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Atomic clocks on indigenous navigation satellite IRNSS-1A develops snag

The atomic clocks on the first satellite IRNSS-1A of the NavIC (Navigation with Indian Constellation), the indigenously built satellite-based positioning system, has developed a technical snag.

One of the three crucial rubidium timekeepers (atomic clock) on IRNSS-1A satellites failed six months ago and the other two followed subsequently. ISRO will soon launch one of its back up navigation satellites as a replacement to IRNSS-1A satellite.

Key Facts
  • Remaining satellites of NavIC constellation (having total 7 satellites) are performing their core function of providing accurate position, navigation and time.
  • Each satellite has three clocks and a total of 27 clocks for the navigation satellite system. These clocks are supplied same foreign vendor. These clocks are important to provide precise data.
  • The troubled IRNSS-1A spacecraft was put in space in July 2013 and has an expected life span of 10 years. The seventh navigation satellite, IRNSS-1G, was launched in April 2016.

Atomic clock: It is an extremely accurate type of clock regulated by the vibrations of an atomic or molecular system. Its principle of operation is not based on nuclear physics, but rather on atomic physics. It uses the microwave signal that electrons in atoms emit when they change energy levels. The accuracy of an atomic clock depends on two factors, temperature of the sample atoms and frequency and intrinsic width of the electronic transition (higher frequencies and narrow lines increase the precision).

About NavIC (Navigation with Indian Constellation)

  • NavIC also known as the Indian Regional Navigation Satellite System (IRNSS) is similar to the GPS (Global Positioning System) of US, Glonass of Russia and Galileo of Europe as well as China’s Beidou.
  • Starting in July 2013, ISRO had launched all the seven navigation satellites of the IRNSS by April 2016. Each satellite has a life span of 10 years.
  • IRNSS is said to be the “Indian GPS” that will give accurate real-time positioning and timing services over India and the region around it extending to 1,500km. Thus, NAVIC’s reach is regional.
  • Applications of IRNSS: terrestrial, aerial and marine navigation, terrestrial navigation for hikers and travellers, vehicle tracking and fleet management, disaster management, integration with mobile phones, mapping and geodetic data capture and visual and voice navigation for drivers. Apart from the civilian applications, it will be used for defence purposes as well.

For more Information: IRNSS

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ISRO Successfully tests Cryogenic Engine for Upper Stage of GSLV Mk III

The Indian Space Research Organisation (ISRO) successfully tested indigenously developed cryogenic engine for the upper stage ‘GSLV Mk III’ rocket.

 The cryogenic upper stage, designated as C25, was tested for 50 seconds at ISRO Propulsion Complex (IPRC) at Mahendragiri in Tamil Nadu demonstrating all the stage operations. It was the first test in a series of two tests.  The second test is planned for flight duration of 640 seconds.

Key Facts 
  • Cryogenic engines are used in the upper stage of a rocket launch as they provide the maximum thrust to a launcher vehicle.
  • The development of C25 cryogenic stage started after approval of GSLV MkIII, ISRO’s next generation launch vehicle, capable of launching heavy four tonne class spacecraft in Geosynchronous Transfer Orbit (GTO).
  • C25 stage was conceptualised, designed and realised by Liquid Propulsion Systems Centre (LPSC) with support from Vikram Sarabhai Space Centre (VSSC), ISRO Propulsion Complex (IPRC) and Sathish Dhawan Space Centre (SDSC).
  • GSLV MkIII vehicle consists of two solid strap-on motors, one earth storable liquid core stage and the cryogenic upper stage.
  • The C25 stage is most powerful upper stage developed by ISRO. It uses Liquid Oxygen and Liquid Hydrogen propellant combination. This stage carries 27.8 tons of propellants loaded in two independent tanks.
  • Note: Development of a cryogenic stage has unique design challenges liquid Oxygen stored at -195 deg C and as liquid Hydrogen is stored at -253 deg C in its tanks. To store these cryogenic fluids, special multi-layer insulation is provided for the tanks and other structures.
Comment

The 50 second test of C25 is a significant milestone in the ISRO’s development of indigenous cryogenic propulsion technology. The successful hot test of the stage in the first attempt itself demonstrates the ISRO’s ability to work in new areas like cryogenic technology. The first flight stage for ‘GSLV MkIII-D1’ mission is in an advanced stage of realisation. It is scheduled to launch GSAT-19 during first quarter of 2017. Its flight engine was successfully tested earlier in the High Altitude Test facility and integrated with the flight stage.

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Scientists creates world’s first stable semi-synthetic organism

Researchers from The Scripps Research Institute (TSRI), US have created world’s first stable semi-synthetic organism, a single-celled bacterium with an expanded genetic code

The semi-synthetic organism is the modified E.coli bacteria created by introducing DNA molecules that are not found in nature in a common bacterium.

How the new bacterium was created?
  • Life’s natural genetic code only contains four natural bases- adenine (A), cytosine (C), guanine (G), thymine (T). These bases pair forms two base pairs in the DNA ladder.
  • The newly created bacterium has two human-created X and Y bases that grow and divide, much like the four natural bases. This single-celled organism can hold on to the synthetic base pair as it divides.
  • The human-created X and Y base pair was dropped over time in the bacterium that limited the ways the it can use the additional information possessed in their DNA.
  • For this, researchers had optimised a tool called a nucleotide transporter, which brings the materials necessary for the unnatural base pair to be copied across the cell membrane.
  • They discovered that modification to the transporter, made it much easier for the organism to grow and divide while holding on to X and Y.
  • Researchers used gene editing tool CRISPR-Cas9 to design the synthetic organism to see a genetic sequence without X and Y as a foreign invader.
Potential Applications
  • This research gives scientists an opportunity to ‘create organisms with wholly unnatural attributes and traits that are not found elsewhere in nature.
  • In future, it can help in creation of microbes capable of manufacturing entirely new proteins, which can provide leads to new medicines and nanotechnology breakthroughs.

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