NEOWISE Observations of Distant Active Long-period Comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini)

Hyperactive comet activity typically becomes evident beyond the frost line (∼3-4 au) where it becomes too cold for water-ice to sublimate. If carbon monoxide (CO) and carbon dioxide (CO2) are the species that drive activity at sufficiently large distances, then detailed studies on the production rates of these species are extremely valuable to examine the formation of the solar system because these two species (beyond water) are next culpable for driving cometary activity. The NEOWISE reactivated mission operates at two imaging bandpasses, W1 and W2 at 3.4 μm and 4.6 μm, respectively, with the W2 channel being fully capable of detecting CO and CO2 at 4.67 μm and 4.23 μm in the same bandpass. It is extremely difficult to study CO2 from the ground due to contamination in Earth’s atmosphere. We present our W1 and W2 photometry, dust measurements, and findings for comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini), hereafter, B1, K2, and U3, respectively. Our results assess CO and CO2 gas production rates observed by NEOWISE. We have determined: (1) comets B1 and K2 have CO2 and CO gas production rates of ∼1027 and ∼1029 molecules s−1, respectively, if one assumes the excess emission is attributed to either all CO or all CO2; (2) B1 and K2 are considered hyperactive in that their measured Af ρ dust production values are on the order of ≳103 cm; and (3) the CO and CO2 production rates do not always follow the expected convention of increasing with decreased heliocentric distance, while B1 and K2 exhibit noticeable dust activity on their inbound leg orbits. © 2024. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The NEO Surveyor Near-Earth Asteroid Known Object Model

The known near-Earth object (NEO) population consists of over 32,000 objects, with a yearly discovery rate of over 3000 NEOs per year. An essential component of the next generation of NEO surveys is an understanding of the population of known objects, including an accounting of the discovery rate per year as a function of size. Using a near-Earth asteroid (NEA) reference model developed for NASA’s NEO Surveyor (NEOS) mission and a model of the major current and historical ground-based surveys, an estimate of the current NEA survey completeness as a function of size and absolute magnitude has been determined (termed the Known Object Model; KOM). This allows for understanding of the intersection of the known catalog of NEAs and the objects expected to be observed by NEOS. The current NEA population is found to be ∼38% complete for objects larger than 140 m, consistent with estimates by Harris & Chodas. NEOS is expected to catalog more than two-thirds of the NEAs larger than 140 m, resulting in ∼76% of NEAs cataloged at the end of its 5 yr nominal survey, making significant progress toward the US Congressional mandate. The KOM estimates that ∼77% of the currently cataloged objects will be detected by NEOS, with those not detected contributing ∼9% to the final completeness at the end of its 5 yr mission. This model allows for placing the NEOS mission in the context of current surveys to more completely assess the progress toward the goal of cataloging the population of hazardous asteroids. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Validation of the Survey Simulator Tool for the NEO Surveyor Mission Using NEOWISE Data

The Near-Earth Object Surveyor (NEO Surveyor) mission has a requirement to find two-thirds of the potentially hazardous asteroids larger than 140 m in size. In order to determine the mission’s expected progress toward this goal during design and testing, as well as the actual progress during the survey, a simulation tool has been developed to act as a consistent and quantifiable yardstick. We test that the survey simulation software is correctly predicting on-sky positions and thermal infrared fluxes by using it to reproduce the published measurements of asteroids from the NEOWISE mission. We then extended this work to find previously unreported detections of known near-Earth asteroids in the NEOWISE data archive, a search that resulted in 21,661 recovery detections, including 1166 objects that had no previously reported NEOWISE observations. These efforts demonstrate the reliability of the NEO Surveyor Survey Simulator tool and the perennial value of searchable image and source catalog archives for extending our knowledge of the small bodies of the solar system. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Asteroid diameters and albedos from neowise reactivation mission years six and seven

We present diameters and albedos computed for the near-Earth and main belt asteroids (MBAs) observed by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft during the sixth and seventh years of its Reactivation mission. These diameters and albedos are calculated from fitting thermal models to NEOWISE observations of 199 near-Earth objects (NEOs) and 5851 MBAs detected during the sixth year of the survey and 175 NEOs and 5861 MBAs from the seventh year. Comparisons of the NEO diameters derived from Reactivation data with those derived from the WISE cryogenic mission data show a ∼30% relative uncertainty. This larger uncertainty compared to data from the cryogenic mission is due to the need to assume a beaming parameter for the fits to the shorter-wavelength data that the Reactivation mission is limited to. We also present an analysis of the orbital parameters of the MBAs that have been discovered by NEOWISE during Reactivation, finding that these objects tend to be on orbits that result in their perihelia being far from the ecliptic, and thus missed by other surveys. To date, the NEOWISE Reactivation survey has provided thermal fits of 1415 unique NEOs. Including the mission phases before spacecraft hibernation increases the count of unique NEOs characterized to 1845 from WISE's launch to the present. © 2021. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Signal nonlinearity measurements and corrections in MWIR and LWIR HgCdTe H2RG arrays for NEO Surveyor

The depletion region around each p-n junction in HgCdTe HAWAII-2RG detector arrays decreases in volume as charge is collected, causing the pixel capacitance to change continuously throughout an integration period. This changing capacitance manifests as a steadily decreasing measured signal rate while observing a constant flux. Ignoring this nonlinear response to signal accumulation can lead to underestimating the number of detected pho- tons by as much as 10%. Presented here are two methods, one simple and one complex, of measuring this signal nonlinearity and a theoretical framework behind a nonlinearity correction method. Additionally, experimental data are compared with simulations to explain methods to reduce noise in the nonlinearity measurement and identify deviations from the expected behavior that merit further study. © SPIE. Downloading of the abstract is permitted for personal use only.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The Warm Spitzer NEO Survey: Exploring the history of the inner Solar System and near Earth space

The majority of Near Earth Objects (NEOs) originated in collisions between bodies in the main asteroid belt and have found their way into near Earth space via complex and little understood dynamical interactions. This transport of material from the main belt into the inner Solar System has shaped the histories of the terrestrial planets. However, despite their scientific importance, key characteristics of the NEO population --- such as the size distribution, mix of albedos and mineralogies, and contributions from so-called dead or dormant comets --- remain largely unexplored; some 99% of all presently known NEOs are essentially uncharacterized. We have an approved 500 hour Warm Spitzer program to derive albedos and diameters for some 700 NEOs. We will measure the size distribution of this population to understand fundamental physical processes that occur among the small bodies of our Solar System. We will measure the fraction of NEOs likely to be dead comets, with implications for the flux of organic material onto the Earth. We will measure the NEO albedo distribution, which indicates the compositional diversity among these small bodies. We will study properties of individual NEOs, including their surface properties and potentially their densities, and detailed properties of a subset of well-characterized objects. Our Warm Spitzer program began execution in July 2009, and will return on average one target per day for the next two years. We will present initial results from our program. This work is based on observations made with the Spitzer Space Telescope, which is operated by JPL/Caltech, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech

Blooming in H2RG arrays: Laboratory measurements of a second brighter-fatter type effect in HgCdTe infrared detectors

Improved measurement and calibration of detector behaviors will be crucial for future space missions, particularly those aiming to tackle outstanding questions in cosmology and exoplanet research. Similarly, many small detector effects, such as the nearest-neighbor interactions of the brighter-fatter effect and interpixel capacitance, will need to be considered to ensure measured signals are truly astronomical in origin. Laboratory measurements confirming the existence of an additional brighter-fatter type effect in HAWAII-1RG and HAWAII-2RG HgCdTe infrared arrays with cutoff wavelengths ranging from 5.7 to 16.7 μm are presented. This effect is similar in nature to the blooming observed in charge-coupled devices and is characterized by a pixel spontaneously sharing a current with its neighbors upon reaching saturation, serving to make the brightest sources appear fatter. In addition to exploring the cause and mechanism of current sharing for this effect, measurements for several arrays show the magnitude of the shared current is greater than 60% of the incoming photocurrent hitting the saturated pixel. A proof-of-concept correction method for this effect is also described along with the necessary next steps to improve this correction and investigate the amplitude of other nearest-neighbor interactions. © 2021 Society of Photo-Optical Instrumentation Engineers (SPIE).Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Size and Albedo Constraints for (152830) Dinkinesh Using WISE Data

Probing small main-belt asteroids provides insight into their formation and evolution through multiple dynamical and collisional processes. These asteroids also overlap in size with the potentially hazardous near-Earth object population and supply the majority of these objects. The Lucy mission will perform a flyby of the small main-belt asteroid, (152830) Dinkinesh, on 2023 November 1, in preparation for its mission to the Jupiter Trojan asteroids. In this Letter, we present data to support the planning of Lucy’s imminent encounter of Dinkinesh. We employed aperture photometry on stacked frames of Dinkinesh obtained by the Wide-field Infrared Survey Explorer and performed thermal modeling on a detection at 12 μm to compute diameter and albedo values. Through this method, we determined Dinkinesh has an effective spherical diameter of 0.76 − 0.21 + 0.11 km and a visual geometric albedo of 0.27 − 0.06 + 0.25 at the 16th and 84th percentiles. This albedo is consistent with typical stony (S-type) asteroids. These measurements will enable the Lucy team to optimize planning for the flyby of Dinkinesh, including refinement of exposure times and flyby geometry. The data obtained from this mission will, in turn, allow us to better understand the calibration of our thermal models by providing ground truth data. The Lucy flyby presents a rare opportunity to study the smallest main-belt asteroid ever observed in situ. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Modulation transfer function measurements of HgCdTe long wavelength infrared arrays for the Near-Earth Object Surveyor

The modulation transfer function (MTF) is a useful measure in image quality analysis and performance budget determination. Sensitive long wavelength infrared (LWIR) detectors for astronomical space telescopes require slight modifications to the existing MTF measurement methods due to the increased prevalence of high dark current pixels. Presented here are the specifics of a modified slanted edge method to determine the MTF in λc > 10 μm HgCdTe detectors to be used with the planned Near-Earth Object Surveyor Mission. The measured MTF at Nyquist using 6 μm light is 0.22 ± 0.02 and is 0.25 ± 0.02 using 10 μm light for both 250 and 350 mV of applied reverse bias. These measurements are from edge spread functions with median signal values around 50% of the well depth, as the MTF is expected to change with signal value due to two brighter-fatter type effects. The expected trends caused by the influences of these two effects and the expected trends with wavelength of absorbed photons are all observed. © 2022 Society of Photo-Optical Instrumentation Engineers (SPIE).Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Testing results from pathfinder HgCdTe infrared detectors for the Near-Earth Object Surveyor mission

Near-Earth Object (NEO) Surveyor, a NASA planetary defense space mission, is currently in Phase B with a launch date in 2026. NEO Surveyor is an infrared telescope designed to detect and characterize Potentially Hazardous Asteroids (PHAs). The required sensors leverage the space flight heritage and further development over the last 15 years of HgCdTe arrays to detect infrared light spanning from 4 to 10 µm. NEO Surveyor will employ eight passively cooled HgCdTe Sensor Chip Assemblies (SCAs) across two bands, each band consisting of a 1x4 SCA mosaic to cover a wide field of view. Four of these SCAs have a >5.5 µm cutoff wavelength and cover the shorter 4-5.2 µm (NC1) band, while four SCAs will have a >10.5 µm cutoff wavelength and span the longer 6-10 µm (NC2) band. We present calibration and performance results from two recently produced pathfinder SCAs, one for each band, manufactured by Teledyne Imaging Sensors with development guidance from the University of Arizona, the University of Rochester, and JPL. Both devices demonstrate the requisite low dark current, high well depth, and high quantum efficiency, exceeding mission requirements. © 2022 SPIE.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]