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

Potential effects of optical solar sail degredation on trajectory design

The optical properties of the thin metalized polymer films that are projected for solar sails are assumed to be affected by the erosive effects of the space environment. Their degradation behavior in the real space environment, however, is to a considerable degree indefinite, because initial ground test results are controversial and relevant inspace tests have not been made so far. The standard optical solar sail models that are currently used for trajectory design do not take optical degradation into account, hence its potential effects on trajectory design have not been investigated so far. Nevertheless, optical degradation is important for high-fidelity solar sail mission design, because it decreases both the magnitude of the solar radiation pressure force acting on the sail and also the sail control authority. Therefore, we propose a simple parametric optical solar sail degradation model that describes the variation of the sail film's optical coefficients with time, depending on the sail film's environmental history, i.e., the radiation dose. The primary intention of our model is not to describe the exact behavior of specific film-coating combinations in the real space environment, but to provide a more general parametric framework for describing the general optical degradation behavior of solar sails. Using our model, the effects of different optical degradation behaviors on trajectory design are investigated for various exemplary missions

In-situ Magnesium Diboride Superconducting Thin Films grown by Pulsed Laser Deposition

Superconducting thin films of MgB2 were deposited by Pulsed Laser Deposition on magnesium oxide and sapphire substrates. Samples grown at 450C in an argon buffer pressure of about 10-2 mbar by using a magnesium enriched target resulted to be superconducting with a transition temperature of about 25 K. Film deposited from a MgB2 sintered pellet target in ultra high vacuum conditions showed poor metallic or weak semiconducting behavior and they became superconducting only after an ex-situ annealing in Mg vapor atmosphere. Up to now, no difference in the superconducting properties of the films obtained by these two procedures has been evidenced.Comment: 10 pages, 4 figure

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

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

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