Parc Kennedy - Bat A , Rue Gilles Roberval / F NIMES  +33 (0) /  +33 (0) / Web : FOGALE Nanotech Solutions for Metrology and Control of Telescopes

FOGALE Nanotech FOGALE Nanotech, a company created in 1983 by researchers, is now an authority in the field of fast and precise measurements. With partners as prestigious as ONERA, LNE, ESRF, CERN and several industry leaders, we have developed a complete family of equipments and products dedicated to non-contact and remote technology; several of these products are protected by international patents. The strength of our experience and our multidisciplinarity team combine to bring you standard or tailored solution which are comprehensive and utilise engineering and computer science to meet all your implementation and usage requirements. Our capability is now proven in the most demanding applications of industries and laboratories (automobile, aeronautics, armaments, nuclear and heavy industries, synchrotrons, accelerators…) in France, in Europe as well in the United States and Japan.

Examples for telescopes applications Optical technology Optical distances and thickness measurements Application example : focus determination in the SALT Capacitive technology Capacitance-based technology Some examples of applications - High resolution sensors - Tip Tilt control of adaptative optic - Tip Tilt control of image stabilizer - Measuring system of wind buffeting of the VLT 8.2 primary mirror - Alignment system of coude rotating platform - The VLT delay line rails alignment system Measuring Tip, Tilt, Piston, Gap and GRoC for segmented mirror

Measurement principle ground guard electrode target Capacitance-based technology Several possibilities for the sensor design : metal/resin technology, different shapes, serigraphy... Non-contact Rapidity Very high resolution Accuracy Any type of electrically conductive target (universal calibration) Good resistance to extreme conditions (temperature, radiation, magnetic fields, cryogeny) Special solutions Standard solutions Low cost solutions C =  r  S d

Tip Tilt Control of Adaptative Optic In collaboration with Paris-Meudon Observatory Servo-control system Non contact magnetic actuators Mesurement range : Bandwidth : Mirror diameter : 400 arc second 138 mm From 0 up to 400 Hz Resolution : < 0.05 arc second Mesurement range : Resolution : Deformable mirror diameter : 500 arc second < 0.05 arc second 180 mm Bandwidth : From 0 up to 100 Hz Sensor range : Sensor noise : Sensor diameter : From 0 to 500 µm 0.17 nm/Hz 1/2 10 mm Gemini ALTAIR VLT NAOS VLTI MACAO

Tip Tilt Control of Image Stabilizer In collaboration with Paris-Meudon Observatory Servo-control system Non contact magnetic actuators Mesurement range : Bandwidth : Mirror diameter : +/- 1 ° 480 mm From 0 up to 50 Hz Resolution : < 1 arc second CFH MEGACAM

Measuring system of the wind buffeting of the VLT 8.2 primary mirror Mesurement range : Bandwidth : +/- 0.5 mm From 0 up to 20 Hz Resolution : < 5 nm

Alignment system of the coude rotating platform Accuracy :  5 µm Diameter : 5.1m

The VLT delay line rails alignment system HLS WPSTMS The solution for alignment of the carriage of the delay line is based on the use of a stretched wire and a water level system that materialise the reference Length 66 m, accuracy : 15 µm/m

Measuring Tip, Tilt, Piston, Gap and GRoC for segmented mirror Edge sensors based concept System mounting Southern African Large Telescope example for the Segment Alignment Measurement System : - Schematic of measurement and processing chain example - Some specifications of the capacitance chain example

Edge sensors based concept Measurement of Tip, Tilt, Piston, Gap and GRoC by Capacitive Edge Sensors Two plates of sensors parallel with edge of segments : 1 transmitter plate 1 receiver plate Sensors are under or between segments (low cost and low mass solution) High resolution and stability Possible remote electronics (no heat dissipation near segments) Edge sensors under the Segments Edge sensors between the Segments Multi electrode sensor : measure directly the capacitances Cost effective technology

to PC I/O board Connector for 3 edge sensors Numerical module 1 shielded cable l = 20 m Igloo Max 8 capacitive modules (3 channels by module) Small coaxial connectors Mirror segment Measurement near the mirror surface No heat dissipation near segment High stability (sensor sticked on segment) 3x8 channels rack with numerical module Plate sensors x y z 19 ’’ 3U Rack Mirror surface System mounting Measurement of Tip, Tilt, Piston, Gap and GRoC by Capacitive Edge Sensors

Mini-connectors (coaxial) Mini-cable (coaxial / low noise) Connection box Principal cable (multi coaxial) Length up to 20m Transmitter plates Receiver plates Mirror surface Igloo Rack 19’’ 3U Module To PC Primary mirror Schematic of measurement and processing chain example for SALT Measurement of Tip, Tilt, Piston, Gap and GRoC by Capacitive Edge Sensors

Some specifications of the capacitance chain example for SALT Measurement of Tip, Tilt, Piston, Gap and GRoC by Capacitive Edge Sensors SENSOR : between the Segments Transmitter plate : Plate dimension : 42 x 170 mm 2 Receiver plate : Plate dimension : 42 x 170 mm 2 Sensor gap : From 6 to 25 mm Sensibility on Z axis : 14 pF/m Sensibility on Y axis : 11 pF/m ELECTRONICS : Electronics measurement noise on Z axis : < 30 nm/Hz 1/2 Electronics measurement noise on Y axis : < 40 nm/Hz 1/2 Range on Z axis : +/- 0.7 mm Range on Y axis : 6-25 mm Offset setting on Z axis : +/- 0.7 mm Output signal on Z axis : +/- 10 V Output signal on Y axis : 2-10 V Output resolution (ADC 16 bits) on Z axis : 0.4µm Output resolution (ADC 16 bits) on Y axis : 0.02µm Bandwidth : 0-20 Hz Electronic gain and offset drift on Z and Y axis : 10 ppm/°C Serial link : Ethernet TCP/IP Power supply : 115 or 230 V 24-channel 19’’3U rack Length of sensor to electronics cable : 20 m

Optic example for telescope applications Optical technology Optical distances and thickness measurements Application example : focus determination in the SALT

– Interference Peaks when optical paths L m = L r – Measurement of absolute distance X from an internal ultrastable reference position. Low-Coherence Interferometry – Principle : – Low-coherence source (SLD) – High-accuracy scanner with reference mirror istances and thickness measurements Optical technology Distances and thickness measurements

Applications : – Distance and thickness measurements in laboratory and industrial environments Fiber optics design – Adaptable to several measurement configurations OCT Industrial system Optical distances and thickness measurements OCT Industrial system Compensation of propagation and thermal effects for high-accuracy applications Specifications – Absolute accuracy : Down to +/- 0.5 µm – Measuring Range : up to 400 mm – Distance of measurement : up to several meters

SAC Primary mirror Control Unit Collimator Fiber Link Measurement of the distance between the spherical aberration corrector (SAC) and the primary mirror to maintain the focus of the telescope Application example : Focus determination in the SALT Distance = 13 m Range = 40 mm Accuracy = 10 µm