1. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 SPACE SITUATIONAL AWARENESS PROGRAMME P2-SST-VII EXPERT COORDINATION CENTRES (PHASE 1) Contribution of Czech Technical University in Prague Ivan Procházka, Josef Blažej presented at KOM, Darmstadt, April 14, 2016 Czech Technical University in Prague, 119 19 Prague 1, Czech Republic

2. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 Outline - CTU Contribution n Description of bi - and multi - static laser ranging of space debris and related calibration constants n Signal propagation delays – transmitting part explanation and possible calibration procedure n Signal propagation delays – receiving part explanation and possible calibration procedure n Hw and sw required for new calibration procedure n Calibration of European SLR sites for bi- and multi – static laser tracking of space debris n Summary and Conclusion

3. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 n SLR is a technique to measure the distance as a function of time. To calibrate the SLR the optical signal propagation time is determined as a single value by ranging to a ground target of known distance. n In bi- and multi - static laser ranging to space objects the system biases are strictly separated into transmitting and receiving channels. n In addition to it the relations of the epochs of transmission and reception have to be referred to the coordinated time scale UTC with the accuracy reaching one nanosecond level or better. C.Baman et al, The Importance of Clock Synchronization in Multi-static Laser Ranging Scenarios for Orbit Improvement of Space Debris, ILRS Workshop, Matera, 2015 n This requirement is about one hundred times more accurate (!) than in standard SLR applications. n That is why a new signal delays calibration technique has to be developed, tested and applied Standard SLR versus bi- and multi-static Laser Ranging to Space Object

4. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 Signals propagation delays – transmitting n GROUND SEGMENT DT1,2 optical path length n DT3 photodiode BW, delay n DT4 cable delay n ET timing system, BW, delay n Difficult to determine most parts individually n Satellite Laser Ranging (SLR) n all contributors replaced by a single parameter. n calibrated via reference ground target ranging n routine technique, (sub) mm accuracy.

5. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 Signal delays calibration - Transmitting part n The transmitting delay will be calibrated individually for each participating SLR system n Calibration value computed from n - epoch dif. (E2-E1) - geometry distance L n Calibration Device HW needed Detector + Epoch timer + cables n High synergy with ELT European Laser Timing Epoch E1 recorded using standard SLR part Epoch E2 recorded using Calibration Device Both systems will use common freq. and “1pps” & common 1pps cable

6. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 Calibration Device HW n Optical receiver head n Photon to electrical delay will be measured with ~15 ps accuracy n Signal cabling – low temp. drift cables n Delay will determined with ~ 2 ps accuracy n NPET timing system, sub-ps stability and linearity Prochazka I, et al, Metrologia 48 (2011) L13-L16 P. Panek, I.Prochazka, Rev. of Sci. Instruments, 78 (2007) L 78-81

7. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 Calibration Device demo Fundamental Station Wettzell, Germany n detector package in front of SLR telescope distance surveyed repeatedly (< +/- 1mm) n Event timing NPET n Epoch reference “1pps” connected consecutively to SLR and calibration timing systems using identical cable 20 ps RMS

8. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 Signal delays calibration - Receiving part n The receiving part will be calibrated individually for each participating SLR system n Calibration value will be computed from : - SLR standard calib. value - transmitting part calibration constant n No additional measurements and HW is needed

9. I.Prochazka,et al, KOM ESOC, Darmstadt, April 2016 Summary and Conclusion n For efficient implementation of bi - and multi - static laser ranging of space debris a new calibration procedures and constants are needed. n CTU in Prague will contribute to development, tests and implementation of new calibration techniques. n The necessary hw and sw will be developed and tested, high synergy to the laser time transfer project ELT will be considered without any negative impact on the original ELT project. n We are looking forward our common results !