Spectro-Polarimetric High-contrast Exo-planet REsearch


SPHERE Observing Modes

The primary observing modes of SPHERE a re summarized in the table below:

ModeSub-ModeDescriptionScience case
Module/Spectral RangeDe-rotatorSet-up/options
IRDIFS NIRSUR Simultaneous IFS(Y-J) + IRDIS/DBI (H) pupil stab. Dedicated coronograph Large survey for exo-Planet detection in NIR, hundreds of targets
NIR OBS pup. or field stab. any or no coronagraph Specific characterization with IRDIS and IFS
IRDIS alone DBI Dual band Imaging, any filter pair Y-Ks Pupil or field stab. Any or no coronagraph Characterization of companions in outer field, confirmations
DPI Dual Polarimetric Imaging Field (pseudo) stabilized or fixed Any or no coronagraph
Polarized circumstellar sources, e.g. disks
LSS Long Slit Spectroscopy Field stab. Low or medium resolution Characterization of known companions
CI Classical Imaging
Any BB/NB filter, Y-Ks
Pupil or field stab. Genral use NIR high-res imaging
ZIMPOL alone P1 High-precision relative polarimetry
Any BB/NB filter
fixed (i.e. no de-rotation at all) Any or no cornagraph
Highest precision polarimetry mode
P1 Polarimetry mode with de-rotation
Any BB/NB filter
Field stab. Any or no cornagraph
High precision polarimetry mode for fainter targets
P3 Polarimetry with de-rotator close to P1 position
Any BB/NB filter
"pseudo" field stab.
(single integrations stabilized)
Any or no cornagraph
High precision polarimetry with reduced de-rotator polar and cross-talk
I Imaging
Any BB/NB filter
Field stab. or de-rotator fixed Same or distinct filters in 2 arms
Any or no coronagraph
CP HWP out, modulation off
High-res imaging in the visual, differential NB imaging

The NIR survey mode is the main observing mode which will be used for ~80% of the observing time. It combines IRDIS dual imaging in H band with imaging spectroscopy using the IFS in the Y-J bands. This configuration permits to benefit simultaneously from the optimal capacities of both dual imaging over a large field (out to ~5" radius) and spectral imaging in the inner region (out to at least 0.7" radius). In particular, it allows to reduce the number of false alarms and to confirm potential detections obtained in one channel by data from the other channel. This will be a definitive advantage in case of detections very close to the limits of the system.

The NIR characterization mode, in which IRDIS is used alone in its various modes, will allow obtaining observations with a wider FOV in all bands from Y to short-K, either in dual imaging or dual polarimetry, or in classical imaging using a variety of broad and narrow-band filters. This will be especially interesting in order to obtain complementary information on already detected and relatively bright targets (follow-up and/or characterization). Spectroscopic characterization at low or medium resolution will be possible in long-slit mode. Additional science cases will also benefit from these observing modes (disks, brown dwarfs, etc.).

The visible search and characterization mode, will benefit from ZIMPOL polarimetric capacities to provide unique performance in reflected light very close to the star, down to the level required for the first direct detection in the visible of old close-in planets, even if on a relatively small number of targets. ZIMPOL also provides classical imaging in the visible, offering unique high-Strehl performance.

mfeldt.php, 08/2007