Schutz von weltraumgestützten Systemen

Die Bedeutung von Satelliten-Systemen zum Schließen von Fähigkeitslücken in der Aufklärung, Kommunikation und Navigation nimmt stetig zu. Die benötigten Informationen können präzise und schnell zur Verfügung gestellt werden. Jedoch unterliegen die Raumfahrzeuge auch einer Vielzahl von Bedrohungen. In einer vom DLR erstellten Studie wurden die Gefahren aus dieser Systemumwelt betrachtet und eruiert, welche Gegenmaßnahmen zum Schutz von weltraumgestützten Systemen sich ableiten lassen

Entwicklungen und Möglichkeiten passiver Mikrowellentechniken im Sicherheitsbereich

Der Vortrag behandelt Grundlagen und potentielle Anwendungsmöglichkeiten der Mikrowellenradiometrie für moderne Sicherheitsanwendungen

Requirements and Technological Needs for Military Space-borne Reconnaissance Systems

Requirements For military space-borne reconnaissance systems two major requirements are minimized systems response time, which is the time span between the order of a needed image and an assessable image on ground, and minimized image age, which is the time span between image acquisition and assessable image on ground. To fulfil these requirements in an optimal way with reasonable image quality and cost, a constellation of small satellites is needed. Software For design, development and operations of such a multi satellite mission new software tools are necessary. The regarding developments within the Satellite-Systems-Engineering Group of DLR will be presented. Hardware Also new hardware technologies are needed to build up a cost effective satellite constellation. The possibility for multiple launches is a cost saver but requires small satellites and therefore, using a classical SAR-Sensor for image generation, deployable reflectors to get reasonable apertures in space. A proposal for such a new reflector technology will be presented. Risk analysis The more satellites we have in space the larger is the risk for the single space craft to be damaged or destroyed by natural, man-made or active threats in orbit. The possible threats will be shortly overviewed and potential counteractions described

Error analysis of sparse passive synthesis radiometers on UAV platforms

Passive millimetre-wave imaging is a potential solution to surveillance problems in the presence of obscurants. Research has shown that passive millimetre-wave imaging can form high contrast, natural imagery even through foul weather. The application of passive acquisition methods on a UAV is important for strategical and tactical reasons. In mountainous regions or in highly urbanized areas an almost Nadir looking imaging scheme for the data acquisition is beneficial. In order to achieve sufficient ground resolution from a few kilometers altitude, the use of synthetic methods is proposed. The method of aperture synthesis for high resolution passive imaging is discussed, and a simulated system design example using the UAV platform characteristics is illustrated. Since the aperture size even for W band is in the order of several meters, the imaging performance is influenced by many parameters, which are otherwise negligible. Within this context the feasibility of such a system on a UAV platform is discussed

Protection of Spaceborne Systems

The importance of satellite systems for closing capability gaps in reconnaissance, communication and navigation is increasing constantly. Such systems can provide the sought-after information rapidly and accurately. Spacecraft, however, are also vulnerable to a multitude of threats. A study conducted by the DLR (German Aerospace Center) has looked at these threats and determined what are the most efficient countermeasures for protecting spaceborne systems

Analysis of SAR images by simulation

Accurate simulation tools for the design of space borne synthetic aperture radar systems (SAR) are compulsory for the analysis of the system's capabilities, because ground based experimental tests are in most cases impossible and very costly. Through a simulation process it is possible to analyze the image quality parameters for a given system configuration or evaluating the effects in SAR images when this configuration is changed. A new fast SAR image simulator (SARIS) is currently under development on the basis of an existing toolset called SAR end-to-end simulator (SETES). This image simulator produces SAR images by using the point spread function (PSF) of a focused point target response in contrast to SETES's very expensive raw data generation module. In SARIS the SAR image is produced through a convolution of the PSF with the so-called reflectivity map of the scene. In this paper first simulation results with a prototype of SARIS are given to show effects like motion errors and low peak-to-side-lobe ratios

A multi-frequency microwave aperture synthesis radiometer for high-resolution imaging

Many geophysical parameters can be determined with the aid of a passive microwave sensor. To achieve a high spatial resolution in passive microwave imaging the method of aperture synthesis can be applied. Narrowband radiometric measurements within a wide frequency range allow extracting more surface information on observed objects or materials and it is possible to obtain depth information on layered structures. Furthermore the advantages of using a range of different center frequencies, i.e. a higher spatial resolution with increasing frequency and a higher penetrating capability at lower frequencies, can be combined in many cases to enhance the overall imaging capabilities. Thus our recent interest is focused on the development of an experimental system offering those features but keeping the costs affordable. In this paper the basic system concept is outlined

Simulation Techniques for High-Resolution Spaceborne SAR Systems

At the German Aerospace Center (DLR) new methods for a realistic and efficient simulation of high resolution space borne synthetic aperture radar (SAR) systems are being developed. Amongst parametric end-to-end simulations for the design of future SAR missions, these methods can be used as an educational or assistance tool for image analysts in tasks like signature analysis or target recognition

A multi-frequency microwave aperture synthesis radiometer for high-resolution imaging

Many geophysical parameters can be determined with the aid of a passive microwave sensor. To achieve a high spatial resolution in passive microwave imaging the method of aperture synthesis can be applied. Narrowband radiometric measurements within a wide frequency range allow extracting more surface information on observed objects or materials and it is possible to obtain depth information on layered structures. Furthermore the advantages of using a range of different centre frequencies, i.e. a higher spatial resolution with increasing frequency and a higher penetrating capability at lower frequencies, can be combined in many cases to enhance the overall imaging capabilities. Thus our recent interest is focused on the development of an experimental system offering those features but keeping the costs affordable. In this paper the basic system concept and some reconstruction algorithms are outlined and illustrated by an imaging simulatio

A Microwave Imaging Spectrometer for Security Applications

In recent years the security of people and critical infrastructures is of increasing interest. Passive microwave sensors in the range of 1 - 100 GHz are suitable for the detection of concealed objects and wide-area surveillance through poor weather and at day and night time. The enhanced extraction of significant information about an observed object is enabled by the use of a spectral sensitive system. For such a spectral radiometer in the microwave range also some depth information can be extracted. The usable frequency range is thereby dependent on the application. For through-wall imaging or detection of covert objects such as for example landmines, the lower microwave range is best suited. On the other hand a high spatial resolution requires higher frequencies or instruments with larger physical dimensions. The drawback of a large system is the required movement of a mirror or a deflecting plate in the case of a mechanical scanner system, or a huge amount of receivers in a fully-electronic instrument like a focal plane array. An innovative technique to overcome these problems is the application of aperture synthesis using a highly thinned array. The combination of spectral radiometric measurements within a wide frequency band, at a high resolution, and requiring a minimum of receivers and only minor moving parts led to the development of the ANSAS instrument (Abbildendes Niederfrequenz- Spektrometer mit Apertursynthese). ANSAS is a very flexible aperture synthesis technology demonstrator for the analysis of main features and interactions concerning high spatial resolution and spectral sensing within a wide frequency range. It consists of a rotated linear thinned array and thus the spatial frequency spectrum is measured on concentric circles. Hence the number of receivers and correlators is reduced considerably compared to a fully twodimensional array, and measurements still can be done in a reasonable time. In this paper the basic idea of ANSAS and its setup are briefly introduced. Some first imaging results showing the basic capabilities are illustrated. Possible error sources and their impacts are discussed by simulation and compared to the measured data