Missions currently in progress:

Cassini
-This mission's objective is to perform a detailed study of Saturn, it's Rings, Magnetosphere, it's Icy Satellites, and it's moon, Titan.
Launched October 15, 1997

Compton Gamma Ray Observatory (CGRO)
-This is the second of NASA's Great Observatories, studying solar flares, cosmic gamma-ray bursts, pulsars, nova and supernova explosions, accreting black holes of stellar dimensions, quasar emission and interactions of cosmic rays with the interstellar medium.
Launched April 5, 1991

Galileo
-Galileo's objective is to study Jupiter, focusing on it's atmosphere, satellites and surrounding magnetosphere.
Launched October 18, 1989 - Jupiter arrival December 7, 1995

Geotail
-The primary objective of this mission is to study the tail of the Earth's magnetosphere. The information gathered during the Geotail mission will allow scientists to model and more accurately predict Sun-Earth interactions.
Launched July 24, 1992

Hubble Space Telescope (HST)
-HST is a long lived space-based observatory for the benefit of the international astronomical community. HST has generated a continuing stream of major scientific discoveries throughout it's history in space.
Launched April 24, 1990 - next Servicing Mission launch December 1999

Interball
-The INTERBALL Project is designed to study various plasma processes in the circumterrestrial space as the principal way to study solar-terrestrial physical processes. The Project consists of two pairs (satellite-subsatellite) at high altitude orbits: to 200,000 km for the Tail Probe pair and to 20,000 km for the Auroral Probe pair. This Russian-led project involves the efforts of a large, international community.
Tail Probe launch August 1995
Auroral Probe launch August 1996

Lunar Prospector
-Prospector's objective is to answer long-standing questions about the Moon, it's resources, it's structure and it's origins. This information will direct future exploration of the Moon and future utilization of Moon resources.
Launched January 6, 1998

Mars Global Surveyor
-The Mars Global Surveyor has a course of a full Martian year, and during this year it's objective is to return an unprecedented amount of data regarding Mars' atmosphere, magnetic properties and surface features.
Launched November 7, 1996

Near Earth Asteroid Rendezvous (NEAR)
-The first spacecraft to orbit an asteroid, the NEAR mission attempts to answer fundamental questions about the nature and origin of near-Earth objects. These objects contain clues to the nature of early solar system processes.
Launched February 17, 1996

Near Earth Asteroid Tracking (NEAT)
-NEAT is a ground-based system of automated electronic cameras taking inventory of earth-approaching objects down to 1 kilometer in diameter. It is a cooperative program between NASA and the United States Air Force.

Polar
-Polar is part of the ISTP Project and is the second of two NASA spacecraft in the Global Geospace Science (GGS) initiative. GGS is designed to improve the understanding of the flow of energy, mass and momentum in the solar-terrestrial environment with emphasis on "geospace".
Launched February 24, 1996

Solar, Anomalous, and Magnetospheric Particle Explorer(SAMPEX)
-SAMPEX is investigating the composition of local interstellar matter and solar material and the transport of magnetospheric charged particles into the Earth's atmosphere. SAMPEX was the first Small Explorer mission.
Launched July 3, 1992

Solar and Heliospheric Observatory (SOHO)
-SOHO is a joint venture of the European Space Agency and NASA, and is a solar observatory stydying the structure, chemical composion, and dynamics of the solar interior; the structure and dynamics of the outer solar atmosphere; and the solar wind and it's relation to the solar atmosphere.
Launched December 2, 1995

Ulysses
-The Ulysses Mission is the first spacecraft to explore interplanetary space at high solar latitudes. The spacecraft orbits the Sun nearly perpendicular to the plane in which the planets orbit.
Launched Oct. 6, 1990

Voyager Interstellar Mission (VIM)
-The VIM is an extension of the Voyager primary mission that was completed in 1989. This extended mission continues to characterize the outer solar system environment and searches for the heliopause boundary, the outer limits of the Sun's magnetic field and outward flow of the solar wind.
Voyager 1 launched September 5, 1997
Voyager 2 launched August 20, 1977

WIND
-WIND is part of the International Solar-Terrestrial Physics (ISTP) Project, and is the first of two NASA spacecraft in the Global Geospace Science (GGS) initiative. WIND has been in a sunward, multiple double-lunar swingby orbit with a maximum apogee of 250Re during the first two years of operation. this will be followed by a halo orbit at the Earth-Sun L1 point.
Launched November 1, 1994

Missions in Development

Astro-E
-Astro-E is Japan's fifth X-ray Astronomy missions. It is being developed at the Institute of Space and Astronautical Science (ISAS) in collaboration with US (NASA/GSFC, MIT) and Japanese institutions. US contributions to this mission include Goddard Space Flight Center building the X-ray telescopes and micro-calorimeters, and MIT building the four X-ray imaging spectrometers.
Expected Launch: February 2000

Advanced X-Ray Astrophysics Facility (AXAF)
-AXAF is designed to observe X-rays from high energy regions of the universe, such as hot gas in the remnants of exploded stars. The observatory has three major parts:(1) the X-ray telescope, whose mirrors will focus X-rays from celestial objects; (2)the science instruments which record the X-rays so that X-ray images can be produced and analyzed; and (3) the spacecraft, which provides the environment necessary for the telescope and the instruments to work. This will be the most sophisticated X-ray observatory ever built.
Expected Launch: December 1998

Cooperative Astrophysics and Technology Satellite (CATSAT)
-CATSAT is a small scientific satellite mission that is being developed jointly by the University of New Hampshire, Weber State University, and the University of Leicester. It's scientific mission will be to study the origin and nature of Gamma Ray Bursters, seen as one of the most mysterious astrophysical phenomenom. CATSAT will be designed, built and operated by student engineering teams, with professional staff and teaching faculty as mentors.
Expected Launch: 2000

Cluster-II
-The origional Cluster mission (part of the ISTP program) was lost on June 4, 1996 tot he explosion of the Ariane-5 rocket. Cluster-II, the second attempt, has been approved by the European Space Agency and NASA, and as planned, the four spacecraft will carry out three-dimensional measurements in the Earth's magnetosphere, covering both large and small scale phenomena in the sunward and tail regions.
Expected Launch: June 2000

Deep Space 1
-During it's two year primary mission,Deep Space 1 (DS1) will test and perfect 12 new technologies for future missions in the 21st Century. In addition to rigourous testing of the future technologies, the DS1 spacecraft will fly by and collect information about an asteroid, then Mars, and finally a comet. The DS1 mission will be the first to use solar electric ion propultion.
Expected Launch: July 1998

Deep Space 2
-The primary purpose of this mission is to demonstrate key technologies for future planetary exploration while collecting meaningful science data. Scientific objectives include determining if ice is present below the Martian surface, measuring the local atmospheric pressure of Mars and characterizing the thermal properties of the Martian subsurface soil.
Expected Launch: January 1999

FUSE
-FUSE, Far Ultraviolet Spectroscopic Explorer, is a NASA supported astronomy mission to explore the Universe using the technique of high-resolution spectroscopy in the far-ultraviolet spectral region. The Johns Hopkins University has the lead role in developing and operating the mission, in collaboration with other universities, contractors and international partners.
Expected Launch: November 1998

Gravity Probe B-The Relativity Mission
-The goal of this experiment is to precisely measure an effect that is predicted by all viable relativistic theories of gravity, but has yet to be observed. Just as Newton's law of gravity is paralleled by Coulomb's law of electricity, it is also expected that the force between currents of electrical charge, described by Ampere's law, should be paralleled by a force between "currents" of flowing matter. It is this force that has never been directly observed.
Expected Launch: March 2000

International Gamma-Ray Astrophysics Laboratory (INTEGRAL)
-INTEGRAL's mission is dedicated to the fine spectroscopy and fine imaging of celestial gamma-ray sources in the energy range of 15 keV to 10 MeV with concurrent source monitoring in the X-ray and optical energy ranges. The nominal lifetime of the observatory will be 2 years with possible extension to up to 5 years. Most of the observing time will be made available to the worldwide scientific community.
Expected Launch: March 2001

Imager for Magnetopause-to-Aurora Global Exploration (IMAGE)
see also: IMAGE Home Page at Southwest Research Institute
-IMAGE is a MIDEX class mission, selected by NASA in 1996, to study the global response of the Earth's magnetosphere to changes in the solar wind. IMAGE will use neutral atom, ultraviolet, and radio imaging techniques to:

1. Identify the dominant mechanisms for injecting plasma into the magnetosphere on substorm and magnetic storm time scales;
2. Determine the directly driven response of the magnetosphere to solar wind changes; and,
3. Discover how and where magnetospheric plasmas are energized, transported, and subsequently lost during substorms and magnetic storms.

Expected Launch: January 2000

Microwave Anisotropy Probe (MAP)
-Map is a MIDEX class mission, selected by NASA to probe conditions in the early universe. MAP will help to answer three of the most fundamental questions in cosmology:

1. What are the values of the cosmological parameters of the Big Bang theory?
2. How did structures of galaxies form in the universe?
3. When did the first structures of galaxies form?

To answer these questions, MAP will measure temperature fluctuations (anisotropy) of the cosmic microwave background radiation over the entire sky.
Expected Launch: November 2000

RadioAstron
-RadioAstron is led by the Astro Space Center of the Lebedev Physical Institute in Moscow, Russia. This project will put a 10-meter radio telescope into a high elliptical orbit in order to make VLBI observations in conjunction with radio telescopes on the ground. It will be supported by the U.S. SVLBI project.
Expected Launch: TBA

Stardust
-Stardust will be the first U.S. mission dedicated solely to a comet and the first robotic return of extraterrestrial material from outside the orbit of the Moon. It's primary goal is to collect comet dust and volatile samples during a planned close encounter with comet Wild 2 in January of 2004. Additonally, the Stardust spacecraft will also bring back samples of interstellar dust, including the recently discovered dust treaming into the solar system from the direction of Sagittarius.
Expected Launch: February 1999

Sub-millimeter Wave Astronomy Satellite (SWAS)
-The scientific objectives of SWAS are to study the chemical composition, energy balance and structure of interstellar clouds and the processes that lead to the formation of stars and planets. SWAS is part of the Small Explorer program.
Expected Launch: February 1999

Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED)
-TIMED is planned to explore Earth's Mesosphere and Lower Thermosphere (60-180 kilometers), the least explored and understood region of our atmosphere. Advances in remote sensing technology employed by TIMED instrumentation will enable us to explore this region on a global basis from space.
Expected Launch: May 2000

Wide-Field Infrared Explorer (WIRE)
-The objective of the WIRE mission is to answer three questions:

1. What fraction of the luminosity of the Universe at a redshift of 0.5 and beyond is due to starburst galaxies?
2. How fast and in what ways are starburst galaxies evolving?
3. Are luminous protogalaxies common at redshifts less than three?

This will be the first mission to probe these redshifts at far-infrared wavelengths.
Expected Launch: September 1998