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Infrared Data Reduction

Infrared Data Reduction. K. Michael Merrill. Windows on the Universe. Electromagnetic Spectrum. Historic Perspective. 1960’s - Discrete pixel devices 1968 - Two Micron Sky Survey to K=3 1970’s - AFCRL Rocket Survey 1980’s - IR arrays deployed 1983 - IRAS deployed

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Infrared Data Reduction

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  1. Infrared Data Reduction K. Michael Merrill

  2. Windows on the Universe

  3. Electromagnetic Spectrum

  4. Historic Perspective • 1960’s - Discrete pixel devices • 1968 - Two Micron Sky Survey to K=3 • 1970’s - AFCRL Rocket Survey • 1980’s - IR arrays deployed • 1983 - IRAS deployed • 1990’s - Rapid growth in array technology • 1998 - 2MASS to K=14 • 2003 - SIRTF • 201? - JWST

  5. AtmosphericTransmission1 - 6 mm

  6. Atmospheric Transmission 6 - 30 mm

  7. Background sky radiation

  8. Background sky radiation OH airglow Thermal emission

  9. The Operations Challenge in the IR • The sky is always bright (and variable on many time scales) • Site selection • Adopting an observing strategy with active sky subtraction • The telescope can be seen in thermal emission • Reduce mirror emissivity & do not warm baffle • Re-image the telescope mirror inside the instrument & cold baffle • The instrument can be seen in thermal emission • Cool the instrument in vacuum (at or below 77K) • The array can see itself • Cool the array as needed (77K, 30K, 8K, depending on device) • Observations tend to be background (rather than detector) limited • Detecting 2X fainter takes 4X longer

  10. Planck function:black-body radiation Wein’s Law:  max2898K Emittance = T4

  11. InSb Array Development at NOAO • March of the pixels: • 58X62 (smallest box) • 256X256 • 1024X1024 ALADDIN - deployed worldwide • 2048X2048 Orion - active development • NEWFIRM footprint with 4 Orion detector focal plane mosaic • Science in the raw: • H2 gas emission (left insert) • PAH dust emission (middle insert) • JHK color composite (right insert) Backdrop: 2MASS JHK view of the Orion Nebula

  12. Orion Focal Plane Module Clock and Biases Output Current Mirrors Light Baffles Outputs 1-32 Outputs 33-64 AlN Motherboard Invar36 Pedestal Alignment Locator Detector SCA Photo Courtesy RIO

  13. 2X2 Mosaic of Orion Modules: 4098X4098 Build a 4Kx4K Focal Plane from four Orion Modules

  14. MBE HgCdTe Cross Section Silicon Read Out IC Incident Photons

  15. InSb Array Cross Section

  16. Non-destructive Readout • Photo-electrons accumulate until reset • Difference between two reads minimizes fixed pattern noise Pixel Readout kTCnoise 0.5 V Reset Reset Readout CDS Signal Diode Bias Voltage Double Correlated Sampling: Fowler 1 Readout 0 V Time

  17. Non-destructive Readout • Photo-electrons accumulate until reset • Difference between two reads minimizes fixed pattern noise Pixel Readout kTCnoise 0.5 V Reset Reset Readouts MCS Signal Diode Bias Voltage Multiple Correlated Sampling: Fowler N (=4) Readouts 0 V Time

  18. Read noise

  19. SQIID Optical Schematic

  20. SQIID: dichoric side

  21. SQIID channels from the camera side

  22. Old SQIID

  23. Mosaic: a grid of spatially offset images

  24. Registered composite images at K(2.2m), H(1.6m) & J(1.25mm)

  25. NGC 2024: the Flame Nebula Visible:Red IR: JHK

  26. SQIID JHK composite of the Galactic Center Region: 7X7 dithered spatial grid

  27. Sgr A @ K

  28. Star Speeds Around Milky Way’s Black Hole

  29. Galactic CenterIR Composite

  30. Sgr A at 3 to 4 microns

  31. Galactic Center in Brackett Alpha Brackett Gamma and Molecular Hydrogen

  32. Galactic Center at 9/13/21 microns Visible Near IR

  33. Multi-wavelength astrophysics with SQIID:simultaneous operation of 4 arrays sharing a single FOV through dichroics M17: the Omega Nebula

  34. Image processing: separating the stars from the debri of gas and dust

  35. NGC 7129: JHK SQIID composite

  36. NGC7538: JHK SQIID composite

  37. W3 IRS1K L L’ composite

  38. M42: the Orion Nebula

  39. Views of Orion Molecular Cloud 1

  40. Egg Nebula in Polarized Light

  41. High Background Science • Imaging at the South Pole • NOAO Abu system on SPIREX • two season demonstration • relentless observing • limited by data flow, not natural background • Challenge to excel… NGC6334 - PAH,L,M’ composite

  42. S106

  43. S106

  44. Data cube The spatial grid of long slit spectra can be assembled into a 3D structure, then sliced along the dispersion axis (by wavelength) to yield registered images throughout the spectral range.

  45. S106: infrared spectral imaging Observations at the KPNO 1.3m with the Cryogenic Spectrometer (CRSP) at a (2 pixel) wavelength resolution of 2000 across a single spectral baseline from 2.12 mm to 2.25 mm stepping the slit to map the source simultaneously. Left Panel: molecular H2 lines [red:v=1-0 S(1) at 2.122mm; green:v=1-0 S(0) at 2.224mm; blue:v=2-1 S(0) at 2.248mm]. These line ratios depend sensitively on excitation (fluorescence or dynamic shock) and density. Right Panel: ionized lines of hydrogen Brackett g  and [FeIII] (green: 3G5-3H6 at 2.218mm; blue:3G5-3H4 at 2.242mm). These line ratios depend on excitation, density and temperature.

  46. S106 H2 Br 

  47. SQIID Data Processing Overview • The NOAO SQIID Infrared Camera produces simultaneous images of the same field • in the J, H, K, and narrowband L passbands, using individual 512X512 quadrants • of ALADDIN InSb arrays. • The observations are generally background (photon statistics) limited. • Typical observing programs include: • taking a few (2-5) exposures on the same target with small offsets (to counter • ghosts and bad pixels and improve spatial sampling of the images) • taking many exposures of the same target with a dither pattern of offsets • (to build up long exposures) - DEEP • spatial mosaics of dithered pairs of images covering larger regions with limited • overlap between images (to build up large images) - WIDE. • These three kinds of observations are distinguished because they require somewhat • different data reduction strategies.

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