A Polarimetric Phased Array Antenna for E-SAR in L-Band

The design of a new L-band antenna for DLR’s airborne synthetic aperture radar system (E-/F-SAR) is presented. Beside operations in L-band new components for a system upgrade were developed. These components are intro-duced. Special interest of this paper is the development of the dual-polarized L-Band antenna with enhanced bandwidth of 150MHz. The antenna feed network is equipped with 2bit hybrid phase shifters to steer the beam between 25° and 40° in elevation. For mounting the antenna at the fuselage of a Dornier Do 228-212 aircraft a rack is described to house several antenna configuration

A P-band 5-way Unequal Split High Power Divider for SAR Applications

The design and test of 5-way high power divider operating at P-band for the airborne Synthetic Aperture Radar (SAR) system of DLR is presented. Distinctive features are high bandwidth, high power and an unequal power split on the 5 output ports

Measurements of a Multi Feed Reflector Antenna for SAR Systems Based on Digital Beam Forming

In the last years, the Synthetic Aperture Radar (SAR) systems evolution migrates toward the use of multi-channel systems based on Digital Beam Forming (DBF) techniques [1]. This tendendy allows fulfilling stringent SAR requirements, providing high spatial resolution within a wide swath. Moreover, the combination of DBF techniques with parabolic reflector antennas merges both flexibility and high antenna gain ending up in a high versatile system [2]. One of the main parts in a Digital Beam Forming (DBF) Synthetic Aperture Radar system is constituted by the antenna. An accurate characterization of the antenna radiation pattern is of high interest for the calibration of the system which guarantees the performance and versatility of the DBF network. This paper describes the measurements of a multi- feed single offset reflector antenna designed in X-band. The antenna is part of an on ground multi-channel radar system used to demonstrate ind investigate DBF techniques at HR/DL

Bistatic Experiment Using TerraSAR-X and DLR’s new F-SAR System

A bistatic X-band experiment was successfully performed early November 2007. TerraSAR-X was used as transmitter and DLR’s new airborne radar system F-SAR, which was programmed to acquire data in a quasi-continuous mode to avoid echo window synchronization issues, was used as bistatic receiver. Precise phase and time referencing between both systems, which is essential for obtaining high resolution SAR images, was derived during the bistatic processing. Hardware setup and performance analyses of the bistatic configuration are pre-sented together with first processing results that verify the predicted synchronization and imaging performance

The Optical Design of CHARIS: An Exoplanet IFS for the Subaru Telescope

High-contrast imaging techniques now make possible both imaging and spectroscopy of planets around nearby stars. We present the optical design for the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), a lenslet-based, cryogenic integral field spectrograph (IFS) for imaging exoplanets on the Subaru telescope. The IFS will provide spectral information for 138x138 spatial elements over a 2.07 arcsec x 2.07 arcsec field of view (FOV). CHARIS will operate in the near infrared (lambda = 1.15 - 2.5 microns) and will feature two spectral resolution modes of R = 18 (low-res mode) and R = 73 (high-res mode). Taking advantage of the Subaru telescope adaptive optics systems and coronagraphs (AO188 and SCExAO), CHARIS will provide sufficient contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets. CHARIS will undergo CDR in October 2013 and is projected to have first light by the end of 2015. We report here on the current optical design of CHARIS and its unique innovations.Comment: 15 page

Dual-Polarized Multilayer L-Band Asymmetric Subarray with Truncated Electric Walls Separation for Airborne SAR Applications

A novel planar phased array of 5x4 multilayer dual polarized aperture coupled stacked patch elements, operating in L-band, with beam steering in elevation and excited with an asymmetric amplitude distribution in azimuth, is presented in this work. The proposed design exploits the restricted available antenna size (2.45λ0 x 1.97λ0) maximizing the number of array elements by means of an interelement spacing of 0.48λ0 and the use of truncated walls. The measurements of the manufactured prototype show an antenna bandwidth of almost 20%, polarization isolation greater than 23 dB and directivity values above 15 dB. Despite the close proximity among the array elements, the measured coupling levels between the feeding ports are lower than -20 dB for the center frequency of operation 1.325 GHz, which makes the proposed work suitable for airborne Synthetic Aperture Radar systems, where a high degree of integration is require

CHARIS Science: Performance Simulations for the Subaru Telescope's Third-Generation of Exoplanet Imaging Instrumentation

We describe the expected scientific capabilities of CHARIS, a high-contrast integral-field spectrograph (IFS) currently under construction for the Subaru telescope. CHARIS is part of a new generation of instruments, enabled by extreme adaptive optics (AO) systems (including SCExAO at Subaru), that promise greatly improved contrasts at small angular separation thanks to their ability to use spectral information to distinguish planets from quasistatic speckles in the stellar point-spread function (PSF). CHARIS is similar in concept to GPI and SPHERE, on Gemini South and the Very Large Telescope, respectively, but will be unique in its ability to simultaneously cover the entire near-infrared $J$, $H$, and $K$ bands with a low-resolution mode. This extraordinarily broad wavelength coverage will enable spectral differential imaging down to angular separations of a few $\lambda/D$, corresponding to $\sim$0.\!\!''1. SCExAO will also offer contrast approaching $10^{-5}$ at similar separations, $\sim$0.\!\!''1--0.\!\!''2. The discovery yield of a CHARIS survey will depend on the exoplanet distribution function at around 10 AU. If the distribution of planets discovered by radial velocity surveys extends unchanged to $\sim$20 AU, observations of $\sim$200 mostly young, nearby stars targeted by existing high-contrast instruments might find $\sim$1--3 planets. Carefully optimizing the target sample could improve this yield by a factor of a few, while an upturn in frequency at a few AU could also increase the number of detections. CHARIS, with a higher spectral resolution mode of $R \sim 75$, will also be among the best instruments to characterize planets and brown dwarfs like HR 8799 cde and $\kappa$ And b.Comment: 13 pages, 7 figures, proceedings from SPIE Montrea

Persistence of engineered nanoparticles in a municipal solid-waste incineration plant

More than 100 million tonnes of municipal solid waste are incinerated worldwide every year1. However, little is known about the fate of nanomaterials during incineration, even though the presence of engineered nanoparticles in waste is expected to grow2. Here, we show that cerium oxide nanoparticles introduced into a full-scale waste incineration plant bind loosely to solid residues from the combustion process and can be efficiently removed from flue gas using current filter technology. The nanoparticles were introduced either directly onto the waste before incineration or into the gas stream exiting the furnace of an incinerator that processes 200,000 tonnes of waste per year. Nanoparticles that attached to the surface of the solid residues did not become a fixed part of the residues and did not demonstrate any physical or chemical changes. Our observations show that although it is possible to incinerate waste without releasing nanoparticles into the atmosphere, the residues to which they bind eventually end up in landfills or recovered raw materials, confirming that there is a clear environmental need to develop degradable nanoparticles

First Interferometric Trials with the Airborne Digital-Beamforming DBFSAR System

The Microwaves and Radar Institute of the German Aerospace Center (DLR) is known for its consistent work on the field of airborne Synthetic Aperture Radar and its application. Currently, the Institute is developing a new advanced airborne SAR system, the DBFSAR, which is planned to supplement its operational F-SAR system in near future. The development of DBFSAR was triggered by the various evolving digital beamforming (DBF) techniques for future space-borne SAR systems and the need for an airborne experimental platform for preparation of such missions. Additionally, there is a demand for very high resolution SAR imagery, which cannot anymore be fully satisfied with the existing F-SAR system. This paper should give an overview over the current status and performance of the DBFSAR system, including interferometirc results from test flights performed in spring 2017