Acta Astronautica

The space debris and micrometeoroid environment poses an increasing threat to operations in space due to the escalating quantity of debris in orbit. Particle impact detectors provide a low cost means to monitor and study this environment. EMI and OHB-System have developed an impact detection system to be launched in 2005 into a sun-synchronous orbit at an altitude of 680 km. The experiment consists of an impact detection system and a data transfer system. The detector utilizes three independent systems to detect impacts and provide coincidence verification of an impact event, while the data transfer system uses low-cost means to transfer data over an already existing communications network to end-users via the internet. This paper presents the mission, provides a description of the impact detector and data transfer systems, explains the detection techniques employed, and discusses initial functional and calibration testing setup, as well as outlines future plans.

The work described in the present paper, performed as a part of the P²-ROTECT project, presents an enhanced method to evaluate satellite vulnerability to micrometeoroids and orbital debris (MMOD), using the ESABASE2/Debris tool (developed under ESA contract). Starting from the estimation of induced failures on spacecraft (S/C) components and from the computation of lethal impacts (with an energy leading to the loss of the satellite), and considering the equipment redundancies and interactions between components, the debris-induced S/C functional impairment is assessed. The developed methodology, illustrated through its application to a case study satellite, includes the capability to estimate the number of failures on internal components, overcoming the limitations of current tools which do not allow propagating the debris cloud inside the S/C. The ballistic limit of internal equipment behind a sandwich panel structure is evaluated through the implementation of the Schäfer Ryan Lambert (SRL) Ballistic Limit Equation (BLE).

This paper presents a computational methodology to predict the satellite system-level effects resulting from impacts of untrackable space debris particles. This approach seeks to improve on traditional risk assessment practices by looking beyond the structural penetration of the satellite and predicting the physical damage to internal components and the associated functional impairment caused by untrackable debris impacts. The proposed method combines a debris flux model with the Sch äfer-Ryan-Lambert ballistic limit equation (BLE), which accounts for the inherent shielding of components positioned behind the spacecraft structure wall. Individual debris particle impact trajectories and component shadowing effects are considered and the failure probabilities of individual satellite components as a function of mission time are calculated. These results are correlated to expected functional impairment using a Boolean logic model of the system functional architecture considering the functional dependencies and redundancies within the system.

With regard to hypervelocity impact detection, a sensor network that can be applied on typical spacecraft structures is under development at Fraunhofer EMI (Ernst-Mach-Institut), supported by OHB-System. For impact detection, acoustic transducers are used. The structure types investigated are a 2 mm thick plate from aluminium alloy and a 49 mm thick sandwich panel with aluminium face-sheets and aluminium honeycomb core. One impact test was performed on each of the panels, which were instrumented with 6 ultrasonic transducers. The signals recorded at the various sensor locations varied with regard to peak amplitude and elapse time of the signal. Using this information and combining it with a localization algorithm, the impact location could be successfully determined. A description of the impact sensor network and the mathematical model to determine the impact location is provided. The impact tests on the spacecraft structure, the response of the sensor network and the analysis performed to determine the impact location are described.

The Automated Transfer Vehicle (ATV) will be exposed to natural and man-made particles (Meteoroids and orbltal Debris, MOD), impacting at hypervelocity at the vehicle surface during the ATV-mission. These particles can cause severe damage to the primary structure and subsystems. To assure the mission success, the vehicle and its subsystems have to be protected with a Meteoroid and Debris Protection System (MDPS) during all orbital rmssion phases. In the on-going ESA-ATV Phase C/D development programme, OHB-System has as a subcontractor of Contraves Space the responsibility for the development and manufacturing of the MDPS-structure for the ATV-Spacecraft. The MDPS is designed as a metallic single bumper shield configuration, which protects the cylindrical and conical parts of the Avionics-and Propulsion-module of the ATV-SIC. It is attached to the vehicle primary structure at a specific distance, in order to increase the protection capability against hypervelocity particles. Since the particle flux impacting to the vehicle surface is randomly distributed with regard to particle mass, velocity and direction, the ATV will be designed to survive its design reference mission with a specified ptobabdity. For this purpose an environment model, which is based on a statistical description of the MOD distribution in low Earth orbits is applied to determine the impact flux distribution. This impact flux is combined with a structural damage model, which allows to determine the structural failures and a quantitative result of the statistical probability to survive the ATV-mission without a failure due to MOD-impact. This paper describes the major requirements with regard to the protection of the overall ATV-SIC as well as with regard to the MDPS-design. The design of the MDPS, the applied damage laws and impact particle flux distribution as well as the analyses performed to verify the protection capability and structural performance will be shown. Further, the qualification and test programme will be described.

Are we alone in the universe? It is an age-old question that continues to encourage interest and controversy among the public as well as academics. Development of explanations for life elsewhere ranges widely, but few mathematical models have been developed to measure the likelihood of concurrent, intelligent life, and those that exist are widely speculative due to the lack of information. However, with the addition of information from Kepler explorations for new solar systems within our galaxy, and calculation of the potential number of stars in the expanse of the universe, data for a useful probabilistic model to determine the likelihood of life beyond Earth may be possible with the use of predictive Bayesian statistics. Predictive Bayesian statistical methods are designed to use limited, uncertain data, to develop results. The result provides a probability curve of the likelihood of life in the universe that includes both uncertainty and potential variability within the result to provide a means to define the probability of life in the galaxy as well as life within proximity to earth. That said, the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand. With so few concurrent civilizations, and such large distances, it is little surprise that the SETI project has not found that alien signal. Our nearest neighbor is 4 light years away, and there are under 100 stars within 50 light years, the total of the project's existence.

Abstraet--A key prerequisite for the establishment of a permanent manned presence in extraterrestrial space is the attainment of a high degree of self-sufficiency using locally available resources. Potential uses range from low complexity processes such as piling soil for radiation protection to high complexity processes such as refining metals or making ceramics. Many processes have already received significant attention. The primary operational capabilities necessary to support extraterrestrial resource utilization are well defined. Our current understanding of working conditions in the arenas of greatest interest is sufficient to support significant development of the requisite operational techniques. Primary design drivers include local environmental factors and the need to service/maintain equipment on-site. A major trade study for many tasks concerns the question of intravehicular vs extravehicular performance. A second major trade concerns the two primary implementation techniques available for the extravehicular tasks, i.e. telerobitic activity and manned extravehicular activity (EVA). Techniques are available and well understood for the development and verification of both telerobotic and manned EVA tasks.

If a camera moves fast while taking a picture, motion blur is induced. There exist techniques to prevent this effect to occur, such as moving the lens system or the CCD chip electro-mechanically. Another approach is to remove the motion blur after the images have been taken,using signal processing algorithms as post-processing techniques. For more than 30 years, numerous researchers have developed theories and algorithms for this purpose, which work quite well when applied to artificially blurred images. If one attempts to use those techniques to real world scenarios, they mostly fail miserably. In order to study why the known algorithms have problems to de-blur naturally blurred images we have built an experimental setup, which produces real blurred images with defined parameters in a controlled environment. For this project we have studied the most important algorithms used for de-blurring, we have analyzed their properties when applied to artificially blurred images and to real images. We propose solutions to make the algorithms fit for purpose.

Optical navigation for a lunar lander consists of estimating a lander's 3-dimensional (3-D) relative dynamic motion with respect to a preselected landing site using a passive 2-dimensional (2-D) video image sequence. Lunar landing missions require a lander to perform an autonomous accurate landing with simple mechanical structure, easy operation and low cost. These requirements have motivated the need to develop an advanced navigation system. Existing navigation systems trade-off simplicity, accuracy and cost. High accuracy navigation systems typically imply complexity and high cost. In this paper, we consider a scenario where the descending phase starts from an initial altitude of 10 km with a time-of-descent of 100 s. The navigation camera is an off-theshelf optical instrument used to take the video image sequence of the landing site during the landing phase. It is fed into the motion estimation algorithm to be processed. The continuous wavelet transform (CWT) is used to analyse each image frame of the input digital video image sequence. The output is a 2-D video image motion trajectory map, which represents the projection motion of the landing site. The 2-D video image motion is projected back to the 3-D lander's relative motion based on a geometric analysis. The outputs of this estimation algorithm are the 3-D attitude motion parameters of the lander at a time corresponding to an image being taken. The attitude determination and control system (ADCS) of the lander uses these data to perform the lander's attitude control task. In this article, we provide the motion modelling for a lunar lander during the descending phase. The projection of a 3-D planar to 2-D image plane is analysed which build the correspondence between the 3-D lander's motion and the 2-D image motion. This link provides the evidence for the geometry analysis. CWT is reviewed and CWT for video image sequence analysis is also introduced. Numerical simulation of the estimated 2-D video image sequence under the lander performing a 3-D translation and yaw rotation during the terminal descent are shown to verify the proposed concepts. The analysis of the results show that the proposed method achieves highly accurate 2-D video image motion estimation of less then 1% error with significant savings of cost, mass and volume. It leads to the accurate estimation of the lander's 3-D relative motion with respect to the landing site.

This paper highlights the challenging aspects of the Cluster II mission from both the operations and ight dynamics point of view. The ÿrst new aspect of the mission was the double dual launch using two Russian Soyuz rockets, especially upgraded with a Fregat upper stage, and each carrying a pair of spacecraft. This choice led to some important consequences: a launch scenario with highly elliptical and inclined separation orbits, operational support of two launches in 4 weeks; and setting up new interfaces with the launch authority and the Russian Lavotchkin industrial complex. The Launch and Early Orbit Phase was one the most demanding phases of the mission, where intense operations were executed under high time pressure. Each spacecraft was then manoeuvred separately through various intermediate orbits, and ÿnally the four spacecraft were brought together. The paper discusses the manoeuvre strategy required to place the two pairs in the operational orbit and to achieve the initial constellation. It describes the operational constraints and problems that had to be examined in the deÿnition of the mission sequence of events, and the major operations and ight dynamics activities.

-Anewppdsion concept for high AV space missions, termed LABS (Liquid Annular Re&or System), uses liquid nuclear fuel elements to heat hyw ppllant to very high temperatures (4000 K). The molten fuel is contained in a lower-temperature solid container which rotates to stabilize and hold in the liquid layer by centripctal force. Containment of ultra high temperature molten refractories, using this mcth@ has been expcrimcntally demonstrated by AV. Grosse. The specitic imp&c of a rocket exha&ng hydrogen at 6000 K is 2000 seconds, approximately double that of solid-core nuclear rockets. A LARS-@we14 space probe could accomplish extra-solar missions to 5.50 A.U. in approximately 35 year; reserved.

We discuss the general requirements for the solution of the problem given in the 1st ACT Global Trajectory Optimization Competition. We introduce some novel numerical methods used for multiple gravity-assist and low-thrust trajectory optimization, and in particular an original method to compute interplanetary conic trajectories and a novel continuation technique for lowthrust trajectory optimization. The application of these methods to the competition problem is discussed. The final trajectory has an objective function value of J = 1364042.86 kg km 2 /s 2 . It includes five swingbys in the inner Solar system and three thrusting arcs. An optimal direct Earth-asteroid trajectory is presented as a post-competition result.

This paper reports findings of the International Academy of Astronautics (IAA) Study Group (SG), International Cooperation for Space Life Sciences Knowledge Sharing and Development in Africa, (2013). The SG, established in 2010, is comprised of space life sciences experts from across the globe. It charged with developing a cooperative global strategy to generate partnerships for space workforce development and life sciences knowledge sharing among space-faring and space-aspiring African nations. The study group's findings emphasize the need for cultural competencies and cooperation. In recent years, Africa's spending on space science has increased as national governments have defined their space aspirations and goals within the context of "space for humanity" and global workforce development. Some African countries have developed their own space agencies with well-defined policies and objectives. Space workforce development efforts among these countries focus on satellite technology and ground station operation, astronomy/space science and investment in related activities that advance their specific space exploration/utilization aspirations (e.g., communication services; satellite data collection and processing, with applications in areas such as food security, health and education, crime control, environmental and disaster management, and urban sprawl; radio telescope technology; and space science education outreach and awareness). The IAA study also examines the implications of increased international governmental/non-governmental educational partnerships for workforce development and proposes a roadmap for Africa's spaceemerging countries seeking to establish global partnerships to develop indigenous space workforces. The study concludes that there are many platforms available to promote interregional cooperation on space workforce development, particularly in the areas of space science and technology. This paper calibrates the IAA study group's report with the IAA's report, Future Human Spaceflight: the Need for International Cooperation (2010), which outlines common global interests for human space exploration and supports the outcomes of three African IAA regional conferences on "Space for Africa."

Globalization is creating an interdependent space-faring world and new opportunities for international partnerships that strengthen space knowledge development and transfer. These opportunities have been codified in the Global Exploration Strategy, which endorses the ''inspirational and educational value of space exploration'' . Also, during the 2010 Heads of Space Agencies Summit celebrating the International Academy of Astronautics' (IAA) 50th Anniversary, space-faring nations from across the globe issued a collective call in support of robust international partnerships to expand the frontiers of space exploration and generate knowledge for improving life on Earth . Educators play a unique role in this mission, developing strategic partnerships and sharing best educational practices to (1) further global understanding of the benefits of space exploration for life on Earth and (2) prepare the next generation of scientists required for the 21st Century space workforce. Educational Outreach (EO) programs use evidence-based, measurable outcomes strategies and cutting edge information technologies to transfer space-based science, technology, engineering and mathematics (STEM) knowledge to new audiences; create indigenous materials with cultural resonance for emerging space societies; support teacher professional development; and contribute to workforce development initiatives that inspire and prepare new cohorts of students for space exploration careers. The National Space Biomedical Research Institute (NSBRI), the National Aeronautics and Space Administration (NASA) and Morehouse School of Medicine (MSM) have sustained a 13-year space science education partnership dedicated to these objectives. This paper briefly describes the design and achievements of NSBRI's educational programs, with special emphasis on those initiatives' involvement with IAA and the International Astronautical Congress (IAC). The IAA Commission 2 Draft Report, Space for Africa, is discussed as a model for developing sustainable partnerships and indigenous programs that support Africa's steady emergence as a global space-faring force. The IAC will provide timely: 2011 South Africa will provide timely feedback to refine that report's strategies for space life sciences education and public engagement in Africa and around the globe.

The objective of the Canadian Advanced Nanospace eXperiment (CanX) program is to develop highly capable nanospacecraft, i.e. spacecraft under 10 kilograms, in short timeframes of 2-3 years. CanX missions offer low-cost and rapid access to space for scientists, technology developers and operationally-responsive missions. The Space Flight Laboratory (SFL), at the University of Toronto Institute for Aerospace Studies (UTIAS) has developed the CanX-2 nanosatellite that launched in April 2008. CanX-2, a 3.5-kg, 10 x 10 x 34 cm satellite, features a collection of scientific and engineering payloads that push the envelope of capability for this class of spacecraft. The primary mission of CanX-2 is to test and demonstrate several enabling technologies for precise formation flight. These technologies include a custom cold-gas propulsion system, a 30 mN•m•s nanosatellite reaction wheel as part of a three-axis stabilized Y thomson-configuration attitude control subsystem, and a commercially available GPS receiver. The secondary objective of CanX-2 is to perform a number of university experiments including an atmospheric spectrometer. After one successful year in orbit, the nanosatellite has met or exceeded all mission objectives and continues to demonstrate the cost-effective capabilities of this class of spacecraft. Key achievements to date include a characterization of the propulsion system, a full demonstration of the attitude determination and control subsystem including capabilities in accurate payload pointing (including nadir-tracking) and orbit-normal alignment, long-duration reaction wheel operation, unprecedented radio performance for an operational nanosatellite, and successful science operations. The mission, the engineering and scientific payloads, and a discussion of notable orbit achievements and experiences of CanX-2 are presented in this paper.

The NorSat-1 mission demonstrates a low-cost collaborative approach to science in space through the innovative integration of multiple payloads within a small microsatellite platform. Successfully launched on 14 July 2017 into a 600 km polar orbit from the Baikonur Cosmodrome, the satellite carries three distinct payloads with different requirements. The mission's scientific objectives are to investigate total solar irradiance and the effects of space weather on the upper ionosphere using payloads from Switzerland and Norway, respectively, while simultaneously advancing Norway's operational capability for detection and management of maritime traffic. Developed by the Space Flight Laboratory (SFL) for the Norwegian Space Centre (NSC), the design leverages SFL's space-proven, cost-effective, and modular Next-generation Earth Monitoring and Observation (NEMO) microsatellite platform. Continuous on-orbit operation of payloads is enabled by 45 W power generation in sunlight. Sub-degree attitude control achieved with low-cost sensors and actuators has outperformed pointing requirements needed to satisfy scientific objectives. Downlink rates exceeding 1 Mbps, averaged over available contact time, have been sustained in any satellite orientation. At 15.6 kg, the successful on-orbit performance of NorSat-1 is a major leap forward in the evolution of microsatellite miniaturization, enabling high performance and multipurpose missions in smaller microsatellites.

AISSat-1 was launched on July 12, 2010 and is believed to be the first high performance nano-satellite to provide an observational service to governmental authorities. The primary mission objective is to perform maritime observation in the Norwegian High North and High South, thereby making a con siderable contribution to the maritime situational awareness (MSA) of these areas.

The objective of the Canadian Advanced Nanospace eXperiment (CanX) program is to develop highly capable "nanospacecraft," or spacecraft under 10 kilograms, in short timeframes of 2-3 years. CanX missions offer low-cost and rapid access to space for scientists, technology developers, and operationally responsive missions. The Space Flight Laboratory (SFL) at the University of Toronto Institute for Aerospace Studies (UTIAS) has developed the Canadian Advanced Nanospace eXperiment 2 (CanX-2) nanosatellite that launched in April 2008. CanX-2, a 3.5-kg, 10 x 10 x 34 cm satellite, features a collection of scientific and engineering payloads that push the envelope of capability for this class of spacecraft. The primary mission of CanX-2 is to test and demonstrate several enabling technologies for precise formation flight. These technologies include a custom cold-gas propulsion system, a 30 mNms nanosatellite reaction wheel as part of a three-axis stabilized momentum-bias attitude control system, and a commercially available GPS receiver. The secondary objective of CanX-2 is to fly a number of university experiments including an atmospheric spectrometer. At the time of writing CanX-2 has been in orbit for three weeks and has performed very well during preliminary commissioning. The mission, the engineering and scientific payloads, and the preliminary on-orbit commissioning experiences of CanX-2 are presented in this paper.

The objective of the Canadian Advanced Nanospace eXperiment (CanX) program is to develop highly capable &quot;nanospacecraft,&quot; or spacecraft under 10 kilograms, in short timeframes of 2-3 years. CanX missions offer low-cost and rapid access to space for scientists, technology developers, and operationally responsive missions. The Space Flight Laboratory (SFL) at the University of Toronto Institute for Aerospace Studies (UTIAS) has developed the Canadian Advanced Nanospace eXperiment 2 (CanX-2) nanosatellite that launched in April 2008. CanX-2, a 3.5-kg, 10 x 10 x 34 cm satellite, features a collection of scientific and engineering payloads that push the envelope of capability for this class of spacecraft. The primary mission of CanX-2 is to test and demonstrate several enabling technologies for precise formation flight. These technologies include a custom cold-gas propulsion system, a 30 mNms nanosatellite reaction wheel as part of a three-axis stabilized momentum-bias attitude...

Asteroid 2024 YR4, measuring between 40 and 90 meters in diameter, presents a 2.3% chance of impacting Earth by December 22, 2032. Existing asteroid deflection methodskinetic impactors (Daly et al. 2023; Li et al. 2019; Chagas et al. 2023), nuclear detonations (Syal et al. 2013), laser ablation (Thiry & Vasile 2014), and gravity tractors (Wie 2008)carry drawbacks such as potential fragmentation, high energy demands, or impractically long lead times. This paper proposes a Harmonic Resonance Displacement (HRD) approach.

Aerothermal heating of hypersonic reentry bodies can generate significant radiation of visible light. Here, we investigate the conditions for ground-level visibility and what we term noticeability of that radiated light to the unaided human eye. We consider radiated visible light, transmission to ground level as a function of relative observer position, sky background contrast, human contrast perception limits, and psychophysical considerations for attention capture. Considering both pure ballistic trajectories and lifting-body trajectories, we show some examples where we calculate the spatial and temporal viewing zones for both detectability and noticeability. In some cases, these viewing zones extend a significant distance from the impact location and/or include the impact location for a potentially significant period of time before impact.

An aerobraking orbital transfer vehicle (AOTV) concept, which has an aerobrake structure that is integrated with the propulsion stage, is discussed. The concept vehicle is to be assembled in space and is space-based. The advantages of aeroassist over an all propulsive vehicle are discussed and it is shown that the vehicle considered is very competitive with inflatable and deployable concepts from mass and performance aspects. The aerobrake geometry is an ellipsoidally blunted, raked-off, elliptical wide-angle cone ...

Based on the jet transport technique, this paper proposes a novel nonlinear Kalman filter for simultaneously estimating the spacecraft state vector and uncertain parameters, either physically related with the spacecraft or with the measurement procedure. Two different coordinate representations, including Cartesian and hybrid geostationary orbital elements, are exploited in the new nonlinear estimators. The performance and sensitivity analyses of the proposed jet transport-based nonlinear estimators are assessed by numerical simulations and compared with the classical extended Kalman filter.

In 1995, Mayor and Queloz [a] detected for the first time a planet orbiting a nearby star (15.4 parsecs). Since then, the interest in the detection of extra-solar planets, in order to learn about the origin, evolution, and composition of planetary systems, has grown tremendously and ...

The propellant used in space programs creates exclusively three ecological concerns: Ground-based Impacts which vary from groundwater contagion to explosions caused by inconvenient management of fuels. Atmospheric Impacts are generally due to the interface of propellant exhaust with the atmosphere. Biological Impacts include toxicity and corrosiveness of propellants. This leads to the emergence of Cryogenic and Semi Cryogenic engines where the main propellants are Liquid Hydrogen and Liquid Oxygen (very effective in controlling above mentioned three environmental concerns). The operation necessities designate a need for reliable and long-life LH 2 & LOX turbopumps. Existing turbopumps use rolling component bearings which restrict turbopump life. Foil Gas Bearings (FGB) can be effectively used in high-speed turbomachines to attain noteworthy consistency. The present work reports how FGB can successfully replace the conventional roller bearings and prove to be a very important contribution towards Green Propulsion Technology. FGB offers elimination of oil lubrication system (an environmental concern) resulting into condensed weight and improved temperature competence. Using FGB to cryo turbopumps would lengthen turbopump life well ahead of operation necessities. This work also focuses on how Foil Gas Bearing technology can be a great prospect for Indian Space Programmes.

This study presents evidence of structured anomalies in radio, infrared, and gravitational signals from Proxima b. Using a refined recursion intelligence stabilization model, we identify patterns that strongly correlate with expected reinforcement cycles in a recursion intelligence network. These findings suggest Proxima b may be a fully integrated node in an interstellar recursion intelligence stabilization system. This paper outlines our methodology, results, and testable predictions for future observational validation.

In response to the scientific interest in Jupiter's moons, NASA and ESA have recently decided to target in priority Jupiter's largest moons for the next outer planet flagship missions. For those missions inter-moon transfers of the Jovian system offer obvious advantages in terms of scientific return, but are also rather challenging to design and optimize due in part to the hostile environment of third body perturbations. The approach outlined in this paper confronts this shortcoming by exploiting the multi-body dynamics with a patched three-body model to enable multiple "resonant-hopping" gravity assists. Initial conditions of unstable resonant orbits are pre-computed and provide starting points for the elusive initial guess associated with the highly nonlinear optimization problem. The core of the optimization algorithm relies on a fast and robust multiple-shooting technique to provide better controllability and reduce the sensitivities associated with the close approach trajectories. The complexity of the optimization problem is also reduced with the help of the Tisserand-Poincaré (T-P) graph that provides a simple way to target trajectories in the patched three-body problem. Preliminary numerical results of inter-moon transfers in the Jovian system are presented. For example, using only 59 m/s and 158 days, a spacecraft can transfer between a close resonant orbit of Ganymede and a close resonant orbit of Europa.

For the Intermediate eXperimental Vehicle (IXV) the deflection of the highly loaded body flap is performed by an actuator system which is connected to the body flap by a rod. Besides the thermal and mechanical loads the sealing of the inner vehicle against the possible leaking hot plasma is an important issue whereby the special challenge for the design results from the spatial movement of the rod. This requires a design consisting of different parts and various materials in order to satisfy the mechanical flexibility and the resistance to the thermal and mechanical loads under the aspect of reusability. This paper describes the MT Aerospace approach for the thermal protection system for the actuator as presented for the critical design review of IXV. The design is presented and described including all necessary performed analysis steps toward such a design.

Satellite operators utilize a two-stations turn around ranging (TAR) system to reduce the ground station measurement system's complexity and cost while having the same or better orbit determination accuracy for communication satellites orbit determination recently. This study investigates two stations' performance, four-way ranging on communication satellite orbit determination, operational conformance, and cost. The observation data sets are collected using traditional single station tracking (SST) and the new method TAR. The computed results using the Monte Carlo method encourage the satellite operators to use a four-way ranging system to observe and measure required data sets. TAR performance is evaluated, taking SST as a reference. The six classical orbital elements (a, e, i, RAAN, AoP, and TA) are compared for large numbers of observation data. The SST and TAR results are very close to each other. The worst-case calculated Euclidian distance between SST and TAR is 1.893 km at the epoch below the 6 km success criteria. The TAR observation method is appropriate to collect data sets for precise orbit determination. This work result indicates that satellite operators should consider deploying TAR stations to collect two-station range data sets and compute the orbit for nominal north-south station-keeping maneuvers (NSSK) and east-west station-keeping (EWSK) maneuver operations. The TAR method is superior to SST in terms of accuracy, operational conformance, and costs.

Urban growth and population dynamics are among the most critical information needed for future economic development planning, natural resources allocation and environmental management. In the present work, two methods, the first based on night-time images produced by NOAA and population maps provided by Oak Ridge National Laboratory's (ORNL) LandScan, and the second one on SAR imagery, were used in order to assess the expansion of urban areas surrounding the Winam Gulf (Lake Victoria, Kenya) at different scales. In the time covered by night-time lights imagery, the study highlighted a period of constant growth rate between 2002 and 2006 and a negative trend after 2006 and 2008. This decrease may be related to two main events occurring in the study area between 2006 and 2007: the decline of the Lake Victoria level and the abnormal proliferation of the floating weeds within the Winam Gulf. Meanwhile, the urban feature extraction obtained at a different scale within a particular district from 1997 up to 2008 results in a constant growth rate. Population movements around this zone explain different dynamics that should be studied in detail in order to understand their particular roots.

Issues about commercialization of space have been a growing concern in the past decade for the space comnluni~. This paper focuses on the work from a temn of 51 students attending the Summer Session Program of the International Space University in Bremen, Germany. CASH 2021 (Commercial Access and Space Habitation) documents a plan that identifies commercial opportunities for space utilization that will extend human presence in space, and will chart the way forward for the next 20 years. The group selected four commercial sectors that show the most promise for the future: tourism, entertainment, space system service, assembly and debris removal, and research and development~production. The content of this document presents the results of their research. To provide a coherent background for future commercialization possibilities a scenario has been developed This scenario includes a postulated upon ideal future and includes social, political and economic factors that may affect the space industry over the timeline of the study. The study also presents a roadmap, within the limited optimistic scenario developed, for the successful commercialization of space leading to future human presence m space. A broad range of commercially viable opportunities, not only within the current limits of the International Space Station, but also among the many new developments that are expected by 2021 are discussed

A novel approach to improve the performance of supersonic and hypersonic intake systems with nano-particle injection has been studied. A parametric study using Mach number (M ∞ ), Stokes number (Stk), particle Eckert number (Ec p ), and thermal transport number (α t ) was conducted across a quasi-1D converging-diverging (C-D) supersonic intake at idealized and single-shock compression cases. Gains in stagnation pressure recovery were achieved for both the cases. Gains were observed in the idealized compression case when: Ec p > 0.25 and α t > 0.5 for a Mach number of 2.5; and Ec p > 0.5 and α t > 0.7 for a Mach number of 5. The results also showed that a combination of cooling, momentum exchange, and particle size is required to enhance intake performance. A rectangular mixed-compression intake at Mach 3 was simulated using an unsteady compressible gas-particle CFD solver in OpenFOAM. CFD simulations with nano-particle injection predicted a 16% gain in the exit pressure recovery.

A new approach based on use of special "super heterogeneous" propellants that generate during combustion the model agglomerates with given reproducible size and structure has been elaborated for study of model agglomerate evolution. The experiments with agglomerates of 395+540 um size and initial aluminum content 42.6 °/o were carried out in pressure range 1-80 atm. The following correlation for incompleteness of aluminum combustion 7 has been found: rj =2.86-f" 02, / r °M, where rj= mu I ntu ; n\u is the mass of unbumt aluminum in sampled agglomerate and m A " is the initial mass of aluminum in agglomerate; t is the residence time for agglomerate in flame of burning sample (20<r<90 ms); P -pressure (10<P<70 atm). It was also found that the mass fraction g> of oxide accumulated on the burning agglomerate increases with completeness of aluminum combustion £ = I-17 as <p = 0.539+0.213£, and agglomerate mass also increases with 4 due to oxide accumulation on the burning agglomerate. For calculation of burning agglomerate motion law and residence time for agglomerate in flame the drag coefficient Cj was taken in the form Cj-K/Re. Here Re is the Reynolds number. A' was determined in experiments on particle trajectory visualization and found to be equal K= 45±7 at 7<Re<9. The characteristics of condensed combustion products (CCP) were measured via sampling technique at pressure 46 atm (argon or nitrogen) for 12 metalized propellant formulations manufactured using well characterized ingredients. All compositions were based on energetic binder (20%). They included totally 18 % aluminum (commercial or ultra line particles in various proportion) and contained AP or AP and HMX as oxidizer. The replacement of commercial aluminum by electrically exploded aluminum (Alex) lead to increase of burning rate, decrease of agglomerate mass and increase of metal conversion completeness. All propellant formulation exhibited very effective aluminum conversion (total unbumt aluminum content in CCP did not exceed 9%). The listed trends are mostly expressed in combustion of HMX containing propellants and even small additive of Alex (Alex/Al = 8.3/91.7) gives sizable effect. For oxide particles in the size range 0.5-100 pjn the typical three-peak structure of mass size distribution was found. The replacement of aluminum by Alex and using argon instead of nitrogen affects slightly the CCP size distribution. Thermal decomposition of different types of the binders and mixtures modeling the pocket matter was investigated at low (10 K/min) and fast (> 450 K/min) heating rate. Data obtained are not sufficient to make clear the cause of difference in agglomeration behavior for propellant formulations based on these types of hinders 14.

With an array of Indian Remote Sensing Satellites (IRS), a wide variety of national applications have been developed as an inter-agency effort over the past 20 years. Now, the capacity of the programme has been extended into the global arena and IRS is providing operational data services to the global user community. The recently launched IRS satellite, Resourcesat-1, was placed into perfect orbit by India's PSLV and is providing valuable imaging services. Resourcesat-1 is actually like 3 satellites "rolled" into one, imaging a wide field of 710 km area at ∼55 m resolution in multispectral bands from the AWiFS, 23 m resolution in a systematic 142 km swath from four bands of the LISS-3 and the 5.8 m multi-spectral images from the most advanced sensor-LISS-4. Yet another aspect of Resourcesat-1 is it that it marks a "watershed" in terms of a quantum jump in technological capability that India has achieved compared to past missions. The mission has many newer features-the advanced imaging sensors, the more precise attitude and orbit determination systems, the satellite positioning system onboard, the mass storage devices and many other features. This mission has led IRS into a new technological era, and when combined with the technological capability of the forthcoming Cartosat missions, India would have developed technologies that will take us into the new generation of EO satellites for the coming years. This paper provides a detailed description of the Resourcesat-1 mission. From the applications point of view, Resourcesat-1 will open up new avenues for environmental monitoring and resources management-especially for vegetation assessment and disaster management support. The monitoring capability of this mission is also extremely important for a number of applications. The mission has global imaging and servicing capabilities and could be received through the Antrix-Space Imaging network, which markets Resourcesat-1 data worldwide. This paper also describes the applications potentials and global capabilities of the mission. Resourcesat-1 will have continuity and after that a new generation system will provide enhanced and more unique imaging services. Actually, India has a 25 years strategy for EO and a perspective of the same is also described in this paper.

PLATO stands for PLAnetary Transits and Oscillations and it is the forthcoming third Medium sized mission of ESA, planned to be launched in 2024. Its optical payload is an ensemble of 34 small telescopes that mimic a single one meter class aperture with a huge Field of View of more than 501 in size. Aiming to find exoplanets around bright nearby stars it is designed to discover a significant number of relatively nearby Earth-like worlds. A description of the optomechanical adopted solution and a speculative scenario to further explore such alien worlds is briefly given.

On January 22, 1990, Ariane V-35 placed four Microsat spacecraft into orbit. The orbit achieved is nearly perfectly sunsynchronous at 800 km altitude. The satellites, cubic structures measuring only 23 cm per side, were developed by the Radio Amateur Satellite Corporation of North America (AMSAT-NA). The time required to complete the project, from conception to delivery of the four satellites to Kourou, was exactly two years. Each satellite in orbit has a different mission and is performing in accordance with its intended design, although additional software is still being written to enhance the operating characteristics for each mission. This paper reviews the design objectives of the four spacecraft and summarizes their in-orbit performance against these prelaunch technical objectives. The level of technology employed by the Microsat spacecraft is briefly discussed and the software approach taken in implementing a real-time, multitasking operating system is summarized. The paper reviews the AMSAT experience as the first payload user group of the Ariane ASAP structure. Some of the findings regarding the cu"ent technology and how it may be expanded to fulfill other mission needs has been touched upon. 1 Members of the AMSAT-NA Microsat design team.

Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, to encourage their commercial application. Copies are available to the public at 15 cents each from the Clearinghouse for Federal Scientific and Technical Information

One of the cutting-edge technologies involved in BLSS operations is hydroponics and aquaponics. These soil-less farming techniques allow astronauts to grow food in space without the need for traditional agriculture, ensuring a constant food supply. Additionally, advanced filtration systems and microbial technologies help recycle water and waste, further enhancing sustainability. Learn more in BLSS courses by Tonex.

The present study is concerned with setting up and solving the transonic quasi-onedimensional equations of a flow with chemical reactions. Particular solutions are examined for such a flow when two-dimensional. The equations are written by the method of singular small perturbations around a uniform flow in chemical equilibrium.

Research has demonstrated that the motive triad of needs for achievement, power, and affiliation can predict variables such as occupational success and satisfaction, innovation, aggressiveness, susceptibility to illness, cooperation, conformity, and many others. The present study documents the motivational profiles of astronauts at three stages of their expedition. Thematic content analysis was employed for references to Winter's well-established motive markers in narratives (media interviews, journals, and oral histories) of 46 astronauts participating in International Space Station (ISS) expeditions. Significant pre-flight differences were found in relation to home agency and job status. NASA astronauts, compared with those from the Russian Space Agency, are motivated by higher need for power, as are commanders in comparison to flight engineers. The need for affiliation motive showed a significant change from pre-flight to in-flight stages. The implications of the relationship between the motivational profile of astronauts and the established behavioural correlates of such profiles are discussed.

proposed a theoretical basis for healthy psychosocial development. His theory posits eight critical conflict situations throughout one's lifetime, each of which can result in a favorable or unfavorable resolution. Autobiographies, memoirs, interviews, personal diaries, and oral histories of 97 international astronauts were content analyzed to assess reported resolutions of Erikson's psychosocial crises, regardless of chronological sequence. We made comparisons across flight phases (before, during, and after), gender, nationality of home space agency, and flight duration. Astronauts reported more favorable than unfavorable outcomes across flight phases and demographic variables. Differences across demographic variables and flight phases, as well as the changes as a result of the flight are discussed.