Many space based optical systems, especially in the infrared, have the constraint that the focal plane cannot be adequately sampled due to IR detector constraints. Adequately sampled refers to sampling at twice the optical MTF cutoff frequency. Generally the focal plane contains multiple columns of detectors with each detector element being large with respect to the system PSF. This necessitates a system which is scanned either by moving a scan mirror or physically moving the spacecraft or a combination of both. Discussed is a method which allows rapid construction, from multiple column scan data, of an image sampled on a square grid with minimal modification of frequency content up to the spatial Nyquist frequency of the image grid. The method relies on a modified implementation of the 2-D Whittaker-Shannon sampling theorem to minimize aliasing and `spectral leakage.' The algorithm and its implementation for the Spirit III radiometer of the Mid-Course Space Experiment (MSX) are discussed along with a rapid implementation on a multiple processor desktop workstation.