True Origins and Major Original Challenges for GPS Success (1962 – 1978) A Tribute to the “almost forgotten” who labored and sacrificed to make it happen! * Brad Parkinson Stanford University 10/22/09 Stanford CPNT October 2009 1 GPtS – the Stealth Utility • Pre-History and GPS Design • The Key Innovation • 5 Engineering Frontiers • GPS Applications Enabled Note: t = TIME “Success has a thousand Fathers, failure is an orphan.“ -- Unknown Author 10/22/09 Stanford CPNT October 2009 2 Today, GPS Serves over 600 Million Users 10/22/09 Stanford CPNT October 2009 3 Summary – The GPS Concept Four or more Passive Ranging Satellite signals to solve for 4D (3 Shown for clarity) Question: How did we come up with this design in 1973? And Where did we push the Technology/ Engineering Frontiers? Big Point: Eliminates the need for accurate clocks in the user equipment. But Leaves the major Issue: from P. Enge, Scientific American What is the form of the signal? 10/22/09 Stanford CPNT October 2009 4 The Dawn of Satellite Navigation • 4 October 1957 - Sputnik • US Failures and success (31 January 1958) • William Guier and George Weiffenbach (APL) – Doppler Signature Unique – Single Pass Orbit Determination 10/22/09 Stanford CPNT October 2009 5 The Eras of Satellite Navigation 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 Pioneers -Transit 10/22/09 Stanford CPNT October 2009 6 The World in 1966 • There were no: – PCs – CDs and DVDs • And– Cell there Phones/Text was no Monday night Football!!! • NorMessaging was there a GPS – but – Satellite TV – ThereInternet was an existing Satellite-based • Google Navigation System… • Facebook – eMail – iPODS – HDTV 10/22/09 Stanford CPNT October 2009 7 Navy’s Transit • Developed by Dick Kirschner - APL • Doppler (Frequency-based) system • Polar Orbits at 1075 km. (107 Min.) • Satellite – Solar Powered – Gravity Gradient Stabilized By 1964, Some People felt – Scout Launched • 150 and 400 MHzThere (Iono shouldCorrection) be a better way… • Orbit determination and prediction – 12 hrs. • Fix available every few hours • 10 to 16 minutes for a fix – 25 meters / 2D Dick Kirschner – Velocity Correction: 1 knot = 0.2 n. mi. 10/22/09 Stanford CPNT October 2009 8 Tribute to Ivan Getting (Co-recipient of the Draper Prize – 2002) Dr. Ivan Getting • Saw the need and possibilities President Aerospace Corporation • Major instigator/supporter of Key USAF/621B System Studies (1962-1972) • “Getting was a tireless advocate of the project in the face of early resistance from the Pentagon.” • While not directly involved in the GPS development, continued strong advocacy in the Pentagon 1973-1978 10/22/09 Stanford CPNT October 2009 9 The Eras of Satellite Navigation 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 Pioneers -Transit Competition System Study System Study Woodward 621B 621B Woodward • 1st Oper. Sys. / Transit (Jan 1964-1996) • New Systems Proposed (mid 1960’s) • 621B (USAF) 10/22/09 Stanford CPNT October 2009 10 First “GPS” System Study- USAF 621B The 1966 Woodford/Nakamura Secret System Study Preliminary 1964 – Final Released in 1966 Originally Classified Secret and could not be discussed in Public – Not declassified until 1979 This was the real foundation of the decisions in the “Lonely-Halls” Pentagon Meeting 10/22/09 Stanford CPNT October 2009 11 First “GPS” System Study- USAF 621B The 1966 Woodford/Nakamura Secret System Study Preliminary 1964 – Final Released in 1966 A True System study: • Advocated Passive Ranging – Next step-which technique? • Advocated Atomic Clocks in Space for Navigation • Explored 4 Dimensional Navigation (triple Δρ) • User did not require an Atomic clock • Directly led to building Prototype CDMA (PRN) Navigation receivers and the USAF/621B tests at WSMR 1970-1972 10/22/09 Stanford CPNT October 2009 12 Advocacy for Atomic Clocks in USAF/621B Study of 1964-1966 10/22/09 Stanford CPNT October 2009 13 USAF/621B Study of 1964/66 Recommended Development of Space qualified Atomic Clock and Demo of tracking signal 10/22/09 Stanford CPNT October 2009 14 In-depth USAF/621B System Studies Intensified from 1966-1974 • Extended and Modified Original Study • Aerospace Library still Archives over 90 listings – – At least four are still (apparently!) classified. • Subjects Included: – Analysis of Passive Ranging Techniques • CDMA emerged as a strongest contender – 621B Receiver Accuracy – Analysis of Orbits – Error and Testing Analysis – Estimation of costs for DNSDP – Comprehensive studies of Tactical mission enhancement 10/22/09 Stanford CPNT October 2009 15 The Frontier in 1964-66 Use of Spread-Spectrum CDMA for Passive Ranging All signals at the same Frequency “Correlation” in GPS receivers identifies and locks on each one 10/22/09 Stanford CPNT October 2009 16 In 1966 -Many Questions about CDMA • Signal Acquisition (Doppler and Phase) • Ability to encrypt signal • Selection of Codes: – False Lock (Right code, wrong phase!) – Maintaining Orthogonality for all codes (30 sats - 435 combinations) – Adding Additional Satellites • Complexity of Receiver • Rejection of Accidental or Deliberate Interference • Communication Capability – Satellite Location and Time 10/22/09 Stanford CPNT October 2009 17 The Eras of Satellite Navigation 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 Pioneers -Transit Competition System Study System Study Woodward 621B 621B Woodward 621B CDMA 621B CDMA • 1st Oper. Sys. / Transit (Jan 1964-1996) Navigation Receivers Tests Navigation Receivers Tests • New Systems Proposed (mid 1960’s) • 621B (USAF) 10/22/09 Stanford CPNT October 2009 18 USAF/621B Woodford Study – Alternative Passive Ranging Techniques (1966) GPS (621B demo: 1971/73) 10/22/09 Stanford CPNT October 2009 19 621B Analyses and Tests of Prototype Receivers and CDMA Signal Structure 1966 -1973 • Gold Codes Invented in 1967 • Two versions of Receiver Built • Tested with CDMA passive ranging • Transmitters in an “Inverted” Satellite configuration –the Inverted Range • Verified the effectiveness of the signal structure and the ability to navigate (~5 Meters) • Results available for the “Lonely Halls” Meeting in September 1973. 10/22/09 Stanford CPNT October 2009 20 The Eras of Satellite Navigation 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 Pioneers -Transit Competition • 1st Oper. Sys. / Transit (Jan 1964-1996) • New Systems Proposed (mid 1960’s) • 621B (USAF) • TIMATION (NAVY) 10/22/09 Stanford CPNT October 2009 21 • Original Purpose: Quartz clocks in space for long-distance time transfer – Orbiting clocks - initially quartz – Passive side/tone ranging/cw subcarriers • could be used for 2-D positioning with user atomic clock • Timation I - May 1967 – Gravity Gradient/12 watts! – 500 n.mi./ 400 MHz – Time transfer, Oct. 1967-Mar. 1968 – Commercial double oven quartz • Timation II - Sept. ’69 – 150 and 400 MHz – 4 oven quartz – Radiation induced a high aging rate • Timation IIIA- Quartz and Rubidium - July ’74 – Renamed NTS - I - (Rb failed after about a year) • NTS - II Technology support for GPS 10/22/09 Stanford CPNT October 2009 22 The Eras of Satellite Navigation 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 Pioneers -Transit Competition • 1st Oper. Sys. / Transit (Jan 1964-1996) • New Systems Proposed (mid 1960’s) • 621B (USAF) • TIMATION (NAVY) • UPGRADED TRANSIT (NAVY) • “Joint” Program Office (JPO) 1972 - Director, Col. Parkinson • “GPS” System Defined/ Labor Day 1973 10/22/09 Stanford CPNT October 2009 23 The GPS Era - Initial Chronology Two “Lucky Failures” • LGen Ken Schlutz asks Col Parkinson if he would like to dance (the 621B Fox Trot) November 1972 – Answer: Would volunteer, only if I can lead – result instant dance lessons - LF #1 • LGen Schultz suggests Dr. Currie (DDR&E) would enjoy spending the afternoon with Col Parkinson Spring 1973 – Dr. Currie becomes a champion of the cause – Protection against the Air Force reluctance – A direct, informal line between Col Parkinson and Dr. Currie • The then-current 621B proposal did not gain approval in August 1973 LF#2 • I called a small meeting to modify the proposal… 10/22/09 Stanford CPNT October 2009 24 The Pentagon “Lonely Halls” System Design Meeting • Labor Day Weekend – September 1-3, 1973 • Only JPO/Aerospace in Attendance (~12 attendees) – Attendees included: Col Brad Parkinson, Maj Gaylord Green, Maj Mel Birnbaum • Result: – Confirmation of Fundamental 621B concept • Selection of USAF/621B Signal structure • But direct to Space-hardened Atomic Clocks (Advocated by 621B and Timation – actively pursued by Timation/NRL) • 4 Space Vehicles - Orbits modified to Inclined (Major Gaylord Green) – Not the NRL orbits – 11H 58.03M - Sidereal Semi -Synchronous (stable test area – Yuma) • Prepared Decision Coordinating Paper (DCP-133) • Approval to proceed – 22 December 1973 10/22/09 Stanford CPNT October 2009 25 Details of the evolved JPO concept - Refinement of the 1966 621B System Concept • USAF/621B signal structure (PRN code) • USAF 621B User equipment integration concepts – especially Anti Jam The new synthesis had answers to all the issues, • Inclined Maj Gaylord Green orbits (11H 58M period) but was a “go for broke” approach • EvolvedCommitted Transit orbit to Hardeneddetermination/predictions Atomic Clocks • Atomic ClocksAnd on Worldwide Spacecraft Deployment (Advocated by both 621B and NRL, Advanced development by NRL) • Evolutionary test concept based on 621B (the ”Inverted Range”) • A family of tailored user equipment (Manpack, Lo-cost, Multichannel) •