GFP-IFS: a coronagraphic integral field spectrograph for the APO 3.5-meter telescope

We present the design and initial laboratory tests of a new integral-field spectroscopy mode to be added to the Goddard Fabry-Perot instrument at Apache Point Observatory. This new IFS mode incorporates a 'TIGER'-style lenslet array, with pre-optics to allow spatial sampling of 0.21 or 0.42 arcseconds, corresponding to fields-of-view of 7 or 14 arcseconds. For coronography, we insert a mask close to the lenslet array focal plane, blocking a discrete number of the lenslet foci. Three VPH grisms will be available to disperse the spectra, with medium-resolution (R~1000) red (λ ~ 660nm) and green (λ ~ 490nm) modes and a high-resolution (R~5000) red mode. We show that it is possible to reduce crosstalk between spectra by at least an order of magnitude by placing a pinhole mask at the focus of the lenslet array, and present data on the throughput of the lenslets and VPH grism.