3.4 Trajectory Design
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3.4.6 Analysis of Launch Window
When the launch window is determined for lunar lander, there are factors to be
considered including illumination and telecommunication condition on landing site,
time on circumlunar orbit, flight time of LTO and constraints of launch trajectory.
When the solar elevation is greater than 10°, usually the optical imaging sensor
would obtain fine pictures. So the solar elevation on landing site was designed to
be greater than 15° when the CE-3 lunar lander was landed. The telecommunication
access of powered descent process should be available for Chinese domestic ground
station to monitor powered descent.
The telecommunication access with satisfying requirements of illumination condition was analyzed between 2012 and 2013 for the CE-3 lunar lander. There were
20 telecommunication accesses that satisfied requirements of both illumination and
telecommunication condition in Jul. 2012 to Dec. 2013, while the duration of each
access was about 3–4 days. The total time of LTO and circumlunar orbit was about
12–15 days. Then the launch time was determined. The argument of perigee of the
launch trajectory was determined by the launch time. The final launch window was
determined by constraints of argument of perigee of the launch trajectory.
On above analysis, the launch windows satisfying all requirements and constraints
of the CE-3 lunar lander in 2013 were in May, June, July, August and December.
3.5 System Components and Specifications
3.5.1 System Components
The components of lunar lander included subsystems such as structure and mechanism, landing cushion, GNC, propulsion, thermal control, Telemetry, Tracking and
Command (TT&C), directional antenna, power supply, general circuits, On Board
Data Handling (OBDH), payloads, engineering parameters measure and etc. The
basic function of subsystems of the CE-3 lunar lander is listed as following.
(1) Structure and mechanism subsystem was made up of structure and mechanisms. There were main bearing structure and auxiliary structure in structure,
whose function was: providing installation surface and room for instruments
of the lunar probe; satisfying requirements of installing accuracy for instruments; assuring the integrity of the structure during all phases including AIT,
launch, soft landing and operation on lunar surface; enduring load condition during assembling, parking, suspending, transporting, integration, test,
launch, flight, landing and operation on lunar surface. There were mechanisms such as solar panel pivoting mechanism, lunar rover connection, release
and deployment mechanism, camera pointing mechanism, cover mechanisms
79
3.4.6 Analysis of Launch Window
When the launch window is determined for lunar lander, there are factors to be
considered including illumination and telecommunication condition on landing site,
time on circumlunar orbit, flight time of LTO and constraints of launch trajectory.
When the solar elevation is greater than 10°, usually the optical imaging sensor
would obtain fine pictures. So the solar elevation on landing site was designed to
be greater than 15° when the CE-3 lunar lander was landed. The telecommunication
access of powered descent process should be available for Chinese domestic ground
station to monitor powered descent.
The telecommunication access with satisfying requirements of illumination condition was analyzed between 2012 and 2013 for the CE-3 lunar lander. There were
20 telecommunication accesses that satisfied requirements of both illumination and
telecommunication condition in Jul. 2012 to Dec. 2013, while the duration of each
access was about 3–4 days. The total time of LTO and circumlunar orbit was about
12–15 days. Then the launch time was determined. The argument of perigee of the
launch trajectory was determined by the launch time. The final launch window was
determined by constraints of argument of perigee of the launch trajectory.
On above analysis, the launch windows satisfying all requirements and constraints
of the CE-3 lunar lander in 2013 were in May, June, July, August and December.
3.5 System Components and Specifications
3.5.1 System Components
The components of lunar lander included subsystems such as structure and mechanism, landing cushion, GNC, propulsion, thermal control, Telemetry, Tracking and
Command (TT&C), directional antenna, power supply, general circuits, On Board
Data Handling (OBDH), payloads, engineering parameters measure and etc. The
basic function of subsystems of the CE-3 lunar lander is listed as following.
(1) Structure and mechanism subsystem was made up of structure and mechanisms. There were main bearing structure and auxiliary structure in structure,
whose function was: providing installation surface and room for instruments
of the lunar probe; satisfying requirements of installing accuracy for instruments; assuring the integrity of the structure during all phases including AIT,
launch, soft landing and operation on lunar surface; enduring load condition during assembling, parking, suspending, transporting, integration, test,
launch, flight, landing and operation on lunar surface. There were mechanisms such as solar panel pivoting mechanism, lunar rover connection, release
and deployment mechanism, camera pointing mechanism, cover mechanisms