CIRS PREVIEW IMAGES =================== Mark Showalter, PDS Rings Node, September 2009 Adapted from COCIRS_5xxx/BROWSE/BROWINFO.TXT All images are in PNG format. FP1 footprints are always outlined in red; FP3 footprints are in green; FP4 footprints are in blue. Footprints that have smeared by less than 20% of their own size are plotted in bright, fully saturated colors. As the amount of smear increases to 100%, the line weight gets narrower and the color gets darker. Footprints that have smeared by more than 100% are not shown. All lines are plotted with a thin, darker border. This makes it easier to distinguish the boundaries of overlapping footprints, and it also ensures that footprints smeared by nearly 100% remain visible. 1. Saturn Saturn diagrams show two views of the planet, unrolled in simple cylindrical projection. Planetographic latitudes increase uniformly from -90 degrees to 90 degrees along the vertical axis of each diagram. The scale is 0.5 degrees per pixel. A background image of the planet is provided for general reference but has no relationship to the actual locations of atmospheric features at the time of the observation. The top view shows Saturn in a frame fixed relative to the Sun. An accurate shadow boundary is plotted. The horizontal axis is labeled by local time on the planet, with 0h at left and 24h at right. The bottom view shows Saturn in rotating, System III coordinates. The prime meridian is in the middle, and longitude 180 at the right and left edges. Longitudes increase westward, which is leftward in the diagrams. Yellow plus symbols indicate the sub-solar point at the beginning and end of the observation, with a larger plus indicating the end. This location is fixed in the upper panel but shifts due to the rotation of the planet in the lower panel. White plus symbols indicate the sub-spacecraft point at beginning and end. Smaller dots also mark the sub-solar and sub-spacecraft points at each moment when a spectrum was obtained; the locus of these points traces out the path of the Sun and spacecraft above the planet. Openings indicate gaps in the time coverage. Note that many deep sky calibrations begin and end pointed at Saturn but turn elsewhere in between. These can be recognized by the absence of any clear pathway joining the initial and final sub-solar and sub-spacecraft points. 2. Saturn's rings Ring images show a top-down view if the system in a frame fixed relative to the Sun, which is assumed to be shining up from the bottom of the diagram. The shadow of the planet and the dark side of Saturn are rendered accurately, based on the sub-solar latitude at the time of the observation. A simple model of ring brightness vs. radius is shown, so that the locations of familiar ring features can be easily identified. Bright and dark regions change appropriately depending on whether the lit or unlit face of the ring plane is being observed. The direction of ring particle rotation is counterclockwise in the diagram (regardless of which ring face is shown). This means that the morning ansa is at left and the evening ansa is at right. Arrows point toward the sub-solar and sub-spacecraft longitudes. The direction to the Sun is shown in yellow and always points downward. The direction to the spacecraft is shown in white, with a smaller arrow pointing to toward the spacecraft at the beginning of the observation, and a larger one at the end. 3. Moons Moon diagrams show a simple cylindrical map of the body with CIRS footprint locations overlaid. The IAU-defined prime meridian of each map falls in the middle, with longitude 180 degrees at left and right edges. Longitudes increase westward which is leftward in the diagram. Planetographic latitude increases upward in uniform steps from -90 to +90 degree. The scale is 0.5 degrees per pixel. Maps of the bodies have been adapted from those released by the Cassini Imaging team. In the case of bodies for which a map is currently unavailable, a simple texture map of a hypothetical cratered surface serves as the background. The terminators is rendered accurately for the beginning and end times of the observing period. Because a moon rotates slightly over the course of an observation, dark gray defines the region in darkness throughout, whereas a lighter gray defines the regions that went from day to night or night to day during the observation. As with the Saturn diagrams, yellow plus marks and dots describe the sub-solar point during the observation, whereas white plus marks and dots describe the sub-spacecraft point. BROWSE Directory Overview ========================= This directory contains diagrams of CIRS observation footprints atop Saturn and its rings and moons. The files and subdirectories are: BROWINFO.TXT - This file. Subdirectory Filename TARGETS/ IMGyymmddhhmm_FPn.PNG S_RINGS/ RINyymmddhhmm_FPn.PNG SATURN/ POIyymmddhhmm_FPn.PNG MIMAS/ POIyymmddhhmm_FPn_601.PNG ENCELADUS/ POIyymmddhhmm_FPn_602.PNG TETHYS/ POIyymmddhhmm_FPn_603.PNG DIONE/ POIyymmddhhmm_FPn_604.PNG RHEA/ POIyymmddhhmm_FPn_605.PNG TITAN/ POIyymmddhhmm_FPn_606.PNG HYPERION/ POIyymmddhhmm_FPn_607.PNG IAPETUS/ POIyymmddhhmm_FPn_608.PNG PHOEBE/ POIyymmddhhmm_FPn_609.PNG The TARGETS subdirectory contains one diagram for every file of CIRS spectra in the APODSPEC directory. The files follow the same naming scheme as the data files, with the same time tags and focal plane numbers embedded into the names. The diagrams in the "TARGETS" subdirectory are to be considered the default diagrams most likely to be relevant to a user of the data. The footprints are shown atop the nominal target body. For observations not targeted at any particular body, a diagram of Saturn is provided. A large "X" appears in diagrams that contain no CIRS footprints; these are typically sky calibration observations. Because many observations obtain spectra on multiple targets (most commonly Saturn and the rings), additional directories are organized by body. Each of the subdirectories S_RINGS, SATURN and MIMAS to PHOEBE contains files only for that subset of observations that obtained one or more spectra of the named target. In these directories, file names correspond to the associated tables DATA/RINDATA/RIN*.TAB and DATA/POIDATA/POI*.TAB, which contain the information upon which these plots are based. Note that the SPICE body ID is appended to the names of the moon diagrams to reduce the possibility of confusion and to ensure that every file name is unique, regardless of the subdirectory. Subdirectories named after moons are omitted if they would otherwise be empty.