High Accuracy Absolute Long Distance Metrology using femtosecond lasers : Optical frequency combs and spectral interference techniques

At the frontiers of science and technology of High Accuracy Absolute Long Distance Metrology (HAALDM), femto-second based laser (FSL) systems show promise for combining incoherent time-of-flight absolute distance measurement capabilities over large distances with coherent high resolution interferometric methods. The combination of a long-range absolute distance measurement scheme with a method for simultaneous sub-wavelength resolution is a combination of requirements that naturally leads to a broadband or multi-wavelength measurement scheme. In order to cover a range-to-resolution ratio of 108 for a distance of tens of metres to 1013 for a distance of thousands of kilometres, it is obvious that coherence and stability of the optical "ruler" to be better than 8 to 13 decimal digits is required. Recent advances in optical metrology are particularly promising in this respect achieving 15 decimal digits in accuracy and beyond with an optical frequency comb. Here we analyze the application of femto-second optical frequency combs to spectral techniques for HAALDM in satellite formation flying missions.