Ike Pono

Ike Pono is a 1kx1k infrared detector aimed at ultra-low flux astronomical imaging. It provides avalanche gain at these very low photon flux levels and consequently sets a new standard in sensitivity for astronomy. This allows fainter objects to be observed and shorter integration times for the same signal-to-noise, thereby maximizing the science return on large telescopes. Many future astronomy projects depend on photon counting level sensitivity, including imaging faint objects and spectral lines.

Ike Pono is the product of many years of research and development alongside the University of Hawaii, Institute of Astronomy on avalanche photodiode sensors for astronomical imaging. The aim is to perform long integration times and uses multiple non-destructive readout frames, so minimizing the self-luminescence (glow) is an important objective. Extensive reference pixels and outputs are designed to control drift in long exposures.

Despite 15-micron pixel size, the crosstalk and inter-pixel capacitance are very low due to the mesa architecture of the photodiode array. The array is not designed for high-speed readout but can achieve 32 frames per second with 16 parallel outputs.

The HgCdTe avalanche photodiodes determine the performance of the Ike Pono detector and is under continuous development with the University of Hawaii. Currently, an avalanche gain of 10x can be applied at the photon arrival rate of 1 photon per 100 seconds per pixel. This same detector has a dark current of 1e-3 electrons per second per pixel at 70 K. A read noise of 1 electron rms has been measured, setting a new standard in sensitivity by almost an order.