  The planetary system discovered around the young A-type HR8799 provides a
unique laboratory to: a) test planet formation theories, b) probe the diversity
of system architectures at these separations, and c) perform comparative
(exo)planetology. We present and exploit new near-infrared images and
integral-field spectra of the four gas giants surrounding HR8799 obtained with
SPHERE, the new planet finder instrument at the Very Large Telescope, during
the commissioning and science verification phase of the instrument
(July-December 2014). With these new data, we contribute to completing the
spectral energy distribution of these bodies in the 1.0-2.5 $\mu$m range. We
also provide new astrometric data, in particular for planet e, to further
constrain the orbits. We used the infrared dual-band imager and spectrograph
(IRDIS) subsystem to obtain pupil-stabilized, dual-band $H2H3$ (1.593 $\mu$m,
1.667 $\mu$m), $K1K2$ (2.110 $\mu$m, 2.251 $\mu$m), and broadband $J$ (1.245
$\mu$m) images of the four planets. IRDIS was operated in parallel with the
integral field spectrograph (IFS) of SPHERE to collect low-resolution
($R\sim30$), near-infrared (0.94-1.64 $\mu$m) spectra of the two innermost
planets HR8799d and e. The data were reduced with dedicated algorithms, such as
the Karhunen-Lo\`eve image projection (KLIP), to reveal the planets. We used
the so-called negative planets injection technique to extract their photometry,
spectra, and measure their positions. We illustrate the astrometric performance
of SPHERE through sample orbital fits compatible with SPHERE and literature
data.
