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Establishing
a
Real-Time
video
link
to
Antarctica
On November
24,
1992,
NASA
engineers implemented a real-time video link between McMurdo
Station in the Antarctic and the continental United States. The problems encountered and the
solutions developed in establishing a network in a harsh and isolated environment provide valuable
insights into the conditions space explorers will encounter in planetary exploration. These efforts
have enabled subsequent breakthroughs in technology applications, education, and telepresence.
Mark
Leon
MARK LEON is deputypro-
ject
manager for the NASA
Information Infrastructure
Technology and Applications
Project at Ames Research
Center and deputy program
manager for the NASA IITA
K-12Program.
8
n November 24,1992, NASA Science
,Internet (NSI) engineers implement-
ed the world’s first real-time video
link between McMurdo Station in the
Antarctic and the Continental United
States; this link was also the first real-time video
transmission accomplished from such a low latitude.
The effort, which built upon NSI’s existing Antarc-
tic high-speed data communications infrastructure,
was a response to last-minute requests from
major television networks for live coverage of the
National Aeronautics and Space Administration’s
(NASA) Mars analog experiments in Antarctica. To
meet broadcast requirements for bi-directional
video, NSI employed laser, microwave, and satellite
communication links, as well as a variety of video
codecs and multiplexers. NSI implemented sever-
al different network configurations within a short
period of time to accommodate requirements for
both live broadcasts and scientific experimenta-
tion with a remotely operatedvehicle. The problems
encountered and the solutions developed in
establishing a communications network, in a
harsh and isolated environment equipped with
World War I1 vintage equipment, provide valu-
able insights into the conditions space explorers
will encounter in planetary exploration. These
ground-breaking efforts have enabled subse-
quent breakthroughs in technology applications,
education, and telepresence.
NASA Science Internet engineers at NASA
Ames Research Center (ARC) in California have
implemented four different communication con-
figurations in the Antarctic to date: one was part
of NSI’s original Three-Year Plan; one was the
result of an urgent request by the ABC network,
NASA, and the National Science Foundation
(NSF); and
two
arose as a result of accomplishing
the second requirement.
NSI’s
Three-Year Plan included initiation of a 56-
Kb/s data link for Internet service in the first
year, 1991, with an increase to 128 Kb/s in the
second year. When the repositioning of a satellite
from inclined to geosynchronous orbit achieved
bit error rates of at 768 Kb/s, plans to increase
bandwidth for telepresence applications and
compressed video were accelerated. The increased
bandwidth performance indicated that proof-of-
concept testing at McMurdo Station could be
accomplished in 1992 instead of 1993.
An experiment simulating operation of a
Remotely Operated Vehicle (ROV) was there-
fore conducted in July 1992, and in November,
ABC presented an urgent request to use the
video circuit for a live broadcast for “Night Line”
and “Good Morning America”
15
days hence.
Because of the short deadline, NSI engineers
worked around the clock to implement the
requirement. The effort to establish the bi-direc-
tional real-time video link is described herein.
Background
n 1990, NSI engineers met with the National
I
Science Foundation (NSF) to pose NASA’s
Antarctic communication requirements for ’91, ’92,
and ’93. At that time, NSI envisioned high band-
width requirements to support compressed video
for the purpose of returning vision from a robot
exploring beneath the Ross Sea Ice Shelf. NSF
did not, however, include NSI’s requirements in
its bid for a communications implementation due
five years later, in 1995.
As a result, NASA developed its own Three-
Year Plan. The first year of the plan, 1991, includ-
ed requirements for 56 Kbis of data for Internet
service; the second year involved higher band-
width, also to support data; and the third year
was to involve yet higher bandwidth for telep-
resence applications and compressed video.
In 1991, NSI had a link to IntelSat 177 East,
which had an inclined orbit of 3”. This link pro-
0890-8044/95/$04.00
1995
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IEEE
IEEE
Network
March/April
1995
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for voice
to
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PSTN
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;
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beroptic
mux
Router:
,
i
512,384Kbls
McMurdo
i
Black
i
San
i
ARC
i
ARC
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Island
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Valleio.
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27,000
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Figure
1
.
Otvivicw
ofAntarctic
video
circuit
vided approximately six hours of dedicated real-
time connectivity between McMurdo Station
and the Sylmar Tracking Station in California. How-
ever, because the satellite was in an inclined
orbit, it was difficult to keep a lock
on.
Its aver-
age bit error rate of
as
it
entered the horizon prior
to
setting. Many
problems were experienced with this particular
implementation, including outages of several
hours at a time without
good explanation. The
service was run in its entirety for only about two-
and-a-half weeks of the originally planned two
months. The difficulties NSI experienced in
establishing the satellite link were exacerbated
by
the conditions in Antarctica, and in Black
Island and McMurdo Station, specifically. This
link, however, provided the infrastructure which
would be used in 1992.
In
the 1991 configuration, the entire 128-KbIs
circuit was channeled through the multiplexer
(MUX) into a voice multiplexer (RLX) for four
voice channels, and into the data router (Proteon)
for
56
Khis
of data (Fig.
2).
This particular imple-
mentation was jointly funded by NASA and NSF.
The 1992 configuration was originally planned
to
be much like that for 1991, and in 1993, NSI
planned to upgrade to higher bandwidths to pro-
vide compressed video. The compressed video
would be used
to
return video from the ROV
underneath the frozen lakes in the Taylor Valley
and to allow operation of the ROV remotely
from ARC. What actually occurred differs con-
siderably from the original plan.
dropped sharply to
W
Figure
2.
1991
Antarctic communications configuration.
Safeellife
Move
After the experiences in 1991 with the inclined
satellite, it became evident to NSI engineers that
a geosynchronous satellite would be required.
By organizing a contract with Comsat through
IDBISTARS, an inclined satellite was moved from
177"
East to 180" East, and a geosynchronous
satellite was moved from 180" East to
177"
East.
By switching the
two,
NSI gained access to a satel-
lite with much greater capability. NSI used an
LNB
with an ultra-high gain step on the antenna
assembly to communicate with this satellite, a
configuration which is much more powerful than
what is normally used.
On
the down-link we
received a 42.5 db signal-to-noise (SIN) ratio.
Aftcr moving the satellites and establishing
the link to the receiving stations at Vallejo, Cali-
fornia and Black Island, Antarctica, NSI was able
to get bit error rates of
10-8
operating at a total
bandwidth speed of
768
Kbis.
From Black Island
lEEE
Network
March/April
1995
9