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TDRS-4 , known before launch as TDRS-D , is an American communications satellite which was operated by NASA as part of the Tracking and Data Relay Satellite System from 1989 until 2011 .
 American, NASA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 American, NASA