In pensione il primo "satellite dei satelliti" della NASA

Dopo più di un quarto di secolo di onorata carriera chiude la sua esistenza spaziale il satellite TDRS-1 o -A, un satellite molto speciale. Fin dalla sua iniziale messa in orbita dalla stiva dello Shuttle, nel 1983, il Tracking and Data Relay Satellite ha fatto da ponte tra la rete di rilevamento terrestre della NASA e una quantità infinita di altri satelliti e missioni spaziali, fornendo inoltre un prezioso supporto per il collegamento dei punti sulla terra che non possono stabilire connessioni dirette neppure attraverso i satelliti in orbita bassa, come i due poli geografici. Il geostazionario TDSR-1 è stato anche il primo satellite interconnesso a Internet.

A 27 anni di distanza non è più il solo. Il sistema TDRS consiste infatti in una decina di satelliti (per la verità il decimo è andato distrutto nel disastro del Challenger) e altri due se ne aggiungeranno entro il 2013. Considerata la messa in pensione del TDRS-1, in quell'anno si arriverà a una flotta di dieci.

Sulle comunicazioni in banda S, KA e KU rese possibili da questo network di ripetitori orbitali trovate una miriade di siti. E' opportuno partire da quello dedicato al 25esimo anniversario (2008) del TDRS-1 ma soprattutto dal bellissimo libro "Read you loud and clear" scritto per l'occasione da Sunny Tsiao. Una demo dell'interazione tra questi satelliti e la ground network della NASA si trova qui (richiesta l'applicazione di simulazione 3d Celestia). Altri siti offrono un quadro generale dei programmi di comunicazione spaziale e un dettaglio sul sistema geostazionario cui appartiene il TDRS-1, mentre questo è un sommario delle capacità di comunicazione:

S-Band Single Access - Full-time cover- age (except for a 10-minute gap per orbit over the Indian Ocean) provided by two 15- foot diameter steerable antennas used at the 2.0 to 2.3 GHz band supplies robust communications to user satellites with a smaller antenna, and receives telemetry data from expendable launch vehicles during launch.

Ku-Band Single Access - The same two large antennas, operating between 13.7 to 15.0 GHz, provide high data-rate support to the International Space Station with high- resolution digital television. The Ku-band also can dump huge volumes of data at rates up to 300 megabits per second (Mbps)

Ka-Band Single Access - This new higher-frequency (22.5 to 27.5 GHz) service increases data rate capabilities to 800 Mbps to provide communications with future missions requiring higher bandwidth communications such as 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 datarate users and transmits commands to a single user.

Satellite Navigation - In addition to equipment located at the White Sands Complex in New Mexico, the system continues to provide user navigational data required to locate the orbit and position of NASA user satellites.

Ecco infine il comunicato sulla decommissionamento del Tracking and Data Relay Satellite numero 1, classe aprile 1983 e spento ufficialmente domenica 27 giugno 2010.

NASA RETIRES FIRST DATA RELAY SATELLITE AFTER STELLAR CAREER

WASHINGTON -- After a long and successful career providing communications support, NASA's groundbreaking Tracking and Data Relay Satellite (TDRS) 1 is retiring.

On Sunday, June 27, NASA will shut down the satellite that launched into orbit during space shuttle Challenger's maiden voyage (STS-6) in April 1983. From 1983 to 1998, TDRS-1 provided NASA with the ability to communicate with other satellites in orbit. NASA reassigned TDRS-1 in 1998 to support the National Science Foundation's (NSF) U.S. Antarctic Program and others on scientific, educational and operational endeavors.

TDRS-1 worked with eight additional satellites to relay data and communications from more than 15 customers, including the NSF, the Hubble Space Telescope, the shuttle and the International Space Station. The TDRS system provides the capability not only to send commands and receive data, but also to navigate and talk with crews in orbit.

"TDRS-1 paved the way for this incredible space communications system," said Bill Gerstenmaier, associate administrator for NASA's Space Operations Mission Directorate. "The remaining TDRS satellites, and the new satellites that will be online within three years, will carry on these critical capabilities for many NASA missions, including science and human spaceflight."

TDRS-1 was the first satellite used to support launches from NASA's Kennedy Space Center in Florida in the early 1990s, returning real-time telemetry. It eliminated a dead zone over the Indian Ocean where there previously was no communication, providing full coverage for the space shuttle and low-Earth orbiting satellites.

TDRS-1 proved helpful during a 1999 medical emergency at the NSF's Antarctic Amundsen-Scott South Pole Station. The satellite's high-speed Internet connectivity allowed personnel to conduct telemedicine conferences. Doctors in the United States aided Dr. Jerri Nelson, who had breast cancer, in performing a self-biopsy and administering chemotherapy. Later, in 2002, doctors used TDRS-1 to perform another telemedicine conference with the station to assist in knee surgery for a meteorologist.

Because of its orbit, the satellite was able to link the North and South Poles and relayed the first pole-to-pole phone call. TDRS-1 also transmitted the first internet connection and live webcast from the North Pole and supported the first global television event from the South Pole Station - a worldwide television broadcast to commemorate the beginning of the year 2000.

TDRS-1 was instrumental in supporting innovative astronomy and astrophysics research programs at the South Pole Station, including the one-of-a-kind IceCube Neutrino Observatory and the South Pole Radio Telescope. The satellite transmitted gigabytes of science research data to university researchers worldwide on a daily basis.

The first six TDRS satellites were built by TRW Inc. (now Northrop Grumman Corp.). Boeing Space and Intelligence Systems also built three TDRS satellites. NASA plans to launch two additional satellites into the Tracking and Data Relay Satellite System by 2013. On June 13, 2010, the satellite arrived at its final destination, approximately 22,500 miles above the Earth. After the orbit is stabilized and the remaining fuel removed, NASA will shut down the satellite on Sunday, June 27.

http://nssdc.gsfc.nasa.gov/multi/tdrs.html