[Instrument Designs for SOFIA: FOCUS and FORCAST]

As a result of these studies a proposal for FORCAST was submitted to the SOFIA Announcement of Opportunity for Instruments. FORCAST, a facility instrument, was one of the winning proposals. A short description of FORCAST follows: (1) FORCAST is a dual-channel, high-sensitivity, wide-field camera designed to perform continuum imaging in the mid-infrared (4-8 microns) and far-infrared (16-40 microns). The pixels map to 0.75 sec. on the sky and the total field-of-view is 3.2 min. During normal operation a cold MgO dichroic allows imaging in two bands (16-25 and 25-40 microns) enabling high efficiency, simultaneous observations. For imaging at shorter wavelengths (4-8 microns), a mirror replaces the dichroic. FORCAST simultaneously operates two 256 x 256 Si BIB hybrid arrays from Boeing (formerly Rockwell). A Si:As BIB array is used for lambda less than 25 microns while a Si:Sb BIB array is use for lambda greater than 25 microns, FORCAST allows selection of the bandpass independently for each channel via filter wheels. Several specific filters are needed for the Pi science program. Selection of other filters will be based on input from the SOFIA science community. These can include filters to cover specific lines or dust features (such as the PAH features in the 4-8 microns regime). Future upgrades could include a polarimetric capability. The Pi team has extensive experience with all of the technologies used in FORCAST. FORCAST uses mature, low-risk, state-of-the-art technology ensuring highly reliability. In addition, FORCAST will be easy to set up for an observing run and easy to operate (with an intuitive graphical interface). We feel that we can virtually guarantee success on the first flight with FORCAST. FORCAST is designed to complement SIRTF (ISO will no longer be functional). While it cannot achieve the sensitivity levels of SIRTF, FORCAST covers sections of phase space not planned for SIRTF (30-40 microns imaging) and has significantly higher spatial resolution than SIRTF at all wavelengths.