Gyaan - Tracking a plane, Quasars, Shompen tribe, Li-Fi, STAP, Organic Farming, SRI

How do you track a plane?

Air traffic control - standard international practice is to monitor airspace using two radar systems: primary and secondary.

Primary radar -based on the earliest form of radar developed in the 1930s, detects and measures the approximate position of aircraft using reflected radio signals. It does this whether or not the subject wants to be tracked. Secondary radar, which relies on targets being equipped with a transponder, also requests additional information from the aircraft - such as its identity and altitude.

All commercial aircraft are equipped with transponders (an abbreviation of "transmitter responder"), which automatically transmit a unique four-digit code when they receive a radio signal sent by radar.

The code gives the plane's identity and radar stations go on to establish speed and direction by monitoring successive transmissions. This flight data is then relayed to air traffic controllers.

However, once an aircraft is more than 240km (150 miles) out to sea, radar coverage fades and air crew keep in touch with air traffic control and other aircraft using high-frequency radio.

Can't planes be tracked with GPS?
Yes, but while GPS (Global Positioning System) is a staple of modern life, the world's air traffic control network is still almost entirely radar-based.

Aircraft use GPS to show pilots their position on a map, but this data is not usually shared with air traffic control.

Some of the most modern aircraft are able to "uplink" GPS data to satellite tracking services, but handling large volumes of flight data is expensive and such systems are usually only used in remote areas with no radar coverage.

The satellite data which suggests flight MH370 flew on for several hours are basic 'pings' sent by the plane, and so far only help to identify two very approximate flight corridors north and south.

Over the next decade, a new system called ADS-B (Automatic Dependent Surveillance Broadcast) is expected to replace radar as the primary surveillance method for air traffic control

ADS-B will see aircraft work out their position using GPS and then relay data to the ground and other planes.

But, as with existing secondary radar, ADS-B coverage does not extend over the oceans.

Could other data systems provide clues?
When Air France flight 447 crashed into the mid Atlantic in 2009, its onboard data system - Aircraft Communications Addressing and Reporting System (ACARS) - gave investigators an early insight into what had gone wrong.

ACARS is a service that allows computers aboard the plane to "talk" to computers on the ground, relaying in-flight information about the health of its systems.

Messages are transmitted either by radio or digital signals via satellites, and can cover anything from the status of the plane's engines to a faulty toilet.

This provides ground crews with vital diagnostic information, allowing maintenance to be carried out more quickly.

In the Air France case, ACARS highlighted faulty speed readings, which caused the air crew to become disorientated.

The final message from the ACARS onboard the Malaysian plane came at 01:07 and investigators believe the system was then deliberately shut down.

Turning off ACARS is no easy feat, requiring a person with technical knowledge to climb down through a trapdoor into the plane's hull to remove circuit breakers.

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Related Gyaan

What is the difference between Radar and Sonar?

• The radar uses radio waves for detection, while sonar uses sound waves (or acoustic) for detection.

• Radar usually is used in the atmosphere, while sonar is usually used underwater. However, these are not strict conditions.

• Radar has a greater range than the sonar (preferably in air).

• Radar has faster response (radio waves travel at the speed of light), while sonar is slower in response (speed of sound is low, and it depends on the properties of the medium, such as temperature, pressure and if its sea water, its salinity).

Quasars

Quasars are extremely distant objects in our known universe. They are the furthest objects away from our galaxy that can be seen. Quasars are extremely bright masses of energy and light. The name quasar is actually short for quasi-stellar radio source or quasi-stellar object.

Quasars are the brightest objects in our universe, although to see one through a telescope they do not look that bright at all. This is because quasars are so far away. They emit radio waves, x-rays and light waves. Quasars appear as faint red stars to us here on Earth.

A quasar is believed to be a supermassive black hole surrounded by an accretion disk. An accretion disk is a flat, disk-like structure of gas that rapidly spirals around a larger object, like a black hole, a new star, a white dwarf, etc. A quasar gradually attracts this gas and sometimes other stars or or even small galaxies with their superstrong gravity. These objects get sucked into the black hole. When a galaxy, star or gas is absorbed into a quasar in such a way, the result is a massive collision of matter that causes a gigantic explosive output of radiation energy and light. This great burst of energy results in a flare, which is a distinct characteristic of quasars.

The light, radiation and radio waves from these galaxies and stars being absorbed into a black hole travel billions of light years through space. When we look at quasars which are 10-15 billion light years away, we are looking 10-15 billion years into the past.

Shompen Tribe

Shompens, considered one of the last surviving stone-age tribes and living in Great Nicobar.

The Shompens are one of the six tribes that inhabit the forest in the southern-most tip of the country. They are classified as primitive tribal group along with the four other tribes  - Jarawa, Andamanese, Onge and the Sentinelese. 

The Shompen's are not as well known as the Jarawas of the Andaman islands. While the Jarwas are a negrito tribe, the Shompens are of Mongoloid stock. Like the Jarawa they are skilled hunter-gatherers but unlike them raise plantations of various crops and subsist primarily on them, besides honey and fish.

Why in News? : LOK SABHA POLLS: SHOMPENS TRIBE VOTES FOR FIRST TIME IN ANDAMAN

Li-Fi Technology

Li-Fi, or "light fidelity", is a technology, that can be a complement of RF communication (Wi-Fi or Cellular network), or a replacement in contexts of data broadcasting. Li-Fi, like Wi-Fi, is the high speed, bidirectional and fully networked subset of visible light communications (VLC). It is wireless and uses visible light communication (instead radio frequency waves), which carries much more information, and has been proposed as a solution to the RF-bandwidth limitations.

It is 5G visible light communication systems using light from light-emitting diodes (LEDs) as a medium to deliver networked, mobile, high-speed communication in a similar manner as Wi-Fi. Li-Fi could lead to the Internet of Things, which is everything electronic being connected to the internet, with the LED lights on the electronics being used as internet access points. The Li-Fi market is projected to have a compound annual growth rate of 82% from 2013 to 2018 and to be worth over $6 billion per year by 2018

Stimulus-triggered acquisition of pluripotency cell (STAP)

Stimulus-triggered acquisition of pluripotency (also known as STAP) is a possible phenomenon capable of generating pluripotent stem cells by subjecting ordinary cells to certain types of stress, such as the application of a bacterial toxin, submersion in a weak acid, or physical squeezing. The technique gained prominence in January 2014 when research by Haruko Obokata was published in Nature. Over the following months, most scientists who tried to duplicate her results failed and suspicion arose that Obokata's results were due to error or fraud. An investigation by her employer, RIKEN, was launched. On 1 April 2014, RIKEN concluded that Obokata had falsified data to obtain her results.

If proven valid, STAP would be a radically simpler method of stem cell generation than previously researched methods as it requires neither nuclear transfer nor the introduction of transcription factors.

Organic Farming

Organic farming is a farming system with minimal or no use of chemicals as fertilizers, herbicides, pesticides etc and with a maximum input of organic manures, recycled farm-wastes, use of bio-agents such as culture of blue green algae in preparation of biofertilizers, neem leaves or turmeric specifically in grain storage as bio-pesticides, with healthy cropping systems [mixed cropping, inter-cropping and crop rotation.]

It is useful over fertilizers and pesticides by following :
Lower Growing Cost: The economics of organic farming is characterized by increasing profits via reduced water use, lower expenditure on fertilizer and energy, and increased retention of topsoil. To add to this the increased demand for organic produce makes organic farming a profitable option for farmers.

Enhances Soil Nourishment: Organic farming effectively addresses soil management. Even damaged soil, subject to erosion and salinity, are able to feed on micro-nutrients via crop rotation, inter-cropping techniques and the extensive use of green manure. The absence of chemicals in organic farming does not kill microbes which increase nourishment of the soil.

Resistance to Disease and Pest: Farming the organic way enables farmers to get rid of irksome weeds without the use of any mechanical and chemical applications. Practices such as hand-weeding and soil enhancement with mulch, corn gluten meal, garlic and clove oil, table salt and borax not only get rid of weeds and insects, but also guarantee crop quality.

Increased Drought Tolerance: Organically grown plants are more drought tolerant. The soluble salts in cells of fertilizers-fed plants are unable to osmotically draw sufficient water to maintain safe dilution, thereby increasing the salt content. This salt level reaches toxic levels and result in the death of plants.

Environment-friendly Practices: The use of green pesticides such as neem, compost tea and spinosad is environment-friendly and non-toxic. These pesticides help in identifying and removing diseased and dying plants in time and subsequently, increasing crop defense systems.

System of rice intensification 

The system of rice intensification, known as SRI is an agro-ecological methodology for increasing the productivity of irrigated rice by changing the management of plants, soil, water and nutrients. SRI originated in Madagascar in the 1980s 

SRI Principles
SRI methodology is based on four main principles that interact with each other:

1. Early, quick and healthy plant establishment
2. Reduced plant density
3. Improved soil conditions through enrichment with organic matter
4. Reduced and controlled water application 

Based on these principles, farmers can adapt recommended SRI practices to respond to their agroecological and socioeconomic conditions. Adaptations are often undertaken to accommodate changing weather patterns, soil conditions, labor availability, water control, access to organic inputs, and the decision whether to practice fully organic agriculture or not.

In addition to irrigated rice, the SRI principles have been applied to rainfed rice and to other crops, such as wheat, sugarcane, teff, finger millet, pulses, showing increased productivity over current conventional planting practices. When SRI principles are applied to other crops, we refer to it as the System of Crop Intensification or SCI
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