The Array Characteristics min. readout time 3.227s gain: 4.25 e-/ADU well depth : 150,000 e-

1. ISPI 5492-106 a wide field NIR imager for the CTIO Blanco 4-meter telescope Nicole S. van der Bliek, Ron Probst, Dara Norman, Robert D. Blum, Andres Montane, Ramon Galvez, Michael Warner, Roberto Tighe, Francisco Delgado & Manuel Martinez CTIO/NOAO http://www.ctio.noao.edu/instruments/ir_instruments/ispi/ • First light with ISPI was obtained on Sept. 24 2002, and since January 2003 ISPI has been in operation as a common user instrument. We discuss the operational aspects of ISPI, the behaviour of the array and we report on the instrument performance during the first 1.5 year of operation. • 1 – 2.4 micron imaging with a 2K x 2K HgCdTe HAWAII-2 array • 0.3 arcsec/pixel sampling, matched to the f/8 IR image quality of 0.6 arcsec • 10.5 x 10.5 arcmin field of view • broad band J, H and Ks, as well as narrow band filters • Operational aspects • Cooling ISPI • cooled with LN2, hold time 36hrs. • ISPI is cooled slow: optics & array cool < 1.5K/min. • operating temperatures: • 77K @ detector to 150K @ first collimator lens. • vacuum during cool down & operation: • 10e-6 to 10e-7 Torr • molecular sieve (Linde 5A zeolite) installed near detector • ISPI is warmed up passively, taking several days • Mounting & boresighting • ISPI is mounted at the side port of the rotator, and held in place by a support at the backend. Boresighting is done during day-time, using 9 lights placed on the tips of the M2 petals (forming a ring of equally spaced lights, with variable radius) and checked at night time with a defocussed image of a bright star. • Filters • ISPI is currently equiped with 4 broad band filters:, Y, J, H and Ks, and 8 narrow band filters in the H and K band. There are two filters wheels, located in a box in the middle of the instrument. To access the filter wheels, the two dewars have to be taken apart, introducing the risk that the optics within the instrument are no longer aligned. • Analysis of the image quality over the course of 1.5 yr, during which the instrument has been opened 3 times, shows no impact on the image quality over the FOV. • The Graphical User Interface • ISPI is run through a Graphical User Interface. The top half of the panel display the instrument status. The bottom half allows the user to set the array control parameters (exp. time, # of co-adds), filter, telescope focus, off-sets. The GUI is an implementation of ArcVIEW, a LabVIEW based astronomical instrument control system, running under Linux. • The Array • Characteristics • min. readout time 3.227s • gain: 4.25 e-/ADU • well depth : 150,000 e- • 1% linear range: • full frame: 55,000 e-, illuminated spot: 100,000 e- • read out mode: double correlated sampling • Dead pixels and debonding of pixels • # of dead pixels: ~2920, located along a few rows, • and in 1spot. No significant change with time. • # of pixels lost/cold cycle, due to debonding: ~180 • All located in the corners; upper right corner most affected. • Instrument Performance • Throughput, based on data taken on Jan. 19, 2003 • Image quality & distortion • FWHM of 0.6 arcsec over full FOV. • Analysis of focus data show that best focus for the upper right (too low) and lower left corner (too high) of the array differ slightly from best focus of the rest of the frame, with the differences being largest for the upper right corner. This indicates that the array is slightly tilted and perhaps might imply that the upper right corner is bent. • Distortion in the images can be corrected for using linear or polynomial astrometric solutions, leaving residuals of less than 1 arcsec (polynomial fit) to a few arcsecs in the corners of the image (linear fit). Debonded pixels, upper right corner Sept. 2002 May 2004 1st cold cycle 5th cold cycle Boresighting result with lights on M2 petals (left) and checked with defocussed image of a star (right) First light image: 47 Tuc in H, FWHM = 0.6 arcsec