Space Exploration - Robotic Missions
While the manned space program of the 1960s 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 gentlemens agreement, the Americans were to explore
Mars while the Soviets would explore Venus. The USSR sent 16 Venera probes to
Venus in the early 1970s. 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
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
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.
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
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
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 planets
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.
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-1980s, 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.
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.
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!
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.
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
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.
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-1970s, 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 Jupiters
magnetosphere. On December 7, 1995, it dropped a probe into Jupiters atmosphere
at 106,000 km/hr and recorded data of the chemicals present there before incinerating
after 47 minutes.
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.
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
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?
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
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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