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The
TDRSS test
Well, after a few delays and some quick
work, we were ready
for our
TDRSS test when it came today at 1:00 PM. The folks at NSBF have
to make sure to reserve NASA TDRSS (Telemetry Data Relay Satellte
System) for a certain block of time whenever it needs to be used.
It is particularly difficult down here in Antarctica, mainly because
the satellite system is in an equatorial orbit. For us, that
means that whenever our payload is too close to the South Pole (below
about
85° S Lat.), TDRSS is below the horizon and we are unable to
transmit data to it. By about 1:00, a satellite had finally made
its way around Mount Erebus and we were able to make contact with
it. The satellite was reserved between 1:00 PM and 4:00 PM.
During this time, our GSE (Ground Support Equipment) in Palestine,
Texas was able to receive data
and relay it over a port 7740 (ethernet) connection down here.
However, we were only able to send commands to TIGER during a 44-minute
period during the beginning of the TDRSS window and during a 43-minute
window during the end of our window.
The whole concept is a pretty fascinating
thing to think about. Here I am in a weatherport in a "suburb" of
McMurdo Station, Antarctica. We are sending commands over an
ethernet connection to a microwave link to McMurdo Station, up to a
satellite, and down to a receiver in the United States, and through the
wires to our stateside GSE in Palestine, Texas. Our commands are
telemetered up to TDRSS, which then relays the commands to TIGER, which
is currently only about 30 feet from the computer I'm sitting in front
of. TIGER processes command and transmits its response back up to
the satellite, which then relays it to an array of dishes in White
Sands, New Mexico. The data is then sent to Palestine where it is
sent over the network to our stateside GSE. The GSE then
transmits the data over the network, through the wires and through
another satellite link, to McMurdo Station, where it is received and
sent over a microwave link out to Williams Field and finally to our
local GSE out here. The whole process takes a matter of a few
seconds. Our data rate is limited to only around 6 kbits every
second, but it is a remarkable feat of technology.
During our test, one of the most important things
was the integration of ANITA data into our datastream. When we
flew two years ago, we were alone and we only had to worry about which
of our data was important enough to be sent in the limited amount we
were able to send over TDRSS. This year, it is important for
ANITA to get as much good data as possible since it is a budding
experiment that has been highly regarded by the Balloon Program.
The test was one of the more grueling 3 hours that
I've spent down here, and it was further compounded by the fact that
our internet connection to Palestine, Texas is unspeakably slow.
But after all was said and done, it went extremely well. Our
group was able to multitask quite well during the test. Garry and
Dana made use of the TIGER up time to continue working on our thermal insulation shield.
Today, they began the laborious process of covering it in aluminized
mylar to reflect the intense sunlight that TIGER will see during flight.
We headed back at 5:30 to eat dinner and we were
lucky enough to see a little friend
on the way. We asked if he needed a ride, but he just waved us
on. Maybe some other time.
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