Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 1 Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas Metrology system PM# July 2006

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 2 THERMAL METROLOGY General assumption in prototype: - IN THE ACU AN OLD CONCEPT OF THERMAL METROLOGY WAS IMPLEMENTED: WITH THIS OLD CONCEPT THE POSITION OF THE SENSORS PUTTED IN THE BASE STRUCTURE WAS CONSIDERED IN A WRONG WAY - THE ACU SOFTWARE WAS CORRECTED AND UPDATED - THE CORRISPONDENCE BETWEEN THE PHYSICAL SENSORS AND THE ROWS OF THE MATRIX WAS WRONG: SOME SENSORS IN THE RIGHT ARM WAS READ BY ACU AS THEY WERE IN THE LEFT ARM - ALL THE SENSORS WERE CHECKED AND NOW THEY ARE READ BY ACU IN THEIR CORRECT POSITION - THE POINTING MODEL GIVE A POINTING ERROR GREATER THAN THE ERROR DUE TO THERMAL DISTORSION OTHER PROBLEMS -THE CORRECTION DUE TO THERMAL METROLOGY SEEMS TO GO IN THE WRONG DIRECTION -BY POINTING POLARIS AND BY TRYING TO TRACK, AFTER A FEW TIME (i.e. 1 hour) YOU CAN SEE A POINTING ERROR AND IF WE TURN ON THERMAL METROLOGY, THE ERROR INCREASE -AFTER SOME EVALUATIONS AND SOME CHECKS, WE FOUND THAT THE CORRECTION OF THERMAL METROLOGY IS IN THE CORRECT DIRECTION -WE PUTTED THE ANTENNA WITH THE REAR FACING TO THE SUN, SO THE ANTENNA BEND ITSELF AND POINT LOWER. AFTER A FEW TIME WE TURNED ON THE METROLOGY AND THE ELEVATION CORRECTION WAS IN THE RIGHT DIRECTION

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 3 THERMAL METROLOGY PROBLEM -THE POINTING MODEL WAS VERY OLD AND GIVE AN ERROR BIGGER THAN THE THERMAL ERROR POSITION AFTER 1 hour WITH A CORRECT POINTING MODEL POSITION AFTER 1 hour = ERROR DUE TO POINTING MODEL + ERROR DUE TO THERMAL STARTING POSITION POSITION AFTER 1 hour WITH METROLOGY TURNED ON POSITION AFTER 1 hour WITH A CORRECT POINTING MODEL AND METROLOGY TURNED ON = ERROR DUE TO THERMAL = ERROR DUE TO POINTING MODEL

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 4 THERMAL METROLOGY PROBLEM THE RESOLUTION OF THE OPT SYSTEM IS NOT GOOD, ONLY AN EXTIMATION OF THE ENTITY OF THE POINTING ERROR IS POSSIBLE MONITOR OF THE OPTICAL TELESCOPE 1 cm = ABOUT 30 arcsec POINTING ERROR TO CORRECT: 0.6 arcsec

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 5 THERMAL METROLOGY GENERAL ASSUMPTIONS FOR PRODUCTION: -New concept based on 78 thermal sensor (TBD). (18 in the base structure, 60 in the Yoke base and arms) -There are additional 4 sensors in the Apex cylinder interface. - Consolidated FEA model ready for optimization of position and numbers of thermal sensors -If possible in the prototype the system must be tested after the pointing model implementation in order to have evidence about the level of correction

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 6 WIND METROLOGY General assumptions from prototype: -The dynamic behaviour of the titlmeter in the top arm is not good for Fast switching motion -After a fast accelleration the system need 20’ of settling time -There is evidence of the hysteresys link to the azimuth bearing -We need to improve the control system link to the actual azimuth encoder signal (at the hight elevations) What we need to correct with the dynamic metrology?

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 7  Error Budget Calculation without metrology correction: Pointing Error Offset Pointing error Absolute Pointing Error Pathlenght error

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 8 Fast Motion mode: Step response with maximal acceleration

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 9 Fast Motion mode: On the fly Mosaiking mode

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 10 Tracking mode: Maximal elevation tracking velocity.

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 11 Tracking mode: test on the repeatability position.

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 12 PULL TEST OF THE RIGHT ARM LOAD APPLIED: N WITH STEPS EVERY 1000 N (LOAD AND UNLOAD) APPLICATION POINT: TOP ARM RIGHT (Z = 700mm BELOW ELEVATION AXIS) CONSTRAINT POINT TO GROUND: X = +20m FROM AZIMUTH AXIS Z = 500mm ABOVE GROUND LOAD APPLIED BY ONE TIRFOR (MANUAL) MEASURE WITH ONE DYNAMOMETER 1000 samples a 1/100s (decimation 9)

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 13 PULL TEST OF THE RIGHT ARM TILTMETER POSITIONED ON THE TOP ARM RIGHT

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 14 PULL TEST OF THE RIGHT ARM PULL IN DIRECTION +X ANSYS RESULTS: ROTY = 0.264E-04 rad = 5.45 arcsec MEASURED VALUES ON THE TILTMETERi ArmTiltX_arcsec_vs_kg = e-3 ArmTiltY_arcsec_vs_kg = e-3 YokeTiltX_arcsec_vs_kg = -6.96e-5 YokeTiltY_arcsec_vs_kg = e-3 Vectorial sum ArmTilt in direction Xyoketilt=-8.719e-4 Vectorial sum ArmTilt in direction Yyoketilt=-4.676e-3 REAL ANTENNA IS 16.6% MORE STIFF THAN ANSYS MODEL

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 15 PULL TEST OF THE RIGHT ARM PULL IN DIRECTION -Y ANSYS RESULTS: ROTY = E-04 rad = arcsec MEASURED VALUES ON THE TILTMETERi ArmTiltX_arcsec_vs_kg = e-3 ArmTiltY_arcsec_vs_kg = e-3 YokeTiltX_arcsec_vs_kg = e-3 YokeTiltY_arcsec_vs_kg = e-4 Vectorial sum ArmTilt in direction Xyoketilt=-2.513e-3 Vectorial sum ArmTilt in direction Yyoketilt=-5.199e-4 REAL ANTENNA IS 6.6% MORE STIFF THAN ANSYS MODEL

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 16 WIND METROLOGY General assumption for the production: -The new concept is based on two titlmeter mounted on the top arms (we need this two titlmeter also for the requiremets of the realignment) -We are working with the Geomechanics in order to improve the dynamic behaviour of the titlmeters -We are working with the control system in oreder to eliminate dynamical problem w.r.t encoder system, drive system, others source of noise. We have to work in order to check only the error source that we need to correct: -Steady wind up to 6,5m/sec -Fast motion mode (see TM)