Parking orbit

Abstract: The International Sun-Earth Explorer (ISEE) scientific satellite to be stationed in 1978 in the vicinity of the sun-earth interior libration point to continuously monitor the space between the sun and the earth, including the distant geomagnetic tail is described. Orbit selection considerations for the ISEE-C are discussed along with stationkeeping requirements and fuel-optimal trajectories. Due to the alignment of the interior libration point with the sun as viewed from the earth, it will be necessary to place the satellite into a 'halo orbit' around the libration point, in order to eliminate solar interference with down-link telemetry. Parametric data for transfer trajectories between an earth parking orbit (altitude about 185 km) and a libration-point orbit are presented. It is shown that the insertion magnitude required for placing a satellite into an acceptable halo orbit is rather modest.

Abstract: Minimum-fuel, planar trajectories from a circular low Earth parking orbit to a circular low lunar parking orbit with a fixed thrust-coast-thrust engine sequence are computed for a low-thrust spacecraft. The problem is studied in the context of the classical restricted three-body problem. Since a low-thrust trajectory is a long-duration transfer with slowly developing spirals about Earth and the moon, the minimum-fuel Earth-moon trajectory is obtained by formulating and successively solving a hierarchy of three subproblems. This three-stage approach presents a systematic and effective method for solving the complex and numerically sensitive minimum-fuel, lowthrust, trajectory problem. The first subproblem is to obtain several optimal continuous-thrust Earth-escape and moon-capture trajectories. The second subproblem is to compute a suboptimal, all-coasting, translunar trajectory between boundary conditions provided by the first subproblem. Finally, the complete minimum-fuel trajectory problem is solved using a "hybrid" direct/indirect method. The hybrid method utilizes the costate time histories to parameterize the thrust steering history. Numerical results are presented for the optimal Earth-moon trajectories.

Abstract: Global optimization methods have been increasingly under consideration for preliminary interplanetary mission design. One promising global method, differential evolution, has been identified as being particularly well suited to high-thrust trajectory optimization. Differential evolution is a stochastic direct search optimization method which uses parameter vectors that interact in a manner motivated by the evolution of living species. To improve the performance of differential evolution for this application, the effect of the tuning parameters is investigated over a diverse group of trajectory optimization problems. The quality of solutions obtained with differential evolution is found to be very sensitive to the selection of the routine’s tuning parameters. A set of tuning parameter values is found that results in the rapid global optimization of an array of typical ballistic interplanetary missions. The fine-tuned differential evolution routine is implemented in a new tool, the mission-direct trajectory optimization program, and the effectiveness of this tool is demonstrated by the rapid solution of interplanetary trajectory optimization problems that involve complex features such as multiple gravity assists and parking orbit considerations.

Abstract: The FORMOSA Satellite Series No. 3/Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC) spacecraft constellation consisting of six low-earth-orbiting satellites is the world's first operational Global Positioning System (GPS) radio occultation mission. The mission has been jointly developed by the National Space Organization of Taiwan and the University Corporation for Atmospheric Research of the U.S. in collaboration with the Jet Propulsion Laboratory, NASA, and the Naval Research Laboratory for three onboard payloads, including a GPS Occultation Receiver, a triband beacon, and a tiny ionospheric photometer. The FORMOSAT-3/COSMIC mission was successfully launched from Vandenberg into the same orbit plane of the designated 516-km circular parking orbit altitude on April 15, 2006. After the six satellites completed the in-orbit checkout activities, the mission was started immediately at the parking orbit for in-orbit checkout, calibration, and experiment of three onboard payloads. Individual spacecraft thrust burns for orbit raising were performed to begin the constellation deployment of the satellites into six separate orbit planes. All six FORMOSAT-3/COSMIC satellites are maintained in a good state of health except spacecraft flight model no. 2, which has had power shortages. Five out of the six satellites had reached their final mission orbits of 800 km as of November 2007. This paper provides an overview of the constellation spacecraft design, constellation mission operations, constellation deployment timeline evolution, associated spacecraft mass property and moment of inertia results, orbit-raising challenges, and lessons learned during the orbit-raising operations.