Interplanetary probes

ASTRONOMY AND ASTRONAUTICS IN THE TWENTIETH CENTURY: INTERPLANETARY PROBES

In the early days of the Space Age, soon after the first artifact in space (the Soviet Sputnik 1, in 1957), the first living being (the dog Laika), the first discovery in outer space (the Van Allen radiation belts in 1958), the next logical step seemed to be trying to make something reach the Moon.

The first object built by humans which managed to leave once and for all the Earth's gravity (the first "artificial planet") was the Lunik 1, in 1959. It was launched towards the Moon (it missed the target) but relayed important details about the environment between the Earth and its natural satellite. Shortly thereafter, the Soviets launched a sister spacecraft, the Lunik 2, and yes this made a perfect trip to shatter itself against the lunar surface. For the first time humans could touch, albeit indirectly, another celestial body. To the scientific and historical importance was united the political importance of the achievement, demonstrated by the fact that an important part of the small payload of the spacecraft was Soviet medals and badges: we were in the Cold War. Even more spectacular results came through the advanced Lunik 3, when it photographed for the first time the far side of the Moon, something never before seen by humans.

In the early 60's the U. S. were about to begin a much more ambitious program. The goal for the end of the decade was nothing less than putting a man on the Moon and bring him safely back to Earth: it was the Apollo program. To achieve it, it was imperative to have a previous knowledge of the Moon. Three robotics projects emerged: the Ranger, basically free-fall spacecraft, which would film with TV cameras the last few minutes before the fatal crash; the Surveyor, landing craft that would test equipment and techniques and would analyze lunar soil to see whether it was possible or not the landing of large crewed spacecraft; and the Lunar Orbiter, that would make Moon maps much more detailed than previous ones in order to choose the best landing sites. All these steps were carried out with great success.

The Soviets continued their programs of spacecraft to the Moon, and sometimes even stood in front of the U. S., for example with the first successful soft landing (Lunik 9) and the first artificial satellite around another world (Lunik 10), but in generally failed to keep pace with the U. S.. The latter put six large crewed ships with a dozen astronauts between 1969 and 1972 in the lunar soil, finishing the work begun by Ranger. The Soviets had to settle for far less spectacular results, but they also have their importance, e.g. the first (and until now only) samples from another world brought by remote control (Lunik 16), and the first remote-control cars to roll on an alien surface (Lunokhod).

The true era of planetary exploration began in 1962, with the launch of the U .S. Mariner 2 toward the nearest neighbor, Venus. This spacecraft confirmed the suspicion that the surface of Venus is hotter than a kitchen oven, and not least, the robotic spacecraft managed to survive several months in the hostile interplanetary environment and transmit information to Earth from many millions of kilometers away. A more advanced brother, equipped with cameras, showed that there are no gaps between the clouds, and then it came the time to study them with a descent spacecraft. The Soviet Venera 4 became the first object constructed by humans to enter the atmosphere of another planet, but it did not got to the floor because it was overwhelmed by the amazing atmospheric pressure of Venus.

Meanwhile, the new spacecraft of the Mariner series were headed the other way, toward Mars. The first pictures showed a uninteresting surface that some people thought similar to the Moon's surface, but the revolution came in 1971, with Mariner 9. First artificial satellite from Earth around another planet, it studied Mars continuously sending more than 7000 photographs, in which the first evidence that Mars has not always been a desert appeared: dry riverbeds. Other impressive findings were the largest canyon in the Solar System (now called Mariner Valley) and the highest mountains: volcanoes up to 26 km high. It also showed that the small moons of Mars are probably captured asteroids.

In the early years of the 70's travels to still further afield began: Mercury and, beyond the main belt of asteroids, Jupiter and Saturn. The Pioneer 10 and 11 are also the first spacecraft that, after a preliminary reconnaissance of these gas giants, continued traveling through space to leave the Solar System. They are the first interstellar spacecraft launched by Humankind. As a signature of its builders, they carry gold-plated aluminum plaques with a drawing of a man and a woman, a special code that is expected to be understood by any intelligent being and a map of the position of the Sun and Earth in the Galaxy with the time when the spacecraft were launched.

This first phase of the use of spacecraft is characterized by the large number of launches (in part because of the space race during the Cold War) but also by the large number of failures, because the technology was still in its infancy. After the arrival of humans to the Moon, by virtue of the technological breakthroughs achieved, especially in the area of electronics and the size of the rocket, a second generation of interplanetary probes appears: big, heavy, equipped with payloads of very refined instruments, with extremely high budgets and with missions lasting up to decades. Again the first are launched to the closest neighbor, Venus. The Soviet Venera series continues to be refined and manage landings with transmissions of images and other important data from the surface, over the years 1970s and 1980s. The U. S. launch missions for the detailed study of the atmosphere, and using radar, make the first high-quality maps of the permanently overcast surface. The height of sophistication of this technique comes at the end of the 80s, with the probe Magellan with a radar employing the technique of Synthetic Aperture Radar (more expensive than the spacecraft itself) that makes images equivalent to high-quality photographs.

The mission that symbolizes the establishment of this new era is undoubtedly the Viking, to Mars. The U. S. pass for the first time the barrier of 1000 million dollars for a non-crewed mission with spacecraft so advanced that a thousand people are needed to monitor the operation. Fed by even nuclear batteries, they perform experiments for years since 1976, both from orbit and from the ground of the Red Planet. Undoubtedly the most ambitious experiments are those seeking signs of life in the Martian soil. The results of these biological experiments, appear contradictory and nothing conclusive.

The most successful interplanetary probe in History is from this era. Shortly after Viking, the Voyager probes are launched, a reduced version of a project to take advantage of a rare conjunction of planets to perform a "Grand Tour" by the outer planets. With the most modern and sophisticated with regard to sensors and computers the twin spacecraft study in unprecedented detail Jupiter and Saturn (Voyager 1 and 2), and also Uranus and Neptune (Voyager 2), not only re-writing entire scientific books when passing by these distant worlds while filling entire shelves of new information: virtually everything we know about that part of the Solar System, we ought it to Voyager, which working much longer than originally foreseen, continue until today sending information while leaving the Solar System towards the stars. Gold records with songs, messages and images from Earth are traveling with them, in the hope of being found and deciphered someday by some civilization that we can not even imagine.

The last descendants of these spacecraft are the Galileo, managed by the United States, launched in 1989 to study for at least 2 years (which in the end were almost 8 years) the system of Jupiter, and the Cassini-Huygens, an international project that, with a price of 3000 million dollars is also the most expensive and sophisticated in History. Launched in 1997, arrived at Saturn in 2004 and studied this system over 4 years, already renewed.

In more recent times comes a new vision about space exploration. On the one hand, new countries (especially those in Western Europe and Japan) desire to explore interplanetary space, in an affordable way of course. Moreover, the United States of America, the only surviving superpower, is seeking to reduce in the new missions the investment risks. Rather than build and launch a single spacecraft of thousands of millions of dollars with 20 different scientific instruments, it is deemed wiser to launch four spacecraft with 5 very specific instruments, at a lower price and with much less risk of losing the entire mission if any failure happens in a critical system.

An interest in new objects in the Solar System also surge. Missions like the encounters with comet Halley in 1986, which had as main protagonist the Giotto probe of the European Space Agency, show that small spacecraft and international cooperation instead of confrontation also get spectacular results. Currently, missions to study the Sun, smaller bodies such as comets and asteroids and a renewed interest in Mars follow this philosophy.

Despite increasingly reduced budgets, the role of interplanetary probes as research tools are still irreplaceable. In the new decades of the 21st century, we expect a more active participation of new explorer nations, systematic missions to the more scientifically interesting objects, and travels for the first time to places that have not yet been explored, such as the trans-Neptunian Pluto, in the depths of the System Solar.

CHRONOLOGY OF PLANETARY EXPLORATION

THE PIONEERING MISSIONS TO THE MOON

Lunik 1 - 1959 - Moon - Flyby

Lunik 2 - 1959 - Moon - Impact

Lunik 3 - 1959 - Moon - Flyby

Ranger 7 - 1964 - Moon - Impact

Ranger 8 - 1965 - Moon - Impact

Ranger 9 - 1965 - Moon - Impact

Lunik 9 - 1966 - Moon - Lander

Lunik 13 - 1966 - Moon - Lander

Lunik 10 - 1966 - Moon - Orbiter

Lunik 11 - 1966 - Moon - Orbiter

Lunik 12 - 1966 - Moon - Orbiter

Lunik 14 - 1968 - Moon - Orbiter

Surveyor 1 - 1966 - Moon - Lander

Surveyor 3 - 1967 - Moon - Lander

Surveyor 5 - 1967 - Moon - Lander

Surveyor 6 - 1967 - Moon - Lander

Surveyor 7 - 1968 - Moon - Lander

Lunik 16 - 1970 - Moon - Samples

Lunik 20 - 1972 - Moon - Samples

Lunik 24 - 1976 - Moon - Samples

Lunik 17 / Lunokhod 1 - 1970 - Moon - Lander / Rover

Lunik 21 / Lunokhod 2 - 1973 - Moon - Lander / Rover

OTHER PIONEERING MISSIONS TO THE MOON

Pioneer 4 - 1959 - Moon - Flyby

Zond 3 - 1965 - Moon - Flyby

Explorer 35 (IMP-E) - 1967 - Moon - Orbiter

Zond 5 - 1968 - Moon - Circumlunar and return

Zond 6 - 1968 - Moon - Circumlunar and return

Lunik 15 - 1969 - Moon - Samples (Failed, orbiter)

Zond 7 - 1969 - Moon - Circumlunar and return

Zond 8 - 1970 - Moon - Circumlunar and return

Lunik 19 - 1971 - Moon - Orbiter

Explorer 49 (RAE-B) - 1973 - Moon - Orbiter / Radio Astronomy

Lunik 22 - 1974 - Moon - Orbiter

THE PIONEERING INTERPLANETARY MISSIONS

Mariner 2 - 1962 - Venus - Flyby

Mariner 5 - 1967 - Venus - Flyby

Venera 4 - 1967 - Venus - Descent

Venera 5 - 1969 - Venus - Descent

Venera 6 - 1969 - Venus - Descent

Mariner 4 - 1964 - Mars - Flyby

Mariner 6 - 1969 - Mars - Flyby

Mariner 7 - 1969 - Mars - Flyby

Mariner 9 - 1971 - Mars - Orbiter

Mariner 10 - 1973 - Venus and Mercury - Flyby

OTHER PIONEERING INTERPLANETARY MISSIONS

Pioneer 5 - 1960 - Interplanetary Environment

Mars 1 - 1962 - Mars - Flyby with failure

Zond 1 - 1964 - Interplanetary Environment

Venera 3 - 1965 - Venus - Descent with failure

Pioneer 6 - 1965 - Interplanetary Environment

Pioneer 7 - 1966 - Interplanetary Environment

Pioneer 8 - 1967 - Interplanetary Environment

Pioneer 9 - 1968 - Interplanetary Environment

Venera 7 - 1970 - Venus - Descent and landing

Mars 2 - 1971 - Mars - Orbiter / Lander (Failed)

Mars 3 - 1971 - Mars - Orbiter / Lander with failure

Venera 8 - 1972 - Venus - Landing

Mars 4 - 1973 - Mars - Orbiter (Failed, flyby)

Mars 5 - 1973 - Mars - Orbiter

Mars 6 - 1973 - Mars - Lander (Failed)

Mars 7 - 1973 - Mars - Lander (Failed, flyby)

Pioneer 10 - 1972 - Jupiter - Flyby

Pioneer 11 - 1973 - Jupiter and Saturn - Flyby

THE BIG PROBES

Venera 9 - 1975 - Venus - Orbiter / Lander

Venera 10 - 1975 - Venus - Orbiter / Lander

Pioneer Venus 1 - 1978 - Venus - Orbiter

Pioneer Venus 2 - 1978 - Venus - Descent, multiple probe

Magellan - 1989 - Venus - Orbiter

Viking Orbiter 1 / Viking Lander 1 - 1975 - Mars - Orbiter / Lander

Viking Orbiter 2 / Viking Lander 2 - 1975 - Mars - Orbiter / Lander

Voyager 2 - 1977 - Jupiter, Saturn, Uranus and Neptune - Flyby

Voyager 1 - 1977 - Jupiter and Saturn - Flyby

Galileo - 1989 - Jupiter - Orbiter / Descent

Cassini / Huygens - 1997 - Saturn - Orbiter / Descent

OTHER BIG PROBES

Venera 11 - 1978 - Venus - Flyby / Lander

Venera 12 - 1978 - Venus - Flyby / Lander

Venera 13 - 1981 - Venus - Flyby / Lander

Venera 14 - 1981 - Venus - Flyby / Lander

Venera 15 - 1983 - Venus - Orbiter

Venera 16 - 1983 - Venus - Orbiter

Vega 1 - 1984 - Venus and comet 1P/Halley - Flyby / Lander / Balloons and flyby

Vega 2 - 1984 - Venus and comet 1P/Halley - Flyby / Lander / Balloons and flyby

Phobos 1 - 1988 - Mars - Orbiter (Failed) / Landing on Phobos (Failed)

Phobos 2 - 1988 - Mars - Orbiter / Landing on Phobos (Failed)

THE NEW EXPLORERS

ICE (ISEE-3) - 1978 - Solar research and comets 21P/Giacobini-Zinner and 1P/Halley - Flyby

Sakigake - 1985 - Comet 1P/Halley - Flyby

Giotto -1985 - Comets 1P/Halley and 26P/Grigg-Skjellerup - Flyby

Suisei - 1985 - Comet 1P/Halley - Flyby

SOHO - 1995 - Solar research

NEAR-Shoemaker - 1996 - Asteroid (433) Eros - Orbiter, landing

Mars Global Surveyor - 1996 - Mars - Orbiter

Mars Pathfinder / Sojourner - 1996 - Mars - Lander / Rover

Nozomi - 1998 - Mars - Orbiter (Failed, flyby)

Lunar Prospector - 1998 - Moon - Orbiter

Deep Space 1 - 1998 - Asteroid (9969) Braille and comet 19P/Borrelly - Flyby

Stardust - 1999 - Comet 81P/Wild 2 - Samples

OTHER NEW EXPLORERS

Helios 1 - 1974 - Solar research

Helios 2 - 1974 - Solar research

Hiten - 1990 - Moon - Flyby / Orbiter

WIND - 1994 - Solar research

Clementine - 1994 - Moon - Orbiter

ACE - 1997 - Solar research

21st CENTURY

Genesis - 2001 - Solar Wind - Samples

2001 Mars Odyssey - 2001 - Mars - Orbiter

Hayabusa - 2003 - Asteroid (25143) Itokawa - Landing and samples

SMART 1 - 2003 - Moon - Orbiter

Spirit - 2003 - Mars - Rover

Opportunity - 2003 - Mars - Rover

Mars Express / Beagle 2 - 2003 - Mars - Orbiter / Lander (Failed)

Rosetta / Philae - 2004 - Comet 67P/Churyumov-Gerasimenko - Orbiter / Lander

Deep Impact - 2005 - Comet 9P/Tempel 1 and 103P/Hartley 2 - Meeting / Impact

MESSENGER - 2004 - Mercury - Orbiter

Mars Reconnaissance Orbiter - 2005 - Mars - Orbiter

Venus Express - 2005 - Venus - Orbiter

New Horizons - 2006 - Pluto and trans-Neptunian object (486 958) 2014 MU₆- Flyby

Phoenix - 2007 - Mars - Lander

Kaguya / Ouna / Okina - 2007 - Moon - Constellation of orbiters

Dawn - 2007 - Asteroid (4) Vesta and (1) Ceres - Orbiter

Chang'e 1 - 2007 - Moon - Orbiter

Chandrayaan 1 / MIP - 2008 - Moon - Orbiter / Impact

Kepler - 2009 - Extrasolar research

Lunar Reconnaisance Orbiter - 2009 - Moon - Orbiter

LCROSS - 2009 - Moon - Impact

Akatsuki - 2010 - Venus - Orbiter (Failed, flyby)

Chang'e 2 - 2010 - Moon - Orbiter

Juno - 2011 - Jupiter - Orbiter

GRAIL - 2011 - Moon - Orbiter

Curiosity - 2011 - Mars - Rover

LADEE - 2013 - Moon - Orbiter

Mangalyaan - 2013 - Mars - Orbiter

MAVEN - 2013 - Mars - Orbiter

Chang'e 3 / Yutu - 2013 - Moon - Lander / Rover

Chang'e 5 T-1 - 2014 - Moon - Circumlunar and return / Orbiter

Hayabusa 2 - 2014 - Asteroid (162 173) Ryugu - Sample return

PROCYON - 2014 - Asteroid 2000 DA₁₀₇

Trace Gas Orbiter / Schiaparelli - 2016 - Mars - Orbiter / Lander

OSIRIS-REx - 2016 - Asteroid (101 955) Bennu - Sample return

InSight - 2018 - Mars - Lander

Queqiao - 2018 - Moon - Relay Satellite

Parker - 2018 - Sun / Venus - Solar research/ Flybay

BepiColombo - 2018 - Mercury - Two Orbiters

Chang'e 4 - 2018 - Moon - Lander / Rover

Beresheet - 2019 - Moon - Lander (Failed)

Chandrayaan 2 - 2019 - Moon - Orbiter / Lander (Failed)

Solar Orbiter -2020 - Sol / Venus - Solar Research / Flyby

Hope - 2020- Mars - Orbiter

Tianwen 1 - 2020- Mars - Orbiter / Lander / Rover

Perseverance - 2020- Mars - Rover / Rotorcraft

Aldo Loup.

From a lecture given at USP, originally on 11 November 2000. Originally published by USP, from a document dated 26 January 2001. Photo: The most successful spacecraft in History were probably the twin Voyager 1 and Voyager 2, the findings of which rewrote entire books about the Solar System. Credit: Courtesy NASA / JPL-Caltech.