Tagliaferri, GianpieroGianpieroTagliaferriMoretti, AlbertoAlbertoMorettiCampana, SergioSergioCampanaTamburelli, F.F.Tamburelli2020-09-172020-09-172004-02-01https://hdl.handle.net/20.500.13025/225X-Ray and Gamma-Ray Instrumentation for Astronomy XIII. Edited by Flanagan, Kathryn A.; Siegmund, Oswald H. W. Proceedings of the SPIE, Volume 5165, pp. 241-250 (2004).The Swift X-ray Telescope (XRT) is designed to make astrometric, spectroscopic and photometric observations of the X-ray emission from Gamma-ray bursts and their afterglows, in the energy band 0.2 - 10 keV. Here we report first results of the analysis of Swift XRT effective area at five different energies as measured during the end-to-end calibration campaign at the Panter X-ray beam line facility. The analysis comprises the study of the effective area both on-axis and off-axis for different event grade selection. We compare the laboratory results with the expectations and show that the measured effective area meets the mission scientific requirements.10.1117/12.504835http://adsabs.harvard.edu/abs/2004SPIE.5165..241T2004SPIE.5165..241T