Extending the capabilities of optical remote sensing and inverse optical algorithms, which have been commonly focused on the visible (VIS) range of the electromagnetic spectrum, to derive the optical ...properties of seawater in the ultraviolet (UV) range is important to advancing the understanding of various optical, biological, and photochemical processes in the ocean. In particular, existing remote-sensing reflectance models that derive the total spectral absorption coefficient of seawater, a(λ), and absorption partitioning models that partition a(λ) into the component absorption coefficients of phytoplankton, a
(λ), non-algal (depigmented) particles, a
(λ), and chromophoric dissolved organic matter (CDOM), a
(λ), are restricted to the VIS range. We assembled a quality-controlled development dataset of hyperspectral measurements of a
(λ) (N = 1294) and a
(λ) (N = 409) spanning a wide range of values across various ocean basins, and evaluated several extrapolation methods to extend a
(λ), a
(λ), and a
(λ) ≡ a
(λ) + a
(λ) into the near-UV spectral region by examining different sections of the VIS as a basis for extrapolation, different extrapolation functions, and different spectral sampling intervals of input data in the VIS. Our analysis determined the optimal method to estimate a
(λ) and a
(λ) at near-UV wavelengths (350 to 400 nm) which relies on an exponential extrapolation of data from the 400-450 nm range. The initial a
(λ) is obtained as a difference between the extrapolated estimates of a
(λ) and a
(λ). Additional correction functions based on the analysis of differences between the extrapolated and measured values in the near-UV were defined to obtain improved final estimates of a
(λ) and a
(λ) and then the final estimates of a
(λ) as a sum of final a
(λ) and a
(λ). The extrapolation model provides very good agreement between the extrapolated and measured data in the near-UV when the input data in the blue spectral region are available at 1 or 5 nm spectral sampling intervals. There is negligible bias between the modeled and measured values of all three absorption coefficients and the median absolute percent difference (MdAPD) is small, e.g., < 5.2% for a
(λ) and < 10.5% for a
(λ) at all near-UV wavelengths when evaluated with the development dataset. Assessment of the model on an independent dataset of concurrent a
(λ) and a
(λ) measurements (N = 149) yielded similar findings with only slight reduction of performance and MdAPD remaining below 6.7% for a
(λ) and 11% for a
(λ). These results are promising for integration of the extrapolation method with absorption partitioning models operating in the VIS.
In response to the growing interest in offshore wind energy development in California, the U.S. Bureau of Ocean Energy Management delineated three Call Areas for potential leasing. This study ...provides a comprehensive characterization and comparison of offshore wind power potential within the two Central California Call Areas (Diablo Canyon and Morro Bay) using 12‐ and 15‐MW turbines under different inter‐turbine spacing and wind farm size scenarios. Our analysis shows similar daily and seasonal patterns of wind power produced within the Call Areas, which peak in spring and during evening hours. Per‐turbine power production is higher in the Morro Bay Call Area due to slightly higher hub‐height wind speeds, whereas total power production is higher in the Diablo Canyon Call Area due to its larger size. Turbine type had a negligible impact on average power production per‐unit‐area because while larger turbines produce more power, they require greater inter‐turbine spacing. Combined power production from the two fully built out Call Areas could equal nearly a quarter of California's current annual electrical energy production. A commercial‐scale wind farm with a realized power output of 960 MW would require a footprint of at least half of the Morro Bay Call Area or at least a quarter of the Diablo Canyon Call Area. These results provide guidance on offshore wind development over the Central California Coast, and the framework demonstrated here could be applied to other wind data sets in other regions.
The analysis of the spatiotemporal variability of wind power remains limited during the planning stage of an offshore wind farm. This study provides a framework to investigate how offshore wind power ...varies along the Central California Coast over diurnal and seasonal time scales, which is critical for reliability and functionality of the grid system. We find that offshore wind power in this region peaks during evening hours across all seasons and maximizes in spring and summer. The timing of peak offshore wind power production better aligns with that of peak demand across California than solar and land-based wind power production, highlighting its potential to fill the supply gap when demand is high and power production from other renewable energy sources is low. We further assess the value of offshore wind power using demand-based and wholesale market metrics. Both metrics indicate high potential value of offshore wind power over most areas in this region. Finally, we show that the estimate of power production is significantly biased when using mean wind speeds that do not account for temporal variability, leading to potentially inaccurate predictions about locations that are expected to produce the most power. These results reiterate the importance in considering spatiotemporal variability in wind power for accurately calculating the value of offshore wind development.
In 2019, the Research and Education Collaborative Occultation Network (RECON) obtained multiple-chord occultation measurements of two Centaur objects: 2014 YY49 on 2019 January 28 and 2013 NL24 on ...2019 September 4. RECON is a citizen-science telescope network designed to observe high-uncertainty occultations by outer solar system objects. Adopting circular models for the object profiles, we derive a radius km and a geometric albedo for 2014 YY49 and a radius km and a geometric albedo for 2013 NL24. To the precision of these measurements, no atmosphere or rings are detected for either object. The two objects measured here are among the smallest distant objects measured with the stellar occultation technique. In addition to these geometric constraints, the occultation measurements provide astrometric constraints for these two Centaurs at a higher precision than has been feasible by direct imaging. To supplement the occultation results, we also present an analysis of color photometry from the Pan-STARRS surveys to constrain the rotational light curve amplitudes and spectral colors of these two Centaurs. We recommend that future work focus on photometry to more deliberately constrain the objects' colors and light curve amplitudes and on follow-on occultation efforts informed by this astrometry.
Abstract
A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132) Leleākūhonua (also known by the provisional designation of 2015 TG
387
) was predicted by the Lucky Star ...project and observed with the Research and Education Collaborative Occultation Network on 2018 October 20 UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is
km, corresponding to a geometric albedo
, for an adopted absolute magnitude of
H
V
= 5.6, typical of other objects in dynamically similar orbits. The occultation also provides a high-precision astrometric constraint.
A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132) Lele k honua (also known by the provisional designation of 2015 TG387) was predicted by the Lucky Star project ...and observed with the Research and Education Collaborative Occultation Network on 2018 October 20 UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is km, corresponding to a geometric albedo , for an adopted absolute magnitude of HV = 5.6, typical of other objects in dynamically similar orbits. The occultation also provides a high-precision astrometric constraint.
We report on the stellar occultation by (523764) 2014 WC510 observed on 2018 December 1 UT. This occultation campaign was part of the Research and Education Collaborative Occultation Network (RECON), ...a network of small telescopes spread over 2000 km in western USA and Canada. Light curves from six stations revealed three groups of two or more consecutive flux drops correlated in time between adjacent stations. A Bayesian model comparison reveals that a model with a double object occulting a double star is favored over alternative models considered. For the statistically favored model, we determined that the primary component of the object has a diameter dp = 181 16 km and the secondary ds = 138 32 km, assuming identical geometric albedo between the two components. The two components have a projected separation of 349 26 km. Adopting an absolute magnitude for the system of HV = 7.2 from the Minor Planet Center, we derive a geometric albedo of pV = 5.1% 1.7%. This is the smallest resonant object with an occultation size measurement and with a detected secondary from a ground-based stellar occultation, filling a region of the size versus separation parameter space of binary objects that is largely unexplored. The results show the capabilities of the unique design of the RECON experiment sensitive to small objects and close binaries. 2014 WC510 is presently at a low galactic latitude where the high surface density of stars will provide good occultation opportunities in the upcoming years.
Abstract
In 2019, the Research and Education Collaborative Occultation Network (RECON) obtained multiple-chord occultation measurements of two Centaur objects: 2014 YY
49
on 2019 January 28 and 2013 ...NL
24
on 2019 September 4. RECON is a citizen-science telescope network designed to observe high-uncertainty occultations by outer solar system objects. Adopting circular models for the object profiles, we derive a radius
km and a geometric albedo
for 2014 YY
49
and a radius
km and a geometric albedo
for 2013 NL
24
. To the precision of these measurements, no atmosphere or rings are detected for either object. The two objects measured here are among the smallest distant objects measured with the stellar occultation technique. In addition to these geometric constraints, the occultation measurements provide astrometric constraints for these two Centaurs at a higher precision than has been feasible by direct imaging. To supplement the occultation results, we also present an analysis of color photometry from the Pan-STARRS surveys to constrain the rotational light curve amplitudes and spectral colors of these two Centaurs. We recommend that future work focus on photometry to more deliberately constrain the objects’ colors and light curve amplitudes and on follow-on occultation efforts informed by this astrometry.
A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132) Lele\={a}k\={u}honua (also known by the provisional designation of 2015 TG387) was predicted by the Lucky Star ...project and observed with the Research and Education Collaborative Occultation Network on 2018 October 20 UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is \(r={110}_{-10}^{+14}\) km, corresponding to a geometric albedo \({p}_{V}={0.21}_{-0.05}^{+0.03}\), for an adopted absolute magnitude of H V = 5.6, typical of other objects in dynamically similar orbits. The occultation also provides a high-precision astrometric constraint.
In 2019, the Research and Education Collaborative Occultation Network (RECON) obtained multiple-chord occultation measurements of two centaur objects: 2014 YY\(_{49}\) on 2019 January 28 and 2013 ...NL\(_{24}\) on 2019 September 4. RECON is a citizen-science telescope network designed to observe high-uncertainty occultations by outer solar system objects. Adopting circular models for the object profiles, we derive a radius \(r=16^{+2}_{-1}\)km and a geometric albedo \(p_V=0.13^{+0.015}_{-0.024}\) for 2014 YY\(_{49}\), and a radius \(r=66 ^{+5}_{-5}\)km and geometric albedo \(p_V = 0.045^{+0.006}_{-0.008}\) for 2013 NL\(_{24}\). To the precision of these measurements, no atmosphere or rings are detected for either object. The two objects measured here are among the smallest distant objects measured with the stellar occultation technique. In addition to these geometric constraints, the occultation measurements provide astrometric constraints for these two centaurs at a higher precision than has been feasible by direct imaging. To supplement the occultation results, we also present an analysis of color photometry from the Pan-STARRS surveys to constrain the rotational light curve amplitudes and spectral colors of these two centaurs. We recommend that future work focus on photometry to more deliberately constrain the objects' colors and light curve amplitudes, and on follow-on occultation efforts informed by this astrometry.
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