Middle Earth Orbit Research Articles

Deep operator and SSA collaboration for space sustainability

The space data association (SDA) has been providing reliable flight safety products for approximately 30 spacecraft operators for 14 years now. The service provides conjunction warnings and operator points of contact for around 700 spacecraft occupying all orbital regimes. The SDA's Space Data Center (SDC), built by AGI and maintained and operated by COMSPOC Corporation, has a proven track record of providing high availability space traffic coordination (STC) products since becoming operational on 15 July 2010.Earlier this year, the SDA, and its chief technical consultant, COMSPOC Corporation, supported the U.S. Department of Commerce (DOC) Geosynchronous Earth Orbit (GEO) and Middle Earth Orbit (MEO) Pilot project by providing comprehensively fused orbit solutions, ten-day orbit ephemeris and covariance predictions, and smoothed reference ephemerides for 100 active spacecraft. Most of these spacecraft are operated by SDA members and participants, allowing the operators to collaboratively contribute their maneuver plans, GPS NavSol measurements, active ranging, and passive RF observations, and authoritative spacecraft dimensions to the DOC Pilot project. For its part, COMSPOC employed its Space Situational Awareness (SSA) Software Suite (SSS)to comprehensively fuse this diverse set of spacecraft operator observations with COMSPOC's own observations from its global network of optical sensors.The first phase of this collaborative data fusion required the establishment of accounts, data connectivity, file transfer methods, and sensor calibration. This required about one month of technical interchange, provision of operator sensor locations and specifics, and COMSPOC SSS operator calibration of those sensors for each spacecraft.But once the data flows, sensor calibrations, and maneuver readers were completed, the second phase drew upon a nearly continuous stream of fused observations and maneuvers to yield accurate and timely predictive ephemerides and covariance time histories. These data products are well-suited to the collision avoidance problem.

High-speed inter-satellite link construction technology for navigation constellation oriented to engineering practice

Abstract This article presents a study on the design of high-speed inter-satellite links for the global navigation satellite system, which consists of 24 middle earth orbit, 3 inclined geosynchronous orbit, 3 geostationary orbit satellites, and 4 typical ground stations based on the laser link of slowly varying continuous system and high-speed Ka link. Pre-allocation of node connections in inter-satellite link construction is conducted by employing the optimized Dijkstra algorithm using finite-state automata. In addition, topological design and routing planning principles are utilized for high-speed inter-satellite links. Based on full constellation orbit data of a regression period and locations of the ground station nodes, an hourly link construction program is obtained using the scheme described above. The calculation result of the position dilution of precision values of all satellites, the average inter-satellite transmission delay, and the inter-satellite link switching meet the requirements of measurement, data transmission, and management for navigation constellation.

DIME-2 Flown as Part of NASA’s SET-1 on the DSX Satellite

The objective of the Dosimetry Inter-comparison and Miniaturization Experiment (DIME) approach is to compare different miniature electronic dosimeters for monitoring exposure to ionizing radiation primarily in terms of potential degradation due to total ionizing dose (TID) and the threat of single event effects (SEEs). As the title implies, DIME is divided in two parts: DIME-1 is a passive board that is turned on only to read the cumulative dose and DIME-2 is an active board that requires continuous power to monitor the radiation-induced energy depositions that can lead to SEE. This article describes the details of the operation of DIME-2 and the results of the flight on the Demonstration and Science Experiments (DSX) satellite which orbited the Earth in an elliptical middle earth orbit (MEO) orbit that extended from 6000 to 12 000 km at an inclination of 42° thereby crossing the entire slot region between the inner and outer electron belts. Measurements made every 15 min consistently showed a large peak in the energy depositions at perigee and a small one near apogee with fewer events in the slot region.

Variation of Permittivity and Dark Conductivity of Polyimide and FR4 With Electron Dose by Experiments

The internal charging effect may lead to electrostatic discharges (ESDs) for Geostationary Earth Orbit (GEO) and Middle Earth Orbit (MEO) satellites. This is due to the high-energy electrons that deposit in the dielectrics of satellites. The properties of the dielectrics such as permittivity and dark conductivity dominate this effect. This may contribute to the ESD risk of long-lifetime satellites if these properties change with the increase of electron dose. Two general materials, Polyimide (PI) and FR4 Epoxy Glass Cloth (FR4), were chosen as samples to study by experiments with different doses. The results show that the permittivity of PI and FR4 decreased as the dose increased while the dark conductivity increased. Numerical simulation evaluates the electron dose and the ESD risk of dielectrics under the electron environment of a specific MEO electron spectrum. The results show that the decrease of permittivity and the increase of dark conductivity will shorten the time constant of internal charging. The quicker build-up of electric field will increase the ESD risk if it exceeds the breakdown threshold.

Experimental Investigation of Surface Potentials of Materials Under Electron Spectra Representative of GEO and MEO Worst Case Environments

This paper presents a novel approach to test surface material charging under electron flux representative of space conditions below 400 keV. The experimental protocol used to test space material electrical properties consists in adapting the electron flux distribution to mimic worst case spectra met in space. Input environments are taken from Kp > 5 specifications at geosynchronous orbit (GEO) and from the analysis of both RBSP and LANL spacecraft data at middle Earth orbit (MEO) and GEO. Experimental results using GEO specifications show that the surface potential strongly depends on the energetic particle flux. Above a given > 100-keV electron flux, the radiation-induced conductivity tends to govern the charging dynamics. A numerical analysis based on the environments selected in this paper shows that charging levels could be larger at MEO than at GEO.

Comparison Between In-flight SEL Measurement and Ground Estimation Using Different Facilities

This paper describes a comparison between in-orbit single-event effects (SEE) rate measurement acquired by the CARMEN-3 experiment on-board the JASON-3 satellite (middle earth orbit, 1336 km, 66°) and an estimation using SEE rate calculation approaches from several facilities. A SRAM memory sensitive to single-event latchup (SEL) has been monitored in orbit, and the number of events per day was estimated using monoenergetic data coming from the Kernfysisch Versneller Instituut (protons) and Universite Catholique de Louvain (heavy-ions) facilities as well as using mixed-field data coming from the Cern High energy AcceleRator Mixed field (CHARM) facility. A comparison of both estimations with respect to the in-flight measurement has been carried out.

Relativistic effects to the onboard BeiDou satellite clocks

The relationship between the proper time of a satellite clock and the geocentric coordinate time (TCG) is discussed in the framework of general relativity. The influences of Earth's shape and the tidal potentials of the Sun and Moon are analyzed for onboard satellite clocks in different orbits. The results show that the influence of the shape of the Earth on Middle Earth Orbit (MEO) satellite reaches the level of 4.0 × 10-15, and it may be the direct cause of the half orbital-period variation in the clock frequency. The influences of the tidal potentials of the Sun and the Moon are relatively smaller. These influences on the frequencies of the clocks in the BeiDou MEO and GEO/IGSO (Geosynchronous Earth Orbit/Inclined Geosynchronous Satellite Orbit) satellites are 5.9 × 10-16 and 1.2 × 10-15, respectively, and appear to be half-day periodic variations. Therefore, these effects need to be considered in the precise assessment and application of BeiDou satellite clocks.

Description of the Code ANVIL (ANisotropic Vhf Impulse Location)

AbstractWe have developed a general, three‐dimensional method to locate sources of earth‐directed radiation that takes into account the flight paths of reflected signals. While time‐of‐arrival algorithms exist for locating radio sources using line‐of‐sight propagation paths, radio sources originating above the surface of the Earth will not necessarily emit strong power along direct paths to satellites. A combination of direct and ground‐reflected pulses or only ground‐reflected signals from such sources could be received by satellite‐borne sensors. The work presented here applies to satellite detection of subionospheric radio sources in a vacuum environment with ideal reflection off the Earth's surface. Because satellites are not static receivers, their configuration with respect to a radio source is not always optimal. Therefore, a statistical study is performed using 1,000 randomized configurations of 24 satellites in middle Earth orbit. For each configuration, the radio source latitude and longitude is fixed, and its altitude is varied from 1 to 97 km. An analytic direct‐path algorithm using the five satellites nearest the radio source provides an initial guess for the radio source latitude and longitude. We find that, using this approximation, the mean error in the calculated nadir location has a maximum value of 134 m for the 97‐km source altitude. The coordinates of the initial guess are used to define the origin of a grid within which an all‐points search refinement is performed. Using this procedure, the overall maximum mean error in radio source position is found to be on the order of the computational grid size.

Оценка зоны обслуживания станции приема и обработки информации среднеорбитального сегмента КОСПАС–САРСАТ

Оценка зоны обслуживания станции приема и обработки информации среднеорбитального сегмента КОСПАС–САРСАТ

Возможность и эффективность дополнения среднеорбитального сегмента системы КОСПАС–САРСАТ геостационарным сегментом этой системы

Возможность и эффективность дополнения среднеорбитального сегмента системы КОСПАС–САРСАТ геостационарным сегментом этой системы

Экспериментальная оценка точности определения координат медленно подвижных радиобуев в среднеорбитальном сегменте КОСПАС–САРСАТ

Экспериментальная оценка точности определения координат медленно подвижных радиобуев в среднеорбитальном сегменте КОСПАС–САРСАТ

Single satellite beam scanning positioning based on Neural Network BP algorithm

In this paper, the principle of single line positioning based on beam scanning and the neural network algorithm are analysing, and the neural network BP algorithm is applying to the single satellite positioning. At the same time, this paper presents a new algorithm based on electron beam (MEO) for the single scan positioning (Middle Earth orbit). Finally, through theoretical analysis and simulation, it is proving that the neural network BP algorithm of single satellite beam scanning is feasible in fast positioning.

Markov approximation for multilayered selection in satellite network

A satellite network system comprises three layers of satellites: LEO (Low Earth Orbit), MEO (Middle Earth Orbit) and GEO (Geostationary Orbit). In the system, users can choose a layer according to their demands, including QoS (Quality of Service), congestion, energy cost, etc. The utility that users gain will change when they access satellites in different layers. The mobility of satellites in the LEO and MEO leads to frequent handover among satellites in the same layer. These characteristics of multi-layered satellite networks make it possible for us to exploit the optimal distribution of users, which will maximize the utility of the entire satellite network. While the proposed problem is an NP-hard problem, we analyze the system based on the Markov chain and use the Markov approximation to approach the maximum utility. In addition, we use the count down and select algorithm to implement the process of Markov chain. The simulation results validate the convergence of the Markov approximation. In addition, the gap between the approximate value and optimal values decreases with an increase in ß, which is a positive constant in Markov formulation, according to the simulation results.

BeiDou Satellites Assistant Determination by Receiving Other GNSS Downlink Signals

GNSS’s orbit determinations always rely on ground station or intersatellite links (ISL). In the emergency of satellite-to-ground links and ISL break-off, BeiDou navigation satellite system (BDS) satellites cannot determine their orbits. In this paper, we propose to add a spaceborne annular beam antenna for receiving the global positioning system (GPS) and global navigation satellite system (GLONASS) signals; therefore, the BDS satellites may be capable of determining their orbits by GPS/GLONASS signals. Firstly, the spectrum selection, the power isolation, the range of Doppler frequency shift, and changing rate are taken into account for the feasibility. Specifically, the L2 band signals are chosen for receiving and processing in order to prevent the overlapping of the receiving and transmitting signals. Secondly, the minimum number of visible satellites (MNVS), carrier-to-noise ratio (C/N0), dilution of precision (GDOP), and geometric distance root-mean-square (gdrms) are evaluated for acquiring the effective receiving antennas’ coverage ranges. Finally, the scheme of deploying 3 receiving antennas is proved to be optimal by analysis and simulations over the middle earth orbit (MEO), geostationary earth orbit (GEO), and the inclined geosynchronous satellite orbit (IGSO). The antennas’ structures and patterns are designed to draw a conclusion that installing GPS and GLONASS receivers on BDS satellites for emergent orbits determination is cost-effective.

Visibility Analysis of Domestic Satellites on Proposed Ground Sites for Optical Surveillance

The objectives of this study are to analyze the satellite visibility at the randomly established ground sites, to determine the five optimal ground sites to perform the optical surveillance and tracking of domestic satellites, and to verify the acquisition of the optical observation time sufficient to maintain the precise ephemeris at optimal ground sites that have been already determined. In order to accomplish these objectives, we analyzed the visibility for sun-synchronous orbit satellites, low earth orbit satellites, middle earth orbit satellites and domestic satellites as well as the continuous visibility along with the fictitious satellite ground track, and calculate the effective visibility. For the analysis, we carried out a series of repetitive process using the satellite tool kit simulation software developed by Analytical Graphics Incorporated. The lighting states of the penumbra and direct sun were set as the key constraints of the optical observation. The minimum of the observation satellite elevation angle was set to be 20 degree, whereas the maximum of the sun elevation angle was set to be -10 degree which is within the range of the nautical twilight. To select the candidates for the optimal optical observation, the entire globe was divided into 84 sectors in a constant interval, the visibility characteristics of the individual sectors were analyzed, and 17 ground sites were arbitrarily selected and analyzed further. Finally, five optimal ground sites (Khurel Togoot Observatory, Assy-Turgen Observatory, Tubitak National Observatory, Bisdee Tier Optical Astronomy Observatory, and South Africa Astronomical Observatory) were determined. The total observation period was decided as one year. To examine the seasonal variation, the simulation was performed for the period of three days or less with respect to spring, summer, fall and winter. In conclusion, we decided the optimal ground sites to perform the optical surveillance and tracking of domestic satellites and verified that optical observation time sufficient to maintain the precise ephemeris could be acquired at the determined observatories.

A TECHNICAL OVERVIEW OF THE “SUNTOWER” SOLAR POWER SATELLITE CONCEPT

During 1995–1996, the National Aeronautics and Space Administration (NASA) conducted a far-reaching reexamination of the technologies, systems concepts and terrestrial markets that might be involved in future space solar power (SSP) systems. The principal objective of this “fresh look” study was to determine whether a solar power satellite (SPS) and associated systems could be defined that could deliver energy into terrestrial electrical power grids at prices equal to or below ground alternatives in a variety of markets, do so without major environmental drawbacks, and which could be developed at a fraction of the initial investment projected for the SPS Reference System of the late 1970s. One of the key concepts emerging from the “fresh look” SSP study is the “SunTower” SPS system. This concept exploits a variety of innovative technologies and design approaches to achieve a potential breakthrough in establishing the technical and programmatic feasibility on initial commercial SSP operations. Capable of being deployed to either low Earth orbit or middle Earth orbit altitudes and various inclinations, the SunTower concept involves essentially no in-space infrastructure and requires no unique heavy lift launch vehicle. The concept, which can provide power to global market places appears to allow up to a factor of 30:1 reduction in initial investment requirements, compared to the 1979 SPS Reference Concept. This paper presents a technical overview of the SunTower SPS concept, including key technologies, sensitivity trades, operational scenarios. Potential non-SPS space program uses of the SunTower concept and related technologies are identified, including human exploration, space science and commercial space applications.

A fresh look at space solar power: New architectures, concepts and technologies

The concept of generating solar power in space for wireless transmission to receivers on the ground has been discussed at some length during the past three decades. During the first decades of the new century, global demand for electrical power is projected to growth dramatically — perhaps doubling from 12 terawatts to more than 24 terawatts. Achieving this power growth while managing environmental impacts effectively is a crucial international challenge. During 1995–1996, the National Aeronautics and Space Administration (NASA) conducted a far-reaching reexamination of the technologies, systems concepts and terrestrial markets that might be involved in future space solar power (SSP) systems. The principal objective of this “fresh look” study was to determine whether a solar power satellite (SPS) and associated systems could be defined that could deliver energy into terrestrial electrical power grids at prices equal to or below ground alternatives in a variety of markets, do so without major environmental drawbacks, and which could be developed at a fraction of the initial investment projected for the SPS Reference System of the late 1970s. Working with a major focus on emerging nations — the study examined 5 different markets and about 30 different SPS concepts, ranging from the 1979 SPS Reference Concept defined by the US Department of Energy and NASA to very advanced concepts involving technologies which have not yet been validated in the laboratory. Following a preliminary assessment of technical and economic risks and projected costs, 7 SSP system architectures and 4 specific SPS concepts were chosen for examination in greater depth using a comprehensive, end-to-end systems analysis employing a desk-top computer modeling tool that was developed for the study. Several innovative concepts were defined and a variety of new technology applications considered. A key ground rule to achieve initial cost goals was to avoid wherever possible the design, development, test and evaluation costs associated with SSP-unique infrastructure. Three architectures in particular were identified as promising: a sunsynchronous low Earth orbit (LEO) constellation, a middle Earth orbit (MEO) multiple-inclination constellation, and one or more stand-alone geostationary Earth orbit (GEO) SPS serving single, dedicated ground sites. This paper presents a summary of the results of the “Fresh Look” Study, including architectures, systems concepts and technologies.