Another photo by Esther Dyson taken on April 9, 2007 in Russia during the Soyuz space flight of Charles Simonyi. One should really click over to Esther's photo on Flickr where she has posted notes on the photo explaining what each area of the screen is.
Jüri Kaljundi added this comment to Esther's photo: "Basically there used to be 6 TDRS (tracking and data relay) satellites which can provide "no rest period" communication between the spacecraft and customer (or NASA). Out of the 6 only half should be operational online at any time, while 3 are in backup mode. ISS is one of many customers of the system. TDRSS 2 was destroyed in Challenger accident so satellite no 7 was built. Now I believe generation 2 of TDRSS is operational with 3 additional satellites. "
See Esthr's blog posting for more information.
Nice graphic representation of TDRSS
Wikipedia entries for