"We are developing rotating-baseline nulling-interferometry techniques and algorithms on the single-aperture Hale and Keck telescopes at near-infrared wavelengths, aimed at the detection of faint emission close to bright stars. Our experiments are aimed at developing simple and robust nulling interferometer systems, that will be useful in the short term for unique observations of faint exozodiacal emission and exoplanets very close to nearby stars, and in the long term for refining and simplifying potential nulling-interferometer-based space missions. Here we propose significant sensitivity, stability, dispersion-reduction and statistical-analysis upgrades to  our nulling interferometer systems so as to take our nulling work from the earlier ""basic physics demonstration"" phase to the ""ultimate limiting performance"" stage.



 Several planned upgrades to our nulling systems will enable forefront nulling capabilities at very low cost.  First, we plan to improve the sensitivity of our Palomar Fiber Nuller by two orders of magnitude by replacing our current very modest detector with a much more sensitive IR camera inherited from the Palomar Testbed Interferometer. Second, we plan to improve our fringe stability through a series of upgrades. We will make use of the P3K extreme adaptive optics capability to come on line at Palomar mid-2011 to enable ~ 70 -100 nm stability between subapertures, and also extremely good fiber-coupling stability, together allowing very deep nulls to be measured. We will also upgrade our own post-adaptive optics fringe tracker and implement a novel fluctuation-tolerant fringe tracker algorithm.  Third, we will further develop and test novel data reduction algorithms based on the statistics of the null-depth fluctuations to measure accurate astrophysical nulls to levels much deeper than our stabilization level would otherwise allow. Finally, we will also implement a number of dispersion reduction techniques to improve broadband operation an