On orbit Sensitivity of ACS

Sirianni,M., De Marchi, G., Gilliland, R., Mack, J., Pavlovsky, C., the ACS photometric calibration working group, the ACS science team, and the STScI ACS team

We present the results of the on-orbit measurement of the sensitivity of each camera. The instrument throughput was measured by observing spectrofotometric standard stars in all bandpasses. Data were analyzed with standard photometric softwares in order to measure the Encircled Energy profile and to determine the absolute photometric calibration. We discuss comparisons with prelaunch estimates of response curves models and present the new sensitivity curves implemented in SYNPHOT. Finally, we present the preliminary photometric transformations between the WFC and HRC.

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