Moon

The Moon (in Greek: σελήνη Selene, in Latin: Luna) is Earth's only natural satellite. It is one of the largest natural satellites in the Solar System, and, among planetary satellites, the largest relative to the size of the planet it orbits (its primary). It is the second-densest satellite among those whose densities are known (after Jupiter's satellite Io).

The Moon is thought to have formed approximately 4.5 billion years ago, not long after Earth. There are several hypotheses for its origin; the most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia.

The Moon is in synchronous rotation with Earth, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters. It is the second-brightest regularly visible celestial object in Earth's sky after the Sun, as measured by illuminance on Earth's surface. Although it can appear a very bright white, its surface is actually dark, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence on language, calendars, art, and mythology.

Geostationary orbit

A geostationary orbit, geostationary Earth orbit or geosynchronous equatorial orbit (GEO) is a circular orbit 35,786 kilometres (22,236 mi) above the Earth's equator and following the direction of the Earth's rotation. An object in such an orbit has an orbital period equal to the Earth's rotational period (one sidereal day), and thus appears motionless, at a fixed position in the sky, to ground observers. Communications satellites and weather satellites are often placed in geostationary orbits, so that the satellite antennas (located on earth) which communicate with them do not have to rotate to track them, but can be pointed permanently at the position in the sky where the satellites are located. Using this characteristic, ocean color satellites with visible and near-infrared light sensors (e.g. the Geostationary Ocean Color Imager (GOCI)) can also be operated in geostationary orbit in order to monitor sensitive changes of ocean environments.

A geostationary orbit is a particular type of geosynchronous orbit, the distinction being that while an object in geosynchronous orbit returns to the same point in the sky at the same time each day, an object in geostationary orbit never leaves that position.

Launch vehicle

In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad, and other infrastructure. Although a carrier rocket's payload is often an artificial satellite placed into orbit, some spaceflights, such as sounding rockets, are sub-orbital, while others enable spacecraft to escape Earth orbit entirely.

Earth orbital launch vehicles typically have at least two stages, and sometimes as many as four or more.

Types

Expendable launch vehicles are designed for one-time use. They usually separate from their payload and disintegrate during atmospheric reentry. In contrast, reusable launch vehicles are designed to be recovered intact and launched again. The Space Shuttle was the only launch vehicle with components used for multiple orbital spaceflights. SpaceX is developing a reusable rocket launching system for their Falcon 9 and Falcon Heavy launch vehicles. A second-generation VTVL design was announced in 2011. The low-altitude flight test program of an experimental technology-demonstrator launch vehicle began in 2012, with more extensive high-altitude over-water flight testing planned to begin in mid-2013, and continue on each subsequent Falcon 9 flight.Non-rocket spacelaunch alternatives are at the planning stage, although it is known that some companies are developing actual launch platforms, such as the Spanish zero2infinity with their rockoon-based launcher "bloostar".

Satellite Launch Vehicle

The Satellite Launch Vehicle (Hindi: उपग्रह प्रक्षेपण यान), or SLV was a project started in the early 1970s by the Indian Space Research Organisation to develop the technology needed to launch satellites. The project was headed by APJ Abdul Kalam. SLV was intended to reach a height of 400 km and carry a payload of 40 kg.The first experimental flight of SLV-3, in August 1979, was only partially successful.

It was a four-stage rocket with all solid-propellant motors.

The first launch of the SLV took place in Sriharikota on 10 August 1979. The fourth and final launch of the SLV took place on 17 April 1983.

Launch History

All four SLV launches occurred from the SLV Launch Pad at the Sriharikota High Altitude Range.

See also

References

Geosynchronous Satellite Launch Vehicle

GeoSynchronous Satellite Launch Vehicle (Hindi: भूस्थिर उपग्रह प्रक्षेपण यान), abbreviated in English as GSLV, is an expendable launch system operated by the Indian Space Research Organisation (ISRO). It was developed to enable India to launch its satellites without dependence on foreign rockets and providers. GSLV has been used in nine launches to date, since its first launch in 2001 through to its most recent launch on August 27, 2015 of the GSAT-6.

History

The Geosynchronous Satellite Launch Vehicle (GSLV) project was initiated in 1990 with the objective of acquiring an Indian government launch capability for geosynchronous satellites. India has depended on the United States and Europe for the launch of INSAT class of satellites.

GSLV uses major components that are already proven in the Polar Satellite Launch Vehicle (PSLV) launchers in the form of the S125/S139 solid rocket booster and the liquid-fueled Vikas engine. The third stage was procured from Russian company Glavcosmos based on an agreement signed in 1991. Russia backed out of the deal after US sanctions were imposed in May 1992. ISRO started the Cryogenic Upper Stage Project in April 1994 and began developing its own cryogenic stage. Russia agreed to sell 7 cryogenic stages and 1 ground mock-up stage instead of 5 cryogenic stages and the technology to build the stages.