urn:nasa:pds:context:instrument:ctio-cerro_tololo.2mass_1m3.2masssouth 1.4 1.25.0.0 Product_Context urn:nasa:pds:context:instrument:ctio.2mass1m3.2masssouth 2026-07-07 1.4 Removed duplicate Internal_Reference entries from Reference_List. 2025-12-24 1.3 Adding missing "facility" references. Adding missing "telescope" references. 2025-12-24 1.2 Updated schema version. Adding missing "facility" references. Adding missing "telescope" references. 2025-01-02 1.1 Updated schema version. Adding missing "telescope" references. 2021-12-07 1.0 per RMS, deprecated ctio in favor of ctio-cerro_tololo urn:nasa:pds:context:telescope:ctio-cerro_tololo.2mass_1m3 instrument_to_telescope urn:nasa:pds:context:facility:observatory.ctio-cerro_tololo instrument_to_facility Milligan et al., SPIE Proceedings Volume 2863, p. 2, 1996. 2MASS Camera - South Imager 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.