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अंतरिक्ष विभाग
भारतीय अंतरिक्ष अनुसंधान संगठन

लोक सूचना : सावधान : नौकरी पाने के इच्छुक उम्मीदवार

यू.आर.राव उपग्रह केंद्र (यू.आर.एस.सी), अं‍तरिक्ष विभाग, इसरो, बेंगलूरु में प्रतिनियुक्ति के आधार पर वेतन मैट्रिक्‍स (7वां केंद्रीय वेतन आयोग) के स्‍तर 14 में नियंत्रक के पद की भर्ती (आवेदन की अंतिम तिथि है: 15/11/2021)
चंद्रयान-2 विज्ञान आंकड़ा उपयोगीता के लिए अवसर की घोषणा। प्रस्ताव प्रस्तुत करने की अंतिम तिथि 31 अक्तूबर 2021 है।
वर्तमान ई-प्रापण साइट का नई वेबसाइट में रूपांतरण करना प्रस्तावित है। सभी पंजीकृत/नये विक्रेताओं से नई वेबसाइट का अवलोकन करने तथा इसरो केंद्रों के साथ भाग लेने के लिए अपने प्रत्यय-पत्र का वैधीकरण करने का अनुरोध किया जाता है।


  1. What is NavIC? How is it different from IRNSS?
  • NavIC (Navigation with Indian Constellation) is the name of the independent stand-alone navigation satellite system of India.
  • This system was earlier known as IRNSS (Indian Regional Navigation Satellite System).
  • The name NavIC was coined by the Hon. Prime Minister of India on the occasion of completion of the constellation in April 2016.


  1. Which are the current navigation satellite systems operational in the world?
  • Currently, there are four global systems viz., GPS from USA, GLONASS from Russia, Galileo from European Union and BeiDou from China.
  • In addition, there are two regional systems viz., NavIC from India and QZSS from Japan.


  1. Common location tracking devices in India indicate “GPS” on them. Does it mean that the product supports only GPS? Is GPS a generic term for satellite navigation?
  • GPS is the name of the navigation satellite system owned by USA. On similar lines, Russia, European Union, China, India and Japan have their own navigation satellite systems namely GLONASS, Galileo, BeiDou, NavIC and QZSS respectively.
  • GPS is not a generic term for satellite navigation. The correct term is GNSS, which comprises of all the above systems.
  • Common location tracking devices are capable of receiving signals from many or all of the above systems, including NavIC.
  • Hence it is appropriate that the devices indicate that they are capable of “GNSS” instead of “GPS”.


  1. Some mobile phone applications show“location” as “GPS” on the display. Is it correct to do so?
  • GPS is the name of the navigation satellite system owned by USA. On similar lines, Russia, European Union, China, India and Japan have their own navigation satellite systems namely GLONASS, Galileo, BeiDou, NavIC and QZSS respectively.
  • Mobile phone applications use the location value computed using signalsreceived by the phone hardware. These signals could be from many or all of the above navigation systems, including NavIC.
  • Hence it is appropriate that the applicationsin the mobile phones indicate the term “location” instead of “GPS”.


  1. What is the need for NavIC when already GPS, GLONASS, Galileo and BeiDou are operating?
  • GPS and GLONASS are operated by defence agencies of the respective nations. It is possible that the civilian service can be degraded or denied.
  • NavIC is an independent regional system over the Indian region and does not depend on other systems for providing position service within the service region.
  • It is fully under the control of Government of India.


  1. What are the various segments of NavIC?
  • NavIC, like any other navigation satellite system, consists of three segments:
    • Space segment: Consists of the constellation of satellites.
    • Ground segment: Consists of a network of ground stations that generate navigation data to be uplinked to the satellites, and subsequently to be used by the user receiver for aiding in position computation.
    • User segment: Consists of the users utilizing the navigation signals for the purpose of position, navigation, and timing.


  1. Which are the international bodies involved in NavIC co-ordination activity?
  • International Telecommunication Union (ITU)
  • United Nations Office for Outer Space Affairs (UNOOSA)
  • International Committee on GNSS (ICG)
  • Other navigation service providers (like GPS, GLONASS, Galileo, BeiDou, QZSS)


  1. Can revenue be generated using NavIC?
  • NavIC is conceived and built mainly with the aim of having an independent navigation satellite system for India to remove the dependence on foreign satellite systems for navigation service requirements, especially for the strategic sector.
  • It is not built for the purpose of revenue generation.
  • However, many civilian applications are possible using free-to-air navigation signals broadcast from the satellites.
  • The industry can produce receivers capable of receiving NavIC signal and use for various applications in several areas.
  • Thus, economic benefit will accrue to the Indian economy by usage of position and navigation technologies.


  1. What is GNSS?
  • GNSS is an acronym for global navigation satellite systems.
  • GNSS allows users worldwide to pinpoint their locations or the locations of objects, other people and goods at any given moment.


  1. What is the difference between global and regional navigation systems?
  • Global navigation system caters to the users in the entire world, whereas regional navigation system caters to the users in the limited service area.


  1. What is the principle of navigation system operation?
  • Satellite navigation is based on the use of range measurements between navigational satellite and the user.
  • Information about the satellite’s coordinates is given to the user through navigation signal.
  • Range measurements are based on the calculation of the receiving signal time delay compared with the signals generated by the user equipment.


  1. What is the minimal quantity of the satellites needed for users positioning?
  • For determining position and time, a minimum of four satellites are required.
  • In ideal case, when the measurements are precise and satellite time is identical with the user’s equipment time, the user position can be computed with 3 satellites.
  • In reality, satellite time differs from the time on user’s equipment.
  • So,difference between user equipment time and satellite time also needs to be determined. That is the reason four satellites are needed.


  1. Is there a limit on the number of users for any satellite based navigation system?
  • There is no limit on the number of users.
  • The satellite based navigation system sends signals in broadcast mode, and any number of users within the coverage area can receive the signals.


  1. Why are atomic clocks used in navigation satellites?
  • Atomic clocks are highly accurate and stable clocks, with errors of less than 10 nanoseconds.
  • The low errors results in providing accurate ranging for position determination.


  1. What is GAGAN?
  • GAGAN stands for GPS Aided Geo Augmented Navigation.
  • It is a satellite based augmentation system developed primarily for safety-of-life civil aviation applications catering to the Indian airspace.
  • It provides correction and integrity messages for GPS.
  • GAGAN has been established jointly by ISRO and AAI. It is being operated and maintained by AAI.


  1. How GAGAN and NavIC systems can be compared?
  • Following are the major differences between GAGAN and NavIC systems:



An augmentation to the GPS

An independent stand-alone navigation system

Provides integrity information

Does not provide integrity information

Provides safety-of-life operation support

Does not support safety-of-life operations