Rosetta is a robotic spacecraft of the European Space Agency on a mission to study the comet 67P/Churyumov–Gerasimenko. Rosetta consists of two main elements:

• the Rosetta space probe;
• the Philae lander.

The spacecraft was launched on 2 March 2004 on an Ariane 5 rocket and will reach the comet by mid 2014. The space probe is intended to orbit and perform long-term exploration of the comet at close quarters. On 10 November 2014 the Philae lander will attempt to land and perform detailed investigations on the comet's surface. Both the probe and the lander carry a large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted.

The probe is named after the Rosetta Stone, as it is hoped the mission will help form an idea of how the solar system looked before planets formed. The lander is named after the Nile island Philae where an obelisk was found that helped decipher the Rosetta Stone. The spacecraft has already performed two successful asteroid flyby missions on its way to the comet. In 2007 performed a Mars swingby (flyby), and returned images. The craft completed its fly-by of asteroid 2867 Šteins in September 2008 and of 21 Lutetia in July 2010, and is presently (2013) in hibernation and on-target for its final destination as of June 2013.

SMOS — the second Earth Explorer mission launched on November 2009 designed to measure Soil Moisture and Ocean Salinity.

The Soil Moisture and Ocean Salinity Satellite (SMOS) is a part of ESA's Living Planet Programme intended to provide new insights into Earth's water cycle and climate. In addition, it will provide better weather forecasting and will also monitor snow and ice accumulation.

Planck —  a  Cosmic Microwave Background explorer, after COBE & WMAP. launched in may 2009.

Planck is a space observatory of the European Space Agency (ESA) and designed to observe the anisotropies of the cosmic microwave background (CMB) over the entire sky, at a high sensitivity and angular resolution. Planck was built in the Cannes Mandelieu Space Center by Thales Alenia Space and created as the third Medium-Sized Mission (M3) of the European Space Agency's Horizon 2000 Scientific Programme. The project, initially called COBRAS/SAMBA, is named in honour of the German physicist Max Planck (1858–1947), who won the Nobel Prize for Physics in 1918.

Planck was launched in May 2009, reaching the Earth/Sun's L₂ Lagrangian point in July, and by February 2010 had successfully started a second all-sky survey. Preliminary data from these surveys have been released, and results are said to indicate that the data quality is excellent. Planck is expected to yield definitive data on a number of astronomical issues by 2012. The mission will complement and improve upon observations made by the NASA Wilkinson Microwave Anisotropy Probe (WMAP), which has measured the anisotropies at larger angular scales and lower sensitivity than Planck. Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early universe and the origin of cosmic structure.

The mission has a wide variety of scientific aims, including:

• High resolution detections of both the total intensity and polarization of the primordial CMB anisotropies
• Creation of a catalogue of galaxy clusters through the Sunyaev-Zel'dovich effect
• Observations of the gravitational lensing of the CMB, as well as the integrated Sachs–Wolfe effect
• Observations of bright extragalactic radio (active galactic nuclei) and infrared (dusty galaxy) sources
• Observations of the Milky Way, including the local interstellar medium, distributed synchrotron emission and measurements of the galactic magnetic field.
• Studies of the local Solar System, including planets, asteroids, comets and the zodiacal light.

INTEGRAL  is the first space observatory that can simultaneously observe objects in gamma rays, X-rays and visible light.

The European Space Agency's INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) is an operational Earth satellite, launched in 2002 for detecting some of the most energetic radiation that comes from space. It is the most sensitive gamma ray observatory ever launched.

INTEGRAL is an ESA mission in cooperation with the Russian Space Agency and NASA. It has had some notable successes, for example in detecting a mysterious 'iron quasar'. It has also had great success in investigating gamma-ray bursters and evidence for black holes.

The Hubble Space Telescope (HST) is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter (7.9 ft) aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared. The telescope is named after the astronomer Edwin Hubble.

Hubble's orbit outside the distortion of Earth's atmosphere allows it to take extremely sharp images with almost no background light. Hubble's Ultra-Deep Field image, for instance, is the most detailed visible-light image ever made of the universe's most distant objects. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.

Although not the first space telescope, Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. The HST was built by the United States space agency NASA, with contributions from the European Space Agency, and is operated by the Space Telescope Science Institute. The HST is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.

Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster. When finally launched in 1990, scientists found that the main mirror had been ground incorrectly, significantly compromising the telescope's capabilities. However, after a servicing mission in 1993, the telescope was restored to its intended quality.

Hubble is the only telescope designed to be serviced in space by astronauts. Between 1993 and 2002, four missions repaired, upgraded, and replaced systems on the telescope, but a fifth mission was canceled on safety grounds following the Columbia disaster. However, after spirited public discussion, NASA administrator Mike Griffin approved one final servicing mission, completed in 2009. The telescope is now expected to function until at least 2014. Its scientific successor, the James Webb Space Telescope (JWST), is to be launched in 2018 or possibly later.

A space telescope observing in the far-infrared.

The Herschel Space Observatory is a European Space Agency space observatory sensitive to the far infrared and submillimetre wavebands. It is the largest infrared space telescope ever launched, carrying a single mirror of 3.5 metres (11.5 ft) in diameter.

The observatory was carried into orbit in May 2009, reaching the second Lagrangian point (L2) of the Earth-Sun system, 1,500,000 kilometres (930,000 mi) from the Earth, about two months later. Herschel is named after Sir William Herschel, the discoverer of the infrared spectrum and planet Uranus.

The Herschel Observatory is capable of seeing the coldest and dustiest objects in space; for example, cool cocoons where stars form and dusty galaxies just starting to bulk up with new stars. The observatory will sift through star-forming clouds—the "slow cookers" of star ingredients—to trace the path by which potentially life-forming molecules, such as water, form. The United States through NASA is participating in the ESA-built and -operated observatory. It is the fourth 'cornerstone' mission in the ESA science program, along with Rosetta, Planck, and the Gaia mission.

A mission designed to measure the Earth's gravity field, launched on march 2009.

The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) is an ESA satellite that was launched on March 17, 2009. It is a satellite carrying a highly sensitive gravity gradiometer which detects fine density differences in the crust and oceans of the Earth.

GOCE data will have many uses, probing hazardous volcanic regions and bringing new insight into ocean behaviour. The latter, in particular, is a major driver for the mission. By combining the gravity data with information about sea surface height gathered by other satellite altimeters, scientists will be able to track the direction and speed of geostrophic ocean currents. The low orbit and high accuracy of the system will greatly improve the known accuracy and spatial resolution of the geoid (the theoretical surface of equal gravitational potential on the Earth).

The satellite's arrow shape and fins help keep the GOCE stable as it flies through the wisps of air still present at an altitude of 260 km. In addition, an ion propulsion system continuously compensates for the deceleration of air-drag without the vibration of a conventional chemically-powered rocket engine, thus restoring the path of the craft as closely as possible to a purely inertial trajectory. The craft's primary instrument is three pairs of highly sensitive accelerometers which measure gravitational gradients along three different axes.

GIOVE, or Galileo In-Orbit Validation Element, is the name for each satellite in a series being built for the European Space Agency (ESA) to test technology in orbit for the Galileo positioning system.

Giove is the Italian word for "Jupiter". The name was chosen as a tribute to Galileo Galilei, who discovered the first four natural satellites of Jupiter, and later discovered that they could be used as a universal clock to obtain the longitude of a point on the Earth's surface.

The GIOVE satellites are exploited by the GIOVE Mission (GIOVE-M) segment in the frame of the risk mitigation for the In Orbit Validation (IOV) of the Galileo positioning system.

GIOVE-A2

With the delays of GIOVE-B, the European Space Agency again contracted with SSTL for a second satellite, to ensure that the Galileo programme continues without any interruptions that could lead to loss of frequency allocations. Construction of GIOVE-A2 was terminated due to the successful launch and in-orbit operation of GIOVE-B.

GIOVE, or Galileo In-Orbit Validation Element, is the name for each satellite in a series being built for the European Space Agency (ESA) to test technology in orbit for the Galileo positioning system.

Giove is the Italian word for "Jupiter". The name was chosen as a tribute to Galileo Galilei, who discovered the first four natural satellites of Jupiter, and later discovered that they could be used as a universal clock to obtain the longitude of a point on the Earth's surface.

The GIOVE satellites are exploited by the GIOVE Mission (GIOVE-M) segment in the frame of the risk mitigation for the In Orbit Validation (IOV) of the Galileo positioning system.

GIOVE-B (previously called GSTB-V2/B), has a similar mission, but has greatly improved signal generation hardware.

It was originally built by satellite consortium European Satellite Navigation Industries, but following re-organization of the project in 2007, the satellite prime contractor responsibility was passed to Astrium.

GIOVE-B also has MEO environment characterization objectives, as well as signal-in-space and receiver experimentation objectives. GIOVE-B carries three atomic clocks: two rubidium standards and the first space-qualified passive hydrogen maser.

Launched on 27 April 2008

GIOVE, or Galileo In-Orbit Validation Element, is the name for each satellite in a series being built for the European Space Agency (ESA) to test technology in orbit for the Galileo positioning system.

Giove is the Italian word for "Jupiter". The name was chosen as a tribute to Galileo Galilei, who discovered the first four natural satellites of Jupiter, and later discovered that they could be used as a universal clock to obtain the longitude of a point on the Earth's surface.

The GIOVE satellites are exploited by the GIOVE Mission (GIOVE-M) segment in the frame of the risk mitigation for the In Orbit Validation (IOV) of the Galileo positioning system.

GIOVE-A

Previously known as GSTB-V2/A, this satellite was constructed by Surrey Satellite Technology Ltd (SSTL).

Its mission has the main goal of claiming the frequencies allocated to Galileo by the ITU. It has two independently-developed Galileo signal generation chains and also tests the design of two on-board rubidium atomic clocks and the orbital characteristics of the intermediate circular orbit for future satellites.

GIOVE-A is the first spacecraft whose design is based upon SSTL's new Geostationary Minisatellite Platform (GMP) satellite bus, intended for geostationary orbit. GIOVE-A is also SSTL's first satellite outside low Earth orbit, operating in medium Earth orbit), and is SSTL's first satellite to use deployable sun-tracking solar arrays. Previous SSTL satellites use body-mounted solar arrays, which generate less power per unit area as they do not face the sun directly.

Launched on 28 December 2005

It was launched at 05:19 UTC on December 28, 2005 on a Soyuz-FG/Fregat from the Baikonur Cosmodrome in Kazakhstan.

It began communicating as planned at 09:01 UTC while circling the Earth at a height of 23,222 km. The satellite successfully transmitted its first navigation signals at 17:25 GMT on 12 January 2006. These signals were received at Chilbolton Observatory in Hampshire, UK and the ESA Station at Redu in Belgium. Teams from SSTL and ESA have measured the signal generated by GIOVE-A to ensure it meets the frequency-filing allocation and reservation requirements for the International Telecommunication Union (ITU), a process that was required to be complete by June 2006.

The GIOVE-A signal in space is fully representative of the Galileo signal from the point of view of frequencies and modulations, chip rates, and data rates. However, GIOVE-A can only transmit at two frequency bands at a time (i.e., L1+E5 or L1+E6).

GIOVE-A codes are different from Galileo codes. The GIOVE-A navigation message is not representative from the structure and contents viewpoint (demonstration only purpose). The generation of pseudorange measurements and detailed analysis of the tracking noise and multipath performance of GIOVE-A ranging signals have been performed with the use of the GETR (Galileo Experimental Test Receiver) designed by Septentrio.

There has been some public controversy about the open source nature of some of the Pseudo-Random Noise (PRN) codes. In the early part of 2006, researchers at Cornell monitored the GIOVE-A signal and extracted the PRN codes. The methods used and the codes which were found were published in the June 2006 issue of GPS World. ESA has now made the codes public.