ION 2012 GNSS 2012 ION GNSS Sept Slide

ION 2012 GNSS 2012 ION GNSS Sept. - Slide Nashville, TN Sept. 17 -21, 2012 The L 1 -SAIF Signal How was it designed to be used? Takeyasu Sakai Electronic Navigation Research Institute

ION GNSS Sept. 2012 - Slide 1 Introduction • QZSS (Quasi-Zenith Satellite System) program: – Regional navigation service broadcast from high-elevation angle by a combination of three or more satellites on the inclined geosynchronous (quasi-zenith) orbit; – Broadcast GPS-like supplemental signals on three frequencies and Two Augmentation Signals, L 1 -SAIF and LEX; – The first QZS satellite was successfully launched on Sept. 11, 2010. • L 1 -SAIF (Submeter-class Augmentation with Integrity Function) signal: – Augmentation service on L 1 single frequency designed for mobile users; – Signal design: SBAS-like message stream on L 1 C/A code (PRN 183). • ENRI has been developing L 1 -SAIF signal and conducting experiments: – L 1 -SAIF Master Station (L 1 SMS) experimental facility installed at ENRI; – IS-QZSS contains specification of L 1 -SAIF signal as well as other signals.

ION GNSS Sept. 2012 - Slide 2 QZSS Concept GPS/GEO • • • Footprint of QZSS orbit; Centered at longitude of 135 E; Eccentricity 0. 075, Inclination 43 deg. 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 at any time.

ION GNSS Sept. 2012 - Slide 3 Inclined Geosynchronous Orbit Apogee 40, 000 km 8: 40 15: 20 Perigee 32, 000 km Orbital Planes of QZSS (3 SVs) Ground Track • Semi-major axis (42, 164 km) is equal to GEO orbit: synchronous with rotation of the earth; • Inclined obit makes ground track ‘ 8’-figure; Called IGSO or Quasi-Zenith Orbit; • With three or more satellites on the same ground track, navigation service can be provided from the zenith to regional users at any time.

ION GNSS Sept. 2012 - Slide 4 Broadcast from the Zenith 75. 9 deg 3 satellites constellation @Tokyo 80. 3 deg 4 satellites constellation @Tokyo • The constellation of 3 or more QZS satellites is capable of broadcasting signals from near the zenith to regional users at any time; • This property is attractive for augmentation channel; Users can expect to receive the augmentation signal anytime anywhere.

ION GNSS Sept. 2012 - Slide 5 Space Segment: QZS-1 Mass 4, 020 kg (wet) 1, 802 kg (dry) (NAV Payload： 320 kg) Power Approx. 5. 3 k. W (EOL) (NAV Payload: Approx. 1. 9 k. W) Design Life 10 years m 3. 5 2 Radiation Cooled TWT Successfully launched on Sept. 11, 2010 and settled on Quasi. Zenith Orbit (IGSO). TWSTFT Antenna C-band TTC Antenna Nickname: “Michibiki” Laser Reflector L 1 -SAIF Antenna L-band Helical Array Antenna

ION GNSS Sept. 2012 - Slide 6 Frequency Plan Signal QZS-L 1 C Channel Frequency L 1 CD L 1 CP 1575. 42 MHz QZS-L 1 -C/A QZS-L 2 C QZS-L 5 L 5 I L 5 Q 1227. 6 MHz 1176. 45 MHz Bandwidth Min. Rx Power 24 MHz – 163. 0 d. BW 24 MHz – 158. 25 d. BW 24 MHz – 158. 5 d. BW 24 MHz – 160. 0 d. BW 25 MHz – 157. 9 d. BW QZS-L 1 -SAIF 1575. 42 MHz 24 MHz – 161. 0 d. BW QZS-LEX 1278. 75 MHz 42 MHz – 155. 7 d. BW Interoperability GPS-like supplemental signals with minimum modifications from GPS signals SBAS-like augmentation signal (250 bps) QZSS-specific augmentation signal (2 kbps) Find detail in IS-QZSS document.

ION GNSS Sept. 2012 - Slide 7 QZSS L 1 -SAIF Signal • QZSS broadcasts wide-area augmentation signal: – Called L 1 -SAIF (Submeter-class Augmentation with Integrity Function); – Augmentation signal for mobile users designed and developed by ENRI. • L 1 -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 improving position availability. • Augmentation to GPS L 1 C/A based on the SBAS specifications: – Broadcast on L 1 freq. with RHCP; Common antenna and RF front-end; w w w Modulated by BPSK with C/A code (PRN 183); 250 bps data rate with 1/2 FEC; Message structure is identical with SBAS; Differences from SBAS: PRN, large Doppler, and some additional messages. – Developed easily if one has the experience to develop SBAS-capable receiver; – Specification of L 1 -SAIF: See IS-QZSS document (Available at JAXA HP).

ION GNSS Sept. 2012 - Slide 8 L 1 -SAIF Signal Functions 3 Functions by L 1 -SAIF QZS satellites Ranging Function GPS Constellation Error Correction Integrity Function • Three functions by a single signal: ranging, error correction (Target accuracy: 1 m), and integrity; • User receivers can receive both GPS and L 1 -SAIF signals with a single antenna and RF front-end; • Message-oriented information transmission: Flexible contents. SAIF： Submeter-class Augmentation with Integrity Function Ranging Signal User GPS/L 1 -SAIF Receivers

ION GNSS Sept. 2012 - Slide 9 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. • Broadcast separate corrections to each error factor to enlarge the service area; • User receivers reconstruct pseudorange corrections with regard to its location.

ION GNSS Sept. 2012 - Slide 10 L 1 -SAIF Message Structure Preamble 8 bits Transmitted first Sync to GPS epoch Message Type 6 bits Data Field 212 bits CRC parity 24 bits 250 bits per second Message Type Contents 0 to 7, 10, 18 to 28, 62, 63 • Basic messages compatible with SBAS • Submeter accuracy correction could be achieved by these messages only 9, 12, 17 • These messages are for geostationary satellites • Not used for L 1 -SAIF 52 to 61 • L 1 -SAIF original messages • Receiver implementation is optional Note: Message Types 29 to 61 have no definitions in the current specification of SBAS. • Message structure is identical with SBAS; • Basic function is supported by only SBAS-compatible messages; Easy to develop!

ION GNSS Sept. 2012 - Slide 11 L 1 -SAIF Master Station • L 1 -SAIF Master Station (L 1 SMS): – Generates L 1 -SAIF message stream in realtime and transmits it to QZSS MCS developed by and installed at JAXA; – Installed at ENRI, Tokyo; 90 km from JAXA Tsukuba Space Center; – Dual frequency GPS measurements at some locations in Japan necessary to generate L 1 -SAIF messages are sent from GEONET in realtime. GPS Satellites Measurements IF A -S 1 L L 1 SMS al n g Si k lin Up GEONET Ra ng in g Si gn al nd ba K- g in g n Ra al n g Si QZS L 1 -SAIF Message QZSS MCS GSI Server ENRI JAXA TKSC (Tokyo) (Tsukuba)

ION GNSS Sept. 2012 - Slide 12 L 1 SMS at ENRI I/F Message Generator Ionosphere Processor Storage Router to GEONET/JAXA GEONET Server Storage UPS

ION GNSS Sept. 2012 - Slide 13 Preliminary Result 6 reference stations User location for this test Standalone GPS L 1 -SAIF Augmentation • Example of user position error at Site 940058 (Takayama); • Realtime operation with MSAS-like 6 reference stations in Japan; • Period: 19 -23 Jan. 2008 (5 days). L 1 -SAIF experimental area Horizontal Error 1. 45 m Standalone RMS GPS Max 6. 02 m RMS 0. 29 m L 1 -SAIF Max 1. 56 m System Vertical Error 2. 92 m 8. 45 m 0. 39 m 2. 57 m Note: Results shown here were obtained with geodeticgrade antenna and receivers at open sky condition.

ION GNSS Sept. 2012 - Slide 14 Realtime Operation using GEO GPS Satellites ETS-VIII Satellite L 1 -SAIF L 1 SMS in Tokyo 350 km Separation GPS/L 1 -SAIF Rx in Sendai Airport • ENRI joined communication experiment of ETS-VIII geostationary satellite; • L 1 SMS transmitted L 1 -SAIF message to ETS-VIII; Received L 1 -SAIF message was input to the GPS/L 1 -SAIF receiver and processed in realtime; No ranging function; • Successfully completed in Feb. 2009.

ION GNSS Sept. 2012 - Slide 15 Resulted Position via GEO 2009/2/17 01: 21: 39 to 07: 23: 14 (6 hours) Standalone GPS L 1 -SAIF Augmentation H Error RMS = 1. 221 m V Error RMS = 4. 043 m H Error RMS = 0. 412 m V Error RMS = 0. 464 m

ION GNSS Sept. 2012 - Slide 16 Experiment by Car GPS+IMU • L 1 -SAIF technical verification experiment: – L 1 -SAIF is originally planned as an augmentation for mobile users; – Conducted 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/L 1 -SAIF receiver and PC in cabin; – Receives L 1 -SAIF signal on PRN 183; – Applies L 1 -SAIF corrections in realtime and outputs position fix. GPS/L 1 -SAIF Receiver

ION GNSS Sept. 2012 - Slide 17 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.

0 H: mm: ss tt UTC Time時刻（UTC） 1: 22: 08 to 1: 37: 08 15 min H: mm: ss tt H: mm: ss tt 5 H: mm: ss tt 1 H: mm: ss tt 2 H: mm: ss tt 3 Horizontal Position Error, m 4 H: mm: ss tt 水平測位誤差（m） ION GNSS Sept. 2012 - Slide 18 Freeway: No Augmentation Chuo Freeway: GPS without Augmentation GPS測位精度（中央道） 1. 2 m

0 H: mm: ss tt UTC Time時刻（UTC） 1: 22: 08 to 1: 37: 08 15 min H: mm: ss tt H: mm: ss tt H: mm: ss tt 5 H: mm: ss tt 1 H: mm: ss tt 2 H: mm: ss tt 3 Horizontal Position Error, m 4 H: mm: ss tt 水平測位誤差（m） ION GNSS Sept. 2012 - Slide 19 Freeway: L 1 -SAIF Augmented Chuo Freeway: L 1 -SAIF Augmentation L 1 -SAIF測位精度（中央道） 0. 5 m

ION GNSS Sept. 2012 - Slide 20 In the 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.

0 H: mm: ss tt UTC Time 5: 30: 01 to 5: 45: 01 時刻（UTC） 15 min H: mm: ss tt H: mm: ss tt 5 H: mm: ss tt 1 H: mm: ss tt 2 H: mm: ss tt 3 Horizontal Position Error, m 4 H: mm: ss tt 水平測位誤差 （ｍ） ION GNSS Sept. 2012 - Slide 21 City: No Augmentation Tsukuba: GPS without Augmentation GPS測位精度（つくば 2） 2. 0 m

0 H: mm: ss tt UTC Time 5: 30: 01 to 5: 45: 01 H: mm: ss tt 時刻（UTC） 15 min H: mm: ss tt H: mm: ss tt 5 H: mm: ss tt 1 H: mm: ss tt 2 H: mm: ss tt 3 Horizontal Position Error, m 4 H: mm: ss tt 水平測位誤差 （ｍ） ION GNSS Sept. 2012 - Slide 22 City: L 1 -SAIF Augmented Tsukuba: L 1 -SAIF Augmentation L 1 -SAIF測位精度（つくば 2） 0. 6 m

ION GNSS Sept. 2012 - Slide 23 Ranging by L 1 -SAIF 2011 -08 -18 02: 18: 45 to 21: 16: 20 L 1 -SAIF (PRN 183) Ranging ON L 1 SMS Configuration: 6 DF GPS GMS (GEONET) 4 SF GPS/QZS GMS (JAXA) User location: @ENRI, Tokyo Receiver: JAVAD ALPHA-G 3 T Processing by ENRI Mask 5 deg, Smoothing 100 s L 1 -SAIF Correction L 1 -SAIF Ranging ON Hor RMS Hor Max Ver RMS Ver Max OFF 0. 680 m 8. 686 m 0. 988 m 13. 308 m ON 0. 658 m 2. 494 m 0. 937 m 4. 682 m

ION GNSS Sept. 2012 - Slide 24 Conclusion • ENRI has developed L 1 -SAIF augmentation signal: – Planned as an augmentation for mobile users; – Signal design: SBAS-like message stream on L 1 C/A code (PRN 183); – The first QZSS satellite “Michibiki” has been broadcasting L 1 -SAIF signal. • Experiments for L 1 -SAIF: – ENRI has implemented L 1 -SAIF Master Station (L 1 SMS) which generates augmentation message stream in realtime and transmit it to QZSS MCS; – Preliminary tests have shown promising performance; – Technical verification experiments confirmed the performance for mobile users. • Ongoing work: – – Continue experiments regularly (two weeks per month); Define messages to be used to broadcast regional information; Support augmentation to GLONASS satellites for further improvement of availability; Support dual frequency operations. Information available at: http: //www. enri. go. jp/sat/qzss_e. htm