Prelims-48: Current Affairs in Science and Technology

July 15, 2017

NAVIC {NAVigation withIndian Constellation} is the new name of IRNSS {Indian Regional Navigation Satellite System}.
It has been designed to provide information over Indian region and an area extending about 1500 sq km around India {which is called its primary service area}.
Further, it will also provide service beyond this region {Extended Service Area} enclosed by a rectangle made by 30°S, 50°N, 30°E and 130°E latitudes and longitudes.
It will provide two types of services viz. Standard Positioning Service {SPS} for all users and also Restricted Service {RS} for only authorized users. RS is an encrypted service.
It is expected to provide position accuracy of better than 20 m in the primary service area.
The key applications include Terrestrial, Aerial and Marine Navigation; Disaster Management; Vehicle tracking and fleet management; Integration with mobile phones; Precise Timing; Mapping and Geodetic data capture; Terrestrial navigation aid for hikers and travellers; Visual and voice navigation for drivers.
There are seven satellites of which three are in GEO whole four are in geosynchronous orbits included at 29°.

NAVIC is a regional navigation system like BeiDou and QZSS and unlike GPS (United States) Galileo (European Union) and GLONASS (Russian Federation), which have global coverage.
Further, UPSC might ask a question comparing two of them, so here is what you should note comparing NAVIC with GPS and BeiDou.

While NAVIC is regional, GPS is global.
While NAVIC has 7 satellites; GPS has total 31 satellites.
Both have almost same resolution for standard / public services (20 meters). However, NASA claims that GPS provides resolution up to 3 meters.
The satellites of NAVIC are in GEO/GSO orbits; while the satellites of GPS are in medium earth orbit.

Both NAVIC and BeiDou are regional navigation systems. However, BeiDou-2 {COMPASS} will be a global satellite navigation system consisting of 35 satellites.

While NAVIC is a project of ISRO, Gagan is a joint project of ISRO and Airports Authority of India Ltd.
GAGAN {Global Positioning System Aided Geo Augmented Navigation System} is for only civil aviation purpose. NAVIC can be used for military purposes also.
GAGAN itself is not a navigation system. Its GPS Aided…., which means that it is dependent on GPS system of America.

To be launched around 2019, Aditya-L1 is India’s first dedicated scientific mission to study Sun. It’s a joint project of ISRO with physicists of various institutes in India including Indian Institute of Astrophysics, Bengaluru; Inter University Centre for Astronomy and Astrophysics, Pune; and Tata Institute of Fundamental Research, Mumbai.
The Aditya Satellite will be placed at Lagrangian point L-1, hence name Aditya L-1 in a Halo Orbit. The satellite will be launched during the event solar maximum {a period of intense activity on the sun and it occurs once in every 11 years}.
Lagrangian points are the locations in space where the combined gravitational pull of two large masses roughly balance each other. Any small mass placed at that location will remains at constant distances relative to the large masses. There are five such points in Sun-Earth system and they are denoted as L1, L2, L3, L4 and L5. A halo orbit is a periodic three-dimensional orbit near the L1, L2 or L3.
It will study the dynamic nature of Sun’s outermost layers viz. Corona and Chromosphere.

Li-Fi uses LEDs and ‘visible’ light to transmit data wirelessly as an alternative to short-range radio.
The standard LED bulbs can be used when attached with a chip and when the output intensity of the light from the bulb is modulated at nanosecond intervals to generate stream of binary codes.
Though it’s a bidirectional technology, currently costs issues don’t allow it to be used for other than data transmission.
It used visible light band of the electromagnetic spectrum 400 and 800 THz frequency (780–375 nm wavelength).
Filament bulbs and fluorescent tubes cannot be used since the light source has to be switched on and off for several thousands of times in a second.
Since this technology is based upon light, it’s a free band which does not need a license. Obviously it would be cheaper than Wi-Fi. Then, the visible light spectrum is 10 thousand times larger then the Radio spectrum and thus is NOT a scare resource.
Since Optical waves don’t pass through the walls, it could be used as a secured communication
The speed of communication can be very high; theoretically it can be 1GB per second.
Light does not interfere with various applications in aviation, medical science etc. For example, in operating rooms, Wi-Fi is not allowed at many places. Similarly, Wi-Fi can interfere with the communication used in aviation.
Unlike Wi-Fi, Li-Fi is not affected by the number of devices using the signal, which is a bonus when compared to traditional Wi-Fi technology.

Li-Fi requires line of sight, when set up outdoors, the apparatus would need to deal with ever-changing conditions.
The major challenge is that how the receiving device would transmit the data back to the sending device.