Seeing the Sky throughHubble’s Eye: The COSMOS SkyWalker

Large, high-resolution space-based imaging surveys produce a volume of datathat is difficult to present to the public in a comprehensible way. Whilemegapixel-sized images can still be printed out or downloaded via the WorldWide Web, this is no longer feasible for images with 10^9 pixels (e.g., theHubble Space Telescope Advanced Camera for Surveys [ACS] images of the GalaxyEvolution from Morphology and SEDs [GEMS] project) or even 10^10 pixels (forthe ACS Cosmic Evolution Survey [COSMOS]). We present a Web-based utilitycalled the COSMOS SkyWalker that allows viewing of the huge ACS image data set,even through slow Internet connections. Using standard HTML and JavaScript, theapplication successively loads only those portions of the image at a time thatare currently being viewed on the screen. The user can move within the image byusing the mouse or interacting with an overview image. Using an astrometricallyregistered image for the COSMOS SkyWalker allows the display of calibratedworld coordinates for use in science. The SkyWalker "technique" can be appliedto other data sets. This requires some customization, notably the slicing up ofa data set into small (e.g., 256^2 pixel) subimages. An advantage of theSkyWalker is the use of standard Web browser components; thus, it requires noinstallation of any software and can therefore be viewed by anyone across manyoperating systems.Comment: 4 pages, 2 figures, accepted for publication in PAS