SS Science Weekly Highlight

Title: IRAD laboratory demonstration of IR detector stability for future exoplanet missions —- POC: Tom Greene (SSA) Short story:  

Thomas Greene (ARC Code SSA) has directed an Ames IRAD project to develop a mid-infrared densified pupil spectrograph testbed through its first year of activity. The project goal is to measure and demonstrate system stability sufficient for measuring the atmospheric compositions of Earth-like planets transiting M stars. Completing this work is crucial for demonstrating the feasibility of the Origins observatory which is under study by NASA SMD APD for development in the 2020s and completion in the 2030s.

Highlights of the past year include:

1. Professor Taro Matsuo is visiting from Osaka University in Japan and has designed and fabricated the densified pupil optical testbed system at a cost of over $400 K paid by Japanese grants.

2. Roy Johnson (ARC Code SGG) has refurbished the Ames mid-IR detector lab dewars and data system in building N244.

3. Selected, tested, and re-characterized a flight-like mid-infrared detector for the experiment. Ames originally developed this detector for the James Webb Space Telescope (JWST) over 15 years ago. Significantly, T. Matsuo has demonstrated detector stability of ~20 ppm, better than achieved on-orbit with SPitzer which used similar Si:As IBC detectors.

4. Refurbished a large (~0.4 x 0.5-m working volume) liquid nitrogen and helium laboratory test dewar that we will use to house the densified pupil testbed. This has been a difficult process and has been supported by the SS Airborne Instrument lab (E. QUigley), the Ames metal shop, ARC Code RE, code SGG (R Johnson), and MEI contract personnel (B. Helvenstein & A.  Kashani).

           Detector system:                                                                                                


        Ames N244 detector system (left and center) operates the SB226 Si:As detector (right).
Achieved stability is ~20 ppm for the detector itself!

Refurbished Laboratory  Dewar

                                                                   Densified pupil testbed (T. Matsuo)

The project is currently starting full systems integration, involving integrating the mid-IR detector with the optical system and then integrating that assembly and a blackbody thermal source into the large lab dewar. We hope to start system testing in May and complete all testing and analysis by October 1. However, work is slowed somewhat by late arrival of FY19 IRAD funds. We very much appreciate the support the SS DIvision has given to this project, which has been crucial for its progress.

These efforts have helped rebuild ARC capabilities in mid-IR detectors and cryogenic systems. The refurbished detector and dewar systems and refreshed technical experience should help Ames win and complete related projects in the future.

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