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Multi-Application Solar Telescope Preliminary results

Shibu K. Mathew Udaipur Solar Observatory

Multi-Application Solar Telescope

– Past Telescope specs. and components

Installation

Optical alignment and tests

– Present Back-end instruments

Preliminary observations

– Future Adaptive optics implementation

Regular G-Band and H-alpha observations

Vector magnetic field imaging

Multi-Application Solar Telescope 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 ± 1o 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


Collimated beam

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

M2

M3 M4

M5

DM1 DM2

DM3

M6

Output wave-front error better than /12


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


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 1oC 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.

Multi-Application Solar Telescope 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.

Multi-Application Solar Telescope 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

Multi-Application Solar Telescope 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, 0.025 arc-sec/min

Multi-Application Solar Telescope Telescope & Observing floor

Telescope floor Telescope enclosed with in the collapsible dome

Back-end instruments on the observing floor

Multi-Application Solar Telescope Back-end instruments

Broad G-band and Narrow-band H-alpha imager

CCD G-band

Halle Filter L1

BS

CC

D H

-alp

ha

G-band IF


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

Multi-Application Solar Telescope G-band and H-alpha sample images

G-band, AR 12192, 22 October 2014


H-alpha, AR 12192, 22 October 2014


H full disk image constructed from a sequential mosaic of 293 images taken by MAST on 19th May 2015.


G-band & H-alpha


AR 12436, 24 Oct 2015


Fabry-Perot Narrow band imager for Magnetic field measurements

• Two voltage tunable lithium niobate FP etalons in tandem, resulting pass-band around 60 mÅ @ 617.3 nm

• Filter wheel with two or more pre-filters.

• Presently two wavelengths at 617.3 nm and 854.2 nm (FeI and CaII) for photospheric and chromospheric observations.

• The filters were tested using a Littrow spectrograph installed close to the imager


Fabry-Perot Narrow band imager : voltage tuning

Littrow Spectrograph

FP1

FP

2

M1

M2

M

3

M4

M

5

Fro

m M

AST

FP2 -3000V

FP2 +3000V

FP1 +3000V

FP1 -3000V


Fabry-Perot Narrow band imager

61

7.3

nm

Pre

-Filter

FP1

+FP2

+Prefilte

r


Fabry-Perot Narrow band imager; optical layout

From MAST

FP1 FP2

CC

D

Pre-filter

AO Components

Polarimeter


Fabry-P

ero

t N

arrow

b

an

d

image

r; typ

ical tu

nin

g re

sult:

22

W

avele

ngth

po

sition

s alon

g the

61

7.3

nm

line

pro

file w

ith 1

5

mA

step

s


Polarimeter

(in degree)

Fast axis of

LC1, =0

(in degree)

Fast axis of

LC2, =45

Measured

Intensity, Imeas

315.0 305.264 I1=I+Q/3+U/3+V/3

315.0 54.736 I2=I+Q/3-U/3-V/3

225.0 125.264 I3=I-Q/3-U/3+V/3

225.0 234.736 I4=I-Q/3+U/3-V/3

(in

degree)

(in

degree)

Imeas

360 90 I1=I-V

360 270 I2=I+V

Modulation Scheme

2 LCVRs and Linear polarizer


Polarimeter, initial results from I+V & I-V measurement

I+V I-V V/I o-65mÅ

~o


Polarimeter, initial results from I+V & I-V measurement


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

resu

lts fro

m

the

w

ave-fro

nt

reco

nstru

ction

. 1

9

len

lets are

illu

min

ated

u

sing

the

pu

pil ligh

t

Multi-Application Solar Telescope 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.

Multi-Application Solar Telescope 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 617.3 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 854.2 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 ---------------------------------------------

Download - Udaipur Solar Observatory - Physical Research Laboratoryuso/suit_files/Shibu-SUIT.pdf · Udaipur Solar Observatory . Multi-Application Solar Telescope –Past Telescope specs. and

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