Abstract. We describe the technological concept and the first-light results of a 1024-channel spectrometer based on field programmable gate array (FPGA) hardware. This spectrometer is the prototype for the seven beam L-band receiver to be installed at the Effelsberg 100-m telescope in autumn 2005. Using "of-the-shelf" hardware and software products, we designed and constructed an extremely flexible Fast-Fourier-Transform (FFT) spectrometer with unprecedented sensitivity and dynamic range, which can be considered prototypical for spectrometer development in future radio astronomy.
In this paper we present the first high resolution SAR measurements performed in the lower terahertz region with the MIRANDA-300 system. The millimeter wave FMCW radar is operated at 300 GHz and provides a bandwidth of more than 40 GHz leading to a range resolution of a few millimeters. With an output power of around 5 mW over the complete bandwidth the system is mainly designed for short range applications up to several hundreds of meters. The capability of the radar has also been investigated in ISAR measurements. The presented results demonstrate the high image quality and the richness of details
In this paper we present an interference detection toolbox consisting of a high dynamic range Digital Fast-Fourier-Transform spectrometer (DFFT, based on FPGA-technology) and data analysis software for automated radio frequency interference (RFI) detection. The DFFT spectrometer allows high speed data storage of spectra on time scales of less than a second. The high dynamic range of the device assures constant calibration even during extremely powerful RFI events. The software uses an algorithm which performs a two-dimensional baseline fit in the time-frequency domain, searching automatically for RFI signals superposed on the spectral data. We demonstrate, that the software operates successfully on computer-generated RFI data as well as on real DFFT data recorded at the Effelsberg 100-m telescope. At 21-cm wavelength RFI signals can be identified down to the 4-sigma level. A statistical analysis of all RFI events detected in our observational data revealed that: (1) mean signal strength is comparable to the astronomical line emission of the Milky Way, (2) interferences are polarised, (3) electronic devices in the neighbourhood of the telescope contribute significantly to the RFI radiation. We also show that the radiometer equation is no longer fulfilled in presence of RFI signals.Comment: 12 pages, 16 figures, accepted for publication in Astron. Note
The capability of imaging and surveying ground areas with airborne and spaceborne sensors has a very high priority in many applications, both in the civilian and military sectors. One of the most essential uses of this capability is in disaster monitoring, where up-to-date, reliable images and data are vital for the undertaking and coordinating of rescue actions. Sensors in space are very accurate but typically have a long revisit time, and thus their use for continuous monitoring is limited. Manned aircrafts equipped with optical, infrared, and synthetic aperture radar (SAR) are costly, and their operation in poor weather conditions (like heavy storms) are limited due to concerns over pilot safety. Unmanned aerial vehicles (UAV) are ideal candidates for the safe and cheap surveillance and imaging of such areas. They can provide continuous monitoring at very low cost, be deployed very quickly, and pose no risk of the loss of life in the case of a platform malfunction caused by heavy weather conditions, technical problems, or human error. The disadvantage of small, unmanned platforms is that they only offer limited space for payloads and have a low electrical power supply. This lays down the conditions for the design of an airborne sensor for small- and medium-sized UAVs. The cheapest solution for UAV surveillance is the use of visual light cameras. Optical cameras are cheap, light, and require a low supply of power, but their usage is limited to the daytime and good weather conditions. The presence of heavy rain, clouds, fog, or smoke can significantly reduce their imaging distance, sometimes down to just a few meters. Far better results can be obtained using much longer electromagnetic waves. The use of far infrared (e.g. in the 10 μm region) can provide thermal information and can be used for the detection of people in both day and night conditions, but it does not provide satisfactory images of land and infrastructures. The use of millimeter and centimet- r microwaves with active illumination, combined with SAR technology, can provide high resolution images in all weather conditions, day and night, at a distance of several kilometers
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