An IFU for IFOSC on IUCAA 2m Telescope A. N. Ramaprakash Inter-University Centre for Astronomy & Astrophysics, Pune Abhay, Atul, Hillol, Kalpesh, Mahesh, Moin, Mudit, Pravin, Ranjan, Shyam, Sujith, Swapnil, Vilas

IFU on IUCAA 2 m Telescope Plan of the Talk Telescope and IFOSC parameters Basic structure of the system Constraints on IFU Design for IFOSC on IUCAA Telescope IFU on IUCAA 2 m Telescope Design and Performance of the IFU Basic Design Selection criteria for parameters Performance IFOSC performance with IFU / Summary 4.12.2007 A. N. Ramaprakash, IUCAA

Techniques for 2-D Spectroscopy http://www.cfai.dur.ac.uk/new/spectroscopy/spectroscopy.html 4.12.2007 A. N. Ramaprakash, IUCAA

Built by Telescope Technologies Ltd., Liverpool, UK Location A glimpse of IGO Built by Telescope Technologies Ltd., Liverpool, UK Location Girawali - 80km NE from Pune, near Junnar Altitude - ~1000m above MSL Telescope Specification - 2m, f/10, Ritchey Chrétien, 6’ radius field Wide Field Corrector to extend field to 21’ radius Mount – Alt-Az on hydrostatic bearings Focus – Cassegrain (1 direct & 4 side ports) Active pneumatic mirror support (20cm thick) Integrated Autoguider 4.12.2007 A. N. Ramaprakash, IUCAA

Observatory Views 4.12.2007 A. N. Ramaprakash, IUCAA

IUCAA Girawali Observatory 4.12.2007 A. N. Ramaprakash, IUCAA

The 2m Telescope 4.12.2007 A. N. Ramaprakash, IUCAA

V-band median seeing in winter - 1.2" Extinction (mag./airmass) Site Vital Statistics V-band median seeing in winter - 1.2" Extinction (mag./airmass) B – 0.26 to 0.74 V – 0.14 to 0.38 Sky Brightness (mag/sq. arcsec) B – 21.8 V – 20.8 R – 19.3 Cloud cover over a period of six months (Nov. – April) 50% photometric 80% spectroscopic (Das et. al, ’99,BASI 27,609) 4.12.2007 A. N. Ramaprakash, IUCAA

IFOSC & Calibration Unit PI CCD NIPI Next Generation Instruments IFOSC & Calibration Unit PI CCD NIPI Next Generation Five Year Plan 4.12.2007 A. N. Ramaprakash, IUCAA

IUCAA Faint Object Spectrograph Camera (IFOSC) UBVRI filters 0.8”, 1”, 1.5”, 2” x 11’ slits 10 grisms (2 echelle & 2 cross dispersers) R = 190 to R = 3700  = 0.35m to  = 0.85m Polarimetry mode 2K x 2K EEV CCD with 13.5m2 pixels 40m/arcsec plate scale on CCD at f/4.5 (demagnification of 2.2) 4.12.2007 A. N. Ramaprakash, IUCAA

Direct Cassegrain Port F/10 Beam Primary Mirror Side Port A & G Unit Lamps Calibration Unit IFOSC IFOSC Object Plane / Telescope Focal Plane CCD Detector 4.12.2007 A. N. Ramaprakash, IUCAA

/ Telescope Focal Plane Calibration Unit Primary Mirror Side Port A & G Unit Lamps Folding Mirror Calibration Unit IFOSC IFOSC Object Plane / Telescope Focal Plane CCD Detector 4.12.2007 A. N. Ramaprakash, IUCAA

/ Telescope Focal Plane Cassegrain Side Port Primary Mirror Side Port Instrument Folding Mirror A & G Unit Lamps Calibration Unit IFOSC IFOSC Object Plane / Telescope Focal Plane CCD Detector 4.12.2007 A. N. Ramaprakash, IUCAA

IFU on IUCAA Telescope : Design Constraints Mechanical Constraints Can’t put Fibre-slit directly at the IFOSC object plane Dimension of the CCD + De-magnification of the IFOSC Maximum Dimension of Projected Fibre Slit on the IFOSC Object Plane ~ 59 mm 4.12.2007 A. N. Ramaprakash, IUCAA

IFU on IUCAA Telescope : Design Constraints Area–Solid Angle Product (AΩ) : Invariant Optical System A1 Ω1 A2 Ω2 A1 . Ω1 = A2 . Ω2 AΩ : Fixed by Telescope’s plate scale and F/number For 1 arc-sec sampling AΩ = 94.265 μm2 - steradians 4.12.2007 A. N. Ramaprakash, IUCAA

Basic Design Configuration of the IFU Fore-Optics Lenslet + Fibre Unit Output Optics IFU Teles-cope Spectro-graph Necessary magnification Proper sampling. Telecentric Output To couple fibre Slit to the Spectrog. Change the f/# of the beam Telecentric Output To Sample the sky image Feed light into the fibre with proper f/# 4.12.2007 A. N. Ramaprakash, IUCAA

Mechanical Configuration of the IFU Fore - Optics Lenslet + Fibre Unit Fibre Slit Primary Mirror Integral Field Unit (IFU) A & G Unit Output Optics Lamps This distance has To be > 80 mm (Opto-Mechanical Design Constraints) IFOSC Object Plane / Telescope Focal Plane Image of Fibre Core ~ Slit 4.12.2007 A. N. Ramaprakash, IUCAA

IFU on IUCAA Telescope : Design Constraints Focal Ratio Degradation (FRD) (F/#)out < (F/#)in Due to Micro-bending/Manufacturing Defects Statistical property Results in increase of (AΩ) product FRD should be minimized 4.12.2007 A. N. Ramaprakash, IUCAA

Focal Ration Degradation (Carrasco & Parry, 1994, MNRAS, 271,1-12) 4.12.2007 A. N. Ramaprakash, IUCAA

Design Optimization of the IFU To minimize FRD : (F / #)in < 5 so that, (F / #)out ~ (F / #)in Further, invariance of AΩ Lower the (F/#)fibre Better Spectral Resolution Smaller the Fiber Core Diameter Smaller (F/#)fibre is desirable 4.12.2007 A. N. Ramaprakash, IUCAA

Design Optimization of the IFU BUT IFOSC accepts ‘F/10’ beam F/# IFOSC F/10 Output Optics Fibre Core Magnification = 10 / (F/#) = M The projected slit width = M X Fibre Core Diameter ‘M’ affects the Spectral resolution 4.12.2007 A. N. Ramaprakash, IUCAA

Design Optimization of the IFU The maximum length of the Fibre Slit = 59 mm / M ‘M’ restricts the total numbers of fibres It is preferred to keep ‘M’ as low as possible. (F/#)fibre should be made as large as possible + Aberrations &Throughput Recipe for Design Optimization 4.12.2007 A. N. Ramaprakash, IUCAA

Basic scientific constraints of the IFU Optimized for the wavelength range 4500 – 8500 Å The sky area would be sampled by 100 Lenslets + Fibres Three spatial sampling scales 1.0" per fibre, 0.8" per fibre and 1.2" per fibre are being used. The sky area sampled by IFU ~ 14 arc-sec X 7 arc-sec (For the case of 1 arc-sec per fibre) 4.12.2007 A. N. Ramaprakash, IUCAA

Fore-optics, Lenslets and Fibres Telescope Focal Plane Lenslet + Fibre Unit u v d Singlet field flattener for telecentric output Achromatic doublet f2 ~ 508mm, v = 10mm, Lenslet Φ= 2.1 mm For different sampling scales, MFore-optics=f2/f1 (17.2, 21.8, 25.75); L2 & v kept fixed; Only L1, u and f1 changed. 4.12.2007 A. N. Ramaprakash, IUCAA

Sampling Diameter at Telescope focal plane Lenslet and Fibre Dpupil f DL= 2.1 mm Magnified Image by Fore-Optics F/number of the Lenslet = 4 F/number of the telescope = 10 Sampling Diameter at Telescope focal plane Lenslets provide continuous sampling of sky; they feed light into the fibre with the appropriate f/#. 4.12.2007 A. N. Ramaprakash, IUCAA

Output Optics IFOSC Output Optics Output Magnification ‘M’ Fibre Core Magnification = 10 / 4 = 2.5 Telecentric output Projected slit width = 2.5 X 70μm (Fibre Core Dia.) Maximum length of the Fibre Slit, = 59 / 2.5 ~ 23.6 mm 4.12.2007 A. N. Ramaprakash, IUCAA

Fore-optics layout – 1" per fibre sampling 4.12.2007 A. N. Ramaprakash, IUCAA

Lenslet Optical Layout 4.12.2007 A. N. Ramaprakash, IUCAA

Fore-optics Spot Diagram (1" sampling) 4.12.2007 A. N. Ramaprakash, IUCAA

Output Optics Layout This distance to be kept > 80 mm 4.12.2007 A. N. Ramaprakash, IUCAA

Output Optics and IFOSC 4.12.2007 A. N. Ramaprakash, IUCAA

Spot diagram at IFOSC object plane 4.12.2007 A. N. Ramaprakash, IUCAA

Spot diagram at IFOSC detector plane 4.12.2007 A. N. Ramaprakash, IUCAA

Fore-optics encircled energy diagram (1" sampling) 4.12.2007 A. N. Ramaprakash, IUCAA

Encircled energy at IFOSC detector plane 4.12.2007 A. N. Ramaprakash, IUCAA

(Ranjan Gupta et al., 2002, BASI, 30, 785) Spectral Resolution Slit width - 220 μm: Grism Peak (Angstrom) Wavelength range (Angstroms) Spectral resolution (Angstrom for 2.2 arc-sec slit) IFORS 5 4000 3300 – 6300 20.02 IFOSC5 6000 5200 – 10300 20.24 IFORS1 3300 – 5540 9.02 IFOSC7 5000 3800 – 6840 9.68 IFOSC8 5800 – 8350 8.14 (Ranjan Gupta et al., 2002, BASI, 30, 785) 4.12.2007 A. N. Ramaprakash, IUCAA

Sensitivity 4.12.2007 A. N. Ramaprakash, IUCAA