76
3 System Design of Lunar Lander
3.4.2 Constraints of Trajectory Design
Major constraints of trajectory design for lunar lander by mission requirements and
engineering system constraints were including [5]:
(1) Requirement for launch window: there should be more and wider launch
windows for implementation feasibility.
(2) Launch site: there were launch site location, launch azimuth and etc. in
constraints of launch trajectory design.
(3) Launch vehicle: there were constraints like launch mass, accuracy of launch
trajectory, limitation of launch trajectory and etc.
(4) Landing site: range of longitude and latitude of landing site on lunar surface.
(5) Ground station: location and distribution of the ground stations.
(6) Illumination condition: illumination condition of all procedures in mission
profile.
(7) Accuracy of orbit control: the error of Delta V control for orbit maneuvers.
(8) Target orbit before powered descent: altitude, inclination, argument of
perilune and etc.
(9) Requirements of telecommunication access: requirements for telecommunication access time especially for key events.
(10) Accuracy of orbit determination and prediction: Accuracy of measurement
and prediction for the trajectory position and velocity of all procedures in
mission profile.
All those above factors should be considered to define optimum solution when the
trajectory is designed.
3.4.3 Determination of Landing Window
The determination of landing window was up to requirements of solar elevation and
telecommunication condition when lunar lander was landed on lunar surface. For
example, it ws analyzed for the Sinus Iridum (31.5°W, 44.1°N) in lunar day in Aug.
2013 for the CE-3 lunar lander. The variation of solar elevation is shown in Fig. 3.22
in one lunar daytime (14 Earth days) assuming that the local plane was horizontal.
The solar elevation and telecommunication access for Chinese domestic ground
station is shown in Fig. 3.23. The landing window selection should satisfying requirements for both illumination and telecommunication access by analysis of illumination
and telecommunication condition.
3 System Design of Lunar Lander
3.4.2 Constraints of Trajectory Design
Major constraints of trajectory design for lunar lander by mission requirements and
engineering system constraints were including [5]:
(1) Requirement for launch window: there should be more and wider launch
windows for implementation feasibility.
(2) Launch site: there were launch site location, launch azimuth and etc. in
constraints of launch trajectory design.
(3) Launch vehicle: there were constraints like launch mass, accuracy of launch
trajectory, limitation of launch trajectory and etc.
(4) Landing site: range of longitude and latitude of landing site on lunar surface.
(5) Ground station: location and distribution of the ground stations.
(6) Illumination condition: illumination condition of all procedures in mission
profile.
(7) Accuracy of orbit control: the error of Delta V control for orbit maneuvers.
(8) Target orbit before powered descent: altitude, inclination, argument of
perilune and etc.
(9) Requirements of telecommunication access: requirements for telecommunication access time especially for key events.
(10) Accuracy of orbit determination and prediction: Accuracy of measurement
and prediction for the trajectory position and velocity of all procedures in
mission profile.
All those above factors should be considered to define optimum solution when the
trajectory is designed.
3.4.3 Determination of Landing Window
The determination of landing window was up to requirements of solar elevation and
telecommunication condition when lunar lander was landed on lunar surface. For
example, it ws analyzed for the Sinus Iridum (31.5°W, 44.1°N) in lunar day in Aug.
2013 for the CE-3 lunar lander. The variation of solar elevation is shown in Fig. 3.22
in one lunar daytime (14 Earth days) assuming that the local plane was horizontal.
The solar elevation and telecommunication access for Chinese domestic ground
station is shown in Fig. 3.23. The landing window selection should satisfying requirements for both illumination and telecommunication access by analysis of illumination
and telecommunication condition.