1. T. Sakai, T. Yoshihara, S. Fukushima, and K. Ito Electronic Navigation Research Institute, Japan T. Sakai, T. Yoshihara, S. Fukushima, and K. Ito Electronic Navigation Research Institute, Japan The Ionospheric Correction Processor for SBAS and QZSS L1-SAIF The Ionospheric Correction Processor for SBAS and QZSS L1-SAIF ION ITM 2009 Anaheim, CA Jan. 26-28, 2009

2. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 1 MSAS has been operational since 2007:MSAS has been operational since 2007: –SBAS augmentation signal offers: wide-area differential correction, integrity function, and ranging function. QZSS will broadcast another augmentation signal in 2010:QZSS will broadcast another augmentation signal in 2010: –ENRI is developing L1-SAIF (Submeter-class Augmentation with Integrity Function) on GPS/SBAS L1 frequency; –Upper compatible with SBAS signal; Also offers WADGPS, integrity, and ranging. Ionosphere is a major problem for both systems:Ionosphere is a major problem for both systems: –Developed the Ionospheric Correction Processor (ICP) independent from WADGPS correction processor; –Implemented and integrated with QZSS L1-SAIF Message Generator (L1SMG); Tested successfully. Introduction

3. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 2 Part 1 Overview of MSAS and QZSS L1-SAIF Programs

4. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 3 WADGPS Concept Orbit Correction Troposphere Ionosphere Ionospheric Correction Tropospheric Correction Clock Correction Same contribution to any user location;Same contribution to any user location; Not a function of location;Not a function of location; Needs fast correction.Needs fast correction. Different contribution to different user location;Different contribution to different user location; Not a function of user location; but a function of line-of-sight direction;Not a function of user location; but a function of line-of-sight direction; Long-term correction.Long-term correction. Function of user location;Function of user location; Up to 100 meters;Up to 100 meters; Vertical structure may be described as a thin shell.Vertical structure may be described as a thin shell. Function of user location, especially height of user;Function of user location, especially height of user; Up to 20 meters;Up to 20 meters; Can be corrected enough by a fixed model.Can be corrected enough by a fixed model.

5. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 4 MSAS Status Satellite navigation for civil aviation use:Satellite navigation for civil aviation use: –SBAS international standard; –Compatible with US WAAS and European EGNOS. MSAS facilities:MSAS facilities: –2 GEOs: MTSAT-1R (PRN 129) and MTSAT-2 (PRN 137) on orbit; –6 domestic GMSs and 2 RMSs (Hawaii and Australia) connected with 2 MCSs; –IOC WAAS software with localization. IOC service since Sept. 27, 2007:IOC service since Sept. 27, 2007: –Certified for Enroute to NPA operations as a sole mean navigation; –Stable operation. MTSAT-1R MTSAT-2

6. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 5 MSAS Performance Horizontal Position Accuracy RMS 0.42m MAX 1.64m GPS MSAS @Kawagoe (93011) 08/1/17-19 PRN129 Vertical Position Accuracy RMS 0.57m MAX 2.34m GPS MSAS @Kawagoe (93011) 08/1/17-19 PRN129

7. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 6 Concerns for MSAS The current MSAS is built on the IOC WAAS:The current MSAS is built on the IOC WAAS: –As the first satellite navigation system developed by Japan, the design tends to be conservative; –The primary purpose is providing horizontal navigation means to aviation users; Ionopsheric corrections may not be used; –Achieves 100% availability of Enroute to NPA flight modes. The major concern for vertical guidance is ionosphere:The major concern for vertical guidance is ionosphere: –The ionospheric term is dominant factor of position solution uncertainty; –Necessary to reduce ionospheric uncertainty to provide vertical guidance with reasonable availability.

8. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 7 QZS GPS/GEO Signal from high elevation angleSignal from high elevation angle Applicable to navigation services for mountain area and urban canyonApplicable to navigation services for mountain area and urban canyon QZSS Concept Footprint of QZS orbitFootprint of QZS orbit Centered 137ECentered 137E Eccentricity 0.1, Inclination 45degEccentricity 0.1, Inclination 45deg

9. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 8 Supplement signals:Supplement signals: –GPS-compatible L1C/A, L2C, L5, and L1C signals working with GPS; For improving availability of navigation; –With minimum modifications from GPS signal specifications; –Coordination with GPS Wing on broadcasting L1C signal; –JAXA is responsible for all supplement signals. Augmentation signals:Augmentation signals: –Augmentation to GPS; Possibly plus Galileo; –L1-SAIF (Submeter-class Augmentation with Integrity Function): compatible with SBAS; reasonable performance for mobile users; –LEX: for experimental purposes; member organizations may use as 2kbps experimental data channel; –ENRI is working for L1-SAIF and JAXA is developing LEX. QZSS Signals

10. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 9 QZSS Frequency Plan SignalChannelFrequencyBandwidth Min. Rx Power QZS-L1CL1CD 1575.42 MHz 24 MHz –163.0 dBW L1CP 24 MHz – 158.25 dBW QZS-L1-C/A 24 MHz – 158.5 dBW QZS-L1-SAIF 24 MHz – 161.0 dBW QZS-L2C 1227.6 MHz 24 MHz – 160.0 dBW QZS-L5L5I 1176.45 MHz 25 MHz – 157.9 dBW L5Q 25 MHz – 157.9 dBW QZS-LEX 1278.75 MHz 42 MHz – 155.7 dBW Find detail in IS-QZSS document.

11. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 10 QZSS will broadcast wide-area augmentation signal:QZSS will broadcast wide-area augmentation signal: –Called L1-SAIF (Submeter-class Augmentation with Integrity Function); –Developed by ENRI. L1-SAIF signal offers:L1-SAIF signal offers: –Wide-area differential corrections for improving position accuracy; Target accuracy: 1 meter for horizontal; –Integrity function for safety of mobile users; and –Ranging function to improve signal availability. Interoperable with GPS L1C/A and fully compatible with SBAS:Interoperable with GPS L1C/A and fully compatible with SBAS: –Broadcast on L1 freq. with RHCP; Common antenna and RF front-end; –Modulated by BPSK with C/A code; –250 bps data rate with 1/2 FEC; message structure is same as SBAS. QZSS L1-SAIF Signal

12. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 11 SBAS/L1-SAIF Message Structure Preamble 8 bits Message Type 6 bits Data Field 212 bits CRC parity 24 bits 250 bits per second MT 0 1 2～52～52～52～5 6 7 9 10 12 17 18 Contents Test mode PRN mask Fast correction & UDRE UDRE Degradation factor for FC GEO ephemeris Degradation parameter SBAS time information GEO almanac IGP mask Interval[s] 6 120 60 6 120 120 120 300 300 300 24 25 26 27 28 63 FC & LTC Long-term correction Ionospheric delay & GIVE SBAS service message Clock-ephemeris covariance Null message 6 120 300 300 120 — MTContentsInterval[s] Transmitted First

13. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 12 SBAS/L1-SAIF Message (1) Message Type ContentsCompatibilityStatus 0 Test mode BothFixed 1 PRN mask BothFixed 2 to 5 Fast correction & UDRE BothFixed 6UDREBothFixed 7 Degradation factor for FC BothFixed 10 Degradation parameter BothFixed 18 IGP mask BothFixed 24 Mixed fast/long-term correction BothFixed 25 Long-term correction BothFixed 26 Ionospheric delay & GIVE BothFixed 9 GEO ephemeris SBASFixed 17 GEO almanac SBASFixed 12 SBAS network time SBASFixed 8ReservedSBASFixed

14. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 13 SBAS/L1-SAIF Message (2) Message Type ContentsCompatibilityStatus 27 SBAS service message SBASFixed 29 to 51 (Undefined)—— 28 Clock-ephemeris covariance BothFixed 62ReservedBothFixed 63 Null message BothFixed 52 TGP mask L1-SAIFTentative 56 Intersignal biases L1-SAIFTentative 57 (Ephemeris-related parameter) L1-SAIFTBD 58 QZS ephemeris L1-SAIFTentative 59 (QZS almanac) L1-SAIFTBD 60 (Regional information) L1-SAIFTBD 61ReservedL1-SAIFTentative 5３5３5３5３ Tropospheric delay L1-SAIFTentative 54 to 55 (Advanced Ionospheric delay) L1-SAIFTBD

15. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 14 Part 2 Ionospheric Correction Processor (ICP) and L1-SAIF Message Generator

16. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 15 L1-SAIF Master Station (L1SMS):L1-SAIF Master Station (L1SMS): –Generates L1-SAIF message stream in realtime and transmits them to QZSS MCS developed by JAXA; –Installed at ENRI, Tokyo; –Subsystems: GEONET Server, Primary Receiver, Interface Processor, Message Generator, Ionosphere Processor, Troposphere Processor, and Batch Processor. ENRI L1SMS L1SMSGEONET QZS QZSS MCS GPS MeasuredDataL1-SAIFMessage GSIENRIJAXA L1-SAIF Signal L1C/A, L2P K-band ClosedLoop

17. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 16 GEONET Server:GEONET Server: –Receives dual frequency measurement from GEONET operated by Geographical Survey Institute (GSI), Japan; –Output rate: 1 sample per second (1 Hz); In native binary format of receivers; Latency is less than 2 seconds; –5 servers for 1,000 GEONET stations distributed all over Japan. Primary Receiver:Primary Receiver: –Installed inside L1SMS with connection via Ethernet LAN; –Provides measurements for immediate response to satellite failure to ensure integrity function; –Collects navigation message every subframe; –Provides the actual time to the message generator; –Currently NovAtel OEM-3 MiLLennium-STD. L1SMS Subsystems (1)

18. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 17 L1SMS Subsystems (2) Interface Processor:Interface Processor: –Distributes GPS measurement data stream to other processors; –Other subsystem processors access to this processor for measurements to avoid generating lots of direct connections to GEONET Server and Primary Receiver; –Also relays L1-SAIF message packets from Message Generator to QZSS MCS at JAXA. Message Generator (L1SMG):Message Generator (L1SMG): –Generates L1-SAIF message with clock and orbit corrections; –Variable configuration of monitor stations; –Accepts several types of receiver: RINEX, NovAtel, Trimble, JAVAD; –Standard planar fit algorithm for ionospheric correction; Identical with WAAS/MSAS ionospheric corrections; –Standard correction model for troposphere.

19. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 18 L1SMS Subsystems (3) Ionospheric Correction Processor (ICP):Ionospheric Correction Processor (ICP): –Generates ionospheric correction and integrity information based on vast number of monitor stations; –Tested with realtime measurements from up to 200 monitor stations; –IGP location is not fixed and identified by QUERY command; –This processor is optional; If not exist, L1SMG employs its own standard algorithm. Tropospheric Correction Processor (under development):Tropospheric Correction Processor (under development): –Estimates atmospheric condition and generates tropospheric delay; –Semi-realtime estimation: latency is less than 5 min; –Formats delay information into vertical delay at TGP (tropospheric grid point) like IGP for ionosphere; –Also optional; If not exist, standard troposphere model is used.

20. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 19 L1SMS Subsystems (4) Batch Processor:Batch Processor: –Estimates satellite and receiver hardware biases so-called Inter- frequency bias or L1/L2 bias; –Runs on daily basis; Constructs model of ionosphere based on measurements for at least two days and performs estimation; –Provides stable and accurate estimation in comparison with a realtime sequential processing. Data Storage Server:Data Storage Server: –Very large capacity storage with RAID configuration; –Holds input measurements and resulted message stream for several months (depending on the number of monitor stations).

21. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 20 L1SMS Installed at ENRI Storage Router to GEONET I/F UPS UPSMessageGeneratorGEONETServer Storage Ionosphere Processor Storage

22. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 21 Configuration of L1SMS GEONET Server Ionosphere Processor Troposphere Processor Message Generator (L1SMG) GEONET Batch Processor (IFB Estimation) L1SMS Batch Subsystem L1SMS Realtime Subsystems TCP/IP MessageOutput via TCP/IP Observation File (RINEX) via FTP IFBEstimates Primary Receiver Interface Processor Dual Freq. Ant.

23. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 22 Message Generator (L1SMG) Input Module L1-SAIF Message Generator (L1SMG) MessageOutput Primary Receiver Messaging Module Ionospheric Correction (Standard Planar Fit) GEONET Server MessageLog Time and NAV Message Input from Iono Processor GMS measurement (6 stations) Clock and Orbit Correction Dual Freq. Ant. Ionospheric Correction Processor (ICP) Input Module Ionospheric Correction Module QUERY RESPONSE IMS measurement (200 stations)

24. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 23 Command and Response VariableBytesUnit Command Time8(double) Number of IGPs2— IGP 1 Latitude20.1 deg Longitude20.1 deg : IGP n Latitude20.1 deg Longitude20.1 deg VariableBytesUnit Response Time8(double) Number of IGPs2— IGP 1 Vertical Delay8(double) GIVE8(double) : IGP n Vertical Delay8(double) GIVE8(double) QUERY Command RESPONSE Message Each command and message is packed with Header and CRC;Each command and message is packed with Header and CRC; QUERY command identifies location of each IGP; ICP computes vertical delay for each IGP location separately;QUERY command identifies location of each IGP; ICP computes vertical delay for each IGP location separately; If Message Generator could not receive any response from ICP for 150 seconds, the command shall be timed out.If Message Generator could not receive any response from ICP for 150 seconds, the command shall be timed out.

25. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 24 Realtime Operation Test Tested performance of the ICP Implemented as a subsystem of L1SMS; running with L1SMG;Tested performance of the ICP Implemented as a subsystem of L1SMS; running with L1SMG; Analyzed user position error at 14 evaluation locations; Numbered from North to South;Analyzed user position error at 14 evaluation locations; Numbered from North to South; Used GEONET stations as all monitor stations and evaluation sites.Used GEONET stations as all monitor stations and evaluation sites. GMS Stations (6) for L1SMG L1-SAIF Experimental Area IMS Station (200) for ICP Evaluation Locations (14)

26. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 25 Results – Position Error Sample Example of user positioning error at Site #5 93022 Choshi (East of Tokyo);Example of user positioning error at Site #5 93022 Choshi (East of Tokyo); ICP: 200 IMS, 5-deg IGP, 0th Order Fit;ICP: 200 IMS, 5-deg IGP, 0th Order Fit; Period: 16-21 Jan. 2009 (5 days).Period: 16-21 Jan. 2009 (5 days). MSAS Augmentation Standalone GPS L1-SAIF Augmentation System Horizontal Error Vertical Error L1-SAIF RMS 0.23 m0.36 m MAX 1.67 m3.35 m MSAS RMS 0.46 m0.59 m MAX 1.73 m2.43 m Standalone GPS RMS 1.25 m2.99 m MAX 4.30 m8.11 m

27. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 26 Computation Time Request 42 IGPs (5 deg) RESPONSEMessage Request 143 IGPs (2.5 deg) 16 seconds for 101 IGPs 7 seconds for 42 IGPs L1SMGICPConnection ACK QUERYCommand RESPONSEMessage QUERYCommand Delay and GIVE Cache for 42 IGPs Computation Time 0.16 s / IGP

28. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 27 Test Cases CaseABCDEMSAS Ionospheric Correction Made by L1SMGICP MSAS Used Stations6 GMS200 IMS 6 GMS IGP grid5 deg 2.5 deg 5 deg Estimation Order110101 Rmax (km)21001000 2100 Nmax30 Nmin10 Rmax, Nmax, and Nmin are parameters to select ionospheric pierce point (IPP) measurements to be used for estimate the IGP delay;Rmax, Nmax, and Nmin are parameters to select ionospheric pierce point (IPP) measurements to be used for estimate the IGP delay; The ICP collects IPPs within smaller radius because 200 IMS stations provide vast number of measurements.The ICP collects IPPs within smaller radius because 200 IMS stations provide vast number of measurements.

29. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 28 Location vs. Horizontal Accuracy ICP improves position accuracy in the Southern Region;ICP improves position accuracy in the Southern Region; First order estimation is better to ensure accuracy.First order estimation is better to ensure accuracy.

30. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 29 Location vs. Vertical Accuracy 1 meter accuracy is achievable even for vertical direction;1 meter accuracy is achievable even for vertical direction; Note that these results associate with solar minimum phase.Note that these results associate with solar minimum phase.

31. ION ITM 26-28 Jan. 2009 - ENRI S LIDE 30Conclusion ENRI has been developing QZSS L1-SAIF signal:ENRI has been developing QZSS L1-SAIF signal: –L1-SAIF augmentation signal on GPS/SBAS L1 frequency; –Signal design: upper compatible with SBAS. Development of Ionospheric Correction Processor (ICP):Development of Ionospheric Correction Processor (ICP): –Improves accuracy of WADGPS such as SBAS and L1-SAIF; –Implemented as a subsystem of L1-SAIF Master Station; Respond to QUERY command issued from L1-SAIF Message Generator; –Achievable accuracy: 0.2-0.3m horizontal at center of Japan; 0.5-0.7m at the edge of service area; Note: nominal condition of solar minimum phase. Future works will include:Future works will include: –Verify the performance during ionospheric storm condition; –Consider other L1-SAIF message formats for ionospheric correction. –Contact: sakai@enri.go.jp