icso 20101 high accuracy laser telemetry for kilometric distance measurement in space c.courde, h....
TRANSCRIPT
ICSO 2010 1
High Accuracy Laser Telemetry for Kilometric Distance Measurement in Space
C.COURDE, H. PHUNG Duy, M. LINTZ, A. BRILLET
ARTEMIS, Observatoire de la Côte d'AzurCNRS et Univ. Nice-Sophia Antipolis
06300 NICE
ICSO 2010 22
Objectives
Absolute long distance measurement (~km) in vacuum with high accuracy
For :– Formation Flying telescope
(Darwin (30µm of accuracy))– Alignement and monitoring of
large structure (particle colliders or radio telescope)
DARWIN
Our goal
Range : ~ 1km
Accuracy : < 1µm
Resolution: ~nm
ICSO 2010 3
Outline
I. T2M telemeter• Principle• Results
II. Iliade telemeter• Principle• Results
ICSO 2010 44
I. T2M Principle
)(.)(.)(tF
cKtKtL 1
1 ..F
cKKL
22 ).1().1(
F
cKKL 12
1
FF
FK
t
Δref/meslocked at 0
mes
ref
Λ
Calibration with K integer and c the speed of light
Amplitude Modulated beam
Λ=c/F
Synthetic wavelength
Reference path
Measurement path
Δref/mes
Adjustable frequency F
Accuracy limited by phase drifts and cyclic errors
Robust and simple system
Corner cube
ICSO 2010 55
I. T2M PrincipleElimination of systematic errors
Amplitude modulated beam
Λ=c/F
Synthetic wavelength
Reference path
Measurement path
Δ
Adjustable frequency F
PHD1 PHD2
Crosstalk
Cyclic errors are suppressed with the optical switching
system
Unbiased zero of phase difference
Exchange of the beams between the two photodiodes
Corner cube
Optical switching system
ICSO 2010 66
Frequency-meter
VCO13GHz
PHD
ASE SOURCE1.55 µm
Fibered PBS
2 kHzswitch
LI-A Telemetric lock
Optical isolator
Polarization controller 2
PBS cube
Corner cubes
Mixer HF
phase-meter
Δφ
refmeasure
Telemetric signal
I. T2M Principle
Lock-in Amplifier
Polarization controller 1
Amplitude modulator
DISTANCE
Optical switching
system
HF
ICSO 2010 7
I. T2M resultsAllan deviation of the Telemetric signal
in open loop with a broadband source (ASE)
Allan deviation < 20 nm for 5s < times < 2000s
Probably limited At short measurement times by intensity noise of the source
At long measurement times by systematic error
To identify parasitic interferences :
Broadband source+modulator is replaced by the beat note of two single mode lasers shifted by 13 GHz
10 nm
ICSO 2010 88
I. T2M characterizationSearching for optical interferences
Systematic errors !!!
4GHz
5µm
Manual master laser wavelength scan
2 different cavity effects
FSR 4GHz thickness 37mm
(vacuum) or 25mm (n=1.5)
FSR 270MHz thickness 56cm
(vacuum) or 37cm (n=1.5)
2µm2µm
Slow length scan
Telemetric signal
PBS cube
SOLUTION
Freq markers
- PBS cube changed for a thick polarization beam splitter at 45°
Manual master laser wavelength scan
Telemetric signal
Systematic errors lower than 1 µm
4GHz
Freq markers
ICSO 2010 9
II. Iliade principleCombining 3 levels of increasing sensitivity:
Time of flight measurement of optical pulses
=> Absolute distance measurement0.1 mm
15 mm 0.1 µm
Phase measurement of synthetic wavelength
=> relative distance measurement
1.55 µm0.1 nm
Phase measurement of optical wavelength
=> relative distance measurement
In PhD1
Synthetic angular frequency
Optical angular frequency
ICSO 2010 10
II. Iliade preliminary results
Simulation
Varying L, All parameters fixed
Experiment
« segment » for different positions with 0.5mm increments at a 1.5m Distance
Use of the interference figure :
Varying allows to cover the « segment » /2 c
Deviations of 3.10-3 peak-peak
Non-linearity in commercial oscilloscope used for data acquisition
ICSO 2010 11
Conclusion
– T2M• Simple system with accuracy fixed by the frequency
measurement• No optical stabilization• Systematic errors lower than 1 µm, to be confirmed• Stability below 20 nm for measurement times [5s,2000s]
– Iliade• Principle of the measurement is confirmed• Limitations in phase measurements and in amplitude
measurements caused by non linearity in the data acquisition system
ICSO 2010 12
Thanks toCNESANR
Thales Alenia Spacerégion PACA
and thank for your attention