CREATE TABLE table_19621 ("Explosion" TEXT, "Location" TEXT, "Date" TEXT, "Yield  ( approximate ) " TEXT, "Altitude  ( km ) " TEXT, "Nation of Origin" TEXT)

What was the altitude of the event on 1962-07-09?
SELECT "Altitude (km)" FROM table_19621 WHERE "Date" = '1962-07-09'
SELECT "Altitude (km)" FROM "table_19621" WHERE "Date" = '1962-07-09'