Cosima – High Resolution Time-of-Flight Secondary Ion Mass Spectrometer for the Analysis of Cometary Dust Particles onboard Rosetta

The ESA mission Rosetta, launched on March 2nd, 2004, carries an instrument suite to the comet 67P/Churyumov-Gerasimenko. The COmetary Secondary Ion Mass Anaylzer – COSIMA – is one of three cometary dust analyzing instruments onboard Rosetta. COSIMA is based on the analytic measurement method of secondary ion mass spectrometry (SIMS). The experiment’s goal is in-situ analysis of the elemental composition (and isotopic composition of key elements) of cometary grains. The chemical characterization will include the main organic components, present homologous and functional groups, as well as the mineralogical and petrographical classification of the inorganic phases. All this analysis is closely related to the chemistry and history of the early solar system. COSIMA covers a mass range from 1 to 3500 amu with a mass resolution m/Δm @ 50% of 2000 at mass 100 amu. Cometary dust is collected on special, metal covered, targets, which are handled by a target manipulation unit. Once exposed to the cometary dust environment, the collected dust grains are located on the target by a microscopic camera. A pulsed primary indium ion beam (among other entities) releases secondary ions from the dust grains. These ions, either positive or negative, are selected and accelerated by electrical fields and travel a well-defined distance through a drift tube and an ion reflector. A microsphere plate with dedicated amplifier is used to detect the ions. The arrival times of the ions are digitized, and the mass spectra of the secondary ions are calculated from these time-of-flight spectra. Through the instrument commissioning, COSIMA took the very first SIMS spectra of the targets in space. COSIMA will be the first instrument applying the SIMS technique in-situ to cometary grain analysis as Rosetta approaches the comet 67P/Churyumov-Gerasimenko, after a long journey of 10 years, in 2014.     

Numerical investigations on the VFE-2 65-degree rounded leading edge delta wing using the unstructured DLR TAU-Code

The numerical simulation of the flow around a 65° delta wing configuration with rounded leading edges is presented. For the numerical simulation the DLR TAU-Code is used which is based on an unstructured hybrid mesh approach. Within this paper several numerical results are shown, solving the steady RANS equations by different turbulence models. The simulations are carried out within the RTO/AVT-113 task group focusing on experimental and numerical research on delta wing configurations with rounded leading edges. Within this paper the focus is related to the flow topology depending on the angle of attack as well as on Reynolds number effects. Finally the results are compared and verified by experimental data.     

The ROSAT mission

A primary scientific objective of the ROSAT mission is to perform the first all-sky survey with an imaging X-ray telescope leading to an improvement in sensitivity by several orders of magnitude compared with previous surveys. A large number of new sources (? 10⁵) will be discovered and located with an accuracy of 1 arcmin or better. These will comprise almost all astronomical objects from nearby normal stars to distant quasistellar objects. After completion of the survey which will take half a year the instrument will be used for detailed observations of selected sources with respect to spatial structure, spectra and time variability. In this mode which will be open for guest observers ROSAT will provide substantial improvement over the imaging instruments of the Einstein observatory.The main ROSAT telescope consists of a fourfold nested mirror system with 83 cm aperture having three focal plane instruments. Two of them will be imaging proportional counters (0.1 – 2 keV) providing a field of view of 2°, an angular resolution of ≈ 30″ in the pointing mode and a spectral resolution ^ΔE/E ≈ 45% FWHM at 1 keV. The third focal instrument will be a high resolution imager (≈ 3″). The main ROSAT telescope will be complemented by a parallel looking Wide Field camera which extend the spectral coverage into the XUV band.     

Two-dimensional analyzer with dE-dE silicon detectors for cosmic ray experiments in space

A charged particle semiconductor-telescope is under construction in the CRIP, Budapest, to measure fluxes of 4–30 MeV/AMU protons, alphas, and M nuclei in interplanetary space. Identification and counting of particles are made on-board using microprocessor techniques. Details including some new ideas on economical coding of information and design of electronics are given.     

Convection in melts and crystal growth

Convection plays a significant role in determining the electronic properties of semiconductor crystals grown from the melt. Inhomogeneities (doping striations) in these crystals can be caused by unsteady natural convection. Therefore, the origins of unsteady natural convection, which means fluctuating temperatures in a fluid, are investigated in this paper. Several effects have been found at increasing Rayleigh numbers Ra which cause fluctuating temperatures. But it was also observed, that unsteady convection became again steady if Ra was increased to higher values. This effect, which is called relaminarization, is very interesting for crystal growth and is discussed in this paper.     

The helium abundance on Jupiter

Methods of determining helium on Jupiter (and the Jovian planets) are critically surveyed. Current information is consistent with solar abundance, He/H₂ = 0.11 by number. The available lines of evidence are the mean density, spectral-line broadening, and stellar occultations. Methods usable from spacecraft flying by are discussed. Observation of far-infrared emission has great promise, but we may have to await the development of entry probes for the greatest assurance.This is one of the publications by the Science Advisory Group.     

Comparison of quiet-Sun radiances measured by CDS and SUMER on SOHO

Space Science Reviews - Since the beginning of the SOHO (Solar and Heliospheric Observatory) mission an intercalibration programme was carried out which included simultaneous observations of the...     

Formation of Jupiter's rings

An excellent review of the present understanding of the structure and formation of Jupiter's rings has recently been published by Burns et al. /1/. Therefore I will only summarize the basic ideas and open questions concerning the physical phenomena governing Jupiter's rings.     

Computer-Aided Design and Weight Estimation of High-Power High-Voltage Power Conditioners

Aspects of high-power high-voltage power conditioner design and weight estimation relevant to space subsystems are discussed. Weight has become an increasingly important parameter with the advent of larger and more sophisticated spacecraft, especially those for high-power communication. A computer program for estimating the weight of a high-power dc-to-dc power conditioner as functions of output power, operating frequency, input voltage range, maximum input voltage, and efficiency, respectively, is described, including computer-aided design of inductors and transformers. Curves of typical power conditioner weight as functions of the preceding parameters, derived from the power conditioner weight program, are presented.     

Development status and application of the electric propulsion system RIT-10 used for station-keeping

The German 10 mN high frequency ion thruster system RIT-10 designed at Giessen University, constructed at MBB, and tested essentially at DFVLR, has attained an engineering model status and stands shortly before qualification for space flight. First application is planned for RIT-10 as a north-south stationkeeping system in TV-Sat preoperational version where it is flown as an experiment in order to acquire experience for subsequent operational communication satellite missions. The paper first describes the existing hardware, then shortly discusses application aspects, the respective test program, and preflight and flight procedures considered to guarantee safe and efficient operation in space.