Space has fascinated mankind for millennia, and in the last century we have explored more of the solar system than we could ever have imagined. Here is a list of the top 10 space missions that often go unmentioned.

1. USA-193

Spy satellites are often subjects of SciFi plots, but this satellite had a more interesting fate than most.

USA-193 was a US military spy satellite launched on December 14th, 2006. It malfunctioned shortly after deployment and was therefore never put to use. Because of this, the U.S. launched an SM-3 missile from a warship that successfully intercepted and destroyed the orbiting satellite on February 21st, 2008. This was in part a display of technological superiority to its eastern competitors, China and Russia.

Developed by Boeing and Lockheed, the satellite weighed more than 2 tonnes and was initially intended to operate as a reconnaissance satellite.

Missile LaunchCredit: U.S. Navy

2. Stardust

With the recent public interest in the Rosetta mission which succeeded in landing a probe on a comet, it is important to remember the role that Stardust played in comet exploration.

On February 7th 1999, NASA launched the Stardust space probe. It's mission was to collect particles of dust from the trail of a comet, and return these samples to Earth. After a flyby of 2 comets, the spacecraft successfully returned to Earth in January 2006. The sample was protected by a heat shield and a parachute, which worked together to slow the probe down from its initial velocity of 12.9 kilometres per second - the fastest re-entry any man-made object has ever achieved.



3. NEAR Shoemaker

The Near - or Near Earth Asteroid Rendezvous - Shoemaker spacecraft made a soft landing on an asteroid on February 12th 2001. The spacecraft continued to operate successfully for nearly a month, although its electronics eventually succumbed to the extreme cold on the asteroid. Temperatures were as low as -173o C (-279o F).

Asteroids pose a great threat to human survival in the long term. As the first to perform a soft landing on an asteroid, this spacecraft confirms the possibility of redirecting asteroids that are on course to collide with earth. However, this would likely require a lot of fuel, or a warning far in advance.

Eros AsteroidCredit: NASA

4. Ulysses

Launched in October 1990, Ulysses enjoyed a 19 year journey and provided us with a plethora of data. While its primary mission was to observe the sun and its poles, a number of comets were encountered and studied.

Most importantly, Ulysses discovered that the intensity of Solar Wind was decreasing, currently at its lowest value ever measured. This finding effects the planned use of solar sails as a future form of spacecraft propulsion.

The original launch of Ulysses was delayed by four years, because of the tragic loss of the Space Shuttle Challenger in the January of 1986 and the subsequent shortage of launch options.

5. Young Engineers Satellite 2

The Young Engineers Satellite 2 was designed and built by students and young engineers. This mission was a huge success in bringing hands-on education into the space engineering field, and also confirmed an important hypothesis about the use of a technology called Space Tethers.

With the CubeSat and other microsatellites being manufactured at an ever-smaller cost, we are beginning to see a new age of engineering education. emerge.

6. Giotto

Halley's Comet has been observed for millennia. It even makes an appearance in the Bayeux Tapestry depicting the French invasion of England, embroidered almost one thousand years ago. Giotto approached Halley in March 1986 and became the first to make observations of a comet at a close range.

Because of its proximity to the comet, Giotto was struck by some of the ejecta from the comet. One of these events caused Giotto to spin into a dangerous orientation. The craft was stabilized after more than half an hour. A camera on the spacecraft was later destroyed by another impact.

7. Don Quijote

The European Space Agency proposed the Don Quijote probe to study the possibility of redirecting or deflecting an asteroid. If successful, we will finally have a method of defence against future extinctions caused by massive asteroid impacts. Although it sounds unlikely, there is strong evidence to suggest that earth has been stuck by asteroids a number of times before, and the ecological implications were severe.

If this plan is carried out the craft may be launched in 2015. It is designed to last for over 7 years. An impactor will collide with an asteroid at around 10 kilometres per second (over 22 thousand miles per hour), and another craft will land near or in the impact crater to investigate the newly revealed comet material.

ImpactCredit: Fredrik (Wikipedia)

8. Deep Impact

The Deep Impact mission, launched in early 2005, performed a similar feat that the Don Quijote hopes to in the near future. A 370kg craft impacted the comet at approximately 10 kilometres per second, an impact that produced a bright flash recorded by another nearby spacecraft. The impactor captured and transmitted an images up to 3 seconds before it impacted the comet. Although this places it 30km away from the comet, this image provided a lot of visual detail.

9. Skylab

As NASA's first ever space station, Skylab was instrumental in developing the technology and infrastructure utilized in current manned space missions. After a reasonably long operational life of almost 6 years, the spaceship re-entered the atmosphere and broke up over Western Australia.

Due to some debris falling on parts of Western Australia, this resulted in NASA being fined $400 (Australian dollars) for littering. This was never paid by NASA.

Skylab LaunchCredit: NASA

10. Pluto Kuiper Express

This mission was designed by NASA to closely pass Pluto and map its surface, among other scientific objectives. Although cancelled, the mission objectives will soon be completed by the New Horizons spacecraft, which will reach Pluto in July 2015.

Many NASA missions have been cancelled for budgetary reasons. After the successful moon missions in the early 70s, the US government decreased science spending across the board. The future depends on continued scientific development, and this requires more confident funding from the government.