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Justin's Astronomy

Sputnik 1:

Sputnik 1 (Russian: Спутник-1, Satellite 1) was the first artificial satellite to be put into orbit, on October 4, 1957. Coming at the height of the Cold War, the launching of Sputnik caught the West by surprise, and in the U.S. led to a wave of self-recriminations, the beginning of the space race, and a movement to reform science education.

The satellite had a mass of about 83 kg (184 pounds). It had two radio transmitters (20 and 40 MHz) and is believed to have orbited Earth at a height of about 250 km (150 miles). Analysis of the radio signals was used to gather information about the electron density of the ionosphere. Temperature and pressure was encoded in the duration of radio beeps, indicating the satellite was not punctured by a meteorite. Sputnik 1 was launched by an R-7 rocket. It incinerated upon re-entry on January 3, 1958.

Sputnik was the first of several satellites in the Soviet Union's Sputnik program, the majority of them successful. Sputnik 2 followed as the second satellite in orbit, also the first to carry an animal, the dog Laika. The first failure occurred with Sputnik 3.

Sputnik 1 spacecraft was launched from Baikonur Cosmodrome at Tyuratam (370 km southwest of the small town of Baikonur) in Kazakhstan, then part of the Soviet Union. The Russian word "Sputnik" means "travel companion" ("satellite" in the astronomical sense). The full official name, however, translates as "Artificial Earth Satellite" (ISZ in Russian literature). In 1885 Konstantin Tsiolkovsky first described in his book Dreams of Earth and Sky (ISBN 1414701632) how such a satellite could be launched into a low altitude orbit. It was planned as a contribution to the International Geophysical Year (1957-1958), with three of the five Sputnik satellites reaching orbit during that period.

The actual sequence of decision-making as to the form of Sputnik 1 was convoluted. A tonne-and-a-half, cone-shaped artificial satellite capable of making many physics measurements in space was first planned by Academician Keldysh, but when the Soviets read that the American Project Vanguard had two satellite designs, a small one which was just to see if they could get something into orbit, the Soviets decided to have what translates as the "Simplest Satellite" too, one which was one centimeter larger in diameter, and much heavier, than Vanguard's "real" satellite. They had to see whether the conditions in low Earth orbit would permit the bigger satellite to remain there for a useful length of time. When, months after Sputnik 1, the Vanguard test satellite was orbited, Khrushchev ridiculed it as a "grapefruit." Once the Soviets found they could orbit a test satellite too, they planned to orbit Keldysh's space laboratory satellite as Sputnik 3, and did so after one launch failure.

The Sputnik 1 satellite was a 58.0 cm-diameter aluminum sphere that carried four whip-like antennas that were 2.4-2.9 m long. The antennas looked like long "whiskers" pointing to one side. The spacecraft obtained data pertaining to the density of the upper layers of the atmosphere and the propagation of radio signals in the ionosphere. The instruments and electric power sources were housed in a sealed capsule and included transmitters operated at 20.005 and 40.002 MHz (about 15 and 7.5 m in wavelength), the emissions taking place in alternating groups of 0.3 s duration. The downlink telemetry included data on temperatures inside and on the surface of the sphere.

Since the sphere was filled with nitrogen under pressure, Sputnik 1 provided the first opportunity for meteoroid detection (no such events were reported), since losses in internal pressure due to meteoroid penetration of the outer surface would have been evident in the temperature data. The satellite transmitters operated for three weeks, until the on-board chemical batteries failed, and were monitored with intense interest around the world. The orbit of the then-inactive satellite was later observed optically to decay 92 days after launch (January 4, 1958) after having completed about 1400 orbits of the Earth, travelling a cumulative distance of 70 million kilometers. The orbital apogee declined from 947 km after launch to 600 km by December 9.

The Sputnik 1 rocket booster also reached Earth orbit and was visible from the ground at night as a first magnitude object. The satellite itself, a small but highly polished sphere, was barely visible at sixth magnitude, and thus more difficult to follow optically. Several replicas of the Sputnik 1 satellite can be seen at museums in Russia and another is on display in the Smithsonian National Air and Space Museum in Washington, D.C.

The United States had also been working on satellites, primarily through teams working for the US Navy as Project Vanguard. Their first launch had originally been intended to go before Sputnik, but was delayed several times before eventually blowing up on the pad. A rush effort then started under the US Army's Jupiter project and succeeded launching Explorer I in January 1958. This is considered the start of the Space Race between the two superpowers, as an aspect of the Cold War. Both nations attempted to out-do each other in space exploration, eventually culminating in the launch of the Apollo 11 mission to the Moon.

In 2003 a back-up unit of Sputnik 1 called "model PS-1" was sold on eBay (minus the classified military radio parts that were removed in the 1960s). It had been on display in a science institute near Kiev. It is estimated that between four and twenty models were made for testing and other purposes.

A Sputnik 1 model was given as a present to the United Nations and now decorates the entry Hall of its New York City Headquarters.

Preceded by:
First satellite
Sputnik program Followed by:
Sputnik 2

Hear also


Voyager1 & 2:

The Voyager 1 & 2 spacecrafts is an 815-kilogram unmanned probe of the outer solar system and beyond, launched September 5, 1977, and currently operational. It is the farthest human-made object from Earth. The Voyager 1 spacecraft has moved into the solar system's final frontier, a vast area where the Sun's influence gives way to interstellar space. At 14 billion kilometers (95 astronomical units or 8.8 billion miles) from the Sun, Voyager 1 has entered the heliosheath, a region beyond termination shock – the heliosheath is the shocked region between the solar system and interstellar space. If Voyager 1 is still functioning when it finally passes the heliopause, scientists will get their first direct measurements of the conditions in the interstellar medium. At this distance, signals from Voyager 1 take more than thirteen hours to reach its control center at the Jet Propulsion Laboratory, a joint project of NASA and Caltech near Pasadena, California. Voyager 1 is on a hyperbolic trajectory and has achieved escape velocity, meaning that its orbit will not return to the inner solar system. Along with Pioneer 10, the now deactivated Pioneer 11, and its sister ship Voyager 2, Voyager 1 is becoming an interstellar probe.

Voyager 1 had as its primary targets the planets Jupiter and Saturn and their associated moons and rings; its current mission is the detection of the heliopause and particle measurements of solar wind and the interstellar medium. Both Voyager probes are powered by three radioisotope thermoelectric generators, which have far outlasted their originally intended lifespan, and are now expected to continue to generate enough power to keep communicating with Earth until around the year 2020.



Mission planning and launch

Voyager 1 was originally planned as Mariner 11 of the Mariner program. From the outset, it was designed to take advantage of the then-new technique of gravity assist. By fortunate chance, the development of interplanetary probes coincided with an alignment of the planets called the Grand Tour. The Grand Tour was a linked series of gravity assists that, with only the minimal fuel needed for course corrections, would enable a single probe to visit all four of the solar system's gas giant planets: Jupiter, Saturn, Uranus and Neptune. The identical Voyager 1 and Voyager 2 probes were designed with the Grand Tour in mind, and their launches were timed to enable the Grand Tour if desired.

Voyager 1 was launched on September 5, 1977 by NASA from Cape Canaveral aboard a Titan IIIE Centaur rocket, slightly after its sister craft, Voyager 2. Despite being launched after Voyager 2, Voyager 1 was sent on a faster trajectory so it reached Jupiter and Saturn before its sister craft.

Initially, an underburn in the second stage of the Titan IIIE rocket left an estimated one second worth of fuel remaining in that stage. Although ground crews were worried that Voyager 1 would not make it to Jupiter, the Centaur upper stage proved to have enough fuel to compensate.

For details on the Voyager instrument packages, see the separate article on the Voyager program.

Detail of Jupiter's atmosphere, as imaged by Voyager 1.
Detail of Jupiter's atmosphere, as imaged by Voyager 1.
Voyager 1 image of Saturn from 5.3 million km four days after its closest approach.
Voyager 1 image of Saturn from 5.3 million km four days after its closest approach.


Voyager 1 began photographing Jupiter in January 1979. Its closest approach to Jupiter was on March 5, 1979, at a distance of 349,000 kilometers (217,000 miles) from its center. Due to the greater resolution allowed by close approach, most observations of the moons, rings, magnetic fields, and radiation environment of the Jupiter system were made in the 48-hour period bracketing closest approach. It finished photographing the planet in April.

The two Voyager spacecraft made a number of important discoveries about Jupiter and its satellites. The most surprising was the existence of volcanic activity on Io, which had not been observed from the ground or by Pioneer 10 or 11.


The gravity assist at Jupiter was successful, and the spacecraft went on to visit Saturn. Voyager 1's Saturn flyby occurred in November 1980, with the closest approach on November 12 when it came within 124,000 kilometers (77,000 miles) of the planet's cloud-tops. The craft detected complex structures in Saturn's rings, and studied the atmospheres of Saturn and Titan. Because of the earlier discovery of a thick atmosphere on Titan, the Voyager controllers at the Jet Propulsion Laboratory elected for Voyager 1 to make a close approach of Titan and terminate its Grand Tour. (For the continuation of the Grand Tour, see the Uranus and Neptune sections of the Voyager 2 article.) The Titan-approach trajectory caused an additional gravity assist that took Voyager 1 out of the plane of the ecliptic, thus ending its planetary science mission.

Interstellar mission

It is estimated both Voyager craft would have sufficient electrical power to operate at least some instruments until 2020.


Voyager1 is in the heliosheath.
Voyager1 is in the heliosheath.

As the Voyager 1 space probe heads for interstellar space, its instruments continue to study the solar system; Jet Propulsion Laboratory scientists are using the plasma wave experiments aboard Voyager 1 and 2 to look for the heliopause.

Scientists at the Johns Hopkins University Applied Physics Lab believe that Voyager entered the termination shock in February 2003. Some other scientists have expressed doubt, discussed in the journal Nature of November 6, 2003. In a scientific session at the American Geophysical Union meeting in New Orleans on the morning of March 25, 2005, Dr. Ed Stone presented clear evidence that Voyager 1 crossed the termination shock in December 2004 [1]. The issue will not be resolved for some months as other data become available, since Voyager's solar-wind detector ceased functioning in 1990. However, in May 2005 a NASA press release said that consensus was that Voyager 1 was now in the heliosheath. [2].

Distance travelled

In November 2005, Voyager 1 was at a distance of 14.56 billion kilometers (97.3 AU or 9.05 billion miles) from the Sun, which makes it the most distant man-made object from Earth. At this distance, light (which travels at 300,000 kilometers per second) takes close to 13.8 hours to reach the spacecraft from Earth. As a basis for comparison, the Moon is about 1 light second from Earth, the Sun is about 8.5 light minutes away, and Pluto, the most distant planet in our solar system, is at an average distance of approximately 5.5 light hours. As of November 2005, the spacecraft was travelling at a speed of 17.2 kilometers per second relative to the sun (3.6 AU per year or 38,400 miles per hour), 10% faster than Voyager 2. It is not heading straight towards any particular star, but even if Voyager 1 were going straight toward the closest star system, Alpha Centauri, it would take about 80,000 years to get there.

Current Position

Voyager 1, as of January 2006, was at 12.13 declination and 17.079hrs Right Ascension, placing it in the constellation Ophiuchus.


Pioneer 10:

On December 3, 1973, Pioneer 10 sent back the first close-up images of Jupiter. On June 13th 1983 it passed the orbit of Neptune, then the outermost planet because of Pluto's highly eccentric orbit. By some definitions, this made the spacecraft the first artificial object to leave the solar system. However, Pioneer 10 has still not passed the heliopause or Oort cloud.

Famed for a time as the most remote object ever made by man, at last contact Pioneer 10 was over 7.60 billion miles away from Earth. (Until February 17, 1998, the heliocentric radial distance of Pioneer 10 had been greater than that of any other man-made object. But later on that date, Voyager 1's heliocentric radial distance, in the approximate apex direction, equaled that of Pioneer 10 at 69.419 AU. Thereafter, Voyager 1's distance will exceed that of Pioneer 10 at the approximate rate of 1.016 AU per year). As of December 30, 2005 Pioneer 10 was 89,7 AU away from the Sun.

Pioneer 10 was also outfitted with a plaque to serve as a message for any extraterrestrial life, in the unlikely case that it may be discovered.

The plaque on board the Pioneer spacecraft
The plaque on board the Pioneer spacecraft

Built by TRW[1], the spacecraft made valuable scientific investigations in the outer regions of our solar system until the end of its mission on March 31, 1997. The Pioneer 10's weak signal continued to be tracked by the Deep Space Network as part of a new advanced concept study of chaos theory. Before 1997 the probe was used in the training of flight controllers on how to acquire radio signals from space.

The last, very weak, signal from Pioneer 10 was received January 23, 2003. A contact attempt February 7, 2003, was not successful and further attempts are not planned. The last successful reception of telemetry was on April 27, 2002; subsequent signals were barely strong enough to detect. Loss of contact was probably due to a combination of increasing distance and the spacecraft's steadily weakening power source, rather than failure of the craft.

However, the planetary society mentions in their Pioneer Anomaly pages that there will be one last attempt to get data from the spacecraft on March 4, 2006. After this date the spacecraft antenna will never be aligned correctly again.

Pioneer 10 is heading in the direction of the star Aldebaran in the constellation Taurus. It will take Pioneer over 2 million years to reach it.

Pioneer anomaly

Main article: Pioneer anomaly

Analysis of the radio tracking data from the Pioneer 10 and 11 spacecraft at distances between 20–70 AU from the Sun has consistently indicated the presence of an anomalous, small Doppler frequency drift. The drift can be interpreted as being due to a constant acceleration of (8.74  1.33)  10−10 m/s2 directed towards the Sun. Although it is suspected that there is a systematic origin to the effect, none has been found. As a result, the nature of this anomaly has become of growing interest.

An artist's impression of Pioneer 10.
An artist's impression of Pioneer 10.

Image of Jupiter by Pioneer 10.
Image of Jupiter by Pioneer 10.


Project Mercury:

Project Mercury was the United States' first successful manned spaceflight program. It ran from 1959 through 1963 with the goal of putting a man in orbit around the Earth. Early planning and research was carried out by NACA, while the program was officially carried out by the newly created NASA. The name Mercury comes from the Roman god (it is also the name of the innermost planet of the solar system).

The Mercury program cost $1.5 billion in 1994 dollars. See NASA Budget.


Mercury spacecraft (also called a capsule or space capsule) were very small one-man vehicles; it was said that the Mercury spacecraft were not ridden, they were worn. Only 1.7 cubic meters in volume, the Mercury capsule was barely big enough to include its pilot. Inside were 120 controls: 55 electrical switches, 30 fuses and 35 mechanical levers. The spacecraft was designed by Max Faget and NASA's Space Task Group.

During the launch phase of the mission, the Mercury spacecraft and astronaut were protected from launch vehicle failures by the Launch Escape System. The LES consisted of a solid fuel, 52,000 lbf (231 kN) thrust rocket mounted on a tower above the spacecraft. In the event of a launch abort, the LES fired for 1 second, pulling the Mercury spacecraft away from a defective launch vehicle. The spacecraft would then descend on its parachute recovery system. After booster engine cutoff (BECO), the LES was no longer needed and was separated from the spacecraft by a solid fuel, 800 lbf (3.6 kN) thrust jettison rocket, that fired for 1.5 seconds.

To separate the Mercury spacecraft from the launch vehicle, the spacecraft fired three small solid fuel, 400 lbf (1.8 kN) thrust rockets for 1 second. These rockets are called the Posigrade rockets.

The spacecraft had only attitude control thrusters. After orbit insertion and before retrofire they could not change their orbit. The spacecraft had three sets of control jets for each axis (yaw, pitch and roll), supplied from two separate fuel tanks. An automatic set of high and low powered jets and a set of manual jets, fueled from either the automatic tank or the manual tank. The pilot could use any one of the three thruster systems and fuel them from either of the two fuel tanks to provide spacecraft attitude control.

The Mercury spacecraft were designed to be totally controllable from the ground in the event that the space environment impaired the pilot's ability to function.

The spacecraft had three solid fuel, 1000 lbf (4.5 kN) thrust retrorockets that fired for 10 seconds each. One was sufficient to return the spacecraft to earth if the other two failed. The first retro was fired, five seconds later the second was fired (while the first was still firing). Five seconds after that, the third retro fires (while the second retro is still firing). This is called ripple firing.

There was a small metal flap at the nose of the spacecraft called the "spoiler". If the spacecraft started to reenter nose first (another stable reentry attitude for the capsule), airflow over the "spoiler" would flip the spacecraft around to the proper, heatshield first reentry attitude.

Suborbital Mercury capsules encountered lower reentry temperatures and used beryllium heat-sink heat shields. Orbital missions encountered much higher temperatures during reentry and used ablative shields.

NASA ordered 20 production spacecraft, numbered 1 through 20, from McDonnell Aircraft Company, St. Louis, Missouri. Five of the twenty spacecraft were not flown. They were, Spacecraft #10, 12, 15, 17, and 19. Two unmanned spacecraft were destroyed during flights. They were Spacecraft #3 and #4. Spacecraft #11 sank and was recovered from the bottom of the Atlantic Ocean after 38 years. Some spacecraft were modified after initial production (refurbished after launch abort, modified for longer missions, etc) and received a letter designation after their number, examples 2B, 15B. Some spacecraft were modified twice, example, spacecraft 15 became 15A and then 15B.

A number of boilerplate spacecraft (mockup/prototype/replica spacecraft, made from non-flight materials or lacking production spacecraft systems and/or hardware) were also made by NASA and McDonnell Aircraft and used in numerous tests, including launches.


The Mercury program used three boosters: Little Joe, Redstone, and Atlas. Little Joe was used to test the escape tower and abort procedures. Redstone was used for suborbital flights, and Atlas for orbital ones. Starting in October, 1958, Jupiter missiles were also considered as suborbital launch vehicles for the Mercury program, but were cut from the program in July, 1959 due to budget constraints. The Atlas boosters required extra strengthening in order to handle the increased weight of the Mercury capsules beyond that of the nuclear warheads they were designed to carry. Little Joe was a solid-propellant booster designed specially for the Mercury program. The Titan missile was also considered for use for later Mercury missions, however the Mercury program was terminated before these missions were flown. The Titan was used for the Gemini program which followed Mercury


The "Mercury seven" astronauts pose with an Atlas model July 12, 1962.
The "Mercury seven" astronauts pose with an Atlas model July 12, 1962.

The first Americans to venture into space were drawn from a group of 110 military pilots chosen for their flight test experience and because they met certain physical requirements. Seven of those 110 became astronauts in April 1959. Six of the seven flew Mercury missions (Deke Slayton was removed from flight status due to a heart condition). Beginning with Alan Shepard's Freedom 7 flight, the astronauts named their own spacecraft, and all added "7" to the name to acknowledge the teamwork of their fellow astronauts

Mercury had seven prime astronauts, all former military test pilots, known as the Mercury Seven. NASA announced the selection of these astronauts on April 9, 1959.


Project Gemini:

Project Gemini was the second human spaceflight program in which the United States of America sent humans into space, between Projects Mercury and Apollo, during the years 1963-1966. Its objective was to develop techniques for advanced space travel, notably those necessary for Apollo, whose objective was to land men on the Moon. Gemini missions involved extravehicular activity and orbital maneuvers including rendezvous and docking.

Gemini was originally seen as a simple extrapolation of the Mercury program, and thus early on was called Mercury Mark II. The final program had little in common with Mercury and was in fact superior to even Apollo in some ways. (See Big Gemini.) This was mainly a result of its late start date, which allowed it to benefit from much that had been learned by that time on the Apollo project (which, despite its later launch dates, was actually begun before Gemini).

Its primary difference from Mercury was that the earlier spacecraft had all systems other than the reentry rockets sited within the capsule, nearly all of which had to be accessed through the astronaut's hatchway, while Gemini had many power, propulsion, and life-support systems in a detachable module like a huge bowl; many components in the capsule itself were reachable each through its own small access door. The original intention was for Gemini to use a paraglider instead of a parachute, and the crew to be seated upright controlling the forward motion of the craft before its landing. To facilitate this, the parachute cord does not just attach to the nose of the craft; there is an additional attachment point for balance near the heat shield. This cord is covered by a strip of metal between the doors. Early, short-duration missions had their electrical power supplied by batteries; later endurance missions had the first fuel cells in manned spacecraft.

The "Gemini" designation comes from the fact that each spacecraft held two men, as "gemini" in Latin means "twins". Gemini is also the name of the third constellation of the Zodiac and its twin stars, Castor and Pollux.

Unlike Mercury, which could only change its orientation in space, the Gemini capsule could alter its own orbit. It could also dock with other spacecraft--one of which, the Agena Target Vehicle, had its own large rocket engine which was used to perform large orbital changes. Gemini was the first American manned spacecraft to include an onboard computer, the Gemini Guidance Computer, to facilitate management and control of mission maneuvers. It was also unlike other NASA craft in that it used ejection seats, in-flight radar and an artificial horizon - devices borrowed from the aviation industry. Using ejection seats to push astronauts to safety was first employed by the Soviet Union in the Vostok craft manned by cosmonaut Yuri Gagarin.

The design for Gemini was developed by a Canadian, Jim Chamberlin, formerly of the Avro Arrow chief design studio. The main contractor was McDonnell who had lost out on main contracts for the Apollo Project. McDonnell sought to extend the program by proposing a Gemini craft could be used to fly a cislunar mission and even achieve a manned lunar landing earlier and at less cost than Apollo but these were rejected.

The Gemini program cost $5.4 billion in 1994 dollars. See NASA Budget.



The National Aeronautics and Space Administration (NASA) announced December 7, 1961, a plan to extend the existing manned space flight program by development of a two-man spacecraft. The program was officially designated Gemini on January 3, 1962.


The Gemini program was managed by the Manned Spacecraft Center, Houston, Texas, under direction of the Office of Manned Space Flight, NASA Headquarters, Washington, D.C, Dr. George E. Mueller, Associate Administrator of NASA for Manned Space Flight, served as acting director of the Gemini program. William C. Schneider, Deputy Director of Manned Space Flight for Mission Operations, served as Mission Director on all Gemini flights beginning with Gemini V.

The Manned Spacecraft Center Gemini effort was headed by Dr. Robert R. Gilruth, director of the Center, and Charles W. Matthews, Gemini Program Manager. The Gemini spacecraft was designed by Canadian Jim Chamberlin, who joined the Gemini Program in 1961 after being recruited by NASA shortly after the AVRO Arrow project was dismantled by the Canadian Diefenbaker government.


Project Apollo:

Project Apollo was a series of human spaceflight missions undertaken by the United States of America using the Apollo spacecraft and Saturn launch vehicle, conducted during the years 1961–1972. It was devoted to the goal of landing a man on the Moon and returning him safely to Earth within the decade of the 1960s. This goal was achieved with the Apollo 11 mission in July 1969. The program continued into the early 1970s to carry out the initial hands-on scientific exploration of the Moon, with a total of six successful landings. As of 2006, there has not been any further human spaceflight beyond low earth orbit. The later Skylab program and the joint American-Soviet Apollo-Soyuz Test Project used equipment originally produced for Apollo, and are often considered to be part of the overall program. The name Apollo, like earlier manned space-flight programs, was named after a god from classical civilizations, and comes from one of the Greek gods.


The Apollo Program was originally conceived late in the Eisenhower administration as a follow-on to the Mercury program, doing advanced manned earth-orbital missions. In fact, it became the third program, following Gemini. The Apollo Program was dramatically reoriented to an aggressive lunar landing goal by President Kennedy with his announcement at a special joint session of Congress on May 25, 1961:

"...I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth. No single space project in this period will be more impressive to mankind, or more important in the long-range exploration of space; and none will be so difficult or expensive to accomplish..." (Excerpt from "Special Message to the Congress on Urgent National Needs".[1])

Choosing a mission mode

Having settled upon the Moon as a target, the Apollo mission planners were faced with the challenge of designing a set of flights that would meet Kennedy's stated goal while minimizing risk to human life, cost and demands on technology and astronaut skill.

Three possible plans were considered.

Apollo configuration for Direct Ascent and Earth Orbit Rendezvous - 1961 (NASA)
Apollo configuration for
Direct Ascent and
Earth Orbit Rendezvous - 1961 (NASA)
  • Direct ascent: This plan was to boost a spaceship directly to the moon. The entire spacecraft would land on and return from the moon. This would have required a Nova rocket far more powerful than any in existence at the time.
  • Earth orbit rendezvous: This plan, known as Earth orbit rendezvous (EOR), would have required the launch of two Saturn V rockets, one containing the space ship and one containing fuel. The spaceship would have docked in earth orbit and be fueled with enough fuel to make it to the moon and back. Again, the entire spacecraft would have landed on the moon.
  • Lunar Surface Rendezvous: This would have required two spacecraft to be launched - the first one being an automated vehicle carrying propellants would land on the Moon, to be followed some time later by the 'manned' vehicle. Propellant would be transferred from the automated vehicle to the 'manned' vehicle before the 'manned' vehicle could return to Earth.
  • Lunar orbit rendezvous: This plan, which was adopted, is credited to John Houbolt and used the technique of 'Lunar Orbit Rendezvous' (LOR). The spacecraft was modular, composed of a 'Command/Service Module' (CSM) and a 'Lunar Module' (LM; originally Lunar Excursion Module {LEM}). The CSM contained the life support systems for the three man crew's five day round trip to the moon and the heat shield for their reentry to Earth's atmosphere. The LM would separate from the CSM in lunar orbit and carry two astronauts for the descent to the lunar surface, then back up to the CSM.

In contrast with the other plans, the LOR plan required only a small part of the spacecraft to land on the moon, thereby minimizing the mass to be launched from the moon's surface for the return trip. The mass to be launched was further minimized by leaving part of the LM (that with the descent engine) behind, on the moon.

Grumman Apollo LM
Apollo LM on lunar surface.
Apollo LM on lunar surface.
Role: Lunar landing
Crew: 2; CDR, LM pilot
Height: 20.9 ft 6.37 m
Diameter: 14 ft 4.27 m
Landing gear span: 29.75 ft 9.07 m
Volume: 235 ft3 6.65 m3
Ascent module: 10,024 lb 4,547 kg
Descent module: 22,375 lb 10,149 kg
Total: 32,399 lb 14,696 kg
Rocket engines
LM RCS (N2O4/UDMH) x 16: 100 lbf ea 441 N
Ascent propulsion system
(N2O4/Aerozine 50) x 1:
3,500 lbf ea 15.57 kN
Descent propulsion system
(N2O4/Aerozine 50) x 1:
9,982 lbf ea 44.4 kN
Endurance: 3 days 72 hours
Apogee: 100 miles 160 km
Perigee: surface surface
Spacecraft delta v: 15,387 ft/s
(10,491 mi/h)
4,690 m/s
(16,884 km/h)
Apollo LM diagram
Apollo LM diagram (NASA)
Apollo LM diagram (NASA)
Grumman Apollo LM

The Lunar Module itself was composed of a descent stage and an ascent stage, the former serving as a launch platform for the latter when the lunar exploration party blasted off for lunar orbit where they would dock with the CSM prior to returning to Earth. The plan had the advantage that since the LM was to be eventually discarded, it could be made very light, so the moon mission could be launched with a single Saturn V rocket. However, at the time that LOR was decided, some mission planners were uneasy at the large numbers of dockings and undockings called for by the plan.

To learn lunar landing techniques, astronauts practiced in the Lunar Landing Research Vehicle (LLRV), a flying vehicle that simulated (by means of a special, additional jet engine) the reduced gravity that the Lunar Module would actually fly in.


The Apollo program included eleven manned flights, designated Apollo 7 through Apollo 17, all launched from the Kennedy Space Center, Florida. Apollo 4 through Apollo 6 were unmanned test flights (officially there was no Apollo 2 or Apollo 3). The Apollo 1 designation was retroactively applied to the originally planned first manned flight which ended in a disastrous fire during a launch pad test that killed three astronauts, Virgil "Gus" Grissom, Edward White, and Roger B. Chaffee, in January 1967. The first of the manned flights employed the Saturn IB launch vehicle; the remaining flights all used the more powerful Saturn V. Two of the flights (Apollo 7 and Apollo 9) were Earth orbital missions, two of the flights (Apollo 8 and Apollo 10) were lunar orbital missions, and the remaining 7 flights were lunar landing missions (although one, Apollo 13, failed to land).

Apollo 7 tested the Apollo command and service modules (CSM) in Earth orbit. Apollo 8 tested the CSM in lunar orbit. Apollo 9 tested the lunar module (LM) in earth orbit. Apollo 10 tested the LM in lunar orbit. Apollo 11 achieved the first human lunar landing. Apollo 12 achieved the first lunar landing at a precise location. Apollo 13 failed to achieve a lunar landing, but succeeded in returning the crew safely to earth following a potentially disastrous in-flight explosion. Apollo 14 resumed the lunar exploration program. Apollo 15 introduced a new level of lunar exploration capability, with a long-stay-time LM and a lunar roving vehicle. Apollo 16 was the first manned landing in the lunar highlands. Apollo 17, the final mission, was the first to include a scientist-astronaut, and the program's first manned night launch.

Apollo Applications Program

In the speech which initiated Apollo, Kennedy declared that no other program would have as great a long-range effect on America's ambitions in outer space. Following the success of Project Apollo, both NASA and its major contractors investigated several post-lunar applications for the Apollo hardware. The "Apollo Extension Series", later called the "Apollo Applications Program", proposed at least ten flights. Many of these would use the space that the lunar module took up in the Saturn rocket to carry scientific equipment.

One plan involved using the Saturn IB to take the Command/Service Module (CSM) to a variety of low-earth orbits for missions lasting up to 45 days. Some missions would involve the docking of two CSMs, and transfer of supplies. The Saturn V would be necessary to take it to polar orbit, or sun-synchronous orbit (neither of which has yet been achieved by any manned spacecraft), and even to the geosynchronous orbit of Syncom 3, a communications satellite not quite in geostationary orbit. This was the first functioning communications satellite at that now-common great distance from the Earth, and it was small enough to be carried through the hatch and taken back to Earth for study as to the effects of radiation on its electronic components in that environment over a period of years. A return to the moon was also planned, this time to orbit for a longer time to map the surface with high-precision equipment. This mission would not include a landing.

Of all the plans only two were implemented; the Skylab space station (May 1973 – February 1974), and the Apollo-Soyuz Test Project (July 1975). Skylab's fuselage was constructed from the second stage of a Saturn IB, and the station was equipped with the Apollo Telescope Mount, itself based on a lunar module. The station's three crews were ferried into orbit atop Saturn IBs, riding in CSMs; the station itself had been launched with a modified Saturn V. Skylab's last crew departed the station on February 8, 1974, whilst the station itself returned prematurely to Earth in 1979, by which time it had become the oldest operational Apollo component.

The Apollo-Soyuz Test Project involved a docking in Earth orbit between an un-named CSM and a Soviet Soyuz spacecraft. The mission lasted from July 15 to July 24, 1975. Although the Soviet Union continued to operate the Soyuz and Salyut space vehicles, NASA's next manned mission would not be until STS-1 on April 12, 1981.

End of the program

Unflown command module CM-007 in a museum
Unflown command module CM-007 in a museum

Originally three additional lunar landing missions had been planned, as Apollo 18 through Apollo 20. In light of the drastically shrinking NASA budget and the decision not to produce a second batch of Saturn Vs, these missions were cancelled to make funds available for the development of the Space Shuttle, and to make their Apollo spacecraft and Saturn V launch vehicles available to the Skylab program. Only one of the Saturn Vs was actually used; the others became museum exhibits.

Another excerpt from Kennedy's Special Message to Congress:

"I believe we should go to the moon. But I think every citizen of this country as well as the Members of the Congress should consider the matter carefully in making their judgment, to which we have given attention over many weeks and months, because it is a heavy burden, and there is no sense in agreeing or desiring that the United States take an affirmative position in outer space, unless we are prepared to do the work and bear the burdens to make it successful. If we are not, we should decide today and this year.
Lunar lander LM2 at the National Air and Space Museum
Lunar lander LM2 at the National Air and Space Museum
"This decision demands a major national commitment of scientific and technical manpower, material and facilities, and the possibility of their diversion from other important activities where they are already thinly spread. It means a degree of dedication, organization and discipline which have not always characterized our research and development efforts. It means we cannot afford undue work stoppages, inflated costs of material or talent, wasteful interagency rivalries, or a high turnover of key personnel.
"New objectives and new money cannot solve these problems. They could in fact, aggravate them further--unless every scientist, every engineer, every serviceman, every technician, contractor, and civil servant gives his personal pledge that this nation will move forward, with the full speed of freedom, in the exciting adventure of space." (Excerpt from "Special Message to the Congress on Urgent National Needs")

Reasons for Apollo

The Apollo program was at least partly motivated by psycho-political considerations, in response to persistent perceptions of American inferiority in space technology vis-a-vis the Soviets, in the context of the Cold War and the Space Race. In this respect it succeeded brilliantly. In fact, American superiority in manned spaceflight was achieved in the precursory Gemini program, even before the first Apollo flight.

The Apollo program stimulated many areas of technology. The flight computer design used in both the lunar and command modules was, along with the Minuteman Missile System, the driving force behind early research into integrated circuits. The fuel cell developed for this program was the first practical fuel cell. Computer controlled machining (CNC) was pioneered in fabricating Apollo structural components.

Many astronauts and cosmonauts have commented on the profound effects that seeing earth from space has had on them. One of the most important legacies of the Apollo program was the now-common, but not universal view of Earth as a fragile, small planet, captured in the photographs taken by the astronauts during the lunar missions. The most famous of these photographs, taken by the Apollo 17 astronauts, is "The Blue Marble." These photographs have also motivated many people toward environmentalism and space colonization.

Miscellaneous information

  • The cost of the entire Apollo program: USD $25.4 billion -1969 Dollars ($135-billion in 2005 Dollars). See NASA Budget. (Includes Mercury, Gemini, Ranger, Surveyor, Lunar Orbitar, Apollo programs.) Apollo spacecraft and Saturn rocket cost alone, was about $ 83-billion 2005 Dollars (Apollo spacecraft cost $ 28-billion (CS/M $ 17-billion; LM $ 11-billion), Saturn I, IB, V costs about $ 46-billion 2005 dollars).
  • Amount of moon material brought back by the Apollo program: 381.7 kg (841.5 lb). Most of the material is stored at the Lunar Receiving Laboratory in Houston.



The Surveyor Program comprised unmanned spaceflights to the Moon, with soft landings, without returning (although Surveyor 6 became the first spacecraft to lift off the moon).

It was initiated and carried out to demonstrate the feasibility of soft landing on the Moon. This was done in preparation for the Apollo Program. The program was implemented by NASA's Jet Propulsion Laboratory (JPL) and performed several other services beyond its primary goal. The ability for a spacecraft to make midcourse corrections was demonstrated, and the landers carried instruments to assist with evaluation of the suitability of their landing sites for manned Apollo landings.

The Surveyor Shovel was a project to determine the composition of the Moon's surface. The robotic shovel was designed to dig at the surface and determine the composition of the materials. Before this project, it was unknown how deep the dust on the moon was. If the dust were to be too deep, then no Astronaut could land. Today, of course, we now know that the Astronauts could walk the face of the Moon, as evidenced by the photographs of their footprints.

There were seven Surveyor missions, five were successful. Surveyor 2 and 4 failed. Each consisted of a single unmanned spacecraft designed and built by Hughes Aircraft Company.

Mission list

Apollo 12 landed within walking distance of the Surveyor 3 landing site.



Clementine Mission __ "The Clementine spacecraft successfully mapped the Moon with 4 cameras (UVVIS 415-1000nm; NIR 1100-2789 nm; HI-RES 415-750 nm; LWIR 9 microns) over the period February through May 1994. Using the UVVIS and NIR cameras the entire Moon was mapped at a resolution of 125-250 m/pixels. From these new data it will be possible to map the mineralogy (rock types) of the entire Moon, a truly unprecedented feat in the history of planetary exploration. In addition to the multispectral mapping cameras the Clementine spacecraft also carried a laser altimeter. The laser altimetry data will make possible the first ever uniform global lunar topographic map."  You will find information and images. - illustrated - From USGS - 

Earth and Moon Viewer __ You can view the Moon from the Earth, Sun, night side, above named formations on the lunar surface. or as a map showing day and night. You can also make expert and custom images of the Moon. A related document compares the appearance of the Moon at perigee and apogee, including an interactive Perigee and Apogee Calculator. - illustrated - From John Walker - 

The Earth's Moon __ A good overview of our moon with sections for the beginner, intermediate and advanced student. - illustrated - From University of Michigan - 

Exploring the Moon: Apollo Missions __ "This document is meant to provide an introduction to the lunar exploration missions of the Apollo program. It provides information at a general level. It
also offers links to more detailed information at this and other sites." - illustrated - From LPI - 

Historical Lunar Data Archive __ "Presented here are variety of data selected from a collection of data commonly referred to as the Lunar Consortium Data. This pre-Clementine data set consists of products derived from Apollo, Lunar Orbiter, Galileo, and Zond 8 missions. Select data collected from Earth-based observations are also included as part of this collection." - illustrated - From USGS - 

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