This page presents throughput curves in graphic and tabular form. These data have been generated with Pysynphot and are the transmission at launch in March 2002. The total throughputs represent the fractional photon detection efficiency in terms of photons in vs. detected photo-electrons. The variation with time is documented by Bohlin, Mack, and Ubeda (2011, hereafter ISR-III). This time variability is incorporated in the Quantum Efficiency (QE) ACS instrument component file; and the amount of change with time is summarized by the changes in the flux calibration keyword PHOTFLAM in Table 7 of Bohlin (2012, hereafter ISR-IV). For example, the maximum change for WFC over its initial operational period from 2002.16 to 2007.1 at the loss rate of 0.26/year is 1.3% for six filters in Table 1 of ISR-III. After SM4 in 2009 May, the sensitivity drops by at most another 0.7% for a total loss of 2.0% in F550M. This change is reflected in the PHOTFLAM change from 3.906e-19 to 3.984e-19 in Table 7 of ISR-IV. Also, see the ACS Zeropoints web page.
If desired, more accurate throughput curves for a particular time may be acquired by using Pysynphot in the following way:
# The first line applies within STScI only.
# set this environment variable to the root directory where you have installed
# Pysynphot's reference files.
setenv PYSYN_CDBS /grp/hst/cdbs/
>>> import pysynphot as S
# Generate a bandpass for an observational setup and time (in MJD).
>>> bp = S.ObsBandpass ('acs,wfc1,f606w,mjd#52340')
# Now, bp.wave and bp.throughput are the wavelength and transmission
# arrays, respectively.
Please consult the Pysynphot Documentation for more details.
ACS Throughput Tables
Calibration of the ACS CCD Cameras III. Sensitivity Changes over Time,
Bohlin, R. C., Mack, J., & Ubeda, L. 2011, Instrument Science Report, ACS
2011-03, (Baltimore:STScI), ISR-III