Experimental investigation of the modes of operation of uncontrolled attitude motion of the Progress spacecraft

by on 9 June 2015in Technology Development & Demonstration No comment

Results of in-flight tests of three modes of uncontrolled attitude motion of the Progress spacecraft are described. These proposed modes of experiments related to microgravity are as follows: (1) triaxial gravitational orientation, (2) gravitational orientation of the rotating satellite, and (3) spin-up in the plane of the orbit around the axis of the maximum moment of inertia. The tests were carried out from May 24 to June 1, 2004 onboard the spacecraft Progress M1-11. The actual motion of this spacecraft with respect to its center of mass, in the above-mentioned modes, was determined by telemetric information about an electric current tapped off from solar batteries. The values of the current obtained during a time interval of several hours were processed jointly using the least squares method by integration of the equations of the spacecraft’s attitude motion. The processing resulted in estimation of the initial conditions of motion and of the parameters of mathematical models used. For the obtained motions the quasi-static component of microaccelerations was computed at a point onboard, where installation of experimental equipment is possible.

Related URLs:
http://dx.doi.org/10.1134/S0010952506010059

Admissible Subspace TRajectory Optimizer (ASTRO) for Autonomous Robot Operations on the Space Station

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The paper presents the development of a real-time path-planning optimization approach to controlling the motion of space-based robots. The algorithm is capable of designing a trajectory for a robot to navigate within complex surroundings that include numerous obstacles (generalized shapes) and constraints (geometric and performance limitations). The methodology employs a unique transformation that effectively changes a complex optimization problem into one with a positive definite cost function that enables high convergence rates for complex geometries, enabling its application to real-time operations. The strategy was implemented on the Synchronized Position Hold Engage Reorient Experiment Satellite (SPHERES) test-bed on the International Space Station (ISS), and iterative experimental testing was conducted onboard the ISS during Expedition 17 but the first author.

Related URLs:
http://dx.doi.org/10.2514/6.2014-1290

Results of SPHERES Microgravity Autonomous Docking Experiments in the Presence of Anomalies

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In 2006 and 2007, the SPHERES testing facility, a series of micro-satellites developed by the MIT Space Systems Laboratory and designed to operate autonomously inside the International Space Station, has been extensively used to demonstrate multiple autonomous docking scenarios. Following the first autonomous docking to a tumbling target ever achieved on-orbit and presented at a conference last year, some off-nominal docking scenarios were attempted. Multiple autonomous docking maneuvers were achieved in the presence of simulated failures. In some situations, the chaser was required to perform a collision avoidance maneuver, which consisted in a simple thrust sequence that brought it on a safe trajectory. A docking maneuver was also attempted with a satellite tumbling such that its docking port swept a plane that does not include the chaser’s initial position, to simulate a servicing satellite docking to an uncontrollable target. One last scenario was an attempt to dock to a target satellite with its docking port sweeping a cone. Two different algorithms were used to perform some of these experiments. The first one involved a traditional glideslope approach, where the chaser is commanded to reduce its approach velocity with the distance-to-go. The second involved a pre-planned trajectory ensuring a passive abort in case a failure is detected. Following the success of these experiments, interesting conclusions were made on the performance of both algorithms, based on the observations during the experiments and the telemetry. This paper will present the results of these experiments, along with a comparison of the performance of both algorithms for the different scenarios attempted.

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New molecular technologies against infectious diseases during space flight

by on 9 June 2015in Technology Development & Demonstration No comment

Latent virus reactivation, reduction in the number of immune cells, decreased cell activation and increased sensitivity of astronauts to infections following their return on Earth demonstrate that the immune system is less efficient during space flight. This dysfunction during long-term missions could result in the appearance of opportunistic infections or a decrease in the immuno-surveillance mechanisms that eradicate cancer cells. On the other hand, monitoring of the microbial environment is essential to prevent infectious diseases in space. Therefore, both aspects will have to be monitored continuously during long-term missions in space, using miniature and semi-automated diagnostic systems. In the short term, such equipment will allow the study of the causes of space-related immunodeficiency, developing countermeasures to maintain an optimal immune function and improving our capacity to prevent infectious diseases during space missions. In order to achieve these objectives, a new diagnostic system has been designed to perform a set of biological and immunological assays on board spacecrafts. Through flow cytometric assays and molecular biology analyses, this diagnostic system will improve medical surveillance of astronauts and will be used to test countermeasures aimed at preventing immune deficiency during space missions.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0094576508000039

Implementation of Satellite Formation Flight Algorithms Using SPHERES aboard the International Space Station

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The MIT’s Space Systems Laboratory developed the Synchronized Position Hold Engage and Reorient Experimental Satellites (SPHERES) as a risk-tolerant spapceborne facility to develop and mature control, estimation, and autonomy algorithms for distributed satellite systems for applications such as satellite formation flight. Tests performed study interferometric mission-type formation flight maneuvers in deep space. These tests consist of having the satellites trace a coordinated trajectory under tight control that would allow simulated apertures to constructively interfere observed light and measure the resulting increase in angular resolution. This paper focuses on formation initialization (establishment of a formation using limited field of view relative sensors), formation coordination (synchronization of the different satellite’s motion) and fuel-balancing among the different satellites.

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Initial SPHERES Operations aboard the International Space Station

by on 9 June 2015in Technology Development & Demonstration No comment

The Satellite Position Hold Engage Reorient Experimental Satellites (SPHERES) program, developed by the MIT Space Systems Laboratory, began operations aboard the International Space Station (ISS) on May 2006. SPHERES was designed as a research facility to demonstrate metrology, control, and autonomy algorithms for distributed satellites systems. By operating in the risk-tolerant environment of the ISS, SPHERES allows researchers to push the limits of their algorithms. Five test sessions, conducted during 2006, achieved multiple objectives for the different areas under study. The first test session was dedicated to hardware checkout. The second test session demonstrated basic 6DOF closed-loop control of the satellites. Fault detection and isolation algorithms were also tested, successfully using the inertial measurement system to detect simulated faults in space. Formation flight tests during the fourth and fifth session demonstrated two types of control architectures. Following the principle of incremental algorithm development, demonstrations of multiple scenarios of spacecraft docking occurred during test sessions one through four; the last session demonstrated docking to a tumbling spacecraft. The results of these test sessions are the basis upon which substantial more research will be conducted in the following years.

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International Space Station acoustics – a status report

by on 9 June 2015in Technology Development & Demonstration No comment

It is important to control acoustic noise aboard the International Space Station (ISS) to provide a satisfactory environment for voice communications, crew productivity, and restful sleep, and to minimize the risk for temporary and permanent hearing loss. Acoustic monitoring is an important part of the noise control process on ISS, providing critical data for trend analysis, noise exposure analysis, validation of acoustic analysis and predictions, and to provide strong evidence for ensuring crew health and safety, thus allowing Flight Certification. To this purpose, sound level meter (SLM) measurements and acoustic noise dosimetry are routinely performed. And since the primary noise sources on ISS include the environmental control and life support system (fans and airflow) and active thermal control system (pumps and water flow), acoustic monitoring will indicate changes in hardware noise emissions that may indicate system degradation or performance issues. This paper provides the current acoustic levels in the ISS modules and sleep stations, and is an update to the status presented in 20031. Many new modules, and sleep stations have been added to the ISS since that time. In addition, noise mitigation efforts have reduced noise levels in some areas. As a result, the acoustic levels on the ISS have improved.

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SPHERES: a platform for formation-flight research

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New space missions, such as the Terrestrial Planet Finder (TPF) and Darwin programs, call for the use of spacecraft which maintain precise formation to achieve the effective aperture of a much larger spacecraft. Achieving this requires the development of several new space technologies. The SPHERES program was specifically designed to develop a wide range of algorithms in support of formation flight systems. Specifically, SPHERES allows the incremental development of metrology, control, autonomy, artificial intelligence, and communications algorithms. To achieve this, SPHERES exhibits a wide array of features to 1) facilitate the iterative research process, 2) support experiments, 3)support multiple scientists, and 4) enable reconfiguration and modularity. The effectiveness of these aspects of the facility have been demonstrated by several programs including development of system identification routines, coarse formation flight control algorithms, and demonstration of tethered systems.

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Physical and Biological Organ Dosimetry Analysis for International Space Station Astronauts

by on 9 June 2015in Technology Development & Demonstration No comment

In this study, we analyzed the biological and physical organ dose equivalents for International Space Station (ISS) astronauts. Individual physical dosimetry is difficult in space due to the complexity of the space radiation environment, which consists of protons, heavy ions and secondary neutrons, and the modification of these radiation types in tissue as well as limitations in dosimeter devices that can be worn for several months in outer space. Astronauts returning from missions to the ISS undergo biodosimetry assessment of chromosomal damage in lymphocyte cells using the multicolor fluorescence in situ hybridization (FISH) technique. Individual-based pre-flight dose responses for lymphocyte exposure in vitro to γ rays were compared to those exposed to space radiation in vivo to determine an equivalent biological dose. We compared the ISS biodosimetry results, NASA's space radiation transport models of organ dose equivalents, and results from ISS and space shuttle phantom torso experiments. Physical and biological doses for 19 ISS astronauts yielded average effective doses and individual or population-based biological doses for the approximately 6-month missions of 72 mSv and 85 or 81 mGy-Eq, respectively. Analyses showed that 80% or more of organ dose equivalents on the ISS are from galactic cosmic rays and only a small contribution is from trapped protons and that GCR doses were decreased by the high level of solar activity in recent years. Comparisons of models to data showed that space radiation effective doses can be predicted to within about a ±10% accuracy by space radiation transport models. Finally, effective dose estimates for all previous NASA missions are summarized.

Related URLs:
http://dx.doi.org/10.1667/RR1330.1