As the
day progressed, the euphoria caused by this fantastic achievement
started to wane bit by bit, as bad news kept trickling. I had
mentioned in the previous article, that two harpoons, that were
supposed to be fired to anchor Philae on ground because 67P comet is
a small mass moving in space with extremely low gravity (
1/100,000th that of Earth), did not get fired at all. In fact this
washing machine sized probe weighs just unbelievable 1 gram on comet
because of its low gravity. The harpoons were supposed to hold the
probe against the surface of the comet and since they did not fire,
Philae is sitting their just because of the gravitational force of
its weight of 1 gram. Scientists recognize this as highly unstable
and dangerous situation.
News
for more trouble started coming in. Because the two harpoons failed
to get fired, Philae just could not be anchored to the surface of
comet at first touch down at
15.33 Hrs and bounced off the surface of the comet like a tennis ball
and drifted through
the void for almost two hours before touching down again at 17:33
Hrs. According to some reports, this bounce could have been as high
as a mile or 1,6 Km. Even at this time it did not settle down on
surface and bounced off again, though with a smaller bounce. After
another 7 minutes it finally settled on the surface at 17:41 Hrs. in
a shallow crater on the comet's 2 mile wide body.
With
the stability problem being solved temporarily, a new problem cropped
up. Philae has a primary battery and secondary solar powered
batteries. Scientists detected that they were hardly getting any
solar power at all as during the 12 hour day, the comet received
illumination for just 1.5 hours. The reason for this problem was
found out to be the place where Philae was resting after the second
bounce. It was sitting next to a cliff that was about few meters away
and it was in the shadow of the cliff permanently. This meant that
the shadow was blocking the sunlight from reaching to solar points.
This
has brought about a new dilemma for the mission control scientists.
With the primary battery slowly running out, they need to decide the
use for which this power is to be used. There are 4 scientific
instruments that can reveal tomography of the comet and data showing
whether the matter it is made of is magnetized? The primary battery
can run these experiments for a few days without the help of solar
batteries. On the other hand, some acrobatic maneuvers can be tried
to get the solar panels out of the shadows so they can keep Philae
going for a few more months. However if this fails, the mission
control will neither receive any data from the experiment nor would
be able to move the craft out of shadow. This would mean that
Philae's useful lifetime may now be much shorter and it would just
keep sitting on surfaced of the planet in a mode of hibernation for
the coming months. The comet is on a 6 ¼ year elliptical orbit
around the sun, and at the moment it is getting closer to the sun.
There is a chance that Philae might wake up again if its solar
panels catch more light. But that is just a chance.
It
appears that mision control scientists have decided to collect as
much data as possible while its primary battery still has energy
before trying any risky maneuvers. Philae's scientific instruments
have already begun gathering reams of data to send back to Earth,
including the first pictures taken from the surface of a comet. The
first photos reveal the comet's rocky terrain, include one that
showed one of the lander's three feet in the corner of the frame.
Another
experiment was carried out in which a penetrator was hammered in
comet's surface and related temperature rise was measured with
sensors. This could give important clues regarding composition of the
ground.
Because
Philae is sitting their just with its own weight of 1 gram,
scientists are figuring out whether an important planned experiment
can be tried out This experiment involves drilling into the comet to
extract some of the material buried beneath the surface. But drilling
without the craft not being properly anchored can be dangerous as it
can tilt or even lift off the lander. This experiment is important
because scientists want to analyze the material of the comet as it
has remained almost unchanged for 4.5 billion years, making it
something of a cosmic time capsule. However as per latest news,
mission control has decided to go ahead with drilling as the
batteries may not last beyond Friday ( 14-November 2014).
Around
7PM (IST) on 14th November 2014, Philae started drilling
on the surface of the comet. Around midnight, another attempt was
made to rotate Philae to see whether it could get more sunlight to
charge its batteries. Finally around 7 AM (IST) on 15th
November, Philae sent the last round of data including analysis of
the drilling samples, before its batteries went dead and it went into
hibernation. It would revive only when sunlight falls on the solar
chargers. Whether the data sent by Philae reveals at least some new
information about the materials, the comet is composd off, we should
know in a day or 2.
After
Philae has gone dead, scientists can still receive data from the
mother ship Rosetta, which carries on board 11 instruments to analyze
the comet, over the coming months. Let us wait and watch.
15th
November 2014
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