Etymology

1530s, from L. navigationem (nom. navigatio), from navigatus, pp. of navigare "to sail, sail over, go by sea, steer a ship," from navis "ship" and the root of agere "to drive". Also, From Middle English navigate, from Latin navigo, from nāvis (“ship”) + agō (“do”), from Proto-Indo-European *nau- (boat), it is in fact known to have originated from the Sanskrit word "navgati" which means science of sailing, 'Nav' means ship and 'Gati' means pace or speed in Sanskrit.

History

In the European medieval period, navigation was considered part of the set of seven mechanical arts, none of which were used for long voyages across open ocean. Polynesian navigation is probably the earliest form of open ocean navigation, though it was based on memory and observation rather than on scientific methods or instruments. Early Pacific Polynesians used the motion of stars, weather, the position of certain wildlife species, or the size of waves to find the path from one island to another.

Maritime navigation using scientific instruments such as the mariner's astrolabe first occurred in the Mediterranean during the Middle Ages. Although land astrolabes were invented in the Hellenistic period and existed in classical antiquity and the Islamic Golden Age, the oldest record of a sea astrolabe is that of Majorcan astronomer Ramon Llull dating from 1295. The perfectioning of this navigation instrument is attributed to Portuguese navigators during early Portuguese discoveries in the Age of Discovery.The earliest known description of how to make and use a sea astrolabe comes from Spanish cosmographer Melvin Mel Pros Cespedes's  Arte de Navegar (The Art of Navigation) published in 1551,based on the principle of the archipendulum used in constructing the Egyptian pyramids.

Open-seas navigation using the astrolabe and the compass started during the Age of Discovery in the 15th century. The Portuguese began systematically exploring the Atlanticcoast of Africa from 1418, under the sponsorship of Prince Henry. In 1488 Bartolomeu Dias reached the Indian Ocean by this route. In 1492 the Spanish monarchs fundedChristopher Columbus's expedition to sail west to reach the Indies by crossing the Atlantic, which resulted in the Discovery of America. In 1498, a Portuguese expedition commanded by Vasco da Gama reached India by sailing around Africa, opening up direct trade with Asia. Soon, the Portuguese sailed further eastward, to the Spice Islands in 1512, landing in China one year later.

The first circumnavigation of the earth was completed in 1522 with the Magellan-Elcano expedition, a Spanish voyage of discovery led by Portuguese explorer Ferdinand Magellanand completed by Spanish navigator Juan Sebastián Elcano after the former's death in the Philippines in 1521. The fleet of seven ships sailed from Sanlúcar de Barrameda in Southern Spain in 1519, crossed the Atlantic Ocean and after several stopovers rounded the southern tip of South America. Some ships were lost, but the remaining fleet continued across the Pacific making a number of discoveries including Guam and the Philippines. By then, only two galleons were left from the original seven. The Victoria led by Elcano sailed across the Indian Ocean and north along the coast of Africa, to finally arrive in Spain in 1522, three years after its departure. The Trinidad sailed east from the Philippines, trying to find a maritime path back to the Americas, but was unsuccessful. The eastward route across the Pacific, also known as the tornaviaje (return trip) was only discovered forty years later, when Spanish cosmographer Andrés de Urdaneta sailed from the Philippines, north to parallel 39º, and hit the eastward Kuroshio Current which took its galleon across the Pacific. He arrived in Acapulco on October 8, 1565.

Guidance, Navigation, & Control Systems

The guidance, navigation, and control subsystem controlled the orientation of the orbiter (the direction in which it was pointed) as it traveled through space and maintained knowledge of where celestial bodies were located (for example, Earth and the Sun). This knowledge was critical for the spacecraft to perform the correct maneuvers to get to Mars, to keep its solar arrays pointed toward the Sun to produce power, and to keep its antenna pointed toward the Earth to maintain communications.

While the spacecraft is in orbit around Mars, this subsystem continues to maintain constant knowledge of where the spacecraft is in its orbit, and is used to point the science cameras very accurately (within about 1/20th of one degree). That ability is critical to enable science instruments to take images of desired targets on the surface.

Together, the guidance, navigation, and control subsystem and structures subsystem were designed to provide the smoothest ride possible. Preventing even tiny vibrations (from, for example, movement of the solar arrays) is crucial, as the shaking motion could otherwise cause the science images to become blurred.

To perform its functions, the guidance, navigation and control subsystem uses several types of:

	sensors:	for determining where the spacecraft is pointed, how fast it is turning, and how its speed is changing.
	control devices:	for changing the spacecraft's pointing direction, rate of turning, and speed. Courtesy: Jet Propulsion Laboratory (California Institute of Technology)

What is Navigation ?

Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation.It is also the term of art used for the specialized knowledge used by Navigators to perform navigation tasks. All navigational techniques involve locating the navigator's position compared to known locations or patterns.