A Selective History of the Jet Propulsion Laboratory
- James D. BurkeJames D. BurkeNASA, Jet Propulsion Laboratory
- and Erik M. ConwayErik M. ConwayNASA, Jet Propulsion Laboratory
The Jet Propulsion Laboratory (JPL) of the California Institute of Technology had its origins in a student project to develop rocket propulsion in the late 1930s. It attracted funding from the U.S. Army just prior to U.S. entry into World War II and became an Army missile research facility in 1943. Because of its origins as a contractor-operated Army research facility, JPL is the National Aeronautics and Space Administration’s (NASA) only contractor-operated field center. It remains a unit of the California Institute of Technology. In the decades since its founding, the laboratory, first under U.S. Army direction and then as a NASA field center, has grown and evolved into an internationally recognized institution generally seen as a leader in solar system exploration but whose portfolio includes substantial Earth remote sensing.
JPL’s history includes episodes where the course of the laboratory’s development took turning points into new directions. After developing short-range ballistic missiles for the Army, the laboratory embarked on a new career in lunar and planetary exploration through the early 1970s and abandoned its original purpose as a propulsion technology laboratory. It developed the telecommunications infrastructure for planetary exploration too. It diversified into Earth science and astrophysics in the late 1970s and, due to a downturn in funding for planetary exploration, returned to significant amounts of defense work in the 1980s. The end of the Cold War between 1989 and 1991 resulted in a declining NASA budget, but support for planetary exploration actually improved within NASA management—as long as that exploration could be done more cheaply. This resulted in what is known as the “Faster Better Cheaper” period in NASA history. For JPL, this ended in 2000, succeeded by a return to more rigorous technical standards and increased costs.
The Missile Years
The Jet Propulsion Laboratory (JPL) traces its origins to a set of rocket motor experiments conducted by students in the Arroyo Seco, a desert wash in Pasadena, California. Some, though not all, of the students were in Caltech’s Guggenheim Aeronautical Laboratory (GALCIT), advised by its director, Theodore von Karman. These experiments led to the development of rocket-assisted take-off for airplanes. Both liquid and solid rockets were tested, and when the United States entered World War II and production funding began to flow, GALCIT’s rocket project split. Caltech’s leader did not want GALCIT to become a production facility, so the production effort was spun off into a private company, Aerojet. The research effort, set up as a Caltech-operated Army facility, became JPL (Koppes, 1982). The laboratory’s transition from jet-assisted take-off rockets to guided missiles was fostered by the U.S. discovery of the German V-2 rockets. JPL’s first liquid-fueled missile was the WAC Corporal, a demonstration vehicle that led to a 75-mile-range missile called Corporal. In 1949, a WAC Corporal, mounted on a V-2 in a configuration known as a “Bumper WAC,” achieved an altitude of more than 300 km.
The full-size Corporal was the subject of JPL’s first large-scale development project, with dozens of flights at the Army’s White Sands Proving Ground followed by conversion into a rather clumsy Army missile system. The liquid-fueled Corporal’s recognized shortcomings led to the development of the Sergeant missile system, intended from the outset to be a fieldworthy weapon. Corporal’s liquid propulsion was replaced by solid fuel and its radio guidance by inertial. The Army deployed several battalions of Sergeant missile units starting in 1963 and retired the weapons system in 1977 (Koppes, 1982, pp. 30–77).
The transition from Corporal to Sergeant during the 1950s was a turning point for JPL. It brought about the change from rocket research to the growth of what is now known as large-scale systems engineering and management, the founding skills for most of what has followed at JPL and in the space industry (Johnson, 2002, pp. 81–114).
Joining the Space Race
JPL’s collaboration with the Von Braun team began when the Germans were first domiciled at Fort Bliss near El Paso, Texas, launching V-2s as sounding rockets (DeVorkin, 1992; Koppes, 1982, pp. 40–42). When the team moved to Huntsville, Alabama, and set up the Army Ballistic Missile Agency (ABMA), a project was started for testing missile re-entry bodies using modified Redstone missiles with upper stages made of clusters of scale-model Sergeant rocket motors, a combination capable of launching a small Earth satellite. The Army proposed doing exactly that for the International Geophysical Year (IGY), an 18-month period starting in 1957, but a U.S. government decision awarded that task to a coalition effort based on the Navy’s Viking rocket to build a vehicle called Vanguard. The Army’s re-entry vehicle test program went ahead anyway and made three suborbital flights in 1956 and 1957 (Koppes, 1982, pp. 80–82).
Soviet scientists had announced that the USSR would also launch satellites during the IGY, but this did not attract much attention until, on October 7, 1957, a modified Soviet intercontinental ballistic missile launched Sputnik, causing a worldwide upheaval (Divine, 1993; Siddiqi, 2000, pp. 119–170). After a Vanguard failure, permission was ultimately granted for a U.S. Army attempt built largely from spare hardware developed for the re-entry testing program, and on January 31, 1958, the ABMA-JPL team’s Explorer 1 entered orbit (Koppes, 1982, pp. 82–93; McLaughlin Green & Lomask, 1969).
After Sputnik and Explorer 1, the Eisenhower Administration faced a decision whether to allow the nation’s space exploration program to remain within the Defense Department or to place it in a new civilian agency. Eisenhower chose to transform the old National Advisory Committee on Aeronautics into the National Aeronautics and Space Administration (NASA). NASA was launched in October 1958 but without JPL. The laboratory’s leaders quickly sought to leave the Army for NASA too and joined it in January 1959. Those leaders were also faced with deciding what part of the new space age it should adopt as a central set of objectives. The result, clearly a critical turning point in JPL’s history, has shaped the laboratory’s character and reputation, but the actual decision process is not documented. The laboratory chose and advocated a future of lunar and planetary exploration to NASA. While the new agency’s leaders were skeptical that available launch vehicles were up to the task, they ultimately agreed to let the laboratory try (Koppes, 1982, pp. 99–112).
One consequence of the decision to focus on planetary exploration was the JPL’s exit from launcher development. Sending scientific instruments to the Moon and planets would obviously require much larger spacecraft, hence more capable launch services, than had been provided for the Explorers and early Pioneers. It was agreed that the booster would be the U.S. Air Force’s Atlas, so the next question regarded selecting the upper stage.
JPL’s own candidate was called 6K, a rocket stage with storable propellants in spherical tanks mounted in a truss structure. A shortage of test stands slowed the program to the point that the U.S. Air Force’s Agena upper stage, developed initially for the Central Intelligence Agency’s “Corona” reconnaissance satellites, surpassed it. Faced with too many competing designs, NASA chose to adopt the Agena for its own use; thus JPL’s 6K stage was cancelled. But it left a legacy: The hexagonal shape of Rangers and Mariners is due to the plan for matching the 6K truss (Koppes, 1982, p. 105; Wheelon, 1995).
The abandonment of 6K was a major turning point in JPL’s history. After exiting the Sergeant missile program, it ceased to be a developer of large rocket motors. Instead, JPL concentrated on small units for spacecraft midcourse maneuvers and, later, solar-electric, or ion, drive.
Deep Space Networks
To track and receive signals and send commands to far-distant probes in the solar system, the ground station must have a huge antenna of the kind used for radio astronomy, high-powered transmitters, and super-sensitive receivers. Thus it was essential, contemporary with the decision to make lunar and planetary missions JPL’s main goal, to build a deep-space tracking and data acquisition facility. While JPL had established temporary facilities for Explorer 1, its first large antenna, a 26-meter dish in Goldstone, California, was built for its first pair of U.S. lunar missions, Pioneers 4 and 5.
From the start, it was decided that spacecraft contact should be maintained whenever it was physically possible, with the result that Deep Space Network (DSN) stations would be located to cover all longitudes. As a consequence, U.S. intercept facilities, initially known as Deep Space Information Facilities, had to be in the Eastern Hemisphere. In addition to Goldstone, the laboratory built DSN sites in South Africa (later relocated to Spain) and Australia to host the necessary antennae and supporting equipment. Renamed the Deep Space Network in 1963, Deep Space Information Facilities served both U.S. and foreign missions operating beyond Earth orbit (Koppes, 1982, pp. 95–96; Mudgway, 2001; Waff, 1989, 1993). NASA also built a virtual clone of the DSN for the Apollo program known as the Manned Space Network, which became part of DSN when the Apollo program concluded.
Project Ranger began in 1960, when NASA was still working out its internal structure and its management relationships to its field centers, but by the time of Ranger’s last flight in 1965 these had largely been sorted out. Mariner 2, JPL and NASA’s first successful planetary mission in 1962, derived its spacecraft design and some operations concepts from Ranger. What follows is a review of Ranger’s origin and the political background, technical experience, management relationships, and in-flight events that characterized the project and created its legacy (Burke, 1984; Gallantine, 2010; Hall, 1977). At its outset, the project’s priorities were driven by the post-Sputnik urgency of competition with the USSR. (Burke, 1996; Huntress & Marov, 2011).
Deep-space mission planners knew that an October 1960 launch window offered the first chance in human history for a mission to Mars. Briefly studied as a goal for a large spacecraft to be named Mariner A, the prospect of a 1960 mission to Mars was soon abandoned as too ambitious. A smaller craft called Mariner R, derived from Ranger, was chosen for a mission to Venus during the 1962 launch window. Ranger had always been considered a precursor to planetary spacecraft, so it had solar panels and a high-gain antenna, features not necessary for lunar missions but essential for flights beyond the Moon.
On January 20, 1961, U.S. President John F. Kennedy delivered an inaugural address that was almost entirely about a great contest between American values and the dark forces of communism, tyranny, and subversion emanating from the USSR. He said,
In the long history of the world, only a few generations have been granted the role of defending freedom in its hour of maximum danger. I do not shrink from this responsibility—I welcome it. I do not believe that any of us would exchange places with any other people or any other generation. The energy, the faith, the devotion which we bring to this endeavor will light our country and all who serve it—and the glow from that fire can truly light the world.
The nation’s space agency was part of this grand contest.
On February 4 and 12, the Soviets launched two Venus missions. The first spacecraft failed to eject from Earth parking orbit, but the second, Venera 1, succeeded in beginning its interplanetary trip, only to fail later en route.
The seeds of Ranger’s most important conflicts were planted at that time. First, JPL people, accustomed to the largely hands-off management style of Army personnel and their well-established collaboration with von Braun’s team at the Army Ballistic Missile Agency (AMBA), were unprepared for more intrusive management by NASA. The early Ranger program was run by a committee at NASA headquarters, of which one of us (Burke), ostensibly the project manager, was only a member. This lasted into 1961, when NASA defined something close to modern project management practice (Hall, 1977). Second, management relations among the Army, Air Force, and NASA for launch services had yet to be worked out. NASA had to procure launch vehicles via the Air Force, so JPL’s engineers often had trouble acquiring information from their counterparts in the launcher programs. This produced delays and confusion (Hall, 1977, p. 39). It was also unclear in Ranger’s early years who actually had authority over the selection of scientific experiments for the vehicles, JPL or NASA. Burke believed he did but eventually found, to the contrary, NASA assumed the role of choosing experiments that would fly on JPL spacecraft, with the ongoing result that sometimes JPL builds spacecraft on which there are no JPL instruments at all. The most famous case of this was the grand Voyager missions launched in 1977 (see later discussion). But this was not clear when Ranger began.
Two Ranger test spacecraft, launched August 23 and November 18, 1961, were intended to demonstrate Sun and Earth attitude information systems, solar power, and high-gain communications from high-apogee orbits not aimed at the Moon. Because of Agena upper-stage failures, these two spacecraft were stranded in low Earth orbit and unable to return any useful data. Both spacecraft did appear to be fully functional during their brief lives in orbit.
The second group of Ranger spaceraft, known as Ranger Block 2, carried a seismometer capsule that was to be dropped onto the lunar surface during the spacecraft’s approach. None of these three flights was successful. Failure of the fifth flight resulted in a project reorganization. Burke was replaced by Harris “Bud” Schurmeier, and the program’s goals were descoped to lunar imaging. Heat sterilization of the spacecraft, which had been required but always controversial due to the damage done to the spacecraft electronics, was abandoned. JPL’s director, William Pickering, curtailed the relative independence of the laboratory’s technical (or “line”) divisions to aid Schurmeier in getting his project’s work done and implemented a new quality assurance program.
The third group of Rangers, known as Block 3, carried a set of high-resolution television cameras to record their lunar impact. The first of these, Ranger 6, failed again. At staging off of the Atlas booster engines, a hot plasma cloud enveloped the launch vehicle, bridging pins in an Agena umbilical connector and burning out the spacecraft’s two high-powered TV transmitters. Redesigning the umbilical receptacle eliminated the possibility of this failure occurring in future missions.
The Ranger 6 failure earned JPL its first Congressional hearing, ostensibly on the Ranger program but also involving investigation of the NASA-JPL management relationship. It was no secret that JPL’s leaders had not always taken directives from NASA’s leaders well, and the laboratory had rebuffed NASA attempts to install a “general manager” at the lab to supplement its long-time director, William Pickering. After these hearings, the laboratory acceded to the demand and recruited the former general manager of the Atomic Energy Commission (Hall, 1977, pp. 251–154).
Rangers 7, 8, and 9 were completely successful, returning thousands of high-resolution images. They did not, however, satisfy the nation’s young science community. NASA’s chief scientist had tried to force JPL to place eight additional scientific instruments on the Block 3 Rangers in response to criticism that the TV-only payload was not sufficiently scientific but rescinded the requirement as the mission failures mounted.
In 1960, JPL also embarked on a second lunar program called Surveyor. Its goal was to land automated scientific probes on the lunar surface. Unlike Ranger, the Surveyor program was to be accomplished via a systems contract, which was awarded to Hughes Aircraft Company. During its first four years, the contract was administered in a very “hands-off” fashion, with a small management office at JPL and little engineering or contract management support. The project fell far behind schedule, and in 1964 it was overhauled. More than 300 JPL engineers were assigned to work with Hughes engineers, and the NASA program manager, Benjamin Milwitzky, formed an executive management council that included Hughes’ Vice President Allen Puckett to ensure adequate management attention (Koppes, 1982, pp.172–183).
One element of Surveyor’s difficulty was the Centaur upper stage, which was being developed simultaneously. The mass capability of the stage was unknown and constantly in flux, and as a result the Surveyor engineering teams had frequent changes to which they had to adapt. Lower than expected capability from the first few Centaurs meant that the first Surveyor carried only a television camera to the Moon (Dawson & Bowles, 2004). It landed safely on June 2, 1966. Later missions carried additional instruments, including an instrument to determine the strength of the lunar surface for NASA’s Apollo program. Like Ranger, NASA had initially planned to send advanced versions with greater capabilities, including a small rover, but as the NASA budget shrank in the late 1960s, these were all terminated. Ultimately, seven Surveyors were launched, and five successfully completed their science missions.
The Surveyor program taught JPL that it could not rely on a “hands-off” systems contracting mode to deliver successful missions. Its engineers had to be directly involved with contractor engineers when using a systems contractor. This lesson would be discarded for a brief period in the 1990s and later have to be relearned.
Early planning at JPL envisioned a large spacecraft called Mariner A for Mars and Venus. This was soon abandoned as too ambitious for the time and replaced by a craft derived from Ranger, hence named Mariner R, to be launched in the 1962 Venus opportunity.
On October 10 and 14, 1960, the Soviets attempted to launch robotic spacecraft to Mars. Intercepted telemetry showed that those two launch vehicles were by far the most heavily loaded rockets launched to date, and though both failed, they signaled the USSR’s commitment to deep-space exploration and acted as a spur to Mariner (Huntress & Marov, 2011, pp. 87–94).
The Atlas carrying Mariner 1 strayed and was destroyed by Range Safety. Mariner 2, successfully launched, confirmed the hellish conditions at the Venus surface expected from ground observations. Mariner 3 and 4, launched at the 1964 Mars opportunity, were larger spacecraft requiring the increased performance of Atlas-Agena D. In the flight of Mariner 3, the payload shroud failed to separate, causing loss of the mission. Mariner 4 was a seminal mission; providing the first up-close images of Mars, it also destroyed belief in a wet, inhabited planet. Craters were clearly visible, and radio science revealed an atmosphere only 1% as dense as Earth’s (see Koppes, 1982, pp. 128–129, pp. 161–171).
For the 1967 Venus opportunity it was decided to reconfigure the spare 1964 spacecraft, reducing solar panel size and making other changes for survival closer to the Sun. The mission succeeded, arriving at Venus a few days after the Soviet Venera 4 (Koppes, 1982, pp. 128–129).
Launched by Atlas-Centaurs at the 1969 Mars opportunity, Mariner 6 and 7 flew by southern latitudes on Mars, sending images of the ancient cratered surface of the martian highlands, leading to the erroneous opinion that Mars resembled the Moon. Later missions revealed the more northerly regions showing a past influenced by volcanoes and water (Koppes, 1982, pp. 200–202).
The 1971 Mars opportunity brought a new turning point in JPL’s history: Mariner 9, the first planetary orbiter, revolutionized planetary exploration by showing what a comprehensive scientific mission can do to open whole new fields of inquiry. (Mariner 8 had been lost when its Centaur tumbled out of control.) Operating for nearly a year in Mars orbit, Mariner 9 revealed that Mars had been warmer and wetter in its ancient past, presenting a mystery that is still in not resolved today (Ezell & Ezell, 1984, pp. 159–167, 304–305; Koppes, 1982, pp. 218–221).
Obviously eager to achieve success at Mars ahead of the expected American 1975 Vikings, the Soviets launched four spacecraft in 1973. Mars 4, 5, 6, and 7 all reached the planet’s vicinity, but due to various failures their data return was meager (Huntress & Marov, 2011, pp. 233–240).
In February 1974, Mariner Venus Mercury, also known as Mariner 10, used a gravity assist from Venus to reach Mercury, the last of the inner planets to be visited. Mariner 10 performed three flybys of Mercury, imaging about 40–45% of its surface (Koppes, 1982, pp. 221–226; Murray, 1989, pp. 93–123).
The Viking missions to Mars are often mistakenly attributed to JPL, because the mission’s science operations were at JPL and so media gathered there to follow the landings and the science activities. But the project management was assigned to the NASA Langley Research Center, which had JPL build the orbiters (derived from the Mariner 8/9 design) and contracted with Martin Marrietta in Denver to build the complex landers. The Viking landers were the first to use general purpose computers to manage their descents in real time, necessary due partly to the time delay between Earth and Mars and also because of the unpredictability of the martian atmosphere. A simple timed sequencer, the way JPL’s Surveyors and Soviet Mars landers had managed their descents, was deemed unlikely to work. The Viking Orbiters also provided data relay services for the landers, an idea revived two decades later with the Mars Global Surveyor mission.
The Viking mission was oriented toward finding life on Mars, and the landers carried life-detection experiments with sampling arms to dig into the martian surface. The first landing, on July 20, 1976, was delayed by discovery that the original landing site appeared to be too rocky. Using the orbiter imagery, mission scientists gathered at JPL had to find a new site, choosing a spot in western Chryse Planitia. The second lander touched down in Utopia Planitia on September 3, 1976. Both orbiter/lander pairs operated successfully and returned a vast amount of scientific information, including life-detection results that were at first regarded as inconclusive but later deemed negative (Ezell & Ezell, 1984, pp. 398–413).While the mission was still in development, JPL director and planetary scientist Bruce C. Murray (1989, p. 68) had argued that the life detection focus was premature and the results would likely be uninterpretable without first understanding the composition of the surface. His criticism would echo for decades, with future missions oriented directly at understanding Mars’ surface topography and composition, not looking for life. The Viking orbiters mapped the seasonal distribution of water vapor in the atmosphere, finding a pattern that suggested water ice lay near the surface across much of the planet, while, after the excitement over the life detection non-results died down, the landers provided years of data on the martian weather.
In 1965, JPL trajectory analysts noticed that all four of the outer solar system’s giant planets would be accessible to a single spacecraft from a 1977 launch, making possible what quickly became called a “Grand Tour” of the outer solar system. At the same time, JPL was working on a long-life spacecraft design intended for outer planet exploration known as TOPS (thermoelectric outer planet spacecraft). The reworking of TOPS and the Grand Tour eventually became the Voyager mission.
When the Voyager mission was finally approved by NASA in 1973, it was known as the Mariner/Jupiter/Saturn 1977 mission, to reflect a substantial descoping in mission goals. The revamped mission encompassed only Jupiter and Saturn to reduce the program’s cost, but two spacecraft would still be launched. The spacecraft were also simplified and were basically advanced (and enlarged) versions of the Mariner spacecraft design. But the engineering team worked to preserve the vital launch date and the spacecraft’s capabilitiy to carry out the full Grand Tour (Dethloff & Schorn, 2003; Pyne, 2010). One vital improvement made to the design was radiation hardening. This design change stemmed from the Pioneer 10 mission to Jupiter, which returned data showing that Jupiter was surrounded by a radiation field far more intense than expected and had caused the spacecraft computer to malfunction.
Voyager 2 was launched first, on August 20, 1977, on a somewhat slower trajectory than Voyager 1, which was launched two weeks later. Thus Voyager 1 reached Jupiter and Saturn first. The space science community considered the Saturnian moon Titan a scientifically valuable target, so Voyager 1 was targeted to use Saturn’s gravity to make a Titan flyby. This was successful, though little could be seen, it turned out, through Titan’s dense atmosphere. It proved to be composed largely of hydrocarbons, rendering Titan a largely opaque orange ball. Voyager 1’s Titan flyby put it on a path out of the ecliptic and eventually the solar system, so it could not complete the Grand Tour. With a second Titan flyby deemed scientifically pointless, Voyager 2 was reprogrammed to use Saturn’s gravity to complete the Grand Tour by flying past Uranus and Neptune in 1986 and 1989. Completing the Grand Tour required upgrades to the DSN as well as updates to Voyager 2’s software. One technique used was “arraying,” or using multiple antennas to, in effect, create a much larger receiving antenna to increase the received data rate. Both spacecraft were still operating as of this writing.
The Voyager spacecraft made many unexpected discoveries in the outer solar system. They discovered 22 moons and active volcanism on Jupiter’s moon Io. They found a planetary ice sheet on Jupiter’s moon Europa. Voyager 2 found that Uranus’s magnetic field was dramatically misaligned with the planet’s spin axis, and it discovered two Uranian rings. At Neptune, Voyager 2 found a “Great Dark Spot” and previously unknown rings, following the flyby with a close pass over Neptune’s moon Triton. Most spacecraft instruments were deactivated to save power so that the vehicles’ particles and fields instruments could continue to function nearly indefinitely, but Voyager 1’s cameras were reactivated on February 14, 1990, to create a “family portrait” of the solar system seen from 6 billion kilometers from Earth (see Pyne, 2010, pp. 312–315; Sagan, 1994, pp. 1–7). Both spacecraft had passed through the heliopause and entered interstellar space by late 2018.
The Shuttle Era
The development of NASA’s Space Shuttle was supposed to end the use of expendable launch vehicles of the sort used for the planetary missions of the 1960s and 1970s. But the Shuttle’s low Earth orbit only capability meant that planetary missions had to have an additional stage to get them out of Earth orbit once free of the Shuttle’s cargo bay. This was a fraught development. NASA ultimately developed a version of the Centaur upper stage for the Shuttle but, after the Challenger accident of 1986, abandoned it. Instead, a less powerful but safer solid fuel upper stage known as the Inertial Upper Stage propelled the three planetary missions launched by Space Shuttles: the Galileo mission to Jupiter, the European Space Agency’s (ESA) Ulysses solar probe, and the Magellan mission to Venus. After the Challenger accident, President Reagan decided to remove all future planetary missions from the Shuttle program, but these three were far enough along in development that they could not easily be reworked for a traditional, expendable launch vehicle.
Galileo was known initially as Jupiter Orbiter with Probe (JOP) (Melzer, 2007, pp. 32–36; Westwick, 2007, pp. 41–47; Williamson, 1999, pp. 161–193). A JPL-built orbiter was to carry an atmospheric entry probe provided by the NASA Ames Research Center. Originally intended for a 1982 launch, due to delays in the Shuttle program, Galileo was prepared for a 1986 launch and had been shipped to Kennedy Space Center for launch when the Challenger accident happened. It was finally launched by Shuttle Atlantis in 1989 but from that launch year had to be launched toward Venus and use gravity assists from Venus and Earth (twice) to reach Jupiter. During its transit back to Earth, JPL discovered Galileo’s high-gain antenna would not open properly, dramatically reducing the amount of data it could return to Earth. JPL scientists and engineers were able to install data compression and other software changes to mitigate this failure during its flight out to Jupiter. The spacecraft arrived in 1995 and operated until 2003 (Melzer, 2007, pp. 37–70). Galileo’s principal scientific discoveries were about Jupiter’s moons; at least one, Europa, proved to have a shell of water ice with a still liquid ocean beneath (see Melzer, 2007).
Ulysses was originally part of a joint NASA/ESA program known as the International Solar Polar mission. Both JPL and ESA were to build spacecraft for jointly observing the Sun’s poles. Office of Management and Budget officials sought deep cuts to the NASA budget, and at one point, NASA administrator James Beggs threatened to terminate planetary exploration and close JPL (“Beggs to Honorable David A. Stockman,” 2001). While closure of JPL was fought off with the aid of some of Caltech’s trustees, the JPL solar polar spacecraft was eliminated, and JPL was also denied funding to build a Halley’s comet rendezvous mission for the 1986 apparition (Westwick, 2007, pp. 51–54). So only ESA’s solar polar mission, renamed Ulysses, actually flew. It used Jupiter flybys to achieve its flyovers of the Sun’s poles. It was launched by Shuttle Discovery on October 6, 1990, and operated until 2009.
JPL’s Magellan was an orbiting radar mission built largely from spare parts developed for other missions. It was a descoping of an older mission concept, the Venus Orbiting Imaging Radar, which had been terminated during the budget cutting earlier in the decade. Launched in by Shuttle Atlantis on May 4, 1989, it produced a radar map covering nearly the entire Venusian surface. In 1994, at the end of its operating life, Magellan was used for aerobraking tests and then was deorbited (Westwick, 2007, pp. 198–202).
The small number of planetary missions NASA authorized during the 1970s and 1980s caused JPL to turn to other federal agencies for funding. During the 1970s, the laboratory developed energy technologies for the Department of Energy, including solar and geothermal studies, fostered by the energy crises of that decade. That effort ended with the Reagan Administration, and instead the laboratory returned to its roots in the defense world. It developed, among other things, a combat management system for the U.S. Army known as the All Source Analysis System (Westwick, 2007, pp. 136–140). JPL actually reached its peak employment in 1992–1993, with 7,700 employees, as planetary exploration funding began to expand again while it was still completing its obligations to the Defense Department. As a consequence, the laboratory would shrink through the 1990s, even as the number of missions it developed expanded.
The “Faster Better Cheaper” Era
The Ranger, Surveyor, and Mariner missions of the 1960s and 1970s had developed a particular model of operation, in which JPL (sometimes with system contractors) developed spacecraft but NASA science officials decided what scientific payloads they would carry. Sometimes NASA assigned instruments to various “principal investigators,” and sometimes it held open instrument competitions. The Voyager instrument payload, for example, was competed. This model of operation continues to the present with larger missions, which are often referred to as “flagship” missions. But during the 1990s, NASA leaders tried to end it. Their replacement idea was to compete entire missions. This era, which was supposed to achieve more missions at lower cost, was known as Faster Better Cheaper.
The last flagship mission was supposed to have been a Saturn orbiter with an entry probe, somewhat like Galileo. It came to be named Cassini/Huygens. This was approved in 1989 as a joint NASA/ESA mission, with NASA funding the orbiter and ESA providing a Titan atmosphere probe. It also became the target of attacks by NASA Administrator Daniel S. Goldin, appointed in 1992, who deemed it too big, too slow, and too expensive. He called it a “Battlestar Galactica” and proclaimed an end to all such future missions (Lambright, 2007, pp. 33–43; McCurdy, 2001; Roy, 1998).
Many planetary scientists had also grown frustrated with the difficult process of developing and marketing these large, complex missions to NASA, the Office of Management and Budget, and Congress. They required the consensus of a large community to gain funding, which inevitably worked against cost containment. One attempt to find a way around this political problem, a series of similar missions based on an Earth orbiter spacecraft called “Planetary Observers,” collapsed when the Office of Management and Budget refused to give up the privilege of approving each mission individually. Only a single Planetary Observer, Mars Observer, was approved and built, and it was lost in 1993 shortly before reaching Mars (Conway, 2015, pp. 9–33). An expected follow-on “Lunar Observer” was, in effect, lost with it.
The failure of the Planetary Observer idea to gain traction did not end the effort to reform the process. The competed mission model already existed in NASA but not in planetary exploration. The astrophysics Explorer program had long been allowed to choose its own missions without explicit, individual approval from the Office of Management and Budget and Congress, as long as it remained within a fixed budget, and it became the model of a low-cost planetary exploration called “Discovery.” The Discovery program allowed individual scientists to devise and propose entire missions, which would be subjected to a review and selection process by other scientists. These competed missions would have a cost cap (initially $150 million), and NASA would hold a Discovery program competition every few years. The Discovery program, combined with a new Mars exploration program approved after Mars Observer’s 1993 loss, would radically transform the way JPL operated. JPL, and other NASA centers, would become managers of these principal investigator led missions, as they are often called.
In order to “kick-start” the program, the first two Discovery missions were not competed. The first was assigned to the Applied Physics Laboratory and was called NEAR (Near Earth Asteroid Rendezvous mission; Prockter et al., 2002). The second, Mars Pathfinder, was assigned to JPL. The Mars Pathfinder mission’s goal was to land a small meteorological station on Mars and operate it for 90 days. Later, a “microrover” was added that carried an alpha-proton X-ray spectrometer. Its spectacular landing on July 4, 1997 (aided by a decision to release images almost immediately onto the newly public World Wide Web), brought enormous public attention to NASA and to Mars (Conway, 2015, p. 129; Mishkin, 2003; Muirhead, 1999). Costing only about a tenth of what Viking had, it also seemed to justify the new low-cost approach.
JPL’s first competitively awarded Discovery mission was called Stardust. Proposed by a team led by Donald Brownlee of the University of Washington, this effort was designed to collect interstellar dust and gases from the comet 81P/Wild 2 in 2004 and return them to Earth in 2006. Stardust was launched February 7, 1999, and placed its payload in the UTdesert January 15, 2006 (Brownlee et al., 2003). The still-operating spacecraft was later retargeted to fly by comet Tempel 1 in 2011, as a follow-up to the Deep Impact mission of 2005 (Veverka et al., 2013).
As part of the post-Mars Observer NASA Mars Exploration Program, JPL was assigned a reflight of part of Mars Observer’s payload. This became the Mars Global Surveyor mission, and it was the first mission in a new Mars exploration program, known as Mars Surveyor. The Mars Surveyor program was supposed to fly two missions to Mars every launch opportunity (about 26 months). After Mars Global Surveyor, these Surveyor program missions were Mars Climate Orbiter and Mars Polar Lander, launched in 1998, the 2001 Mars Odyssey mission, and a 2001 lander mission that was cancelled after both of the Mars Surveyor 1998 missions failed.
The Mars Surveyor program was a hybrid of the competed and assigned management model and exclusively operated via systems contract. JPL’s chosen contractor was Lockheed-Martin’s Astronautics division in Denver (the same organization that had developed the Viking landers). Surveyor also employed a cost cap like the Discovery program, but, unlike the Discovery program, required two missions for the same amount of money. The low-cost Mars Pathfinder mission was not cheap enough; for the 1998 mission pair, JPL had to deliver two spacecraft to Mars for the same price tag (Conway, 2015, pp. 140-167).
Mars Global Surveyor carried five of Mars Observer’s instruments to Mars in 1997 and operated there until 2006. The Mars Climate Orbiter carried another Mars Observer instrument in addition to a small camera but was lost due to a navigational error. Its companion mission, the Mars Polar Lander, failed during its descent to Mars. JPL’s formal failure review traced the failure to a software problem related to the landing legs, but the Mars Phoenix mission, which used the cancelled 2001 lander hardware to perform a very similar mission, found numerous other design flaws that could also have caused the Polar Lander’s failure (Conway, 2015, pp. 301–312). Thus the Polar Lander’s fate is unknown. The final Mars Surveyor program mission, 2001 Mars Odyssey, reached Mars late in 2001 and was still operating in mid-2018. Its primary instrument, a gamma ray spectrometer built for Mars Observer, provided hydrogen and mineralogical maps of the martian surface.
A NASA-commissioned investigation into the Mars Surveyor 1998 failures concluded that “Mars ’98 had inadequate resources to accomplish the requirements. Through a combination of perceived Headquarters mandates and concern for loss of business, JPL and Lockheed-Martin Astronautics committed to overly challenging programmatic goals” (Report of the Mars Program Independent Assessment Team, 2000, p. 23). Neither JPL nor LMA had assigned adequate experienced management oversight to the project, and their efforts to reduce operating costs had resulted in having the same small team try to operate Mars Global Surveyor, both Mars 1998 missions, and the Discovery program’s Stardust mission simultaneously. In a speech at JPL after these failures, NASA Administrator Goldin (2000) echoed the issue of resources: “in my effort to empower people, I pushed too hard, and in so doing, stretched the system too thin.”
The focus on resources (i.e., money and experienced talent) is crucial, because while the Mars Surveyor program ended, the idea of cost-capped, competed, principal investigator led missions did not end with it. The Discovery program continued and had its cost cap raised, and the new Mars Exploration program that replaced the Mars Surveyor program had both competed missions (called Mars Scouts) and assigned, flagship class missions. NASA headquarters also formulated a new program of competed outer planets missions called New Frontiers. Competition and cost-capping survived the debacle of 1999—to a degree, at least.
After the loss of the Mars Climate Orbiter and Mars Polar Lander, NASA and JPL embarked on a rapid planning exercise to decide what to send to Mars in 2003 and what to do for the rest of the decade. Out of that pair of exercises came a mixed program that was devised to develop the technological infrastructure for a Mars Sample Return mission around 2010, as well as preserve competition. Assigned flagship missions would provide the necessary technologies (and do science), while a Mars Scout program would fly competed, cost-capped, focused-Mars science missions (Conway, 2015, pp. 202–205; Hubbard, 2011). The flagship class missions were the Mars Exploration Rovers (MERs), the Mars Reconnaissance Orbiter, and a Mars Science Lander to kick off the multimission sample return campaign. The first Mars Scout mission was awarded to Peter Smith of the University of Arizona and managed by JPL. This used the cancelled 2001 lander hardware to fly to Mars’ north polar region. The second Mars Scount, the Mars Atmosphere and Volatiles Evolution Mission, was awarded to Bruce Jaksosky of the University of Colorado and managed by NASA Goddard Space Flight Center.
The MER mission, which sent independent rovers to Mars in 2004 that operated until 2010 and 2018, marked a new turning point in planetary exploration. These rovers did not require a lander to communicate with and manage them as Mars Pathfinder’s rover had; they could be operated either via a relay orbiter (Mars Global Surveyor and, later, 2001 Mars Odyssey, served as their primary relays) or from Earth via a small on-board high-gain antenna. The two rovers were ultimately able to traverse dozens of miles.
The MER mission was a hybrid of the management models discussed earlier: the rover development and mission overall were assigned to JPL, which had strongly promoted it to NASA, but the mineralogy instrument payload chosen had been developed by a team led by Cornell scientist Steve Squyres, for the cancelled 2001 lander mission. This arrangement was a result of the short available development time for the mission, 36 months, which did not allow for a competition to be held. Since Squyres’ payload existed already, it, and his science team, were drafted (see Conway, 2015; Hubbard, 2011; Squyres, 2005).
Despite the great success of MER, the planned Mars Sample Return mission intended to follow it did not come to fruition. A 2004 presidential decision to send astronauts back to Earth’s Moon in the 2010s led to cuts in the Mars exploration budget, and the sample return campaign that was to start in 2010 was descoped into a single, albeit large, Mars Science Laboratory. This, too, was successfully implemented, but suffered an expensive 26-month delay in its launch due to development problems with its mechanical actuators (Conway, 2015, p. x). The Mars Science Laboratory mission landed in 2012, and its rover, named “Curiosity,” was still operating in 2019.
One long-term consequence for the adoption of a competed mission model within NASA for JPL was having to develop the ability to work with university-based principal investigators (mostly) to conceptualize, design, and cost small to medium-size missions relatively quickly (a few months) in response to calls for mission proposals from the various competed mission programs. A project formulation office manages that infrastructure, while technology development funding from NASA and a small internal research and development fund supports new technologies for new potential mission proposals.
Another consequence was having to manage many projects at once, leading to organizational reform. After the Mars Surveyor 1998 failures, the JPL created an Office of Safety and Mission Success to maintain technical and management standards, and “product quality” in current management jargon, while project implementation remains within thematic directorates—Earth, Mars, Solar System, and so on. This structure replaced a single implementation directorate, JPL’s Flight Project Office, which took over projects once they had been “sold” to NASA by theme directorates. It had been disbanded in 1993 in order to reduce costs. The demise of the Flight Project Office had ushered in a brief era in which there were no longer consistent engineering standards and management practices across the JPL. These were recreated in the early 2000s.
The “Battlestar Galactica” of missions, Cassini/Huygens, left Earth on October 15, 1997. It reached Saturn on July 1, 2004, though not unproblematically. The receiver for the probe data that ESA had supplied to JPL could not compensate for the doppler shift that Cassini would see during the probe’s descent. The problem was discovered during the long flight to Saturn. While it could not be fixed, it could be mitigated by altering Cassini’s trajectory. The intent had been to release Huygens during the spacecraft’s first orbit of Saturn. Instead, JPL’s navigators redesigned the spacecraft’s first four orbits to improve the communications geometry and thereby reduce the Doppler shift that Cassini’s receiver would experience. Huygens was released on the redesigned third orbit instead (Oberg, 2005).
Huygens separated from Cassini on December 25, 2004, and made its Titan descent on January 14, 2005. A software error caused one of the probe’s two redundant transmitters to fail to send data during the mission, costing some wind data and imagery. But the mission still returned 350 images of the alien world during its operational hours, along with extensive chemistry data.
Cassini operated in Saturn orbit until September 2017, when it was disposed of in a “Grand Finale” campaign that used Titan flybys to reshape and shrink the orbits, eventually bringing the vehicle through Saturn’s rings and finally burning it up in Saturn’s atmosphere (NASA, 2019). Cassini witnessed unexpected cryovolcanism on the tiny moon Enceladus, even flying through, and sampling, a plume in 2008 that turned out to be water vapor and other gases. Enceladus proved to be the source of material for Saturn’s E-ring, and the evidence of water led to rather extravagant astrobiological speculations about the tiny moon (Thompson, 2017).
During its first decade as a NASA center, JPL had focused on lunar and planetary missions. But it began to diversify during the 1970s into both Earth science and astrophysics. This was another response to the downturn in support for planetary exploration during that decade.
The laboratory’s first ocean science mission was Seasat-A. JPL had actually been building microwave instruments for the U.S. weather satellite program throughout the 1960s and early 1970s, and Seasat-A provided an opportunity to expand the use of microwave remote sensing in Earth orbit. Unfortunately, the satellite power system failed early in the mission, and it was not until the early 1990s that JPL was able to develop another ocean remote sensing satellite. In 1993, it launched a joint ocean altimetry mission with the French space agency, called Topex/Poseidon, that was the forerunner of a series of such missions that continue into the present (Westwick, 2007).
JPL also won a number of instrument competitions for NASA’s Earth Observing System, developed in response to scientific and governmental interest in climate research during the 1990s. This began operating in 1999 after a difficult development phase. JPL also developed a number of competed Earth System Science Pathfinder missions (see Table 1). By the mid-2000s, Earth science was frequently the largest piece of JPL’s budget (Table 2).
Table 1. JPL Major Missions
Spacecraft Built By JPL
January 31, 1958
March 5, 1958
March 26, 1958
July 26, 1958
August 24, 1958
December 6, 1958
March 3, 1959
August 23, 1961
November 18, 1961
January 26, 1962
April 23, 1962
July 22, 1962
August 27, 1962
October 18, 1962
January 30, 1964
July 28, 1964
November 5, 1964
November 28, 1964
February 17, 1965
March 21, 1965
June 14, 1967
February 24, 1969
March 27, 1969
May 8, 1971
May 30, 1971
November 3, 1973
Viking 1 Orbiter
August 20, 1975
Viking 2 Orbiter
September 9, 1975
August 20, 1977
September 5, 1977
October 18, 1989
December 4, 1996
October 15, 1997
Deep Space 2
January 3, 1999
Mars Exploration Rover Spirit
June 10, 2003
Mars Exploration Rover Opportunity
July 7, 2003
Mars Science Laboratory
November 26, 2011
Soil Moisture Active-Passive
January 31, 2015
Spacecraft Built By JPL Subcontractor
May 30, 1966
September 20, 1966
April 17, 1967
July 14, 1967
September 8, 1967
November 7, 1967
January 7, 1968
June 27, 1978
Solar Mesosphere Explorer
October 6, 1981
Infrared Astronomical Satellite
January 25, 1983
May 4, 1989
August 10, 1992
October 25, 1992
Mars Global Surveyor
October 25, 1992
Deep Space 1
October 24, 1998
Mars Climate Orbiter
December 11, 1998
Mars Polar Lander
January 3, 1999
February 7, 1999
Wide-field Infrared Explorer
March 4, 1999
June 19, 1999
December 20, 1999
April 7, 2001
August 8, 2001
Galaxy Evolution Explorer
April 28, 2003
Spitzer Space Telescope
August 25, 2003
January 12, 2005
Mars Reconnaissance Orbiter
August 10, 2005
April 28, 2006
Mars Phoenix Lander
August 4, 2007
September 27, 2007
Orbiting Carbon Observatory
February 24, 2009
May 14, 2009
Wide-field Infrared Survey Explorer
December 14, 2009
August 5, 2011
Orbiting Carbon Observatory 2
July 20, 2014
May 5, 2018
Foreign Spacecraft w/ Major JPL Role
October 6, 1990
December 7, 2001
March 17, 2002
June 20, 2008
June 10, 2011
January 17, 2016
May 22, 2018
JPL Instrument on Other Spacecraft/Satellite
Scanning Multichannel Microwave Radiometer
October 24, 1978
Wide Field/Planetary Camera
April 24, 1990
Microwave Limb Sounder
September 12, 1991
Wide Field and Planetary Camera 2
December 2, 1993
August 17, 1996
Multi-angle Imaging Spectro-Radiometer
December 18, 1999
Advanced Spaceborne Thermal Emission and Reflection Radiometer
December 18, 1999
Atmospheric Infrared Sounder
May 4, 2002
December 13, 2002
June 2, 2003
Microwave Instr on Rosetta Orbiter
March 2, 2004
Microwave Limb Sounder
July 15, 2004
Tropospheric Emission Spectrometer
July 15, 2004
April 14, 2006
Moon Mineralogy Mapper (M3)
October 22, 2008
May 14, 2009
May 14, 2009
June 18, 2009
April 18, 2014
September 20, 2014
Cold Atom Laboratory
May 21, 2018
July 6, 2018
Table 2. Budget history chart
NASA and JPL's NASA Funding since 1980*
JPL NASA funds
* In millions of FY 2017 dollars. Does not include non-NASA JPL funds.
NASA Data from the 2017 Aeronautics and Space Report of the President; JPL Data from JPL CFO.
Another major impetus for diversification was the Discovery program of competed missions. After Mars Pathfinder and Stardust, JPL won a number of these, with considerable variety in mission targets. Collecting the solar wind and comet dust were the goals of two Discovery missions. The Deep Impact mission struck comet 9P/Tempel 1 with a copper impactor to help identify composition and surface strength, the GRAIL mission sent a pair of satellites to map the Moon’s gravity in great detail, and the Dawn mission, utilizing the solar-electric propulsion technology demonstrated by JPL’s Deep Space 1 mission in 1998, orbited two different main belt asteroids, Ceres (renamed a “dwarf planet” in 2006) and 4 Vesta. Somewhat unusually, JPL also managed the development of the Kepler exoplanet hunting telescope, which was awarded to NASA Ames Research Center’s William Borucki in 2001. JPL also began to promote astrophysics missions. The first was the assignment to build the Wide Field and Planetary Camera (WFPC) for the Hubble Space Telescope. When Hubble proved to have a flawed primary mirror, it developed a copy of WFPC known as WFPC 2 that had corrective optics (Smith, 1989; Trauger, 2014). WFPC 2 produced most of Hubble’s iconic astronomical imagery once installed during the first Hubble Servicing Mission in 1993. JPL also played a significant role in the international Infrared Astronomical Survey mission, launched in 1983. Finally, JPL won one of NASA’s “Great Observatory” missions, the Space Infrared Telescope Facility (SIRTF). Originally conceived in the 1970s as a Space Shuttle–based observatory, SIRTF went through a series of redesigns to make it less expensive and more useful. The Shuttle was a poor platform for an infrared telescope because the Shuttle (and the Earth below it) were major heat sources that rapidly depleted the instrument’s cryogenic coolant. Ultimately, SIRTF, renamed for astronomer Lyman Spitzer, was put in an “Earth trailing orbit,” in essence, following the Earth around the Sun, so that it was not exposed to the Earth’s own warmth. The Spitzer spacecraft was launched in 2003 and is expected to be shut down in 2020 (Rottner, 2017).
- Brownlee, D. E., Tsou, P., Anderson, J. D., Hanner, M. S., Newburn, R. L., Sekanina, Z., . . . Tuzzolino, A. J. (2003). Stardust: Comet and interstellar dust sample return mission. Journal of Geophysical Research: Planets, 108(E10).
- Burke, J. D. (1984, March). Personal profile. SPACEFLIGHT. London, U.K.: The British Interplanetary Society.
- Burke, J. D. (1996). Seven years to Luna Nine: Studies in intelligence. Washington, DC: U.S. National Archives, 1996 (Declassified 1994).
- Conway, E. M. (2015). Exploration and engineering: The Jet Propulsion Laboratory and the quest for Mars. Baltimore, MD: Johns Hopkins University Press.
- Dawson, V. P., & Bowles, M. D. (2004). Taming liquid hydrogen: The Centaur Upper Stage Rocket, 1958–2002 (SP-2004-4230). Washington, DC: NASA.
- Dethloff, H. C., & Schorn, R. (2003). Voyager’s grand tour: To the outer planets and beyond. Washington, DC: Smithsonian Books.
- DeVorkin, D. H. (1992). Science with a vengeance: How the military created the US space sciences after World War II. New York, NY: Springer-Verlag.
- Divine, R. A. (1993). The Sputnik challenge. Oxford, U.K.: Oxford University Press.
- Ezell, E. C., & Ezell, L. N. (1984). On Mars: Exploration of the red planet, 1958–1978. Washington, DC: NASA.
- Gallentine, J. (2010). Ambassadors from Earth. Lincoln: University of Nebraska Press.
- Goldin, D. S. (2000, March 29). When the best must do even better. Speech at the Jet Propulsion Laboratory, Pasadena, CA. Speeches of NASA Administrator Daniel S. Goldin, NASA History Office, Washington, DC.
- Hall, R. C. (1977). Lunar impact: A history of Project Ranger. NASA History Series (SP-4210). Washington, DC: NASA.
- Hubbard, S. (2011). Exploring Mars: Chronicles from a decade of discovery. Tucson: University of Arizona Press.
- Huntress, W. T., & Marov, M. Y. (2011). Soviet robots in the solar system. Chichester, U.K.: Springer-Praxis.
- James M. Beggs to Honorable David A. Stockman, September 29, 1981. (2001). Document II-31. In J. M. Logsdon et al. (Eds.), Exploring the unknown: Vol. V, Exploring the cosmos. Washington, DC: NASA.
- Johnson, S. B. (2002). The secret of Apollo: Systems management in American and European space programs. Baltimore, MD: Johns Hopkins University Press.
- Koppes, C. R. (1982). JPL and the American space program: A history of the Jet Propulsion Laboratory. New Haven, CT: Yale University Press.
- Lambright, W. H. (2007). Leading change at NASA: The case of Dan Goldin. Space Policy, 23(1), 33–43.
- McCurdy, H. (2001). Faster better cheaper: Low cost innovation in the US space program. Baltimore, MD: Johns Hopkins University Press.
- McLaughlin Green, C., & Lomask, M. (1969). Vanguard: A history. Washington, DC: NASA.
- Meltzer, M. (2015). The Cassini-Huygens visit to Saturn: An historic mission to the ringed planet. New York, NY: Springer.
- Meltzer, M. (2007). Mission to Jupiter: A history of the Galileo Project (SP-2007-4231). Washington, DC: NASA.
- Mishkin, A. (2003). Sojourner: An insider’s view of the Mars Pathfinder mission. New York, NY: Berkeley Books.
- Mudgway, D. J. (2001). Uplink-downlink: A history of the Deep Space Network, 1957–1997 (SP-2001-4227). Washington, DC: NASA.
- Muirhead, B. K. (1999). High velocity leadership. New York, NY: HarperCollins.
- Murray, B. C. (1989). Journey into space: The first thirty years of space exploration. New York, NY: Norton.
- NASA. (2019). Cassini: The grand finale. Washington, DC: Author.
- Oberg, J. (2005, January 17). How Huygens avoided disaster. The Space Review.
- President John F.Kennedy inaugural address (1961, January 20). JFK Library and Museum.
- Prockter, L., Murchie, S., Cheng, A., Krimigis, S., Farquhar, R., Santo, A., & Trombka, J. (2002). The NEAR Shoemaker Mission to Asteroid 433 Eros. Acta Astronautica, 51(1), 491–500.
- Pyne, S. J. (2010).Voyager: Seeking newer worlds in the third great age of discovery. New York, NY: Viking.
- Report of the Mars Program Independent Assessment Team. (2000, March 14). Washington, DC: NASA.
- Rottner, R. M. (2017). Making the invisible visible: A history of the Spitzer Infrared Telescope Facility (1971–2003). Washington, DC: NASA.
- Roy, S. A. (1998). The origin of the smaller, faster, cheaper approach in NASA’s solar system exploration program. Space Policy, 14(3), 153–171.
- Sagan, S. (1994). Pale blue dot: A vision of the human future in space. New York, NY: Ballantine Books.
- Siddiqi, A. (2000). Challenge to Apollo: The Soviet Union and the Space Race, 1945–1974. Washington, DC: NASA.
- Siddiqi, A. A. (2002). Deep space chronicle: A chronology of deep space and planetary probes (SP-2002-4524). Washington, DC: NASA.
- Smith, R. W. (1989). The Space Telescope. Cambridge, U.K.: Cambridge University Press.
- Squyres, S. (2005). Roving Mars: Spirit, Opportunity, and the exploration of the red planet. New York, NY: Hyperion.
- Thompson, J. R. (2017, April 12). The moon with the plume. Washington, DC: NASA.
- Trauger, J. (2014). Constructing the Wide Field and Planetary Camera 2. In R. D. Launius & D. H. DeVorkin (Eds.), Hubble’s legacy: Reflections by those who dreamed it, built it, and observed the universe with it (pp. 47–53). Washington, DC: Smithsonian Institution Scholarly Press.
- Veverka, J., Klaasen, K., A’Hearn, M., Belton, M., Brownlee, D., Chesley, S., . . . Wolf, A. (2013). Return to Comet Tempel 1: Overview of Stardust-Next results. Icarus, 222(2), 424–435.
- Waff, C. B. (1989). The struggle for the outer planets. Astronomy, 17(9), 44–52.
- Waff, C. B. (1993, April). The road to the deep space network. IEEE Spectrum, pp. 50–57.
- Westwick, P. J. (2007). Into the black: JPL and the American space program, 1976–2004. New Haven, CT: Yale University Press.
- Wheelon, A. D. (1995). Lifting the veil on Corona. Space Policy, 11(4), 249–260.
- Williamson, R. A. (1999). Developing the Space Shuttle. In Exploring the unknown: Vol. IV: Accessing space (pp. 161–193). Washington, DC: NASA.