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Instrument Performance

GPI is a complex instrument and the performance is changing quickly with improvements in data reduction and the instrument wavefront sensor control loops. The performance has been broken down into the following areas:


Detector Characteristics

Our understanding of performance and calibration is a work in progress; these pages will continue to be updated as more on sky calibrations are taken and analyzed.



Readnoise plot


Backgrounds (Sky and Thermal)

Sky frames were taken from the 13th-17th of November, 10th December and were reduced using the following primitives:

Subtract Dark Background

Load Wavelength Calibration

Assemble Spectral Datacube

Interpolate Wavelength Axis

The sky flux was then calculated as the median value within each spectral channel, divided by the integration time per coadd (ITIME keyword).



We find that after correcting for distortion, the average positional residual drops from 0.26 spaxels to 0.04 spaxels.

Semester 2014B Time Distribution


The time available on each of Gemini North and South is distributed according to the Observatory partners' shares . To maintain overall balance amongst the partnership, the allocations are adjusted each semester as a result of actual time charged in prior semesters. The allocations are approved at the Operations Working Group meeting prior to the Call. Historically, around 5% of each semester's science time is used to complete highly ranked programs from the previous two semesters to which the ITAC granted rollover status.

Semester 2014B Important Dates

Key dates and events in the proposal process are shown below. The Phase I and Phase II deadlines are highlighted.

2014B Instrument Availability and Target Accessibility

This page provides best estimates, at the time of the Call for Proposals, of instrument availability and target (RA, dec) restrictions for 2014B.


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Spectroscopic Accuracy

Spectroscopic Accuracy

The spectroscopic accuracy has been evaluated using the white dwarf orbiting HD 8049 discovered by Zurlo et al (2013), believed to have a temperature of 18800+/-2000 K. Observations were performed during the second commissioning run on December 12, 2013. The recipes, calibration files, and reduced cubes used to create the plots in this section are available as part of the first light data release. For this data, zero-point offsets to the wavelength solutions were determined using an Argon arclamp image taken immediately after the exposures.

Limiting magnitudes for instrument and internal wavefront sensors

GPI limiting magnitudes are determined by several components, the AO WFS (I-band), the LOWFS (H-band), and the IFS (selected filter). In addition the observing conditions add another layer of limits. Thus the brightest of the science object is limited in I band from the AOWFS, in H-band from the LOWFS (not a constraint in DIRECT mode as then no coronographic mask is used and no LOWFS is possible). 


For faint targets(I magnitude ≤9.0), GPI is expected to achieve 5-σ sensitivity at H=21 in one hour in spectroscopic mode. Achieved sensitivity is a function of many parameters, including contrast, inner working distance, brightness of the central star (if any), observing mode (dithered, sky-offset, sky-rotation) and it is not yet possible to provide estimates for all modes.