  In February 2011 we proposed a NASA Explorer Mission of Opportunity program
to develop and operate a large-aperture ultraviolet coronagraph spectrometer
called the Coronal Physics Investigator (CPI) as an attached International
Space Station (ISS) payload. The primary goal of this program is to identify
and characterize the physical processes that heat and accelerate the primary
and secondary components of the fast and slow solar wind. In addition, CPI can
make key measurements needed to understand CMEs. UVCS/SOHO allowed us to
identify what additional measurements need to be made to answer the fundamental
questions about how solar wind streams are produced, and CPI's next-generation
capabilities were designed specifically to make those measurements. Compared to
previous instruments, CPI provides unprecedented sensitivity, a wavelength
range extending from 25.7 to 126 nm, higher temporal resolution, and the
capability to measure line profiles of He II, N V, Ne VII, Ne VIII, Si VIII, S
IX, Ar VIII, Ca IX, and Fe X, never before seen in coronal holes above 1.3
solar radii. CPI will constrain the properties and effects of coronal MHD waves
by (1) observing many ions over a large range of charge and mass, (2) providing
simultaneous measurements of proton and electron temperatures to probe
turbulent dissipation mechanisms, and (3) measuring amplitudes of low-frequency
compressive fluctuations. CPI is an internally occulted ultraviolet coronagraph
that provides the required high sensitivity without the need for a deployable
boom, and with all technically mature hardware including an ICCD detector. A
highly experienced Explorer and ISS contractor, L-3 Com Integrated Optical
Systems and Com Systems East, will provide the tracking and pointing system as
well as the instrument, and the integration to the ISS.
