Posted by John Trauger on June 24, 1999 at 15:05:25:
Here is a strawman filter proposal for the atmospheres of giant planets and brown dwarfs -- a set of three quad filters as follows -- (1) UVIS CH4 abs/cntm pairs 619, 619(+/-), 893, 935 nm (2) UVIS CH4 narrowband 889, 904, 922, 937 nm (FWHM < 0.01*center wavelength) (3) NIR CH4 abs/cntm pairs 1080, 1130, 1580, 1710 nm This selection of planetary science passbands is offered for further discussion by the HST user community. It has been distilled from an informal email survey distributed in May 1999 to a number of planetary scientist who are past users of HST data, and came from the following tabulation of their preferences. ------------------------------------------------------ Preferences Wavelength(nm) Comments ------------------------------------------------------ K 1350 longpass rings and satellites B C K M S W 1710 CH4 B M S W 1650 cntm B C K 1580 cntm B M 1480 NH3, H2O, Galileo/NIMS K M S W 1130 CH4 NIC1 K M S W 1080 cntm NIC1 B C K R S W 935 cntm ~0.02/km-am B K R W 922 CH4 ~0.3/km-am B K R W 904 CH4 ~3/km-am B C H K R S W 893 CH4 ~30/km-am, WFPC2 B K 727 CH4 WFPC2 B H K R W 619 CH4 WFPC2 W 619(+/-) dual-passband continuum, Cassini B R 635 cntm 543 CH4 WFPC2 B 200 photometry B 350 photometry ------------------------------------------------------ Voting -- (and thanks to all for communicating your preferences) B = Kevin Baines C = Nancy Chanover H = Heidi Hammel K = Erich Karkoschka M = Mark Marley (cool brown dwarfs) R = Kathy Rages S = Amy Simon W = Bob West ------------------------------------------------------ There were various opinions on the choice of continuum wavelength companion for the 1.71 micron filter, here we have taken Karkoschka's advice and selected 1.58 microns. The suggested broadband filters are already accounted in the WFC3 set of photometry filters in the UV and NIR. Bob West suggests a Cassini-style dual-passband continuum filter for the 619 nm band. The 619(+/-) filter simultaneously transmits the continuum wavelengths on both sides of the 619 absorption feature, while blocking the 619 absorption band itself. Since it is likely there will be space for up to two UVIS and one NIR filter for methane/planetary science, the list was reduced to 12 passbands distributed into three quad filters, each quad element covering an FOV larger than Jupiter. Multiple filter elements, four to each (quad) filter, each provide about 70 arcsecond square fields of view in the UVIS camera, and somewhat smaller (TBD) FOVs in the NIR camera. HST pointing offsets would be used to select among the four filter elements, as is done for the WFPC2 quads. Rapid absorption/continuum exposure pairs could be facilitated via filter selection, rather than telescope pointing, by placing each CH4 and its corresponding continuum passband in the same quad position on two different filters. Rapid subframe readouts of just one quadrant of the CCD can also be used to help keep the absorption/continuum pairs close together in time. - John Trauger (on behalf of the WFC3 SOC)