The National Aeronautics and Space Administration-sponsored balloon flight of the Solar Bolometric Imager (SBI) is scheduled for September 2003, and it presents an important opportunity to measure the wide-band photometric contributions of bright photospheric magnetic structures to the total solar irradiance variations. Uncertainty in these contributions is presently one of the main obstacles to assessing the likelihood of secular irradiance variations in excess of those now linked to sunspots, faculae and changes in the network area. This effort will support co-ordinated ground-based photometry during the flight. This will have the added benefit of enhancing the science output from the SBI flight by broadening the range of structures measured. The greater significance of the research lies in its direct importance for climate studies and the interpretation of 20th Century global warming.
