Orbit Design In Responsive Space Missions

Operationally responsive space is a new application for space systems to progress,which can improve the efficiency to exploit the space and arrive at utilizing space indemand. With the background of responsive space missions, this thesis performs theresearch and discussion on the technologies of orbit design, and investigates anddemonstrates the application feasibilities of several classic responsive orbits.Firstly, the critical requirements and system drivers of responsive space missionswith respect to orbit design are exhibited, and the coverage characteristics of responsiveorbits are analyzed. The variations of ground tracks due to orbit perturbations and orbitinsertion errors are studied, the analytical expression of the maximum ground-track driftis derived, and the orbit maintenance strategy that is suitable for responsive orbits andcan ensure the accuracy over the entire ground track is presented. The coveragecharacteristics of classic responsive orbits are analyzed based on the geometry of theground tracks of the orbits and the ground-target coverage region on a reference sphereand on a map, and the metrics that describe the coverage characteristics andresponsiveness of orbits are obtained, including successive-coverage time, meancoverage persistence time and orbit response time.Secondly, the launch, lighting, and tracking-telemetry-and-command (TTC)constraints of responsive orbits are analyzed. For the launch constraint, the launchwindows and launch delays of fixed launch and mobile launch are investigated, and theinsertion times of direct injection, transfer injection and phasing injection are exhibited.If a satellite is launched into a low-Earth fast access orbit (FAO), the fixed launch anddirect injection should be employed. If satellites are launched into low-Earth repeatcoverage orbits (RCO), the mobile launch and phasing injection should be employed.For the lighting constraint, the reconnaissance windows of targets at various latitudes indifferent seasons are analyzed in the visible-light reconnaissance, and the applicationfeasibilities of the low-Earth FAO and RCO are exhibited. A low-Earth FAO or RCOcan perform a visible-light reconnaissance to any ground target in summer, a low-EarthFAO can perform a visible-light reconnaissance to a low-latitude ground target at anytime in the whole year, and a low-Earth RCO can perform the survey reconnaissanceand television reconnaissance to a low-latitude ground target at any time in the wholeyear. For the TTC constraint, the deployments of stations for launch-TTC and datacollection of the low-Earth FAO and RCO are discussed, and the feasibility of deploying the stations within our country is investigated. The launch-TTC stations forthe low-Earth FAO should be deployed around the launch site evenly, and the datacollection station should be laid at the point that isωe T Sto the west of the launch site.The launch-TTC stations for the low-Earth RCO should be deployed evenly along theeast, north and south frontier within and out of the launch area.Thirdly, the orbit design methods in classic responsive space missions arediscussed, including rapid reconnaissance, rapid successive-coverage reconnaissance,on-orbit surveillance, and satellite constellation complement and reconfiguration. Underthe background of a rapid reconnaissance, the design method of a low-Earth FAO isdiscussed. A constrained observation region of a low-Earth FAO is analyzed, and thecorresponding data collection station deployment and launch constraints are studied. If asatellite is launched into a low-Earth FAO to perform a rapid reconnaissance, more thanone launch site should be built to evade the constrained observation region of the FAO.Under the background of a rapid successive-coverage reconnaissance, the designmethod of low-Earth RCOs is discussed. The construction of a responsivesuccessive-coverage constellation is exhibited, and the rapid launch and deploymentscheme is analyzed. A responsive successive-coverage constellation can be launchedand deployed using three one-rocket-multiple-satellites launches. Under the backgroundof an on-orbit fire surveillance, the design method of low-Earth sun-synchronous orbits(SSO) is discussed. Firstly, the responsiveness of a low-Earth SSO is analyzed, and theorbit response time is derived. Then, a low-Earth sun-synchronous repeat-groundtrackorbit constellation is designed, in which two orbit planes can acquire the upperresponsiveness. Under the background of rapid complement or reconfiguration of asatellite constellation, the feasibility for a responsive orbit satellite to complement orreconfigure an Earth-observation satellite constellation is analyzed. The method torepair the coverage gap of an Earth-observation constellation with a low-Earth RCO orSSO is exhibited.Finally, the nondominated sorting genetic algorithm II (NSGA-II), is used todesign responsive orbits, considering two conflicting metrics of the orbit: thesuccessive-coverage time and the orbit response time. The frame of designing aresponsive orbit with NSGA-II is built and the optimal solution selected from Paretofronts is obtained, which can provide references to the traditional design of responsiveorbits.Along with the development of space technologies and extension of space system applications, the responsive technologies are stepping into practice gradually. Theresearch conclusions of this thesis would be helpful in the development of our country’srelated space missions, theoretically and technically.