Space Exploration - Robotic Missions

While the manned space program of the 1960’s was exciting, the unmanned program was scientifically fruitful. Certainly, the US military launched a large number of satellites for various defense purposes, but these missions have become declassified and the collected data made available to the astronomy community, often yielding useful information. The purpose of this webpage is to introduce you to the history of unmanned space missions. While not as exotic in terms of national interest and emotional appeal, the satellites were able to go where people could not, stay our longer without the need for food, water, and air ... to say nothing about keeping warm, and once the missions were completed, either be sent crashing into the sun or planet, or else simply keep on going out, and out, and out some more. This page is much more simple on coverage, and you will be directed to connecting links for additional browsing.
At the Nobel Conference in 1998 I had the opportunity to listen to a series of lectures on the first 30 years of exploration of the solar system. Ed Stone was present, and you will see his visage if I can figure out a way to let you watch the "Voyager" video on line :). Most interesting to me was the talk of Raoul Sagdeev, a leader of the Soviet space exploration initiative. While not responsible for the manned missions, he was heavily involved in the unmanned missions, and in particular of those space probes sent to Venus and Mars. By a form of gentlemen’s agreement, the Americans were to explore Mars while the Soviets would explore Venus. The USSR sent 16 Venera probes to Venus in the early 1970’s. Some of these missions were unsuccessful with probes being lost on the launch pad, disintegrated in the upper atmosphere of Venus, or being crushed on the surface of our sister planet. However, there was sufficient success over the length of the program such that they made safe landings and took photos from the surface of Venus. Meanwhile, Americans launched spacecraft to Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, the Sun, and some asteroids and comets. Like the Russians, plenty were failures. However, a great deal were successful. It is my hope to give you a glimpse into the robot spacecraft missions and some of the results of their travels. Since this page is primarily introductory, we will look more closely at the mission results in the Solar System Unit.

The first satellite to be placed successfully in orbit was the Soviet's Sputnik 1, on October 4, 1957. When America heard the simple beeping pattern of this little metal ball, we were ushered into the Space Age and plunged deeper into the Cold War. Few students who were born after 1970 can comprehend the emotional fear which accompanied the beeping of this little satellite. It was reasonable to conclude that if the Russians could put a small satellite into orbit, it would be no small feat to place nuclear warhead aboard space missiles. The United States would sit at the negotiating table without a trump card, and the Soviets would set all major policies from their position of greater power. From that October day forward, America would be playing a game of catch-up. The political goal would be to beat the Russians to the moon and prove the superiority of our governmental method. Every attempt to launch a satellite would be viewed with great anticipation, as much from the general public as it was from the military brass and political leaders.

Eventually, the Americans launched Explorer 1, a more missile-shaped satellite, that discovered a dense belt of radiation surrounding the Earth ... later named the Van Allen Belt. The race was joined and public excitement grew. Russian launched satellites, America launched satellites, Russia experienced failures, America experienced failures. Eventually, the great Soviet Union dismantled and the space endeavor was picked up by other countries in a more cooperative environment. The European Space Agency was formed with their own satellite program. Today, China has entered the Space Age with satellites and proposed manned spaceflight.

For a complete look back at the history of spaceflight, please check out these websites:




Chronology of Spaceflight

History of NASA

History of Unmanned US Satellite Missions

Complete List of All Spaceflights

Jet Propulsion Laboratory

To me, this is where it all starts when one wishes to learn about the unmanned space program. The Jet Propulsion Laboratory (JPL) is located in Pasedena, California, and is a surprisingly visitor-friendly place. While satellites are launched in Florida, the mission control center is in Pasedena. To learn more about the JPL and its numerous missions, past, present, and future, click on the name above this paragraph.

Explorer 1 was the first successful US satellite, and it is shown in the image to your left, hoisted by Wehrner Von Braun himself. To learn more about this satellite, connect to the name and thus to the Explorer homepage.






Inner Rocky World Exploration

Mariner 1 and 2 The US sent the Mariner series to Mercury and Mars, and then later the Viking missions landed on Mars, took photographs, and dug trenches in the Martian sand to search for biomolecules. The complete lack of any form of life on both Venus and Mars came as a bit of a disappointment for many astronomers, but the scientific data that was returned told us much of the geology of these two worlds.

Mariner 3 and 4

Mariner 10 The Mariner 10 mission to Mercury was interesting in that the satellite made three passes by the planet, and at each instance, the same side of Mercury was illuminated by the sun and thus we have photographed only 44% of this planet’s surface.

Viking 1 and 2 The Viking mission to Mars even sent back one famous photo of a large rock formation which looked surprisingly like a gigantic human face, and this fueled the notion of alien civilizations. The more recent Mars Global Surveyor passed over this rock formation and confirmed that it was mere shadowing from the sun. After the Sojourner and Pathfinder missions of 1998, we have a much greater understanding of the Martian surface. A small robotic car analyzed soil and rock samples better than ever before, but still there is no evidence of life ever gaining a foothold on Mars. Missions are proposed in the next 6 years to send a series of space craft to Mars, each with small robotic cars to collect sample rocks. A later mission will then land on Mars, retrieve these rocks, and return them to Earth for further analysis. The fear of bringing a virus to Earth for which there are no defenses is real, and great care will be taken to keep these samples under the strictest biosecurity.

Venera To me, any discussion of the US Space Program is incomplete without equal attention given to the Soviet Space Program. Unfortunately, I am still unearthing this information so that students of Astronomy can have a more complete picture of the space race and develop their own opinion about the political sides and motives. Beyond the Sputnik program, the Soviets launched an ambitious campaign to explore Venus ... our sister planet. By gentleman's agreement, America would explore Mars and share information, while the Russians would explore Venus and share their findings. Thus began project Venera ... Russia's multisatellite mission to the cloud-enshrouded planet. The launch complex at the Baikonur Cosmodrome, Kazakhstan is a pretty cool site to visit. While many of the missions were failures because Venus turned out to be nothing expected, they managed to land several spacecraft on the surface and take images of this unusual planet. Two Venera craft are shown below ... Venera 14 and 15.

Phobos Of particular interest was the timing of star wars technology. The USSR was under the treaty agreement to the ban star wars program, but was secretly working on one anyway. In the mid-1980’s, they wanted to send a probe to Phobos, a moon of Mars. The satellite was to arrive, fire a laser at the surface of the moon, blast off rock fragments which could achieve escape velocity, and then collect this debris for a return trip to Earth. The US spy organization learned of this secret plan and officials made a offer to attach a supersensitive camera to the Soviet probe ... supposedly to study the moon's surface. The Soviets went public and formally asked the US if they would like to piggyback a mission with them to Phobos. Since our government saw this as an opportunity to directly study the Soviet star wars technology with their camera, they obliged, because they wanted to test their laser and improve their negotiating position in power talks. Sadly, the mission failed as it approached Mars and was completely lost. The Soviets did not get a chance to test their laser on this supposedly scientific mission. Dr. Sagdeev left his country in anger and moved to America shortly thereafter. If you want to see a more fanciful approach to the star wars laser idea, watch James Bond in "Goldeneye."

To see a complete picture of the history of the Russian Space Program, go to their website and then check out some of the ambitious plans of the Chinese.

Magellan In 1994, the US government discontinued funding for the Magellan mission to Venus, and the space craft burned up in the atmosphere. Prior to its demise, Magellan mapped the surface of Venus to a great detail giving us a better understanding of the world hidden beneath perpetual clouds than ever before. The Soviets dropped balloons with transmitters into these clouds and discovered that they circumnavigated the planet in a mere 4 days! While almost no winds blow at the surface, the high altitude clouds are moving very quickly. There is much more to learn about Venus in the Solar System Unit.





Mars Observer This is a truly disappointing mission. After a successful launch and nearly yearlong journey, the Mars Observer was braking for insertion into Mars orbit when a malfunction shut down the satellite, ending the mission permanently. Turns out that a ground controlled had given commands to the spacecraft in English measurement units instead of metric, and the onboard computer did not understand the command and froze!


Mars Global Surveyor was sent after the embarrassing Mars Observer debacle, and its purpose was to map the surface of Mars and find some nice landing sites for the Pathfinder mission. The pictures are still arriving at the Earth, and you will be asked to analyze Martian craters and determine their presence and edge for an ongoing survey of the surface.







Mars Sojourner and Pathfinder was the most successful mission to Mars. The spacecraft dropped to the planet's surface in giant crash balloons, similar to those found in the steering wheel of your car. After bouncing around a while, the balloons settled, were deflated, and the spacecraft was ready for its mission. One part formed a homebase, while a small electronic car scurried around the surface taking pictures of rocks and dust. The mission was launched December 4, 1996 and landed July 4, 1997 ... the same day as the release of the movie Independence Day. The little Rover worked well, before finally freezing up for good later in October.


Gas Giant Missions

Pioneer 10-11 were the first satellites to explore the outer planets Jupiter and Saturn, and are still returning signals almost 30 years after their encounter. Both have flown beyond the orbit of Pluto and are technically out of the Solar System, but not yet beyond the heliopause ... a place where the solar wind is negligible and interstellar space is reached.

Voyager and its Mission Timeline

Without any doubt, my personal favorite space mission was the Voyager project. As much as I looked up to Jim Lovell as a hero, I now look professionally at the early Voyager team members as heroes. Ed Stone, Carolyn Porco, Larry Soderblom, Ray Heacock, Andy Gill, and others were pioneers in getting this satellite out to Jupiter and Saturn. There was no clearly elucidated plan for Voyager to visit the final two gas giants of our solar system, but with the rare alignment of the planets, and some persuasive speech, the JPL engineers sold their plan to tweak the trajectory of Voyager 2 and send it on to Uranus and Neptune. The purpose of the mission was to explore the outer gas giant planets and their moons, learn about their magnetic fields, atmospheric composition, and other interesting phenomenon which earth-based instruments could not detect. Perhaps the most significant discovery of the mission was the presence of active volcanoes on the surface of Jupiter's moon Io. This altered the expectations of the Voyager team. From that point forward, no one was complacent. The moons, originally thought to be geologically inactive and bland would prove far more interesting than anyone could have imagined.

Click on image to enlarge.

Pioneer 10 and 11 explored Jupiter and Saturn in the mid-1970’s, but it was the Voyager 1 and 2 missions which proved most successful. Imagine that one of these space craft flew to Neptune, over 4 billion kilometers from here and almost 12 years en route, and arrived within a kilometer of its exact destination. All of this was accomplished with a system operating on less power than a 20 watt light bulb and computers with less computing power than that which exists in your car today. The Voyager program opened our eyes to the splendor of the gas giant planets and showed us that in these outer worlds, "the bizarre had become commonplace." You would enjoy the Voyager video in my classroom course, but for now you will have to trust my enthusiasm. Presently, the Galileo satellite is orbiting the Jovian system, analyzing the Galilean moons and Jupiter’s magnetosphere. On December 7, 1995, it dropped a probe into Jupiter’s atmosphere at 106,000 km/hr and recorded data of the chemicals present there before incinerating after 47 minutes.

Galileo was a satellite sent to explore Jupiter in detail. This mission continues today (that is as of May, 2002), orbiting Jupiter and passing by Jupiter's major moons, Io, Europa, Ganymede, and Callisto. Most significant to this mission is the discovery of an immense magnetic field surrounding the planet. Radiation is trapped within this field, making human flight impossible within a 3 million km radius of the planet. The Galileo spacecraft electronics are stressed with each flyby of Io, and it continues to return images. During deployment after the launch, the large umbrella-shaped antenna failed to open completely, threatening the mission. Fortunately, back-up transmitters and receivers worked and the mission has been a major success. On December 7, 1995, an atmospheric probe was dropped into the clouds of Jupiter. The probe sent information for almost an hour before friction in the thickening atmosphere and increasing pressure vaporized the probe. We will learn more about the results of the Galileo probe in the Solar system unit.


In the summer of 2000, I had the opportunity to meet Dr. Carolyn Porco at an Astronomy Society of the Pacific annual meeting. She was the imaging director of the Voyager project, and was now the project manager of Cassini. This bus-sized satellite is the last of the great satellite missions. Dr. Golden, NASA director, scaled down the space mssions, opting for smaller, faster, cheaper satellites. Cassini would be the final multi-billion dollar spaceprobes, and great hopes travel with it. Cassini was launched in 1997 and will arrive at Saturn in the summer of 2004. As it approaches, a small probe (Huygens Probe) will be dropped into the atmosphere of Saturn's moon Titan. That's right! There is a large moon orbiting Saturn that has an atmosphere, although not quite like Earth, and significantly colder ... say -180oC at the surface. If you thought the rings of Saturn look cool in the Voyager images, wait until you see what Cassini will send back in a few more years. On a side note, the launch of the spacecraft received some unwelcome attention from various anti-nuke and pro-environmental groups. These large satellites are all powered by radioisotope thermal generators. Plutonium is housed in a small, hardened box, and as it spontaneously decays heat is released. The heat powered the generators which give power to the spacecraft for their transmitters and receivers. The activists were fearful of an unsuccessful launch and potential explosion that might release the plutonium into the atmosphere. They were on boats offshore, threatening to stop the launch with their presence. The US Navy and Coast Guard removed them from the launch pad waters and Cassini was on its way. Had the rocket exploded, there was no danger of any release of plutonium because of the extreme caution taken by the engineers in safely housing the material.

On August 18, 1999 the Cassini mission successfully flew past Earth and received a gravity boost on its trip to Saturn. The 6 ton space craft is so large, that current rockets were unable to lift it directly to Saturn. Cassini flew instead to Venus, where it received 2 gravity assists, one from the Earth, and one more to come from Jupiter before it finally arrives at Saturn in 2004. Carolyn Porco is one of the mission directors, and she too is seen in the Voyager video as part of the imagine team in the 1980 mission to Saturn. She will have waited 7 years from the launch of Cassini before it finally arrives at Saturn.

Deep Space 1 was really more about an innovative form of propulsion than a mission to any particular place. The ion drive engines worked extremely well, as this spacecraft was actually able to take a picture of a target in space and self-adjust as it approached, without steering by the mission controllers. DS1 flew by an asteroid and a comet, taking some pretty fantastic photos en route and on location. We will learn more about the particular findings of this satellite in the Solar System unit, but you are welcome to check out the DS1 homepage now if you want.




Websites to connect you to space missions

Deep Space Network

Ames Research Center

Goddard Space Flight Center

National Space Science Data Center

Jet Propulsion Laboratory

Kennedy Space Center

Beyond these probes to other planets, our world has launched many other satellites for other scientific pursuits. Perhaps the most famous is the Hubble Space Telescope (HST). After a space shuttle mission corrected the optics in 1993, the HST has sent innumerable pictures of deep space objects which are telling us of star life cycles, galactic recession, and very distant objects. The HST website changes almost daily with new photos of interest and a vast library of stored images for your enjoyment or study. The HST has also sent back some pretty cool pictures for posters which adorn my classroom, student dorm rooms, and office walls.
Other satellites orbit our planet studying solar phenomenon, x-ray emitting objects, gamma ray bursters, microwave objects, or stellar distances. With the fall of communism in the USSR and the dismantling of the Soviet states, more space missions today are joint efforts between countries for mutual scientific benefit. A space station is currently being built by many nations, and it will allow continual scientific experimentation in the zero gravity environment of space. The quest for knowledge of our Universe is unending, and with steady improvements in technology we will be learning more and more. While scientists open the doors of the Universe to us, we must always be keeping the doors of our hearts open to spiritual teaching and have our minds trained to discern truth. The coming years will probably not have publicly funded space missions, but the increasing number of satellite launches will continue to make the Universe reveal more of its secrets.

Where are the Voyager and Pioneer spacecrafts today?

After Voyager 1 flew by up through the rings of Saturn, it continued in a northerly trajectory relative to the ecliptic, and is continuing to travel out of our solar system. There are two things which control the future of the Voyager spacecraft ... the amount of nuclear fuel as well as the amount of thruster engine fuel. The spacecraft uses the decay of Plutonium to generate heat, which in turn is converted into electricity, that can be used to send signals to the JPL facility in Pasadena, as well as receive signals from Earth. The thruster fuel is used to point the Voyager receiver/transmitter antenna at the Earth. Scientists believe that there is enough of both fuels to keep Voyager 1 operational until about 2015-2020. It is hoped by that time, that Voyager will have escaped the heliosphere (the bubble or gas blown out by the Sun), cross the heliopause (where the Sun's wind-blown bubble ends and interstellar space begins), and enter interstellar space. The mission has been renamed Voyager Interstellar Mission, and scientists are continuing to maintain contact with both Voyager 1 and 2.

This information in the last paragraph of this page is found in several other places within my course because I believe it to be incredibly important, interesting, and relevant to a potential creative writing assignment of yours :)

I suppose that this page will never be complete since websites are continually being updated, deleted, or moved. I will be adding to this unit over the years I hope to be teaching on-line. For now though, please proceed to the Space History Quiz, or return to the Introduction to Space Exploration.

This also represents the conclusion to the Exploration of Space Unit. You should have completed the assignments for this unit by now, and thus be ready to move forward to discover what we have learned from these missions ... starting with the Earth. If you need a break, just go back to the Syllabus or the Home page.

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