Presentation on theme: "First Meeting of ionospheric Studies Task Force (ISTF/1)"— Presentation transcript:
1First Meeting of ionospheric Studies Task Force (ISTF/1) 27th -29th Feb 2012Ionospheric data collection and analysis over Indian region - Recent resultsByC.L.Indi, Jt. GM (GAGAN)Surendra Sunda, Manager (GAGAN)Airports Authority of India
2Overview Current status of GAGAN Receiver and Data formats Data ProcessingTEC variabilityRecent resultsScintillationGSAT-8Loss of lockDepletions
3GAGAN works as per ICAO SARPS 2004200720082013GAGANSDCM2011GAGAN supports for interoperability of SBAS & seamless air navigation in the World
7GAGAN Configuration ● ● ● ● GSAT-10INLUS #3PRN 127 (DD)GSAT- 15GSAT In-orbit SpareINLUS #1PRN 127(BG)GSAT-8INLUS #2PRN128 (BG)DATA COMMUNICATION NETWORK @ 2 Mbps / 128 Kbps (OFC Link)INMCC #1(BG)DATA COMMUNICATION NETWORK @ 128 Kbps /2Mbps(OFC & V Sat - 4 Link)INMCC #2GPS 1 to 32INRES-2INRES-1INRES-15● ● ● ●SIS with PRN 127SIS with PRN 128DATA COMMUNICATION NETWORK @ 128 Kbps /2Mbps(OFC & V Sat - 4 Link)
8GAGAN Configuration # Sub System No of Sites Location Status 1Master Control Centre (INMCC)2BengaluruOperationalLand Uplink Station (INLUS)DelhiInstallation in Progress3Reference Station (INRES)15AhmedabadBhubaneswarKolkataDibrugarhGayaGoaGuwahatiJaisalmerJammuNagpurPorbandarPortblairTrivandrum4Data communication Network(DCN)2 OFC Networks2 VSAT Networks1 OFC & 1 VSAT Circuits Operational5GEO SatellitesGSAT8, GSAT10 & GSAT15GSAT 8 Integrated & Test SIS available
9GAGAN Space Segment Coverage PRN127PRN128GSAT- 8 at 55°GSAT-10 at 82°GSAT-15 at 83°
11Grid Based Ionosphere Model For GAGAN IGM-MLDF (Indian GIVE Model- Multi Layer Data Fusion):New Multi layer Grid Based ModelUses Data Fusion TechniqueProvides GIVD, GIVE at 350 km (as per MOPS)This model does not call for any change to the existing SBASmessage structureNo change for the legacy usersAlgorithm evaluated using :GAGAN TEC receiver dataHigh quality live data (supertruth) collected over 15 INRES locationsAchievable APV1 performance during nominal days:76% over Indian land mass
12GPS- TEC data Stations Total 26 receiver stations Latitude range – 8.5o N to 31o NLongitude range o E to 92.7o EMinimum separation- 400 Km
13Receiver and Data Format GSV4004(23)RINEX V.2.10ISMRNovatel OEMV3(3)
14Data 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.
15RINEX V.2.10 sample 2.10 OBSERVATION DATA G (GPS) RINEX VERSION / TYPE Convert Aug :58 PGM / RUN BY / DATESignal Strength values S1,S2 are in dBHz COMMENTMARKER NAMEMARKER NUMBEROBSERVER / AGENCYNovAtel GPSCard REC # / TYPE / VERSANT # / TYPEAPPROX POSITION XYZANTENNA: DELTA H/E/NWAVELENGTH FACT L1/2G02 G03 G04 G06 G07 G08 G09WAVELENGTH FACT L1/2G10 G11 G12 G13 G14 G15 G16WAVELENGTH FACT L1/2G17 G18 G19 G20 G21 G22 G23WAVELENGTH FACT L1/2G24 G25 G26 G27 G28 G29 G30WAVELENGTH FACT L1/2G31 G WAVELENGTH FACT L1/2COMMENT8 C1 L1 D1 S1 P2 L2 D2 S # / TYPES OF OBSERVINTERVALGPS TIME OF FIRST OBSGPS TIME OF LAST OBSLeap Seconds Unknown COMMENTEND OF HEADERG23G13G08G27G25G07G28G03G19
17TEC 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.
18Scintillation Effects on GNSS GPSSBASGrid basedmodelReduced AvailabilityLoss of lockLoss oflockUnder Samplinguser positionOutage of GNSSServicePoorGDOPSignalFadingGIVEReduced Accuracy
19Recent 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-continuedThe 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.
21Day-wise Scintillation occurrence in October 2011
22Scintillation examples in 2011 13/10/2011Hyd12/10/2011MUMPRN-15PRN-1512/10/2011VIZ12/10/2011HydPRN-18PRN-22
23Scintillation 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.
24Examples of GSAT-8 Scintillation measurements 28/10/2011IPP N, 780 EIPP N, E
25Comparison of GPS and GSAT-8 Nov 9Nov 10GPSPRN-31
26Impact 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),.
27Loss of lock - effect on satellite availability GayaKolkataApril 6April 6SevereScintillationDayNo. of Visiblesatellitesgoing downdue to scintillationApril 9April 9ScintillationFree day
28Impact 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).6 April, Severe Scintillation Day9 April,2011- Scintillation Free day
29DepletionDeep depletions (plasma bubbles) have been observed at various stations during 2011.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-390 TECBubbleLoss of Lock
30DepletionbubbleAhmedabadA 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.
31Slant 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 kmSharp rise in differential delay for SAC and Ahmedabad airport receivers is observed at the boundaries of bubble.