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“Infrared Spectroscopic Imaging Survey (IRSIS) payload for an Indian Satellite”

(1 st Indo-French Meeting, 04-Dec-2007). “Infrared Spectroscopic Imaging Survey (IRSIS) payload for an Indian Satellite”. S K Ghosh on behalf of IRSIS team ( TIFR, IUCAA, PRL, IIA, ARIES, Paris Observatory, IAS-Orsay ).

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“Infrared Spectroscopic Imaging Survey (IRSIS) payload for an Indian Satellite”

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  1. (1st Indo-French Meeting, 04-Dec-2007) “Infrared Spectroscopic Imaging Survey (IRSIS) payload for an Indian Satellite” S K Ghosh on behalf of IRSIS team (TIFR, IUCAA, PRL, IIA, ARIES, Paris Observatory, IAS-Orsay)

  2. Motivation & Scientific objectives for the IRSIS Proposal : -Exploit the crucial gap in astronomical spectroscopic capability in the wavelength range 2 - 6 micron (left between HST-NICMOS cut-off & SPITZER-IRS cut-on) -Being unexplored ‘territory’, enormous science potential even with an experiment with limited capabilities (i.e. limited sophistication & resources); - Need for Space borne experiments (Earth’s atmosphere : transparency, background)

  3. Primary science goals : Spectroscopic Survey at 1.7-6 mm covering > 50% of the full sky (within 2 years) including the Galactic plane ; (i) Detection of several spectral lines & features from the Interstellar Medium (ISM) of our Galaxy (inaccessible from ground); (ii) Spectra of stars in our Galaxy and nearby galaxies; (iii) Complete census of Low Mass objects in the Solar neighbourhood (~ 30 pc).

  4. Large volume of quantitative details leading to much better understanding of energetics & composition of the Interstellar Medium; • Infrared characterization of (1) stars, and (2) various types of Solar system bodies.

  5. Indian InfraRed Spectroscopic Imaging Survey (IRSIS) Scientific Objectives #1 • Interstellar gas in the Galaxy (+ LMC, SMC, M31) : • mapping the Galactic Plane in • - PAH bands at 3.3 & 6.2 mm (1.68 mm harmonic), • size distribution from relative strengths; PAD at 4.2 mm; • - recombination lines : • Paschen-a (20% of Ha), Brackett-a (10%) ; • - ro-vibration bands of molecular H2, HD ; 2) Interstellar & circumstellar solid matter : - very small grains (nanodiamonds from 5 mm feature) ; - signatures of hydration of silicates (in absorption) ; - elongation vib modes of isolated OH (2.6-2.9 mm) - carbonaceous matter ; - distribution of interstellar ices (H2O @ 3.07 mm, CO2,CH4), ISM  primitive solar nebula (Comet formation) ;

  6. Indian InfraRed Spectroscopic Imaging Survey (IRSIS) Scientific Objectives (continued …) #2 3) Stellar populations in the Galaxy (classification) : - precise study of evolved stars (giants, supergiants, PNe) - chemical composition (metallicity) - effective temperatures & luminosity classes (from CO & H2O indices) - stars with dense envelopes (H2O & NH3 ices @ 3.1mm) - emission line objects (Be star, proto-planetary nebulae, Fe II lines, PAH bands in post-AGB nebulae, …) 4) Low mass stars in the solar neighbourhood : - complete census (dwarf stars : class M, L, T, brown dwarf characterized by molecular bands; e.g. CH4) - precise mass & age (using model)

  7. Indian InfraRed Spectroscopic Imaging Survey (IRSIS) Scientific Objectives (continued …) #3 5) Star forming regions : census of the nearby complexes (Taurus, Ophiucus, etc) complete up to ~ 10 Jupiter masses ; 6) Population of distant (z ~ 2-3) starburst galaxies (from limited deep survey, ~ 30 sq. deg.) : first generation stars  period of galaxy formation, (rest frame visible spectra shifted to IR) ; diffuse extragalactic background ; 7) Small bodies of solar system : ~ 3000 asteroids & comets, their mineral composition ; evolution of solar system ; 8) Unexpected discoveries from new survey … ??

  8. Important spectral lines in the 1.7-6 mm range inaccessible from the ground Wavelength (mm) Line identifier Type of target 1.87 Paschen-a stars / ISM 1.96 [Si VI] PN 2.41 H2 (1-0, Q(1)) ISM 2.63 Brackett-b stars / ISM 4.49 [Mg VI] PN 4.53 [Ar VI] PN 5.61 [Mg V] PN

  9. Important spectral bands in the 1.7-6 mm range inaccessible from the ground Wavelength (mm) Line identifier Type of target 1.8 C2 Carbon stars 1.9 H2O M stars 2.4 CH4 Brown Dwarfs 2.7 OH in Silicates ISM 3.05 Ice (H2O) ISM 3.1 C2H2, HCN Carbon stars 3.3 PAH (in emission) ISM 3.5 nano-diamonds stars 4.2 Ice (CO2) ISM 4.6 CO M/C Stars 5.2 C3 Carbon stars 6.0 Ice (H2O) ISM 6.2 PAH (in emission) ISM

  10. Examples of typical spectra : (rich !) Cushing et al (2006)

  11. Example of topicality : Comparison between measurements ( ) and theoretical models ( , ) (R ~ 200) (M2 super-giant) Tsuji (2006)

  12. “Quality” of the Atmospheric Windows in the Near & Mid Infrared (#1) (Kitt Peak; 2080 m; “best condition”) J H K 1.0 0.5 Transmission 2.6 1.0 1.4 2.2 IRSIS coverage Wavelength ( mm)

  13. Atmospheric transmission …. (continued #2) (… at Mauna Kea; 4200 m) L’ 1.0 0.5 Transmission 3.2 3.6 4.0 4.4 Wavelength (mm) IRSIS

  14. Atmospheric transmission … (continued #3) (… at Mauna Kea; 4200 m) • emissivity  background M 1.0 0.5 Transmission 4.2 5.4 Wavelength (mm) IRSIS

  15. Atmospheric transmission … (continued #4) (… at Mauna Kea; 4200 m) N Q Transmission 1.0 0.5 6.0 10 14 22 IRSIS coverage 28 Wavelength (mm)

  16. Atmospheric Backgrounds : affecting ground based observations - - atmospheric “fluorescence” : AIRGLOW; OH- originates at ~ 100 km ; spatial & temporal variation too ! limits photometric accuracy ; • at l > 2.3 mm, dominated by thermal emission • (230-280 K; peak ~ 12 mm) ; • + emissivity of the telescope ; • - scattered moonlight

  17. Infrared background at the ‘best’ site (Mauna Kea) (comparison with space platform) @ 4,200 m Jy/(sq. arc-sec) M K L IRSIS COBE

  18. We just saw – Infrared astronomy (near/mid IR) from Space : has many advantages over Ground based ; (access to uninterrupted wavelength range; lower background, not varying with time ; etc) Matured Satellite Platform/(s) available to us (Indians) ! (Courtesy : ISRO) BUT, what is the international scene (competition) ?

  19. Perspective vis-a-vis international scene

  20. Given the international scene, is there a niche for Indian astronomers ? Yes ! - Exploit ~ 2-6 mm gap in Spectroscopic capabilities between IRS/Spitzer & NICMOS/ HST !! - ASTRO-F is unsuitable for Spectroscopic Survey covering large fields ; • Concentrate on Spectroscopic Survey with emaphasis on features / lines inaccessible from the ground ; Major strength : - Large sky coverage (Survey) with Spectroscopic dimension ! - simultaneous capability of Spectro-photometry of ‘point’ as well as ‘extended’ sources !

  21. Technical feasibility ? What are the major Technological challenges for realizing an Infrared spectrometer (~1.7-6 mm ) with R ~ 100 ? - cryogenics (achieving ~ 80 K in Low Earth Orbit, Earth’s albedo) provenspace grade cryo-coolers now (2004+) available commercially ! - space grade detector arrays with ‘astronomy’ grade performance; ~ 80 K operation ? recent developments from JWST efforts ! - fibers with transmission in 1-6 mm new materials developed in France !

  22. Summary of the proposed instrument (IRSIS) #1: Wavelength coverage : 1.7—6.5 micron Sky coverage : > 50%, including Galactic Plane Angular resolution : 18” Spectral resolution, R = (l/Dl) ~ 100-120 Survey Sensitivity (3-s; 10 sec) – Point source : @K (2.2 mm) = 14 mag. Diffuse emision : SW (1.7-3.4 mm) ~ 0.4 MJy/Sr LW (3.2-6.5 mm) ~ 1.5 MJy/Sr Confusion limit : 2,500 stars/sq. deg.

  23. Summary of the proposed instrument (IRSIS) #2 : Medium size telescope : ~ 30 cm (dia) @~120K Instantaneous FoV : 15’ x 15’ (9 sub-fields - 5’x5’, each feeding one slit) Micro-lenses + Infrared fiber-bundles couple Focal Plane to multiple slits of 2-channel spectrometer : Channel SW : 1.7—3.4 mm; Channel LW : 3.2 – 6.5 mm; Optical components for dispersion (Grating) Cooled (~ 80 K) detector arrays : 1024x1024 HgCdTe (x 2)

  24. IRSIS : Basic Specs -

  25. Typical expectations from IRSIS : • -Typical number of stellar spectra detected : • ~ 2,000 per sq. degree (@ Galactic lat., b ~ 0 deg. • ~ 500 per sq. degree (@ b ~ 45 deg. • -Detection of 3.3mm PAH feature from the • Galactic Plane with S/N ~ 100 (10 sec. int.); • Number of L-Dwarfs discovered & • classified : ~ 2,500; • -Number of Asteroids & Comets with • detected spectral features : ~ 3,000;

  26. Block diagram of IRSIS

  27. Spectroscopic Imaging : Topology - Telescope focal plane  Slit  detector array Simultaneous spectra from all sub-areas (fibers) of sky !

  28. Concept from MUSE instrument (ESO-VLT)

  29. Exploring 1-degee of freedom (telescope moves, spectrometer fixed to S/C deck) Very deep exposures for selected targets possible;

  30. IRSIS with one degree of freedom : ?? (NOT TO SCALE)

  31. Target low-power cryo-cooler with space heritage (K508 from M/s RICOR) (220mW load @ 77 K) Mass : 450 gm Size : 70-120 mm Power : 7 W (steady) 17 W (max) MTBF : 10,000 hrs (Used in MMM payload of Chandrayaan-1)

  32. Choice of Detector Arrays : Tunable cut-off wavelength (3.4 & 6.5 mm)  HgCdTe (MCT) FPAs Ultra-Low Dark Current at ~ 80 K Exciting recent developments related to James Webb Space Telescope (JWST) useful ! Development of MBE process for successful fabrication of larger format arrays (upto 2048 x 2048) Development of a powerful ASIC for driving the array and signal processing (SIDECAR), operational at cryogenic temperatures (30 K to RT)

  33. Liquid Phase Epitaxy (LPE)  Producible Alternative to CdTe for Epitaxy (PACE) PACE-1  Sapphire substrate Molecular Beam Epitaxial (MBE)

  34. Drastic reduction in Dark Current for MBE -

  35. Identified Detector array : HAWAII-1RG ‘R’  Reference columns : Insensitive to temperature variations;

  36. Big saving in Mass, Power; EMI/EMC

  37. (ASIC cost ~ Rs. 200 Lakh!) DETECTOR ASIC

  38. ASIC - SIDECAR : System Image Digitizing, Enhancing, Controlling And Retrieving Fully software controlled selectable Read-Out scheme ! 22 mm x 15 mm 30 K  RT < 0.1 Watt

  39. Orbit & Spacecraft specs - 900 km Polar Sun-synchronous Inertial, 3-axis stab. (L2 ?)

  40. Mass budget -

  41. Raw Power Budget -

  42. Proposed plan for implementation (institutional responsibilities): a) TIFR : Overall system configuration, Telescope optics, Thermal (Passive/active Cooling), Detectors, Mechanical Structures, Data Handling, Interfaces with the Spacecraft-bus; b) IUCAA : Fiber optic system design; c) PRL : Optical design /development of Spectrometers; Ground based follow-up; d) IIA : Off-line data processing pipeline software; e) ARIES : Data analysis; e) Paris Observatory + IAS-Orsay: Micro-lenses; Cryogenic Infrared Fibers (Anamorphoser)

  43. Important components :

  44. Realization strategy :

  45. Status & Plans : ISRO’s Announcement of Opportunity (AO) : March 2006 Proposal Deadline : July 31, 2006 (IRSIS version #1) TIFR review (XI Plan) : September 2006 Results of ISRO Review #1 : November 2006 (suggested improvements) IRSIS version #2 : January 2007 IRSIS-ISRO Technical meeting : March 2007 IRSIS version #3 : April 2007 Results of ISRO Review #2 : August 2007 (Phase 1 support : 2 years for Engineering Model) Next actions : Detailed Project Report (DPR) by December 31, 2007 Baseline Design Review (BDR) ~ February 2008 ? Preliminary Design Review (PDR) ~ end-2008 ??

  46. Thank you !

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