Experience of passive thermal control of long-term near- Earth small satellite mission

The microsatellite BIRD (Bispectral InfraRed Detection) with mass of 94 kg and overall sizes 0.55 x 0.61 x 0.62 m operates on near-earth sun-synchronous orbit more than 11 years. The temperature range -10…+30 oC for payload and housekeeping equipment with average power of 35 W and peak power of 200 W in the observation mode (10…20 min) is provided by a passive thermal control system (TCS). The TCS supports a thermal stability of the payload structure by use of heat transfer elements – grooved heat pipes, thermally jointing the satellite segments. Two radiators, multilayer insulation (MLI) and low-conductive stand-offs provide the required temperature level. An analysis of TCS performance includes the definition of minimal, maximal and average temperatures of satellite units and their comparison with the designed parameters. The elaborated passive TCS successfully keeps the nominal temperature level of satellite components during one-year designed period of exploitation and sequent 10 years

PASSIVE THERMAL CONTROL SYSTEMS FOR SPACE INSTRUMENTS MAKING – SCIENTIFIC BACKGROUND, QUALIFICATION, EXPLOITATION IN SPACE

Passive thermal control systems (TCS) are one of obligatory system of any space mission, used as on large spacecraft and microsatellites Supporting of required temperature range for space instruments is supported by rational design of TCS with optimal choice of main thermal control components such as multilayer insulation, optical coatings, heat conductive elements, heat insulation supports, thermal conductive gaskets, radiating surfaces and other elements. New ideology in TCS design has come after appearance of new element – heat pipe(s) which is a super heat conductive thermal conductor with constant or variable thermal properties

Understanding human functioning using graphical models

<p>Abstract</p> <p>Background</p> <p>Functioning and disability are universal human experiences. However, our current understanding of functioning from a comprehensive perspective is limited. The development of the International Classification of Functioning, Disability and Health (ICF) on the one hand and recent developments in graphical modeling on the other hand might be combined and open the door to a more comprehensive understanding of human functioning. The objective of our paper therefore is to explore how graphical models can be used in the study of ICF data for a range of applications.</p> <p>Methods</p> <p>We show the applicability of graphical models on ICF data for different tasks: Visualization of the dependence structure of the data set, dimension reduction and comparison of subpopulations. Moreover, we further developed and applied recent findings in causal inference using graphical models to estimate bounds on intervention effects in an observational study with many variables and without knowing the underlying causal structure.</p> <p>Results</p> <p>In each field, graphical models could be applied giving results of high face-validity. In particular, graphical models could be used for visualization of functioning in patients with spinal cord injury. The resulting graph consisted of several connected components which can be used for dimension reduction. Moreover, we found that the differences in the dependence structures between subpopulations were relevant and could be systematically analyzed using graphical models. Finally, when estimating bounds on causal effects of ICF categories on general health perceptions among patients with chronic health conditions, we found that the five ICF categories that showed the strongest effect were plausible.</p> <p>Conclusions</p> <p>Graphical Models are a flexible tool and lend themselves for a wide range of applications. In particular, studies involving ICF data seem to be suited for analysis using graphical models.</p

Identification of Heat Exchange Parameters of Thermal Networks by Transient Measured Node Temperatures at Minimized Measurement Time

Eine übliche Methode zur Formulierung von Thermalmodellen (Thermal Mathematical Models) ist die Methode der konzentrierten Parameter (thermische Netzwerke, thermische Knotenmodelle). Für die genaue Vorhersage des thermischen Verhaltens einer realen Hardware durch ein thermisches Knotenmodell ist es erforderlich, die Wärmeaustauschparameter so gut wie möglich zu kennen. Oft sind transient gemessene Knotentemperaturen eines Thermal Engineering Models oder einer ähnlichen Hardware durch Thermal- Vakuum- Tests verfügbar. In der vorliegenden Arbeit wird die Entwicklung und Anwendung einer numerischen Prozedur zur Identifikation (bzw. Korrektur) der Wechselwirkungsparameter eines thermischen Netzwerkes beschrieben. Der Kern dieser Prozedur ist ein Kalman-Filter Algorithmus, der die gesuchten Parameter aus transient gemessenen Knotentemperaturen errechnet. Dieser Algorithmus wurde so konditioniert, daß er sehr stabil arbeitet. Die notwendigen a priori Werte für das Kalman-Filter werden von einem angepassten Algorithmus der Verallgemeinerten Kleinsten Quadrate bereit gestellt. Dieser Algorithmus verwendet das SVD-Verfahren (Singular Value Decomposition) zur Berechnung der Startparameter und deren Fehlervarianzen und gibt zusätzlich Informationen zu ggf. schlecht gewählten experimentellen Randbedingungen oder zu Modellfehlern. Die gesamte Methode wird auf gemessenen Knotentemperaturen des Thermal Engineering Models des Wide Angle Optical Stereo Scanners der Russischen Mars '96 Mission angewendet. Eine Prozedur zur Einsparung teurer Meßzeit in der Weltraumsimulationsanlage wurde implementiert. Die Resultate werden diskutiert und bewertet. Ein Leitfaden zur Vorgehensweise bei der Validierung des Thermal Mathematical Models mit der vorgestellten Methode wird gegeben.A common method to create Thermal Mathematical Models is the lumped parameter method (Thermal Network; Thermal Nodal Model). For a well prediction of the thermal behaviour of a real hardware by a Thermal Nodal Model it is necessary to know the heat exchange parameters as exactly as possible. Transient measured node temperatures are often available e.g. from thermal vacuum tests of a Thermal Engineering Model (TEM) or a similar real hardware. In this doctoral thesis the development and application of a numerical procedure for the identification (or correction) of interaction parameters of a Thermal Network is described. The core of this procedure is a Kalman Filter Algorithm, which calculates the wanted parameters by the transient measured node temperatures. This Algorithm is conditioned to worki very stable. The necessary a priori values for the Kalman Filter are supplied by an adjusted General Least Square Algorithm. This Algorithm uses the Singular Value Decomposition for calculating of the starting parameters and their error variances and additionally it indicates badly chosen experimental conditions or model failures. The whole method is applied on the measured node temperatures of the Thermal Engineering Model of the Wide Angle Optical Stereo Scanner of the Russian Mars '96 mission. A procedure for saving expensive measurement time in the space simulation chamber was implemented. The results are discussed and assessed. A guideline is given for the kind of action along the validation of the Thermal Mathematical Model by the presented method

BIRD 9 years microsatellite mission the experience of passive thermal control in space

Microsatellites are one of promising instruments to achieve near– Earth space research programs.. The aim of this paper is to present the experience gained by authors during thermal design of microsatellite BIRD and to give a summary of the thermal control system performance during almost 10 years of exploitation in the near – Earth orbit. Microsatellite BIRD (Bispectral InfraRed Detection, mass 95 kg, sizes 550 x 610 x 620 mm) was launched with Indian PSLV on October 22nd, 2001 into a sun-synchronous orbit. Payload consists of precise optical devices: VIS/NIR – Wide Angle Optoelectronic Stereo Scanner and MWIR/LWIR camera with activily cooled infrared sensors, operating within the MWIR range (from 3,4 to 4,2 µm) and within the LWIR range (from 8,5 to 9,3 µm wavelength). These cameras require an accurate control of optical axes geometrical parallelism and a faithful thermal control. The mean satellite power is about 35 – 40 W, with 10 – 20 min peak of 200 W power consumption in observation mode. The microsatellite thermal control system (TCS) has been designed to keep the satellite equipment within –10… +30° C for cold and hot cases. It includes a thermally stable design of the payload structure, heat transfer elements (conductors and grooved heat pipes), thermally connecting the satellite’s segments, two radiators, multilayer insulation and low-conductive stand-offs. More than 9 years of operation in space has brought an enormous volume of telemetric data about the performance of the TCS, based on information of temperature sensors, on power consumption and on the attitude relative to Sun and Earth. The TCS successfully maintained the required temperature level of satellite components. Nevertheless, the authors have set the task to analyze the temperature history during the satellite’s operation life. This concerns the main units of housekeeping equipment such as radiator, payload platform, power supply subsystem, board computer, solar arrays and communication setup. The authors intend to draw conclusions about apparently emerged changes in the thermal conditions and the performance of it. In order to realize that objective, an algorithm of initial telemetric data processing is proposed. A temperature survey is performed for the following time scales: short operation time (10 – 30 min), one orbit (96 min), one day, beginning of operation and actual time, the whole period – by now (from 10.2001 to 10.2010

Landminen - sicheres Aufspüren einer unsichtbaren Bedrohung II, "easyMine" Realistische und systematische Minendetectionssimulation und Anwendung

Weltweit sind rund 100 Länder von den 100 Millionen gegenwärtig verlegten Minen betroffen, die den Wiederaufbau nach Beendigung der kriegerischen Auseinandersetzungen behindern. Die Statistik sagt: Auf jede 1000. geräumte Mine kommt ein Unfall, so dass 100 000 Opfer zusätzlich zu erwarten sind. In der Regel sind dies Zivilisten – häufig Kinder. Der Krieg geht somit an einer anderen Front weiter. Im Rahmen der Vortragsreihe „Sicherheit in der Technik“ stellen am 5. März 2004 Frau Dr. Müller, Bundesanstalt für Materialforschung (BAM) und Frau Dr. Böttger, Deutsches Zentrum für Luft- und Raumfahrt (DLR) mit ihrem Beitrag „Landminen – Sicheres Aufspüren einer unsichtbaren Bedrohung?“ vor, wie die Wissenschaft, verantwortungsbewusst angewandt, hier helfen kann. Beide Institute sind seit einiger Zeit auf dem Gebiet der humanitären Minenräumung aktiv. In dem Beitrag wird geschildert, wie man ein realistisches Bild der Leistungsfähigkeit und Zuverlässigkeit der Such- und Räumtechnik unter realen Feldbedingungen erhalten und diese unter Beachtung aller Einflussfaktoren, nicht nur der physikalisch-technischen, sondern auch der spezifischen Umweltfaktoren und des menschlichen Faktors, verbessern kann. Darüber hinaus wird ein wissenschaftlich hochqualifiziertes aber dennoch realitätsbezogenes Simulationswerkzeug vorgestellt, das neue Techniken zur Minensuche für die konkreten Bedingungen in den betroffenen Ländern punktgenau zusammenstellen kann und gleichzeitig eine rasche Überführung in die Praxis gewährleistet. Mit diesen Verbesserungsmaßnahmen soll nicht nur der Minenräumer im Feld besser geschützt werden, sondern auch das an die Bevölkerung übergebene Land soll zuverlässig geräumt und wieder nutzbar sein. Der Vortrag wird begleitet von einer Ausstellung, in der neben fachwissenschaftlichen auch künstlerisch gestaltete Poster zu sehen sind. Diese Poster wurden im Rahmen eines Wettbewerbs von Studenten verschiedener Kunsthochschulen erarbeitet. Darüber hinaus werden Beispiele von Minen aus verschiedenen Regionen der Welt aus der Ausstellung des Vereins für Humanitäre Kampfmittelbeseitigung e.V. und ein Metalldetektor in Aktion gezeigt

NEW APPROACH TO THE PASSIVE THERMAL CONTROL SYSTEM WITH LOW-TEMPERATURE “AL-NH3” HEAT PIPES: QUALIFICATION TESTING RESULTS AND FLIGHT PERFORMANCE ON MICROSATELLITE BIRD

An important question of exploitation of near-Earth space environment investigation satellites is the support of a thermal regime of satellite as a whole and devices in particular. Guarantee of their reliable working in space depends on thermocontrol system (TCS) operation that is confirmed by qualification working-off ground tests both with heat pipes separately and when they are a part of satellite TCS. The program of qualification tests and its realisation is considered in this paper. The typical modelling object is an ammonia aluminium grooved heat pipe (shell diameter of 12 mm, 30 grooves) developed for DLR's BIRD small satellite program. Qualification tests consist of thermal steady-state and non-stationary performance tests, long life tests, environmental tests and others reviewed in the paper. Tests of determination of thermal resistance, maximum heat transfer rate, influence of tilt on maximum heat transfer rate are related to determination of thermal technical characteristics of heat pipes. Start-up tests, in which an ability of heat pipe to continue the function normally after certain power surge is determined, tests on definition of priming time, in which the priming time of heat pipe capillary structure after its full drainage by method of direct discharging and continuing the power supply is defined, are related to non-stationary tests. During the long life tests an ability of heat pipe to function for a long time is checked and quantity of noncondensable gas generated is defined. Test program was realised on test facilities of the National Technical University of Ukraine “Kyiv Polytechnic Institute” (Kyiv, Ukraine) and Institute of Structural Mechanics (Berlin, Germany). The analysis of heat pipe operation during qualification test and flight performance of BIRD satellite is shortly reviewed on the base of telemetric informatio

BIRD - Microsatellite Thermal Control System - 5 Years of Operation in Space

Microsatellite BIRD (Bispectral InfraRed Detection) with mass 92 kg and overall sizes 0,55x 0,61x 0,62 m operates on a sun-synchronous orbit more than 5 years. The temperature range –10 …+30 oC for payload with average power about 35 W and peak power of 200 W in observation mode, continuing 10-20 min is provided by passive thermal control system (TCS). Operation of TCS foresees a thermal stability of payload structure by use of heat transfer elements - conductors and grooved heat pipes - thermally jointing the satellites segments. Two radiators, multilayer insulation (MLI) and low-conductive stand-offs provide the required temperature level. Review of TCS performance is based on an analysis of daily telemetric data, collected by 33 temperature sensors and power consumption. An analysis includes the definition of minimal, maximal and averaged temperatures of satellite main units and comparison with designed parameters. TCS successfully supports the required temperature level of satellite components during the whole period of exploitatio

"easyMine" Realistic and systematic Mine Detection Simulation Tool

Mine detection is to date mainly performed with metal detectors, although new methods for UXO detection are explored worldwide. The main problem for the mine detection to date is, that there exist some ideas of which sensor combinations could yield a high score, but until now there is no systematic analysis of mine detection methods together with realistic environmental conditions to conclude on a physically and technically optimised sensor combination. This gap will be removed by a project “easyMine” (Realistic and systematic Mine Detection Simulation Tool) which will result in a simulation tool for optimising land mine detection in a realistic mine field. The project idea for this software tool is presented, that will simulate the closed chain of mine detection, including the mine in its natural environment, the sensor, the evaluation and application of the measurements by an user. The tool will be modularly designed. Each chain link will be an independent, exchangeable sub module and will describe a stand alone part of the whole mine detection procedure. The advantage of the tool will be the evaluation of very different kinds of sensor combinations in relation of their real potential for mine detection. Three detection methods (metal detector, GPR and IR-polarimetry) will be explained to be introduced into the easyMine software tool in a first step. An actual example for land mine detection problem will be presented and approaches for solutions with easyMine will be shown

THE 3-STEP DLR-ESA GOSSAMER ROAD TO SOLAR SAILING

The 3-step Gossamer road map to solar sailing is presented, that has been agreed between DLR and ESA in November 2009. The main and exclusive purpose of that project is to develop, to prove, and to demonstrate the solar sail technology as a safe and reliably manageable propulsion technique for long lasting and deep space missions. Since the development of the solar sail technology is a quite complex task, presently at the DLR implemented solar sail related research activities will be presented as well