2MASS CAMERA - SOUTH
====================

  Instrument Overview                                                         
  ===================                                                         
    Each 2MASS camera consisted of a liquid nitrogen cryostat which contained 
    three 256x256 NICMOS3 arrays. Each array viewed the same region of the sky
    via beamsplitting dichroics. The light passed through both dichroics to   
    the Ks-band array. The first dichroic reflection fed the light to the     
    J-band array. All three optical paths shared the same first element       
    located behind a cryogenic field stop. Each optical path had six other    
    lenses. This set of six lenses was identical for each band. The lenses    
    were composed of water-free fused silica (Infrasil) or calcium fluoride.  
    All lens surfaces were spherical. All optical elements were               
    anti-reflection coated and the integrated optical assembly transmitted    
    ~70% of the incident light. A band-limiting interference filter located   
    near a pupil image established the system bandpass. Table 1 summarizes the
    Survey's bandpasses:                                                      
                                                                              
    Table 1:  2MASS 50% Transmission                                          
                                                                              
    Band    Optics and Camera       System + Atmosphere                       
    J       1.11 - 1.40 um          1.12 - 1.36 um                            
    H       1.51 - 1.79 um          1.51 - 1.78 um                            
    Ks      2.00 - 2.31 um          2.02 - 2.30 um                            
                                                                              
    This instrument catalog refers to the 2MASS camera used at the southern   
    hemisphere 2MASS facility, at the Cerro Tololo International Observatory  
    in Chile.

References
==========

Milligan et al., SPIE Proceedings Volume
        2863, p. 2, 1996.