Table Of ContentBRIAN HARVEY
DISCOVERING
THE COSMOS WITH
SMALL SPACECRAFT
The American Explorer Program
Discovering the Cosmos with Small Spacecraft
The American Explorer Program
Brian Harvey
Discovering the
Cosmos with Small
Spacecraft
The American Explorer Program
Brian Harvey
Templeogue
Dublin
Ireland
SPRINGER-PRAXIS BOOKS IN SPACE EXPLORATION
Springer Praxis Books
ISBN 978-3-319-68138-2 ISBN 978-3-319-68140-5 (eBook)
https://doi.org/10.1007/978-3-319-68140-5
Library of Congress Control Number: 2017955838
© Springer International Publishing AG 2018
This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the
material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,
broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage
and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or
hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does
not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective
laws and regulations and therefore free for general use.
The publisher, the authors and the editors are safe to assume that the advice and information in this book are
believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give
a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that
may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and
institutional affiliations.
Cover design: Jim Wilkie
Project Editor: Michael D. Shayler
Printed on acid-free paper
This Springer imprint is published by Springer Nature
The registered company is Springer International Publishing AG
The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland
Contents
Acknowledgements ................................................................................................... vi
Dedication .................................................................................................................. vii
About the Author....................................................................................................... viii
Author’s Introduction ............................................................................................... ix
1 Foundations ......................................................................................................... 1
2 Early Explorers ................................................................................................... 51
3 Explorer and the Crisis in Space Science.......................................................... 138
4 Faster, Better, Cheaper? ..................................................................................... 174
5 Future Missions and Conclusions ...................................................................... 254
Bibliographical Note ................................................................................................. 271
Appendix 1: List of Explorer Missions ................................................................... 273
Index ........................................................................................................................... 276
v
Acknowledgements
I wish to thank all those who assisted with the provision of information, photographs,
articles, ideas and suggestions, especially Dave Shayler; Bert Vis; Gurbir Singh; Dr Nathan
Schwadron, University of New Hampshire; William Barry (NASA); and Suzanne Parry,
Mary Todd and Ben Jones of the British Interplanetary Society (BIS) for use of the library
and photographs.
Photographs are courtesy of NASA unless otherwise stated.
vi
To
Judith, Valerie, Alistair and Charlie
About the Author
Brian Harvey is a writer and broadcaster on space flight who lives in Dublin, Ireland. He
has a degree in history and political science from Dublin University (Trinity College) and
a MA from University College Dublin. His first book was Race into space – the Soviet
space programme (Ellis Horwood, 1988), followed by further books on the Russian,
Chinese, European, Indian and Japanese space programmes. His books and chapters have
been translated into Russian, Chinese and Korean.
viii
Author’s Introduction
Explorer 1 was the first American satellite to reach orbit, on 31st January 1958, salvaging
American space pride after the first two Soviet Sputniks had orbited the Earth the previous
year. Explorer 1 also achieved a significant scientific result, as its instruments enabled
James Van Allen to present the case that Earth was circled by radiation belts.
What is less well known is that the Explorer program, in its various forms, continues to
the present day, making it the world’s longest continually running program of scientific
space exploration. Explorers have been the principal instrument for unmanned American
space discovery in near Earth orbit (although four also reached the Moon). Up to the pres-
ent time (2017), 94 Explorer-class satellites have been launched and more are promised
for the coming years. The importance of the humble Explorer program may have been
overlooked, thanks to high-profile, large scientific missions (Hubble, for example) and by
extraordinary American successes with planetary probes right across the solar system, but
so far, no one has chronicled this series, its scientific results over six decades and the value
of such small spacecraft as instruments of scientific discovery. This book, Discovering the
cosmos with small spacecraft – the American Explorer program, is designed to mark the
60th anniversary of Explorer 1 (2018).
The core of the book is a description of the Explorer missions to date: their purpose,
mission, instruments, results and discoveries. This is set in the broader context of the infra-
structure built up around the missions (such as the Goddard Space Flight Center), ground
control, management, operations, dissemination, methods and launchers used, from the
large Deltas to the diminutive Pegasus. It will also look at the politics of space science, the
priority given to that discipline and, within that, this form of exploration by small space-
craft. At one stage, for example, missions in the Explorer program got bigger in size but
fewer in number (there was only one mission between 1982 and 1988) and the series
almost died out, only to rediscover its true vocation in the period of ‘faster, better, cheaper’
during the 1990s.
Dividing the Explorer program into distinct phases in a manner that was manageable
for the reader was a challenge and there was no perfect way by which this could be done.
The American space program as a whole has a number of natural dividing lines: the
ix
x Author’s Introduction
establishment of the space program as a reaction to Soviet achievements (1950s); the
heroic period of the 1960s, culminating in the landing on the Moon; the radical revision of
the program under the Nixon presidency, associated with the introduction of the Shuttle
(1970s); reconsideration in the late 1980s following the Challenger accident; and the cur-
rent period of the space station, commercialization and robotic conquest of the solar sys-
tem (2000s onwards). This book broadly follows these natural dividing lines.
Accordingly, Chapter 1, Foundations, outlines the establishment of Explorer, set against
the creation of NASA and the field centre most associated with Explorer, the Goddard
Space Flight Center. The extensive Chapter 2, Early Explorers, outlines the heyday of the
early Explorer program, with its numerous subsets for aeronomy, astronomy, meteorites
and so on, whose natural course ran to Explorer 55 in the mid-1970s. Chapter 3, Explorer
and the crisis in space science, outlines the most difficult period of the program from the
mid-1970s to the 1990s, in which there were few missions (only eleven) and which is now
regarded as having been a period of crisis in space science. Chapter 4, Faster, better,
cheaper? examines the recovery of the program with new approaches and rules, one of
which has led to extraordinary scientific outcomes, starting with SAMPEX. Chapter 5,
Future missions and conclusions, looks at new missions in prospect, looks back over the
program and provides conclusions.
Nomenclature
How to best identify and name spacecraft has been a problem in virtually all the world’s
space programs. Unlike its Soviet equivalent, the Cosmos program, Explorer was never
originally designed as a stand-alone program of small scientific spacecraft. The term
‘Explorer’ was given to it only once the first was in orbit and was the quickly-made choice
of the incumbent President. Explorer was one of two rival programs – the other being
Vanguard – to get a satellite into orbit for the United States, with what is now known as
Explorer being run by the army while Vanguard was associated with the navy. The first five
Explorers were all army projects and it was not until NASA was established that Explorer
began to emerge as the scientific program it later became, starting with Explorer 6. Early
Explorers were given ‘S’ designations (‘S’ for ‘scientific’), normally with a number;
indeed, this was long the designator of choice in the Goddard Space Flight Center and, to
complicate things, might be followed by ‘a’, ‘b’ or ‘c’ designators which might be upper
or lower case.
Not long afterwards, various subsets within the Explorer program acquired specific
designations according to their role, such as ‘Atmospheric Explorer’ (AE) or ‘Beacon
Explorer’ (BE) and these are used here alongside the numerical title. The ‘Interplanetary
Monitoring Platforms’ (IMP), which had their own alphanumeric identifications (A, B, C
etc) were also Explorers and there was a period of overlap between the ‘S’ series and these
subsets. To complicate things further, there were a number of intrusions into the program
by individual, well-established satellites that came from other institutions (University of
Iowa, Naval Research Laboratory) but which acquired Explorer status (Injun, Solrad).
From the 1990s, the subsets were re-invented according to size and scope, such as SMEX
(Small Explorer), MIDEX (Mid-sized Explorer) and UNEX (‘University Explorers’).
