Multi-Application Solar Telescope Preliminary results

Transcription

1 Preliminary results Shibu K. Mathew Udaipur Solar Observatory

2 Past Present Future Telescope specs. and components Installation Optical alignment and tests Back-end instruments Preliminary observations Adaptive optics implementation Regular G-Band and H-alpha observations Vector magnetic field imaging

3 Telescope specs. and components Salient features 50 cm off - axis design for reduced scattered light. Zerodur primary, secondary and Coude mirrors with SiC. /12 wave front error, around 0.25 arc-sec resolution at 600 nm. Alt-azimuth mount, image de-rotator for FOV rotation compensation. Active thermal control on M1 and all the other mirrors, maintained within ± 1 o C to the ambient. Collapsible dome, no trapped heat and thus no dome seeing. Hexapod mounted secondary mirror for active compensation of aberrations due to thermal flexure. Back-end instruments on a stable platform beneath the telescope floor

4 Telescope specs. and components Optical Design Primary mirror (M1) : Off-axis parabola, 2m focal length, surface figure (rms) /30, Zerodur. Secondary mirror (M2) : Off-axis parabola, 200 mm focal length, SiC, surface figure (rms) /40. Coudé Train (M3 - M5) : Plane mirrors, SiC,, surface figure (rms) /60. De-rotator Mirrors (DM1 DM3) : Plane mirrors, Zerodur,, surface figure (rms) /60. Folding Mirror (M6) : Plane mirror, Zerodur, provides light to the back-end instruments,, surface figure (rms) /60 M1 M3 M5 DM1 DM3 M4 DM2 M2 Output wave-front error better than /12 Collimated beam M6

5 Telescope specs. and components Mechanical design A stiff central structure connecting the two altitude shafts A reinforced strut structure to connect the central structure and M2 M2 is mounted on a hexapod with correction capabilities for tilt, decentring, and translation Support structure for the polarimeter package in the strut Specifications Differential pointing accuracy : 0.5 arc-sec Open loop tracking : 0.25 arc-sec for 10 min Closed loop tracking : 0.1 arc-sec for 1 Hr M2 mechanism : tip-tilt system

6 Telescope specs. and components Thermal design The tubes and the fork, are shaded from the sun s illumination by an upper sunshield system. The M1 mirror is thermally controlled by means of airflows with controlled temperature The primary mirror surface is kept at within 1 o C ambient Telescope Control System (TCS) Telescope Control System (TCS) software is written in LabView. PLC control for the thermal and pneumatic systems. UMAC controllers for the azimuth, elevation and de-rotator drives. The TCS can be accessed and the telescope can be controlled remotely over Ethernet.

7 Telescope Installation The entire telescope mechanical structure transported from AMOS in three pieces, the largest weighing more than 4 tonnes. The boxes were transported to the island (around 700m from the shore) on a large pontoon. Steel structure was erected for lifting the boxes from the lake to the building top.

8 Optical alignment and tests Both theodolite and Zygo interferometer are used for the optical alignment. Preliminary alignment of all the mirrors with respect to the telescope and optic axes using theodolite. A 60 cm flat mounted in front of the telescope and a Zygo interferometer are used for measuring wave-front errors. Secondary hexapod parameters were adjusted to minimize the errors in optical alignment of M1 & M2

9 Optical alignment and tests Tracking Tests Tests carried out using G-band observations. Sunspots tracked in 10 Hrs of data, in HG co-ordinate frame. Shift of the sunspot calculated by registering the mages. Maximum shift is with in 15 arc-sec for 10 Hrs, arc-sec/min

10 Telescope & Observing floor Telescope floor Telescope enclosed with in the collapsible dome Back-end instruments on the observing floor

11 CCD H-alpha Multi-Application Solar Telescope Back-end instruments Broad G-band and Narrow-band H-alpha imager CCD G-band G-band IF L1 Halle Filter BS

12 Back-end instruments Broad G-band imager Broad band interference filter 1nm passband 1376 x 1040 PCO Sensicam CCD 3 arc-min field-of-view Better than 10 images/sec temporal resolution Available for regular observations Narrow band H-alpha imager Narrow band Birefringent Halle filter 500 må band-pass 1024x1024 Photon Max CCD to cover 3arc-min Tuning capability, will be used for making Dopplergrams Better than 5 images/sec temporal resolution Available to make regular line-center observations

13 G-band and H-alpha sample images G-band, AR 12192, 22 October 2014

14 G-band and H-alpha sample images H-alpha, AR 12192, 22 October 2014

15 G-band and H-alpha sample images H full disk image constructed from a sequential mosaic of 293 images taken by MAST on 19 th May 2015.

16 G-band and H-alpha sample images G-band & H-alpha

17 G-band and H-alpha sample images G-band & H-alpha

18 G-band and H-alpha sample images AR 12436, 24 Oct 2015

19 Back-end instruments Fabry-Perot Narrow band imager for Magnetic field measurements Two voltage tunable lithium niobate FP etalons in tandem, resulting pass-band around nm Filter wheel with two or more pre-filters. Presently two wavelengths at nm and nm (FeI and CaII) for photospheric and chromospheric observations. The filters were tested using a Littrow spectrograph installed close to the imager

20 M1 From MAST M4 M5 Multi-Application Solar Telescope Back-end instruments Fabry-Perot Narrow band imager : voltage tuning Littrow Spectrograph FP1-3000V M2 M3 FP V FP1 FP2 FP2-3000V FP V

21 Back-end instruments Fabry-Perot Narrow band imager nm Pre-Filter FP1+FP2+Prefilter

22 Back-end instruments Fabry-Perot Narrow band imager; optical layout From MAST AO Components Pre-filter FP2 FP1 CCD Polarimeter

23 Back-end instruments Fabry-Perot Narrow band imager; typical tuning result: 22 Wavelength positions along the nm line profile with 15 ma steps

24 Back-end instruments Polarimeter 2 LCVRs and Linear polarizer (in degree) Fast axis of LC1, =0 (in degree) Fast axis of LC2, =45 Measured Intensity, I meas I 1 =I+Q/ 3+U/ 3+V/ I 2 =I+Q/ 3-U/ 3-V/ I 3 =I-Q/ 3-U/ 3+V/ I 4 =I-Q/ 3+U/ 3-V/ 3 (in degree) (in degree) Modulation Scheme I meas I 1 =I-V I 2 =I+V

25 Back-end instruments Polarimeter, initial results from I+V & I-V measurement o-65må I+V I-V V/I ~ o

26 Back-end instruments Polarimeter, initial results from I+V & I-V measurement

27 Back-end instruments Adaptive optics Deformable membrane mirror for the wave-front correction (MMDM), Schack Hartmann (SH) wavefront sensor. Tip-tilt mirror for the correction of image wobbling if any No. of actuators : 19, No. lenslets in SH: 19, Being integrated and tested with MAST Initial test results from the wave-front reconstruction. 19 lenlets are illuminated using the pupil light

28 Conclusion & Future plans MAST Installation completed. Telescope tested for wave-front accuracy and tracking errors. Presently, regular observations can be obtained in G-band and H-alpha. Integration of the back-end instruments are in progress. Narrow-band imager along with polarimeter are being used for test observations. Adaptive optics in the beginning of 2016.

29 Data products & SUIT connection High cadence G-band and H-alpha images Active region evolution in Photosphere and Chromosphere Flare and prominence studies H-alpha Dopplergrams providing los velocities Photospheric vector magnetic field using FeI nm line Full line profile and all the Stokes profiles (I, Q, U, V) Ca II 854.2nm line centre images for Chromospheric studies Chromospheric magnetograms in CaII nm with limited line profile scans All of the above data products could be used for understanding the relation between the magnetic field and the features observed in different SUIT wavelengths Thank you