1) Ground based telescopes are used most widely. The main reason for this is their cost. Relatively cheap, they allow observing a large part of the sky. Their scientific impact is estimated at 60-70% of all the information obtained and referred from 1991 to 1998[4]. Currently, numerous huge telescopes are based in different parts of the world and supply information for scientific researches. However, there are several major problems connected with the ground-based telescopes. First of all, the atmosphere is very thick, for this reason the stars can’t be clearly seen. Atmosphere also creates deflections in images. Only 1% of the sky is observed by ground-based telescopes [5]. Another problem is the data gathered and stored by ground-based telescopes. It should be constantly calibrated for the reason of changing equipment, while geosyncronous orbiting telescopes are much more technically stable (the equipment is not changed every now and then).
Geosyncronous orbiting telescopes differ from the ground-based telescope, as they are situated in the zone of the equator, high over the atmosphere. With the help of this type of telescopes the major problem of obtaining objective, detailed data and images from the bodies around Earth such as stars. The importance of geosyncronous orbiting telescopes lies in their ability to see the needed object directly and not through the whole atmosphere. This ability enlarges their efficiency and accuracy. Second, as it was mentioned the science impact of geosyncronous orbiting telescopes is measured as 30-40% of all data referred, while ground based telescopes outnumber them greatly. They are 15-20 times more efficient then the ground based ones [6]. While ground based telescopes contribute a lot to the exploration of the space, they are still much less efficient them the geosyncronous orbiting ones. Their main disadvantage is their high cost of production. Narrow scientific problem require geosyncronous orbiting telescopes, because detailed tasks cannot be managed by the ground-based telescopes.
2) Manned space missions function as the programs that exist to maintain the process of launching humans into space. One of the most well-known representatives of such missions is the International Space Station.
The International Space Station (ISS) is a space station situated 354, 06 kilometers above the Earth’s orbit. It is the operational project of 6 main space-countries: the U.S.A., Japan, Canada, Brazil, Russia and the European space agency including several countries headed by the U.K. The station is controlled by man and it is the merging point between space shuttles and Earth. The standard quantity of the station’s crew is three. This manned space mission is of a particular interest for the world as it represents the active space program. It actively uses shuttles for the space exploration missions. It is primarily serviced by the major international shuttles and is a base for them.
The Space Shuttle program is directly associated with the mentioned above International Space Station. Space Shuttle also known as the Space Transportation System is a space program controlled by NASA. It is the orbital spacecraft that provides crew rotation for the International Space Station. It carries out the missions offered by the ISS along with Soyuz and Progress(Wiley,1999). The Space Shuttle program includes the following individual orbiters that complete different missions: Enterprise (OV-101), Columbia (OV-102), Challenger (OV-99), Discovery (OV-103), Atlantis (OV-104), and Endeavour (OV-105).The major disadvantage of these manned space missions is the probability of death risks for astronauts especially seen in the tragedies of Colombia and Challenger, when the whole crew died[Berg,76].
3) A lot of space missions nowadays are subjects to the remote-controlled spacecrafts. Such missions do not have a pilot and are controlled by computers. One of the most popular unmanned missions is the Giotto mission, whose priority was to explore the Halley’s Comet [Mirabito, 112]. Nevertheless the term unmanned missions is strongly connected to the term space probes which are intended to explore other planets.
The probes are accomplished out of the borders of the Earth’s orbit as they get as close as they can to the comets, asteroids, planets or any other object they are studying. The probes have been already sent to investigate the Moon, Mars and to make general solar system probes which include the exploration of all the other planets in the system. The probes are ordinary separated into different programs such as Luna program, Mars probe program or Cassini-Huygens probe program. The A-Train program, NASA’s Earth-Sun System Missions, Explorer program, Helios program, ISIS program, Pioneer program and many others also represent the unmanned missions of the highest priority [Matloff, 65].
Unmanned missions also include artificial satellites but they function and work only within the Earth’s orbit. They are used to explore the planet’s surface and atmosphere for any occurring changes.
Probe programs make the work of the contemporary space exploration mush easier providing new opportunities and information for the space-scientists. Most of the probes are conducted by two space centers: by the U.S. Jet Propulsion Laboratory and the European Space Agency [Wolverton, 98]. Probe missions are a good choice because the human death risk is eliminated completely.

Bibliography:

1. Mirabito, Michael M. “The exploration of outer space with cameras: a history of the NASA unmanned spacecraft missions”/ Mcfarland & Co Inc Pub/ 1983.
2. Matloff, Gregory L. “Deep Space Probes: To the Outer Solar System and Beyond”/ Springer/ 2005.

3. Wolverton, Mark “The depths of space: the story of the pioneer planetary probes”/ Joseph Henry Press/ 2004.
4. “Gemini’s Report on MAXAT - the Maximum Aperture Telescope” Hole, W. Madison / October 19, 2005.
<http://www.gemini.edu/science/maxat/>
5. NASA.”Deep Impact”/October 20, 2005. <http://deepimpact.jpl.nasa.gov/science/observations.html>
6. ”Scientific Impact of Large Telescopes”/ Benn, C. SanchezS./October 20,2005.
<http://www.ing.iac.es/PR/newsletter/news4/science2.html>
7. Wiley J. Larson & James R. Wetrz “Space Mission Analysis and Design”/ Microcosm Press/1999.
8. Berg, Van Den “Guide to manned space missions”/Gemini Productions/1988.