based PCs that circumvents this computation-time problem allowing for a real-time KLT.
Existing radio receivers have a very low noise temperature. To further increase the observation speed, the new generation
of radio receivers use a multi-beam focal plane array (FPA) together with wide bandwidth. In this article, we present the
front-end and cryogenic design of the 7-beam FPA double linear polarization receiver for the 64-m primary focus of the
Sardinia Radio Telescope. At the end of this article, we show the simulated performances of the front-end receiver and
the measurements of the down-conversion section.
Radio Frequency Interferences (RFI) represents one of the major issues especially in single-dish low frequency radioastronomic observations. Several solutions have been investigated to face the problem. Among them a wide-band digital spectrometer is used together to a RFI monitoring station placed close to the radio-telescope and eventually supported by a RFI mobile laboratory. In this paper a system combining such as approaches is described. The first one is a wide-band FFT spectrometer designed for RFI purposes, then the second consists of a station dedicated to RF environment monitoring. Advantages and drawbacks of this hybrid approach will be shown.
The noise temperature of existing radio telescope receivers has actually achieved very low values. In any case, there are other practical ways to increase the observational speed of a single dish antennas without using longer integration time: observe with multi-beam and large bandwidth receiver. In this paper we present the front end and the cryogenic dewar design of the 5 beams FPA double linear polarization receiver for the primary focus of the 64 m Sardinia Radio Telescope.
Radio astronomical observations are ordinarily aimed at reaching a specific scientific goal. Radio telescopes are equipped with a certain number of receivers and back-ends, and the choice of the most suitable receiver/back-end combination in order to best match the scientific application of interest is up to the astronomer. However, the opportunity to process the incoming signal, simultaneously, with different back-ends, thus providing different observational 'points of view', may indeed provide additional scientific results. In this paper, we describe a system, developed for the Sardinia Radio Telescope (SRT), which allows the observer to take profit of such a capability.
We present a project aimed at realizing an Italian aperture array demonstrator constituted by prototypical Vivaldi antennas designed to operate at radio frequencies below 500 MHz. We focus on an array composed of a core plus a few satellite phased-array stations to be installed at the Sardinia Radio Telescope (SRT) site. The antenna elements are mobile and thus it will be possible to investigate the performance in terms of both uv-coverage and synthesized resolution resulting from different configurations of the array.
The Sardinia Radio Telescope (SRT) is a new 64-metre, Gregorian-shaped antenna built in Sardinia (Italy). It
is designed to carry out observations up to 100 GHz.
The telescope is provided with six focal positions: primary, Gregorian and four beam-waveguide foci. This
paper describes the project of the servo system which allows the focus and receiver selection during the instrument
setup. This system also operates, at the observation stage, the compensation of some of the stucture deformations
due to gravity, temperature variations and other environmental effects.
We illustrate the system features following a bottom-up approach, analysing all the project layers ranging
from low-level systems, as the hardware controls, to the design and implementation of high-level software, which
is based on the distributed objects ACS (ALMA Common Software) framework.
Particular focus will be put on the links among the hierarchical levels of the system, and on the solutions
adopted in order to guarantee that the control of the servo system is abstracted from the underlying hardware.
The Sardinia Radio Telescope (SRT) is a new 64-meter shaped antenna designed to carry out observations up to 100
GHz. This large instrument has been built in Sardinia, 35 km north of Cagliari, and is now facing the technical
commissioning phase. This paper describes the architecture, the implementation solutions and the development status of
NURAGHE, the SRT control software. Aim of the project was to produce a software which is reliable, easy to keep up to
date and flexible against other telescopes. The most ambitious goal will be to install NURAGHE at all the three italian
radio telescopes, allowing the astronomers to access these facilities through a common interface with very limited extra
effort. We give a description of all the control software subsystems (servo systems, backends, receivers, etc.) focusing on
the resulting design, which is based on the ACS (Alma Common Software) patterns and comes from linux-based, LGPL,
Object-Oriented development technologies. We also illustrate how NURAGHE deals with higher level requirements,
coming from the telescope management or from the system users.
The Digital Base Band Converter project developed in the last decade produced a general architecture and a
class of boards, firmware and software, giving the possibility to build a general purpose back-end system for
VLBI or single-dish observational activities. Such approach suggests the realization of a digital radio system,
i.e. a receiver with conversion not realized with analogue techniques, maintaining only amplification stages in
the analogue domain. This solution can be applied until a maximum around 16 GHz, the present limit for the
instantaneous input band in the latest version of the DBBC project, while in the millimeter frequency range this
maximum limit of 0.5-2 GHz of the previous versions allows the intermediate frequency to be processed in the
A description of the elements developed in the DBBC project is presented, with their use in different environments.
The architecture is composed of a PC controlled mainframe, and of different modules that can be
combined in a very flexible way in order to realize different instruments. The instrument can be expanded or
retrofitted to meet increasing observational demands. Available modules include ADC converters, processing
boards, physical interfaces (VSI and 10G Ethernet).
Several applications have already been implemented and used in radioastronomic observations: a DDC (Direct
Digital Conversion) for VLBI observations, a Polyphase Digital Filter Bank, and a Multiband Scansion
Spectrometer. Other applications are currently studied for additional functionalities like a spectropolarimeter,
a linear-to-circular polarization converter, a RFI-mitigation tool, and a phase-reference holographic tool-kit.