The Time and Performance Estimator (TaPE) is a tool to predict the global and differential astrometry performance of SIM Lite as a function of object characteristics (e.g. apparent brightness, color) and the SIM Lite instrument parameters (e.g. integration time, observing cadence). The tools allow the user to answer such questions as "How well can SIM Lite measure the parallax to star A in X hours?" or "How well can SIM measure the potential wobble in star B if it integrates for Y minutes?"

TaPE includes three estimators: GATE (Global Astrometry Time Estimator), GAPE (Global Astrometry Performance Estimator), and DAPE (Differential Astrometry Performance Estimator). The time estimator (GATE) will estimate the time required to achieve a given performance. The performance estimators (GAPE and DAPE) start with the observing time and estimate the resulting observation performance (accuracy) that can be obtained. By switching back and forth between modes, the user can evaluate the tradeoffs between performance objectives and the observing time required to attain them. TaPE can also be used to evaluate tradeoffs between integration time and the number of visits to a particular source.