1 Construction and design

By the time of the Cassini/Huygens Announcement of Opportunity, my small research group and I had had a lot of experience analyzing observations of Titan made from the Earth and flyby missions from spacecraft. We assembled a list of measurements we could make from an entry probe to constrain all the parameters of Titan's aerosols that had been so difficult to determine from measurements made only outside the atmosphere. We wanted to determine the profiles of optical depth, single scattering albedo, phase function, and ground reflectivity as functions of wavelength from the near ultraviolet to the near infrared. We developed a plan to use a charge-coupled device (CCD) and a simple IR linear array detector coupled by fiber optic bundles to several different sets of fore optics. In this way we could use cameras to view the scene from the probe, map the solar aureole to constrain the phase function, and measure the spectra of upwelling and downwelling solar radiation to measure optical depths, solar flux, single scattering albedos, heating rates, and ground reflectivities. This could be done using only one moving part (a shutter over the input to the IR spectrometer). We would also include a lamp to illuminate the ground from low altitudes to measure the ground reflectivity even in spectral regions where methane absorption prevented solar radiation from reaching the ground. We even found a German team to provide the CCD and driver electronics, as well as a French team to provide the IR array with its drivers.