FS-2001-9-025-GSFC New Series of Tracking and Data Relay Satellites Replenishing The Original Fleet NASA's next generation Tracking and Data 2002, and the third, TDRS-J, is scheduled to Relay Satellites (TDRS) consist of three en- launch sometime during the fourth quarter of hanced satellites that provide vital communi- 2002. The new trio of satellites will complement cation links with astronauts aboard the Space the original TDRS constellation of six satellites, Shuttle and International Space Station, as well which has served the world-wide scientific as enable the transfer of data from numerous community and other organizations since Earth and space science missions. 1983. The first in this trio, TDRS-H, launched from Similar to many other communications sat- Cape Canaveral Air Force Station, Fla. in June ellites, TDRS-H,I and J are placed into a geo- 2000, the second, TDRS-I, launched in March synchronous orbit 22,300 miles above the Artist concept of TDRS-H spacecraft on orbit. equator. Each satellite maintains a fixed - Upgraded to 3 megabits per second position above the Earth, tracking fast moving (nearly equivalent to S-band Single Access satellites to provide nearly continuous commu- capability) versus 100 kilobits per second re- nication links with controllers and researchers turn on the original TDRS fleet, and up to 300 on the ground. kilobits per second forward. Ku-Band Single Access: Satellite Capabilities - Operates at frequencies between 13.7 TDRS-H,I and J provides users with the fol- gigaHertz for forward service and 15.0 lowing services - gigaHertz for return service. Provides higher bandwidth for user satellites with data rates up S-Band Single Access : to 300 megabits per second return, which is 5,000 times faster than the standard 56K home - Provides continuous forward and return computer modem, and 25 megabits per second services to individual users in each orbit and at forward; fixed locations; - Supports high-data rate telemetry and high - Supports two-way communication during resolution digital television for Space Shuttle user satellite data recorder playbacks, or full- and, once equipped, International Space Sta- time high-rate service to high-priority users tion video communications. (Space Station such as the Space Shuttle and International video is currently downlinked through Ku-band Space Station; single access, and will soon be upgraded to provide digital capability.) - Tunable over a range of frequencies, in- cluding Multiple Access; - Efficiently transfers enormous volumes of data from tape or solid-state data recorders - Can provide high gain support to a Multiple aboard NASA scientific spacecraft. Access user satellite with degraded communi- cations, or temporaily provide an increased Ka-Band Single Access: data rate; - Features a new higher-frequency - Provides near full-time coverage for servicethat provides the capability to increase scheduled users within NASA's Space Net- data rates to 800* megabits per second for work. future missions with higher bandwidth commu- nication needs, such as multi-spectral instru- S-Band Multiple Access: ments for Earth science applications. (*Rates above 300 megabits per second require addi- - Supplies five simultaneous Multiple Ac- tional ground station modifications.) cess return channels (user satellite to ground) and one Multiple Access forward channel - Establishes international compatibility (ground to user); with Japanese and European space relay pro- grams, allowing for mutual support in emer- - Features return services that use a com- gency situations; mon (2287.5 megaHertz) with code division multiple access to avoid common channel in- - Provides high bandwidth, less interference terference; with terrestrial communications, and lower user 2 satellite equipment burden. ellite System, or TDRSS, consists of the following components: Satellite Navigation - In addition to telemetry, command and mission data communications - TDRS 1-7 satellites, built by TRW of services, the TDRS system will continue to pro- Redondo Beach, Calif.); vide user navigational data needed to locate the orbit and position of user satellites. - TDRS-8, previously designated TDRS-H, and launched in June 2000; New Antenna Design - NASA's White Sands Complex in New Mexico; Two mechanically steered 15-foot diameter antenna reflectors provide high data - A ground terminal extension on the island rate communications and tracking services to of Guam, South Pacific; and user satellites. - Various customer scheduling and data An innovation called 'active' tuningenbles handling facilities. the shape of the single-access reflectors to be adjusted on orbit to correct residual contour dis- (Note: TDRS-I is currently undergoing pre-ac- tortion, which can be occur during stowage ceptance testing.) within the launch vehicle's fairing. The new feature provides an antenna surface accu- racy 15 times greater than that used for the L- band MSAT mobile satellite program. New Acquisition Approaches The new trio of satellites was developed for NASA under a fixed price contract with Boeing Satellite Systems (Boeing Integrated Defense Systems) of El Segundo, Calif. An innovative approach substituted higher-level perfor- mance specifications in lieu of detailed technical design specifications, allowing the contractor to use commercial practices in de- veloping TDRS-H, I, and J. The contract also includes a payback provi- sion, which protects NASA's interests should service failures occur during the first eight years of each spacecraft's 11-year design lifetime. Upper Left: TDRS-H,I,J shown in the stowed configuration for launch. Lower Right: TDRS-H,I,J shown on-orbit and Tracking and Data Relay System fully deployed. The current Tracking and Data Relay Sat- (Images courtesy of Boeing Satellite Systems) 3 From their geosynchronous location 22,300 vices provide a vital communication and video miles above the equator, TDRS-H, I and J links, supporting ongoing research at the South provide nearly continuous contact with lower Pole. In 2002, TDRS-1 supported the first orbiting satellites. telemedicine link for surgery at the South Pole, drastically improving medical services to re- The Space Network Project at NASA searchers stationed in Antarctica. Goddard Space Flight Center, Greenbelt, Md. manages the daily operations of each on-orbit NASA’s Mission TDRS. With their advanced capacity for relaying In addition to the Tracking and Data Relay vital data back and forth from space to users on System's outstanding success in improving the ground, the Tracking and Data Relay Satel- space flight communications, other far reach- lite System is enabling NASA to meet its mis- ing achievements include: sion... Flight Operations - Replacing an exten- To understand and protect our home planet, sive and costly ground-based tracking system, To explore the Universe and search for life, which relied on foreign sites, numerous person- To inspire the next generation of explorers nel, tracking vessels and aircraft, and provided . . . as only NASA can users less than 15 percent contact per orbit. * By providing a communications back- Multiple Users - Pioneered simultaneous bone, which supports current and future scien- support to multiple space users by sharing tific and engineering research on the Space space and ground assets, and employing ad- Shuttle and International Space Station, en- vanced communications technologies and abling researchers access to real-time science scheduling operations. results; Innovative acquisition - Being a trailblazer * By supporting an array of sophisticated of commercial/government dual use of space- Earth science satellites which, for the first time, craft, of lease and purchase procurement, and are allowing scientists to understand the total of hosting a commercial communications pack- Earth system and effects of natural and human- age. induced changes on the global environment. Launch Operations - A unique capability * By relaying data back from observatories to track launches anywhere on Earth, and pro- such as the Hubble Space Telescope and viding increased user support for new and ad- Chandra X-Ray Telescope, providing scien- vanced expendable launch vehicles while tists with insight about the evolution and pos- helping to lower cost. sible future of the universe. Communications Research - Successful test platform for many research efforts, such as Mission Website radio-frequency propagation, very long-base interferometry, digital radio broadcasting, For more information about this advanced telemedicine and aircraft satellite communica- trio of satellites, go to: tions. http://tdrs.gsfc.nasa.gov/Tdrsproject/ Remote Support - Remaining TDRS-1ser- 4 September 2001 (Updated November2002)