This book is based on my 50 years of experience in navigation of Earth entry vehicles, Minuteman ballistic missiles, and planetary spacecraft. At the Jet Propulsion
Laboratory, I worked on the Mariner 6, Viking, Pioneer, Galileo, and Near Earth
Asteroid Rendezvous missions. At KinetX Inc. I worked on the MESSENGER
and New Horizons missions. In writing this book I have drawn on engineering
memoranda, conference papers, and publications I have written as well as many
notes that I have accumulated over many years. My purpose is to present a book
that will describe how navigation is done. The emphasis is on mathematics that
have been coded in computer programs used for mission operations. Therefore, the
derivations are given in detail since relatively little mathematics actually makes it
into operational software. The mathematics that do are generally straightforward,
but the programs are large and complex and must be virtually error free. In writing
this book, I have frequently checked the mathematics by looking at computer code
that I am confident is correct.