Latest & future Evolutions. Atomic Clocks for. Global Navigation Satellites. Workshop H2020 Space' September 2016 Satellites Navigation

Transcription

1 Latest & future Evolutions on Atomic Clocks for Global Navigation Satellites Workshop H2020 Space' September 2016 Satellites Navigation

2 Presentation outline Standard GNSS RAFS space heritage Robust RAFS project goals, solutions & Results New Miniaturized Physics Package for Passive Maser On Board Clocks Ensemble (ONCLE) Mercury Ions Clock project Robust physical representation of the Galileo System Time 2 P.Rochat

3 RAFS Space Heritage: GSTB-V2 (ESA) 2 FM (Flight Model) GIOVE-A (ESA) 2 FM GIOVE-B (ESA) 2 FM COMPASS (China) 21 FM GAIA (ESA) 2 FM GALILEO IOV (ESA) 8 FM DFH (China) 13 FM IRNSS (India) 27 FM GALILEO FOC (EU) 44 FM Total RAFS FM Delivered: 121 units (77 flying on 40 satellites ) 3

4 On board Clocks and GNSS Programs IRNSS Rubidium Cesium Cesium Rubidium? Hydrogen Maser Rubidium Rubidium Rubidium (1) Rubidium (2) Rubidium 4

5 RAFS latest improvements Removal of frequency discontinuity observed in original design (frequency jumps of several few times a year) Improvement of the drift predictability over several days Compatibility with IOV/FOC satellite I/F as far as possible (electrical, mechanical and thermal) Improved robustness by taking into account flight experiences 3.3 kg 5

6 RAFS latest improvements Results (II) Improvement of the drift predictability over several days GIOVE-A RAFS as per ESA document SP-1320 (end of year 2008) R-RAFS October 2014 to February

7 RAFS latest improvements Results (IV) 7

8 On the Maser side :

9 Passive Hydrogen Maser Mini Maser Physics Package PP GALILEO : ~12100g PP MINI PHM : ~ 8080g Gain: 4020g (33%) Qualification status: on going according to Galileo requirements along with EP& Integration by Leonardo (IT) Risks: Minimum tech risks because uses same material & processes as already flying on Galileo satellites 9

10 Mini-PHM EQM PP model stability test Dimensions Mass Frequency Drift (/Day) 179 x 465 x 175mm 8Kg 1*10-15 /day 10

11 On-board Clock Ensemble Functionalities, tasks & priorities

12 Tasks & Priorities 1. More stable and accurate on board clocks induce more complexity and therefore lower reliability figure. 2. An ensemble of lower stability clocks can lead to higher performances than single clock with dramatically improved reliability figure. 3. Real-time detection of clock feared events (hard fault, frequency jump, Noise / Signal level increase) allowing isolation or correction of unhealthy clock to improve availability of timing system. 4. Generation of output signal from an ensemble of clocks to improve output frequency stability performance. To be robust and implementable in onboard FPGA

13 B. One CLock Ensemble (ONCLE) Ensemble generation: weighted (or simple) average of clocks fout N i1 i f i Pout N i1 ip i N i1 1 Reliable i fout Test results RAFS clocks Pout Ensemble output Clocks with same level of performance: f stability imp. 1 N, f drift average. Mixture of clock technologies: high weighting to high-performance clock to assure high-performance of CMCU+ output.

14 Way forward : A simple and robust solution to improve availability, continuity and performances of the onboard timing system On going activity : Airbus DS & Spectratime working together to convert the CMCU into CMCU+ with following features : CMCU+ will have 6 clocks inputs instead of 4 CMCU+ can operate 100% like CMCU CMCU+ will contain ONCLE functionalities CMCU+ is capable of frequency & phase jumps detection & correction CMCU+ can automatically remove bad clock from the ensemble.

15 MIFS (Mercury Ion Frequency Standard) TRL-3 (ESA TRP) TRL-7 (JPL-NASA) Low magnetic sensitivity No wall collision High Q atomic line Low frequency drift Low temperature sensitivity 15

16 Principle of the MIFS clock: frequency discriminator Clock ion 199 Hg + with microwave clock transition 40,507,347,996.8 Hz Optical pumping towards lower clock level with plasma lamp ( 202 Hg + ) Scan microwave radiation across clock transition Monitor peak in the fluorescence from the ion cloud Atomic Line Q is 25 time better than Maser technology!!! ion cloud 16

17 MIFS Technology assessment ESA TRP = TRL 3 ESA GSTP 6.1 = TRL 4/5 ( ) Parameter Clock Technology Unit PHM R_RAFS MIFS ADEV@1s - < 1E-12 3E-12 < 1E-12 ADEV@1d - < 5E-15 1E-14 < 5E-15 Frequency drift 1/day <1E-15 1E-13 < 1E-15 Magnetic sensitivity 1/G < 3E-13 1E-13 < 1E-14 Thermal sensitivity 1/ C < 3E-14 2E-14 < 1E-15 Volume litre < 5 Mass kg < 5 Power W 60 < 35 < 30 Lifetime years 12 > 15 > 15 Time to 1 ns error days 2 to

18 RCE : Robust Clock Ensemble on ground Precise Timing Facility (PTF) of Galileo GMS RCE Anomaly clock Det. Algorithm AHM: physical realization of GST short-term stability required for navigation R. Zanello, et al, Implementation and On-Site activities of Galileo Precise Timing Facility, EFTF2010. A. Proia, et al, First performance results of the Galileo Precise Timing Facility, ION PTTI 2013.

19 C3. Frequency jump detection and compensation - 3 Example 2. Freq. jump of 1e-14: det. & comp. in 1470s Freq output of PI filter w/o compensation Compensated Technique verified by testing on EBB of robust On-board FRS

20 Thanks for your attention Contact information: (MD) Special thanks to SSO for their 25 years Continuous support on Navigation Clocks development 20