ION ITM 2011 San Diego, CA Jan. 24-26, 2011 QZSS L1-SAIF Initial Experiment Results T. Sakai, S. Fukushima, and K. Ito Electronic Navigation Research Institute, Japan ION ITM 24-26 Jan. 2011 - ENRI Introduction SLIDE 1 • QZSS (Quasi-Zenith Satellite System) program: – Regional navigation service broadcast from high-elevation angle by three satellites on the inclined geosynchronous (quasi-zenith) orbit; – Broadcast GPS-compatible supplemental signals on three frequencies and two augmentation signals, L1-SAIF and LEX; – The first QZS satellite successfully launched on Sept. 11, 2010. • L1-SAIF (Submeter-class Augmentation with Integrity Function) signal offers: – Sub-meter accuracy wide-area differential correction service; – Integrity function for safety of mobile users; and – Ranging function for position availability; all on L1 single frequency. • ENRI has been developing L1-SAIF signal and experimental facility: – Signal design: SBAS-compatible on L1; – Implemented L1-SAIF Master Station (L1SMS) which generates augmentation message stream in realtime and transmits it to QZSS MCS; – Now conducting experiments on L1-SAIF. ION ITM 24-26 Jan. 2011 - ENRI SLIDE 2 Part 1 Overview of QZSS Program ION ITM 24-26 Jan. 2011 - ENRI Launch of QZS-1 “Michibiki” SLIDE 3 Sept. 11, 2010 20:17JST Launch of QZS-1 “Michibiki” • Launched by H-IIA-18 from Tanegashima Space Center of JAXA; • “Michibiki” was separated successfully 28:27 after launch. Michibiki looked from the second stage (c) MHI (c) JAXA/MHI ION ITM 24-26 Jan. 2011 - ENRI SLIDE 4 QZSS Concept GPS/GEO • Footprint of QZS orbit; • Centered 137E; • Eccentricity 0.1, Inclination 45deg. QZS • Broadcast signal from high elevation angle; • Applicable to navigation services for mountain area and urban canyon; • Augmentation signal from the zenith could help users to acquire other GPS satellites all the time. ION ITM 24-26 Jan. 2011 - ENRI QZSS Program SLIDE 5 • QZSS (Quasi-Zenith Satellite System) program: – Japan has been developing QZSS since FY 2003; – Regional navigation service broadcast from high-elevation angle by combination of three satellites on the inclined geosynchronous (quasi-zenith) orbit; – Broadcast GPS-compatible supplemental signals on three frequencies (L1 C/A, L1C, L2C, and L5) and two augmentation signals, L1-SAIF and LEX. • Participating institutes: – JAXA (Japan Aerospace Exploration Agency): Development and operation of the space segment and Master Control Station; – NICT (National Institute of Information and Communication Technology): Frequency standard and time keeping system including Uplink Station; – AIST (National Institute of Advanced Industrial Science and Technology): Time synchronization between space and ground; – GSI (Geographical Survey Institute): Survey-grade carrier-based positioning service; – ENRI (Electronic Navigation Research Institute): Navigation-grade WADGPS service broadcast by L1-SAIF signal. ION ITM 24-26 Jan. 2011 - ENRI SLIDE 6 Overall Architecture Navigation Signals L1: 1575.42 MHz L2: 1227.60 MHz L5: 1176.45 MHz LEX: 1278.75 MHz QZS Satellite GPS Satellites TWSTFT Up: 4.43453GHz Down: 12.30669GHz Satellite Laser Ranging TT&C / NAV Message Uplink SLR Site Monitor Station NW Time Mgmt Station TT&C / NAV Msg Uplink Station User Receiver Master Control Station (MCS) GEONET (GSI) Function distributed in each institute Timing management by NICT, WADGPS service by ENRI, etc. TWSTFT: Two Way Satellite Time and Frequency Transfer (Courtesy: JAXA QZSS PT) ION ITM 24-26 Jan. 2011 - ENRI SLIDE 7 Space Segment: QZS-1 Mass 4,020kg (wet) 1,802kg (dry) (NAV Payload:320kg) Power Approx. 5.3 kW (EOL) (NAV Payload: Approx. 1.9kW) Design Life 10 years Radiation Cooled TWT TWSTFT Antenna C-band TTC Antenna Laser Reflector L1-SAIF Antenna L-band Helical Array Antenna ION ITM 24-26 Jan. 2011 - ENRI QZSS Signals SLIDE 8 • Supplemental signals: – GPS-compatible L1C/A, L2C, L5, and L1C signals working with GPS; improving availability of navigation; – With minimum modifications from GPS signal specifications; – Coordination with GPS Wing on broadcasting L1C signal; – JAXA is responsible for all supplemental signals. • Augmentation signals: – Augmentation to GPS; Possibly plus Galileo; – L1-SAIF: Compatible with SBAS; reasonable performance for mobile users; – LEX: For carrier-based experimental purposes; member organizations may use as 2kbps experimental data channel; – ENRI is working for L1-SAIF while JAXA is developing LEX. • Interface Specification: IS-QZSS available on JAXA HP – Specifies RF signal interface between QZS satellite and user receiver; – First issue: Jan. 2007; Maintained by JAXA. ION ITM 24-26 Jan. 2011 - ENRI QZSS Frequency Plan Signal Channel Frequency SLIDE 9 Bandwidth Min. Rx Power L1CD 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 24 MHz – 160.0 dBW 25 MHz – 157.9 dBW 25 MHz – 157.9 dBW 42 MHz – 155.7 dBW QZS-L1C 1575.42 MHz QZS-L2C 1227.6 MHz L5I QZS-L5 1176.45 MHz L5Q QZS-LEX 1278.75 MHz Find detail in IS-QZSS document. ION ITM 24-26 Jan. 2011 - ENRI SLIDE 10 Part 2 L1-SAIF Signal Design ION ITM 24-26 Jan. 2011 - ENRI QZSS L1-SAIF Signal SLIDE 11 • QZSS will broadcast wide-area augmentation signal: – Called L1-SAIF (Submeter-class Augmentation with Integrity Function); – Developed by ENRI. • L1-SAIF signal offers: – Wide-area differential correction service for improving position accuracy; Target accuracy: 1 meter for horizontal; – Integrity function for safety of mobile users; and – Ranging function for position availability. • 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 identical with SBAS; – Differences: Large Doppler and additional messages; – Specification of L1-SAIF: IS-QZSS document. ION ITM 24-26 Jan. 2011 - ENRI L1-SAIF Signal QZS satellite SLIDE 12 Ranging Function GPS Constellation Error Correction Integrity Function • Three functions by a single signal: ranging, error correction (Target accuracy: 1m), and integrity; • User receivers can receive both GPS and L1-SAIF signals by a single antenna; • Message-oriented information transmission: flexible contents. SAIF: Submeter-class Augmentation with Integrity Function Ranging Signal User GPS Receivers ION ITM 24-26 Jan. 2011 - ENRI SLIDE 13 WADGPS Concept Clock Correction Ionospheric Correction • Function of user location; • Up to 100 meters; • Vertical structure may be described as a thin shell. Ionosphere • Same contribution to any user location; • Not a function of location; • Needs fast correction. Orbit Correction • Different contribution to different user location; • Not a function of user location; but a function of line-of-sight direction; • Long-term correction. Tropospheric Correction Troposphere • Function of user location, especially height of user; • Up to 20 meters; • Can be corrected enough by a fixed model. ION ITM 24-26 Jan. 2011 - ENRI SLIDE 14 SBAS/L1-SAIF Message Structure Preamble 8 bits Message Type 6 bits Data Field 212 bits 250 bits per second Transmitted First MT CRC parity 24 bits Contents Interval [s] MT Contents Interval [s] 0 Test mode 6 17 GEO almanac 300 1 PRN mask 120 18 IGP mask 300 Fast correction & UDRE 60 24 FC & LTC 6 6 UDRE 6 25 Long-term correction 7 Degradation factor for FC 120 26 Ionospheric delay & GIVE 300 9 GEO ephemeris 120 27 SBAS service message 300 10 Degradation parameter 120 28 Clock-ephemeris covariance 120 12 SBAS time information 300 63 Null message 2~5 120 — Note: Some additional messages are also defined for L1-SAIF. See IS-QZSS. ION ITM 24-26 Jan. 2011 - ENRI SLIDE 15 GPS/L1-SAIF Simulator • GPS/L1-SAIF Simulator: – Simulates GPS L1 C/A and QZSS L1-SAIF signals; – Generates RF signals based on pre-defined GPS and QZSS constellation scenario and signal specifications of IS-GPS and IS-QZSS; – Manufactured by Spirent, modifying GPS/SBAS simulator GSS7700. • Special function for experiment: – Added extra command to input L1-SAIF message from Ethernet port (TCP/IP); – L1-SAIF message is either input by the command externally or generated by the simulator internally. GPS/L1-SAIF Simulator GPS/L1-SAIF Receiver ION ITM 24-26 Jan. 2011 - ENRI GPS/L1-SAIF Receiver SLIDE 16 • Prototype GPS/L1-SAIF Receiver: – Receives GPS L1 C/A and QZSS L1-SAIF signals; – Decode and apply L1-SAIF message as defined by IS-QZSS; – Manufactured by Furuno Electric. • Special function for experiment: – L1-SAIF message can be input from Ethernet port (TCP/IP) as well as L1-SAIF signal on RF; – Enable to process L1-SAIF and SBAS, totally three, augmentation signals simultaneously; – Portable equipage for experiment at remote or on mobile. GPS/L1-SAIF Receiver ION ITM 24-26 Jan. 2011 - ENRI SLIDE 17 RF Compatibility Test ENRI (Chofu, Tokyo) Spirent Scenario File GPS/L1-SAIF Simulator L1-SAIF Signal RF Cable Furuno Electric GPS/L1-SAIF Receiver TCP/IP L1-SAIF Message Decoded Message Compare • Ranging function: The receiver output the proper position solution with pseudorange of L1-SAIF signal generated by the simulator; • Decoding message: The receiver decoded L1-SAIF message which matched with the message input to the simulator via Ethernet port; The command needs to be given 2second before the applicable time of transmission; • Successfully completed in Feb. 2009. ION ITM 24-26 Jan. 2011 - ENRI SLIDE 18 RF Compatibility Test 2008/9/10 00:05:00 to 06:00:00 (6 hours) Standalone GPS L1-SAIF Augmentation OK! ION ITM 24-26 Jan. 2011 - ENRI SLIDE 19 Part 3 L1-SAIF Master Station (L1SMS) ION ITM 24-26 Jan. 2011 - ENRI SLIDE 20 ENRI L1SMS • L1-SAIF Master Station (L1SMS): – Generates L1-SAIF message stream in realtime and transmits it to QZSS MCS developed by and installed at JAXA; – Installed at ENRI, Tokyo; 90km from JAXA Tsukuba Space Center; – Subsystems: GEONET Server, Primary Receiver, Interface Processor, Message Generator, Ionosphere Processor, Troposphere Processor, and Batch Processor. QZS GPS Closed Loop Measured Data L1-SAIF Message GEONET L1SMS QZSS MCS GSI ENRI JAXA ION ITM 24-26 Jan. 2011 - ENRI SLIDE 21 L1SMS Installed at ENRI I/F Message Generator Ionosphere Processor Storage Storage Router to GEONET GEONET Server Storage UPS UPS ION ITM 24-26 Jan. 2011 - ENRI SLIDE 22 Configuration of L1SMS GEONET TCP/IP Observation File (RINEX) via FTP Batch Processor (IFB Estimation) Dual Freq. ANT GEONET Server Primary Receiver Message Output via TCP/IP Interface Processor IFB Estimates L1SMS Batch Subsystem Message Generator (L1SMG) Ionosphere Processor Troposphere Processor L1SMS Realtime Subsystems ION ITM 24-26 Jan. 2011 - ENRI SLIDE 23 Position Error Sample Standalone GPS L1-SAIF Augmentation • Example of user position error at Site 940058 (Takayama; near center of monitor station network); • Realtime operation with MSAS-like 6 monitor stations; • Period: 19-23 Jan. 2008 (5 days). Horizontal Error Vertical Error Standalone RMS GPS Max 1.45 m 2.92 m 6.02 m 8.45 m RMS 0.29 m 0.39 m Max 1.56 m 2.57 m System L1-SAIF Note: Results shown here were obtained with geodeticgrade antenna and receivers at open sky condition. ION ITM 24-26 Jan. 2011 - ENRI Realtime Operation using GEO SLIDE 24 GPS Satellites ETS-VIII Satellite L1-SAIF L1SMS in Tokyo 350 km Separation GPS/L1-SAIF Rx in Sendai Airport • ENRI joined communication experiment of ETS-VIII geostationary satellite; • L1SMS transmitted L1-SAIF message to ETS-VIII; Received L1-SAIF message was input to the GPS/L1-SAIF receiver and processed in realtime; No ranging function; • Successfully completed in Feb. 2009. ION ITM 24-26 Jan. 2011 - ENRI L1-SAIF Receiver Output SLIDE 25 2009/2/17 01:21:39 to 07:23:14 (6 hours) Standalone GPS L1-SAIF Augmentation H Error RMS = 1.221m V Error RMS = 4.043m H Error RMS = 0.412m V Error RMS = 0.464m ION ITM 24-26 Jan. 2011 - ENRI SLIDE 26 Part 4 Experiment with QZS-1 “Michibiki” ION ITM 24-26 Jan. 2011 - ENRI Reception of Test Signal SLIDE 27 • Firstly received L1-SAIF test signal broadcast from QZS on orbit; • By L1-SAIF prototype receiver on Oct. 23, 2010 09:46:48-10:48:07GPST at a branch of ENRI in Sendai Airport, Located at the Northern part of Japan; • Raw pseudorange: receiver clock variation is dominant and there are jumps due to clock adjustment. ION ITM 24-26 Jan. 2011 - ENRI SLIDE 28 Experiment by Car GPS+IMU • L1-SAIF experiment: – L1-SAIF is originally planned as an augmentation to mobile users with a certain velocity; – Experiment with a car; – Location: urban/suburban environment, freeway; – Experiment period: Dec. 2010 to March 2011. • Experiment setup: – Reference: GPS+IMU sensor; – Post-processing with GEONET stations (2030 km separation) for accurate reference; – GPS/L1-SAIF receiver and PC in cabin; – Receives L1-SAIF signal on PRN 183; – Applies L1-SAIF corrections in realtime and outputs position fix. GPS/L1-SAIF Rx ION ITM 24-26 Jan. 2011 - ENRI SLIDE 29 On the Freeway GEONET Ichinomiya GEONET Nakamichi Plan View of the Route 2 km Typical Situation • On Dec. 14, 2010; QZS near the Zenith; • About 10 km drive at the Kofu Basin on Chuo Freeway going westward from Tokyo; • Plain ground with less bridges across the Freeway. Position Error, m Horizontal水平測位誤差(m) 0 15min 時刻(UTC) UTC Time 1:22:08 to 1:37:08 1:36:08 AM 1:35:08 AM 1:34:08 AM 1:33:08 AM 1:32:08 AM 1:31:08 AM 1:30:08 AM 1:29:08 AM 1:28:08 AM 1:27:08 AM 1:26:08 AM 1:25:08 AM 1:24:08 AM 1:23:08 AM 1:22:08 AM ION ITM 24-26 Jan. 2011 - ENRI Freeway: L1-SAIF Augmented SLIDE 30 Chuo Freeway: L1-SAIF Augmentation L1-SAIF測位精度(中央道) 5 4 3 2 1 0.5m Position Error, m Horizontal 水平測位誤差(m) 0 15min 時刻(UTC) UTC Time 1:22:08 to 1:37:08 1:36:08 AM 1:35:08 AM 1:34:08 AM 1:33:08 AM 1:32:08 AM 1:31:08 AM 1:30:08 AM 1:29:08 AM 1:28:08 AM 1:27:08 AM 1:26:08 AM 1:25:08 AM 1:24:08 AM 1:23:08 AM 1:22:08 AM ION ITM 24-26 Jan. 2011 - ENRI Freeway: GPS No Augmentation SLIDE 31 Chuo Freeway: GPS without Augmentation GPS測位精度(中央道) 5 4 3 2 1 1.2m ION ITM 24-26 Jan. 2011 - ENRI SLIDE 32 In Tsukuba City GEONET Tsukuba 1 1 km Plan View of the Route Typical Situation • On Dec. 16, 2010; QZS near the Zenith; • About 6 km drive in West part of Tsukuba City in Ibaraki Pref.; • Road on the ground level with less tall buildings around. Error, m Position Horizontal水平測位誤差 (m) 0 15min 時刻(UTC) UTC Time 5:30:01 to 5:45:01 5:44:01 AM 5:43:01 AM 5:42:01 AM 5:41:01 AM 5:40:01 AM 5:39:01 AM 5:38:01 AM 5:37:01 AM 5:36:01 AM 5:35:01 AM 5:34:01 AM 5:33:01 AM 5:32:01 AM 5:31:01 AM 5:30:01 AM ION ITM 24-26 Jan. 2011 - ENRI Tsukuba: L1-SAIF Augmented SLIDE 33 Tsukuba: L1-SAIF Augmentation L1-SAIF測位精度(つくば2) 5 4 3 2 1 0.6m Error, m Position Horizontal水平測位誤差 (m) 0 15min 時刻(UTC) UTC Time 5:30:01 to 5:45:01 5:44:01 AM 5:43:01 AM 5:42:01 AM 5:41:01 AM 5:40:01 AM 5:39:01 AM 5:38:01 AM 5:37:01 AM 5:36:01 AM 5:35:01 AM 5:34:01 AM 5:33:01 AM 5:32:01 AM 5:31:01 AM 5:30:01 AM ION ITM 24-26 Jan. 2011 - ENRI Tsukuba: GPS No Augmentation SLIDE 34 Tsukuba: GPS without Augmentation GPS測位精度(つくば2) 5 4 3 2 2.0m 1 ION ITM 24-26 Jan. 2011 - ENRI Conclusion SLIDE 35 • ENRI has been developing L1-SAIF signal: – Signal design: GPS/SBAS-compatible; – Planned as an augmentation to mobile users; – Implemented L1-SAIF Master Station (L1SMS) which generates augmentation message stream in realtime and transmit it to QZSS MCS. • QZSS satellite “Michibiki”: – The first satellite for QZSS, “Michibiki”, was successfully launched; – Successfully passed initial function tests for Bus and Mission by end Nov.; – Currently in the nominal operation status. • Ongoing work: – Now L1-SAIF experiment has been conducted by ENRI; – Preliminary results show accuracy improvement by L1-SAIF augmentation.