4 gis


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4 gis

  1. 1. Indian Regional Navigational Satellite System Arup Dasgupta Honorary Managing Editor GIS Development, India Primary Navigation System (IRNSS)• Elements Of IRNSS – Constellation – Space Crafts – Signals In Space (Broadcast) – Ground Systems – User Receivers 1
  2. 2. IRNSS Constellation 3 geo-stationary satellites revolving in equatorial orbit 4 geo-synchronous satellites revolving in independent 290 inclined orbits IRNSS – Space Segment• The orbital slots where the 7 satellites will be positioned are 1 each satellite in geo-stationary orbit at 34 0E, 83 0E and 132 0E longitudes and 2 satellites each in geo- synchronous orbit with 290 inclination at 55 0E and 111 0E longitudes• All satellites are configured identically for convenience of realization and production• Each satellite supports 110 Kgs of navigation payload.• Antenna pattern is global in coverage and circular in shape with the beam centre positioned at 10 0N latitude and 83 0E longitude.• Coverage being global (Antenna Global Beam) and circular, no antenna pointing mechanism is required. 2
  3. 3. IRNSS – Space Segment • Continuous yaw manoeuvre of satellites in inclined orbit so as to ensure that sun is always perpendicular to the solar panels. • Satellites to be launched by PSLV. Possibility of launching two satellites onboard GSLV studied as an alternative. • Constellation to be commissioned by 2012. Calls for launching of 1 satellite every 6 months.. • Lift-off mass of each spacecraft is 1370 kgs and power generation capability is 1.6 kW. • Launch strategies being worked out – explained later. • Satellite to carry enough fuel for orbit raising as well as in-orbit manoeuvres. IRNSS Constellation Definition•The 4 satellites in inclined orbits trace a figure of ‘8’ on the earth.•When 2 of the 4 satellites are at equator, other 2 are at extreme positions. 550 E 1110 E longitude longitude 290 GSO 290 GSO 340 E 1320 E longitude longitude GEO GEO 830 E longitude GEO 550 E 1110 E longitude longitude 290 GSO 290 GSO earth’s rotation satellites’s movement 3
  4. 4. Signals In Space• Signals at L Band – 1 MBPS BPSK (similar to GPS C/A) – 2 MBPS BOC (BOC 5, 2)• Signals at S Band – 1 MBPS BPSK – 2 MBPS BOC (BOC 5,2)BOC (Binary Offset Carrier)BOC (5,2) 2 MBPS Code is modulated by a sub carrier of 5 MHz Clock . IRNSS Configuration 8 4
  5. 5. ELEMENTS OF SATELLITE NAVIGATION GROUND SEGMENT PNT ServicesSatellite Navigation is a method employing Global or RegionalConstellation of satellites to accurately determinePosition (P) , Navigation (N) and Time (T)anywhere on the earthUsing a Navigation Satellite System one can determine • Exact Position (Latitude, Longitude and Altitude) • Exact Speed and Direction of travel (course) • Exact Time ( IST,UTC,TAI) 5
  6. 6. Ground Segment TT&C and Nav. Uplink TT&C and User Nav. Uplink Monitor Monitor 1 1 stations stations Two way Two way Ranging Ranging SCC 11 MCC LaserLaser Timing RangingRanging Centre Service Area for IRNSS Longitude 40 deg E to 125 deg E Latitude 30 deg S to 45 deg N 6
  7. 7. IRNSS Ground Segment Objectives• Carry out house-keeping and station-keeping of the IRNSS satellites• Carry out precise orbit determination of all IRNSS Satellites using one way, two-way and laser ranging• Generate maintain and disseminate IRNSS network time using an ensemble of highly stable clocks• Estimate the onboard satellite clock bias and drift rate and ionospheric delay using one way range measurement data• Generate ephemeris parameters that will be broadcast by IRNSS satellites for user community• Have uplink dedicated uplink facility for each satellite for housekeeping and navigation uplinks IRNSS Ground Segment Architecture 34° E 83° E 132° E 55° E 110° E 1 5 6 9 Satellite Control Facility (SCF( M )) Satellite Control Facility Hassan (SCF( R )) Bhopal IRLUS IRLUS SCC +TTC SCC +TTC Backup INC IRNSS Navigation Centre IRNSS CDMA Ranging Bangalore IRNSS Laser Ranging 1-4 IRNWT IRIMS IRIMS 1 17 7
  8. 8. IRNSS Ground Segment Elements• IRNSS Satellite Control Facility ( IRSCF ) – IRNSS TTC and Land Uplink Stations ( IRTTC) - 9 Nos – IRNSS Satellite Control Centre ( IRSCC ) - 2 Nos• IRNSS Range and Integrity Monitoring Stations(IRIMS) - 17Nos• IRNSS Navigation Control Facility ( IRNCF ) – IRNSS Navigation Centre ( INC ) - 2 Nos – IRNSS Network Time ( IRNWT ) - 2 No – IRNSS CDMA Ranging Stations ( IRCDR ) - 4 Nos – IRNSS Laser Ranging Service ( ILRS )• IRNSS Data Communication Network ( IRDCN ) - 2 Nos Iono Modeling Requirements 8
  9. 9. IRIMS Network IRNSSUser Receivers Single Frequency Ionospheric Correction from data in navigation message sent from ground and through extrapolation in receiver through modeling (Less Accurate) Dual Frequency On line ionosphere correction by measuring the delay on two frequencies (More accurate) 9
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