Nibbles. Professor Brad Parkinson Stanford University

Transcription

1 Nibbles SCPNT B. Parkinson

2 Nibbles Professor Brad Parkinson Stanford University Nibbles SCPNT B. Parkinson

3 Three EssenAal ACributes for any GNSS: the Three A's. Availability (Metric- minutes of unavailability per day) Geometry Clear RecepAon Affordability Metrics: Total AmorAzed cost per satellite- year (on orbit) Cost of User Equipment (interference resistance) Accuracy Metrics: PNT 2σ, Inaccuracy bound (3 or 4σ or 10-7 ), Probability that PNT Safety of Life value is exceeded ( integrity ) Geometry Ranging Accuracy Geometric (un)availability is strongly dictated by number of slots in GPS ConstellaAon 3

4 Geometric Availability: First Measure of EffecAveness (Unavailability of GPS due to ConstellaAon size and Moderate Terrain or obstrucaons) Moderate Mountain Slope or small Total town outages of 2 to five hours with 24 slots Total outages are negligible with 33 slots The Message: Require at least a 30 slot constellaaon for reasonable availability for a sky- impaired GPS user in typical small town or mountain terrain (and possibly on airports near buildings) 4

5 First Measure of EffecAveness (Unavailability of GPS due to ConstellaAon size and Steeper Terrain) Fairly rugged Mountain Slope Total outages of 6 to 10 hours with 24 GPS slots Total outages are manageable with 33 GPS slots The Message: A 33 slot constella4on is required for reasonable availability when user is sky impaired in ciaes or rugged terrain 5

6 Affordability and Geometric Availability Co- Dependency $ Affordability # of Satellites Simplis9c Math If: Cost/Sat = C SAT+LAUNCH Then ~ #/Year = (Budget/Year)/C Or (#/Year) * C ~ Constant 6

7 First set of Nibbles (aim for 33+X): Guidelines 15 to 18 Full- up Satellites The Nibbles: 15 to 18 GPS only Satellites, (all NavigaAon signals no surge power) Goal Greatly Reduced Cost per Satellite year on- orbit Approach: Nibble at Satellite Weight, Complexity and Power Directly Reduce Sat Mfg. Cost Enable Triple or Quadruple Launch Reduce on- orbit cost by at least 50% Enable Affordable 33 Satellite ConstellaAon Result: greatly enhanced Geometric Availability for users 7

8 Nibbles Satellite SWaP Design Architecture Only addiaonal payload is Laser Reflector Smaller Commercial Bus Power Requirements (Current Payload ~2200W) Shading Angle Spec 5o changed to 20o With affordable 30+X, many Satellites above 20 degrees Reduce Satellite antenna complexity (12 to 4 Elements?) Total Power reduced ~ 0.6 db Spec RF Power at 20o reduced by 1.5dB Total reducaon 40% (2.1dB) RF Power Conversion Efficiency Convert from GaAs (25-30%) to GaN (35-50%) or TWTAs (50-65%) Nibbles SCPNT B. Parkinson

9 Solar Array Power for Various Amplifier Efficiencies- (η PA ) DC Power Required (WaCs) DC Power = (RF Power)/η PA Current Designs at ~500W RF Nibbled Designs at 300W RF GaAs GaN TWTA RF Power Nibbles Amplifier SCPNT B. Parkinson Efficiency 2012 η PA 9

10 Nibbles can greatly reduce the Satellite Heat RejecAon Requirement Heat RejecAon Required (WaCs) GaAs Heat RejecAon Required = (RF Power) *(1- η PA )/η PA Current Designs at 500W RF GaN TWTA Nibbled Designs at 300W RF RF Power Nibbles Amplifier SCPNT B. Parkinson Efficiency 2012 η PA 10

11 Nibbles Satellite SWaP Design Architecture Only addiaonal payload is Laser Reflector Smaller Commercial Bus Power Requirements (Current Payload ~2200W) Shading Angle Spec 5o changed to 20o With affordable 30+X, many Satellites above 20 degrees Reduce Satellite antenna complexity (12 to 4 Elements?) Total Power reduced ~ 0.6 db Spec RF Power at 20o reduced by 1.5dB Total reducaon 40% (2.1dB) Power Efficiency Convert from GaAs (30%) to GaN or TWTAs AddiAonal Nibbles Lithium Ion BaCeries State of Art Solar Array Efficiency Power ReducAon leads to ProporAonate Overhead ReducAons BaCery Size EOL Reserves for Solar Array S/A Failure Reserves and Design Margin Nibbles SCPNT B. Parkinson

12 CauAons and Decisions Must Maximize use of exisang designs and components Some overhead is hard to shrink TWTA s Subtle consequences for a Nav Ranging Signal? Degrees of Hardening Redundancy (Design Life) 12

13 Es9mated Value of Nibbles (All in Brad $, exact exchange rates to US$, Euros or Yen not determined) Type Satellite Cost (AmorFzed) Sats/ Booster Booster Cost C Cost of Sat on Orbit ~Number of Sats for $500M/yr Current $220M 1 $230M $450M ~ 1 $60M 2 $200M $160M 3 Nibbled $55M 3 $210M $125M 4 $50M 4 $240M $110M Almost 5 13

14 What about the small reducaon in Radiated power with nibbled Satellite? Availability (Metric- minutes of unavailability per day) Geometry Clear RecepFon Affordability Metrics: Leads to Nibbles Part 2 Total AmorAzed cost per satellite- year (on orbit) Cost of User Equipment (interference resistance) Accuracy Metrics: PNT 2σ, Inaccuracy bound (3σ), Probability that PNT Safety of Life value is exceeded ( integrity ) Geometry Ranging Accuracy 14

15 GPS RECEIVER ANTIJAM CAPABILITY (db) Payoff of Jamming jammer ineffecave Resistance to Current: 1 WaC EffecAve to 2 to 5 Kilometers 100 mw 10 mw 1 mw JAMMER ERP = 0.1 mw Desired: A 1kW Aircra flying overhead at 7000 Feet 10 W W 100 W 1 kw 10 kw NEEDED: About 35 db of Additional Receiver Interference Resistance (From Processing, signal, receiver & antenna) JAMMER Maximum Effective Range (km) 15

16 Nibbles Part 2 - Jam Resistance How to get > 35 db of Improved Receiver Performance for Commercial Aircra@ Technique Aircra Shading InerAal And Averaging (MEMS, CSAC, Kasovich Devices) Wider Spreading GNSS Signal (e.g. L1C) Digital Beam Forming Antenna Spilker Vector Receiver (A powerful form of frequency diversity) Range of improvement 5-10 db 8-12 db 5 db db At least 10 db PotenFal Total Improvement db In addifon A credible reliable backup should be included: Recommended Either Retained (selected) DME or eloran 16

17 Payoff of Jamming Resistance GPS RECEIVER ANTIJAM CAPABILITY (db) PotenAal Nibbles CumulaAvely Produce 95 db or more of Interference Resistance 100 mw 10 mw 1 mw JAMMER ERP = 0.1 mw 10 W W 100 W 1 kw 10 kw Digital Technology is making beam steering and vector receivers much more affordable Believe This is a trend that will continue JAMMER Maximum Effective Range (km) 17

18 Nibbles Part 2 ConsideraAons for Receiver improvements Affordability Safety of Life - vastly different Threshold of $ Pain Synergy with WB Aircra Antenna InerAal PoinAng Expanded market drives down cost (cell phone camera) FAA Role push for receiver Interference Resistance Specs Industry Role Prototype and Develop Robust Receivers 18

19 Summary Nibbling to improve the Three EssenAal ACributes Availability (Metric- minutes of unavailability per day) Deploy ~ ½ Nibbled Satellites for 30+X constellafon Focus on Nibbled Technology for Receivers Affordability Metrics: Nibble on size weight and power to insure mulfple- Launch, Affordable Satellites Ride Digital Wave for Beam Steering plus Vector Receiver Accuracy Metrics: PNT 2σ, Inaccuracy bound (3σ), Probability that PNT Safety of Life value is exceeded ( integrity ) Affordability leads to Improved Geometry (Esp. Sky Impaired users) MulAple Frequencies and L1C Improves Ranging Accuracy Nibbles SCPNT B. Parkinson

20 Questions? Nibbles SCPNT B. Parkinson