The first release of data from the Herschel ATLAS: the SPIRE images
  We have reduced the data taken with the Spectral and Photometric Imaging
Receiver (SPIRE) photometer on board the Herschel Space Observatory in the
Science Demonstration Phase (SDP) of the Herschel Astrophysical Terahertz Large
Area Survey (H-ATLAS). We describe the data reduction, which poses specific
challenges, both because of the sheer size of the data, and because only two
scans are made for each region. We implement effective solutions to process the
bolometric timelines into maps, and show that correlations among detectors are
negligible, and that the photometer is stable on time scales up to 250 s. This
is longer than the time the telescope takes to cross the observed sky region,
and it allows us to use naive binning methods for an optimal reconstruction of
the sky emission. The maps have equal contribution of confusion and white
instrumental noise, and the latter is estimated to 5.3, 6.4, and 6.7 mJy/beam
(1-{\sigma}), at 250, 350, and 500 \mu{m}, respectively. This pipeline is used
to reduce other H-ATLAS observations, as they became available, and we discuss
how it can be used with the optimal map maker implemented in the Herschel
Interactive Processing Environment (HIPE), to improve computational efficiency
and stability. The SDP dataset is available from http://www.h-atlas.org/.
