John Robertson Tower

The solar orbiter imager (SoloHI) instrument for the Solar Orbiter mission

The SoloHI instrument for the ESA/NASA Solar Orbiter mission will track density fluctuations in the inner heliosphere, by observing visible sunlight scattered by electrons in the solar wind. Fluctuations are associated with dynamic events such as coronal mass ejections, but also with the “quiescent” solar wind. SoloHI will provide the crucial link between the low corona observations from the Solar Orbiter instruments and the in-situ measurements on Solar Orbiter and the Solar Probe Plus missions. The instrument is a visible-light telescope, based on the SECCHI/Heliospheric Imager (HI) currently flying on the STEREO mission. In this concept, a series of baffles reduce the scattered light from the solar disk and reflections from the spacecraft to levels below the scene brightness, typically by a factor of 1012. The fluctuations are imposed against a much brighter signal produced by light scattered by dust particles (the zodiacal light/F-corona). Multiple images are obtained over a period of several minutes and are summed on-board to increase the signal-to-noise ratio and to reduce the telemetry load. SoloHI is a single telescope with a 40⁰ field of view beginning at 5° from the Sun center. Through a series of Venus gravity assists, the minimum perihelia for Solar Orbiter will be reduced to about 60 Rsun (0.28 AU), and the inclination of the orbital plane will be increased to a maximum of 35° after the 7 year mission. The CMOS/APS detector is a mosaic of four 2048 x 1930 pixel arrays, each 2-side buttable with 11 μm pixels.

Development and test of an active pixel sensor detector for heliospheric imager on solar orbiter and solar probe plus

The Naval Research Laboratory is developing next generation CMOS imaging arrays for the Solar Orbiter and Solar Probe Plus missions. The device development is nearly complete with flight device delivery scheduled for summer of 2013. The 4Kx4K mosaic array with 10micron pixels is well suited to the panoramic imaging required for the Solar Orbiter mission. The devices are robust (<100krad) and exhibit minimal performance degradation with respect to radiation. The device design and performance are described.

NV-CMOS HD camera for day/night imaging

SRI International (SRI) has developed a new multi-purpose day/night video camera with low-light imaging performance comparable to an image intensifier, while offering the size, weight, ruggedness, and cost advantages enabled by the use of SRI’s NV-CMOS HD digital image sensor chip. The digital video output is ideal for image enhancement, sharing with others through networking, video capture for data analysis, or fusion with thermal cameras. The camera provides Camera Link output with HD/WUXGA resolution of 1920 x 1200 pixels operating at 60 Hz. Windowing to smaller sizes enables operation at higher frame rates. High sensitivity is achieved through use of backside illumination, providing high Quantum Efficiency (QE) across the visible and near infrared (NIR) bands (peak QE <90%), as well as projected low noise (<2h+) readout. Power consumption is minimized in the camera, which operates from a single 5V supply. The NVCMOS HD camera provides a substantial reduction in size, weight, and power (SWaP) , ideal for SWaP-constrained day/night imaging platforms such as UAVs, ground vehicles, fixed mount surveillance, and may be reconfigured for mobile soldier operations such as night vision goggles and weapon sights. In addition the camera with the NV-CMOS HD imager is suitable for high performance digital cinematography/broadcast systems, biofluorescence/microscopy imaging, day/night security and surveillance, and other high-end applications which require HD video imaging with high sensitivity and wide dynamic range. The camera comes with an array of lens mounts including C-mount and F-mount. The latest test data from the NV-CMOS HD camera will be presented.

Low-light NV-CMOS image sensors for day/night imaging

Traditionally, daylight and night vision imaging systems have required image intensifiers plus daytime cameras. But SRI’s new NV-CMOS™ image sensor technology is designed to capture images over the full range of illumination from bright sunlight to starlight. SRI’s NV-CMOS image sensors provide the low light sensitivity approaching that of an analog image intensifier tube with the cost, power, ruggedness, flexibility and convenience of a digital CMOS imager chip. NV-CMOS provides multi-megapixels at video frame rates with low noise (<2 h+), high sensitivity across the visible and near infrared (NIR) bands (peak QE <85%), high resolution (MTF at Nyquist < 50% @ 650 nm), and extended dynamic range (<75 dB). The latest test data from the NV-CMOS imager technology will be presented. Unlike conventional image intensifiers, the NV-CMOS image sensor outputs a digital signal, ideal for recording or sharing video as well as fusion with thermal imagery. The result is a substantial reduction in size and weight, ideal for SWaP-constrained missions such as UAVs and mobile operations. SRI’s motion adaptive noise reduction processing further increases the sensitivity and reduces image smear. Enhancement of moving targets in imagery captured under extreme low light conditions imposes difficult challenges. SRI has demonstrated that image registration provides a robust solution for enhancing global scene contrast under very low SNR conditions.

Performance and design differences between PMOS and NMOS CMOS imagers

NMOS and PMOS CMOS imager design comparisons and performance differences are reviewed for night vision and scientific applications. Parameters include pixel read noise, charge transfer efficiency, charge collection efficiency, pixel readout speed, dark current and radiation damage tolerance. Focus of the paper is given to pixel read noise and dark current since these are the only parameters that require further development for our CMOS imagers. Discussions reveal that PMOS read noise is limited to ~ 1 h+ rms by flicker noise and why PMOS can fundamentally achieve lower noise than NMOS. We will examine where flicker noise is apparently generated and discuss various experiments that have been tried to lower it. New design and fabrication remedies are explored to reduce read noise below 1 h+ rms floor without reducing 1/f noise. Data is presented showing that PMOS and NMOS imagers are generating the same amount of dark current that is limited by silicon wafer contamination sources introduced in the fabrication process. Test data from a new stitched PMOS/NMOS Mk x Nk x 10 um pixel CMOS sensor suited for space borne NASA scientific applications is presented.

Asynchronous InGaAsP Geiger-Mode APD Cameras With Free-Running Pixel Operation

We describe 32x32 Geiger-mode avalanche photodiode focal plane arrays (FPAs) with single-photon sensitive pixels and asynchronous free-running operation. These FPAs support direct detection and coherent LIDAR imaging and other applications such as free-space optical communications. Article not available.