Objects In Geostationary Orbit Research Articles

YORP Effect on Long-Term Rotational Dynamics of Debris in GEO

The Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect describes the torque induced on space objects produced by solar radiation and thermal re-emission. Previous analyses have demonstrated its influence on long-term rotational dynamics of space debris objects in Geostationary Orbit (GEO), where YORP becomes predominant with respect to other external perturbations (e.g., atmospheric drag, gravity gradient, eddy current torque), leading to a wide variety of possible behaviors. The capability of forecasting time windows of slow uniform rotation, if any, would bring significant advantages in operations of Active Debris Removal and on-orbit servicing, especially in the detumbling phase. Also, a non-negligible impact of the End-of-Life configuration, in terms of movable surfaces orientation and center of mass location, could lead to guidelines for future satellites to be easier targets in the disposal phase. In this work, a previously derived semi-analytical tumbling-averaged YORP rotational dynamics model is leveraged. Exploiting an averaged model, computational time is strongly reduced while maintaining sufficient accuracy compared to propagation of Euler’s equations of motion. First, a satellite of the Geostationary Operational Environmental Satellite (GOES) family is analyzed and compared to previous studies to verify the correct implementation of the model. A wider analysis is performed on simple geometric models, such as a box-wing satellite, a 3U CubeSat, and a rocket body. The impact of object size, surface optical properties, and center of mass position on long-term rotational behavior is investigated, providing a general insight into these phenomena with a possible future application to existing objects in GEO.

Using photometric data to describe the behaviour of objects in geostationary orbit

Using photometric data to describe the behaviour of objects in geostationary orbit

Optimal transfer schemes between space debris objects in geostationary orbit

The paper compares two variants of re-orbiting space debris objects from the geosynchronous (GEO) region. Under the first re-orbiting variant, a spacecraft-collector transfers between target objects (87 upper stages). Each object is re-orbited into a disposal orbit (DO) using special thruster de/re-orbiting kits (TDK) which are placed on space debris objects by the collector. Under the second variant, the object is pushed to a DO by the collector itself, which then moves to a new space debris object from the previous object's DO. It is shown that due to the slow evolution of the orbital parameters in the GEO region, the same transfer schemes can be used for both re-orbiting variants. We describe orbits in the near-equatorial region and consider two transfer schemes between objects. Under the first scheme, a transfer is executed when the orbits have the same inclination near the equator, and under the second scheme, when the orbit of the next object has the smallest inclination. Calculations show that both schemes are practically equivalent in terms of both the averaged ΔV for a transfer and the duration — however, not all objects under consideration can be covered under the first scheme. Hence, priority should be given to the second scheme. It can be calculated, that 6 collectors are required to clean the GEO protected region from spent upper stages. The service of each is expected to be at most 8 years and its required ΔV budget is at most 0.7 km/s. A re-orbiting of one object to a DO requires on average only 10 m/s; the return to a new object from the DO of the previous object is nearly energetically equal to a sequential transfer between the objects. In this regard, as distinct from low orbits (in which it is preferable to use TDKs), it is more beneficial to follow the second variant for re-orbiting space debris objects from the GEO region (i.e., using the collector itself).

Method of graphoanalytical finding borders space-time areas of reachability service spacecraft man-made space objects in geostationary orbit

At the present time at various stages of creation and development there are several projects of service spacecraft. One of the tasks of which is to service orbital objects as soon as possible. During the planning maintenance is needed to perform a large amount of calculations associated with the choice of a rational flight scheme. To reduce the amount of computation, an approach is needed that provides a search for the set of realized flight paths. One of such approaches is the method for determining the boundaries of the spatiotemporal reachability regions, which allows one to evaluate the a priori capabilities of service spacecraft for servicing orbital objects located in circular orbits. To construct spatiotemporal reachable regions, the mathematical apparatus of the hodograph theory is used, which allows, sequentially, based on the analytical solution of the optimization problem of a two-pulse flight, to determine the minimum and maximum duration of the spacecraft’s movement, which is understood as the time required for the flight from the point of maneuvering to the meeting point with the serviced an orbital object under the condition of the application of one velocity impulse. A graphical comparison of the trajectories of the serviced orbital objects and spatiotemporal reachable areas of the service spacecraft makes it possible to determine the potential for service, as well as the time intervals and phase angles at which such service is possible. The proposed methodological apparatus can be used to find a solution providing an initial approximation for the subsequent accurate calculation of the trajectory of motion by numerical methods, as constructing a control program for the spacecraft.

Proximity scenario design for geostationary rendezvous with collocated satellite avoidance

Proximity operation is one of the prerequisites for in-orbit service or debris removal. Especially for objects in geostationary orbit (GEO), there are certain challenges in rendezvous and proximity operations, such as perturbed relative dynamics and constraints from collocated satellites. In this study, a novel optimization model is built to design the GEO proximity scenario, including the keeping points and durations of each phase. First, as a prerequisite of proximity scenario design, relative dynamics considering solar radiation pressure effects and the corresponding two-point boundary value problem are analytically solved. Second, the concept of passive safety performance is introduced. The safety constraints from both the target satellite and the collocated satellites are considered. The optimization model is then built, and an improved differential evolution optimization algorithm is employed to seek the solution with minimal velocity increment. The numerical examples indicate that a GEO proximity scenario can be stably and effectively designed by the presented method. Moreover, in the scenarios without a collocated satellite, with a static collocated satellite, and with dynamic collocated satellites, the optimized proximity scenarios remain passively safe. If any impulse in the scenario ceases, the resulting free drift trajectory would diverge from the target and the collocated satellites, maintaining the safety index and satisfying the given threshold.

Dynamics of Robotic GEostationary orbit Restorer system during deorbiting

With the development of human space activities, the number of spacecraft in geostationary orbit (GEO) has increased dramatically. According to the European Space Agency (ESA), by the end of 2008, there were 1186 objects in GEO of which only 32% were controlled operational satellites [1]. In the GEO, there are also many malfunctioning or abandoned spacecraft and lots of space debris that need to be deorbited [2] orbiting alongside functioning spacecraft. It has become necessary to monitor and deorbit these uncontrolled spacecraft and space debris to afford a safe environment for operational spacecraft so that collisions can be avoided. To do this, several alternatives have been proposed by scholars and aerospace research institutions all over the world. Among the suggestions are the RObotic GEostationary orbit Restorer (ROGER) for orbital monitoring and deorbiting [3, 4], an ion beam shepherd for contactless space debris removal [5], electrodynamic tether deorbiting [6-8], deorbiting using solar radiation force [9-11], and space robots. [12, 13]

Accuracy of Two-Line-Element Data forGeostationary and High-Eccentricity Orbits

Accuracy of Two-Line-Element Data forGeostationary and High-Eccentricity Orbits

Correlation and orbit determination of space objects based on sparse optical data

While building up a catalog of Earth orbiting objects, if the available optical observations are sparse, not deliberate follow ups of specific objects, no orbit determination is possible without previous correlation of observations obtained at different times. This correlation step is the most computationally intensive, and becomes more and more difficult as the number of objects to be discovered increases. In this paper we tested two different algorithms (and the related prototype software) recently developed to solve the correlation problem for objects in geostationary orbit (GEO), including the accurate orbit determination by full least squares solutions with all six orbital elements. Because of the presence in the GEO region of a significant subpopulation of high area to mass objects, strongly affected by non-gravitational perturbations, it was actually necessary to solve also for dynamical parameters describing these effects, that is to fit between 6 and 8 free parameters for each orbit. The validation was based upon a set of real data, acquired from the ESA Space Debris Telescope (ESASDT) at the Teide observatory (Canary Islands). We proved that it is possible to assemble a set of sparse observations into a set of objects with orbits, starting from a sparse time distribution of observations, which would be compatible with a survey capable of covering the region of interest in the sky just once per night. This could result in a significant reduction of the requirements for a future telescope network, with respect to what would have been required with the previously known algorithm for correlation and orbit determination.

Feasibility of performing space surveillance tasks with a proposed space-based optical architecture

Under ESA contract an industrial consortium including Aboa Space Research Oy (ASRO), the Astronomical Institute of the University of Bern (AIUB), and the Dutch National Aerospace Laboratory (NLR), proposed the observation concept, developed a suitable sensor architecture, and assessed the performance of a space-based optical (SBO) telescope in 2005. The goal of the SBO study was to analyse how the existing knowledge gap in the space debris population in the millimetre and centimetre regime may be closed by means of a passive optical instrument. The SBO instrument was requested to provide statistical information on the space debris population in terms of number of objects and size distribution. The SBO instrument was considered to be a cost-efficient with 20 cm aperture and 6° field-of-view and having flexible integration requirements. It should be possible to integrate the SBO instrument easily as a secondary payload on satellites launched into low-Earth orbits (LEO), or into geostationary orbit (GEO). Thus the selected mission concept only allowed for fix-mounted telescopes, and the pointing direction could be requested freely. Since 2007 ESA focuses space surveillance and tracking activities in the Space Situational Awareness (SSA) preparatory program. Ground-based radars and optical telescopes are studied for the build-up and maintenance of a catalogue of objects. In this paper we analyse how the proposed SBO architecture could contribute to the space surveillance tasks survey and tracking. We assume that the SBO instrumentation is placed into a circular sun-synchronous orbit at 800 km altitude. We discuss the observation conditions of objects at higher altitude, and select an orbit close to the terminator plane. A pointing of the sensor orthogonal to the orbital plane with optimal elevation slightly in positive direction (0° and +5°) is found optimal for accessing the entire GEO regime within one day, implying a very good coverage of controlled objects in GEO, too. Simulations using ESA’s Program for Radar and Optical Observation Forecasting (PROOF) in the version 2005 and a GEO reference population extracted from DISCOS revealed that the proposed pointing scenario provides low phase angles together with low angular velocities of the objects crossing the field-of-view. Radiometric simulations show that the optimal exposure time is 1–2 s, and that spherical objects in GEO with a diameter of below 1 m can be detected. The GEO population can be covered under proper illumination nearly completely, but seasonal drops of the coverage are possible. Subsequent observations of objects are on average at least every 1.5 days, not exceeding 3 days at maximum. A single observation arc spans 3° to 5° on average. Using a simulation environment that connects PROOF to AIUB’s program system CelMech we verify the consistency of the initial orbit determination for five selected test objects on subsequent days as a function of realistic astrometric noise levels. The initial orbit determination is possible. We define requirements for a correlator process essential for catalogue build-up and maintenance. Each single observation should provide an astrometric accuracy of at least 1”–1.5” so that the initially determined orbits are consistent within a few hundred kilometres for the semi-major axis, 0.01 for the eccentricity, and 0.1° for the inclination.

Status of CNES optical observations of space debris in geostationary orbit

On-ground optical systems using a telescope and a CCD camera offer an effective solution to the problem of observing objects in geostationary orbit. CNES has been studying and developing such systems for several years with two main objectives: firstly to develop systems able to detect debris in the vicinity of the geostationary orbit for statistical evaluation of the population and secondly to develop a tool to determine the orbits accurately: these objectives are currently met using two different systems called TAROT and ROSACE. This paper presents the main characteristics of both systems, the principle of their image processing software, their development status and the main results obtained. Finally, perspectives for further developments and coupling of the two systems are presented.