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Garry Simburger and some ANITA guys arrive
We covered TIGER and shut down our science
machines in anticipation of an exciting storm, but alas, it was not to
be. We are trying to be careful about taking care of our
equipment since we heard that in the past, the weatherport was even
blown over during a large storm. Dana and I uncovered the
equipment and I started getting TIGER ready to run on its own, without
the SIP. The NSBF SIP is a rather large machine, costing a few
million dollars, that sits underneath the TIGER payload and is
responsible for telemetering all the data that the science payload
generates. All of our commands run through the SIP and it syncs
the data so that it can be sent via line-of-sight (LOS) while the
instrument is aloft for the first few hours, and when it completes a
full revolution of the continent and is in the vicinity of the NSBF
Telemetry building out at Williams Field. It is also responsible
for sending our data up to a set of old TDRSS satellites that send our
data down to White Sands, NM, on to Palestine, TX (where the National
Scientific Balloon Facility resides) and finally on to us here down on
the Ice. So, needless to say, it is an integral part of the
Long-Duration Balloon project. After having some difficulty
getting our instrument running on its own, Drew Denny and his crew
announced that our SIP would be running by the end of the day.
So, tomorrow is going to be an exciting day as far as getting some
preliminary "whopper" data.
Now whoppers are an interesting phenomenon.
This is not really a scientific term, but they are important for us to
determine that our instrument is running properly when it is still on
earth. Whoppers are caused by energetic particles entering
earth's atmosphere and producing cascades of other particles as they
interact with air molecules and create many other particles on their
way down to the ground. Because of this, these events are rather
messy in the TIGER instrument. By messy, I mean that the
hodoscope, whose purpose is to give us the precise location of a single
particle entering the instrument, is overwhelmed by a blast of many
particles. In other words, many of the approximately 5000 fibers
that make up the hodoscope scintillate due to these particles'
interactions and give us no information about the angle of incidence of
these particles. The scintillators and cherenkov detectors in
TIGER are in turn triggered by this sea of particles and therefore also
can give no information on the charge and energy of the
particles. In order for TIGER to output good data during an
actual flight, a single particle must enter the instrument and remain
totally intact during its entire journey through the instrument.
TIGER's photomultiplier tubes are connected to
electronics that determine how and when a particle can "trigger" the
instrument. We set the thresholds of our detectors so that
a particle that passes through must have a significant enough amount of
energy and charge to allow the electronics to deem it a useful
event. Since we are looking for particles heavier than iron (in
other words, particles that have more than 26 protons in their nuclei)
that have energies a few GeV per nucleon, we set these thresholds
accordingly during the first few hours of the balloon flight. In
order to assure that a particle has remained intact as it passes
through the instrument, we require there to be one distinct set of
fibers in the hodoscope that scintillate brighter than all the others,
and we require that either one of the two scintillators on the top and
on the bottom give a signal that is above our threshold (i.e. S1 or S2
and S3 or S4). TIGER is also equipped with LEDs embedded in all
of the detectors that can simulate a particle passing through the
detector. These LEDs are important because they provide us with a
light source with constant intensity, so we can make sure that our
photomultiplier tubes are detecting light consistently throughout the
flight.
All right, now back to Antarctica. Since
internet security is a very big issue for Raytheon this year, it took a
few days for us to get the required permission for us to set our
network so that people from Washington University may log in to our
science machines. This was finally cleared up today.
Another exciting event: I was able to turn on TIGER's flight CPU
to make sure that it and the hard drive survived the trip down.
Garry Simburger, our group's electronic technician,
and four people from the ANITA project were finally
able to make it down to McMurdo today after being delayed in
Christchurch for several days. For Dana and me, it is nice to
have Garry around as things really start picking up out at Williams
Field. Dana and I came back into town around 4:00 to meet them at
the NSF chalet. Then I spent most of the evening helping the
ANITA crew get their bags from their holding place at the Movement
Control Center to their dorm rooms, and showing them around town.
Tomorrow is going to be a big day. The ANITA
crew will be busy unloading all of their gear and setting up their
electronics and with any luck, TIGER will become fully active, growling
softly out on the Ice.
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