Presentation on theme: "Ionospheric data collection and analysis over Indian region - Recent results By C.L.Indi, Jt. GM (GAGAN) Surendra Sunda, Manager (GAGAN) Airports Authority."— Presentation transcript:
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 Receiver and Data formats Data Processing TEC variability Recent results Scintillation GSAT-8 Loss of lock Depletions
GAGAN works as per ICAO SARPS GAGAN SDCM 2011 GAGAN supports for interoperability of SBAS & seamless air navigation in the World
GAGAN Configuration GSAT-10 INLUS #3 PRN 127 (DD) GSAT- 15 GSAT-15 In-orbit Spare INLUS #1 PRN 127(BG) GSAT-8 INLUS #2 PRN128 (BG ) DATA COMMUNICATION 2 Mbps / 128 Kbps (OFC Link) INMCC #1 (BG) DATA COMMUNICATION 128 Kbps /2Mbps(OFC & V Sat - 4 Link) INMCC #2 (BG) GPS 1 to 32 INRES-2INRES-1INRES-15 SIS with PRN 127 SIS with PRN 128 DATA COMMUNICATION 128 Kbps /2Mbps(OFC & V Sat - 4 Link)
#Sub SystemNo of Sites Location Status 1 Master Control Centre (INMCC)2BengaluruOperational 2 Land Uplink Station (INLUS)2121 Bengaluru Delhi Operational Installation in Progress 3 Reference Station (INRES)15 1. Ahmedabad 2. Bengaluru 3. Bhubaneswar 4. Kolkata 5. Delhi 6. Dibrugarh 7. Gaya 8. Goa 9. Guwahati 10. Jaisalmer 11. Jammu 12. Nagpur 13. Porbandar 14. Portblair 15. Trivandrum Operational 4 Data communication Network(DCN) 42 OFC Networks 2 VSAT Networks 1 OFC & 1 VSAT Circuits Operational 5 GEO Satellites3GSAT8, GSAT10 & GSAT15GSAT 8 Integrated & Test SIS available GAGAN Configuration
GAGAN Space Segment Coverage GSAT- 8 at 55° GSAT-15 at 83°GSAT-10 at 82° PRN127 PRN128
Aug 2003 June 2009 Dec 2010 July 2011 May 2011 Dec 2011 June 2012 Mar 2012 July 2013 May 2006 Aug 2007 TDS START TDS PSAT TDS FSAT FOP START FOP PSAT GSAT-8 Launch MLDF Model GEO-8 Integration TEST SIS GSAT-10 Launch FOP FSAT GAGAN Certification GAGAN Milestone TDS Phase( )FOP Phase( )TDS RFP(2002)TDS RFP(2009) 1 Yrs 4 Yrs1 Yrs4 Yrs
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
GPS- TEC data Stations Total 26 receiver stations Latitude range – 8.5 o N to 31 o N Longitude range o E to 92.7 o E Minimum separation- 400 Km 12
GSV4004 (23) RINEX V.2.10 ISMR Novatel OEMV3 (3) RINEX V.2.10 Receiver and Data Format
Data format- continued RINEX (Level 1) Raw binary data is converted into RINEX V.2.10 using the Novatels 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.
RINEX V.2.10 sample 2.10 OBSERVATION DATA G (GPS) RINEX VERSION / TYPE Convert 27-Aug :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 APPROX POSITION XYZ ANTENNA: DELTA H/E/N 1 1 WAVELENGTH FACT L1/ G02 G03 G04 G06 G07 G08 G09WAVELENGTH FACT L1/ G10 G11 G12 G13 G14 G15 G16WAVELENGTH FACT L1/ G17 G18 G19 G20 G21 G22 G23WAVELENGTH FACT L1/ G24 G25 G26 G27 G28 G29 G30WAVELENGTH FACT L1/ G31 G32 WAVELENGTH FACT L1/2 COMMENT 8 C1 L1 D1 S1 P2 L2 D2 S2 # / TYPES OF OBSERV INTERVAL GPS TIME OF FIRST OBS GPS TIME OF LAST OBS Leap Seconds Unknown COMMENT END OF HEADER G23G13G08G27G25G07G28G03G
DATA PROCESSING Raw binary data ISMR APPLY SATELLITE BIAS APPLY RECEIVER BIAS ISMR OUTPUT ( EXCEL) KALMAN FILTER Rx Bias CODE Website P1C1 Bias Monthly
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.
Loss of lock Loss of lock Poor GDOP Outage of GNSS Service Reduced Accuracy GIVE Under Sampling Signal Fading Reduced Availability Scintillation Effects on GNSS GPS SBAS Grid based model user position
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 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 October 2011 witnessed the maximum scintillation of moderate to severe intensity. It was almost a daily phenomena during this month.
-continued The characteristics have been defined very well using the continuous data of 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.
Day-wise Scintillation occurrence in October 2011
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.
Examples of GSAT-8 Scintillation measurements IPP N, E IPP N, 78 0 E 28/10/2011
Comparison of GPS and GSAT-8 Nov 9Nov 10 GSAT-8 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 Scintillation Free day April 6 Kolkata Gaya No. of Visible satellites going down due to scintillation Severe Scintillation Day April 9
Impact of Scintillation – Loss of lock 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) April, Severe Scintillation Day 9 April,2011- Scintillation Free day
Depletion Deep depletions (plasma bubbles) have been observed at various stations during Depletions are mostly associated with scintillation. Depth of depletion in the order of Slant TEC units ( 5 m - 13m slant delay) are observed. MUM13/10/11PRN-3 Bubble Loss of Lock 90 TEC
Depletion 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 UT. The width of bubble is ~ 200 Km through which satellite signal traverses for close to 30 min. The onset IPP is N, E and end IPP is N, E, thus satellite was traveling in opposite direction of bubble. Ahmedabad bubble
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.