The following list contains only selected spacecraft of interest to planetary science. It
is far from complete (see below for more details).
Much of the following was adapted from the
- Luna 2
- impact on the surface of the Moon 1959 (USSR)
- Luna 3
- first photos of the farside of the Moon 1959 (USSR)
- Mariner 2
- the first successful probe to flyby Venus in December
of 1962, and it returned information which confirmed that Venus is a
very hot (800 degrees Fahrenheit, now revised to 900 degrees F.) world
with a cloud-covered atmosphere composed primarily of carbon dioxide.
(more info from NASA Spacelink)
- Mariner 3
- launched on November 5, 1964, was lost when its protective
shroud failed to eject as the craft was placed into interplanetary
space. Unable to collect the Sun's energy for power from its solar
panels, the probe soon died when its batteries ran out and is now in
solar orbit. It was intended for a Mars
flyby with Mariner 4.
- Mariner 4
- the sister probe to Mariner 3, did reach Mars in 1965 and
took the first close-up images of the Martian surface (22 in all) as it
flew by the planet. The probe found a cratered world with an atmosphere
much thinner than previously thought. Many scientists concluded from
this preliminary scan that Mars was a "dead" world in both the
geological and biological sense.
- Mariner 9
- Mariner 9, the sister probe to Mariner 8 which failed on launch,
became the first craft to
orbit Mars in 1971.
It returned information on the Red Planet that no
other probe had done before, revealing huge volcanoes on the Martian
surface, as well as giant canyon systems, and evidence that water once
flowed across the planet. The probe also took the first detailed closeup
images of Mars' two small moons,
Phobos and Deimos.
- 6 manned landings on the Moon
and sample returns 1969-72.
(Apollo "home page")
- Luna 16
- automated sample return from
the Moon 1970 (USSR)
- Pioneer 10 and Pioneer 11
- Pioneer 10 was the first spacecraft to flyby
Jupiter in 1973.
followed it in 1974, and then went on to become the first probe to
study Saturn in 1979.
The Pioneers were designed to test the ability of spacecraft to survive passage
thru the asteroid belt and Jupiter's magnetosphere. The asteroid belt was easy,
but they were nearly fried by ions trapped in Jupiter's magnetic field. This
information was crucial to the success of the Voyager
Pioneer 11's RTG power supply is dead. Its last communication with Earth
was in November 1995.
Pioneer 10 continues to gather valuable scientific data but will be shut
down on March 31, 1997 due to budget cutbacks.
They are heading off into interstellar space, the first craft ever to do so.
As the first two spacecraft to leave our solar system,
Pioneer 10 & 11 carry a graphic message in the form of a 6- by
9-inch gold anodized
bolted to the spacecraft's main frame.
(Pioneer Project Home Page
and more about Pioneer 10 and Pioneer 11 from NASA Spacelink; current status from NASA Ames)
- Mariner 10
- used Venus as a gravity assist to
Mercury in 1974. The probe
did return the first close-up images of the Venusian atmosphere in
ultraviolet, revealing previously unseen details in the cloud cover,
plus the fact that the entire cloud system circles the planet in four
Earth days. Mariner 10 eventually made three flybys of Mercury from 1974
to 1975 before running out of attitude control gas. The probe revealed
Mercury as a heavily cratered world with a mass much greater than
thought. This would seem to indicate that Mercury has an iron core which
makes up 75 percent of the entire planet.
(more from JPL and
- Venera 7
- First probe to return data from the surface of another planet
(Venus) in 1970.
- Venera 9
- soft landing on Venus,
pictures of the surface 1975. (USSR) This was the first spacecraft to land
on the surface of another planet.
- Pioneer Venus
- 1978; orbiter and four atmospheric probes; made the first high-quality map
of the surface of Venus.
(more info from NASA Spacelink; a tutorial from UCLA)
- Viking 1
- Viking 1 was launched from Cape Canaveral, Florida on August 20, 1975 on
a TITAN 3E-CENTAUR D1 rocket. The probe went into Martian
orbit on June
19, 1976, and the lander set down on the western slopes of Chryse
Planitia on July 20, 1976. It soon began its programmed search for
Martian micro-organisms (there is still debate as to whether the probes
found life there or not), and sent back incredible color panoramas of
its surroundings. One thing scientists learned was that Mars' sky was
pinkish in color, not dark blue as they originally thought (the sky is
pink due to sunlight reflecting off the reddish dust particles in the
thin atmosphere). The lander set down among a field of red sand and
boulders stretching out as far as its cameras could image.
- Viking 2
- Viking 2 was launched on September 9, 1975, and arrived in
on August 7, 1976. The lander touched down on September 3, 1976 in
Utopia Planitia. It accomplished essentially the same tasks as its
sister lander, with the exception that its seismometer worked, recording
The last data from Viking (Lander 1) made its final transmission to Earth
Nov. 11, 1982. Controllers at JPL tried unsuccessfully for
another six and one-half months to regain contact with Viking
Lander 1. The overall mission came to an end May 21, 1983.
An interesting side note: Viking 1's lander has been designated the
Thomas A. Mutch Memorial Station in honor of the late leader of the
lander imaging team. The National Air and Space Museum in Washington,
DC is entrusted with the safekeeping of the Mutch Station Plaque until
it can be attached to the lander by a manned expedition.
(more info and an web page from JPL)
- Voyager 1
- Voyager 1 (image at top) was launched September 5, 1977, and flew past
Jupiter on March
5, 1979 and by Saturn
on November 13, 1980. Voyager 2 was launched
August 20, 1977 (before Voyager 1), and flew by Jupiter on August 7,
1979, by Saturn on August 26, 1981, by Uranus
on January 24, 1986, and
by Neptune on August 8, 1989.
Voyager 2 took advantage of a rare
once-every-189-years alignment to slingshot its way from outer planet to
outer planet. Voyager 1 could, in principle, have headed towards
but JPL opted for the sure thing of a Titan close up.
Between the two probes, our knowledge of the 4 giant planets, their
satellites, and their rings has become immense. Voyager 1&2 discovered
that Jupiter has complicated atmospheric dynamics, lightning and
Three new satellites were discovered. Two of the major
surprises were that Jupiter has rings and that
Io has active sulfurous
volcanoes, with major effects on the Jovian magnetosphere.
When the two probes reached Saturn, they discovered over 1000 ringlets
and 7 satellites, including the predicted shepherd satellites that keep
the rings stable. The weather was tame compared with Jupiter: massive
jet streams with minimal variance (a 33-year great white spot/band cycle
is known). Titan's atmosphere was smoggy.
Mimas's appearance was
startling: one massive impact crater gave it the Death Star appearance.
The big surprise here was the stranger aspects of the rings. Braids,
kinks, and spokes were both unexpected and difficult to explain.
- Voyager 2
- Voyager 2, thanks to heroic engineering and programming efforts,
continued the mission to Uranus and
Uranus itself was highly
monochromatic in appearance. One oddity was that its magnetic axis was
found to be highly skewed from the already completely skewed rotational
axis, giving Uranus a peculiar magnetosphere. Icy channels were found on
Miranda was a bizarre patchwork
of different terrains. 10
satellites and one more ring were discovered.
In contrast to Uranus, Neptune was found to have rather active weather,
including numerous cloud features. The ring arcs turned out to be bright
patches on one ring. Two other rings, and 6 other satellites, were
discovered. Neptune's magnetic axis was also skewed.
Triton had a
canteloupe appearance and geysers. (What's liquid at 38K?)
If no unforeseen failures occur,
we will be able to maintain communications with both spacecraft
until at least the year 2030.
Both Voyagers have plenty of hydrazine fuel -- Voyager 1 is expected
to have enough propellant until 2040 and Voyager 2 until 2034. The
limiting factor is the RTGs (radio-isotope thermal generators).
The power output from the RTGs is slowly
dropping each year. By 2000, there won't be enough power for the UVS
(ultraviolet spectrometer) instrument. By 2010, the power will have
dropped low enough such that not all of the fields and particles instruments
can be powered on at the same time. A power sharing plan will go into
where some of the F&P instruments are powered on, and others off.
The spacecraft can last in this mode for about another 10 years, and after
that the power will probably be too low to maintain the spacecraft.
(the Voyager Project Home Page from JPL; another nice "home page" at NSSDC; fact sheets and a web page from JPL; General Info from NASA/ARC)
- International project VENUS-HALLEY, launched in 1984, carried a Venus orbiter and
lander and did a fly-by of Comet Halley.
(Vega Mission Home page
- Two spacecraft were launched by the USSR in 1988. One failed with out a trace.
A few images were returned
before the second one failed, too.
(Phobos Mission Home page
- Giotto was launched by an Ariane-1 by ESA on July 2 1985, and approached
within 540 km +/- 40 km of the nucleus of
Comet Halley on March 13,
1986. The spacecraft carried 10 instruments including a multicolor
camera, and returned data until shortly before closest approach, when
the downlink was temporarily lost. Giotto was severely damaged by
high-speed dust encounters during the flyby and was placed into
hibernation shortly afterwards.
In April, 1990, Giotto was reactivated. 3 of the instruments proved
fully operational, 4 partially damaged but usable, and the remainder,
including the camera, were unusable. On July 2, 1990, Giotto made a
close encounter with Earth and was retargeted to a successful flyby of
comet Grigg-Skjellerup on July 10, 1992.
(more info from NSSDC)
- a joint mission of the Ballistic Missile Defense Organization
(formerly SDIO) and NASA to flight test sensors developed by Lawrence
Livermore for BMDO. The spacecraft, built by the Naval Research Lab, was
launched on January 25 1994 to a 425 km by 2950 km orbit of the
Moon for a 2
month mapping mission. Instruments onboard include UV to mid-IR imagers,
including an imaging lidar that may be able to
also obtain altimetric
data for the middle latitudes of the Moon.
In early May the spacecraft
was to have been sent out of lunar orbit toward a flyby
of the asteroid 1620 Geographos
but a failure prevented the attempt.
Ground controllers have regained control of the spacecraft, however.
Its potential future mission is being considered.
(for more information see the
Clementine Mission Home page from USGS and the
Clementine page from NASA PDS or The Clementine Mission from LPI.)
- Mars Observer
- Mars orbiter including 1.5 m/pixel resolution camera.
Launched 9/25/92 on a Titan III/TOS booster. Contact was lost with MO on
8/21/93 while it was preparing for entry into Mars orbit. The spacecraft
has been written off
Mars Global Surveyor,
a replacement mission to achieve
most of MO's science goals, is scheduled to launch in November 1996.
- Launched in May 1989, Magellan
has mapped 98% of the surface of Venus
at better than 300 meter resolution and obtained a
comprehensive gravity field map for 95 percent of the planet.
Magellan recently executed an 80-day aerobraking program to lower and
circularize its orbit. Magellan has
completed its radar mapping and gravity data collection. In the fall of
1994, just before it would have failed due to deterioration in its solar
panels, Magellan was deliberately sent
into Venus' atmosphere to further study
aerobraking techniques which can make major savings in fuel for future
(more info, a web page and another web page from JPL; Magellan page from NASA PDS; fact sheet from NSSDC)
- Mars 96
- a large orbiter with several landers originally known as Mars 94.
Launch failed 1996 November 17.
(The original Mars 96 was known for a while as Mars 98 and then cancelled.)
(more info from MSSS and
from IKI (Russia))
- Pioneers 10 and 11 and Voyagers 1 and 2
- still operational after more than 15 years in space and are traveling out of the
Solar System. The two Voyagers are expected to last until at least
the year 2015 when their radioisotope thermoelectric generators (RTG)
power supplies are expected for fail. Their trajectories
give negative evidence about possible planets beyond Pluto. Their
next major scientific discovery should be the location of the heliopause. Low-frequency radio
emissions believed to originate at the heliopause have been detected
by both Voyagers.
Both Voyagers are using their ultraviolet spectrometers to map the
heliosphere and study the incoming interstellar wind. The cosmic
ray detectors are seeing the energy spectra of interstellar
cosmic rays in the outer heliosphere
It is now estimated that Voyager 1 will pass the Pioneer 10
spacecraft in January 1998 to become the most distant human-made
object in space.
(more info from JPL)
As of December 1 1994, Voyager 1 was 8.7 billion kilometers (5.4
billion miles) from Earth traveling at 61,200 km/hr (39,000 mph)
and Voyager 2 was 6.7 billion
kilometers (4.2 billion miles) from Earth traveling at 57,600 km/hr (36,000 mph).
orbiter and atmosphere probe, now in Jupiter orbit.
It will make extensive surveys of the Jovian moons and the probe has
descended into Jupiter's atmosphere to provide our first direct
evidence of the interior of a gas giant.
Galileo has already returned
the first resolved images of two asteroids,
951 Gaspra and
while in transit to Jupiter. It has also returned pictures of the impact
of Comet SL9 onto Jupiter from its unique vantage
Efforts to unfurl the stuck High Gain
Antenna (HGA) have essentially been abandoned.
With its Low Gain Antenna
Galileo transmits data at about 10 bits per second.
JPL has developed a
backup plan using enhancements of the receiving antennas in the Deep
Space Network and data compression (JPEG-like for images, lossless
compression for data from the other instruments) on the spacecraft. This
should allow Galileo to achieve approximately 70% of its original
science objectives with the much lower speed Low Gain Antenna. Long term
Jovian weather monitoring, which is imagery intensive, will suffer the
The magnetotail passage occurs on the long orbit between Callisto 9 and 10.
Galileo will also obtain a few images of Jupiter's ring system and some of its
Galileo passed by Jupiter at a distance of only 214,000 km from
the cloud tops on its first "perijove" on 7-Dec-1995
No images of Io and Europa were returned from the intial orbit due to
concerns with the tape recorder. An additional close pass by Io may be
added late in the mission.
The date from the probe has been safely returned to Earth and the last major
manouver completed successfully. New software has been uploaded which (among
other things) uses data compression techniques to improve the effective
data transmission rate by a factor of 8.
(Education and Public Outreach (images!); Galileo page from NASA PDS; the Galileo Home Page; Galileo Probe Home Page and more info from JPL; newsletter; web page; NSSDC page; preliminary Galileo Probe Results from JPL and ARC and LANL)
- Hubble Space Telescope
- launched April 1990;
fixed December 1993.
HST can provide pictures and spectra over a long period of time.
This provides an important extra dimension to the higher
resolution data from the planetary probes. For example, recent HST data shows
is colder and drier than during the Viking missions; and HST images of
indicate that its atmospheric features change rapidly.
Named for the American astronomer Edwin Hubble.
Much, much more information about HST and HST pictures are available at the
Space Telescope Science Institute.
HST's latest images are
a brief history of the HST project.
There's also some more
HST info at JPL.)
- now investigating the
Sun's polar regions (European Space Agency/NASA).
Ulysses was launched by the Space Shuttle Discovery in October 1990.
In February 1992, it got a gravity boost from Jupiter
and to take it out of the plane of the
It has now completed its main mission of surveying both of the Sun's
Its mission has been extended for another orbit so that it can survey
the Sun's poles near the maximum of the sunspot cycle, too.
Its aphelion is 5.2 AU, and, surprisingly, its
perihelion is about 1.5 AU-- that's right, a solar-studies spacecraft
that's always further from the Sun than the Earth is!
It expected to provide a much
better understanding of the Sun's magnetic field and the
(Ulysses Home Pages from JPL and
a Fact Sheet from JPL;
yet more info from JPL)
- After its November 1, 1994, launch, NASA's Wind
satellite will take up a vantage point between the Sun and
the Earth, giving scientists a unique opportunity to study
the enormous flow of energy and momentum known as the solar
The main scientific goal of the mission is to measure
the mass, momentum and energy of the solar wind that somehow
is transferred into the space environment around the Earth.
Although much has been learned from previous space missions
about the general nature of this huge transfer, it is
necessary to gather a great deal of detailed information from
several strategic regions of space around the Earth before
scientists understand the ways in which the planet's
atmosphere responds to changes in the solar wind.
The launch also marks the first time a Russian
instrument will fly on an American spacecraft. The Konus
Gamma-Ray Spectrometer instrument, provided by the Ioffe
Institute, Russia, is one of two instruments on Wind which
will study cosmic gamma-ray bursts, rather than the solar
wind. A French instruments is also aboard.
At first, the satellite will have a
figure-eight orbit around the Earth with the assistance of
the Moon's gravitational field. Its furthest point from the
Earth will be up to 990,000 miles (1,600,000 kilometers), and
its closest point will be at least 18,000 miles (29,000
Later in the mission, the Wind spacecraft will be
inserted into a special halo orbit in the solar wind upstream
from the Earth, at the unique distance which allows Wind to
always remain between the Earth and the Sun (about 930,000 to
1,050,000 miles, or 1,500,000 to 1,690,000 kilometers, from
- The Near Earth Asteroid Rendezvous (NEAR) mission promises
to answer fundamental questions about the nature of near-Earth
objects such as asteroids and
Launched on 1996 February 17 aboard a Delta 2
rocket, the NEAR spacecraft should arrive in orbit around
asteroid 433 Eros in early January 1999. It will then survey
the rocky body for a minimum of one year, at altitudes as
close as 15 miles (24 kilometers). Eros is one of the largest
and best-observed asteroids whose orbits cross Earth's path.
These asteroids are closely related to the more numerous "Main
Belt" asteroids that orbit the Sun in a vast doughnut-shaped
ring between Mars and Jupiter.
(NEAR Home Page; more info from NSSDC;
more from JPL)
- Mars Surveyor Program
- Mars Global Surveyor is the first mission of a new,
decade-long program of robotic exploration of Mars, called
the Mars Exploration Program. This will be an aggressive
series of orbiters and landers to be launched every 26
months, as Mars moves into alignment with Earth. The
program will be affordable, costing about $100 million per
year; engaging to the public, providing fresh new global and
close-up images of Mars; and have high scientific value
obtained with the development of leading-edge space
Mars Global Surveyor will be a polar-orbiting
spacecraft at Mars designed to provide global maps of
surface topography, distribution of minerals and monitoring
of global weather.
Launched with a Delta II expendable vehicle from Cape
Canaveral, Fla., on November 7 1996, the spacecraft is now
in its 10-month cruise phase; it will arrive at Mars on September 12, 1997,
where it will be initially
inserted into an elliptical capture orbit. During the
following four months, thruster firings and aerobraking
techniques will be used to reach the nearly circular mapping
orbit over the Martian polar caps. Aerobraking, a technique
pioneered by the Magellan mission,
which uses the forces of atmospheric drag to slow the
spacecraft into its final mapping orbit, will provide a
means of minimizing the amount of fuel required to reach the
low Mars orbit. Mapping operations are expected to begin in
late January 1998.
The spacecraft will circle Mars once every two hours,
maintaining a "sun synchronous" orbit that will put the sun
at a standard angle above the horizon in each image and
allow the mid-afternoon lighting to cast shadows in such a
way that surface features will stand out. The spacecraft
will carry a portion of the Mars Observer instrument payload
and will use these instruments to acquire data of Mars for a
full Martian year, the equivalent of about two Earth years.
The spacecraft will then be used as a data relay station for
signals from U.S. and international landers and low-altitude
probes for an additional three years.
International participation, collaboration and
coordination will enhance all missions of the program.
Landers in future years -- 1998, 2001, 2003 and 2005 -- will
capitalize on the experience of the Mars Pathfinder lander
mission to be launched in 1996. Small orbiters launched in
the 1998 and 2003 opportunities will carry other instruments
from the Mars Observer payload and will serve as data relay
stations for international missions of the future.
The Mars Global Surveyor spacecraft will be acquired
from industry through a competitive procurement. The
science payload will be provided as government-furnished
equipment that was built to duplicate the instruments flown
on Mars Observer. The payload includes the Mars orbital
camera, thermal emission spectrometer, ultra-stable
oscillator, laser altimeter, magnetometer/electron
reflectometer and Mars relay system.
The Jet Propulsion Laboratory will manage the project
for NASA's Solar System Exploration Division and will
provide the mission design, navigation, and conduct mission
operations. Tracking and data acquisition will be provided
by a 34-meter subnetwork of the worldwide Deep Space
Project costs for the Mars Global Surveyor through 30
days after launch will be approximately $155 million.
(MGS Home Page from JPL; Planned Missions from 1996 to 2003)
The Mars Pathfinder (formerly known as the Mars Environmental Survey,
or MESUR, Pathfinder) is the second of NASA's low-cost planetary
Discovery missions. The mission consists of a stationary lander
and a surface rover known as Sojourner. The mission has the primary objective of
demonstrating the feasibility of low-cost landings on and exploration
of the Martian surface. This objective will be met by tests of
communications between the rover and lander, and the lander and Earth,
and tests of the imaging devices and sensors.
The scientific objectives include atmospheric entry science,
long-range and close-up surface imaging, with the general objective
being to characterize the Martian environment for further exploration.
The spacecraft will enter the Martian atmosphere without
going into orbit around the planet and land on Mars with the aid of
parachutes, rockets and airbags, taking atmospheric measurements on
the way down. Prior to landing, the spacecraft will be enclosed by
three triangular solar panels (petals), which will unfold onto the
ground after touchdown.
Mars Pathfinder was launched 1996 December 4 and
will arrive at Mars 1997 July 4.
MPF Home Page from JPL;
more info from NSSDC;
images and press releases from MSFC;
Mars Watch, Linking Amateur and Professional Mars Observing Communities for Observational Support of the Mars Pathfinder Mission)
(All missions not otherwise labeled are NASA)
orbiter and Titan atmosphere probe.
Cassini is a joint
NASA/ESA project designed to accomplish an exploration of the Saturnian
system with its Cassini Saturn Orbiter and Huygens Titan Probe. Cassini
is scheduled for launch aboard a Titan IV/Centaur in October of 1997.
Before arriving at Saturn, Cassini will first execute two gravity assist flybys
of Venus, then one of Earth, and then one of Jupiter (a "VVEJGA" trajectory)
before arriving at Saturn in June 2004.
Upon arrival, the Cassini spacecraft performs several maneuvers to achieve an
orbit around Saturn. Near the end of this initial orbit, the Huygens
Probe separates from the Orbiter and descends through the atmosphere of
Titan. The Orbiter relays the Probe data to Earth for about 3 hours
while the Probe enters and traverses the cloudy atmosphere to the
surface. After the completion of the Probe mission, the Orbiter
continues touring the Saturnian system for three and a half years. Titan
synchronous orbit trajectories will allow about 35 flybys of Titan and
targeted flybys of Iapetus,
Enceladus. The objectives of the
mission are threefold: conduct detailed studies of Saturn's atmosphere,
rings and magnetosphere; conduct close-up studies of Saturn's
satellites, and characterize Titan's atmosphere and surface.
An earlier plan for an asteroid fly-by on the way out similar to the
highly successful Galileo fly-bys of
Ida and Gaspra
was scrapped in order to reduce costs.
One of the most intriguing aspects of Titan
is the possibility that its
surface may be covered in part with lakes of liquid hydrocarbons that
result from photochemical processes in its upper atmosphere. These
hydrocarbons condense to form a global smog layer and eventually rain
down onto the surface. The Cassini orbiter will use onboard radar to
peer through Titan's clouds and determine if there is liquid on the
surface. Experiments aboard both the orbiter and the entry probe will
investigate the chemical processes that produce this unique atmosphere.
|Key Scheduled Dates for the Cassini Mission|
| 10/06/97 - Titan IV/Centaur Launch|
| 04/21/98 - Venus 1 Gravity Assist|
| 06/20/99 - Venus 2 Gravity Assist|
| 08/16/99 - Earth Gravity Assist|
| 12/30/00 - Jupiter Gravity Assist|
| 06/25/04 - Saturn Arrival|
| 11/06/04 - Probe Separation|
| 11/27/04 - Titan Probe Entry|
| 06/25/08 - End of Primary Mission|
(Cassini Home Page from JPL; another Cassini page from JPL; Cassini page from NASA PDS; more info from JPL; fact sheets from NASA Spacelink; info on the Doppler Wind Experiment on Huygens)
- Stardust will fly close to a comet and, for the first time ever, bring
material from the comets coma back to Earth for analysis by scientists worldwide.
Scheduled to fly-by Comet Wild-2 in 2004, return to Earth in 2006.
- Pluto Express
- (was Pluto Fast Fly-by) a small, fast, relatively
look at the as yet unvisited Pluto.
Possible launch in 2001 (if a 1998 new start is
authorized). Calls for launch of two spacecraft weighing less
than 100 kg
using Titan IV/Centaur or Proton (possibly with additional solid
kick stages) in 2001 and encounters with Pluto and
around 2006-8 (depending on trajectory choice).
Flybys would be at 12-18 km/second; data would be
recorded onboard the probes during the short encounters and
returned to Earth slowly (due to low power, small antenna sizes,
and large distances) over the next year or so. Russian "Drop
Zond" probes to sample the atmosphere may be included as well.
Science objectives include characterizing global geology and
geomorphology of Pluto and Charon, mapping both sides of each
body, and characterizing Pluto's atmosphere (the atmosphere is
freezing out as Pluto moves away from the Sun, so launching
early and minimizing flight time is critical for this
objective). The 7 kilogram instrument package might include a
CCD imaging camera, IR mapping spectrometer, UV spectrometer,
and radio science occultation experiments.
The PFF spacecraft would be highly a miniaturized descendant of
the present class of outer solar system platforms, breaking the
trend of increasingly complex and expensive probes such as
Galileo and Cassini.
There's an article about PFF by its designers in the Sep/Oct 1994
issue of The Planetary Report, the
bimonthly newsletter from The Planetary Society.
Funding for this project is very much in doubt.
(more info from NASA;
Pluto Express home page;
Pluto Express Science)
- Mercury Polar Flyby
- As a result of renewed interest in Mercury, there are two related proposals being
developed as potential Discovery class missions. Discovery is NASA's new
"cheaper, better, faster" line of solar system exploration spacecraft. These
missions are capped at $150 million total mission costs.
The two Mercury
proposals are the Mercury Polar Flyby (MPF) and Hermes (Mercury orbiter).
MPF's instruments include a neutron spectrometer (water detection), dual
polarization radar (subsurface ice mapping), camera (imaging polar region and
hemisphere not imaged by Mariner 10). We believe a flyby is cheaper and
more technically feasible. MPF is designed to have multiple Mercury encounters
at aphelion only. At aphelion a spacecraft only has to endure the equivalent of
four times the Earth solar flux. The orbit of Mercury is eccentric such that at
perihelion there is eleven times Earth solar flux. An orbiter would have to
endure such conditions requiring elaborate (and expensive) cooling and thermal
Hermes is a joint effort between JPL and TRW.
If it is approved, it will be launched in 1999.
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