Sarh

Sarh, formerly French colonial Fort Archambault, is the capital of Moyen-Chari Region and of the Department of Barh Köh, in Chad, Central Africa.

Geography

Sarh is located on the Chari River, 350 miles (560 km) southeast of the capital city N'Djamena. It was named after the Sara people of southern Chad.

It is the third largest city in Chad, after N'Djamena and Moundou

History

Fort Archambault (Sarh) was founded by the colonial French Equatorial Africa, for returnees from the labour camps associated with the construction of the Congo-Ocean Railway. A significantly large textiles complex was constructed by the French in Sarh in 1967.

The residents of Sarh suffered a meningococcal meningitis epidemic in 1990.

Economy

Sarh is now a major transport hub. It is served by the Sarh Airport (IATA airport code SRH).

It is a center for the cotton industry, due to its warm and seasonally wet climate. It is also an important center for commercial fishing in the Chari River.

The city is known as a center of nightlife in the region. Attractions in the city include the Sarh National Museum.

List of craters on Mars: O-Z

This is a list of craters on Mars. There are hundreds of thousands of impact crater on Mars, but only some of them have names. This list here contains only named Martian craters starting with the letter O – Z (see also lists for A – G and H – N).

Large Martian craters (greater than 60 km in diameter) are named after famous scientists and science fiction authors; smaller ones (less than 60 km in diameter) get their names from towns on Earth. Craters cannot be named for living people, and small crater names are not intended to be commemorative - that is, a small crater isn't actually named after a specific town on Earth, but rather its name comes at random from a pool of terrestrial place names, with some exceptions made for craters near landing sites. Latitude and longitude are given as planetographic coordinates with west longitude.

O

P

Q

R

S

T

U

V

W

X

Y

Z

See also

References

Semi-active radar homing

Semi-active radar homing (SARH) is a common type of missile guidance system, perhaps the most common type for longer-range air-to-air and surface-to-air missile systems. The name refers to the fact that the missile itself is only a passive detector of a radar signal – provided by an external (“offboard”) source — as it reflects off the target(in contrast to active radar homing, which uses an active radar: transceiver). Semi-active missile systems use bistatic continuous-wave radar.

The NATO brevity code for a semi-active radar homing missile launch is Fox One.

Concept

The basic concept of SARH is that since almost all detection and tracking systems consist of a radar system, duplicating this hardware on the missile itself is redundant. The weight of a transmitter reduces the range of any flying object, so passive systems have greater reach. In addition, the resolution of a radar is strongly related to the physical size of the antenna, and in the small nose cone of a missile there isn't enough room to provide the sort of accuracy needed for guidance. Instead the larger radar dish on the ground or launch aircraft will provide the needed signal and tracking logic, and the missile simply has to listen to the signal reflected from the target and point itself in the right direction. Additionally, the missile will listen rearward to the launch platform's transmitted signal as a reference, enabling it to avoid some kinds of radar jamming distractions offered by the target.