GPS (GNSS) Update Image: Lockeed Martin Image: USAF What is GPS used for? • Navigation • Precision location and survey • Near-precision weapons • Timing – Secure radios – Bank transactions – Communication networks What is GPS? Global – Coverage is roughly the same over the whole surface of the Earth • Positioning System – Position – Velocity – Time How does GPS work? • About 32 satellites in Medium Earth Orbit. – 20,000km above the Earth • Typically about 10 visible at any time from any location on the Earth • Radio signals transmitted from all GPS satellites are synchronized when transmitted • Arrival time at your receiver varies due to different path lengths, light travels at ‘only’ 300km per millisecond, so many milliseconds of time variation in signal arrivals • In reality, your receiver is not synchronized to GPS time, so it has to find its location in 4 dimensions (x,y,z and time) • For position accuracy of 3m, time accuracy is 10ns (1 on 100 millionth of a second) GPS Signals • The GPS radio signal is a continuous stream of digital data • Most of the data is known by the receiver in advance (Pseudo Random Number, PRN), also known as the Spreading Code – Different for each satellite and signal – Direct Sequence Spread Spectrum (DSSS) • A small amount of data (50 bits per second) is not known in advance, this is information sent by the satellite to your receiver – Data is generally the same on civil and military signals Military Use of GPS • Threats: – Deception (spoofing) – Denial (jamming) – Use by adversary (denial) • Responses: – Encode signal (protects against spoofing and use by adversary) • Use a secret spreading code, and encrypt some data fields – More power and spot beams – Anti-jam antennas and receivers – Alternate (backup/complimentary) systems GPS Military User Equipment - Weapons • JDAM, JASSM, Harpoon II, AMRAAM D, ESSM, SM-2, Excalibur Images: USAF/USN/US Army GPS Military User Equipment - Receivers • DAGR, microDAGR, blue force tracking • Ships, aircraft, UAVs Images: USAF/Skydek GPS Military Anti-jam Antennas Images: Novatel/USN/Cobham/USAF The GPS State as at Nov 2018 • Very robust constellation as at 12 Nov 18 – 31 satellites currently in operation (1 in maintenance) – 1 GPS IIA 34 – 12 GPS IIR 41 43 44 45 46 47 51 (54) 56 59 60 61 – 7 GPS IIR-M 48 50 52 53 55 57 58 – 12 GPS IIF 62 63 64 65 66 67 68 69 70 71 72 73 – SV# 70 launched JDAY 036 (5 Feb 16) via Atlas V • Final Block IIF satellite • First launch of Block III satellite planned for 15 December 2018 – Global GPS civil service performance commitment met continuously since December 1993 Modernisation of GPS • Add Civil code to L2 in quadrature to P(Y)… (L2C) – From Block IIR-M (19 sv in operation at Nov 2018) • Add third frequency (L5) at 1176.45 MHz – From Block IIF (12 sv in operation at Nov 2018) • Different (additional) military signal (M-code) on L1 and L2 – From Block IIR-M (19 sv in operation at Nov 2018) • Different Nav Message (CNAV) – Standard on L2C signals (19 sv in operation at Nov 2018) • Additional L1 Civil signal (L1C) – From Block III (first spacecraft launch planned 7 Dec 2018) • Slightly higher power as a long term trend • Spot beam (~20dB) and flex power for M-code – Block III (first spacecraft launch 7 Dec 2018) The Future of GPS L5 L2 L1 1176MHz 1227MHz 1575MHz C/A Block II/IIA/IIR P(Y) P(Y) L2C C/A Block IIR-M M M P(Y) P(Y) Block IIF M L2C M C/A P(Y) P(Y) C/A & L1C Block III Space Segment Improvements ‘The Future’ of GPS The Future of GPS • The benefits of the new frequencies are linked to the implementation of the OCX control segment • The control segment has been a critical factor in GPS III launch delays GPS Modernisation – New Civil Signals and IS Second civil signal “L2C” • Designed to meet commercial needs • Higher accuracy through ionospheric correction • 1st launch: Sep 2005 (GPS IIR-M); 19 satellites as at 12 Nov 2018 IS-GPS-200H Third civil signal “L5” • Designed to meet demanding requirements for transportation safety-of-life • 1st launch: 2010 (GPS IIF); 12 satellites as at 12 Nov 2018 IS-GPS-705D Fourth civil signal “L1C” • Designed with international partners for GNSS interoperability • Begins with GPS Block III • 1st launch: Dec 2018; 24 satellites: ~ 2021++… IS-GPS-800D GPS Space Segment Scheduling • Block IIR-M – Last launch 2009 – R&D L5 Payload on last IIR-M • Block IIF – First Launched May-2010, final launch Feb 2016 • Satellite Lives exceeding design life (some more than 15 Years) • Block III starts launch 7 Dec 2018 Countermeasures against jamming Ranges and Jamming Levels • Gets Weapon System Closer to the Target • Fewer Sorties Required • One Target One Bomb • Minimizes Collateral Damage GPS/FRPA EGI+FRPA No AJ GPS+CRPA EGI+CRPA EGI+CRPA EGI+CRPA + Ultra -tight EGI+CRPA +Ultra -tight+DAE +Ultra- tight+MBS Time Now Jamming Power Jamming Range 1 kW <.1 nm .1 nm .5 nm 3 nm 7 nm 70 nm 250 nm 10 kW .3 nm .6 nm 1 nm 8 nm 12 nm 230 nm 250 nm 1 MW 3 nm 6 nm 10 nm 80 nm 230 nm 250 nm 250 nm GPS III System Description GPS III GPS III GPS III GPS III High data rate crosslinks High data rate telemetry Continuous Earth Command & Control Coverage Signals On L1, L2 and L5 Spot Beam Signals MCS AMCS Network-Centric Communications Global Military & Civil Users Ground Antenna Monitor Station Other Global Navigation Satellite Systems • European Galileo (and EGNOS) • Chinese Beidou-2/3 (and Beidou-1) • Russian GLONASS • Japanese QZSS (and MSAS) • Indian IRNSS (and GAGAN) EGNOS • European Wide Area Satellite Based Augmentation System • Geostationary transponder with Wide-Area Differential GPS corrections – 1575.42MHz DSSS signal • 2 operational transponders at 12 Nov 18 – PRN 123 & 136 (120 non operational) • Note additional sv ID’s (NMEA-0183) and PRN codes are used for SBAS transponders Galileo • GPS equivalent, with a few subtle changes and driving to L5 signals • DSSS based signaling • 3 (90, 210, 330) orbital planes at 56 deg inclination • E1 and E2 signals nestle in around GPS • L5 signal for Safety of Life services • 17 satellites operational as at 12 Nov 2018 – Plus 4 in commissioning, 2 in testing • Reports of clock failure issues – Galileo uses Passive Hydrogen Maser instead of Caesium or Rubidium Atomic Clocks Beidou-1 • Chinese Satellite Navigation System using Geostationary satellites – Non-ideal geometry, expensive receivers Beidou-2&3 • Full global GNSS, with a bias towards service in China via quasi-geo satellites • DSSS based signaling in L-band – see ICD online (beidou.gov.cn) • MEO satellites for global coverage (growing) • Geo and quasi-geo satellites for coverage in China – Quasi-geo wander in latitude and longitude but remain in the Eastern hemisphere • 17 Beidou satellites in operation as at 12 Nov 18 – Ref: Test and Assessment Research Center of China Satellite Navigation Office • Beidou 3 is new generation (2 of above) with extra and modernised signals – 19 Beidou 3 in testing GLONASS • The original GPS-ski, but with differences • Each satellite on a different frequency (FDMA) – doesn’t directly use CDMA for satellite isolation • 3 orbital planes • Fell into disrepair, but reinvigorated under Vladimir Putin’s rule from mid 2000’s • 24 operational satellites as at 12 Nov 2018 – 2 in test/commissioning • New generation will eliminate FDMA and use solely CDMA/DSSS, just like GPS MSAS • Japanese geostationary SBAS wide area DGPS • 2 satellites in orbit – PRN 129 & 137 QZSS • Japanese GNSS augmentation system • Satellites follow quasi-Geo orbit • Trace out a lopsided figure 8 – Long, slow (high) loop over Japan – Short, fast (low) loop over Australia • Ensures high elevation satellite over Japan – Coverage in urban canyons • WADGPS, – plus extra satellite(s), L1, L2C, L5 – Plus RTK service (1276.75MHz) “LEX” • 4 satellites in orbit as at 12 Nov 2018 – 3 x QZSS, 1 x GEO Image: qzs.jp Indian GAGAN • GPS augmentation System • 2 satellites active as at 16 Feb 2016 – PRN 127 (55 East) and 128 (83 East) – Service on L1 and L5 Indian Regional NSS (IRNSS/NAVIC) • L5 (1176.45MHz) and S-band (2492.028MHz) • SPS (1MHz BPSK) • Precision Service BOC(5,2) • Combination of Geostationary and Geosynchronous orbits • 7 operational satellites in operation at 11 Feb 2018 – IRNSS-1B to 1G – IRNSS-1A clock failure – IRNSS-1H fairing failed to separate on PSLV – IRNSS-1I launched April 2018 Australian WADGPS/SBAS • WADGPS testbed (from July 2017) – Corrections for Australia and NZ • Available over internet and via Inmarsat 4F1 (143.5E) – Multi-constellation (GPS/Galileo) – Precise Point Positioning • Permanent solution funded in May 2018 budget, along with Space Agency What do all these GNSSs mean? • Lots of signals available – Lots of energy – Frequency diversity – Makes jamming difficult • Multiple antennas make deception virtually impossible • Civil receivers are typically cheaper, more modern, lower power, and possibly more resilient than military receivers – But operational utility needs to be thoroughly understood – Military users should assume there is an adversary trying to mess with their systems Conclusion • GNSS Updates reliant on Satellite Replacement Schedule • Satellite lives generally exceed design life • Future upgrades seek to improve overall system performance whilst introducing selective denial and theatre availability • New Signals • New Frequencies • New Constellations • GEO and quasi GEO satellites.