Geosynchronous Transfer Orbits Research Articles

Ridesharing Options from Geosynchronous Transfer Orbits to the Sun–Earth Region

Ridesharing options for secondary payloads to be delivered to regions beyond geostationary altitude are increasingly available with propulsive evolved expendable launch vehicle secondary payload adapter rings. The preliminary mission design for secondary payloads must consider the variability of the dropoff orbit orientation: a factor that is a function of the primary mission. In this analysis, assume that the dropoff orbit is an Earth-centered geosynchronous transfer orbit (GTO). Then, propellant-efficient transfers to periodic and quasi-periodic orbits near the Sun–Earth Lagrange point are constructed from a range of GTO orientations. Dynamical structures (such as hyperbolic invariant manifolds) associated with orbits near Sun–Earth Lagrange point are leveraged to identify and summarize various types of transfer opportunities.

Method and apparatus for removing orbital space debris from near earth orbit using the solar wind: Platform for redirecting and removing inert space material (PRRISM)

A Platform for Redirecting and Removing Inert Space Material (PRRISM) is a system utilizing an antenna generating an electromagnetic (EM) wave to interact with a solar EM wave to streamline magnetic flux in the Polar Cusp and to facilitate the flow of solar plasma through the Polar Cusp, resulting in an increased density, velocity, and pressure at the exit of the Polar Cusp. The elevated plasma flow intercepts and removes small space debris from Low Earth Orbit (LEO), Geosynchronous Earth Orbit (GEO) and Geosynchronous Transfer Orbits (GTO) transiting the LEO altitude regimes. Patent: US 10,501,212 B2, Dated: December 10, 2019

Sequential Low-Thrust Orbit-Raising of All-Electric Satellites

In this paper, we consider a recently developed formulation of the electric orbit-raising problem that utilizes a novel dynamic model and a sequence of optimal control sub-problems to yield fast and robust computations of low-thrust trajectories. This paper proposes two enhancements of the computational framework. First, we use thruster efficiency in order to determine the trajectory segments over which the spacecraft coasts. Second, we propose the use of a neural network to compute the solar array degradation in the Van Allen radiation belts. The neural network is trained on AP-9 data and SPENVIS in order to compute the associated power loss. The proposed methodology is demonstrated by considering transfers from different geosynchronous transfer orbits. Numerical simulations analyzing the effect of thruster efficiency and average power degradation indicate the suitability of starting the maneuver from super-geosynchronous transfer orbits in order to limit fuel expenditure and radiation damage. Furthermore, numerical simulations demonstrate that proposed enhancements are achieved with only marginal increase in computational runtime, thereby still facilitating rapid exploration of all-electric mission scenarios.

Geosynchronous transfer orbits as a market for impulse delivered by lunar sourced propellant

Every year around 100 metric tons of commercially addressable geostationary satellites are launched into geosynchronous transfer orbits (GTOs). The orbit raising from GTO to geostationary equatorial orbit (GEO) is an existing market for impulse that could be addressed by a service using propellant sourced from the Moon. We reconstructed the economic model in the recently published Commercial lunar propellant architecture: a collaborative study of lunar propellant production (Kornuta et al., 2019) and used it to investigate the financial viability of providing propulsion as a service in GTOs. We used NASA’s General Mission Analysis Tool to design a GTO service delivery flight plan, which we extend to cover sub and super synchronous delivery. We used economic, astrodynamic, and engineering models to derive the sensitivity of the internal rate of return to GTO launch costs, sale prices, tug inert mass fractions, and delivery orbit. While falling launch prices erode the impulse service returns, they may create other markets for propellant, we explore some higher return products these markets would make available.

Swarm Optimization of Lunar Transfers from Earth Orbit with Operational Constraints

Due to the frequent launches of primary satellites into geosynchronous transfer orbits, lunar transfer from an initial geosynchronous transfer orbit represents an attractive option for secondary payloads with lunar mission objectives. The development of advanced launch vehicle upper stages with low boil off rates and restartable engines further enhances the potential of geosynchronous transfer orbits to serve as starting points for lunar transfers. Lunar trajectory design from arbitrarily oriented Earth orbits involves complex tradeoffs that can be successfully addressed with particle swarm optimization. An important mission design consideration is radiation dose, since coasting in a geosynchronous transfer orbit involves repeated passes through the Van Allen radiation belts. In this investigation, a mixture density neural network is trained on the state-of-the-art radiation environment models to provide a surrogate model capable of making probabilistic estimates of radiation dosage. The network is combined with the particle swarm method to optimize the coasting and transfer arcs of a lunar trajectory. The end-to-end design of a trajectory from geosynchronous transfer orbit into a specified lunar orbit is demonstrated by modeling the optimized trajectory in a high-fidelity orbit propagator, including B-plane targeting to overfly a desired lunar landing site.

Dynamical lifetime survey of geostationary transfer orbits

In this paper, we study the long-term dynamical evolution of highly-elliptical orbits (HEOs) in the medium-Earth orbit (MEO) region around the Earth. The real population consists primarily of Geosynchronous Transfer Orbits (GTOs), launched at specific inclinations, Molniya-type satellites and related debris. We performed a suite of long-term numerical integrations (up to 200 years) within a realistic dynamical model, aimed primarily at recording the dynamical lifetime of such orbits (defined as the time needed for atmospheric reentry) and understanding its dependence on initial conditions and other parameters, such as the area-to-mass ratio (A/m). Our results are presented in the form of 2-D lifetime maps, for different values of inclination, A/m, and drag coefficient. We find that the majority of small debris (> 70%, depending on the inclination) can naturally reenter within 25-90 years, but these numbers are significantly less optimistic for large debris (e.g., upper stages), with the notable exception of those launched from high latitude (Baikonur). We estimate the reentry probability and mean dynamical lifetime for different classes of GTOs and we find that both quantities depend primarily and strongly on initial perigee altitude. Atmospheric drag and higher A/m values extend the reentry zones, especially at low inclinations. For high inclinations, this dependence is weakened, as the primary mechanisms leading to reentry are overlapping lunisolar resonances. This study forms part of the EC-funded (H2020) "ReDSHIFT" project.

Capability and Cost-Effectiveness of Launch Vehicles

Data for space launches and launch vehicles from 2000 to 2013 are analyzed to rate the relative capability and cost-effectiveness of launch vehicles for missions. The masses of mission payloads are used to determine the cost of payload mass delivered to low Earth and geosynchronous transfer orbits. These costs are higher due to wastage of launch vehicle capacity totaling 20.4% for the studied missions. A minimum cost scenario is then studied, where the lowest cost launch vehicle capable of performing a mission is used. In this scenario, the total price over the studied period for launches with complete data would be reduced from $44.2B to $33.4B, a savings of 24.5%. Usage is then compared with this scenario, and it is found that the cheapest launch vehicle capable of performing a mission is only used for 20.4% of studied missions.

Space debris mitigation strategies and practices in geosynchronous transfer orbits

Missions to geosynchronous orbits remain one of the most important elements of space launch traffic, accounting for 40% of all missions to Earth orbit and beyond during the four-year period 2000–2003. The vast majority of these missions leave one or more objects in geosynchronous transfer orbits (GTOs), contributing on a short-term or long-term basis to the space debris population. National and international space debris mitigation guidelines seek to curtail the accumulation of debris in orbits which penetrate the regions of low Earth orbit and of geosynchronous orbit. The orbital lifetime of objects in GTO can be greatly influenced by the initial values of perigee, inclination, and right ascension of the orbital plane, leading to orbital lifetimes of from less than one month to more than 100 years. An examination of the characteristic GTOs employed by launch vehicles from around the world has been conducted. The consequences of using perigees above 300 km and super-synchronous apogees, typically above 40,000 km, have been identified. In addition, the differences in orbital behavior of launch vehicle stages and mission-related debris in GTOs have been investigated. Greater coordination and cooperation between space launch service providers and spacecraft designers and owners could significantly improve overall compliance with guidelines to mitigate the accumulation of debris in Earth orbit.

Geosynchronous region orbital debris modeling with GEO_EVOLVE 2.0

GEO_EVOLVE, the NASA/JSC orbital debris simulation model for Earth's geosynchronous region, is in the process of being upgraded to version 2.0. The historical period of geosynchronous earth orbit (GEO) growth is mimicked with the addition of a set of updated and expanded launch/breakup files, and two new orbital propagators servicing objects in GEO and geosynchronous transfer orbits (GTO). This results in a GEO_EVOLVE 2.0 generated environment that is comparable with data from the US Space Surveillance Network (SSN) catalog and NASA's CDT (CCD Debris Telescope). The slow precession of the node and argument of perigee of objects near GEO has driven the development of a pair-wise collision probability algorithm for use in the projection phase of GEO_EVOLVE 2.0. This module is still in the preliminary testing phase.

Optimal Trajectories for Secondary Payloads from Geosynchronous Transfer Orbits to the Moon

Trajectories that provide fuel-efficient transfers from Geosynchronous Transfer Orbits (GTO) to the Moon are examined in this paper. These trajectories are becoming more important as relatively inexpensive launch options to GTO are now available by launching as a secondary payload. The main focus of this research is to explore possibilities for reaching lunar orbit via methods other than launching directly into the lunar orbit plane or waiting in a parking orbit for orbit perturbations to create favorable transfer conditions. Through the use of carefully chosen bi-elliptic type transfers or transfer orbits with optimally placed plane changes, this research shows that relatively efficient transfers to the Moon can be obtained from GTO.

GPS Receiver Architecture and Expected Performance for Autonomous Navigation in High Earth Orbits

ABSTRACT: GPS is an enabling technology for autonomous spacecraft navigation, including mission concepts involving formation flying in highly eccentric orbits. However, to date most spaceborne GPS applications have been limited to low earth orbits or postprocessing applications. This paper describes the problems associated with using GPS in the high earth orbit (HEO) environment and presents a GPS receiver design optimized for these applications. The design builds upon the PiVoT receiver developed by Goddard Space Flight Center by incorporating the GPS Enhanced Orbit Determination (GEODE) navigation filter, a high-quality clock, and enhancements to basic receiver acquisition and tracking algorithms. Predicted navigation performance for several representative missions, including geosynchronous and geosynchronous transfer orbits, is presented. The analysis shows that a modest reduction in the acquisition threshold of the receiver enables reliable navigation performance even in very high orbits with unfavorable antenna placement restrictions.

Use of an Expert System in Autonomous Orbit Control

Orbital Control (OC) is a vital aspect of every satellite mission. Traditionally, the process of OC and orbit determination (OD) has been very labour intensive. The analysis of the OD solution, the identification of anomalous behaviour and diagnosis of any problems that might occur, are all essentially made by the specialist. There is significant scope for the mundane and routine operations to be automated under software control, and for the experience and knowledge of the experts to be encapsulated in an Expert System. The paper will discuss the role of Expert Systems in OC with an emphasis placed on the practical implications and benefits that such systems can offer. A prototype system, that has been developed to cover the areas of Initial OD of Geosynchronous Transfer Orbits and the routine phase of OD of Geosynchronous Orbits, will be presented.

Catalog growth rate study (Hazard analyzed in geosynchronous transfer orbits)

Catalog growth rate study (Hazard analyzed in geosynchronous transfer orbits)