The first satellite laser echoes recorded on the streak camera

The application of the streak camera with the circular sweep for the satellite laser ranging is described. The Modular Streak Camera system employing the circular sweep option was integrated into the conventional Satellite Laser System. The experimental satellite tracking and ranging has been performed. The first satellite laser echo streak camera records are presented

Two wavelength satellite laser ranging using SPAD

When ranging to satellites with lasers, there are several principal contributions to the error budget: from the laser ranging system on the ground, from the satellite retroarray geometry, and from the atmosphere. Using a single wavelength, we have routinely achieved a ranging precision of 8 millimeters when ranging to the ERS-1 and Starlette satellites. The systematic error of the atmosphere, assuming the existing dispersion models, is expected to be of the order of 1 cm. Multiple wavelengths ranging might contribute to the refinement of the existing models. Taking into account the energy balance, the existing picosecond lasers and the existing receiver and detection technology, several pairs or multiple wavelengths may be considered. To be able to improve the atmospheric models to the subcentimeter accuracy level, the differential time interval (DTI) has to be determined within a few picoseconds depending on the selected wavelength pair. There exist several projects based on picosecond lasers as transmitters and on two types of detection techniques: one is based on photodetectors, like photomultipliers or photodiodes connected to the time interval meters. Another technique is based on the use of a streak camera as an echo signal detector, temporal analyzer, and time interval vernier. The temporal analysis at a single wavelength using the streak camera showed the complexity of the problem

Fourier transform photoluminescence excitation spectroscopy of medium-bandgap Hg1-xCdxTe and InSb.

We report for the first time on Fourier transform photoluminescence excitation spectroscopy in the mid-infrared covering the wavelength range between 1 and 5.5 Mym. By studying a medium-bandgap Hgsub0.66Cdsub0.34Te bulk crystal and InSb bulk material, direct evidence for the excitonic nature of the luminescence transitions has been found in both cases. In addition, the excitation spectra on MBE-grown Hgsub1minusxCdsubxTe superlattices show the step-like density of states of the confined two- dimensional system

On the horizon: new ESA Laser Ranging Station (ELRS) with debris tracking capabilities

A new, mostly COTS based “Laser Ranging Station for Cooperative Targets” is being built for the European Space Agency (ESA) by a consortium of European companies and institutes (D, A, CH, LV) under the lead of DiGOS Potsdam GmbH. The objective of the ELRS is to establish a flexible and economical basis for various optical applications. Starting with laser ranging to cooperative targets and demonstrating passive-optical debris tracking, the system provides the adaptability for future applications to be integrated including laser ranging to non-cooperative targets/debris, space-to-ground laser communication, and for serving as a general test bed for optical technologies. We will present the multi-purpose concept and the flexibilities of the ELRS design with a focus on current and future debris tracking capabilities which are being strongly advanced together with the scientific partners IWF and AIUB

Optical and electrical characterization of boron-doped diamond films

Diamond films synthesized from CHdeep4/Hdeep2 mixtures using microwave-assisted plasma deposition were prepared on Si substrates under different growth conditions resulting in (100) and (110)/(111) mixed textured diamond films. p-Type doping with boron was achived by adding trimethylborate to the process gas at concentrations ranging from 0.05 to 500ppm. The boron concentration in the film, as determined by secondary ion mass spectroscopy (SIMS), depended strongly on the texture of the films. For gas phase concentrations of less than 1ppm, the boron incorporation rate in (100) textured films was found to be two orders of magnitude lower than for (110)/(111) textured films. Higher boron concentrations led to a deterioration of the (100) texture, whereas the structure and morphology of the (110)/(111) textured films remained almost unaffected even by highest boron concentrations. The boron concentration of (110)/(111) textured films varied linearly with gas phase concentrations below 50p pm. The boron incorporation saturates for gas phase concentrations exceeding 50ppm, resulting in a maximum boron concentration of 2.1x10high20cmhigh-3 in the diamond film. Temperature-dependent Hall measurements were performed to obtain information on the carrier concentration and activitation energy. The data for the highest doped samples reveal electrical properties which can be attributed to films with doping levels near the metal-insulator Mott transition. Raman spectra of the more heavily doped (110)/(111) textured samples show an increasing asymmetry of the 1332cmhigh-1 zone centre optical phonon line with increasing boron concentration, which is assigned to a Fano-type interference. The shape of the phonon line can be fitted by a superposition of lorentzian and Fano lineshapes which can be explained by a growth sector-dependent boron incorporation. The Fano asymmetry, increasing in strength with increasing dopant concentration, was also found in the Raman spectra of homoepitaxi a l boron-doped high13C diamond films which were grown on (111) natural diamond substrates. For the (110)/(111) textured films, strong IR absorption around 3000cmhigh-1 was observed due acceptor ionization, the strength of which correlates with the boron concentration

Ubc9 Sumoylation Controls SUMO Chain Formation and Meiotic Synapsis in Saccharomyces cerevisiae

Posttranslational modification with the small ubiquitin-related modifier SUMO depends on the sequential activities of E1, E2, and E3 enzymes. While regulation by E3 ligases and SUMO proteases is well understood, current knowledge of E2 regulation is very limited. Here, we describe modification of the budding yeast E2 enzyme Ubc9 by sumoylation (Ubc9*SUMO). Although less than 1% of Ubc9 is sumoylated at Lys153 at steady state, a sumoylation-deficient mutant showed significantly reduced meiotic SUMO conjugates and abrogates synaptonemal complex formation. Biochemical analysis revealed that Ubc9*SUMO is severely impaired in its classical activity but promoted SUMO chain assembly in the presence of Ubc9. Ubc9*SUMO cooperates with charged Ubc9 (Ubc9~SUMO) by noncovalent backside SUMO binding and by positioning the donor SUMO for optimal transfer. Thus, sumoylation of Ubc9 converts an active enzyme into a cofactor and reveals a mechanism for E2 regulation that orchestrates catalytic (Ubc9~SUMO) and noncatalytic (Ubc9*SUMO) functions of Ubc9

Transport asymmetry and photovoltaic response in -AlGa-As/AlAs/GaAs/-AlGa-As single-barrier quantum-wel infrared detectors.

We have studied the wavelength and electric-field characteristics of intersubband photodetectors where a thin AlAs tunnel barrier was introduced between one side of the GaAs quantum well and thicker layers of (AlGa)As. The photoresponse of these structures has an extremely broad (3-11 Mym) spectral range and there is a preferential escape direction of the photoexcited carriers towards one direction of the quantum wells giving rise to photovoltaic detector behavior. We found evidence that this transport asymmetry is not only caused by the asymmetric potential distribution, but that interface scattering processes are involved. These scattering processes act differently on the photocurrent and the dark current, which is useful for further optimization of quantum-well infrared detectors