NASA's EOS Aqua spacecraft was launched on May 04, 2002. The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of the six Earth-observing sensors aboard the EOS Aqua spacecraft. MODIS is the highest spatial resolution instrument on the Aqua platform with data products generated in 250m, 500m, and 1000m resolutions (nadir). It has 36 spectral bands, a total of 490 detectors, located on four focal plane assemblies (FPAs) with two of them controlled during operation at 83K by a passive radiative cooler. In addition to radiometric calibration and spectral characterization, MODIS spatial performance was extensively characterized pre-launch, including measurements of band-to-band registration (BBR), FPA to FPA registration (FFR), line spread function (LSF), modulation transfer function (MTF), and instantaneous field-of-view (IFOV). The sensor's spatial characterization is monitored by an on-board calibrator, the spectro-radiometric calibration assembly (SRCA). In this paper, we will briefly describe MODIS SRCA spatial characterization methodologies and operational activities. We will focus on the sensor's spatial performance using four years of on-orbit observations and, consequently, evaluate the SRCA's performance. On-orbit results of key spatial characterization parameters (BBR, FFR, and MTF) will be examined and compared to pre-launch measurements and design requirements.