Happy Birthday, ESA!

The European Space Agency (ESA) is celebrating its 50th anniversary. Most EU states are members of ESA - which is good because ESA is financed via the EU, Germany and France. Join us for a look back at the last 50 years for some of ESA's biggest missions - some of which are taking the organization into its next half century.

ESA's first mission in space was with the satellite COS-B from 1975 to 1982. Its name stands for Cosmic Ray Satellite B. And the mission was to research gamma rays in space. The highly-energized gamma rays are emitted when radioactive elements decay. COS-B was used to map gamma rays in the milky way for the first time.

Five years later, in 1990, ESA launched its Ulysses spacecraft to study the sun - the polar regions of the sun, its magnetic field, and the solar wind. It was one of many missions which ESA has since done with its American counterpart, NASA.

Another joint project with NASA is the space telescope, Hubble. Since the 90s, Hubble has delivered wonderful shots from deepest space, and it's still in operation. But by 2018, Hubble could be relieved of its duties by the James Webb space telescope.

ESA's space port is located in Kourou in French Guiana. For its launcher system, ESA uses the Ariane 5 rocket, which was developed especially for the job. But in 1997, the first launch with an Ariane 5 rocket failed. It exploded due to a software error.

The Huygens probe is part of yet another ESA-NASA project. After traveling for almost eight years, Huygens landed on Saturn's largest moon, Titan, in 2005. It took photos of Titan's surface and conducted chemical analyses. It is the first probe to have landed on the surface of a moon at the furthest reaches of the solar system.

In 2003, ESA started its Mars Express mission - Europe's first Mars probe. It's carrying equipment to help it look for water on Mars, and it's still going strong.

The research satellite Cryosat was supposed to measure the thickness of the polar ice caps. But due to a problematic navigation algorithm, the satellite failed to reach its orbit and crashed in 2005 in the Arctic Ocean. ESA launched a replacement satellite, the Cryosat-2, in 2010.

It is hoped the satellite navigation system Galileo will deliver exact positioning data. In fact, it is hoped Galileo will be more precise than the American system, GPS. Galileo is a joint project between ESA and the European Union and it consists of a number of satellites. But on August 22, 2014, two of the satellites - Doresa and Milena - were released into the wrong orbit.

Two of the most recent additions in space are the Earth observation satellites Sentinel-1 A and B. They were launched this year. Using radar, the satellites observe Earth from a height of 700 kilometers. The data are freely accessible. They could be used in early warning systems for extreme weather, or to help make shipping safer.

In 2008, ESA sent its space laboratory Columbus to the International Space Station (ISS). Scientists are hard at work in the multipurpose lab - under zero gravity conditions. The German ESA astronaut Alexander Gerst is among them.

One of the most talked about - and current - ESA missions is Rosetta. After a ten-year flight, it's hoped Rosetta will drop its Philae lander on the comet 67P/Churyumov-Gerasimenko to get a closer look. It will be a tricky little number!