Posted by Bruce Woodgate on June 15, 1999 at 15:25:42:
I would suggest that WFC3 has clear filters to provide a mode with maximum light gathering power. Such a mode has proved useful for STIS, for example for the following studies; Morphology of the faintest galaxies - the STIS image of the HDF-south reaches fainter galaxies than any other image. Gamma Ray bursts - the gamma ray burst themselves can be followed to later times to obtain light curves, and the existence and structure of their host galaxies determined. Protoplanetary disks - fainter disks can be found by including all the light, and the diffracted starlight background is smoother and easier to remove than with R~5 filters. (This presumes there would also be an occulting device included, a pseudo-coronograph). Gravitational lensed arclets - fainter arclets could be seen, but this might be countered by the distinctive color differences seen in some arclets relative to the lensing cluster galaxies. There are probably other examples I don't know about. Why provide this for WFC3 when it is on STIS? WFC3 will have a wider field and higher sensitivity, and I think higher resolution (better sampling). STIS could have failed by then. Its CCD will be severely beaten up by then by trapped particles, vastly increasing its hot pixels and decreasing its CTE. In addition I support the medium resolution filters for photometric redshifts. Bruce Woodgate.