NICI has a specialized dual-channel camera with
campaign. The GSC has organized the Planet Finding
a dedicated Lyot coronagraph and an 85-element
Science Working Group and charged it to review NICI
curvature adaptive optics system optimized to directly
performance prior to beginning the NICI Campaign.
detect
planets
The working group and the GSC met in September
around nearby stars. NICI spectrally differences two
massive
and October to review NICI performance and provide
images taken simultaneously at two slightly different
feedback to Gemini and the campaign team.
wavelengths
self-luminous
bracketing
the
extrasolar
strong
near-infrared
methane features found in substellar (planet-mass)
The GSC defined two basic criteria to establish NICI’s
objects. The NICI design philosophy tightly integrates
performance. The first is that NICI must be capable
the three major subsystems (AO system, coronagraph,
of achieving the science goals set out in the campaign
and dual-channel camera) to minimize non-common
proposal submitted by Liu’s team. The campaign
path aberrations so that planets will not be confused
proposal was based on certain performance estimates
with diffracted speckles produced by the optics in the
and assumptions defined by Gemini as part of the
instrument itself. Both cameras are equipped with 1024
campaign Request for Proposals (RFP) more than two
× 1024 ALADDIN InSb (indium antimonide) arrays
years ago. To go forward with the campaign, Gemini
sensitive from 1 to 5 microns. The imaging plate scale
must first establish that NICI performs at least as well
is 0.018 arcsecond per pixel, providing a field of view
as anticipated in the RFP. Secondly, NICI must perform
18 arcseconds across. A variety of broad- and narrow-
at least as well as NIRI + Altair, Gemini’s comparable
band filters are available, including various narrow
AO imager without an optimized coronagraph. The
band filters sampling the methane absorption band at
best measurements to date using NIRI and Altair were
1.6 microns.
made by the Gemini Deep Planet Search (GDPS) team under the leadership of David Lafrenière and René
NICI will be the first Gemini instrument to be used
Doyon (and described in volume 670 of the Astrophysical
in “campaign” mode. A dedicated program has been
Journal, page 1367) as well as an article on page 31 of this
awarded up to 50 nights over three years to look
issue of GeminiFocus.
for extrasolar planets. Campaign observations are
Figure 1.
planned to start before the end of 2008. NICI is also being offered for non-exoplanet AO imaging and coronagraphy starting in 2009A. While the instrument characterization has not been completed yet, the measured performance for some observing modes exceeds specifications. At present, NICI is being offered for 1- to 2.5-micron coronagraphic imaging on targets closer than 1 parsec (pc), or more distant than 200 pc with guide stars brighter than V = 11 magnitude. This restriction is to allow non-exoplanet research on a shared-risk basis during 2009A; full open access will be offered in 2009B once NICI has been fully characterized and the planet search campaign has begun. When the Gemini Board of Directors authorized an allocation of up to 50 nights to the NICI Planet Search team led by Michael Liu and Mark Chun (University of Hawai‘i), and Laird Close (University
During commissioning, the NICI instrument team
of Arizona), they required that the Gemini Science
found that Strehl ratios at 1.6 microns were typically
Committee (GSC) provide technical oversight of the
35% to 40% during median or better seeing, matching
campaign on an annual basis. They also required that
expectations for guide stars brighter than V = 13
the GSC assess NICI performance prior to starting the
magnitude as a function of natural seeing and guide star
December2008
The NICI contrast curves derived with the campaign pipeline reduction software. These contrast curves show the achieved contrasts compared to the original RFP expectations scaled to a twohour exposure. For reference, two contrast curves from NIRI are also shown scaled to the same integration time. (Figure adapted from M. Chun et. al. 2008, Proc. SPIE and using data from D. Lafrenière et. al., 2007. The preliminary NICI contrast curve was derived from commissioning data by Zahed Wahhaj, Mike Liu, and the NICI Campaign Team.)
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