Title : Facility to Support RADARSAT
Type : Antarctic EAM
NSF Org: OD / OPP
Date : January 5, 1994
File : opp94011
National Science Foundation
Office of Polar Programs
Washington, D.C.
ENVIRONMENTAL DOCUMENT AND
FINDING OF NO SIGNIFICANT AND NOT
MORE THAN MINOR OR TRANSITORY EFFECT
Facility to Support RADARSAT, A Joint Project of the
National Aeronautics and Space Administration (NASA) and the
National Science Foundation (NSF) at McMurdo Station, Antarctica
DECEMBER 28, 1993
I. FINDINGS
The National Science Foundation (NSF), the lead agency, in
cooperation with the National Aeronautics and Space Administration
(NASA), has prepared an Initial Environmental Evaluation (IEE) and
an Environmental Assessment (EA) as a combined environmental
document, for the construction of a
17-m diameter radome and 130-m2 support building 1.8 km from the
center of McMurdo Station, Antarctica. The facility, support
buildings for the RADARSAT project which is to receive satellite
data for ongoing and future scientific investigations, is to be in
operation for 15 to 20 years. Three to four people would be
required throughout the life of the project to provide year-round,
seven day per week, 24-hour per day staffing for remote operation
of the facility from the Crary Science and Engineering Center
(CSEC) in McMurdo. At the conclusion of the project, the facility
would be dismantled and removed from Antarctica, unless the
responsible decision-maker makes a decision with appropriate
environmental evaluation and decision documentation to continue use
of the facility, considering the condition of the facility and the
continued need for the facility.
It is possible to use the facility for radio frequency (RF)
transmission purposes at a future date. The decision to initiate
RF transmission operations at the site would be evaluated as a
separate decision after an assessment of radiation safety hazards,
electromagnetic interference (EMI) compatibility, and additional
environmental considerations were performed.
Based on the analyses in the environmental document (IEE/EA),
the NSF Office of Polar Programs (OPP) has determined that
implementation of Alternative D is not a major federal action which
would have a significant effect on the human
environment, within the meaning of the National Environmental
Policy Act (NEPA) of 1969 nor is the action one which would have a
more than minor or transitory effect on the antarctic environment,
within the meaning of the NSF implementing requirements for the
Protocol on Environmental Protection in Antarctica.
The selected alternative, D with identified mitigation,
provides for the construction, operation, and removal of two
buildings for support of the RADARSAT project. To lessen the
possibility of power outage at the facility, a comprehensive
analysis and power conservation program for McMurdo Station's power
plant and electric energy network will be initiated upon completion
of the buildings. Operation of the receiving dish would be
curtailed until an energy conservation and improvement program was
implemented.
Use of the facility or site for programs or projects other
than or in addition to the RADARSAT project would require
appropriate environmental evaluation and decision by the NSF. The
construction, operation, and removal of the facility is consistent
with the NSF's efforts to promote scientific investigations,
cooperate with other federal agencies, and protect the antarctic
environment.
s/Dr. Cornelius W. Sullivan 1/05/94
Dr. Cornelius W. Sullivan Date
Director, Office of Polar Programs
National Science Foundation
4201 Wilson Blvd.
Arlington, Virginia 22230
II. PURPOSE AND NEED FOR THE PROPOSED ACTION
The National Science Foundation (NSF) in cooperation with the
National Aeronautics and Space Administration (NASA) proposes to
construct, operate, and decommission a ground receiving station for
the capture of real-time data as an earth orbiting satellite
(synthetic aperture radar satellite) passes over McMurdo Station,
Antarctica. The ground station antenna, located north of McMurdo
Station (77 51' S, 166 40' E) near Arrival Heights (see Attachments
A, B, and C), would consist of a ten-m dish enclosed in a 17-m
radome and a 130-m2 building for electronic receiving equipment and
occasional use by a technician.
Construction of the facility requires an approximately
245-m long 3-m wide access way and installation of: a 1.8 km fiber
optic line from the CSEC at McMurdo Station; an approximately 396-m
power line from the station grid to the site; an underground
conduit between the radome and the support building for cables and
a boresight antenna with electronics equipment for communication
with the CSEC by telephone modem located near Building 126 on the
lower side of Observation Hill. The facility, 1.8 km from McMurdo
Station, is not near any areas of historical interest. However,
the site is near a Site of Special Scientific Interest (SSSI) No.
2 "Arrival Heights, Hut Point Peninsula, Ross Island".
The proposed facility would receive real-time satellite data
in the Ross Sea sector of Antarctica, where coverage provided by
the German ground station at O'Higgins Station in the antarctic
peninsula and the Japanese ground facility at Syowa Station,
Antarctica do not extend. The need for a ground station at McMurdo
is validated in a report by the U.S. science community (Reference
A). Data received would be used for scientific research of the
antarctic land mass and oceans.
The prefabricated buildings would be unmanned, except for
occasional maintenance work at the facility, requiring no water or
wastewater utilities. There would, however, be three to four
people throughout the life of the project providing year-round,
seven-day per week, 24-hour per day staffing for remote operation
of the facility from the CSEC in McMurdo. Emergency food and water
supplies would be provided at the facility. A maximum of 120 kVA
are required to operate the facility. Power would be provided by
generators located in nearby McMurdo Station.
Issues related to the proposed action are:
Removal of the facility when the RADARSAT project is
concluded;
Aesthetic effects of the facility;
Health and safety of personnel during construction and
operation;
Interference with ongoing or future science projects; and
Power and fuel requirements to build and operate.
III. ALTERNATIVES
Alternative A. Do not build the facility
This alternative is the "No action" alternative which is
required in the consideration of environmental effects. In this
alternative the NSF would take no action to develop the facility
and would not participate in the acquisition of real-time satellite
data.
Alternative B. Build the facility at the preferred site, a
knoll overlooking McMurdo Station
In this alternative the proposed facility would be constructed
on a knoll overlooking McMurdo Station. The facility would be in
operation for 15 to 20 years, after which it would be
decommissioned, dismantled, and removed from Antarctica. Any
materials that could be successfully used in other projects would
be recycled. Other materials would be sorted and retrograded from
Antarctica for appropriate recycling or disposal. Should continued
operations be desired at the conclusion of the RADARSAT project,
use of the facility would be considered within the appropriate
environmental review and decision by the NSF.
In the development of this alternative, four non-fossil fuel
energy sources for facility operation were considered. However, as
described below, non-fossil fuel energy sources do not appear
practical for operation of the facility in the extreme antarctic
environment.
Photovoltaic Cells (PV) PV cells are a well-developed,
extremely reliable method of harnessing solar energy, making them
ideal for small, remote, unattended installations. The efficiency
of commercial PV cells is about 10% to 15%. Their life expectancy
is about 20 years. Initial cost of a PV installation is about
$4000 per kVA, which is not competitive with other sources in
normal applications.
Wind Power A perfect wind turbine would convert about 60% of
the potential energy in wind into useful energy. Depending upon the
aerodynamic, electrical, and mechanical efficiencies of the
turbine, more realistic values range from 20% to 40%. Wind power
is an attractive alternative to diesel generators, and small units
have proven to be reliable in remote facilities. However, large
wind turbines capable of supplying energy required for the RADARSAT
facility have not been developed and tested in Antarctica's harsh
environment.
Fuel Cells The efficiency of fuel cells using petroleum
fuels, is higher than that of an internal combustion engine (nearly
60% compared to about 35% for a diesel generator). The emission
rates of nitrous oxide and sulfur dioxide for fuel cells is very
low and they create no noise. Fuel cells are still in the
developmental and prototype stage and are not suitable for reliable
operation at a remote facility.
Hybrid Power System A combination of alternate energy sources
could be used to create a hybrid system, much like that used at
Black Island, a facility run by the NSF not far from McMurdo
Station. However, Black Island's total power requirement of 5 kVA
is considerably less than the 120 kVA needed to operate the
RADARSAT facility. It is not known if such a system would meet
specifications needed to supply uninterrupted power for the
facility. Further study and demonstration is required.
All of the alternatives to diesel generators have qualities
which make them environmentally desirable, such as the reduction of
air emissions associated with burning fossil fuels and the
reduction in noise. Unfortunately, there is insufficient
information on system reliability to adequately assess safety and
utility of such systems for powering the facility.
Alternative C. Build the facility at a location other than
that proposed
In this alternative the facility would be constructed at a
site other than that described in Alternative B.
The Jet Propulsion Laboratory (JPL) was consulted as the NASA
representative for possible site selection. A primary concern was
finding a site that minimized horizon obstruction of a smooth, flat
view. An unobstructed view of Pine Island Bay (75 degrees south,
100 degrees west with a local azimuth bearing from McMurdo Station
of 90 to 120 degrees) would provide "line of sight" view of a
satellite 5 to 10 degrees above the horizon.
The horizon visibility from the rooftop of Building 165,
located in McMurdo Station, represented a worst case horizon view
due to the immediate surrounding hills. The JPL indicated that
this site was sub-optimal, and it would be a last choice if other
sites were not available. To minimize the horizon blockage by the
hills to the north and east of McMurdo, a site above the town
center ground clutter is needed.
Site evaluation examined prospective hilltop locations on the
perimeter of McMurdo Station. The availability of sites was
constrained by existing land use and by pertinent safety,
environment, and cost considerations. The site selection factors
included: proximity to roads and McMurdo Station for year-round
personnel access; minimal site preparation; horizon visibility; and
land use conflicts such as the existing explosives storage yard,
Arrival Heights Site of Special Scientific Interest (SSSI), radio
quiet zone, and high frequency (HF) radio receiving antennae.
Because horizon elevation clearance data were not available, a
physical site investigation was completed.
Four sites were examined (see Figure 1):
* The summit of First Crater (now the site of the New Zealand
Telecom satellite communications earth station);
* The summit of the knoll overlooking McMurdo Station and
located near the intersection of the Arrival Heights access
road and the main service road leading from McMurdo up the
overlooking terrain;
* The site of the existing HF receiving antenna (Rosette
phased array loop antenna) adjacent to the existing explosives
storage site; and
* The summit of Crater Hill.
The JPL indicated that all of these sites provided visibility
to Pine Island Bay. The proposed sites were then further
evaluated. The principal factors which eliminated three sites
were:
First Crater. This site conflicts with the management plan
for SSSI No. 2;
HF Receiving Antenna/Existing Explosives Storage Site. This
site conflicts with the current land use and would not be safe
for the facility; and
Crater Hill. This site is too remote and would require costly
construction. Also, due to travel distance from McMurdo
Station and severe weather, the site was considered unsafe for
routine use.
The summit of the knoll overlooking McMurdo appeared most
favorable. It has good horizon clearance, good proximity to
developed roads, close proximity to McMurdo Station, reasonable
site preparation requirements, and no conflicts with current or
anticipated land uses.
Alternative D. Build the facility as described in Alternative
B and develop energy conservation program for
McMurdo Station Power Plant
In this alternative, the facility would be constructed as in
Alternative B. However, an energy conservation program for the
electric power generating plant at McMurdo Station would be
implemented. Electric power to operate the facility would be drawn
from existing on-line and reserve capacity. Any encroachment upon
the generating safety margin of the existing power plant would be
compensated with the development and enforcement of an energy
conservation program.
IV. ENVIRONMENTAL EFFECTS AND MITIGATING MEASURES
Note that environmental effects refer to Alternatives B, C,
and D unless otherwise noted.
A. Removal of the facility when the RADARSAT project is concluded
Minor environmental effects are anticipated from
decommissioning the facility in 15 to 20 years. Heavy equipment
would be required to dismantle the radome and support building
causing some minor noise, exhaust, and dust from leveling and
reshaping the site. The underground conduit would also be removed
as part of the facility decommissioning. The site would be
returned to as close to a natural condition as possible. Leveled
areas would be reshaped to approximate the 10 percent slope of the
backside of the knoll.
The materials in the receiving dish and the dome will require
dismantling through approximately six months of specially skilled
labor. Electrical equipment and hardware that could be reused at
McMurdo Station would be replaced into inventory or used in ongoing
projects.
B. Aesthetic effects of the facility
The proposed construction site is currently used as a fill
material collection site. Heavy equipment routinely operates at
the site, collecting the top few inches of soil above the
permafrost. Therefore, ground disturbance would not be new, nor
would operation of heavy equipment in the area.
The addition of the antenna radome would impact the overall
aesthetics of McMurdo Station because it would be visible from
"downtown McMurdo" as well as from long distances. The size,
shape, and appearance of the antenna radome is dictated by its
function. Little can be done to alter these, other than changing
the color of the radome to blend into the local scenery. The
industry standard color is white which increases solar deflection
to keep minimum interior temperatures and avoid damage to
equipment. Cooling the equipment is not a major concern at McMurdo
Station. However, the white radome would blend well with the
predominate colors in summer, white and black.
The support building, which could not be seen from McMurdo
Station, would be dominated by the larger radome making it less
obvious. The top of the building would be below the antenna to
avoid obstruction of the horizon. This lower positioning of the
support building would make it less visible from observation points
below the site. A neutral color for the exterior would be selected
to blend with the slopes which are dark in the summer months when
most visitors are at McMurdo Station.
Fiber optic transmission lines placed on top of the ground in
protective conduit and power cables would be visible. Trenching
is required to place lines below ground. However, trenching is
very difficult to perform in the shallow soils and dense rock that
surrounds McMurdo Station. The placement of lines on the land
surface at McMurdo Station has proven to be effective. Portions of
cable will be placed underground at vehicle crossings to protect
the cable. The new cables would parallel existing cables between
McMurdo and Arrival Heights. The new section of cable run between
the existing cable splice box and the facility would be blocked
from view from downtown by the top of the hillside. In-town,
cables will be placed on stanchions or telephone poles.
C. Health and safety of personnel during construction and
operation
Rigging for crane operations would follow the guidelines and
requirements provided in the "Safety and Health Manual under the
Hoisting and Rigging Program".
Blasting operations would follow established procedures
utilizing containment mats to prevent debris from being dispersed
into the work area. The use of ear and eye protection is required
during these operations under the guidelines provided in the
"Hearing Conservation and Personal Protective Equipment Programs"
contained in the Antarctic Support Associates (ASA) Safety and
Health Manual. The ASA Explosive Safety Program is currently under
development. Additional guidelines from NSF are available.
Heavy equipment operators would pay special attention to
visibility problems, such as icing and fogging of windows, by
scraping ice from cab windows until adequately defrosted. Redesign
of the interior of the dome surface has eliminated the depression
in the center of the dome floor making it a safer work environment.
The safety of personnel that may contact power cables is a
concern. However, cables to be laid on the ground presents no new
or unusual hazards. Cables have been laid on the ground in
previous projects. The same proven precautions will be followed.
Concerns regarding welding and proper eye protection are
addressed in the Personal Protective Equipment Program contained in
the ASA Safety and Health Manual.
The following potentially hazardous jobs: Rigging for crane
operations; Blasting; Heavy equipment operations; High voltage
operations; and Welding have well trained and experienced personnel
available for job completion. All of the potentially hazardous
jobs listed are routine and accepted trades now in practice at
McMurdo every season.
Welding and metal fabrication would use oxygen and acetylene
tanks, high pressure hoses, and flammable liquids (mogas). Heavy
equipment operations would use rigging cables, hydraulic lines, and
their vehicles contain diesel fuel and oil. Potentially high winds
and rugged terrain present the dominant physical hazards. Extreme
caution will be used during operations being conducted during windy
conditions or on rugged terrain.
Vehicles, including those used for collecting fill material,
occasionally traverse through the area between the proposed
facility and the existing splice box where new cables will be set
on the ground. To protect the cables and prevent the cables
(including the 4160 V line) from posing a safety concern to
personnel working in the area, a portion of the cable would be set
underground in a conduit to create a road crossing. Flags and
signs would be used to advertise the presence of the cable and
direct personnel to road crossings.
D. Interference with ongoing or future scientific projects
In Alternative A, the NSF and the scientific community would
not be able to acquire highly valuable scientific data from a
unique space-based remote sensing satellite as it passes over the
Ross Sea area.
The facility site in Alternatives B and D, is located very
close to SSSI No. 2 (Arrival Heights, Hut Point, Ross Island; see
Attachment D). The main receiver in the facility is a receive-only
device which would not create any high frequency interference that
could disrupt sensitive electromagnetic investigations or
communications. Thus, there should be no direct interference
problems for nearby instrumentation.
The boresight antenna would transmit at three discrete
frequencies in the range of 2250 Mhz, and it would also transmit at
three discrete frequencies in the range of 8025 to 8400 Mhz with a
three decibel (dB) bandwidth of two degrees at 8213 Mhz. There are
no current or proposed science projects based at SSSI No. 2 that
operate in the electromagnetic spectrum used by the boresight
system. Therefore, no adverse effects are expected in the
short-term.
Present research interests do not indicate any sensitivities
in the identified spectrum. The emitter is located outside the
SSSI boundaries and isolated by the natural terrain. In addition,
the boresight would not continuously emit energy. It would be used
only for a short time prior to each tracking operation, projected
to be four to six times per day. These events are easily recorded
and could be readily evaluated for impacts on existing or proposed
science projects.
E. Power and fuel requirements to build and operate
The power requirement for the operation of the radome, the
largest power user of the facility, is estimated to be
approximately 56 kVA per day. This estimate is based on the
assumption that the satellite would pass over six times per day for
15 minutes (900 seconds) per pass. Maximum power draw would
be 120 kVA for 5 seconds per pass. Steady power draw would be 75
kVA during a pass while quiescent power draw for the entire system
when not tracking would be 55 kVA.
The average power draw per pass would be: (5/900)*120 +
(895/900)*75 = 75.25 kVA. With six passes per day at 900 sec per
pass, 5400 tracking seconds per day and steady power draw, the
system would require: (5400/86,400 seconds per day)*75.25 +
((86,400-5400)/86,400 )*55 = 56 kVA per day.
Fuel use for the construction of the facility would be minor.
Fuel to operate an oil fired furnace at the site would be stored in
a day tank similar to those located in McMurdo Station. The
furnace in the support building is needed to maintain proper
temperatures for equipment housed in the facility. Standard
operating procedures would be employed to refill and maintain the
tank to prevent spills from occurring.
F. Short-term effects
Environmental impacts would be expected from the preparation
of a site to erect the enclosures. Some grading and trenching
would be required which could produce dust. Explosives may be used
to loosen the soil below the permafrost as necessary to grade a
level site. Dust emissions would be kept to a minimum by wetting
the area with brine water when weather conditions warrant its use.
Because the structures are prefabricated, little waste would be
generated during construction.
The number of personnel at the site and transportation to and
from the site would be highest during construction. After
construction is completed, personnel would only be at the site to
perform maintenance and repairs to equipment.
No change in water quality or flow would occur at the site.
There is no defined pattern at the site that would be altered by
the construction of the proposed facilities. A culvert would be
placed under the proposed road at a point where drainage does
occur.
Hazardous materials would not be used or stored at the site.
Human waste from personnel temporarily working at the site would be
collected and disposed of through McMurdo's human waste disposal
facility.
G. Long-term and cumulative effects
The long-term and cumulative effects of operating the facility
may be important to the total electrical power requirements of
McMurdo Station. If power for the receiving dish
were drawn when reserve generating capacity was not available due
to equipment failure, maintenance requirements, or severe weather;
power could be unavailable to operate the facility.
To lessen the possibility of power outage at the facility, a
comprehensive analysis and power conservation program for McMurdo
Station's power plant and electric energy network would be
initiated by the NSF upon completion of the buildings in
Alternative D. Operation of the receiving dish would be curtailed
until an energy conservation and improvement program was
implemented. Implementation of the program would ensure that
electrical power would be available to the facility without
curtailment of operation or reduction of necessary services at
McMurdo Station.
Transportation of personnel to maintain and repair equipment
would add to exhaust and fugitive dust emissions. The impacts from
these infrequent tasks are considered minor.
The project will require a minimum of three to four people;
seven days per week; 24 hours per day in CSEC year-round. This
will require one dedicated room in CSEC (room 205), 21.5 m2 for
both the austral summer and winter.
H. Unavoidable effects and irretrievable and irreversible
commitment of resources
Use of fuel in the construction and operation of the facility
is an irretrievable use of natural resources. However, this use of
available petroleum resources is considered to be minor. No action
undertaken in the construction of the facility or its use
represents an irreversible condition to the antarctic environment.
I. Consistency with the plans and programs of the NSF and others
Construction of the facility would support the implementation
of the RADARSAT project. The radome and support building would
change the traditional use of the proposed site. The site has been
disturbed for the gathering of road fill and structures have never
been placed there. Although there would be a change in the
traditional use of the proposed site, the physical and
environmental characteristics of the neighboring environment are
suitable for the proposed activity.
K. Mitigation of other environmental effects
The impacts associated with construction of the facility would
be mitigated as follows:
Construction of the antenna and radome foundations
The antenna and radome foundations require site preparation.
An area approximately 335 m2 capable of accommodating the 17-m
radome would be cleared of rock debris larger than 15 cm. The
area would then be graded level and fill material would be removed
and stored for backfill. Explosives may be required to open a
trench approximately 3.05 m in the bedrock for placement of a 1.5-m
diameter tube connecting the radome to the support building. The
tube would house communications and electrical wiring. Standard
safety procedures and precautions will be used to place and set
explosive charges. The possible use of explosives is not unusual
or a unique risk to personnel or the environment.
An area of approximately 1500 m2 would be impacted by the
movement and set up of a 70-ton Grove crane used to erect the
radome. Activities would be confined to the areas described above.
Backfill would be compacted using brine water from the water plant
to maintain a satisfactory compaction density. The water would
also be used to control dust emissions from the site, if necessary.
Precast, reinforced concrete slabs manufactured in the United
States would be used for the foundations, thus eliminating the need
for manufacture on-site and, in turn, reducing construction debris.
Precast slabs may be reused upon decommissioning the facility.
Construction of the support building
An area approximately 2790 m2 would be impacted by
construction of a 130-m2 support building erected approximately
30.5 m from the radome. The proposed site for the building would
require regrading to lower it a maximum of 1.22 m. An area
approximately 1045 m2 would be regraded. Construction activities
would be confined to the designated area to mitigate environmental
impacts. Brine water would be used to control dust emissions when
weather conditions warrant its use. The building would be
prefabricated in the United States, thereby reducing waste
generated during on-site construction. Surface water drainage
would be directed away from the building to prevent frost heaving
damage.
Construction of site access way
An access way of approximately 245 m would be required to link
the proposed facility to the main road. Construction would require
little more than grading to provide a smooth surface for vehicles
to pass over. Construction of a roadbed is not needed at the site.
Culverts would be installed where necessary to allow natural
drainage to occur.
Installation of a Fiber Optic line
A fiber optic line would be installed from the facility to the
CSEC, approximately 1.8 km. The line would have 24 single-mode
fibers in Uniduct (single cable). It would be placed on the ground
near Building 143, then on existing poles and stanchions to the
CSEC. No adverse environmental impact is expected.
Installation of a power line
No special requirements are needed for installation of the
power line.
Consideration for wildlife near the site
The site is not habitat for any significant assemblages of
wildlife. The site has been visited by South Polar Skuas. In the
unlikely event of the discovery of nesting skuas, precautions would
be taken by workers to avoid disturbance of the nest and birds.
V. CONSULTATION WITH OTHERS
Ms. Carol Andrews Environmental Engineer, ASA
Mr. Frank Brier Facilities Manager, NSF/OPP
Mr. Erick Chiang Manager Polar Operations, NSF/OPP
Mr. Robert Cunningham NEPA Compliance Manager, NSF/OPP
Dr. Jane Dionne Acting Environmental Officer, NSF/OPP
Dr. Harry Mahar Health and Safety Officer, NSF/OPP
Mr. Peter Karasik Associate Compliance Manager, NSF/OPP
Dr. Steve Kottmeier Manager, Laboratory Services, ASA
Mr. Terry Johnson Environmentalist, ASA
Mr. Quentin Rodin Lead Blaster, ASA
Mr. Patrick Smith Electronics Engineer, NSF/OPP
Mr. Michael Young Director, Information Systems, ASA
ATTACHMENTS
Figure 1: Sites Considered for RADARSAT Facility
Attachment A: Facility Site Location
Attachment B: Facility Site Plan
Attachment C: Facility Site Profile
Attachment D: Sites of Special Scientific Interest No. 2,
Arrival Heights, Hut Peninsula, Ross Island
References and Background Information
(References are available at NSF/OPP offices Arlington, VA)
A. McMurdo SAR Facility. Ad Hoc Science Writing Team, BPRC
Technical Report #91-01, Byrd Polar Research Center, Ohio
State University.
B. Carter, William. 1991. The Scientific Benefits of a
Geodetic VLBI Station at McMurdo. National Geodetic Survey,
Rockville, MD.
C. NSF and NASA. 1993. Memorandum of Agreement between the
National Science Foundation and the National Aeronautics and
Space Administration for Spacecraft Tracking and Data
Acquisition at McMurdo Station, Antarctica, September.
D. Naval Electronic Systems Engineering Center. 1993.
Electromagnetic Environmental Effects (E3) Survey, Arrival
Heights Site of Special Scientific Interest (SSSI) No. 2 for
McMurdo Station, Antarctica. Charleston, South Carolina.
January.
E. Hewlett-Packard Company. 1992. EMI Site Survey at
Amundsen-Scott Station, McMurdo Station, and Black Island.
Fullerton, CA.
F. Smith, P.D. 1993. Staff Paper. Description and
Requirements of the RADARSAT Project.
BC:JD:PK:pk/RADAR1.doc
DESCRIPTION AND REQUIREMENTS OF THE RADARSAT PROJECT
Prepared by Patrick D. Smith
NSF, Office of Polar Programs
December, 1993
I. Description of RADARSAT Project
The National Science Foundation, Office of Polar Programs
(NSF/OPP) and the National Aeronautics and Space Administration
(NASA) Ground Networks Division, have a Memorandum of Agreement
(MOA) for the installation and operation of a large aperture
satellite tracking ground station at McMurdo Station, Antarctica
(77 degree 51 minutes S, 166 degrees 40 minutes E). McMurdo
Station is the largest of the three year-around antarctic
research stations maintained by the United States.
NASA, through its funded science support activities
conducted at the Jet Propulsion Laboratory (JPL), contacted
NSF/OPP in early 1990 regarding the support of a large satellite
tracking station at McMurdo Station. NASA has entered into a
long-term agreement with the Canadian Space Agency (CSA) for
access to data produced by the forthcoming CSA remote sensing
satellite, RADARSAT. RADARSAT is a low earth orbiting satellite
in a sun synchronous polar orbit that carries a synthetic
aperture radar (SAR) imaging system as its primary payload. The
RADARSAT SAR imager represents a follow-on to the successful
European Space Agency ERS-1 satellite, launched in August, 1991,
which also carries a SAR imager. A primary objective of JPL was
to establish a data receiving station at McMurdo Station to
complement the two existing antarctic receiving stations, one run
by Germany at the Chilean O'Higgins Station and one run by Japan
at the Japanese Syowa Station, originally constructed for the
ERS-1 mission and future missions, such as RADARSAT.
SAR imagery is produced by the active illumination of the
ground by the satellite imager with microwave signal, with the
satellite recording the signal backscattered by the ground. In
the case of RADARSAT, the imager will be able to produce images
with a resolution of 30 meters. The use of microwave imaging,
instead of the familiar visible light or near infrared, is that
the microwave illumination and reflection can penetrate cloud
cover and the electromagnetic frequency of the microwave energy
can reveal surface detail and properties that are not possible
with the optical wavelengths. The value of all-weather imaging
for Antarctica is highly significant given the high level of
cloud cover over the continent at any given time. Additionally,
due to the absence of sunlight at the extreme southern latitudes
for a large portion of the year, the SAR imager enables imaging
to continue on a year-around basis, while optical imaging must
cease during a portion of the year.
The value of SAR imagery in support of antarctic science has
been documented by the report contained in Reference A.
The ability to recover a continuous, daily or near-daily, stream
of SAR images from Antarctica enable the first ever detailed
surveillance of Antarctica and its surrounding sea ice such that
fine time scale events can be monitored on a continental basis.
It should be noted that NSF/OPP funds a significant amount of
glaciological and sea ice research that would have a direct
research interest in the imagery of Antarctica produced by
RADARSAT. NSF/OPP funded scientists participated in the
development and recommendations provided in Ref. A?.
The intent of JPL, on behalf of NASA funded sea ice and
glaciology science, was to establish a ground station in West
Antarctica that would fill a coverage gap that results from the
incomplete coverage of Antarctica and the adjacent seas from the
two existing ground stations. This is of great significance,
since the high data rates produced by SAR imagery satellites
either preclude or highly limit the on-board storage of raw image
data. Thus, in order to recover the raw data produced by the
imager, it is necessary to have a ground receiving station able
to maintain "line of sight" tracking as the satellite passes over
the scene of interest.
The high latitude of McMurdo Station enables it to "see"
approximately 10 of the 14 revolutions per day that RADARSAT will
make over Antarctica. With each revolution, RADARSAT will image
a different ground scene, and the orbit is designed such that a
given ground track will repeat after a finite lapse of days, such
that the entire continent of Antarctica north of approximately 80
degrees south will be completely covered through one master
repeat cycle. McMurdo's unique location will permit it to
collect data throughout all of West Antarctica and the
surrounding continental ice margin for the development of a
thorough and routine time series never before possible.
In parallel with the initial dialogue with NASA and JPL
regarding the value of a SAR imagery ground receiving station at
McMurdo, NSF/OPP was also approached by the National
Oceanographic and Atmospheric Administration National Geodetic
Service (NOAA/NGS) regarding its scientific interest in
implementing a radio astronomy receiving station at McMurdo
Station for the purpose of Very Long Baseline Interferometry
(VLBI), and the requirements of a VLBI receiving station can be
parallel to those of a SAR receiving station.
VLBI entails the observations of galactic noise sources that
have extremely time/frequency stable radio emissions such that
the sources can be used as extremely accurate triangulation
references. When two or more VLBI receiving stations
simultaneously observe and record the emissions of a galactic
source, a combined data analysis can reconstruct the baseline
separation between the two ground stations to a precision of a
few millimeters, all on the scale of continental separations.
VLBI observations have many uses in the field of geodesy, such as
the measurement of continental drift and orbital dynamics studies
of the earth, and the scientific merit of a receiving station at
McMurdo is documented in the NOAA/NGS report contained in Ref. B.
Much the same as for the NASA/JPL interest in filling a
coverage gap over West Antarctica by placing a receiving station
at McMurdo, NOAA/NGS desired a VLBI station at McMurdo to fill a
gap in coverage for the production of baselines that tie
Antarctica to the other continents. The existing SAR receiving
stations at O'Higgins and Syowa also double as VLBI receiving
stations. The common attributes are, in general, the size of the
antenna (large apertures are needed), the fact that a tracking
antenna is needed, and the general complexity and sophistication
of the electronic systems required to receive and record the
signals.
It became readily apparent to NSF/OPP that the natural
synergism that occurred at the other antarctic SAR receiving
stations should also occur for the proposed McMurdo SAR station,
lending even further weight to the value of a McMurdo facility.
As the course of the dialog between NSF/OPP and NASA
continued regarding the issues and uses of the proposed McMurdo
tracking station, it became apparent to NASA that the facility
could also be of value for future operational requirements in
support of NASA science satellite launches. A large number of
earth remote sensing and research satellites scheduled or
proposed for launch well into the next decade are intended for
polar orbit. An example will be the forthcoming Mission to
Planet Earth, Earth Observing Satellite (EOS) series intended for
long term global change monitoring. Many of these satellites
will be launched south from Vandenberg Air Force Base in
California into polar orbit. In order to assist in early orbit
insertion maneuvers, NASA must rely on special aircraft outfitted
with telemetry tracking systems, to collect spacecraft telemetry
and relay it back to launch operations as flight controllers
adjust periodic spacecraft thruster firings to place the
satellite into proper orbit. These orbital maneuvers are
critical to the success or failure of multimillion dollar space
missions. The extreme southern oceans in the Pacific, and in
particular Antarctica, represent a gap in the data coverage for
these critical maneuvers. The special aircraft cannot penetrate
as far south as the viewing represented by a McMurdo ground
tracking station. Additionally, each launch of this special
aircraft has an expense on the order of $350,000. It is quite
likely that an aircraft will launch in support of a satellite
launch, only to find out that the satellite launch was terminated
at the last minute. However, the commitment in funds has
occurred regardless, as the aircraft must launch some time prior
to satellite liftoff in order to be prepositioned. NASA has
determined that it will be of potential operational benefit to
use a ground tracking station at McMurdo to augment, or perhaps
replace, the special aircraft used for launch operations. This
would greatly benefit the overall NASA mission. Consequently,
another value for a McMurdo satellite tracking facility was
identified.
A survey of the various uses proposed by the SAR-class
satellite ground receiving station indicate that it jointly
supports significant and long term scientific and operational
requirements of three different U.S. Federal agencies. The
common factors among these requirements are the size and
complexity of the ground station, the logistics infrastructure
required to operate and maintain such a facility in a remote
location, and the unique high southern latitude afforded by the
location of McMurdo. As such, the proposed McMurdo satellite
receiving station is considered by NSF/OPP and NASA as a
significant national resource.
As the executive manager of the United States Antarctic
Program, NSF/OPP is uniquely distinguished from all other Federal
agencies to provide leadership pertaining to the U.S. national
interests in Antarctica. It is for this reason that NSF/OPP and
NASA have entered into an agreement pertaining to the
implementation and operation of a McMurdo satellite ground
receiving station.
II. Requirements of RADARSAT Project
1.0 Satellite Visibility Dynamics
The proposed satellite ground station is intended to track
low earth orbit, polar orbiting satellites. This general class
of satellites have orbital altitudes of typically 750 km, with a
resulting orbital period of typically 100 minutes and a resulting
number of total revolutions of the earth of typically 14
revs/day. Because of McMurdo's latitude, approximately 10 to 12
revs/day of this type of satellite can be seen, with sky tracks
that can occur at almost any location in the sky. The sky tracks
will have varying rise and set azimuths, and the sky track
elevation when the satellite is at closest approach can vary from
below the horizon to local zenith. A typical satellite
overflight, or pass, can last for as few as 5 minutes to as many
as 15 minutes.
1.1 Horizon
A consequence of the satellite pass dynamics described above
is that the tracking antenna system must be able to acquire the
signal when the satellite is low on the horizon. This is
beneficial for tracking satellites with maximum elevations near
zenith, as these satellites have a high relative motion with
respect to the ground, which result in radio frequency effects
(the Doppler shift) that complicate late acquisition of the
signal.
Additionally, there is a specific geographic location of
particular interest to NASA glaciologists, as specified by JPL,
that of Pine Island Bay (approximately 75 degrees south, 100
degrees west). The typical satellite geometry described above
will result in a visibility from McMurdo of roughly 7 degrees to
15 degrees in elevation of a satellite that is directly above the
Pine Island Bay coordinates. In order for the McMurdo satellite
ground station to track and acquire data from this area of
special interest, the local horizon of as seen from the ground
station must be clear to at least 5 degrees in elevation, or as
close as possible to this level. The local azimuth bearing from
McMurdo to Pine Island Bay is in the vicinity of 90 degrees to
115 degrees. Thus, the McMurdo ground station location needs to
have a clear view towards the East to East-Southeast.
Although the view to the East was the most sensitive horizon
clearance azimuth specified by JPL, a general requirement by JPL
was to find a location with the best possible horizon, including
the North. This general requirement is to maximize the ability
of the system to acquire satellites low on the horizon and to
extend the view towards the marginal sea ice zone to the North,
another area of particular scientific interest.
2.0 Facilities
The general requirement calls for two primary structures at
the tracking site: the antenna under a protective enclosure, and
a man-rated (i.e., heated, thermally controlled) building to
house all of the specific electronic systems that must be close
to the antenna system due to design constraints. Two additional
facility requirements are required: a manned control room
provided within a building within the confines of McMurdo town
center and an unattended antenna calibration target (referred to
as the boresight facility) located within a few km of the
tracking antenna and no lower in elevation than 3 degrees below
the zero degree elevation reference of the tracking antenna.
2.1 Tracking Site
2.1.1 Antenna
The antenna is required to be housed under a radome for the
protection and survivability of the antenna system. The system
design for the facility requires an antenna of a diameter of 10
meters. This antenna must be mounted on a high slew-rate
elevation over azimuth tracking antenna system, with this type of
antenna system a standard for tracking low earth orbit satellites
at the orbit geometries described above and representative of
RADARSAT.
The antenna is consequently very massive, and it also
represents a significant wind load. McMurdo frequently
experiences storm winds with peak gusts above 125 knots, and
sustained winds above 100 knots. These high winds would cause
destruction of an exposed antenna system, unless great additional
expense, well beyond the expense of a protective radome, were
taken to harden the antenna. Additionally, the mechanical
resistance caused by the wind loading of the exposed antenna
would, on occasion, cause an added load on the tracking antenna
motors. To compensate for this load, thus enabling tracking in
winds below the level where the antenna has to be stowed in a
protective mode, would require a greater electrical power
consumption for larger motors. Thus, in the interests in power
economy and in the enhanced survival of the antenna system, the
use of a protective radome was specified as a necessary component
of the facility.
2.1.2 Electronics Support Facility
A key design goal of this remote facility is that the day-
to-day tracking operations that require human operators to
interact with equipment will be conducted remotely within the
confines of McMurdo, proper. Thus, during normal operations and
when alignments and maintenance is not required, the electronics
support facility at the tracking site is unmanned.
The architectural design for the support facility will
reflect this general design goal with the square footage devoted
to the facility. A single building of approximately ???? square
feet will be required for an environmentally controlled
electronics room, an electronics bench repair room, and limited
storage.
The support facility cannot be more than approximately 75
meters from the tracking antenna. This is a design constraint
imposed by signal losses between the electronics in the support
facility and the antenna, as specified by Scientific Atlanta.
Another requirement for the support facility, mainly due to
its close location to the tracking antenna, is that the roof of
the support facility must be at, or slightly below, the zero
degree reference elevation of the tracking antenna, and the
support building must not block the view of the boresight
facility. This building elevation constraint is to prevent the
support building from blocking the low elevation horizon view of
the tracking antenna.
2.1.3 Control Room
Approximately 300 square feet have been identified as
required for the equipment, office space, and personnel space for
a maximum of three operators. This space will represent the day-
to-day human interface to the entire tracking facility. This
space will have a control computer and high density magnetic tape
drives that constitute the remote control and data recording
interface of the system.
A location within the Albert P. Crary Science and
Engineering Center (CSEC) has been identified, Room 205, as a
suitable location for this application. The CSEC was specified
as a location for the control room as it represents the focal
point within McMurdo for scientific activity. It possesses many
desirable attributes: an environmentally controlled atmosphere
for sensitive electronic equipment, an advanced computer network,
readily accessible computer technical support, an electronics
shop and associated technical support, and controlled access. It
is felt that the general type and scope of activity, as well as
the end product being acquired (SAR imagery in support of
science), was compatible in scope with the activities that the
CSEC was designed to support.
2.1.4 Boresight Facility
A routine pre-track operations procedure for this class of
satellite tracking station is to calibrate and test the tracking
and signal acquisition systems with a local, low power
transmitter located on the ground and within line of sight to the
main antenna. The final location of the main antenna will
dictate the final location of this boresight facility. The basic
requirements are that a small tower be erected to mount two small
parabolic antennas, on the order of 0.7 meter in diameter, and be
within a certain specified maximum cable run length to a small
heated enclosure to house the transmitters and a telephone data
modem for remote control via the local telephone system. The
heated space needs not be more than the size of a small closet.
A general limitation is that the boresight facility cannot
be more than a few km distant from the main antenna, and the
boresight facility cannot be any lower in elevation that
approximately 3 degrees below the zero degree elevation reference
of the main antenna. This is a design limitation of the antenna
system provided by Scientific Atlanta.
3.0 General Site Selection and Criteria
3.1 Proximity
The general operation philosophy required by NSF/OPP to
drive the design of the RADARSAT system was that of the remote
facilities, i.e. the tracking antenna and related electronics
support building, would be operated remotely from within McMurdo,
thus requiring no personnel continually man the site.
However, it was acknowledged that personnel would typically
have to go to the site on the order of 1 day per week for routine
maintenance. Additionally, in the event of a system failure,
personnel would have to commute to the site on a daily basis
while troubleshooting and repairs were in progress, a length of
time that can vary based on the nature of the problem, but a
condition that could conceivable result in daily commuting be
required for up to 14 days in duration, with on-site occupation
extending up to 12-14 hours per day.
The potential for a high visitation rate and lengthy daily
stay during a repair scenario places a constraint on the distance
from McMurdo town center that can be prudently accepted,
especially in the case of winter operations. Past experience
from the operation of outlying facilities such as the U.S.
Arrival Heights Laboratory and the Cosmic Ray Observatory have
indicated that there is risk of personnel becoming stranded at
outlying facilities during winter storms, sometimes lasting 2-3
days in duration. Additionally, the roads become dangerous or
impassible.
A general design constraint was defined for proximity so as
to minimize the risk to the safety of personnel that might be
travelling to, and working at, the remote facility during the
winter. Thus, general site selection criteria were defined as:
(1) the remote sight should be on or close to established roads
that can be maintained during the winter and (2) the site should
be as close as practical to McMurdo town center.
An additional reason for proximity, unrelated to personnel
safety, is that of reasonable access for the delivery of
electrical power and telecommunications utility lines. The
utility services for the remote facility must be provided from
McMurdo proper. Close physical proximity to McMurdo minimizes
the expense, possible environmental effects, and land use
conflicts from a very long utility run.
3.2 Initial Site Selection
3.2.1 Reference
For initial reference purposes, a generic site located
within the confines of McMurdo was examined for the suitability
of the horizon. This was easily accomplished with horizon
profile data on file within the USAP program for a location
surveyed from a small satellite tracking antenna platform (the
South Pole Satellite Data Link, or SPSDL) located on the roof of
Building 165, the U.S. Navy administration and radio
communications center building. This horizon data was passed to
JPL for evaluation against their minimum elevation criteria. JPL
indicated that this horizon profile was suboptimum, especially in
regards to the critical azimuth to Pine Island Bay, which was
almost completely blocked. JPL indicated that a site with this
type of visibility would be a last choice.
A site in or near Building 165 represents a typical best
case horizon view from within the McMurdo urban area. This
location is fairly centered with respect to the surrounding hills
to the North and East. Additionally, it is about as far from the
hills, displaced in the direction of the shoreline, as possible
without reaching a local downslope that leads to the shoreline.
This site was not seriously considered as a location for the
RADARSAT tracking antenna for the following reasons: there is no
existing open space that the antenna could be placed that would
not have local buildings blocking the horizon view from close in,
and the weight and structural dynamics of the tracking antenna,
under the protective radome, would result in a much more
expensive and difficult to construct installation if the antenna
were built on an elevated tower, as opposed to the suggested
design that would use precast concrete slabs and placing the
antenna essentially at ground level.
3.2.2 Identification of Potential Sites Meeting the Proximity
and Horizon View Criteria
Given the impracticability of a McMurdo urban center
installation, a review of contractor (Antarctic Support
Associates) McMurdo vicinity plot plans was conducted to identify
the following potential remote tracking antenna sites:
(1) Summit of First Crater (boundary of Site of Special
Scientific Interest No. 2, SSSI #2, Arrival Heights)
(2) Crest of small knoll, no name, overlooking McMurdo and
near the junction of the road turnoff that leads to
Arrival Heights, a site proposed by the previous
contractor, ITT/Antarctic Services, for a new
explosives storage yard
(3) A variant combination of either the existing HF Rosette
receiving antenna site (a small knoll overlooking the
existing explosives storage yard), or the plateau that
hosts the existing explosives storage yard
(4) Summit of Crater Hill
(5) A site within Arrival Heights, SSSI #2, between the
U.S. laboratory building and Second Crater (primarily
to spot check horizon)
No other locations appeared identifiable from available maps that
had the appearance of meeting the criteria.
During January, 1991, a preliminary physical site
investigation was made of all four sites described above. The
physical inspection consisted of a walk of the site to gain a
familiarity with the presence of any indigenous flora or fauna,
the nature of the soil, the actual proximity of access roads, the
actual distance from McMurdo proper, any difficulties that site
location might pose to heavy equipment needed for construction,
existing land use conflicts, and salient horizon profiles.
Following the physical site investigation, a memorandum for
record was created that documented the findings as was used as
reference material for subsequent discussions regarding site
selection with various interested parties. A post survey
discussion revealed the following assessments for the various
sites:
> All sites tended to possess reasonable horizon profiles
with respect to JPL requirements. Some sites were
better than others, most notably the summit of Crater
Hill, which is the tallest point at the McMurdo end of
Hut Point Peninsula. The summit of First Crater had
the second best general view, followed by the unnamed
knoll and the HF Rosette antenna knoll, in that order.
> The HF Rosette antenna knoll/existing explosives
storage yard had the best proximity to McMurdo,
followed by the unnamed knoll, followed by First
Crater, followed by Crater Hill.
After an initial review, the following eliminations were made:
> The summit of Crater Hill was eliminated because of its
remoteness and because of physical access problems. A
construction road would have to be built up a rather
steep incline in loose soil/permafrost in order to gain
access to the summit for the heavy construction
equipment and long term access. It was noted that an
original site for the ASR-8 surveillance radar was
proposed for the summit of Crater Hill, and the ensuing
on-site construction evaluation resulted in the current
sitting on the southern slope of Crater Hill, well
below the summit, within the maximum reach of a
construction road that was extended from the HF
Transmitter Site plateau to the base of the final
ascent of the upper slope of Crater Hill. This was a
pre-existing example of the practical limitation of
construction at this location.
> The summit of First Crater, or any site within the
confines of SSSI #2 at Arrival Heights, was eliminated
on a matter of general principles. It was felt that
this could represent a possible conflict with the
management plan for SSSI #2 adopted in 1974 by the
Antarctic Treaty Consultative Members, as recommended
by the Scientific Committee on Antarctic Research, as
later amended and extended. Although the original
purpose of the RADARSAT facility was of a radio
frequency reception nature only, and thus falling
within the general scope of the management plan, it was
felt that the apparatus of the tracking facility itself
and the possible future requirement to transmit would
represent a conflict with the scientific research
conducted within SSSI #2 should the facility be located
within the boundaries of the SSSI.
The remaining choices were the unnamed knoll and the HF
Rosette/explosives site. A problem then existed with a review in
progress regarding the outstanding recommendation to relocate the
explosives storage site to the northern side of the unnamed
knoll. The recommendation to relocate the site was under
critical examination by the new NSF/OPP Safety Officer, beginning
in the 1992/93 austral summer season. This review was assisted
by an electromagnetic reconnaissance commissioned to characterize
emissions from the ASR-8 radar and the electromagnetic
environment at the U.S. Arrival Heights Laboratory, as well as
selected sites in the hill line above McMurdo. A zero based
review of the explosives requirements that drove the original
design proposal for the new site was also under way. Until a
final recommendation was reached for the future of explosives
storage, both sites were tied up with respect to the RADARSAT
project. The HF Rosette antenna knoll was eliminated as a
possibility in that no presently known location was available for
relocation of the antenna, and the antenna system could not be
decommissioned, as it is the primary receiving antenna for Navy
operations.
By mid-year 1993, the NSF/OPP Safety Officer issued a
finding that placed the long term location for explosives storage
at the historical and current site, with directed modifications.
This freed the unnamed knoll site to be the recommended location
for the RADARSAT tracking facility. Coincidentally, this site
also represented the preferred site by the NSF/OPP Electronics
Engineer, the individual conducting the original site selection
survey.
3.2.3 Salient Features of Unnamed Knoll
This site possesses the following features:
> the site has been historically used for the collection
of fine fill material for general construction and road
maintenance, as well as a processing (sifting) site for
this work
> consequently, the site is previously disturbed, to a
high degree of significance, and has long lost its
pristine condition
> the summit of the knoll appears to have been reduced in
elevation such that the site no longer possess its
natural contours
> the juxtaposition of the knoll peak and the adjacent
terrain that slopes towards the north and east
represent an ideal configuration for the requirement of
the antenna to look above the roof line of the near-by
support building and to possess an unobstructed view in
the azimuth of Pine Island Bay; the natural contour
permit this with a minimum of earth work and permit the
antenna foundation design of choice - concrete slabs at
ground level
> the site is immediately adjacent the main access road
that rises out of the McMurdo urban area and leads to
the U.S. Arrival Heights Laboratory; thus the road is
maintained during the winter for access to Arrival
Heights, and is travelled for other purposes on a
routine basis all year around
> the site is within close reach to an existing
electrical power and telecommunication utility run that
extends from the McMurdo urban area to the U.S. Arrival
Heights Laboratory; this will permit a reduction in
construction costs and will permit the co-use of an
existing utility run to minimize the additional utility
lines that must be run to the site
> the site affords an unobstructed view to the existing
facilities (Buildings 87/89) on the side of Observation
Hill, such that the Observation Hill facilities can be
used as a boresight facility; the look angle depression
and the line of sight separation fall within acceptable
parameter limits as set by NASA and Scientific Atlanta;
because of the use of the existing facilities and
utility support of the Observation Hill facilities, the
installation and cost of the boresight facility becomes
negligible
4.0 Other Defining Criteria
4.1 Antenna Size and Power Requirements
The RADARSAT space-ground telemetry data rate of 105
megabits/second, plus the orbital altitude of approximately 750
km, determines the general antenna size and associated
electromechanical tracking mechanisms. The proposed ground
station antenna system and support electronics are provided by
NASA, Wallops Flight Facility Code 800, via a contract with
Scientific Atlanta of Atlanta, Georgia.
A 10 meter diameter antenna represents a practical and
reasonable engineering choice for the RADARSAT mission and the
typical satellite tracking operations that the facility may be
desired for in the future. The tracking of low earth orbit polar
satellites requires the antenna to have the capability to slew at
high rates when tracking a satellite that passes near zenith.
This creates a large electrical power demand to slew such a
massive antenna at the requisite rate.
NSF/OPP required NASA to consult with Scientific Atlanta to
devise a means to reduce the power demands of the antenna
tracking system during active tracking as much as possible. A
solution devised by Scientific Atlanta was to modify the existing
two motor tracking antenna (elevation and azimuth) by adding a
third motor (elevation tilt). This is a common technique used
for high slew rate tracking systems that can increase performance
(ability to keep up with fast moving targets) and to decrease
power demands. This is accomplished by using the third motor,
which operates at low rate, to induce a tilt in elevation to
reduce the rate at which the elevation motor has to turn. The
net effect is a reduction in the power consumed by the tracking
system.
4.2 Unattended Operation of the Remote Facility
A main operations criterion of NSF/OPP was the ability to
operate the remote facilities from within the confines of the
McMurdo urban area for the routine day-to-day activities that are
human interaction intensive. To respond to this requirement,
NASA directed Scientific Atlanta to modify the existing earth
station systems to be provided such that full computer control of
satellite tracking, operations scheduling, pre-pass calibration,
and data recording would be possible remotely. This has lead to
a design such that the control computer can be interfaced to the
McMurdo Internet computer network link to the outside world, and
a technician can actually access the McMurdo tracking computer
from the United States to assist in maintenance and
troubleshooting.
The provision of the remote control of the tracking facility
has not only produced a safer operation, it has also enabled the
total number of on-site operations/maintenance personnel
recommended by NASA to be reduced from 5 to 3.
4.3 Construction Techniques
The design of the remote electronics support facility was
under the cognizance of NSF/OPP and its prime contractor, ASA.
The general design and construction philosophy taken for this
structure was that of prefabricating the building in the U.S. and
having the building constructed into modular sections that would
permit a rapid erection of the structure with a minimum of on-
site construction activities (when contrasted to the effort
expended for a typical building constructed on-site from raw
materials, the so-called "stick-built" building). This technique
minimizes the number of construction tradesmen needed for the
construction and completion of the facility, and it minimizes the
time required, and thus local environmental impact.