Volume 8, Number 5     September/October 2000

Advanced Technologies

Communications Satellite Serves Space Projects

NASA has launched the first of three of the most advanced communications satellites ever designed to replenish the existing on-orbit fleet that has served the space community since 1983. The newest generation Tracking and Data Relay Satellites (TDRS) will provide vital communication links with the Space Shuttle, International Space Station, Hubble Space Telescope and other spacecraft and launch vehicles.

“The average age of the existing fleet is more than 10 years, which is beyond the mission design lifetime,” said Anthony Comberiate, TDRS project manager at NASA Goddard Space Flight Center in Greenbelt, Maryland. “The new series will replenish our existing fleet and allow users to migrate to the new Ka-band,” which will allow a threefold increase in data throughput.

The TDRS-H was launched June 30, 2000, aboard a Lockheed Martin Atlas IIA rocket from Cape Canaveral Air Force Station in Florida. The White Sands, New Mexico, ground terminal is the TDRS operational control center, which also provides customer telecommunications services. NASA plans to launch TDRS-I and TDRS-J in 2002 and 2003, respectively.

 
TDRS-H, with two additional satellites, will serve to replenish the existing on-orbit fleet of communications satellites. The three satellites are the most advanced communications satellites ever developed.

The TDRS-H spacecraft, having reached its geosynchronous on-orbit testing location of 150° West longitude, has assumed the operational name of TDRS-8. Maintaining its fixed position 22,300 miles above the Earth, TDRS-8 will provide nearly continuous communication links with controllers and researchers on the ground. After testing and acceptance of the spacecraft, TDRS-8 will be moved to its operational location of 171° West longitude. TDRS-8, when placed into operation, will relay enormous volumes of user data-voice, television and science-from various orbiting scientific and manned missions to ground control centers. The spacecraft also will track user satellites, determining their exact location in space.

TDRS-8 features the following new and improved services:

• S-band Single Access: Two 15-foot diameter steerable antennas used at the 2.0 to 2.3 GHz (gigahertz) band will supply robust communications to user satellites with smaller antennas and receive telemetry and range-safety data from expendable rockets during launch.

• Ku-band Single Access: The same two large antennas, operating at 13.7 to 15.0 GHz, will provide high data-rate support to the International Space Station with high-resolution digital television, and will dump large volumes of data at rates up to 300 Mbps (megabits per second). This rate is more than 5,000 times faster than the standard 56K (56 kilobytes per second) home-computer modem.

• Ka-band Single Access: A new higher-frequency (22.5 to 27.5 GHz) service that increases data rate capabilities to 800 Mbps will provide communications with missions like the International Space Station and future multi-spectral instruments for Earth science applications.

• Multiple Access: Using a phased array antenna and operating in the 2.0 to 2.3 GHz range, the system receives and relays data simultaneously from five lower data-rate users and transmits commands to a single user.

Hughes Space and Communications of El Segundo, California, designed, built and tested the spacecraft under a fixed-price agreement with NASA. By specifying performance requirements, the new approach allowed the contractor to custom-design a spacecraft that met NASA's needs. Because it was allowed more latitude to use commercial practices, Hughes was able to reduce the costs associated with such a venture.

The Space Network Project at Goddard will manage TDRS-8 operations through NASA’s Consolidated Space Operations contract.

More information about the TDRS-H, -I and -J spacecraft can be found at http://tdrs.gsfc.nasa.gov/tdrsproject/ or contact Marco Toral 301/286-9861 Marco.A.Toral.1@gsfc.nasa.gov

For more information about how to become a space network user, refer to http://nmsp.gsfc.nasa.gov/tdrss or contact Jon Walker 301/286-7795 Jon.Z.Walker.1@gsfc.nasa.gov Please mention you read about it in Innovation.


 

ACTS Experiments Come to an End

After 81 months of operations, far exceeding its planned 24-month mission, NASA’s Advanced Communications Technology Satellite (ACTS) concluded its extensive experiments program at the end of May 2000.

Launched in September 1993 as a partnership among NASA, industry and academia, ACTS opened the door for U.S. satellite communications technology in demonstrating the use of the high frequency Ka-band (30/20 GHz). Until ACTS, this frequency was virtually unused-the majority of communication satellites used lower frequency bands called C- and Ku-bands. Exploring Ka-band technology was designed to relieve orbital crowding and demonstrate the first band of frequency wide enough to carry simultaneous services ranging from multiple voice, video and data communications to computer connections at optical fiber data rates.

 
ACTS opened the door for U.S. satellite communications technology in demonstrating the use of high-frequency Ka-band. Exploring Ka-band technology was designed to ease orbital overcrowding. (Illustration provided by NASA Glenn Research Center.)

“The ACTS Experiments Program has been an outstanding research and development achievement that resulted in a unique operational capability for the center and the agency,” said Donald J. Campbell, NASA Glenn Research Center director. “It was a bold step to put a new communication satellite into operation with minimal support, and based on program results, it was the right decision because it laid the foundation for advancements in communication satellites.”

Throughout its lifetime, ACTS, which was managed by the NASA Glenn Research Center in Cleveland, Ohio, opened new frontiers by utilizing a unique hopping spot beam antenna system that generated 51 tightly focused signal beams. Each spot beam typically had a diameter of 150-200 miles and was able to “hop” from one location to the next, covering up to 40 locations in a millisecond. Concentrating satellite power in such a way permitted significantly smaller and less expensive Earth stations. In addition, the spot beam was better able to penetrate through rain and mitigate rain fade.

“The ACTS Experiments Program had the foresight to step beyond the conventional thinking and prove the technology needed for the future, as well as the present,” said Joseph H. Rothenberg, NASA associate administrator for space flight. The ACTS Experiments Program has achieved remarkable milestones with 103 experiments and numerous demonstrations involving more than 200 diverse partners, paving the way for the next generation of communications satellites. The experiments program succeeded in areas as diverse as advanced networking, medicine, education, defense, emergency response, maritime and aeronautical mobile communications, science and astronomy.

ACTS set the standard for next generation communications satellites. Its pioneering advanced technologies for space communications have shown the feasibility of the next generation communication satellites to meet ever-growing communications needs. Its successes have been recognized through numerous awards, including induction into the U.S. Space Foundation’s Space Technology Hall of Fame in 1997, an R&D 100 Award in Significant Technology in 1995 and the prestigious Federal Technology Leadership Award in 1995.

For more information on the ACTS Program, please visit: http://acts.grc.nasa.gov, or contact Robert Bauer, NASA Glenn Research Center 216/433-3431 Robert.A.Bauer@lerc.nasa.gov Please mention you read about it inInnovation.

 



NASA Official: Jonathan Root

Web Designer: Shawn Flowers

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