Space probes: Pushing the envelope (images)

On March 1 2002, the European Space Agency sent into space the world's largest Earth observation satellite, Envisat. In the last decade, the eight-ton satellite circled the Earth more than 50 000 times. This shot taken last month by Envisat shows a rare view of Italy: almost all of the country is covered with snow.

But Envisat is just one of dozens of probes already aloft-or planned for launch into-space to further science's knowledge of the Earth, the Sun, and the rest of our solar system.

The Voyager 1 spacecraft recently entered a new region between our solar system and interstellar space. Voyager 1 and its identical twin, Voyager 2, both launched in 1977. At last look, Voyager 1 was 11 billion miles away from the sun, while Voyager 2 was about 9 billion miles away.

NASA's Solar Dynamics Observatory recently celebrated its second year in space, where it has been capturing millions of images -- including solar flares, coronal mass ejections, filament eruptions, and other space weather phenomena -- and relaying them to astrophysicists back at NASA's Goddard Space Flight Center.

The Stereo space observatory -- there are actually a couple of them out there -- has delighted astrophysicists since 2006 with images like these of the sun's solar activity. Stereo, an acronym for Solar Terrestrial Relations Observatory, is a mission to study the Sun and related coronal mass ejections.

Artist rendition of the FastSat spacecraft (FastSat is an acronym for "fast, affordable, science and technology satellite"). In an age of budgetary constraints, this was NASA's attempt to prove it could build a low-cost satellite to conduct experiements in space. Since launching in November 2010, FastSat has turned in an impressive record. Perhaps its most noted experiment involved the January 2011 deployment of a compact solar sail boom.

The Artemis spacecraft depicted in flight around the Moon. Two such craft -- the acronym refers to acceleration, reconnection, turbulence and electrodynamic -- spent about a year and a half traveling to the Moon where they settled down to orbit points on either side of the planet at the point where the moon's and Earth's gravity balance perfectly.

Since its 2008 launch, the IBEX spacecraft has been circling the Earth and searching out particles streaming in from beyond our solar system. These so-called neutral "alien" particles enter our solar system from interstellar space. The work, slated to finish in 2011, was deemed so successful that NASA extended IBEX's mission to 2013.

The Solar Probe Plus will be the first spacecraft to fly into the Sun's corona, circling the orb at approximately 450,000 miles per hour. The car-sized craft is expected to encounter temperatures approaching 2,600 degrees Fahrenheit, or 2,000 degrees Celsius. Launch is slated no later than 2018.

When they launch in 2014, the four identically instrumented MMS spacecraft-Magnetospheric Multiscale Mission-will help clear up a scientific debate. The crafts will explore what happens after magnetic lines of force cross, cancel and reconnect. This process of magnetic reconnection is responsible for solar flares that have the equivalent energy of several atomic bombs.

Slated for an August 2012 launch, a couple of craft known as Radiation Belt Storm Probes, or RBSP, will study the environment of the radiation belts that surround Earth.

Graphic of the proposed IRIS spacecraft. Slated for a December 2012 launch, the craft's planned two-year mission is to measure the Sun's flow of energy.

The European Space Agency is developing a satellite called the Solar Orbiter to study solar wind as well as the polar regions of the Sun. The craft is expected to launch in January 2017.

In its decade of operation, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has tracked more than 40,000 X-ray solar flares.

A collaborative effort between the United States, Japan and the United Kingdom, the Hinode (Solar-b) spacecraft has been observing the Sun since 2006.

NASA's Spitzer Space Telescope took this extraordinary image of a baby star sprouting two identical jets. It was launched in August 2003 and has since been drifting in a Earth-trailing orbit around the Sun. If you want to track where Spitzer is right now, click here.