[201] Unlike aircraft, whose clean forms are shaped by the laws of aerodynamics, spacecraft have assumed a host of strange configurations. The laws that shape them are different: how to fold up to fit within a shroud during the quick, fierce passage through the atmosphere and then unfold in airless space; how to gather electrical power from the Sun; how to deploy antennas to beam data and photographs back to Earth; how to stay in a narrow band within temperature extremes; how to maintain pointing orientation in a weird environment that has no up or down; how to land in a rock-strewn crater. Only manned spacecraft, which must reenter the atmosphere, have of necessity avoided the spraddled, insectlike look of these machines that are truly something new under the Sun.

Spacecraft have paced the growth of much engineering technology in the last decade. Their special requirements for lightweight electronics, miniaturized computers, unique power supplies, and automated cameras and scientific instruments have forced engineers to break new ground. Spacecraft have functioned unattended in space for years, faithfully working and reporting back to Earth long after their designed mission has been accomplished. The following pages show many of the classes of spacecraft that took the photographs in this book.

The Television infrared Observational Satellite (better known as Tiros) that pioneered in worldwide meteorological photography evolved into the ESSA satellite that NASA now delivers in orbit for the Environmental Science Services Administration. Nimbus is a larger, more sophisticated satellite designed to help develop instrumentation for longrange weather forecasting. The Applications Technology Satellites (ATS) carry meteorological and communications experiments to a 22 300-mile, Earth-synchronous orbit, from which they have provided spectacular full-Earth photographs.

Lunar and planetary spacecraft, a group distinct from Earth satellites, began with the Rangers, which were designed to radio back pictures as they approached the Moon to crash landings. The last three Rangers to be launched were completely successful, returning many thousands of excellent photographs.

The Mariner class of planetary explorers derived from Ranger technology, though needing improved guidance and communications systems. Mariner IV, man's first successful scout to Mars, set an excellent record of technical achievement: it completed a 7 1/2 month flight to its planetary rendezvous, radioing its pictures and scientific data back 150 million miles. Then it continued on in lonely solar orbit for an additional 29 months. When it finally fell silent, more than 3 years after launch, it was not because of any failure but simply because it had consumed all of the onboard gas used to maintain its attitude in space.

Five Lunar Orbiters were flown, returning some of the most dramatic photographs in this volume. These craft were unique in that, instead of the vidicon television systems used in other unmanned spacecraft, they carried film cameras of very high resolution, along with automatic laboratories that developed and fixed each picture, and then electronically scanned it for transmission back to Earth.

Five Surveyors soft-landed on the Moon. On Earth command they sent back scores of thousands of photographs ranging from panoramic views to high-resolution closeups of nearby rocks and soil. Surveyor Vll brought to an end America's highly successful automated exploration of the Moon in advance of man's first visit there.

The Mercury spacecraft that carried one man into near-Earth space were succeeded by the Gemini that carried two, and will be shortly followed by the Apollo spacecraft in which three astronauts will embark for the Moon. The shape, if not the size, of the first two classes of manned craft was similar, being designed for the 25 000-feet-per-second reentry velocity from Earth orbit. The Apollo spacecraft is slightly different, to suit the 36 000-feet-per-second velocity of reentry from a lunar trajectory.

The Nimbus satellite was conceived in 1958 as a relatively large satellite that would serve as a platform for research on advanced meteorological sensors. It operates in a Sun-synchronous polar orbit with its axis pointing toward Earth and its solar panels toward the Sun. This requires three-axis stabilization and rotating solar panels. Both Nimbus satellites launched to date were successful. Some characteristics of Nimbus 1:

Initiated by the Department of Defense in 1957, the Tiros Program was transferred to NASA shortly after its establishment. These satellites were designed to explore the feasibility of global weather observation from orbit. The first Tiros flew successfully in 1960 and the series went on to complete a string of 10 consecutive successes. Some specifications for Tiros Vl were:

The ESSA meteorological satellite uses much of the basic Tiros technology, but has a number of important improvements. It flies in a Sun-synchronous polar orbit so as to maintain unchanging illumination of the Earth beneath it from day to day. The early Tiros satellites had their cameras pointing along the spin axis, which limited the coverage; the ESSA series has its cameras pointing radially so that each rotation of the spinning satellite brings the Earth into camera view The satellites are precessed in orbit by electromagnetic coils so that the satellite appears as a wheel rolling along its orbital path. By these techniques, daily global coverage under proper lighting conditions is achieved. The ESSA series has a perfect record of six successful flights to date. Specifications for ESSA III:

The Applications Technology Satellite (ATS) is a multipurpose spacecraft designed to conduct research in synchronous Earth orbit at 22 300 miles above the Equator. In such an orbit, the satellite remains fixed relative to the subsatellite point on Earth. In addition to communications experiments, this satellite provided the first continuous meteorological observations of the world beneath it. Continuous observation will help detect violent but short-lived storms such as thunderstorms and tornadoes, whose life cycles may be less than the time for a low-orbit satellite to complete a single orbit. Of three ATS spacecraft flown, two were successful and one suffered a launch failure. Characteristics of ATS-III:

Ranger was the first U.S. spacecraft designed to make sophisticated observations of another celestial body-the Moon. Nine Rangers were built in all Of these, the first two were test vehicles for Earth orbit and experienced launch failures. Seven were launched to the Moon. The first three were de signed to take moderate-resolution photograph: during approach and to rough-land a seismometer capsule; they failed due to a combination of launch vehicle and spacecraft problems. The last four Rangers were exclusively devoted to detailed lunar photography with a battery of six vidicon cameras An arcing problem during launch rendered Ranger Vl's cameras inoperable. However, Ranger VII, VIII, and IX completed perfect missions and re turned thousands of excellent photographs of the lunar terrain. Specifications for the final (Block III) Ranger:

Mariner spacecraft were designed to reconnoiter the planets Mars and Venus. Mariner I experienced a launch-vehicle failure, but Mariner II made the world's first successful flight to another planet, passing Venus 109 days after launch at a distance of 21648 miles, and recording numerous scientific observations. Mariner III also experienced a launch failure, but Mariner IV made the world's first successful flyby of Mars at a distance of 6118 miles. The most recent of the Mariner series, Mariner V, successfully observed Venus from a distance of 2131 miles in October 1967, but, like its Mariner II predecessor, carried no camera. Specifications for Mariner IV:

Lunar Orbiter was designed to operate in conjunction with Surveyor. By photographing Surveyor sites from orbit, the detailed Surveyor findings could be extrapolated to other areas that appear identical in orbital photography. All five Lunar Orbiters were successful. They photographed all potential Apollo landing sites to resolutions down to I meter. Having completed the Apollo photographic requirement, the last two Orbiters photographed the entire front face of the Moon at resolutions of some 10 times better than possible from Earth, completed photography of the far side at resolutions somewhat better than obtainable of the front side from Earth telescopes, and obtained detailed photography of several dozen lunar features of particular scientific interest. Some Orbiter specifications:

The Surveyor spacecraft series was conceived in 1959 to soft-land scientific experiments on the Moon and carry out initial surface investigations. It was an ambitious undertaking at the time, for it relied on developing the new technology of closed-loop, radar-controlled landings, and, in addition, required the successful development of the world's first hydrogen-oxygen rocket stage, the Centaur Of seven spacecraft, five were completely successful; two experienced in-flight failures prior to landing. The Surveyor not only studied four potential Apollo landing areas, but on its last mission visited the scientifically interesting crater Tycho. In addition to relaying thousands of surface photographs to Earth, Surveyor measured surface properties by manipulating the lunar soil with a mechanical arm and conducted chemical analysis of the lunar material Typical Surveyor specifications:

The Mercury spacecraft was designed to conduct the first U.S. experiments with man in Earth orbit. This spacecraft was constrained in weight by the capability of a modified Atlas launch vehicle and pioneered in lightweight manned spacecraft capable of reentry through the atmosphere. During the four successful orbital Mercury missions, astronauts Glenn, Carpenter, Schirra, and Cooper accumulated 53 hours of space-flight experience. Typical Mercury specifications:

This program was planned to investigate longer duration manned flight and the practicality of rendezvous and docking in space. In 10 missions, each with a 2-man crew, 1940 man-hours of flight time were accumulated. Included were a flight lasting 2 weeks, six rendezvous missions, four docking missions, use of a docked propulsion stage to maneuver to high altitudes, 5 hours of extravehicular activity, and the conduct of numerous scientific experiments. Some characteristics of the Gemini spacecraft:

The Apollo command and service module (CSM) shown here is designed to carry three astronauts into lunar orbit from which two of them will descend to a landing in another spacecraft, the lunar module. After the lunar landing and subsequent rendezvous in lunar orbit, the CSM will inject itself into an Earth-return trajectory. On reaching Earth, the command module alone will reenter the atmosphere at a velocity of about 36000 feet per second, some 11000 fps faster than reentry from Earth orbit. The command module contains advanced guidance and control equipment for accurate maneuvering into lunar orbit and into the narrow-entry corridor upon return.

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