Different silicon avalanche photodiode structures are compared for the effects of 5 I -MeV protons on dark current and responsivity. Large differences in depletion widths coincided with differences in sensitivity to dark current increases and responsivity degradation. INTRODUCTION The ongoing interest in spacsbased light detection and ranging (LIDAR) experimentation continues to create a demand for highly sensitive and radiation tolerant photodetectors. Avalanche photodiodes (APDs) are often chosen for LIDAR systems due to their low noise and high gain compared to conventional detectors. For space applications requiring high sensitivity, radiation-induced changes in device parameters such as responsivity and dark current need to be quantified so that intensity dependent data are correctly interpreted. Limited radiation testing of APDs has been done previously [ 11, however radiation effects on differing avalanche photodiode structures have not been widely researched. This study examines two different silicon avalanche photodiode structures: a conventional APD from Advanced Photonix and an IR-enhanced APD from Perkin Elmer. Results for a third device type from Pacific Silicon will be included in the final paper. EXPERIMENTAL PROCEDURE characteristics: the RCA Type C30954E “reach through” structure by Perkin Elmer, and the 03670-62-53 1 by Advanced Photonix. Both are high speed APDs with active area diameters of 0.8 and 0.9 mm, respectively. However, there is an important dissimilarity. The reach through structure is enhanced for near infrared wavelengths, and has similar responsivity at 800nm and 1 micron. The Advanced Photonix APD has a more typical responsivity curve, for a silicon detector, which peaks at 800nm and falls off rapidly for longer wavelengths. The IR-enhanced APD has a much larger active collection depth because of the long absorption depth near the silicon bandgap edge. The APDs were irradiated at UC Davis using 5 1 -MeV protons. Samples of the Advanced Photonix device were irradiated with Cobalt-60 gamma rays in order to compare proton and gamma radiation effects. All devices were irradiated and evaluated under reverse bias. Pre-irradiation gain was approximately 100 for the Advanced Photonix device and 200 for the Perkin Elmer device. 800nm LED’s were the light source for responsivity measurements. 800nm is near the peak of the responsivity curves for these detectors and close to 8 15nm, a water absorption line that is important for certain LIDAR atmospheric studies. The IRenhanced structure was also evaluated at 1064nm, and that data will be presented in the final paper along with data on un-biased irradiations and annealing. Three samples of each device were tested at 800nm. Irradiations were conducted at room temperature, and preand postirradiation characterization was done at 22C. Two silicon APD structures were studied to determine how proton and gamma radiation affect their *The research in this paper was carried out at the Jet Propulsion Laboratory, Califomia Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA), under the NASA Electronic Parts and Packaging Program, Code AE.
<p>Juno enters its Extended Mission with its low-light sensitive Stellar Reference Unit (SRU) navigation camera poised to explore the Jovian system under novel illumination conditions. During the Prime Mission, high resolution SRU images of Jupiter&#8217;s dark side led to the discovery of &#8220;shallow lightning,&#8221; discharges originating from high altitude ammonia-water storms (above the 2 bar level) where it is too cold for liquid water to exist. Unique SRU images of Jupiter&#8217;s faint dust ring have been captured from rare vantage points, including from locations inside the ring looking out. And during Juno&#8217;s 34th orbit, the SRU acquired a high resolution (< 1 km/pixel), high illumination angle (>79 degrees) image of Ganymede&#8217;s dark side in a region of Xibalba Sulcus illuminated solely by Jupiter-shine. This softly lit image reveals numerous small craters and surface features which are unresolved in the prior Voyager imagery used in the USGS map. This presentation will highlight the recent science findings of Juno&#8217;s SRU.</p><p>&#160;</p><p>The JPL authors&#8217; copyright for this abstract is held by the California Institute of Technology. Government Sponsorship acknowledged.</p>
<p>The Juno Mission has recast its spacecraft engineering star camera as a visible wavelength science imager. Developed and primarily used to support onboard attitude determination, Juno&#8217;s Stellar Reference Unit (SRU) has been put to use as an in situ high energy particle detector for profiling Jupiter&#8217;s radiation belts and as a low light sensitive camera for exploring multiple phenomena and features of the Jovian system. Juno&#8217;s unprecedented polar orbit and closest approach of ~4000 km have yielded high resolution SRU imagery of Jupiter&#8217;s lightning and aurorae from as little as 50,000 km from the 1 bar level and unique Jovian dust ring and satellite images. We will present recent SRU results and discuss the implications for Jupiter&#8217;s atmosphere that stem from the SRU lightning observations.</p>
Abstract Jupiter's polar aurora exhibits low brightness temperatures in Juno Microwave Radiometer (MWR) observations when the Juno spacecraft passes over the high‐latitude region of the Northern Hemisphere. These cold features are observed predominantly at 0.6 GHz and show both long‐term hours and short‐term changes over time, that is, spans less than the 30‐s spacecraft spin period. The MWR “cold spot” observations are associated with polar ultraviolet emission features that are thought to originate from high energy electron precipitation into the Jovian high latitude atmosphere. The energetic electron precipitation produces strong absorptive characteristics at microwave frequencies due to the transient formation of high‐density electron regions in the lower stratosphere. In this paper, we describe progress on the analysis of Juno MWR observations of the northern aurora and simulate the effects of heating and electron impact ionization processes due to high energy particle precipitation events in Jupiter's auroral ionosphere. Electron precipitation intensities at energies up to 10 MeV inferred from the Jupiter Energetic‐Particle Detector Instrument (JEDI) and Ultraviolet Spectrograph (UVS) instruments are used as a Northern Hemisphere case study to understand the energy deposition and ionization processes in the lower stratosphere, and subsequently used to estimate the microwave and ultraviolet opacity of the auroral region. The northward progression of Juno's perijove during the mission reduces the overflight altitude and allows important insights into effects produced at different length scales with respect to the auroral oval.
On 29 September 2022 Juno’s low-light Stellar Reference Unit (SRU) captured a high-resolution image (256-340 m/pixel) of a 3x104 km2 region of Europa’s surface between ~0-6°N and 43.5-51°W. The broadband visible image (450-1100 nm), with the highest resolution ever for that region, was collected at a sub-spacecraft altitude of 412 km during Juno’s close flyby of the icy Jovian moon while the surface was illuminated only by Jupiter-shine (incidence angle: 48-51 degrees). Prior coverage of the area by Galileo was under high-sun conditions at 1 km resolution, leading to characterization of the region as mostly ridged plain and undifferentiated linea. The SRU image reveals a much richer and complex picture; an intricate network of cross-cutting ridges and lineated bands interrupted by an intriguing 37 km (east-west) by 67 km (north-south) chaos feature that appears to be the result of a unique, local geologic process. Low-albedo deposits flank ridges near the chaos feature and bear similarity to features previously linked to hypothesized subsurface activity [Quick & Hedman, Icarus, 2020]. We will present updates to the geologic mapping of Europa enabled by the SRU image, our study of the chaos feature’s morphology, and puzzles awaiting future high-resolution imagery from Europa Clipper or JUICE.  The JPL authors’ copyright for this abstract is held by the California Institute of Technology. Government Sponsorship acknowledged.
Degradation of InGaAs/InP and InGaAsP/InP Geiger-mode avalanche photodiodes caused by proton irradiation is studied for the first time. Substantial changes in the dark I-V characteristics as well as increases in the dark count rate are observed after irradiation. There are no systematic changes in photon count rate observed or in the amount of after-pulsing. The devices are rendered non-operational following a fluence of 8.1×10 10 50-Mev protons/cm 2 for room temperature operation.
Abstract Juno's “Perijove 1” (27 August 2016) and “Perijove 3” (11 December 2016) flybys through the innermost region of Jupiter's magnetosphere (radial distances <2 Jovian radii, 1.06 R J at closest approach) provided the first in situ look at this region's radiation environment. Juno's Radiation Monitoring Investigation collected particle counts and noise signatures from penetrating high‐energy particle impacts in images acquired by the Stellar Reference Unit and Advanced Stellar Compass star trackers, and the Jupiter Infrared Auroral Mapper infrared imager. This coordinated observation campaign sampled radiation at the inner edges of the high‐latitude lobes of the synchrotron emission region and more distant environments. Inferred omnidirectional >5 MeV and >10 MeV electron fluxes derived from these measurements provide valuable constraints for models of relativistic electron environments in the inner radiation belts. Several intense bursts of high‐energy particle counts were also observed by the Advanced Stellar Compass in polar regions outside the radiation belts.
Abstract Degradation of InGaAs/InP Geiger-mode avalanche photodiodes caused by proton irradiation is reported for the first time. The devices are found to be very sensitive to displacement damage. Substantial changes in the dark count rate, and the after-pulse count rate are observed following room temperature irradiation and characterization at −50°C. The device detection efficiency is unaffected by irradiation. Following 51 MeV proton fluences in the mid 109 protons/cm2 range, the dark count rate becomes so large that the devices are rendered essentially unusable. This is a very low fluence at which to observe device failure. Keywords: APDavalanche photodiodeGeiger-modeproton irradiationradiation effectssingle photon detector Acknowledgements This research work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). Helpful discussions with Larry Edmonds and Steve Guertin at JPL on the histogram analysis are gratefully acknowledged.
