IF NASA鈥檚 latest Mars probe is declared a complete loss, as seemed inevitable
as 快猫短视频 went to press, the space agency is in serious trouble.
Not only are its next two Martian landers nearly identical to the stricken
craft, but there is also very little chance that engineers will ever discover
what went wrong.
Launched in January, the Mars Polar Lander ended its voyage on 3 December. If
all had gone to plan, it would have landed near the planet鈥檚 south pole to
analyse surface weather and soil. On its approach, it was supposed to turn away
from the Earth, losing radio contact as it did so, then plunge through the
atmosphere and deploy a parachute, eventually touching down with the help of its
thrusters. It would then have unfurled its solar panels and beamed back a
message signalling its arrival.
That message never came. As 快猫短视频 went to press, mission
controllers at the Jet Propulsion Laboratory (JPL) in Pasadena were still
attempting to contact the lander. But hope was fading fast, following the
failure of several attempts using different radio antennas and different
assumptions about what went wrong.
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Even attempts to detect radio signals from the landing zone using the
orbiting Mars Global Surveyor yielded nothing. Two hitch-hiker probes, designed
to detach from the craft and smash into the Martian soil, also remained
silent.
According to JPL spokesman David Seidel, the lander seemed to be in perfect
health until radio contact was lost. 鈥淲e clearly saw the turn begin,鈥� he says.
The probe was roughly on target, which should have placed it within a few
kilometres of its intended landing zone.
And that鈥檚 about all NASA engineers have to go on as they try to work out
what happened next. Even the failure of the hitch-hiker probes doesn鈥檛 tell them
much. The craft were supposed to separate early in the descent, and Sam Thurman,
Mars Polar Lander鈥檚 flight operations manager, believes they almost certainly
parted company as planned. He thinks the failure of the probes and that of the
lander are likely to have been separate events.
The loss of the Polar Lander is particularly worrying because NASA鈥檚 next
missions to Mars, scheduled for launch in 2001 and 2003, use the same basic
design. 鈥淲e made them as identical as possible to save money,鈥� explains Sylvia
Miller, who helped design the craft. 鈥淚n fact, we call it the workhorse
濒补苍诲别谤.鈥�
It is already too late to make radical design changes to the 2001 project. In
any case, there is little chance that re-examining the designs will uncover the
flaw that claimed the lander, as this would simply be repeating work done
following the loss of the Mars Climate Orbiter in September. Engineers corrected
one problem: they found that the lander鈥檚 fuel lines were in danger of freezing
solid and so switched on its heaters early
(快猫短视频, 20 November, p 15).
But everything else looked fine.
NASA officials are now wondering whether to redesign future probes to yield
more information if they fail. One option is to give them small radio beacons to
report the successful completion of each step in the landing sequence, but this
would leave less room for important scientific equipment. 鈥淚 don鈥檛 think that鈥檚
the correct direction,鈥� says David Crisp, project scientist for NASA鈥檚 New
Millennium space science programme.
Other experts want NASA to change its 鈥渇aster, better, cheaper鈥� policy for
space exploration. Following the loss of the $1 billion Mars Observer
probe in 1993, the agency switched to missions costing around $125
million. 鈥淚 wish we could have $300 million projects,鈥� says John Logsdon,
a space policy analyst at George Washington University in Washington DC. 鈥淲e鈥檙e
really trying to skip by and trust in technological luck.鈥�
Luck, unfortunately, seems to have forsaken NASA.