Low Orbit Space Research Articles

Low cost and high performance double‐node upset resilient latch for low orbit space applications

SummaryThis paper proposes a double‐node upset complete resilient (DNUCR) latch to meet the requirements of low orbit space applications for high robustness, cost‐effectiveness, and high performance. With the help of its interlocked loops with multiple feedbacks consisting of C‐elements (CE), input splitting CEs, 1P‐2N and 2P‐1N elements, and inverters, the proposed DNUCR latch preserves the original data even after the radiation incident. Error injection simulations in Synopsys HSPICE show that the proposed DNUCR latch recovers from all DNUs and can withstand large amount of injected charge. The simulation outcomes further show that the proposed DNUCR latch outperforms existing DNU‐resilient latches in terms of delay, power consumption, and power–delay–area product (PDAP), with an average of 48% reduction in delay, 22% savings in power, and 60% reduction in PDAP. The proposed DNUCR latch is also found to be the best among the existing radiation‐hardened latches in terms of charge‐to‐PDAP ratio.

Analysis of the Impact of Atmospheric Models on the Orbit Prediction of Space Debris

Atmospheric drag is an important influencing factor in precise orbit determination and the prediction of low-orbit space debris. It has received widespread attention. Currently, calculating atmospheric drag mainly relies on different atmospheric density models. This experiment was designed to explore the impact of different atmospheric density models on the orbit prediction of space debris. In the experiment, satellite laser ranging data published by the ILRS (International Laser Ranging Service) were used as the basis for the precise orbit determination for space debris. The prediction error of space debris orbits at different orbital heights using different atmospheric density models was used as a criterion to evaluate the impact of atmospheric density models on the determination of space-target orbits. Eight atmospheric density models, DTM78, DTM94, DTM2000, J71, RJ71, JB2006, MSIS86, and NRLMSISE00, were compared in the experiment. The experimental results indicated that the DTM2000 atmospheric density model is best for determining and predicting the orbits of LEO (low-Earth-orbit) targets.

Damage, recovery, and the geographies of military–civil entanglements

ABSTRACT This paper explores two forms of entanglements between military and civilian phenomena and activities, in contexts of recovery from damaging events. One concerns global civil–military entanglements in low earth orbital space, where recovery from damage is necessary for sustaining the civilian and military service support systems on which we increasingly depend. The other uses the damage caused by the UK state’s regimes of financial austerity to highlight how gendered, spatialized forms of personal labour through military Reserve forces sustain recovery. Both suggest ways in which military and political geography and geographers can find new ways of thinking through civil–military entanglements.

Ballistic Coefficient Calculation Based on Optical Angle Measurements of Space Debris.

Atmospheric drag is an important factor affecting orbit determination and prediction of low-orbit space debris. To obtain accurate ballistic coefficients of space debris, we propose a calculation method based on measured optical angles. Angle measurements of space debris with a perigee height below 1400 km acquired from a photoelectric array were used for orbit determination. Perturbation equations of atmospheric drag were used to calculate the semi-major-axis variation. The ballistic coefficients of space debris were estimated and compared with those published by the North American Aerospace Defense Command in terms of orbit prediction error. The 48 h orbit prediction error of the ballistic coefficients obtained from the proposed method is reduced by 18.65% compared with the published error. Hence, our method seems suitable for calculating space debris ballistic coefficients and supporting related practical applications.

ORBITAL STRUCTURE OPTIMIZATION TECHNIQUE OF THE LOW-ORBIT COMPLEX OF ON-ORBIT SERVICE

Most of the currently planned on-orbit servicing (OOS) missions involve the use of disposable OOS spacecraft. The use of disposable OOS spacecraft may be profitable in the near future. But it is not a reliable solution for OOS in the long term. As an alternative, a more useful concept is the use of reusable OOS complexes, which allow responding to scheduled and random requests from OOS clients. This concept can ensure the timeliness and efficiency of OOS implementation during planned services and random requests of OOS clients. However, despite the potential advantage of a reusable OOS, the design of its orbital structure and operational maintenance is much more complicated in comparison with the traditional concept of the organization of OOS. This is because when planning the response of reusable OOS complexes to requests, it is necessary to distribute OOS client service operations between space vehicles of the reusable OOS complex. Now the space industry is switching its attention to the area of low Earth orbits. This causes an increase in deployed and planned low-orbit satellite groups, the number of satellites in them, the difference in structural schemes of satellite groups, and the significant influence of the environment on orbital parameters. As you know, the orbital parameters of low orbits of space vehicles can differ significantly, and the difference between them can reach tens or even hundreds of degrees in the longitude of the ascending node. This leads to unacceptably high energy costs for modern OOS spacecraft for active rotation of the planes of their original orbits to the planes of the destination orbits. In some works, the possibility of reducing these energy costs due to the use of the difference in the speed of the nodal precession of the parking and destination orbits of the OOS spacecraft due to the non-centrality of the Earth’s gravitational field is considered. However, due to the long wait of the OOS spacecraft in the parking orbit, the flight time with the wait between the parking and destination orbits increases significantly. Its reduction can be achieved by increasing the number and rational selection of the semi-major axis and inclination of the parking orbits of the OOS spacecraft. The purpose of the article is to develop a technique for the optimal synthesis of the orbital structure and optimal operational planning of the low-orbit OOS complex in near-Earth orbits with a small eccentricity. Methods for solving the problem are the averaging method, the branch-and-bound method, and the multiobjective optimization method. The novelty of the obtained results lies in the development of a technique for optimal synthesis of the orbital structure and optimal operational planning of the low-orbit space OOS complex in near-Earth orbits with low eccentricity. The developed technique can be used in the previous planning and design of space OOS complexes in low near-Earth orbits with a small eccentricity.

Automation of the procedure for forming APAA subaperture structure of low-orbit space SAR missions

Automation of the procedure for forming APAA subaperture structure of low-orbit space SAR missions

Research on Magnetic-Induced Error of Small-Sized Fiber Optic Gyro Fiber Coil in Space Environment

Spacecraft is severely limited in weight and volume, resulting in a small bending radius of the fiber coil used by IFOG (Interference Fiber Optic Gyroscope). The fiber coil has such a size that the influence of bending on fiber birefringence cannot be ignored. In this paper, we research magnetic-induced errors of small-sized IFOG working in low orbit space. Firstly, we use the Jones matrix to analyze the effects of radial magnetic field and axial magnetic field on IFOG. Secondly, we establish a three-dimensional model for the radial magnetic-induced errors and magnetic-induced errors of minor radius fiber coil. Using the finite element method, we analyze the magnetic-induced error between different levels of the fiber coil. Combined with the birefringence distribution of the minor radius fiber coil, an accurate three-dimensional magnetic-induced error model is established. Thirdly, in the experiment, we design the magnetic-induced error test platform that includes the Fluke standard current source, transconductance amplifier, and Helmholtz coil. The experimental results show that, compared with the traditional calculation method, the three-dimensional magnetic-induced error model reduces the RMSE (Root Mean Square Error) of the radial magnetic field by 56.9% and the RMSE of the axial magnetic field by 35.7%, respectively.

Проблемы реализации облачных технологий в низкоорбитальных космических системах персональной спутниковой связи и передачи данных и телеуправление

Currently, a steady trend has been formed for targeted informatization of the intelligence community. This is explained by the fact that in the current conditions of the political, economic and technological environment, information technologies are considered as an innovative tool for increasing the capabilities and competitiveness of the state while saving money. Purpose of the study: At present, the creation of a glob- al low-orbit space information system, which is based on a multi-satellite orbital constellation of small-sized spacecraft based on the principle of cluster organization, is currently relevant. The essential difference between the global low-orbit space information systems a cloud network is that the existing cloud technologies are adapted for terrestrial non-mobile computers, among which a significant part plays the role of not computers, but simply data storage devices and "holders". Thus, the problem arises of ensuring the controllability of the GKNIS with limited computing resources for each of the individual spacecraft that make up the space system. It is unlikely that there will be an effective way to solve this problem by including separate "large" spacecraft in the space system, the mass and dimensions of which will allow installing a powerful onboard computer on board to allow such spacecraft to play the role of computing nodes within the orbital system. It is obvious that the economic viability of the GKNIS will primarily depend on the ability to use in its composition spacecraft of precisely small mass and dimensions, unified by the platform of service systems and produced in-line by a conveyor method. The development of such a technology could be a key moment in the creation of an economically viable global low-orbit space information system. Results: The paper deals with the problems of managing the management of a multifunctional satellite communication system in solving problems of information exchange using cloud technologies.

Research on thermal design and thermal optical performance of space telescope based on multidisciplinary integration

This paper first analyzes the external heat flow of a low-orbit space telescope in different flight attitudes, and determines the position of the heat dissipation surface and the thermal analysis cases. Then, the detailed thermal design of each component of the telescope is completed to reduce the influence of thermal deformation of optical elements and supporting structures caused by temperature changes on the imaging quality of telescope. Especially for the thermal control difficulties of CCD detectors such as large heat generation in a short time and one-dimensional movement in a narrow space, a segmented proprietary cold chain with flexible section is designed to transfer the heat to the radiant cold plate. Finally, the thermal/structure/optical integrated simulation analysis under extreme cases is carried out. It is concluded that the average modulation transfer function (MTF) of the optical system at the cutoff frequency satisfies the design requirement greater than 0.3. The analysis results show that the thermal control system designed in this paper can ensure the optical performance of the telescope, which has important reference significance for the thermal design of other space telescopes.

Appearance formation of the Earth remote sensing low-orbit space systems

Appearance formation of the Earth remote sensing low-orbit space systems

Assessment of the capabilities of orbital optical devices for obtaining information about space objects

The purpose of the study is to select the optimal conditions for collecting non-coordinate information about a spacecraft by a space optical-electronic means at the time objects pass the vicinity of the points of the minimum distance between their orbits. The quantitative indicator is proposed that characterize the measure of the possibility of obtaining non-coordinate information about space objects with the required level of quality. The arguments of the function characterizing the indicator are the distance between spacecraft; their relative speed; phase angle of illumination of a spacecraft by the Sun in relation to the optical-electronic means; the length of the time interval during which both objects are in the vicinity of the point of a minimum distance between their orbits. The value of the indicator is computed by solving three particular research problems.
 The first task is to search for neighborhoods that include the minimum distances between the orbits of the controlled spacecraft and optical-electronic means. To solve it, a fast algorithm for calculating the minimum distance between orbits used. Additionally, the drift of the found neighborhoods is taken into account on the time interval up to 60 hours.
 The second task is to estimate the characteristics of motion and the conditions of optical visibility of a controlled spacecraft in the vicinity of the minimum points of the distance between the orbits of spacecraft. The solution to this problem is carried out by using the SGP4 library of space objects motion forecast.
 The third task is justification and calculation of an index characterizing the measure of the possibility of obtaining an optical image of a spacecraft for given conditions of optical visibility. To solve the problem, the developed system of fuzzy inference rules and the Mamdani algorithm is used.
 The presented method is implemented as a program. In the course of a computational experiment, an assessment was made of the possibility of obtaining non-coordinate information on low-orbit and geostationary space objects. The proposed indicator provides an increase in the efficiency of the procedure for collecting non-coordinate information about space objects by choosing the most informative alternatives for monitoring space objects from the available set of possible observations at a given planning interval for collecting information about space objects.

МОДЕЛЬ СИСТЕМИ ВИЗНАЧЕННЯ ВИДУ ФАЗОВОЇ МАНІПУЛЯЦІЇ ТА СИМВОЛЬНОЇ ШВИДКОСТІ В РАДІОЛІНЯХ КОСМІЧНИХ СИСТЕМ

The article proposes a model of a universal automated system for determining the type of phase manipulation and symbol rate for receiving the flow of data by ground-based means transmitted in the radio lines of low-orbit space systems under a partial prior uncertainty. The relevance of the study on the selected topic is that in the last decade there has been noted a significant increase in the number of space systems operating in low-Earth orbits. The afore-mentioned fact leads to an increase in the variety of radio line structures of space systems, which creates a partial prior uncertainty in relation to the parameters of radio signals transmitted by these systems. At the same time, the operation of space systems in low-Earth orbits imposes restrictions on the duration of the communication session, which makes it difficult to set up the ground-based demodulating equipment under conditions of a partial prior uncertainty of the radio signal parameters. Considering the above, the article presents a possible option for designing a structure chart of a universal automated system for determining the type of phase manipulation and symbol rate. The principle of system operation is described and its operability is substantiated by mathematical modelling processes. The considered model of the universal automated system for determining the type of phase manipulation and symbol rate enables to determine the nominal value of the central carrier frequency of the radio signal, radio spectrum width, symbol rate and one of three types of phase manipulation (BPSK, QPSK, 8PSK) in the time operation mode close to real one. By the results of calculations being made, it is established that the system under study can be used while receiving data from space systems operating in low-Earth orbits. Also, the proposed system can be applied to determine the basic parameters of radio signals and other systems that use radio lines with phase manipulation. Further research on the selected topic will be aimed at studying the possibility of expanding the number of types of manipulations that can be automatically determined by the proposed system.

Universal Low-Orbit Space Platforms for Interacting Micro- and Nanosatellites of Earth Remote Sensing and Disaster Monitoring (Twinsat-Rs Project)

A project was designed to create a universal low-orbit space platform that meets the requirements on joint satellites operation in paired structures (space duo) for high-resolution radar imagery; constructing topographic maps and determining the movements of the Earth’s surface to assess seismic hazard and prevent natural and man-made disasters; indicating and determining the parameters of moving objects; constructing high-speed intersatellite communication systems, etc.

Lidar model of the formation of a sodium laser star when space objects are being observed and angularly tracked

This paper discusses a lidar model of the formation of a sodium laser star for the measurement and adaptive correction of atmospheric phase distortions in a ground-based optical system when space objects are being observed and angularly tracked. The energy characteristics of the laser star are studied when it occupies various angular positions in the visibility zone of a ground-based optical system. Requirements are formulated on the energy characteristics of a laser for forming a laser star in order to implement adaptive phase-matched correction of atmospheric phase distortions when low-orbit space objects are being observed.

Observability of hydrogen-rich exospheres in Earth-like exoplanets

Context. The existence of an extended neutral hydrogen exosphere around small planets can be used as evidence of the presence of water in their lower atmosphere, but, to date, such a feature has not been securely detected in rocky exoplanets. Planetary exospheres can be observed using transit spectroscopy of the Lyman-α line, which is limited mainly by interstellar medium absorption in the core of the line, and airglow contamination from the geocorona when using low-orbit space telescopes. Aims. Our objective is to assess the detectability of the neutral hydrogen exosphere of an Earth-like planet transiting a nearby M dwarf using Lyman-α spectroscopy and provide the necessary strategies to inform future observations. Methods. Our tests require spatial and velocity information of the neutral hydrogen particles in the upper atmosphere. The spatial distribution is provided by an empirical model of the geocorona, and we assume a velocity distribution based on radiative pressure as the main driver in shaping the exosphere. We compute the excess absorption in the stellar Lyman-α line while in transit, and use realistic estimates of the uncertainties involved in observations to determine the observability of the signal. Results. We found that the signal in Lyman-α of the exosphere of an Earth-like exoplanet transiting M dwarfs with radii between 0.1 and 0.6 R⊙ produces an excess absorption between 50 and 600 ppm. The Lyman-α flux of stars decays exponentially with distance because of interstellar medium absorption, which is the main observability limitation. Other limits are related to the stellar radial velocity and instrumental setup. Conclusions. The excess absorption in Lyman-α is observable using LUVOIR/LUMOS in M dwarfs up to a distance of ~15 pc. The analysis of noise-injected data suggests that it would be possible to detect the exosphere of an Earth-like planet transiting TRAPPIST-1 within 20 transits.

A Prediction Model for the Type of Consumer Willing to Travel to and Live on Mars

Technological advancements in space travel have brought the concept of private, commercial space transportation closer to reality. Companies such as Blue Origin and Virgin Galactic are working to offer commercial, low orbit space flights to paying customers, and SpaceX is even considering private trips to Mars. As these developments become closer to reality, an essential and missing gap in the literature relates to identifying what type of person would be willing to travel to and live on Mars. The purpose of this study was to develop and validate a statistical model to identify the significant predictors of a participant's willingness to travel to and live on Mars with 536 participants. The findings from the study indicate that nine of the 18 variables were significant predictors. Model fit was assessed through three measures and found to exist for the statistical model. The paper concludes with a discussion of the significant predictors, practical applications, and recommendations for future research.

Mathematical modeling and analysis of motion of a low-orbital space tether system

The paper analyzes the motion of a low-orbital space tether system, which consists of a main spacecraft and a sub-spacecraft connected by a tether. The total tether length is several ten kilometers. We considered deployment phase, the free motion phase and the stabilization motion phase on a low and nearly circular orbit. In the stabilization motion phase the orbital altitude of the system is kept in a given range by a corrective thruster. The corrective thruster is located on the main spacecraft. The simulation for all motion phases of the system is based on a mathematical model with distributed parameters, in which the tether is considered as a sequence of point masses with one-sided elastic mechanical coupling.

EFFICIENCY OF MOTION CONTROL OF SPACE SENSOR PHOTOGRAPHING LOW ORBITAL SPACE OBJECTS

Principles of observations and design of onboard equipment for obtaining optical images of low-orbiting space objects during flight at crossed courses are considered. It is noted that photographing from the distance of about 50 km allows to obtain images of space objects with linear resolution of about 1 dm. Simulation model of observation process by satellites-photographers was developed for the modes of their passive and controlled movement. The statistics of observability by one and two satellitesphotographers of low-orbiting space objects are calculated: dynamics of growth of the number of observed objects from distances of 30 and 50 km during one-year observation cycle, and the difference in dynamics in the modes of passive and controlled movement. An algorithm of controlling the motion of satellite-photographer for increasing productivity of obtaining photographs is proposed and described. The simulation of this algorithm has shown that control of the movement of satellite-photographer with reserve of characteristic velocity of 100 m/s provides significant increase in the number of photographed low-orbiting space objects. At distances to the object not exceeding 50 km the effectiveness of observations due to control increases from 80 to 98%, and the proportion of rendezvous from distance of 30 km will be 93%.

ACCURACY OF SATELLITE OPTICAL OBSERVATIONS AND PRECISE ORBIT DETERMINATION

The monitoring of low-orbit space objects (LEO-objects) is performed in the Astronomical Observatory of Odessa I.I. Mechnikov National University (Ukraine) for many years. Decades-long arсhives of these observations are accessible within Ukrainian network of optical observers (UMOS). In this work, we give an example of orbit determination for the satellite with the 1500-km height of orbit based on angular observations in our observatory (Int. No. 086). For estimation of the measurement accuracy and accuracy of determination and propagation of satellite position, we analyze the observations of Ajisai satellite with the well-determined orbit. This allows making justified conclusions not only about random errors of separate measurements, but also to analyze the presence of systematic errors, including external ones to the measurement process. We have shown that the accuracy of one measurement has the standard deviation about 1 arcsec across the track and 1.4 arcsec along the track and systematical shifts in measurements of one track do not exceed 0.45 arcsec. Ajisai position in the interval of the orbit fitting is predicted with accuracy better than 30 m along the orbit and better than 10 m across the orbit for any its point.

Innovative focal plane design for large space telescope using freeform mirrors

Increasing the size of low-orbiting space telescopes is necessary to attain high-resolution imaging for Earth or planetary science, which implies bigger and more complex imaging systems in the focal plane. The use of homothetic imaging systems such as the Spot and Pleiades push-broom satellites would lead to prohibitive linear focal plane dimensions, especially for IR missions requiring large-volume cryostat. We present two optical TMA telescopes using an image-segmentation module based on astronomical image slicer technology developed for integral field spectroscopy, made of a set of freeform mirrors defined by Zernike polynomials. Each telescope has a linear 1.1° field of view; the first one considers a matrix detector and the second one considers several linear TDI detectors currently used in space missions. We demonstrate that such systems provide efficient optical quality over the full field and offer a substantial gain in terms of volume of the focal plane arrays.