SORU: aşağıdaki parçaya göre cevaplayınız
We see from the passage that the main problem of landing a probe on the moon to test for ice in shadowed areas is ----.
In an attempt to settle the question of whether ice
exists on the moon, NASA plans to launch the Lunar
Reconnaissance Orbiter (LRO) in 2008. Travelling in
a polar orbit only 50 kilometres above the moon's
surface, the probe will focus a high-resolution
neutron sensor on the suspected ice deposits to
determine their precise locations. But because the
ice is probably buried and mixed with lunar dirt,
NASA will also need to land a probe to dig up and
analyze soil samples. This mission, scheduled for
2011, is a challenging one because instruments
operating in shadowed areas cannot use solar
power. The craft could land at a sunlit site and send
a battery-powered vehicle into a dark crater, but the
batteries would quickly die. A radioisotope thermal
generator could provide electricity using heat from
plutonium decay, but NASA is leaning against this
option because it is expensive and controversial.
Another idea under consideration is sending a probe
that could hop from place to place on the lunar
surface by restarting its landing rockets, lifting the
craft to 100 metres above its original landing site and
moving it to another spot in the crater basin to hunt
for ice. Investigating more than one site is crucial
because the ice may be unevenly distributed. Yet
another alternative would be to fire groundpenetrating
instruments at several places in the
shadowed basin, either from a lander at the crater's
rim or from an orbiting craft.