PULSE REPETITION RATE OPTMIZATION IN SLR STATIONS TO PULSE REPETITION RATE OPTMIZATION IN SLR STATIONS TO PROVIDE MINIMUM SYSTEMATIC ERROR OF RANGINGPROVIDE MINIMUM SYSTEMATIC ERROR OF RANGING

M.A. SadovnikovM.A. SadovnikovInstitute for Precision Instrument EngineeringInstitute for Precision Instrument Engineering

MoscowMoscow

1616thth International Laser Ranging Workshop Poznan 2008 International Laser Ranging Workshop Poznan 2008

Active 300 Hz SLR stations. What next ?

INITIAL THESESINITIAL THESES

1.1. In single-photon SLR, the random and systematic errors of return signal arrival In single-photon SLR, the random and systematic errors of return signal arrival time depend on the number of photoelectrons in the return signal pulsetime depend on the number of photoelectrons in the return signal pulse nnsese..

2.2. With nWith nsese>1, the one-shot precision increases, but simultaneously the >1, the one-shot precision increases, but simultaneously the

systematic error of measurement also increases; the error is caused by systematic error of measurement also increases; the error is caused by variations of the moment of detection of the first photoelectron in the return variations of the moment of detection of the first photoelectron in the return pulse, as well as by variations of the signal transit time in the avalanche pulse, as well as by variations of the signal transit time in the avalanche photodiode.photodiode.

3.3. To eliminate the systematic error, it is necessary to provide nTo eliminate the systematic error, it is necessary to provide nsese<<1 in <<1 in

combination with a high repetition rate of radiated laser pulses.combination with a high repetition rate of radiated laser pulses.

4.4. Using a simple analytical model of detection of return pulses with a fluctuating Using a simple analytical model of detection of return pulses with a fluctuating number of photoelectrons, it is possible to estimate the nnumber of photoelectrons, it is possible to estimate the nsese value and value and

corresponding repetition rate F required for a given (sufficiently low) systematic corresponding repetition rate F required for a given (sufficiently low) systematic error level.error level.

ANALYSIS RESULTS AND CONCLUSIONSANALYSIS RESULTS AND CONCLUSIONS

1.1. The effect of signal intensity fluctuations on the systematic error of range The effect of signal intensity fluctuations on the systematic error of range measurements decreases with reduced average number of photoelectrons in the measurements decreases with reduced average number of photoelectrons in the return signal pulse. With nreturn signal pulse. With nsese<0.05, the intensity fluctuations actually do not affect <0.05, the intensity fluctuations actually do not affect

the measurement accuracy.the measurement accuracy.

2.2. WithWith nnsese<0.02, the systematic error of range measurements does not exceed <0.02, the systematic error of range measurements does not exceed

0.30.3 mm, with return signal pulsewidth less than mm, with return signal pulsewidth less than 400 400 psps..

3.3. WithWith nnsese<0.05, the systematic error of range measurements does not exceed <0.05, the systematic error of range measurements does not exceed

0.0.6 mm, with return signal pulsewidth less than6 mm, with return signal pulsewidth less than 400 400 psps..

4.4. To eliminate the systematic error, the laser pulse repetition rate should meet the To eliminate the systematic error, the laser pulse repetition rate should meet the requirement requirement F>fF>fsese/n/nsese, , where where ffsese is the mean value of return signal photoelectron is the mean value of return signal photoelectron

generation frequency in the SLR station receiver.generation frequency in the SLR station receiver.

5.5. To obtain To obtain ffsese values typical for state-of-the-art SLR stations, the laser pulse values typical for state-of-the-art SLR stations, the laser pulse

repetition frequency should be in the tens of kHz range.repetition frequency should be in the tens of kHz range.