Research On Orbit Design Of “Longjiang-2” Microsatellite

To observe and explore the Dark Age of the universe,Harbin Institute of Technology and National Space Science Center proposed a ultralong wave astronomical observation microsatellite program(“Longjiang-2”)in circumlunar orbit,which makes full use of the Long March-4C remaining carrying capacity 100 kg in the launch mission of Queqiao,a relay satellite of Chang'e-4.The project obtained approval of China National Space Administration and a strong support of Heilongjiang Province to carry out a micro-satellite based low-cost deep space exploration.Orbit design and optimization become the technical challenge during the mission of entering the circumlunar orbit independently with limited resource of fuel,telemetry-track-and-command(TT&C)and on-board computing.The optimal operating time of Longjiang-2 microsatellite is affected by the relative positions of the sun,the earth and the moon.With limited mass of fuel consumption,the design of lunar transfer orbit with the consideration of the operational conditions of the circumlunar orbit,is an engineering challenge.To solve this problem,a mathematical model of optimal operating time period of Longjiang-2 microsatellite and conditions of lunar relay communication was constructed.On base of the proposed model,an optimal design model for lunar transfer orbit under the fuel consumption constraint was established.An orbit hierarchical optimization design method,which combines differential correction and genetic algorithm,is proposed to realize a joint optimization of lunar transfer orbit and circumlunar orbit,and solve the problem of the design of lunar transfer orbit and circumlunar orbit of Longjiang-2.In order to realize autonomous high-precision orbit calculation of the Longjiang-2microsatellite,this paper focuses on the orbit fitting under the long-term high-precision constraint based on the orbit prediction strategy of “Extrapolation-Fitting-UploadingCalculation” method.First,based on the idea of separating the main term of the twobody motion and the minor term of the perturbation,a model perturbation residual fitting method using Chebyshev polynomials is proposed.This method makes ingenious use of the tiny model fitting residual and improves the orbital fitting accuracy by an order of magnitude under the same fitting duration.Besides,a long-term orbit piecewise fitting strategy is proposed,which greatly increases the effective time scale of orbit fitting.Finally,by uploading the fitted model,high-precision autonomous orbit calculation is realized,under conditions of limited TT&C and on-board computing resources.Longjiang-2 is scheduled to crash into the moon.This paper studies the design of reliable lunar collision orbits considering the risk of failure.A low-energy-consumption orbit design method based on pulse control at apogee is proposed,which uses natural perturbation.Considering the long-term orbit decay rules,this method can ensure a reliable moon collision of Longjiang-2.Furthermore,the controllable and reachable range of the lunar collision area with limited fuel are analyzed in this paper.On this basis,a precise lunar collision orbit design method is proposed,applying the pulse and finite thrust strategy,considering the geometric constraints of the perigee.The problem of precise lunar collision orbit design is solved.Deep space exploration from the lunar orbit is an important foothold of the lunar base construction plan of various countries,and it is also one of the mission plans of Longjiang-2 microsatellite.This paper first constructed a transfer orbit splicing model for planetary exploration from the moon,and further proposed a step-by-step design method for selenocentric escape and geocentric escape orbits based on the splicing model.For the design of selenocentric escape orbit,the problem of the selenocentric orbit being separated from the initial orbit is avoided by solving the two-point boundary value problem.For the design of geocentric escape orbit,a method to determine the orbit parameters which starts from a certain point to a given residual velocity has been developed.This can be applied to both of direct escape and flyby escape of the earth.The correctness and effectiveness of the proposed method are verified by the orbit design of different target planets.