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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 sci.space FAQ.
Pioneer 11's RTG power supply is dead. Its last communication with Earth was in November 1995. Pioneer 10 is still functioning (barely) but is no longer being tracked regularly due to budget cutbacks. The last data was received from it on 1997 March 31. 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 plaque bolted to the spacecraft's main frame.
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.
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.
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.
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 aurorae. 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.
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 effect then, 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.
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.
Ground controllers have regained control of the spacecraft, however. Its potential future mission is being considered.
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
Voyager 1 has passed the Pioneer 10 spacecraft and is now the most distant human-made object in space.
evidence of the interior of a gas giant.
Galileo has already returned the first resolved images of two asteroids, 951 Gaspra and 243 Ida, while in transit to Jupiter. It has also returned pictures of the impact of Comet SL9 onto Jupiter from its unique vantage point.
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 most.
Galileo Schedule (times UTC)
----------------
10/18/89 - Launch from Space Shuttle
02/09/90 - Venus Flyby
10/**/90 - Venus Data Playback
12/08/90 - 1st Earth Flyby
05/01/91 - High Gain Antenna (was to have) Unfurled
07/91 - 06/92 - 1st Asteroid Belt Passage
10/29/91 - Asteroid Gaspra Flyby
12/08/92 - 2nd Earth Flyby
05/93 - 11/93 - 2nd Asteroid Belt Passage
08/28/93 - Asteroid Ida Flyby
07/13/95 - Probe Separation
07/20/95 - Orbiter Deflection Maneuver
12/07/95 - Jupiter Encounter
06/27/96 06:30 - Ganymede-1
09/06/96 19:01 - Ganymede-2
11/04/96 13:30 - Callisto-3
11/06/96 18:42 - Europa-3A ("non-targeted" flyby @32,000 km on the
same orbit as Callisto-3)
12/19/96 06:56 - Europa-4
01/20/97 01:13 - Europa-5A (flyby @27,400 km during solar
conjunction - counts for gravity - not science)
02/20/97 17:03 - Europa-6
04/04/97 06:00 - Europa-7A ("non-targeted" @23,200 km on the
Ganymede-7 orbit)
04/05/97 07:11 - Ganymede-7
05/06/97 12:12 - Callisto-8A ("non-targeted" @33,500 km on the
Ganymede-8 orbit)
05/07/97 15:57 - Ganymede-8
06/25/97 13:48 - Callisto-9
06/26/97 17:20 - Ganymede-9A ("non-targeted" @80,000 km on the
Callisto-9 orbit)
09/17/97 00:21 - Callisto-10
11/06/97 21:47 - Europa-11 (more
details)
Galileo's extended mission has been approved. If all goes well, it will spend another two years focusing primarily on Europa.
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 posted regularly. (Here is a brief history of the HST project. There's also some more HST info at JPL.)
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 kilometers).
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 Earth).
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.
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 in an eliptical orbit around Mars. During the year, 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 March 1999.
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 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 Network.
Project costs for the Mars Global Surveyor through 30 days after launch will be approximately $155 million.
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 landed successfully on Mars on 1997 July 4.
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 (VVEJGA Trajectory) ------------------------------------------------------------- 10/15/97 - Titan IV/Centaur Launch 04/26/98 - Venus 1 Gravity Assist 06/24/99 - Venus 2 Gravity Assist 08/18/99 - Earth Gravity Assist 12/30/00 - Jupiter Gravity Assist 07/01/04 - Saturn Arrival 11/06/04 - Probe Separation 11/27/04 - Titan Probe Entry 06/25/08 - End of Primary Mission
The Mars '98 orbiter will arrive at Mars Sept. 23, 1999, while the lander will touch down Dec. 3, 1999.
The lander will land near the southern polar cap and is equipped with cameras, a robotics arm and instruments to measure the composition of the Martian soil. Two small microprobes are also piggybacking on the lander, which will penetrate into the Martian subsurface to detect water ice.
The science package for the lander includes the Mars Volatile and Climate Surveyor (MVACS) integrated lander payload, the Mars Descent Imager (MARDI) and an atmospheric lidar experiment provided by the Russian Space Agency Institute for Space Science. The integrated lander payload includes a surface stereo imager with Mars Pathfinder heritage; a meteorology package; an instrumented robotic arm for sample acquisition, soil manipulation and closeup imaging of the surface and subsurface; and the thermal and evolved gas analysis experiment for determining the nature and abundance of volatile material in the Martian soil.
The images obtained while the lander descends to the surface will establish the geological and physical context of the landing site. The atmospheric lidar experiment will determine the dust content of the Martian atmosphere above the landing site.
Pluto-Kuiper Express
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.
This innovative mission will use new flight technology, including solar electric propulsion, to send a spacecraft to asteroid 4660 Nereus and deliver a JPL-developed rover, which measures about the size of a shoebox, to the asteroid's surface. The Muses-C spacecraft will also fire explosive charges into the asteroid, collect the samples that are ejected from the impacts, and return the samples to Earth in a capsule for laboratory analysis. The mission is scheduled for launch in 2002.
Hermes is a joint effort between JPL and TRW. If it is approved, it will be launched in 1999.
(All missions not otherwise labeled are NASA)
