Spartan Spartan Infra-Red Camera

1. Information herein adapted from SOAR web pages. For complete information, please see http://www.pa.msu.edu/~loh/SpartanIRCamera Spartan Spartan Infra-Red Camera E N Image of the Crab Nebula taken with Spartan using the molecular hydrogen filter (2.122μ + continuum; Loh, Baldwin, et al, in prep). The inset shows an H2 complex with four H2 knots (Loh, Baldwin, Ferland 2010, ApJ, 716, L10). Spartan IR Camera revealed---the light beam enters at the lower left, passes through a mask wheel, becomes collimated by the wide-field (WF) collimator (upper left), goes through fold mirrors, a filter wheel and Lyot stop (hidden by the large shiny plate that holds the assembly), becomes focused by WF focusing mirror at the upper right onto the 4-eye detector assembly (lower right) which tilts the detectors when changing between the wide-field and high-res configurations. Shown is the wide-field configuration (68mas/pixel); in the high-res (HR) mode, the HR collimator is rotated into the beam and the WF focusing mirror is rotated out. The circular object at the left is the reservoir for liquid nitrogen. Image courtesy of E. Loh. The NOAO Staff Contact for Spartan is: Dr. Jayadev Rajagopal: jrajagopal@ctio.noao.edu Queries for SOAR specific information should be directed to: Dr. Steve Heathcote: sheathcote@ctio.noao.edu, or Dr. Sean Points: spoints@ctio.noao,edu

2. Schematic of the instrument oriented with the front of the instrument down and the top toward the viewer. The mirrors and 4-eye are positioned for the high-resolution mode. The principal ray is the blue line for the wide-field mode and red for high-resolution. The base design for the Spartan optics is a pair of parabolas. One of these parabolic mirrors collimates the light emanating from its focus. The second parabolic mirror refocuses the light to form an image. By using an off-axis segment, the incoming and outgoing light beams do not interfere. There is a real image of the entrance pupil for a Lyot stop. This design also allows for a change in focal ratio by making the focal lengths of the two mirrors different. The actual design adds several components to the base design. Two flat fold mirrors separate the telescope and instrument images, that are nearly coincident in the base design. The field curvatures of the SOAR telescope and the mirrors have opposite sign. A CaF2 plano-convex lens removes the net field curvature. The lens, placed a few mm from the detector, rotates with the detector when changing the focal ratio. Two sets of mirrors provide for the two focal ratios. To change from the f/12 to the f/21focal ratio, a mechanism inserts the f/21 collimator in front of the f/12 collimator and another mechanism moves the f/12 camera mirror to expose the f/21 camera mirror. Furthermore, a third mechanism rotates the detectors by 9°. The properties of these two imaging modes are listed in the table below. 1The QEs presented in this table are from Rockwell/Teledyne. They have not been checked against engineering measurements and are subject to change. Spartan Overview & Status (Cont): Two filter wheels (between the fold mirrors) hold 50-mm circular filters. Lyot stops will be placed in the smaller wheel which is at the image of the primary mirror of the telescope, in addition to 11 other filters. The larger filter wheel can contain up to 18 filters, including oversized Lyot stops for the J and H bands, where thermal radiation is not important. In addition to the broadband Y, J, H, and K filters, line and continuum filters covering HeI, [FeII], HeI/CIV, H2, Brγ, and CO. The image quality of the instrument is excellent. The Strehl ratio of the instrument itself (not including the atmosphere) is quite high. The mean Strehl across the field is greater than 98% for the high resolution channel. The mean Strehl ratios are 91%, 95%, and 97% for the wide-field channel in the J, H, and K bands. The atmosphere does not preserve diffraction-limited information in the J band, and the pixel size is not sufficient to sample the diffraction limit in the wide-field channel. Spartan Overview & Status: The Spartan Infrared Camera operates in the 1–2.4μmwavelength range for imaging. It has two focal ratios, an f/12 wide-field (WF) imaging mode with 68 mas/pixel for a wide field and an f/21 high-res (HR) imaging mode with 41 mas/pixel for high angular resolution. In the high-res configuration, the detectors resolve the diffraction limit in the atmospheric window at λ 1.6μm. The detectors are four HAWAII-2 arrays with 2048×2048 pixels. The quantum efficiencies (QEs) of the four detectors in the J, H, and K broadband filters are given in the table below1.