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

The Ganymede Laser Altimeter (GALA) for the Jupiter Icy Moons Explorer (JUICE): Mission, science, and instrumentation of its receiver modules

The Jupiter Icy Moons Explorer (JUICE) is a science mission led by the European Space Agency, being developed for launch in 2023. The Ganymede Laser Altimeter (GALA) is an instrument onboard JUICE, whose main scientific goals are to understand ice tectonics based on topographic data, the subsurface structure by measuring tidal response, and small-scale roughness and albedo of the surface. In addition, from the perspective of astrobiology, it is imperative to study the subsurface ocean scientifically. The development of GALA has proceeded through an international collaboration between Germany (the lead), Japan, Switzerland, and Spain. Within this framework, the Japanese team (GALA-J) is responsible for developing three receiver modules: the Backend Optics (BEO), the Focal Plane Assembly (FPA), and the Analog Electronics Module (AEM). Like the German team, GALA-J also developed software to simulate the performance of the entire GALA system (performance model). In July 2020, the Proto-Flight Models of BEO, FPA, and AEM were delivered from Japan to Germany. This paper presents an overview of JUICE/GALA and its scientific objectives and describes the instrumentation, mainly focusing on Japan’s contribution

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

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

From Observational Geometry to Practical Satellite Design: AsteroidFinder/SSB

DLR has selected AsteroidFinder as the first payload to be flown on its SSB satellite platform, in the frame of the German national Compact Satellite Program. The scientific goal is to better observe and characterize Near-Earth Objects (NEO), particularly the Aten asteroids and the Inner Earth Objects orbiting completely Interior to Earth’s Orbit (IEO). Only ten mostly Aten-like IEOs have been found so far, of which two are Potentially Hazardous Asteroids (PHA). Ground-based observations of Atens and IEOs are severely constrained by the Earth’s body and its atmosphere. An Earth-orbiting survey telescope can in principle evade these constraints with ease, to become an efficient and cost-effective tool to facilitate the discovery and follow-up of these objects. It may however be constrained by other factors specific to its orbital environment. Analysis of the observational geometry and present technological capabilities has shown that stray light from the Sun and Earth is the most critical performance limiter. The thermal influences of both sunlight and earthlight become important if the capabilities of state-of-the-art detectors are to be fully exploited at low temperatures. Thus, the optical and thermal behaviour of the satellite as a system beyond the scientific instrument itself is strongly coupled, through the shape and layout of the satellite and the parameters of the satellite’s orbit, to the observational geometry of the target asteroids, the Earth, and the Sun. Objects within the Earth’s orbit are to be observed in a region of interest continuing sunward from that covered by ground-based surveys to 30° solar elongation. Their identification is accomplished through apparent motion and parallax, requiring repeated observations of the same field which the satellite has to provide at certain intervals. The strong coupling of optical and thermal influences forces system-level optimization of the geometrical layout of the satellite in accordance with survey pointing patterns. This affects the layout of the telescope and the components visible to its aperture, the positioning of several radiators for different temperature levels, the accommodation of antennae for communication, the placement of deployable baffles, sunshields, and solar panels, etc. AsteroidFinder will also test space-based detection of space debris and artificial satellites at different observational attitudes. All this has to be fitted to the limited envelope of a compact class satellite; within the common envelope and power rating of a small household fridge, and no moving parts but one-time deployables. As of December 2008, AsteroidFinder/SSB is in preparation for phase B. Its launch is planned for 2012, for a one-year baseline mission

Small satellites for big science: the challenges of high-density design in the DLR Kompaktsatellit AsteroidFinder/SSB

The design of small satellites requires a paradigm shift in the thinking of satellite designers as well as mission scientists, payload users, and programme management - in brief, everyone involved. In a conventional approach, spacecraft design evolves in a mostly linear fashion from mission requirements by well-defined procedures through a series of reviews into a design space that is essentially not limited by constraints other than programmatic. The mission defines a pallet of instruments, their needs then shape the spacecraft bus, and the integrated spacecraft is finally mated to a dedicated launch, to be placed into an orbit carefully custom-tailored by mission analysis and continuously trimmed by on-board propulsion. Components are manufactured to spec, one-off plus spares, and painstaking testing has to iron out the many space firsts and compromises made in an arduous and protracted design process. Small satellite design reverses this comfortable line of thinking. It begins with hard, and not just programmatic constraints on most of the essential parameters that define a satellite. Launch as a secondary payload is the choice, not just for budgetary reasons, but due to the lack of viable dedicated launchers. It requires a small stowed envelope and a tightly limited mass budget. This results in limited surface area for solar panels and radiators. Small project volume enables a high flight cadence which makes re-use of designs and components desirable and feasible, in a self-catalyzing cycle. Re-use and constraints force the system perspective on every participant in a quick succession of sometimes diverging but generally converging iterations that lends itself to the Concurrent Engineering approach. There is simply no space left in a small satellite project for boxes to think in. To exploit the technological convergence that has created powerful and miniaturized science instruments and satellite components, the DLR research and development programme has initiated the Kompaktsatellit line of development. It is intended to enable dedicated missions for science projects that would earlier have resulted in one full-scale scientific instrument among many sharing a ride on a large platform without the perspective of follow-on within an academic career lifetime. In an internal competition, the AsteroidFinder instrument dedicated to the search for small bodies orbiting the Sun interior to Earth’s orbit has been selected as the payload to fly first on a Kompaktsatellit. Alongside, the Standard Satellite Bus kit, /SSB, is being developed, based on extensive re-use of experience, concepts, and components of the DLR satellites BIRD and TET. It is designed to avoid the overhead carried by pre-defined standard bus concepts while allowing for seamless integration of the payload into an organic spacecraft design. Challenges encountered and solutions found across the subsystems of AsteroidFinder/SSB will be presented