64
3 System Design of Lunar Lander
Table 3.1 Equivalent 1 MeV electron damage dose for the single junction gallium arsenide solar
cell
The cover
Lunar lander
Density/(g/cm 2 )
Depth/mm
Open circuit
voltage/V
Max. power
consumption/W
Short circuit
current/A
0.0308
0.12
5.14 × 10 13
3.68 × 10 13
1.69 × 10 13
For the worse case, there might be a super solar flare like the event in Oct. 1989
in the life time of lunar lander. The equivalent 1 MeV electron damage dose for the
single junction gallium arsenide solar cell is listed in Table 3.1.
3) Single Event Effects (SEE)
The radiation source of SEE is high energy proton of the Earth radiation belt, high
energy heavy ion and proton of the GCR and SCR.
It is up to not only the value of Linear Energy Transfer (LET), but also the
capability of SEE tolerance, whether there is SEE or not for the electronic parts and
components. There might be frequent SEE if the threshold value of LET is low and
event cross area is big which means very sensitive to SEE, even there is no solar flare.
Therefore, methods including control of electronic parts and components, anti-SEE
design in system level and etc. must be adopted to avoid influence of SEE.
4) Surface Charge and Discharge Effects (SCDE)
The surface charge and discharge on lunar lander might be caused by hot ion in
the Earth’s magnetosphere and solar wind. The surface charge and discharge effect
caused by hot ion is only encountered when lunar lander is through hot ion region
in the Earth’s magnetosphere (20,000–40,000 km) during LTO. It is obvious when
there is sub storm of the Earth magnetic storm. So the surface charge potential of
lunar lander should be analyzed, while the electrical resistivity of surface material and
ground connection should be controlled strictly to lower the surface electric potential
of lunar lander in order to rule out the effect of surface charge and discharge effect.
The solar wind particles encountered may cause surface charge effect when the
electronic devices of lunar lander work on lunar surface. Because the surface charge
and discharge effect in life time of lunar lander is weak, the surface electric potential
could be lowered by strict control of the electrical resistivity of surface material and
ground connection distance to rule out the effect of surface charge and discharge
effect.
5. Internal Charging Effects
The internal charging effect is due to strong geomagnetic activity. There would be
charging within the spacecraft dielectric materials when the spacecraft is radiated
continuously by long term high energy and high-flux electrons in Earth’s magnetosphere. Because it is only 5 h for lunar lander to get through the Earth’s magnetopause
(about 65,000 km height), there is hardly no strong geomagnetic activity encountered
by lunar lander. After then, lunar lander would no encounter the environment of high
3 System Design of Lunar Lander
Table 3.1 Equivalent 1 MeV electron damage dose for the single junction gallium arsenide solar
cell
The cover
Lunar lander
Density/(g/cm 2 )
Depth/mm
Open circuit
voltage/V
Max. power
consumption/W
Short circuit
current/A
0.0308
0.12
5.14 × 10 13
3.68 × 10 13
1.69 × 10 13
For the worse case, there might be a super solar flare like the event in Oct. 1989
in the life time of lunar lander. The equivalent 1 MeV electron damage dose for the
single junction gallium arsenide solar cell is listed in Table 3.1.
3) Single Event Effects (SEE)
The radiation source of SEE is high energy proton of the Earth radiation belt, high
energy heavy ion and proton of the GCR and SCR.
It is up to not only the value of Linear Energy Transfer (LET), but also the
capability of SEE tolerance, whether there is SEE or not for the electronic parts and
components. There might be frequent SEE if the threshold value of LET is low and
event cross area is big which means very sensitive to SEE, even there is no solar flare.
Therefore, methods including control of electronic parts and components, anti-SEE
design in system level and etc. must be adopted to avoid influence of SEE.
4) Surface Charge and Discharge Effects (SCDE)
The surface charge and discharge on lunar lander might be caused by hot ion in
the Earth’s magnetosphere and solar wind. The surface charge and discharge effect
caused by hot ion is only encountered when lunar lander is through hot ion region
in the Earth’s magnetosphere (20,000–40,000 km) during LTO. It is obvious when
there is sub storm of the Earth magnetic storm. So the surface charge potential of
lunar lander should be analyzed, while the electrical resistivity of surface material and
ground connection should be controlled strictly to lower the surface electric potential
of lunar lander in order to rule out the effect of surface charge and discharge effect.
The solar wind particles encountered may cause surface charge effect when the
electronic devices of lunar lander work on lunar surface. Because the surface charge
and discharge effect in life time of lunar lander is weak, the surface electric potential
could be lowered by strict control of the electrical resistivity of surface material and
ground connection distance to rule out the effect of surface charge and discharge
effect.
5. Internal Charging Effects
The internal charging effect is due to strong geomagnetic activity. There would be
charging within the spacecraft dielectric materials when the spacecraft is radiated
continuously by long term high energy and high-flux electrons in Earth’s magnetosphere. Because it is only 5 h for lunar lander to get through the Earth’s magnetopause
(about 65,000 km height), there is hardly no strong geomagnetic activity encountered
by lunar lander. After then, lunar lander would no encounter the environment of high