Observations of carbon allow us to study all phases of the interstellar medium. Although carbon in dust and molecular forms is routinely observed from the ground, atomic carbon observations are quite difficult, because atmospheric water vapor is nearly opaque to their submillimeter spectral lines except at the very driest sites. Neutral carbon is particularly important because of its central roles in (1) the formation of giant molecular clouds, which in turn form new stars, and (2) the interaction of radiation from newly formed stars with its ambient parental material. CARA's AST/RO telescope is the first to observe neutral carbon routinely and almost continuously.
The magnetic field is a component of the interstellar medium that is both dynamically important and difficult to observe. For this reason, it is significant that a new technique for mapping magnetic fields has recently been developed: far-infrared/submillimeter polarimetry of thermal emission from magnetically aligned grains. By carrying out observations from the South Pole, where the submillimeter observing conditions are superb, it will be possible to extend this technique to regions of low column density that cannot be studied from other sites. Observations with CARA's SPARO (deployed in 1999), a 9-pixel 450 micron polarimetric imager, will be complementary to millimeter/submillimeter polarimetry that is currently being carried out, for example, at the Caltech Submillimeter Observatory and the Owens Valley Radio Observatory. In comparison with the South Pole, these facilities give much better angular resolution, but much worse sensitivity to extended emission.CARA submillimeter instruments include: