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961.
MIRAS is the Microwave Imaging Radiometer with Aperture Synthesis developed under ESA contract, in order to image the ground soil moisture and the ocean salinity from low Earth orbit.
High potential exists for application of this technology in space at low frequency, but low frequency means high antenna dimmensions with potential difficulties in terms of radiating elements correlation and measurements stability.
Based on the foreseen difficulties, ESA envisages a reduced size intermediate instrument compatible with small satellites which is named MIRAS demonstrator.
This paper presents the implementation of the MIRAS antenna demostrator on a Spanish MINISAT platform.
MINISAT programme of small satellites is part of the Spanish National Space plan. The first element of the serie (MINISAT 01) will be launched in December-96. 相似文献
962.
Glasauer S Amorim MA Bloomberg JJ Reschke MF Peters BT Smith SL Berthoz A 《Acta Astronautica》1995,36(8-12):423-431
To investigate changes in spatial orientation ability and walking performance following space flight, 7 astronaut subjects were asked pre- and post-flight to perform a goal directed locomotion paradigm which consisted of walking a triangular path with and without vision. This new paradigm, involving inputs from different sensory systems, allows quantification of several critical parameters, like orientation performance, walking velocities and postural stability, in a natural walking task. The paper presented here mainly focusses on spatial orientation performance quantified by the errors in walking the previously seen path without vision. Errors in length and reaching the corners did not change significantly from pre- to post-flight, while absolute angular errors slightly increased post-flight. The significant decrease in walking velocity and a change in head-trunk coordination while walking around the corners of the path observed post-flight may suggest that during re-adaptation to gravity the mechanisms which are necessary to perform the task have to be re-accomplished. 相似文献
963.
Gabrion J Herbute S Oliver J Maurel D Davet J Clavel B Gharib C Fareh J Fagette S Nguyen B 《Acta Astronautica》1995,36(8-12):439-448
Fluid and electrolyte shifts occuring during human spaceflight have been reported and investigated at the level of blood, cardio-vascular and renal responses. Very few data were available concerning the cerebral fluid and electrolyte adaptation to microgravity, even in animal models. It is the reason why we developed several studies focused on the effects of spaceflight (SLS-1 and SLS-2 programs, carried on NASA STS 40 and 56 missions, which were 9- and 14-day flights, respectively), on structural and functional features of choroid plexuses, organs which secrete 70–90 % of cerebrospinal fluid (CSF) and which are involved in brain homeostasis. Rats flown aboard space shuttles were sacrificed either in space (SLS-2 experiment, on flight day 13) or 4–8 hours after landing (SLS-1 and SLS-2 experiments). Quantitative autoradiography performed by microdensitometry and image analysis, showed that lateral and third ventricle choroid plexuses from rats flown for SLS-1 experiment demonstrated an increased number (about x 2) of binding sites to natriuretic peptides (which are known to be involved in mechanisms regulating CSF production). Using electron microscopy and immunocytochemistry, we studied the cellular response of choroid plexuses, which produce cerebrospinal fluid (CSF) in brain lateral, third and fourth ventricles. We demonstrated that spaceflight (SLS-2 experiment, inflight samples) induces changes in the choroidal cell structure (apical microvilli, kinocilia organization, vesicle accumulation) and protein distribution or expression (carbonic anhydrase II, water channels,…). These observations suggested a loss of choroidal cell polarity and a decrease in CSF secretion. Hindlimb-suspended rats displayed similar choroidal changes. All together, these results support the hypothesis of a modified CSF production in rats during long-term (9, 13 or 14 days) adaptations to microgravity. 相似文献
964.
The nature of the changes of resistance to infection seems to be very important. Our studies indicate that different functions of natural killers could be depressed after the spaceflight. The decrease of the percentage of the lymphocytes that can bind target cells lead to the lowering of the “active” NK level and this can be resulted in the depression of total NK activity and lowering of resistance to viral and tumor antigens. The investigation of natural killer cells in cosmonauts before and after short and long-term spaceflights also revealed the important role of spaceflight duration, stress and individual immune reactivity. 相似文献
965.
Here are reported preliminary results of the “Synergy” experiment performed aboard the Russian orbital station “MIR” in July 1993 (Altaïr Mission). The experiment was carried out before, during, and after the space flight of two astronauts (S1 and S2). The duration of the flight was 21 days for S1 and 6 month for S2. The subjects were tested during preflight, inflight and postflight. The astronaut subjects were fixed on the ground by the feet. They were asked to pick up a box in front of them on the ground. Two velocities of movement and two distances of the target to be reached were tested. The movement of several small markers placed on the body was recorded on video tape.
Results show that the shape of head and hand trajectories in the sagittal plane remains roughly the same during the flight in spite of the modification of mechanical constraints. Trajectory invariance does not result in joint angular displacement invariance. These data indicate that the planning of the movement takes place in terms of head and hand trajectories rather than joint rotations as it was previously suggested for simple arm reaching movement. 相似文献
966.
Guell A 《Acta Astronautica》1995,35(4-5):271-280
The article presents the current status of lower body negative pressure (LBNP) as a countermeasure for preventing orthostatic intolerance after space flight or bed rest. Devices discussed include the Chibis vacuum suit, the Anthrorack device, a collapsible device, and an inflatable device. Two bed rest studies examined the effect of LBNP and exercise on orthostatic tolerance; plasma volume; vasopressin, plasma renin activity, and catecholamines; and side effects. 相似文献
967.
Sadique P.MUHAMMED;Rafic M.AJAJ;Kamran A.KHAN 《中国航空学报》2020,33(10):2575-2588
This paper presents the development of a novel compliant polymorphing wing capable of chord and camber morphing for small UAVs. The morphing wing can achieve up to 10% chord extension and ±20° camber changes. The design, modeling, sizing, manufacturing and mechanical testing of the wing are detailed. The polymorphing wing consists of one continuous front spar fixed to the fuselage and a rear spar on each side of the wing. Each rear spar can translate in the chordwise direction(chord morphing) and rotate around itself(camber morphing). A flexible elastomeric latex sheet is used as the skin to cover the wing and maintain its aerodynamic shape whilst allowing morphing. The loads from the skin are transferred to the spars using the compliant cellular ribs that support the flexible skin and facilitate morphing. Pre-tensioning is applied to the skin to minimize wrinkling when subject to aerodynamic and actuation loads. A rack and pinion actuation system,powered by stepper motors, is used for morphing. Aero-structural design, analysis and sizing are conducted. Performance comparison between the polymorphing wing and the baseline wing(non-morphing) shows that chord morphing improves aerodynamic efficiency at low angles of attack while camber morphing improves efficiency at high angles of attack. 相似文献
968.
A comparison of temporal profiles of low-energy ion intensity and magnetic field magnitude in different periods of solar activity in the outer heliosphere is carried out using the data of the Voyager 1 and Voyager 2 spacecraft. It is shown that temporal, spectral, and statistical characteristics of particle fluxes and magnetic field in the heliospheric regions before and after the terminal shock in 2002–2008 had similar dynamics in different hemispheres. This similarity allowed one to assume that, in the region of the inner heliospheric boundary, a quasistable spatial structure existed moving together with the terminal shock in accordance with the solar wind pressure, as well as, probably, under the action of the interstellar medium. It was revealed that the spatial dimensions of most details of this structure are less on Voyager 2, which, probably, is due to variation of the solar activity level, difference in latitude of spacecraft disposition, and also the influence of the interstellar magnetic field. 相似文献
969.
A. A. Shirinzadeh H. H. Asadov I. Sh. Maharramov N. G. Javadov S. B. Jalilov 《Cosmic Research》2010,48(6):550-552
970.
G E Bingham S B Jones D Or I G Podolski M A Levinskikh V N Sytchov T Ivanova P Kostov S Sapunova I Dandolov D B Bubenheim G Jahns 《Acta Astronautica》2000,47(11):839-848
The control of water content and water movement in granular substrate-based plant root systems in microgravity is a complex problem. Improper water and oxygen delivery to plant roots has delayed studies of the effects of microgravity on plant development and the use of plants in physical and mental life support systems. Our international effort (USA, Russia and Bulgaria) has upgraded the plant growth facilities on the Mir Orbital Station (OS) and used them to study the full life cycle of plants. The Bulgarian-Russian-developed Svet Space Greenhouse (SG) system was upgraded on the Mir OS in 1996. The US developed Gas Exchange Measurement System (GEMS) greatly extends the range of environmental parameters monitored. The Svet-GEMS complex was used to grow a fully developed wheat crop during 1996. The growth rate and development of these plants compared well with earth grown plants indicating that the root zone water and oxygen stresses that have limited plant development in previous long-duration experiments have been overcome. However, management of the root environment during this experiment involved several significant changes in control settings as the relationship between the water delivery system, water status sensors, and the substrate changed during the growth cycles. 相似文献