Thomas Behnke

Venus cloud top winds from tracking UV features in Venus Monitoring Camera images

[1]xa0To date dynamical observations of the Venus clouds have delivered mainly either only short-term or long-term averaged results. With the Venus Monitoring Camera (VMC) it finally became possible to investigate the global dynamics with a relatively high resolution in space and time on a long-term basis. Our findings from manual cloud feature wind tracking in VMC UV image sequences so far show that the details of the mesospheric dynamics of Venus appear to be highly variable. Although the general rotation of the atmosphere remained relatively stable since Mariner 10, more than 30 years ago, by now, there are indications of short-term variations in the general circulation pattern of the Venus atmosphere at cloud top level. In some cases, significant variations in the zonal wind properties occur on a timescale of days. In other cases, we see rather stable conditions over one atmospheric revolution, or longer, at cloud top level. It remains an interesting question whether the irregularly observed midlatitude jets are indeed variable or simply become shielded from view by higher H2SO4 haze layers for varying time intervals. Winds at latitudes higher than 60°S are still difficult to obtain track because of low contrast and scarcity of features but increasing data is being collected. Over all, it was possible to extend latitudinal coverage of the cloud top winds with VMC observations. Thermal tides seem to be present in the data, but final confirmation still depends on synthesis of Visible and Infrared Thermal Imaging Spectrometer and VMC observations on night and dayside. Although poorly resolved, meridional wind speed measurements agree mainly with previous observations and with the presence of a Hadley cell spanning between equatorial region and about 45°S latitude.

Space-qualified laser system for the BepiColombo Laser Altimeter.

The space-qualified design of a miniaturized laser for pulsed operation at a wavelength of 1064xa0nm and at repetition rates up to 10xa0Hz is presented. This laser consists of a pair of diode-laser pumped, actively q-switched Nd:YAG rod oscillators hermetically sealed and encapsulated in an environment of dry synthetic air. The system delivers at least 300 million laser pulses with 50xa0mJ energy and 5xa0ns pulse width (FWHM). It will be launched in 2017 aboard European Space Agencys Mercury Planetary Orbiter as part of the BepiColombo Laser Altimeter, which, after a 6-years cruise, will start recording topographic data from orbital altitudes between 400 and 1500xa0km above Mercurys surface.

Investigations on performance of Electron Multiplied CCD detectors (EMCCDs) after radiation for observation of low light star-like objects in scientific space missions

The DLR Institute of Planetary Exploration has proposed a novel design of a space instrument accommodated on a small satellite bus (SSB) that is dedicated to the detection of inner earth objects (IEOs) from a low earth orbit (LEO). The instrument design is based on a focal plane consisting of electron multiplied CCDs (EMCCD) operating at high frame rates for compensation of the spacecraft’s pointing jitter at very low effective readout noise. The CCD detectors operate at a nominal operating temperature of -80°C and at a frame rate of 5fps. It is well known, that CCD detectors are prone to space radiation. However, EMCCD, designed to detect very low light levels of a few electrons, have not yet been used in space. Therefore, investigations have been initiated and performed by DLR for evaluation of the performance of EMCCDs before and after radiation. The main scope of the investigations was the characterization of the charge transfer efficiency (CTE) at low light levels because of its key impact on the detection performance. The non-ionizing dose effects of space high energy particle radiation on the detector were simulated by 60MeV protons at two different fluence levels. The low light-CTE was measured with point light sources without and with background-light.

MOSES: a modular sensor electronics system for space science and commercial applications

The camera group of the DLR--Institute of Space Sensor Technology and Planetary Exploration is developing imaging instruments for scientific and space applications. One example is the ROLIS imaging system of the ESA scientific space mission `Rosetta, which consists of a descent/downlooking and a close-up imager. Both are parts of the Rosetta-Lander payload and will operate in the extreme environment of a cometary nucleus. The Rosetta Lander Imaging System (ROLIS) will introduce a new concept for the sensor electronics, which is referred to as MOSES (Modula Sensor Electronics System). MOSES is a 3D miniaturized CCD- sensor-electronics which is based on single modules. Each of the modules has some flexibility and enables a simple adaptation to specific application requirements. MOSES is mainly designed for space applications where high performance and high reliability are required. This concept, however, can also be used in other science or commercial applications. This paper describes the concept of MOSES, its characteristics, performance and applications.

The asteroid finder focal plane

The DLR Institute of Planetary Exploration has proposed a novel design for a space instrument accommodated on a small satellite bus (SSB) that is dedicated to the detection of inner earth objects (IEOs) from a low earth orbit (LEO). The low pointing stability of the satellite bus, the stray light and thermal environment in LEO represent the major design drivers for achieving the required limiting magnitude of 18.5 (V-band). In order to cope with the design drivers, DLR has proposed a novel focal plane consisting of four Electron Multiplying CCDs (EMCCD) and their associated electronics.

Optical/mechanical design of the focal plane receiver of the Ganymede Laser Altimeter (GALA) for the Jupiter Icy Moons Explorer (JUICE) mission

The Jupiter Icy Moons Explorer (JUICE) mission of the European Space Agency to be launched in 2022 will provide an opportunity for a dedicated exploration of the Jovian system including its icy moons. The Ganymede Laser Altimeter (GALA) has been selected as one of the ten payloads of JUICE. GALA will enable unique studies of the topography and shape, tidal and rotational state, and geology of primarily Ganymede but also Europa and Callisto. The GALA project is an ongoing international collaboration led by Germany, together with Switzerland, Spain, and Japan. This paper presents the optical and mechanical design of the focal plane receiver, the Japanese part of GALA.

The BepiColombo Laser Altimeter (BeLA) power converter module (PCM): Concept and characterisation

This paper presents the principal considerations when designing DC-DC converters for space instruments, in particular for the power converter module as part of the first European space laser altimeter: BepiColombo Laser Altimeter on board the European Space Agency-Japan Aerospace Exploration Agency (JAXA) mission BepiColombo. The main factors which determine the design of the DC-DC modules in space applications are printed circuit board occupation, mass, DC-DC converter efficiency, and environmental-survivability constraints. Topics included in the appropriated DC-DC converter design flow are hereby described. The topology and technology for the primary and secondary stages, input filters, transformer design, and peripheral components are discussed. Component selection and design trade-offs are described. Grounding, load and line regulation, and secondary protection circuitry (under-voltage, over-voltage, and over-current) are then introduced. Lastly, test results and characterization of the final flight design are also presented. Testing of the inrush current, the regulated output start-up, and the switching function of the power supply indicate that these performances are fully compliant with the requirements.

Planetary exploration with optical imaging systems review: What is the best sensor for future missions

When we talk about planetary exploration missions most people think spontaneously about fascinating images from other planets or close-up pictures of small planetary bodies such as asteroids and comets. Such images come in most cases from VIS/NIR- imaging- systems, simply called ‘cameras’, which were typically built by institutes in collaboration with industry. Until now, they have nearly all been based on silicon CCD sensors, they have filter wheels and have often high power-consuming electronics. The question is, what are the challenges for future missions and what can be done to improve performance and scientific output. The exploration of Mars is ongoing. NASA and ESA are planning future missions to the outer planets like to the icy Jovian moons. Exploration of asteroids and comets are in focus of several recent and future missions. Furthermore, the detection and characterization of exo-planets will keep us busy for next generations. The paper is discussing the challenges and visions of imaging sensors for future planetary exploration missions. The focus of the talk is monolithic VIS/NIR- detectors.

Focal plane electronics for the GAIA focal plane demonstrator

The GAIA mission of the European Space Agency (ESA) comprises two Astro telescopes with a very large common focal plane. The focal plane assembly consist of about 180 CCDs and accompanying video chains. The CCDs are operating in a TDI mode with complex windowing- and binning modes. Low noise, large dynamic range, linearity are mandatory for success of the Mission. Therefore, ESA has initiated a technology demonstrator, which should demonstrate the technical feasibility. Astrium-SAS in Toulouse and DLR-IPF in Berlin have successfully performed the study, in which DLR has developed the CCD- video electronics and the Interconnection Modules for the Focal Plane Demonstrator. The requirements, the conceptional design and the results are presented in this paper.

Converting a Schmidt Telescope to CCDs: The OCA/DLR Asteroid Survey

The OCA Schmidt telescope is a classical Schmidt telescope, 90cm aperture, 1.50 meter mirror and 3.14 meters focal length. It was put into operation in 1978, at a time when astronomical CCDs were in their infancy, and has been designed as a photographic telescope. It has been used for a variety of projects, involving photographic plates, and later photographic films. Intended mostly as a technological development, a small CCD camera was installed inside one of our plate holders has been done in 1992. Thereafter, the development of larger CCD cameras for our telescope has been motivated by the need to survey large area of sky in order to discover Near Earth Asteroids. Since 1995, this effort is a collaborative effort between our team and DLR Berlin.