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Ionospheric data collection and analysis over Indian region - Recent results

Ionospheric data collection and analysis over Indian region - Recent results. By C.L.Indi, Jt. GM (GAGAN) Surendra Sunda, Manager (GAGAN) Airports Authority of India. First Meeting of ionospheric Studies Task Force (ISTF/1) 27 th -29 th Feb 2012. Overview. Current status of GAGAN

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Ionospheric data collection and analysis over Indian region - Recent results

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  1. Ionospheric data collection and analysis over Indian region- Recent results By C.L.Indi, Jt. GM (GAGAN) Surendra Sunda, Manager (GAGAN) Airports Authority of India First Meeting of ionospheric Studies Task Force (ISTF/1) 27th -29th Feb 2012

  2. Overview Current status of GAGAN Receiver and Data formats Data Processing TEC variability Recent results Scintillation GSAT-8 Loss of lock Depletions

  3. 2008 2007 2004 GAGAN 2013 GAGAN works as per ICAO SARPS SDCM 2011 GAGAN supports for interoperability of SBAS & seamless air navigation in the World

  4. GAGAN Segments GAGAN Space Segment GPS (24) GEO (3) GAGAN SIS Civilian Aircraft GAGAN User Segment GAGAN Ground Segment 24 GPS core Constellation 3 GEO – GSAT-8, GSAT-10, GSAT-15 (@ 55° , 82° , 83° longitude) INMCC (2) INLUS (3) INRE (15) GAGAN for safety of life application. Provides GEO PRN127 & 128 with certified RNP0.1 (for Enroute) & APV1 (for Approach) level of service 128KBps/2MBps DCN(4) 15 INRES: (GAH,GBG,GBS,GCC,GDP,GGO,GGT,GGY,GJU, GJR,GMN,GNP.GPB,GPR,GTV) 2 INMCC (Bangalore- GBM & GBC) 3 INLUS (Bangalore – GBL & GLL & Delhi - GDL. ) 4 DCN

  5. GAGAN – Ground Segment GDL Gaya Gaya GBL GLL * GBM GBC GAGAN Reference Station (15) GAGAN Master Control Centre (2) GAGAN Land Up Link Station (3)

  6. INMCC CTF Building INLUS 11m Antenna 1 2 4 3 Bangalore INRES Facility VSAT Antenna (6.3m Dia) GAGAN Ground Segment Sites

  7. GAGAN Configuration GPS 1 to 32 INLUS #3 PRN 127 (DD) INLUS #1 PRN 127(BG) INLUS #2 PRN128 (BG) DATA COMMUNICATION NETWORK @ 2 Mbps / 128 Kbps (OFC Link) DATA COMMUNICATION NETWORK @ 2 Mbps / 128 Kbps (OFC Link) DATA COMMUNICATION NETWORK @ 128 Kbps /2Mbps(OFC & V Sat - 4 Link) INMCC #2 (BG) INMCC #1 (BG) INRES-1 INRES-2 INRES-15 GSAT-10 GSAT- 15 GSAT-8 SIS withPRN 128 GSAT-15 In-orbit Spare SIS withPRN 127 DATA COMMUNICATION NETWORK @ 128 Kbps /2Mbps(OFC & V Sat - 4 Link) ● ● ● ●

  8. GAGAN Configuration

  9. GAGAN Space Segment Coverage PRN128 PRN127 GSAT- 8 at 55° GSAT-15 at 83° GSAT-10 at 82°

  10. GAGAN Milestone June 2012 July 2013 Aug 2003 May 2006 Aug 2007 June 2009 Dec 2010 May 2011 July 2011 July 2011 Dec 2011 Mar 2012 GAGAN Certification TEST SIS GSAT-8 Launch GSAT-10 Launch TDS FSAT MLDF Model TDS PSAT FOP PSAT FOP FSAT GEO-8 Integration TDS START FOP START TDS RFP(2002) TDS Phase(2003-07) TDS RFP(2009) FOP Phase(2009-13) 1 Yrs 4 Yrs 1 Yrs 4 Yrs

  11. Grid Based Ionosphere Model For GAGAN • IGM-MLDF (Indian GIVE Model- Multi Layer Data Fusion): • New Multi layer Grid Based Model • Uses Data Fusion Technique • Provides GIVD, GIVE at 350 km (as per MOPS) • This model does not call for any change to the existing SBAS • message structure • No change for the legacy users • Algorithm evaluated using : • GAGAN TEC receiver data • High quality live data (supertruth) collected over 15 INRES locations • Achievable APV1 performance during nominal days: • 76% over Indian land mass

  12. GPS- TEC data Stations Total 26 receiver stations Latitude range – 8.5o N to 31o N Longitude range- 72.2 o E to 92.7o E Minimum separation- 400 Km

  13. Receiver and Data Format

  14. Data format-continued • RINEX (Level 1) • Raw binary data is converted into RINEX V.2.10 using the Novatel’s ‘Convert4’ tool. • Sampling interval is 10 seconds. • Format is different from that of IGS stations. • ISMR (Level 2) • Standard output format in GSV receivers. • Provides slant TEC, Scintillation index, C/No, satellite position, Lock time etc. at one minute interval. • Kalman filter is used for receiver bias still there is an issue in bias estimation.

  15. RINEX V.2.10 sample 2.10 OBSERVATION DATA G (GPS) RINEX VERSION / TYPE Convert 27-Aug-2009 09:58 PGM / RUN BY / DATE Signal Strength values S1,S2 are in dBHz COMMENT MARKER NAME MARKER NUMBER OBSERVER / AGENCY NovAtel GPSCard REC # / TYPE / VERS ANT # / TYPE 1668621.9862 5475083.1776 2805416.9267 APPROX POSITION XYZ 0.0000 0.0000 0.0000 ANTENNA: DELTA H/E/N 1 1 WAVELENGTH FACT L1/2 1 1 7 G02 G03 G04 G06 G07 G08 G09WAVELENGTH FACT L1/2 1 1 7 G10 G11 G12 G13 G14 G15 G16WAVELENGTH FACT L1/2 1 1 7 G17 G18 G19 G20 G21 G22 G23WAVELENGTH FACT L1/2 1 1 7 G24 G25 G26 G27 G28 G29 G30WAVELENGTH FACT L1/2 1 1 2 G31 G32 WAVELENGTH FACT L1/2 COMMENT COMMENT 8 C1 L1 D1 S1 P2 L2 D2 S2 # / TYPES OF OBSERV 10.000 INTERVAL 2008 09 11 06 24 40.0000000 GPS TIME OF FIRST OBS 2008 09 12 06 24 30.0000000 GPS TIME OF LAST OBS Leap Seconds Unknown COMMENT END OF HEADER 08 09 11 06 24 40.0000000 0 9G23G13G08G27G25G07G28G03G19 -33768328.06149-177453830.89549 -2902.06249 49.619 -33768324.54448 -138275715.81748 -2261.50048 46.266 -35328933.82449-185654810.44349 -1173.87549 51.669 -35328931.46449 -144666068.99349 -914.87549 51.600 -33034931.25049-173599714.79949 2254.62549 48.078 -33034927.88447 -135272481.22747 1756.68847 44.583 -33946541.40549-178390264.37449 1471.25049 50.869 -33946538.78749 -139005377.87249 1146.25049 50.019 -34300753.31149-180251685.45049 227.31249 51.596 -34300750.36449 -140455847.24249 176.93849 51.127

  16. DATA PROCESSING Raw binary data ISMR CODE Website P1C1 Bias APPLY SATELLITE BIAS Monthly APPLY RECEIVER BIAS KALMAN FILTER Rx Bias Monthly ISMR OUTPUT ( EXCEL)

  17. TEC Variability TEC shows a good correlation with solar activity. Annual, semi-annual, seasonal and diurnal variations of TEC have been studied using the continuous data measurement from 2004 onwards. Large day-to-day variations are prominent feature of anomaly region.

  18. Scintillation Effects on GNSS GPS SBAS Reduced Availability Grid based model Loss of lock Loss of lock Under Sampling user position Outage of GNSS Service Poor GDOP Signal Fading GIVE Reduced Accuracy

  19. Recent results on scintillation A sharp rise in the number of scintillation events with their strength and duration has been observed with increasing solar activity in 2011. Total scintillation epochs (S4>0.4) from all the receivers in 2004 were around 6000 whereas in 2011 they shoot up to 60,000 i.e. 900% increase in the scintillation occurrence. The maximum duration of scintillation event/patch (continuous S4>0.4) observed in 2004 was of 25 minute whereas it is of 80 min in 2011. October 2011 witnessed the maximum scintillation of moderate to severe intensity. It was almost a daily phenomena during this month.

  20. -continued • The characteristics have been defined very well using the continuous data of 2004-2011 over the Indian equatorial and low latitude region. • Maximum probability of scintillation occurrence is between 2000 hrs to 2230 hrs local time. • The strength of scintillation increases in accordance with EIA. It is severe at the crest of EIA due to high background electron density and moderate to low at magnetic equator from where it originates.

  21. Day-wise Scintillation occurrence in October 2011

  22. Scintillation examples in 2011 13/10/2011 Hyd 12/10/2011 MUM PRN-15 PRN-15 12/10/2011 VIZ 12/10/2011 Hyd PRN-18 PRN-22

  23. Scintillation observations from GSAT-8 Observations from GAGAN satellite GSAT-8 (PRN-127) may give new insight into the spatial and temporal variations of scintillation due to its fixed position (IPP) contrary to GPS satellites. It can be helpful in determining the plasma bubble drift velocity. Very strong scintillation of the duration of about 2 hours have been observed. Scintillation impact on SBAS satellite is more severe as it directs affects the GNSS Service and its availability. Two to Three SBAS satellites at different positions may help in avoiding the scintillation impact.

  24. Examples of GSAT-8 Scintillation measurements 28/10/2011 IPP- 23.20 N, 780 E IPP- 21.50 N, 71.20 E

  25. Comparison of GPS and GSAT-8 GSAT-8 Nov 9 Nov 10 GPS PRN-31

  26. Impact of Scintillation- Loss of lock Loss of lock is one of the major effects of scintillation. Severe scintillation over a large coverage area may impact more than 2 satellites leading to loss of lock. This may lead to poor GDOP thereby reducing the accuracy of position. A case study on quantitative analysis of loss of lock is carried out on a severe scintillation day. Though L2 gets unlock more often than L1 due to weaker strength, the analysis was done on L1 signal unlock which is also used as downlink frequency for SBAS satellites. The analysis is based on RINEX data (10 sec interval),.

  27. Loss of lock- effect on satellite availability Gaya Kolkata April 6 April 6 Severe Scintillation Day No. of Visible satellites going down due to scintillation April 9 April 9 Scintillation Free day

  28. Impact of Scintillation – Loss of lock 6 April, 2011- Severe Scintillation Day 9 April,2011- Scintillation Free day Total number of IPPs drop down drastically during scintillation period starting from ~14 UT to ~19 UT. There is ~15% reduction in the number of IPPs during severe scintillation period (14UT to 16 UT).

  29. Depletion • Deep depletions (plasma bubbles) have been observed at various stations during 2011. • Depletions are mostly associated with scintillation. • Depth of depletion in the order of 30-80 Slant TEC units ( 5 m - 13m slant delay) are observed. MUM 13/10/11 PRN-3 90 TEC Bubble Loss of Lock

  30. A very large depletion / plasma bubble, with the depth of 46 TEC units ~ 7.5 meters is observed at Ahmedabad for PRN-13 on March 29, 2011 between 16-17 UT. The width of bubble is ~ 200 Km through which satellite signal traverses for close to 30 min. The onset IPP is 19.430 N, 73.300 E and end IPP is 17.620 N, 73.630 E, thus satellite was traveling in opposite direction of bubble. Depletion bubble Ahmedabad

  31. Slant differential range delay • Slant Differential range delay is calculated using 3 GPS receivers at Ahmedabad for PRN -13. • RX ID – 925 and 214 are collocated at SAC and RX ID 527 is installed at Ahmedabad Airport having a radial distance of ~15 km • Sharp rise in differential delay for SAC and Ahmedabad airport receivers is observed at the boundaries of bubble.

  32. Thank You

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