Most important milestones in space exploration

The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States during the Cold War. The Soviet space program achieved many of the first milestones in the exploration of outer space in the 1960’s and the early 1970’s while the United States responded with putting the first men on the moon.

Not many know that first steps in space exploration were undertaken by German scientists during World War II, when they put a man-made object, the V-2 rocket, into space on October 3, 1942. The first images of Earth from space came in 1946, after the United States used German scientists and their captured rockets for research. However, it all truly started in 1957...

- October 4, 1957: Soviet Union launches Sputnik 1, the first artificial satellite to be put into Earth’s orbit. It transmitted radio signals to Earth only for a short time, but it was a major accomplishment. It marked the beginning of the Space Age and it was the first in a series of satellites known as the Sputnik program. Successful Sputnik launch and the failure of the first two U.S. launch attempts ignited “Sputnik crisis” in the United States - the name given to the American reaction to the success of Sputnik program, which became a key event during the Cold War.

- November 3, 1957: The Soviet dog Laika, housed in a pressurized container on board of Sputnik 2, became the first animal in orbit. Laika lived 8 days until the food supply ran out.

- April 12, 1961: Soviet cosmonaut Yuri Gagarin became the first human to travel into space on board of the Vostok 1 spacecraft. Gagarin completed orbit around Earth in 108 minutes and reached altitudes of 112 to 203 miles (180-327 km). Yuri became an instant celebrity and his achievement was heavily promoted by the Soviet Union as the milestone in winning the “Space Race”.

- May 5, 1961: Astronaut Alan Shepard became the first American to be launched into space on board of Freedom 7. The suborbital flight, which was part of the Mercury Project, lasted only 15 minutes and 28 seconds.

- February 20, 1962: Astronaut John H. Glenn became the first American to orbit Earth aboard Friendship 7, also part of the Mercury project. Glenn completed 3 orbits and the flight time was 3 hours and 56 minutes.

- June 6, 1963: Soviet cosmonaut Valentina Tereshkova became the first woman in space when she piloted Vostok 6. She orbited Earth 48 times during her 3-day mission. She performed various tests on herself to collect data on the female body's reaction to spaceflight.

- November 28, 1964: NASA’s spacecraft Mariner 4, intended for planetary exploration in a flyby mode, was launched. It performed the first successful flyby of Mars and, on June 14, 1965, delivered the first pictures of the Martian surface. These were the first images of another planet ever returned from deep space. They showed a cratered, seemingly dead world, which largely changed the view of the scientific community on life on Mars. Communications with Mariner 4 were terminated on December 21, 1967.

- March 18, 1965: Cosmonaut Alexei Leonov became the first human to conduct a space walk. He was outside the Voshkod 2 spacecraft for 12 minutes and 9 seconds, connected to the craft by a 5.35-meter tether. He barely made it back inside the capsule. At the end of the spacewalk, his spacesuit had inflated in the vacuum of space to the point where he could not re-enter the airlock and he had to open a valve to allow some of the suit's pressure to bleed off.

- February 3, 1966: Soviet spacecraft Luna 9 became the first spacecraft to soft-land on the Moon after a 250,000-mile trip (402,000 km). It transmitted pictures of the Moon’s surface back to Earth. Importantly, the mission demonstrated that the Moon’s surface was strong enough to support the weight of a large spacecraft.

- October 18, 1967: The Soviet probe Venera 4 landed on Venus and successfully performed in-place chemical analysis of the Venusian atmosphere. The first direct measurements showed that Venus was extremely hot, the atmosphere was far denser than expected, and that Venus had lost most of its water long ago.

- July 20, 1969: NASA’s spaceflight Apollo 11 delivered the first humans to the Moon. Neil Armstrong and Edwin Aldrin, Jr. landed in the Sea of Tranquillity while Michael Collins orbited above in the command ship, Columbia. On July 21, Armstrong and Aldrin became the first human beings to set foot on another world. Their landing craft, Eagle, spent 21 hours and 31 minutes on the Moon. The three astronauts returned to Earth with 47.5 pounds (21.5 kg) of lunar rocks and landed in the Pacific Ocean on July 24. The mission has been considered a major accomplishment in the history of space exploration and marked the strong return of the United States to the “Space Race” with the Soviet Union, who put the first man into space in 1961.

- April 19, 1971: Soviet Union launched the first space station, the Salyut 1. It remained in orbit till May 28, 1973. On June 6, Soyuz 11 successfully docked with the station and cosmonauts G.T. Dobrovolsky, V.N. Volkov, and V.I. Patsayev became the first manned occupancy of an orbital station. Tragically, on June 29, the Cosmonauts died upon Soyuz 11's reentry.

- July 15, 1975: American Apollo 18 and Soviet Soyuz 19 docked in what became the first international spacecraft rendezvous. Known as the Apollo-Soyuz Test Project, this important mission proved that U.S. and Soviet crews could work together successfully in space.

- August-September, 1977: Voyager 1 and Voyager 2 spacecrafts left Earth to study the outer Solar System eventually interstellar space. The Voyager program has operated for almost 34 years and the spacecrafts continuously receive routine commands and transmit data back to the Deep Space Network. They are the first probes to leave the Solar System and the farthest man-made objects from Earth. They accomplished the initial mission by reaching Jupiter and Saturn between 1979 and 1981, and are now in extended mission, tasked with locating and studying the boundaries of the Solar System, including the Kuiper belt, the heliosphere, and interstellar space.

- April 12, 1981: NASA launched its Space Shuttle program, when Robert L. Crippen and John W. Young made the mission aboard the space shuttle Columbia to test the spacecraft’s systems.

- February 19, 1986: Soviet, and later Russian, Mir (Russian for “Peace” or “World”) space station was launched. In 1995, the first American shuttle, Space Shuttle Atlantis, rendezvoused with Mir during a ten-day mission for cosmonauts to be transferred to and from Atlantis. Mir operated in low Earth orbit till March 21, 2001. It was the largest artificial satellite orbiting the Earth at the time. Now, the record is held by the International Space Station.

- April 24, 1990: Space Shuttle Discovery carried the Hubble Space Telescope into orbit. It was named after the astronomer Edwin Hubble and built by NASA, with contributions from the European Space Agency. It’s operated by the Space Telescope Science Institute. The telescope was successfully deployed in 1990, but was found to contain a seriously flawed primary mirror that had been ground incorrectly, as part of a sphere instead of as part of a parabola. It resulted in fuzzy images. The telescope was restored in 1993, after a servicing mission added a corrective lens. The Hubble telescope is expected to function until at least 2014. Its successor, the James Webb Space Telescope, is due to be launched by 2018.

- March 22, 1995: Cosmonaut Valeriy Polyakov set a space endurance record. He returned to Earth after a 438-day mission aboard Russian space station Mir.

- November 20, 1998: First piece of the International Space Station (ISS), the Russian-built Zarya Control Module, was launched from the Baikonur Cosmodrome. On-orbit construction is scheduled for completion by 2012, and ISS is expected to remain in operation until at least 2020, and potentially to 2028. It’s the largest space station ever constructed and can be seen from Earth with the naked eye. In 2000, the first people took up residence at the ISS, staying there for several months. These were Bill Shepherd and cosmonauts Yuri Gidzenko and Sergei Krikalev.

- February 12, 2001: The Near Earth Asteroid Rendezvous (NEAR) spacecraft made the first landing on an asteroid. The asteroid was named Eros and it was an S-class asteroid, approximately 20 miles (33 km) and 8 miles (13 km) wide. NEAR had been in orbit around Eros since February 14, 2000. Amusingly, the Valentine's Day arrival date seemed very appropriate for an asteroid named after the Greek god of love. NEAR was never designed to land on the asteroid and the landing was a last minute idea to get some additional data as the spacecraft was nearing the end of its mission.

- March 11, 2001: U.S. Shuttle astronauts Susan Helms and Jim Voss set a spacewalk record as they installed the Leonardo module aboard the International Space Station. The total time spent in space was 8 hours and 56 minutes.

- April 28, 2001: Italian American engineer and multimillionaire, Dennis Tito, became the first tourist to fly into space. His 20-million dollar offer was rejected by the United States, but was later welcomed by the Russian space program. A Soyuz space capsule delivered the space tourist and the Russian crew to the International Space Station. Tito spent 7 days, 22 hours, 4 minutes in space and orbited Earth 128 times. He performed several scientific experiments in orbit that he said would be useful for his company and business.

- June 21, 2004: A privately financed and built spacecraft known as SpaceshipOne made history as the first manned private spacecraft to be flown into space. SpaceShipOne was built by famed aerospace designer Burt Rutan of Mojave-based Scaled Composites, with financial backing of approximately $25 million from Microsoft Corporation co-founder Paul Allen.

- July 4, 2005: NASA’s Deep Impact space probe made the first impact with the comet. It slammed into a comet Tempel 1 at a speed of 10.3 kilometers (6.3 miles) per second. The successful collision with the comet's nucleus generated a large and bright dust cloud, which unexpectedly obscured the view of the impact crater for the probe's mothership set to photograph the impact and analyze the resulting debris. Among the many discoveries, water ice was found within the comet and the photographs showed the comet to be more dusty and less icy than had been expected.

- March 6, 2009: NASA’s spacecraft Kepler, named after German astronomer Johannes Kepler, launched on a mission to discover Earth-like planets rbiting other stars. The mission was specifically designed to survey a portion the Milky Way galaxy to search for dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets. The mission was planned to last for at least 3.5 years.

- February 11, 2010: NASA’s space telescope, the Solar Dynamics Observatory (SDO), was launched to observe the Sun. SDO's goal is to understand the Sun's influence on Earth and near-Earth space by studying the solar atmosphere. It’ll investigate how the Sun's magnetic field is generated and structured, how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance. The primary mission is scheduled to last 5 years and 3 months, with expendables expected to last for 10 years. SDO has been called the “Hubble for the sun” and it’s expected to transform solar physics in the same way the Hubble Space Telescope has transformed astronomy and cosmology. First images from SDO's turned out to be so breathtaking that even seasoned observers were stunned.

- July 8, 2011: NASA’s Space Shuttle program retired with the final launch of Atlantis. Space shuttles: Discovery, Endeavour, Atlantis, and the test shuttle Enterprise will end up in various museums in 2012. The total cost of the shuttle program had been $145 billion as of early 2005, and as of 2011, had risen to $196 billion. According to NASA, the average cost to launch a Space Shuttle as of 2011 is about $450 million per mission. The retirement of the Space Shuttle program happens as NASA slowly concludes the 30-year old program in favor of interplanetary travel. The focus of space exploration is switching towards developing technology to enable crewed missions beyond low Earth orbit, envisioning extending the operation of the International Space Station beyond 2020, and transferring the development of launch vehicles for human crews from NASA to the private sector.