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Case
Stories
ITT Advanced Engineering & Sciences Provides NASA
with Research & Technologies to Expand the Reach of Space
Communications
ITT
Advanced Engineering & Sciences is leveraging its heritage in space
communications technology to help NASA expand the range and
efficiency of its space communications capabilities.
Long History of
Engineering Support at NASA Goddard
The
mission of the NASA Goddard Space Flight Center is to expand
knowledge of the earth and its environment, the solar system, and
the universe through observations from space. To accomplish this,
communications to and from spacecraft orbiting the earth is
tremendously important.
Key
to satellite communications for NASA is the TDRSS, the Tracking and
Data Relay Satellite System. The TDRSS geosynchronous orbiting
satellites relay information from low orbiting manned space vehicles
and experimental satellites. With the TDRSS system, low orbiting
satellites can be seen from anywhere on earth and thus can
communicate from any place in their orbit.
AES
has a long history of providing engineering support to NASA Goddard
for TDRSS. According to Lenny Schuchman, Vice President & General
Manager of the Communications Systems Integration Business Unit at
AES, "AES personnel have been dedicated to NASA Goddard's mission in
communications for over 25 years." AES has provided significant
contributions to the initial specifications of TDRSS and to the
design of improved upgrades. AES also works to ensure compatibility
between user spacecraft and TDRSS, to ensure that NASA's allocated
bandwidth is optimally used, to plan the next-generation TDRSS, and
to develop technology which provides new, lower cost services for
TDRSS.
Systems Engineering
For
over 25 years, AES has provided a full range of RF communications
systems engineering support to NASA Goddard related to the TDRSS and
other NASA Space and Ground Network assets. This support encompasses
requirement assessment, architectural trade studies, communications
technology studies, conceptual designs, specification development
and procurement support, and communications performance analyses.
AES
has played key system engineering roles in a number of major
programs at NASA including the TDRSS H, I, J program. This program
will procure three, new next-generation TDRSS spacecraft to meet
NASA track and data relay needs to 2010 and beyond. AES reliability
analyses of the existing TDRSS spacecraft constellation, in
conjunction with user mission modeling were used to determine the
earliest need dates, required launch dates, and number of required
spacecraft to replace the aging fleet. AES performed feasibility and
architecture studies, and then developed the spacecraft
telecommunications requirement specification and in-house cost
estimate for the NASA procurement. Since the award of the spacecraft
contract by NASA, AES continued to support NASA on the TDRSS H, I, J
program by providing oversight of the implementation contractor to
ensure all telecommunications requirements are met.
On a
similar task for NASA, AES supported the procurement and
implementation of the Second TDRSS Ground Terminal (STGT) at White
Sands, NM. AES initially performed studies to define the STGT system
and subsystem architectures, particularly taking into account the
lessons learned from the current White Sands Ground Terminal
operations and current state-of-the-art technologies.
To
support these and other NASA system engineering activities, AES has
designed and developed a large number of software tools now serving
the telecommunications and spectrum engineering communities. With
over 100 analysis and simulation packages (in software form)
operating in a workstation or PC environment, AES is capable of
analyzing all aspects of RF communications. These tools are used to
ensure user spacecraft design and performance compatibility with the
Space Network and/or Ground Network, and to assess, via modeling and
simulation, performance and risks associated with advanced
technology applications.
Spectrum Management
AES
fulfills spectrum management roles and performs communications and
spectrum analyses in support of the NASA Spectrum Managers. AES
plays a critical role in ensuring that quality RF spectrum is
available to NASA missions.
As
part of the spectrum management efforts, AES has performed analyses
on a variety of space communications topics including radio
frequency interference, frequency sharing, power spectral densities,
geographical distribution of interference, technology risk
assessment, and visibility and network coverage. Much of these
analyses are performed in direct support of the NASA Spectrum
Manager or in support of U.S. contributions to national and
international spectral policy conferences, study groups, and task
groups.
The
AES team works closely with NASA project offices in frequency
selection and management, spacecraft design, mission planning,
networks scheduling, and post-mission error analysis in order to
optimize RF performance and avoid data loss or degradation of the
communications links due to interference.
The
AES team uses in-house tools to analyze various types of spectral
interference.
Technology Development
In
the mid-1980's Dr. Aaron Weinberg, AES Vice President of
Communication Systems hypothesized that by using charge coupled
devices (CCD) for communication, acquisition time for the TDRSS
multiple access service could be reduced from minutes to seconds.
The CCD transceiver technology triggered new operational concepts
and further technology development. As an example, new NASA services
could be provided that allowed experimental satellites to transmit
data "on demand" rather than on a scheduled basis. The CCD
transceiver also had the ability to be reprogrammed.
Building on this "software receiver" technology with Field
Programmable Gate Arrays (FPGA), AES is now realizing small size,
low power and affordable transceivers for use in space applications.
In recent years, AES has been focused on supporting NASA in
developing demand access and is developing a Low Power Transceiver (LPT),
which, when implemented, will demonstrate that new technology can
significantly reduce the cost of communicating via the TDRSS.
Expanding Space Communications
with TechSat 21
AES
is currently working with the Air Force Research Laboratory for
flight testing on a new program called TechSat 21 (Technology
Satellite of the 21st Century). A new way to perform missions from
space is the concept of microsatellite clusters that operate
cooperatively to perform the function of a larger, single satellite.
Each smaller satellite communicates with the others and shares
processing, communications, and payload or mission functions to form
a "virtual satellite".
The
key to the TechSat 21 concept requires the microsatellites to
perform "formation flying". AES will perform research for TechSat 21
that will require testing advanced communications between satellites
to maintain the distance needed for formation flying. Schuchman
notes that, "This will require using a phased array antenna, a need
to do beam forming, multiple transmitters, multiple receivers, as
well as GPS navigation."
In
order to meet the weight and power requirements of these
microsatellies, AES engineers are currently working on a
miniaturized version of the LPT. Called the Miniature Terminal
(MIN-T), it will measure approximately 2-inches square. Schuchman
observes that, "We originally designed the LPT and the MIN-T for
spacecraft that communicate with the TDRSS. Now we see that they
have applications for any spacecraft program whether it connects
into TDRSS or not. The goal is to set up very effective
communications to allow the world of space to communicate with
earth. That includes low power receivers that allow for the multiple
access techniques and reconfiguration of a spacecraft's navigation
and communications without having to take it down."
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