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ビーナスリターン…なんてあんま言わないと思うけど、今年のそれ以降私の様子がおかしい。

@NASA_Dawn:
Question of the day: Why is the final orbit at #Ceres (230 mi) higher than the lowest mapping orbit at Vesta (162 mi)? A few reasons:
@NASA_Dawn:
1. Mission planners don't want me to come in contact with the surface, even decades after the mission ends.
@NASA_Dawn:
2. Because Ceres is larger than Vesta, at the lowest altitude, Ceres will appear as large in the sky as Vesta did in my lowest orbit there
@NASA_Dawn:
3. If I did get as close to Ceres as I did to Vesta, it would take a very long time to map the entire surface
@NASA_Dawn:
4. Hydrazine, the fuel I need to turn, is limited, and it costs more hydrazine to operate me the lower I am.
@NASA_Dawn:
All four of these are contributing factors to why my final orbit will be 230 miles (375 km) from Ceres


ドーンの資料はここ。セレスでは高いとこにいるみたいですぞ！