This paper was first published in the Journal in 1963 (Vol. 16, p. 9). It is followed by comments from Brian Kendal.The Transit satellite navigation system, scheduled to become operational in the near future, has been publicized sufficiently for its main features to be rather well known. The excellent article by Dr. R. B. Kershner and Dr. R. R. Newton in the April 1962 issue of this Journal provides a particularly thorough description of the system. In the same issue, Dr. H. C. Freiesleben gives a clear summary of the principal alternative solutions to the navigation satellite problem.