Cluster II is a space mission of the European Space Agency, with NASA participation, to study the Earth's magnetosphere over the course of an entire solar cycle.

The mission is composed of four identical spacecraft flying in a tetrahedral formation. A replacement for the original Cluster spacecraft which were lost in a launch failure in 1996, the four Cluster II spacecraft were successfully launched in pairs in July and August 2000 onboard two Soyuz-Fregat rockets from Baikonur. In February 2011, Cluster II celebrated 10 years of successful scientific operations in space.

The mission has been extended until December 2012.

China National Space Administration/ESA Double Star mission operated alongside Cluster II from 2003 to 2007.

The four identical Cluster II satellites study the impact of the Sun's activity on the Earth's space environment by flying in formation around Earth. For the first time in space history, this mission is able to collect three-dimensional information on how the solar wind interacts with the magnetosphere and affects near-Earth space and its atmosphere, including aurorae.

The satellites are named Rumba, Salsa, Samba and Tango but are more commonly called Cluster 1, Cluster 2, Cluster 3 and Cluster 4 or even C1, C2, C3 and C4.

The spacecraft are cylindrical (290 x 130 cm, see online 3D model) and are spin-stabilized at 15 rotations per minute. After launch, their solar cells provided 224 watts power for instruments and communications. The four spacecraft maneuver into various tetrahedral formations to study the magnetospheric structure and boundaries. The inter-spacecraft distances can be varied from around 17 to 10,000 kilometers (km). The propellant for the maneuvers makes up approximately half of the spacecraft's launch weight.

The highly elliptical orbits of the spacecraft reach a perigee of around 4 R_E (Earth radii, where 1 R_E = 6371 km) and an apogee of 19.6 R_E. Each orbit takes approximately 57 hours to complete. The European Space Operations Centre (ESOC) acquires telemetry and distributes to the online data centers the science data from the spacecraft.

Cluster I was a constellation of four European Space Agency spacecraft which were launched on the maiden flight of the Ariane 5 rocket, Flight 501, and subsequently lost when that rocket failed to achieve orbit.

The launch, which took place on June 4, 1996, ended in failure due to an error in the software design caused by inadequate protection from integer overflow. This resulted in the rocket veering off its flight path 37 seconds after launch, beginning to disintegrate under high aerodynamic forces, and finally self-destructing by its automated flight termination system.

Cluster consisted of four 1,200 kilograms (2,600 lb) cylindrical, spin-stabilised spacecraft, powered by 224 watt solar cells. The spacecraft were to have flown in a tetrahedral formation, and were intended to conduct research into the Earth's magnetosphere. The satellites would have been placed into highly eliptical orbits; 17,200 by 120,600 kilometres (10,700 by 74,900 mi), inclined at 90 degrees to the equator.

Following the failure of Cluster I, four replacement Cluster II satellites were built. 

The Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission was originally a constellation of five NASA satellites to study energy releases from Earth's magnetosphere known as substorms, magnetic phenomena that intensify auroras near Earth's poles. The name of the mission is an acronym alluding to the Titan, Themis.

Now three of the original satellites remain in the magnetosphere, while two have been moved into orbit near the Moon. Those two have been renamed ARTEMIS for Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun, but are also called ARTEMIS P1 (THEMIS B) and ARTEMIS P2 (THEMIS C).

The THEMIS satellites were launched February 17, 2007 from Cape Canaveral Air Force Station Space Launch Complex 17 aboard a Delta II rocket. Each satellite carries identical instrumentation, including a fluxgate magnetometer (FGM), an electrostatic analyzer (ESA), a solid state telescope (SST), a search-coil magnetometer (SCM) and an electric field instrument (EFI). Each has a mass of 126 kg, including 49 kg of fuel.

Launch date 2007-02-17 23:01:00 UTC

Phoenix was a robotic spacecraft on a space exploration mission on Mars under the Mars Scout Program.

The Phoenix lander descended on Mars on May 25, 2008. Mission scientists used instruments aboard the lander to search for environments suitable for microbial life on Mars, and to research the history of water there.

The multi-agency program was headed by the Lunar and Planetary Laboratory at the University of Arizona, under the direction of NASA's Jet Propulsion Laboratory. The program was a partnership of universities in the United States, Canada, Switzerland, Denmark, Germany, the United Kingdom, NASA, the Canadian Space Agency, the Finnish Meteorological Institute, Lockheed Martin Space Systems, MacDonald Dettwiler & Associates (MDA) and other aerospace companies. It was the first mission to Mars led by a public university in NASA history. The mission underscored the value of university-led management. It was led directly from the University of Arizona's campus in Tucson, with project management at the Jet Propulsion Laboratory in Pasadena, Calif., and project development at Lockheed Martin in Denver, Colorado. The operational funding for the mission extended through November 10, 2008.

Phoenix is NASA's sixth successful landing out of seven attempts and is the most recent spacecraft to land successfully on Mars as well as the first successful landing in a Martian polar region. The lander completed its mission in August 2008, and made a last brief communication with Earth on November 2 as available solar power dropped with the Martian winter. The mission was declared concluded on November 10, 2008, after engineers were unable to re-contact the craft. After unsuccessful attempts to contact the lander by the Mars Odyssey orbiter up to and past the Martian summer solstice on May 12, 2010, JPL declared the lander to be dead. Like the two Mars Exploration Rovers, the program was considered a success because it completed all planned science experiments and observations.

IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) is a Japan Aerospace Exploration Agency (JAXA) experimental spacecraft. The spacecraft was launched on 21 May, 2010, aboard an H-IIA rocket, together with the Akatsuki (Venus Climate Orbiter) probe and four other small spacecraft. IKAROS is the first spacecraft to successfully demonstrate solar-sail technology in interplanetary space.

On December 8, 2010, IKAROS passed by Venus at about 80,800 km distance, completing the planned mission successfully, and entered its extended operation phase.

The IKAROS probe is the world's first spacecraft to use solar sailing as the main propulsion. It plans to demonstrate four key technologies (comments in parentheses refer to figure):

1. Deployment and control of a large, thin solar sail membrane (blue areas numbered 3)
2. Thin-film solar cells integrated into the sail to power the payload (black rectangles numbered 4)
3. Measurement of acceleration due to radiation pressure on the solar sail
4. Attitude control via variable reflectance liquid crystal panels (orange rectangles numbered 2)

The mission also includes investigations of aspects of interplanetary space, such as the gamma-ray burst, solar wind and cosmic dust.

The probe's ALADDIN instrument (ALDN-S and ALDN-E) measured the variation in dust density while its Gamma-Ray Burst Polarimeter (GAP) measured the polarization of gamma-ray bursts during its six month cruise.

If successful, IKAROS is to be followed by a 50 m (160 ft) sail, intended to journey to Jupiter and theTrojan asteroids, later in the decade.

The International Space Station (ISS) is a habitable artificial satellite in low Earth orbit. It follows the Salyut, Almaz, Skylab and Mir stations as the ninth space station to be inhabited. The ISS is a modular structure whose first component was launched in 1998. Like many artificial satellites, the station can be seen from Earth with the naked eye. The ISS consists of pressurised modules, external trusses, solar arrays and other elements. ISS components have been launched by American Space Shuttles as well as Russian Proton and Soyuz rockets. Budget constraints led to the merger of three space station projects with the Japanese Kibō module and Canadian robotics. In 1993 the Soviet/Russian Mir-2, the American Freedom, and the European Columbus, merged into a single multi-national programme. The Russian Federal Space Agency plans to separate some of its modules from the Russian segment to form theOPSEK facility before the remainder of the station is deorbited.

The ISS serves as a microgravity and space environment research laboratory in which crew members conduct experiments in biology, human biology, physics, astronomy, meteorology and other fields. The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars.

The station has been continuously occupied for 11 years and 121 days having exceeded the previous record of almost 10 years (or 3,644 days) held by Mir, in 2010. The station is serviced by Soyuz spacecraft,Progress spacecraft, the Automated Transfer Vehicle, the H-II Transfer Vehicle, and formerly the Space Shuttle. It has been visited by astronauts and cosmonauts from 15 different nations.

The ISS programme is a joint project between five participating space agencies, the American NASA, the Russian RKA, the Japanese JAXA, the European ESA, and the Canadian CSA. The ownership and use of the space station is established by intergovernmental treaties and agreements. The station is divided into two sections, the Russian orbital segment (ROS) and the United States orbital segment(USOS), which is shared by many nations. The ISS is maintained at an orbital altitude of between 330 km (205 mi) and 410 km (255 mi). It completes 15.7 orbits per day. The ISS is expected to remain in operation until at least 2020, and potentially to 2028.

The XMM-Newton (X-ray Multi-Mirror Mission - Newton) is an orbiting X-ray observatory launched by ESA in December 1999 on a Ariane 5 rocket. It is named in honor of Sir Isaac Newton.

Its mission is turned towards deep space and aimes to increasing our knowledge of very hot objects created when the Universe was very young, 

Originally known as the High Throughput X-ray Spectroscopy Mission it was placed in a very eccentric 48 hour elliptical orbit at 40°; at its apogee it is nearly 114,000 kilometres (71,000 mi) from Earth, while theperigee is only 7,000 kilometres (4,300 mi)

The satellite weighs 3,800 kilograms (8,400 lb), is 10 metres (33 ft) long and 16 metres (52 ft) in span with its solar arrays deployed. It holds three X-ray telescopes, developed by Media Lario of Italy, each of which contains 58 Wolter-type concentric mirrors. The combined collecting area is 4,300 cm². The three European Photon Imaging Cameras (EPIC) are sensitive over the energy range 0.2 keV to 12 keV. Other instruments onboard are two reflection grating spectrometers which are sensitive below ~2 keV, and a 30 centimetres (12 in) diameter Ritchey-Chretien optical/UV telescope.

The mission was proposed in 1984 and approved in 1985; a project team was formed in 1993 and development work began in 1996. The satellite was constructed and tested from March 1997 to September 1999. Launched in Dec 1999, in-orbit commissioning started Jan 2000. First images published Feb 2000. The original mission lifetime was two years, it has now been extended for further observations until at least 2010, and again until 2012, and technically could operate until 2018.

Observations are managed and archived at the European Space Astronomy Centre (formerly known as VILSPA) at Villafranca, Spain. The data are processed at the XMM-Newton Survey Science Centre at the University of Leicester, England.

The European satellite XMM-Newton (X-ray Multi Mirror), built under contract to ESA by a consortium of 35 European companies with Astrium as prime contractor, by far excels its predecessor, the Astrium-built ROSAT satellite.

The Gravity Recovery And Climate Experiment (GRACE), a joint mission of NASA and the German Space Agency, has been making detailed measurements of Earth's gravity field since its launch in March 2002.

Gravity is determined by mass. By measuring gravity, GRACE shows how mass is distributed around the planet and how it varies over time. GRACE data are important tools for studying Earth's ocean, geology, and climate.

GRACE is a collaborative endeavor involving the Center for Space Research at the University of Texas, Austin; NASA's Jet Propulsion Laboratory, Pasadena, Calif.; the German Space Agency and Germany's National Research Center for Geosciences, Potsdam. The Jet Propulsion Laboratory is responsible for the overall mission management under the NASA ESSP program.

The principal investigator is Dr. Byron Tapley of the University of Texas Center for Space Research, and the co-principal investigator is Dr. Christoph Reigber of the GeoForschungsZentrum (GFZ) Potsdam.

The GRACE satellites were launched from Plesetsk Cosmodrome, Russia on a Rockot (SS-19 + Breeze upper stage) launch vehicle, on March 17, 2002.

GRAIL =Gravity Recovery and Interior Laboratory 

The Gravity Recovery and Interior Laboratory (GRAIL) is an American lunar science mission in NASA's Discovery Program, which will use high-quality gravitational field mapping of the Moon to determine its interior structure. The two small spacecraft GRAIL A and GRAIL B were launched on 10 September 2011 aboard a single launch vehicle: the most-powerful configuration of a Delta II, the 7920H-10. GRAIL A separated from the rocket about nine minutes after launch, GRAIL B followed about eight minutes later. They will arrive at their orbits around the Moon 24 hours apart.

The science phase of the mission will last for 90 days. Following the science phase (or extended mission phase), a five-day decommissioning period is planned, after which the spacecraft will impact the lunar surface in about 40 days.^[6] The gravity mapping technique is similar to that used by Gravity Recovery and Climate Experiment (GRACE), and the spacecraft design is based on XSS-11.

Unlike the Apollo program missions, which took three days to reach the Moon, GRAIL will make use of a three- to four-month low-energy trans-lunar cruise via the Sun-Earth Lagrange point L1 to reduce fuel requirements, protect instruments and reduce the velocity of the two spacecraft at lunar arrival to help achieve the extremely low 50 km (31 mi) orbits with separation between the spacecraft (arriving 24 hours apart) of 175 to 225 km (109 to 140 mi). The very tight tolerances in the flight plan leaves little room for error correction leading to a launch window lasting one second and providing only two launch opportunities per day.

The planned orbital insertion dates are December 31, 2011 (for GRAIL-A) and January 1, 2012 (for GRAIL-B).

NASA's Jet Propulsion Laboratory manages the project. 

The GRAIL mission will place two spacecraft into the same orbit around the Moon. As they fly over areas of greater and lesser gravity, caused both by visible features such as mountains and craters and by masses hidden beneath the lunar surface, they will move slightly toward and away from each other. An instrument aboard each spacecraft will measure the changes in their relative velocity very precisely, and scientists will translate this information into a high-resolution map of the Moon's gravitational field.

This gravity-measuring technique is essentially the same as that of the Gravity Recovery And Climate Experiment (GRACE), which has been mapping Earth's gravity since 2002.
Objectives
GRAIL's engineering objectives are to enable the science objectives of mapping lunar gravity and using that information to increase understanding of the Moon's interior and thermal history. Getting the two spacecraft where they need to be, when they need to be there, requires an extremely challenging set of maneuvers never before carried out in solar system exploration missions. Mission design
The two GRAIL spacecraft will be launched together and then will fly similar but separate trajectories to the Moon after separation from the launch vehicle, taking about 3 to 4 months to get there. They will spend about 2 months reshaping and merging their orbits until one spacecraft is following the other in the same low-altitude, near-circular, near-polar orbit, and they begin formation-flying. The next 82 days will constitute the science phase, during which the spacecraft will map the Moon's gravitational field.
Spacecraft and payload
The two GRAIL spacecraft are near-twins, each about the size of a washing machine, with minor differences resulting from the need for one specific spacecraft (GRAIL-A) to follow the other (GRAIL-B) as they circle the Moon.
The science payload on each spacecraft is the Lunar Gravity Ranging System, which will measure changes in the distance between the two spacecraft down to a few microns -- about the diameter of a red blood cell. Each spacecraft will also carry a set of cameras for MoonKAM, marking the first time a NASA planetary mission has carried instruments expressly for an education and public outreach project.