... The substepping technique is used for the Hubble Space Telescope (HST) imaging to cope with the problem of undersampling and to improve resolution. ... For the HST, undersampling means that the size of the pixel in a camera is larger than the critical value determined by the optics of the telescope, and aliasing takes place. ... Sampling is an operation to integrate a ( x ) within a pixel, and to assign the result to this pixel (Figure 1 A). ... Figure 1: Substepping ( N =2) and normal sampling. ...

... The INTEGRAL Science Data Centre Roland Walter, Alain Aubord, Paul Bartholdi, Jurek Borkowski, Pierre Bratschi, Tomaso Contessi, Thierry Courvoisier, Davide Cremonesi, Pierre Dubath, Donnald Jennings, Peter Kretschmar, Tim Lock, St’ephane Paltani, Reiner Rohlfs and Julian Sternberg 1 INTEGRAL Science Data Centre, Chemin d' ’ Ecogia 16, CH--1290 Versoix, Switzerland Abstract. INTEGRAL is a gamma­ray observatory mission of the Eu­ ropean Space Agency to be launched in 2001. ...

IRAF/STECF 2-D spectrum point source / background decomposition package . ... The general problem is one of spectral decomposition - of separating the spectra of the point sources from the background. ... The STECF IRAF layered package "specres" provides two tasks to extract point source spectra from 2-D images (either longslit, multislit or cross-dispersed) and decompose the full background over the image. ... A Point Source Function spectrum image is required as a 2-D spectrum. ...