Galileo is a joint initiative of the European Commission (EC) and the European Space Agency (ESA). Galileo will be Europe’s own global navigation satellite system, providing a highly accurate, guaranteed global positioning service under civilian control. It will be inter-operable with GPS and GLONASS, the two other GNSS (Global Navigation Satellite Systems). The complete system consists of:

• A space segment of 30 MEO satellites in 3 planes inclined at 56º

• A launch segment to place the satellites into their operational orbits

• A control ground segment for monitoring and control of the satellites

• A mission ground segment managing all mission specific data

• A user ground segment of equipment capable of receiving and using Galileo signals

The Galileo spacecraft was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. Named after the astronomer and Renaissance pioneer Galileo Galilei, it was launched on October 18, 1989 by the Space Shuttle Atlantis on the STS-34 mission. It arrived at Jupiter on December 7, 1995, a little more than six years later, via gravitational assist flybys of Venus and Earth.

Despite suffering from antenna problems, Galileo conducted the first asteroid flyby near 951 Gaspra, discovered the first asteroid moon, Dactyl, around the asteroid 243 Ida, and was the first spacecraft to orbit Jupiter. It furthermore launched the first probe into Jupiter's atmosphere.

The spacecraft measured the atmospheric composition of Jupiter and directly observed ammonia clouds, which seem to be created by an outflow from the lower depths of Jupiter's atmosphere. Galileo also registered Io's volcanism and the plasma interactions between its and Jupiter's atmospheres. Other studies gave support for the popular theory of liquid oceans under the icy surface of Europa. There were also indications of similar liquid-saltwater layers under the surfaces of Ganymede and Callisto, while Ganymede was shown to possess a magnetic field. New evidence was also found for the existence of exospheres around Europa, Ganymede, and Callisto.

It was furthermore discovered that Jupiter's faint ring system is formed by dust from impacts on the four small inner moons. The extent and structure of Jupiter's magnetosphere was also mapped.

Galileo also provided the only direct observation of Comet Shoemaker-Levy 9's impact into the atmosphere of Jupiter in 1994.

On September 21, 2003, after 14 years in space and 8 years of service in the Jovian system, Galileo's mission was terminated by sending the orbiter into Jupiter's atmosphere at a speed of nearly 50 kilometres per second to avoid any chance of it contaminating local moons with bacteria from Earth. Of particular concern was the ice-crusted moon Europa, which, thanks to Galileo, scientists now suspect harbors a potentially life-supporting saltwater ocean beneath its surface.

MetOp is a series of three polar orbiting meteorological satellites operated by EUMETSAT, the European Organisation for the Exploitation of Meteorological Satellites.

The satellites form the space segment component of the overall EUMETSAT Polar System (EPS), which in turn is the European half of the EUMETSAT/NOAA Initial Joint Polar System (IJPS). The satellites carry a payload comprising 11 scientific instruments and two which support Search and Rescue services. In order to provide data continuity between MetOp and NOAA Polar Operational Satellites (POES), several instruments are carried on both fleets of satellites.

(ex   Marconi Space and Defence Systems)

Marconi Electronic Systems (MES), or GEC-Marconi as it was until 1998, was the defence arm of The General Electric Company (GEC). It was demerged from GEC and acquired by British Aerospace (BAe) on November 30, 1999 to form BAE Systems. GEC then renamed itself Marconi plc.

MES exists today as BAE Systems Electronics Limited, a subsidiary of BAE Systems, but the assets were rearranged elsewhere within that company. MES-related businesses include BAE Systems Submarine Solutions, BAE Systems Surface Ships, BAE Systems Insyte and SELEX Galileo (now owned by Finmeccanica).

other owned organisations:

• Marconi Avionics
• Marconi North America
• Marconi Naval Systems
• Alenia Marconi Systems (AMS)
• Matra Marconi Space
• Thomson Marconi Sonar
• Marconi Research Centre

Synthetic-aperture radar (SAR) is a form of radar whose defining characteristic is its use of relative motion between an antenna and its target region to provide distinctive long-term coherent-signal variations that are exploited to obtain finer spatial resolution than is possible with conventional beam-scanning means. It originated as an advanced form of side-looking airborne radar (SLAR).

SAR is usually implemented by mounting, on a moving platform such as an aircraft or spacecraft, a single beam-forming antenna from which a target scene is repeatedly illuminated with pulses of radio waves at wavelengths anywhere from a meter down to millimeters. The many echo waveforms received successively at the different antenna positions are coherently detected and stored and then post-processed together to resolve elements in an image of the target region.

Current (2010) airborne systems provide resolutions to about 10 cm, ultra-wideband systems provide resolutions of a few millimeters, and experimental terahertz SAR has provided sub-millimeter resolution in the laboratory.

SAR images have wide applications in remote sensing and mapping of the surfaces of both the Earth and other planets. SAR can also be implemented as "inverse SAR" by observing a moving target over a substantial time with a stationary antenna.

Astrium is an aerospace subsidiary of the European Aeronautic Defence and Space Company (EADS). It provides civil and defence space systems and services.

In 2008, Astrium had a turnover of €4.3 billion and 15,000 employees in France, Germany, the United Kingdom, Spain and the Netherlands.

The Global Positioning System (GPS) is a space-based satellite navigation system that provideslocation and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. It is maintained by the United Statesgovernment and is freely accessible by anyone with a GPS receiver with some technical limitations which are only removed for military users.

The GPS program provides critical capabilities to military, civil and commercial users around the world. It is an engine of economic growth and jobs, and has generated billions of dollars of economic activity. It maintains future warfighter advantage over opponents and is one of the four core military capabilities. In addition, GPS is the backbone for modernizing the global air traffic system.

The GPS project was developed in 1973 to overcome the limitations of previous navigation systems, integrating ideas from several predecessors, including a number of classified engineering design studies from the 1960s. GPS was created and realized by the U.S. Department of Defense (DoD) and was originally run with 24 satellites. It became fully operational in 1994.

Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS system and implement the next generation of GPS III satellites and Next Generation Operational Control System (OCX). Announcements from the Vice President and the White House in 1998 initiated these changes. In 2000, U.S. Congress authorized the modernization effort, referred to as GPS III.

In addition to GPS, other systems are in use or under development. The Russian GLObal NAvigation Satellite System (GLONASS) was in use by only the Russian military, until it was made fully available to civilians in 2007. There are also the planned European Union Galileo positioning system, Chinese Compass navigation system, and Indian Regional Navigational Satellite System.

GLONASS is a radio-based satellite navigation system operated for the Russian government by the Russian Space Forces. It both complements and provides an alternative to the United States' Global Positioning System (GPS), the Chinese Compass navigation system and the planned Galileo positioning system of the European Union.

Development of GLONASS began in the Soviet Union in 1976. Beginning on 12 October 1982, numerous rocket launches added satellites to the system until the "constellation" was completed in 1995. In the first decade of the 21st century, under Vladimir Putin's presidency, the restoration of the system was made a top government priority and funding was substantially increased. GLONASS is currently the most expensive program of the Russian Federal Space Agency, consuming a third of its budget in 2010.

By 2010, GLONASS had achieved 100% coverage of Russia's territory and in October 2011, the full orbital constellation of 24 satellites was restored, enabling full global coverage. The GLONASS satellites designs have undergone several upgrades, with the latest version being GLONASS-K.

Sputnik, a Russian word meaning "companion" or "satellite", is a name applied to certain spacecraft launched under the Soviet space program. "Sputnik 1", "Sputnik 2" and "Sputnik 3" were the official Soviet names of those objects, while the remaining designations in the series ("Sputnik 4" and so on) were not official names, but were names applied in the West, to objects whose original Soviet names may not have been known at the time.

The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. It was named in honor of Indian-American physicist Subrahmanyan Chandrasekharwho is known for determining the maximum mass for white dwarfs. "Chandra" also means "moon" or "luminous" in Sanskrit.

Chandra Observatory is the third of NASA's four Great Observatories. The first was Hubble Space Telescope; second the Compton Gamma Ray Observatory, launched in 1991; and last is the Spitzer Space Telescope. Prior to successful launch, the Chandra Observatory was known as AXAF, the Advanced X-ray Astrophysics Facility. AXAF was assembled and tested by TRW (now Northrop Grumman Aerospace Systems) in Redondo Beach,California. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, due primarily to the high angular resolution of the Chandra mirrors.

Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes, requiring a space-based telescope to make these observations.