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A new battery of studies followed as NASA , NORAD and others attempted to better understand the orbital environment , with each adjusting the number of pieces of debris in the critical-mass zone upward .
 NASA, NORAD
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 NASA, NORAD