Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. The first US spacecraft was Explorer 1 . I carried instrumentation to measure internal and external temperatures, micrometeorite impacts, and an experiment designed by James A. Van Allen to measure the density of electrons and ions in space. Explorer I ceased transmitting on February 28 of that year but remained in orbit until March of 1970.
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