ACTIVITY TITLE: UVIS Photometric Zero Points
ID: WFC3-037 (11450)
APPLICABLE SMOV REQUIREMENTS: WFC3 will provide high photometric
performance over the full wavelength range covered by the instrument, with filter
limiting magnitudes of at least 25.5 (U), 26.4 (B), 27.1 (V), 26.3 (R), and 26.1 (I) mag.
WFC3 will provide high photometric stability, with the variation over 1 month being less
than 5% at 200-300 nm, less than 3% at 300-400 nm, and less than 1% from 400-1000
nm.
DESCRIPTION: Observe one of three photometric standards (G191B2B, GD153, or
GD71), depending upon time of year, in each of the 16 priority-1 filters (F218W, F225W,
F275W, F300X, F336W, F350LP, F390W, F438W, F475W, F475X, F555W, F600LP,
F606W, F625W, F775W, F814W), 20 priority-2 filters (F280N, F343N, F373N, F390M,
F395N, F410M, F467M, F469N, F487N, F502N, F547M, F621M, F645N, F656N,
F658N, F673N, F689M, F763M, F845M, F953N) and any additional filters used in
EROs. Obtain two short images in each of these filters, using subarrays, with a small
dither (~10.5 pixels) between exposures, allowing rejection of cosmic rays and detector
artifacts. To monitor stability in 6 key filters (F225W, F336W, F438W, F555W, F606W,
F814W), a subset of these observations will be repeated on timescales of 1, 7, and 30
days.
IMPLEMENTATION METHOD: Phase II and SMS.
DEPENDENCIES: WFC3-14 (Shutter test) and WFC3-21 (UVIS Fine Alignment)
DURATION: 10 orbits
DATA REQUIREMENTS: 116 800x800 pixel images.
ANALYSES & EXPECTED RESULTS: Aperture photometry and comparison to
expectations from both thermal vacuum tests and component throughputs.
COMMENTS: None.
AUTHOR/telephone/email: Tom Brown tbrown@stsci.edu x4902
DATE: 12/11/07