Ranger Program

Date February 23, 1961-March 24, 1965

The Ranger space-probe program provided the first close-up photographs of the lunar surface, prepared the way for the Surveyor lander program and the Apollo piloted missions, and demonstrated the need for meticulous preflight testing of spacecraft.

Locale Pasadena, California; Cape Canaveral, Florida

Key Figures

• William H. Pickering (1910-2004), New Zealand-born American director of the Jet Propulsion Laboratory, who encouraged the design of deep-space probes
• Gerard Peter Kuiper (1905-1973), Dutch American astronomer and lead scientist for the final block of successful Ranger missions
• Eugene Merle Shoemaker (1928-1997), American geologist who pioneered the study of lunar geology and meteor impacts
• Harold C. Urey (1893-1981), American Nobel laureate in chemistry who advocated the study of the Moon as a key to understanding the formation of the solar system
• Harris Schurmeier (b. 1924), American project manager for the final successful missions of the Ranger program

Summary of Event

The foundations for the Ranger program were laid in 1958 and 1959 at the Jet Propulsion Laboratory (JPL) in Pasadena, California, when JPL, under the leadership of William H. Pickering, began designing a basic platform for future planetary and lunar missions. During the planning stages, a host of now-routine needs in space exploration were encountered. The spacecraft was designed to use solar panels for electrical power and three-axis stabilization to maintain a constant orientation in space. It would be capable of midcourse maneuvers to improve its trajectory and have a steerable high-gain antenna for transmitting data and receiving commands and on-board computers capable of executing preprogrammed commands or acting on real-time commands transmitted from Earth. The platform itself consisted of a base with solar panels and an antenna. Instrument packages designed for specific mission needs could be mounted on the base as needed.

In addition, it became apparent that the project would need a global system capable of continuous tracking of deep-space probes. Test facilities capable of simulating the vibration and acceleration during launch and the vacuum of space were constructed because the performance of electronics in the vacuum of space was virtually unknown. Finally, sterilization of the spacecraft to prevent possible contamination of space by terrestrial microbes became a routine part of mission preparation.

In 1960, JPL’s spacecraft design was selected for lunar missions by the National Aeronautics and Space Administration (NASA), and the project was designated “Ranger.” The spacecraft were commissioned in groups, or blocks. Block 1 consisted of Rangers 1 and 2. The Ranger spacecraft were conceived as lunar impact missions, where measurements and photographs would be made en route to the Moon. During the remaining months of 1960 and into 1961, the deep-space tracking network was commissioned. On August 1, 1961, the launch countdown for Ranger 1 was abruptly halted when some of the pyrotechnics on the spacecraft unexpectedly fired, causing the solar panels to begin unfolding and the instruments aboard the spacecraft to unexpectedly turn on. The launch was rescheduled for the next favorable launch window. Ranger 1 was launched on August 23 and entered Earth’s orbit, but the second burn of the third stage engine failed to launch the spacecraft out of low orbit. Nevertheless, most of the spacecraft components performed successfully. Ranger 2, launched on November 18, suffered an almost identical fate.

Ranger 3 was the first of a second generation of Rangers (block 2), designed to jettison a capsule with a seismometer onto the lunar surface before impact. On January 22, 1962, a problem with the fuel tanks on the rocket booster resulted in frantic around-the-clock repairs to meet the scheduled launch date of January 26. The launch went off on schedule but the guidance of the booster failed, putting the spacecraft on a trajectory that would make it impossible to hit the Moon. Still, the midcourse correction firing was made to test the system. Ranger 3 missed the Moon by about 30,000 kilometers (18,650 miles) and was tracked to about 1.6 million kilometers (1 million miles) from Earth.

Ranger 4 was successfully launched on April 23, but all communication with the spacecraft was lost soon after launch. The beacon on the lunar instrument capsule was tracked until the spacecraft passed behind the Moon, where it impacted on the far side. Ranger 4 made the first U.S. lunar impact.

On October 18, Ranger 5 was successfully launched on a lunar trajectory, but about fifty minutes after launch a short circuit in the power-switching circuits caused loss of power from the solar panels. The batteries on the spacecraft provided power for almost nine hours, not enough time to reach the Moon. It became impossible to perform midcourse maneuvers or achieve any of the lunar science objectives. The spacecraft missed the Moon by 450 kilometers (280 miles), and the beacon in the instrument capsule was tracked for eleven days.

The next series of Ranger missions, designated block 3, eliminated the instrument capsule in favor of television cameras. This decision caused a number of scientists to complain that science on the mission was being sacrificed for engineering considerations. Although five blocks of spacecraft had initially been planned, in July of 1963, NASA canceled the Ranger missions that were scheduled to begin after block 3, meaning the program would end after Ranger 9. The scientific team for block 3 was headed by astronomerGerard Peter Kuiper, geologist Eugene Merle Shoemaker, and chemistHarold C. Urey.

Ranger 6 was launched on January 30 and worked flawlessly until fifteen minutes before impact on February 2, when the television cameras failed to turn on. A number of unexplained instrument anomalies early in the mission were later attributed to an electrically conducting cloud of gas emitted during third-stage separation, which may have caused electrical shorts within the spacecraft. It became clear that the protective cover of the spacecraft needed to provide not only mechanical protection but also a leakproof seal.

In the wake of the string of failures, Harris Schurmeier was appointed project manager and made photography the objective of the program. Ranger 7, launched on July 28, marked the first total success in the program. The spacecraft impacted on July 31. The television cameras turned on seventeen minutes before impact, transmitting more than 4,300 photographs, with the last taken less than one kilometer (two-thirds of a mile) from the lunar surface. One surprise from these first lunar close-up photographs was the roundness of the rims of small craters, which is now known to result from erosion by tiny impacts over millions of years. Ranger 8, launched on February 17, 1965, was another complete success. Impact on February 20 was less than 25 kilometers (15.5 miles) from the intended target; the spacecraft had returned 7,137 photographs before impact.

The success of Ranger 9 made the overall program a success. The spacecraft was launched on March 21, so precisely on course that even with no midcourse correction, it would have missed its intended target by only 600 kilometers (373 miles). A new conversion system allowed images from the spacecraft to be converted to conventional television format, enabling photographs to be transmitted live on network television. The spacecraft impacted inside the crater Alphonsus, nearly at the center of the Moon’s Earth-facing surface, on March 24, and transmitted 5,814 photographs.

Significance

The early years of U.S. space exploration were marked by a heartbreaking and seemingly endless series of failures. These were even more stinging in the wake of several Soviet “firsts” at the height of the Cold War “space race”—the first artificial satellite (Sputnik 1) and the first person in space (Yuri Gagarin) in 1961 among them. Even though the situation improved during the early 1960’s, the six failures of the Ranger spacecraft were discouraging. The spectacular success of the final three missions provided a much-needed boost in morale and international prestige.

Apart from political prestige and scientific value, the Ranger program demonstrated clearly the need for rigorous and meticulous testing of spacecraft before launch. Apparently insignificant factors like tiny flecks of debris and electrically conductive gases vented during stage separation had caused problems and mission failures. The lessons learned from Ranger generated support for intensive testing of the later Surveyor lander missions, which, although they were much more complex than the Ranger missions, were almost entirely successful. The sacrifice of some scientific goals in favor of engineering considerations was painful for many project scientists but ultimately resulted in greater scientific benefits because of higher success rates.

The JPL vision of a platform for planetary missions bore fruit. Mariner 2, based on a modified Ranger design, made the first successful flyby of Venus on December 14, 1962. Mariner 4, another probe based on Ranger design, made the first successful photographic reconnaissance of Mars on July 14, 1965.

One additional technical innovation to appear during the Ranger program was digital processing of images. A newly developed digital technique for removing signal distortions from image data turned out to be better than the electronic methods that were originally envisioned, and it soon became the standard method for processing images.

Bibliography

Hall, R. Cargill. Lunar Impact: A History of Project Ranger. NASA SP-4210. Washington, D.C.: Scientific and Technical Information Branch, 1977. A history and chronology of the Ranger program. Available at http://history.nasa.gov/SP-4210/pages/TOC.htm.

‗‗‗‗‗‗‗. Project Ranger, a Chronology: NASA and Jet Propulsion Laboratory. Pasadena, Calif.: Jet Propulsion Laboratory, California Institute of Technology, 1971. A dry but detailed chronology of the Ranger program, with references to other significant space events of the time.

Levy, David H. Shoemaker by Levy: The Man Who Made an Impact. Princeton, N.J.: Princeton University Press, 2000. Biography of Eugene Merle Shoemaker, pioneering student of meteor craters and codirector of the Ranger television experiments.

National Space Sciences Data Center (NSSDC) Master Catalog. Spacecraft Query Form. NASA Goddard Space Flight Center, 2006. Entry to a database on satellites and space probes. Can be searched by name, date, or keyword and includes both U.S. and foreign missions. Available at http://nssdc.gsfc.nasa.gov/ database/sc-query.html. A readable narrative of the Ranger program and its fascinating history.

Shoemaker, Carolyn S. “Ups and Downs in Planetary Science.” Annual Review of Earth and Planetary Sciences 27 (1999): 1-17. A personal memoir by a long-time planetary scientist and the widow of Eugene Shoemaker. Describes his early studies of craters and his career in lunar and planetary exploration.