Topic
Supersynchronous orbit
About: Supersynchronous orbit is a research topic. Over the lifetime, 2 publications have been published within this topic receiving 19 citations.
Papers
TL;DR: In this paper, the authors derived an analytic expression for the changes in the eccentricity and semimajor axis of a general elliptic orbit, perturbed by a constant low-thrust acceleration applied along the e −ed inertial direction normal to the orbit major axis.
Abstract: The optimal thrust pitch angle variation that results in the maximum change in the eccentricity in general elliptic orbit using continuous, constant, low-thrust acceleration while keeping the orbit energy unchanged after a full thrust cycle is determined by direct use of the theory of maxima and through numerical quadrature and search techniques. The analysis takes into account the presence of a shadow arc arbitrarily positioned along the elliptic orbit, where thrust is cut off. Unlike the well-known nonoptimal scheme that uses a thrust orientation perpendicular to the line of apsides at all times, the present optimal scheme allows for the maximum change in eccentricity for a more efe cient orbit circularization. Approximate but highly accurate analytic expressions for the changes in the eccentricity and semimajor axis of a general elliptic orbit, perturbed by a constant low-thrust acceleration applied along the e xed inertial direction normal to the orbit major axis, are also derived for general use and rapid calculations. HE problem of the maximization of the change in the eccen- tricityofa generalelliptic orbitusingcontinuousconstantlow- thrust acceleration while constraining the semimajor axis a to stay constant after one full cycle of thrust is analyzed, by also taking into account the presence of the Earth shadow arc where the thrust is turned off. Elliptic orbit circularization with electric thrusters is presently performed by geostationary communications spacecraft that are initially released into highly elliptic supersynchronous or- bits, subsequently circularized by also maintaining orbital energy constant. The optimization method is similar to the one used in Refs. 1- 3, which was also applied in Ref. 4 under the same assumption of the initially circular orbit model. In particular, in Refs. 2 and 3, the problem of transferring a spacecraft between two inclined circular orbits, of different size and inclination, in minimum time, using discontinuous low-thrust acceleration is considered. The two-body thrust-perturbed orbit is, thus, constrained to remain circular dur- ing the transfer, and the optimal control law for the thrust direction derived for the fast timescale problem of maximizing the inclina- tion change for a given change in the semimajor axis is used in an averaging procedure to solve the overall slow timescale trans- fer problem. The present paper tackles the fast timescale planar problem in the more general elliptic case, by deriving the optimal thrust pitch proe le that maximizes the change in eccentricity with- out changing semimajor axis and by also extending the analysis to the dual problem of maximizing the orbit semimajor axis while keeping the eccentricity e unchanged after one cycle of intermittent thrust. The change in eccentricity over a single orbit can then be used in conjunction with an inclination change to produce averaged rates of change in the eccentricity and inclination to solve the over- all slow timescale minimum-time transfer problem of circularizing and rotating an initial elliptic orbit without changing its orbital en- ergy. The theory of maxima is, thus, employed in the present planar problem, and the value of a certain constant Lagrange multiplier is
5 citations
TL;DR: In this paper, the authors examined the long-term stability of supersynchronous disposal orbits and the geopotential stable points of the geosynchronous ring and found that the use of the supersynchronous orbits for disposal purposes is economical and effective in significantly reducing the collision hazard.
Abstract: A number of national and international organizations have adopted a policy of removing spacecraft at the end of life from the geosynchronous ring. However, a resolution of several technical issues still remains before an international policy can be developed and implemented by all users of geosynchronous orbits. The present study reviews the cataloged population of objects in the geosynchronous ring. The probability of collision is computed as a function of range and orbital inclination of an object. Long-term stability of supersynchron ous disposal orbits and of the geopotential stable points is examined. Several disposal options are considered. The results of the study show that the use of the supersynchronous orbits for disposal purposes is economical and effective in significantly reducing the collision hazard. The use of the geopotential stable points for disposal of spacecraft at the end of life, on the other hand, was found to be impractical. I. Introduction B ECAUSE of the uniqueness and usefulness of the geosynchronous equatorial orbit (GEO), the population of objects in this orbit has increased continuously. Reference 1 shows, for example, that at the beginning of 1988, there were 286 cataloged satellites residing in this orbit, not including spent upper stages. Of these, 110 to 130 operating satellites were on station along with 150 that are nonfunctional or abandoned. ,. Reference 2, on the other hand, shows that of the approximately 453 cataloged objects traversing GEO altitudes, only about 150 are geostationary. The others are either geosynchronous or in highly elliptical ("Molniya") semisynchronous orbits. There are also a number of military spacecraft, the orbjts of which are not generally availably in published form. To reduce the collision hazard within GEO, approximately 30 to 35 satellites have been removed from GEO at the end of life. Several strategies are available for disposing of GEO satellites, suqh as moving them to stable longitudes or raising them to orbits above geostationary altitude. The benefits of removing old spacecraft from GEO are a) the freeing of desirable longitudinal positions for repl^cement spacecraft and b) the reduction of collision damage potential, which can become high for collocated satellites.3 The primary issues involved are a) the protection of GEO as a unique natural resource and b) operational considerations such as cost effectiveness of the maneuver, risks of explosion, structural breakup, or other malfurigtions in carrying out the maneuver and national and international policy considerations. Other issues include the potential impact on future traffic to GEO and the perturbative effects on disppsal orbits (e.g., solar radiation and the sun/moon gravitational perturbations). In other words, abandoned rocket stages or satellites should not be a hazard to future missions, and their orbits should not intersect GEO over long periods of time.
Performance Metrics
| Year | Papers |
|---|---|
| 2003 | 1 |
| 1990 | 1 |