text: Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
  ### Context:
  CREATE TABLE table_148578_1 (explosion VARCHAR, altitude__km_ VARCHAR)
  ### Question:
  What explosion had an altitude of 539 km?
  ### Answer:
  SELECT explosion FROM table_148578_1 WHERE altitude__km_ = "539"