Four megapixel sensor for ultra-low-background shortwave infrared astronomy

A six-meter space telescope optimized for exoplanet direct imaging and spectroscopy is the highest priority mission identified by the 2022 Decadal survey. The science goals of this mission are positive identification and spectroscopic classification of ~25 exo-Earths, to determine if they possess atmospheres suitable for life. Multiple studies have demonstrated that detector noise is the most serious impediment to such missions, as typical flux rates at the pupil of a space telescope are a few photons per square meter per hour through a typical 10% bandpass filter. Proposed mission concepts such as HabEx required detector dark currents less than a few electrons per hour and read noise at sub-electron levels. There are no current large-format (eg, suitable for spectroscopy) infrared detectors capable of meeting these noise requirements. This is critical to achieve, as the deepest spectral features lie at infrared wavelengths, with deep molecular features including from biosignature gases like carbon dioxide, water, and methane. The read noise of the workhorse HxRG detectors is far too high for such science, as it is ~13 e-/pix/frame, reducible to ~3 e-/pix/frame by averaging. This has not been significantly improved in three decades, and there is no imminent path to overcoming this read noise barrier. For the last several years, with NASA support, we have been maturing an alternate technology, HgCdTe linear-mode avalanche photodiode (LmAPD) arrays, which reduce effective read noise through noiseless avalanche multiplication of the signal charge within the photodiode. Our latest LmAPDs are 1 megapixel sensors which show encouraging performance, with read noise reducible to sub-electron levels and dark currents consistent with zero (several electrons per day, upper limit). The goals of this award are to develop a large format (4 megapixel) array capable of these challenging exoplanet spectroscopy observations and advance its Technology Readiness Level (TRL) to TRL4. Such a detector would also be a compelling choice for other priority science cases, like space-based spectroscopy of faint galaxies, precision photometry, and ground-based high-resolution infrared spectroscopy. Using lessons learned from the development of the 1 megapixel devices, we propose to develop with our industrial partners a similar ultra-low background 4 megapixel sensor. We propose to undertake a three-step development process, including designing the bare ROICs, prototype engineering-grade sensors, and science-grade sensor based on lessons-learned. We propose to upgrade an existing test camera to allow operation of these new 4 megapixel arrays at low background at both the laboratory and at the telescope. This camera is operated similarly to space infrared cameras, using TRL-9 readout hardware. We will develop sensor controller firmware and software as part of this task. We will use this test camera to characterize these devices at the limit of their performance, including initial testing on-sky. We will report dark current, readout noise, glow, and a range of other important detector parameters.

The Strategic Astrophysics Technology program (SAT) supports focused development efforts for key technologies to the point at which they are ready to feed into major missions in the three science themes of the Astrophysics Division: Exoplanet Exploration, Cosmic Origins, and the Physics of the Cosmos. This program is specifically designed to address middle technology readiness level (TRL) "gaps" between levels 3 and 6: the maturation of technologies that have been established as feasible, but which are not yet sufficiently mature to incorporate into flight missions without introducing an unacceptable level of risk.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.