NASA
The National Aeronautics and Space Administration (NASA), which was established in 1958, is the agency responsible for the public space program of the United States of America. It is also responsible for long-term civilian and military aerospace research.

Vision and mission

NASA's vision is "to improve life here, extend life to there, and to find life beyond". Its mission is "to understand and protect our home planet; to explore the Universe and search for life; and to inspire the next generation of explorers".

History

Space Race

May 5, 1961 launch of Redstone
rocket and NASA's Mercury 3
capsule Freedom 7 with Alan
Shepard Jr. on the United States'
first human flight into sub-orbital
space. (Atlas rockets were used
to launch Mercury's orbital missions.)

Following the Soviet space program's launch of the world's first man-made satellite (Sputnik1)on October 4, 1957, the attention of the United States turned toward its own fledgling space efforts. The U.S. Congress, alarmed by the perceived threat to U.S. security and technological leadership (known as "Sputnik Shock"), urged immediate and swift action; President Dwight D. Eisenhower and his advisers counseled more deliberate measures. Several months of debate produced agreement that a new federal agency was needed to conduct all nonmilitary activity in space.

On July 29, 1958, President Eisenhower signed the National Aeronautics and Space Act establishing the National Aeronautics and Space Administration (NASA). When it began operations on October 1, 1958, NASA consisted mainly of the four laboratories and some 8,000 employees of the government's 46-year-old researc

h agency for aeronautics, the National Advisory Committee for Aeronautics (NACA), though the probably most important contribution actually had its roots in the German rocket program led by Wernher von Braun, who is today regarded as the father of the United States space program. Elements of the Army Ballistic Missile Agency (of which von Braun's team was a part) and the Naval Research Laboratory were incorporated into NASA.

NASA's early programs were research into human spaceflight, and were conducted under the pressure of the competition between the USA and the USSR (the Space Race) that existed during the Cold War. The Mercury program, initiated in 1958, started NASA down the path of human space exploration with missions designed to discover simply if man could survive in space. Representatives from the U.S. Army (M.L. Raines, LTC, USA), Navy (P.L. Havenstein, CDR, USN) and Air Force (K.G. Lindell, COL, USAF) were selected/requested to provide assistance to the NASA Space Task Group through coordination

with the existing U.S. military research and defense contracting infrastructure, and technical assistance resulting from experimental aircraft (and the associated military test pilot pool) development in the 1950s. On May 5, 1961, astronaut Alan B. Shepard Jr. became the first American in space when he piloted Freedom 7 on a 15-minute suborbital flight. John Glenn became the first American to orbit the Earth on February 20, 1962 during the 5-hour flight of Friendship 7.

Once the Mercury project proved that human spaceflight was possible, project Gemini was launched to conduct experiments and work out issues relating to a moon mission. The first Gemini flight with astronauts on board, Gemini III, was flown by Virgil "Gus" Grissom and John W. Young on March 23, 1965. Nine other missions followed, showing that long-duration human space flight was possible, proving that rendezvous and docking with another vehicle in space was possible, and gathering medical data on the effects of weightlessness on humans.

Apollo program

Buzz Aldrin walks on the surface of the Moon during Apollo 11

Apollo program

Following the success of the Mercury and Gemini programs, the Apollo program was launched to try to do interesting work in space and possibly put men around (but not on) the Moon. The direction of the Apollo program was radically altered following President John F. Kennedy's announcement on May 25, 1961 that the United States should commit itself to "landing a man on the Moon and returning him safely to the "Earth by 1970. Thus Apollo became a program to land men on the Moon. The Gemi

ni program was started shortly thereafter to provide an interim spacecraft to prove techniques needed for the now much more complicated Apollo missions.

After eight years of preliminary missions, including NASA's first loss of astronauts with the Apollo 1 launch pad fire, and the first spacecraft to orbit the Moon ( Apollo 8) at the end of 1968, the Apollo program achieved its goals with Apollo 11 which landed Neil Armstrong and Buzz Aldrin on the moon's surface on July 20, 1969 and returned them to Earth safely on July 24. Armstrong's first words upon stepping out of the Eagle lander captured the momentousness of the occasion: "That's one small step for [a] man, one giant leap for mankind". Twelve men would set foot on the Moon by the end of the Apollo program in December 1972.

NASA had won the moon race, and in some senses this left it without direction, or at the very least without the public attention and interest that was necessary to guarantee large budgets from Congress. After President Lyndon Johnson left office, NASA lost its main political supporter, and rocket scientist Wernher von Br

aun was moved to a position lobbying in Washington. Plans for ambitious follow-on projects to construct a space station, establish a lunar base and launch a human mission to Mars by 1990 were proposed but with the end to procurement of Saturn and Apollo hardware, there was no capability to support these. The near-disaster of Apollo 13, where an oxygen tank explosion nearly doomed all three astronauts, helped to recapture national attention and concern. Although missions up to Apollo 20 were planned, Apollo 17 was the last mission to fly men to the moon. The program ended because of budget cuts (in part due to the Vietnam War) and the desire to develop a reusable space vehicle.

Other early missions

Although the vast majority of NASA's budget has been spent on human spaceflight, there have been many robotic missions instigated by the space agency. In 1962 the Mariner 2 mission was launched and became the first spacecraft to make a flyby of another planet – in this case Venus. The Ranger, Surveyor, and Lunar Orbiter missions were essential to assessing lunar conditions before attempting Apollo landings with humans on board. Later, the two Viking probes landed on the surface of Mars and sent colour images back to Earth, but perhaps more impressive were the Pioneer and particularly Voyager missions that visited Jupiter, Saturn, Uranus and Neptune sending back scientific information and colour images.

Having lost the moon race, the Soviet Union had, along with the USA, changed its approach. On July 17, 1975 an Apollo craft (finding a new use after the cancelling of planned lunar flights) was docked to the Soviet Soyuz 19 spacecraft, in the Apollo-Soyuz Test Project. Although the Cold War would last many more years, this was a critical point in NASA's history and much of the international co-operation in space exploration that exists today has its genesis with this mission. America's first space station, Skylab, occupied NASA from the end of Apollo until the late 1970s.

Shuttle era

The space shuttle became the major focus of NASA in the late 1970s and the 1980s. Planned to be a frequently launchab

le and mostly reusable vehicle, four space shuttles were built by 1985. The first to launch, Columbia did so on April 12, 1981.

The shuttle was not all good news for NASA — flights were much more expensive than initially projected, and even after the 1986 Challenger disaster highlighted the risks of space flight, the public again lost interest as missions appeared to become mundane. Work began on Space Station Freedom as a focus for the manned space programme but within NASA there was argument that these projects came at the expense of more inspiring unmanned missions such as the Voyager probes. The Challenger disaster aside the late 1980s marked a low point for NASA.

Nonetheless, the shuttle has been used to launch milestone projects like the Hubble Space Telescope (HST). The HST was created with a relatively small budget of $2 billion but has continued operation since 1990 an

d has delighted both scientists and the public. Some of the images it has returned have become near-legendary, such as the groundbreaking Hubble Deep Field images. The HST is a joint project between ESA and NASA, and its success has paved the way for greater collaboration between the agencies.

In 1995 Russian-American interaction would again be achieved as the Shuttle-Mir missions began, and once more a Russian craft (this time a full-fledged space station) docked with an American vehicle. This cooperation continues to the present day, with Russia and America the two biggest partners in the largest space station ever built – the International Space Station (ISS). The strength of their cooperation on this project was even more evident when NASA began relying on Russian launch vehicles to service the ISS following the 2003 Columbia disaster, which grounded the shuttle fleet for well over two years.

Costing over one hundred billion dollars, it has been difficult at times for NASA to justify the ISS. The population at large have historically been hard to impress with details of scientific experiments in space, preferring news of grand projects to exotic locations. Even now, the ISS cannot accommodate as many scientists as planned.

During much of the 1990s, NASA was faced with shrinking annual budgets due to Congressional belt-tightening in Washington, DC. In response, NASA's ninth administrator, Daniel S. Goldin, pioneered the "faster, better, cheaper" approach that enabled NASA to cut costs while still delivering a wide variety of aerospace programs ( Discovery Program). That method was criticized and re-evaluated following the twin losses of Mars Climate Orbiter and Mars Polar Lander in 1999.

NASA's shuttle program has made over 112 successful launches.

Cloud

Cumulus of fair weather
A cloud is a visible mass of condensed droplets or ice crystals suspended in the atmosphere above the surface of the Earth or another planetary body. The branch of meteorology that studies clouds is nephology.

On Earth, the condensing substance is water vapor, which forms small droplets of water (typically 0.01 mm of ice crystals) that, when surrounded with billions of other droplets or crystals, are visible as clouds. Clouds reflect all visible wavelengths of light equally and are usually white, but they can appear grey or even black if they are so thick or dense that sunlight cannot pass through.

Cloud formation and properties

A variety of cloud formations









Global scheme of cloud optical thickness







Clouds form when the invisible water vapor in the air condenses into visible water droplets or ice crystals. This can happen in three ways.

1. The air is cooled below its saturation point.

This happens when th

e air comes in contact with a cold surface or a surface that is cooling b

y radiation, or the air is cooled by adiabatic expansion (rising). This can happen

• along warm and cold fronts ( frontal lift),
• where air flows up the side of a mountain and cools as it rises higher into the atmosphere ( orographic lift),
• by the convection caused by the warming of a surf ace by insolation (diurnal heating),
• when warm air blows over a colder surface such as a cool body of water.

2. Clouds can be formed when two air masses below saturation point mix. Examples are breath on a cold day, aircraft contrails, and Arctic sea smoke.

3. The air stays the same temperature but absorbs more water vap

or into it until it reaches saturation.

The water in a typical cloud can have a mass of up to several million tonnes. However, the volume of a cloud is correspondingly high, and the net density of water vapor is actually low enough that air currents below and within the cloud are capable of keeping small droplets suspended. As well, conditions inside a cloud are not static: water droplets are constantly forming and re-evaporating. A typical cloud droplet has a radius on the order of 1 x 10^-5 m and a terminal velocity of about 1-2 cm/s. This give these droplets plenty of time to re-evaporate as they fall into in the warmer air beneath the cloud.

Most water droplets are formed when water vapor condenses

around a condensation nucleus, a tiny particle of smoke, dust, ash, or salt. In supersaturated conditions, water droplets may act as condensatio

n nuclei.

Water droplets large enough to fall to the ground are produced in two ways. The most important is through the Bergeron Process, theorized by Tor Bergeron, in which supercooled water drop

lets and ice crystals in a cloud interact to produce the rapid growth of ice crystals, which precipitate from the cloud and melt as they fall. This process typically takes place in clouds with tops cooler than -15°C. The second most import

ant process is the collision and wake capture process, oc

curring in clouds with warmer tops, in which the collision of rising and falling water droplets produces larger and larger droplets, which are eventually heavy enough to overcome air currents in the cloud and the updraft beneath it and fall as rain. As a droplet falls through the smaller droplets which surround it, it produces a "wake" which draws some of the smaller droplets into collisions, thus perpetuating the process. This method of raindrop production is the primary mechanism in low stratiform clouds and small cumulus clouds in trade winds and tropical regions, and produces raindrops of several millimeters diameter.

The actual form of cloud created depends on the strength of the uplift and on air stability. In unstable conditions convection dominates, creating ve

rtically developed clouds. Stable air produces

horizontally homogeneous clouds. Frontal uplift creates various cloud forms depending on the composition of the front ( ana-type or kata-type warm or cold front). Orographic uplift als

o creates variable cloud forms depending on air stability, although cap cloud and wave clouds are

specific to orographic clouds.

"Hot Ice" and "Ice Memory" in cloud form

ation

This wave cloud pattern formed off of the Île Amsterdam in the far southern Indian Ocean



Perh aps s omew hat confusingly, in addition to being the colloquial term sometimes used to describe dry ice, hot ice is the name given to a surprising ph enomenon in which water can be turned into ice at room temperature by supplying an electric field of the order of 1 million volts per meter. ( Choi 2005). The effect of such electric fields has been suggested as an explanation of cloud formation. Though, this theory is highly controversial and is not, by any means, widely accepted as being th e actual mechanism of cloud formation. The first time cloud ice forms around a clay particle, it requires a temperature of -10°C, but subsequent freezing around the same clay particle requires a temperature of just -5°C, suggesting so me kind of "ice memory" ( Connolly, P.J, et al, 2005)

Cloud classification

Cloud Classification by altitude of occurrence

Clouds are divided into two general cate gories: layered and convective. These are named stratus clouds (or stratiform, the Latin stratus means layer) and cumulus clo uds (or cumuliform, cumulus means piled up). These two cloud types are divided into four more groups that distinguish the cloud's altitude. Clouds are classified by the cloud base height, not the cloud top. This system was proposed by Luke Howard in 1802 in a presentation to the Askesi an Society.

High clouds (Family A)

These generally form above 16,500 feet (5,000 m), in the cold region of th

e troposphere. However, in Polar regions they may form as low as 10,000 ft (3,048 m). They are denoted by the prefix cirro- or cirrus. At this altitude water almost always freezes so clouds are composed of ice crystals. The clouds tend to be wispy, and are often transparent.

Clouds in Family A include:

• Cirrus
  
• Cirrus uncinus
• Cirrus Kelvin-Helmholtz
• Cirrostratus
• Cirrocumulus
• Pileus
• contrail
  

A contrail is a long thin cloud which develops as the result of the passage of an aircraft at high altitudes.

Middle clouds (Family B)
Altocumulus mackerel sky

These develop between 6,500 and 16,500 feet (between 2,000 and 5,000 m) and are denoted by the prefix alto-. They are made of water droplets, and are frequently supercooled.

Clouds in Family B include:

• Altostratus
• Altostratus undulatus
• Altocumulus
• Altocumulus undulatus
• Altocumulus mackerel sky
• Altocumulus castellanus
• Altocumulus lenticularis

Low clouds (Family C)

some low clou ds








These are found up to 6,500 feet (2,000 m) and include the stratus (dense and grey). When stratus clouds contact the ground they are called fog.

Clouds in Family C include:

• Stratus
• Nimbostratus
• Cumulus humilis
• Cumulus med iocris
• Stratocumulus

Vertical clouds (Family D)

Cumulonimbus clouds showing strong updrafts










Thes e clouds can have strong up-currents, rise far a bove their bases and can form at many heights.

Clouds in Family D include:

• Cum ulon imbus (associated with heavy prec ipitation and thunderstorms)
• Cumulonimbus incus
• Cumulonimbus calvus
• Cumul onimbus with mammatus
• Cumulus congestus
• Pyrocumulus

Other clouds

A few clouds can be found above the troposphere; these include noctilucent and polar stratospheric or nacreous clouds which occur in the strat

osphere and mesosphere respectively.

Colors of clouds

An example of various cloud colors

Colourful Cloud formation

Cloud colour tells much about what is going on inside a cloud.

Clouds form when water vapor rises, cools, and condenses out of the air as micro-droplets. These tiny particles of water are relatively dense, and sunlight cannot penetrate far into the cloud before it is reflected out, giving a cloud its characteristic white colour. As a cloud matures, the droplets may combine to produce larger droplets, which may themselves combine to form droplets large enough to fall as rain. In this process of accumulation, the space between droplets becomes larger and larger, permitting light to penetrate much farther into the cloud. If the cloud is sufficiently large, and the droplets within are spaced far enough apart, it may be that very little light which enters the cloud is able to be reflected back out before it is absorbed. (Think of how much farther one can see in a heavy rain as opposed to how far one can see in a heavy fog.) This process of reflection/ absorption is what leads to the range of cloud colour from white through grey through black. For the same reason, the undersides of large clouds and heavy overcasts appear various degrees of grey; little light is being reflected or transmitted back to the observer.

Other colors occur naturally in clouds. Bluish-grey is the result of light scattering within the cloud. In the visible spectrum, blue and green are at the short end of light's visible wavelengths, while red and yellow are at the long end. The short rays are more easily scattered by water droplets, and the long rays are more likely to be absorbed. The bluish colour is evidence that such scattering is being produced by rain-sized droplets in the cloud.

A more ominous colour is the one seen frequently by severe weather observers. A greenish tinge to a cloud is produced when sunlight is scattered by ice. A cumulonimbus cloud which shows green is a pretty sure sign of imminent heavy rain, hail, strong winds, and possibly tornados.

Yellowish clouds are rare, but may occur in the late spring through early fall months during forest fire season. The yellow colour is due to the presence of smoke.

Red, orange, and pink clouds occur almost entirely at sunrise/sunset, and are the result of the scattering of sunlight by the atmosphere itself. The clouds themselves are not that colour, they are merely reflecting the long (and unscattered) rays of sunlight which are predominant at those hours. The effect is much the same as if one were to shine a red spotlight on a white sheet. In combination with large, mature thunderheads, this can produce blood-red clouds. The evening before the Edmonton, Alberta tornado in 1987, Edmontonians observed such clouds - deep black on their dark side, and intense red on their sunward side. In this case, the adage "red sky at night, sailor's delight" was clearly incorrect.

Global dimming

The recently recognized phenomena of global dimming is thought to be caused by changes to the reflectivity of clouds due to the increased presence of aerosols and other particulates in the atmosphere.

Clouds on other planets

Within our solar system, any planet with an atmosphere also has clouds. Venus' clouds are composed entirely of sulfuric acid droplets. Mars has high, thin clouds of water ice. Both Jupiter and have an outer cloud deck composed of ammonia clouds, an intermediate deck of ammonium hydrosulfide clouds, and an inner deck of water clouds.Uranus and Naptune have atmospheres dominated by methane clouds.