Development of High Contrast Lenslets for Integral Field Spectroscopy

A key goal of NASA's Exoplanet Exploration Program (ExEP) is to discover Earth-like exoplanets and to determine their spectra for spectral signatures of life. Toward that goal there is on-going development of several competing architectures for how to suppress the starlight and achieve the high contrast necessary to directly image an Earth-like planet in the habitable zone around a nearby star, including coronagraphs, external occulters, and nulling interferometers operating at optical wavelengths.

Regardless of the starlight suppression technology chosen, any future planet imaging mission must have a highly capable science instrument able to perform both imaging and spectroscopy in order to detect and characterize the target planets.  The ideal instrument for making these measurements is an integral field spectrograph (IFS), an instrument that obtains a spectrum at every spatial element in the field of view.  The current state of the art for these instruments does not yet achieve the challenging performance requirements needed for imaging of Earth-like exoplanets due to a variety of challenging systematics. In particular, current lenslet designs introduce too high a level of crosstalk between adjacent spectra to operate at very high contrasts.

In space, an IFS science camera will be used to investigate the properties of exoplanets while monitoring and diagnosing wavefront errors introduced by the telescope optical assembly.

This research will develop a critical technology needed to build a prototype IFS to advance coronagraphy and extreme wavefront sensing and control algorithms in NASA's High Contrast Imaging Testbed (HCIT).  Once built, this laboratory IFS will be used as a facility class instrument within the HCIT.

The work builds upon awards from the FY12 IRAD program and the Nancy Grace Roman Technology Fellowship program.

As part of those programs, NASA Goddard Space Flight Center designed the Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies (PISCES) integral field spectrograph to be integrated into the JPL HCIT.  However, during this the design phase, it became apparent that even though lenslet-based integral field spectrographs exist on the ground, high contrast lenslet arrays are still at a low TRL.   This work will design, model, fabricate, and performance assess a specialized lenslet array in order to meet the requirements of a high contrast imaging mission.