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We estimated geometric plume heights for the daytime eruptions of La Soufrière in April 2021 using visible red band geostationary side views and geostationary–polar orbiter stereo views. Most of the plumes either spread near the tropopause at 16–17 km altitude or penetrated the stratosphere at 18–20 km altitude. Overshooting tops reached heights of up to 23 km. These geometric heights were compared with radiometric heights corresponding to the coldest plume temperature, which usually represent ambiguous estimates within a wide range between a tropospheric and a stratospheric height match. The tropospheric lower bound of the radiometric height range always underestimated the geometric height by a couple of kilometers, even for smaller plumes. For plumes near or above the tropopause, the midpoint or the stratospheric upper bound of the radiometric height range was in reasonable agreement with the geometric heights. The geometric overshooting top height, however, was always above the radiometric height range. We also found that geometric plume heights can be estimated from infrared band side views too, albeit with increased uncertainty compared to the visible red band. This opens up the possibility of applying the side view method to nighttime eruptions.

A geometric technique is introduced to estimate the height of volcanic eruption columns using the generally discarded near-limb portion of geostationary imagery. Such oblique observations facilitate a height-by-angle estimation method by offering close to orthogonal side views of eruption columns protruding from the Earth ellipsoid. Coverage is restricted to daytime point estimates in the immediate vicinity of the vent, which nevertheless can provide complementary constraints on source conditions for the modelling of near-field plume evolution. The technique is best suited to strong eruption columns with minimal tilting in the radial direction. For weak eruptions with severely bent plumes or eruptions with expanded umbrella clouds the radial tilt/expansion has to be corrected for either visually or using ancillary wind profiles. Validation on a large set of mountain peaks indicates a typical height uncertainty of ±500 m for near-vertical eruption columns, which compares favourably with the accuracy of the common temperature method.

Wildfires have posed increasing risks to human health and loss of life and property. Observations of wildfire remain limited, particularly the plume variables such as injection height and wind velocity critical to assessing wildfire impacts. Lack of adequate spatiotemporal coverage and measurement accuracy hinder predictability and initialization needed by weather and chemical transport models. The new observations from the emerging stereo wind and aerosol imaging techniques with LEO-GEO and GEO-GEO satellites offer an unprecedented opportunity to study wildfire dynamics and evolution processes in great detail. The diurnal coverage of the GEO-GEO winds stereo products (Carr et al., 2020, 2019, 2018) and the daytime coverage (and detail) of GEO multi-angle aerosol products (Limbacher et al., 2021; In Prep) can capture and further our understanding of intense wildfire dynamics (e.g., pyroCb), planetary boundary layer (PBL) variations, and direction of aerosol loadings. Using two new satellite-based stereoscopic tracking algorithms, we compare stereo observations directly with the Coupled WRF-CMAQ simulations (Zou et al., 2019) to diagnose the modeled plume injection height and wind velocity, and aerosol properties (Friberg et al., 2021; In Prep). The validated LEO-GEO winds and height algorithm provides plume dynamics data with an accuracy of 200 m vertical resolution for plume height and 0.5 m/s for plume speed. Using these stereo algorithms, we can determine if fire plumes stay within or shoot above PBL, which plays a critical role in plume transport and air quality. From the GEO-based observations of dynamic wildfire aerosol loading dispersion, height, and winds, we can track wildfire development at a sub-hourly frequency and capture extreme and/or rare events such as pyroCb that often occur in a short period of time and are largely missed by LEO satellites. References:Carr, J.L., Wu, D.L., Daniels, J., Friberg, M.D., Bresky, W., Madani, H. “GEO-GEO Stereo-Tracking of Atmospheric Motion Vectors (AMVs) from the Geostationary Ring,” Remote Sensing, 2020 https://doi.org/10.3390/rs12223779Carr, J.L., D.L. Wu, R.E. Wolfe, H. Madani, G. Lin, B. Tan, “Joint 3D-Wind Retrievals with Stereoscopic Views from MODIS and GOES,” Remote Sensing, 2019, Satellite Winds Special Issue https://doi.org/10.3390/rs11182100Carr, J.L., D.L. Wu, M.A. Kelly, and J. Gong, “MISR-GOES 3D Winds: Implications for Future LEO-GEO and LEO-LEO Winds,” Remote Sensing, 2018, MISR Special Issue. https://www.mdpi.com/2072-4292/10/12/1885Limbacher, J. A., R. A. Kahn, and M. D. Friberg “A Multi-Angle Geostationary Aerosol Retrieval Algorithm,” 2021 [In Prep].Zou, Y., O’Neill, S.M., Larkin, N.K., Alvarado, E.C., Solomon, R., Mass, C., Liu, Y., Odman, M.T., Shen, H. “Machine learning based integration of high-resolution wildfire smoke simulations and observations for regional health impact assessment. International Journal of Environmental Research and Public Health, 2019. https://doi.org/10.3390/ijerph16122137Friberg, M.D., Wu, D.L., Carr, J.L., Limbacher, J. A., Zou, Y., O’Neill, S. “Diurnal Observations of Wildfires Boundary Layer Dynamics and Aerosol Plume Convection using Stereo-Imaging Techniques,” 2021 [In Prep].

In a companion paper (Horváth et al., 2021), we introduced a new technique to estimate volcanic eruption column height from extremely oblique near-limb geostationary views. The current paper demonstrates and validates the technique in a number of recent eruptions, ranging from ones with weak columnar plumes to subplinian events with massive umbrella clouds and overshooting tops that penetrate the stratosphere. Due to its purely geometric nature, the new method is shown to be unaffected by the limitations of the traditional brightness temperature method, such as height underestimation in subpixel and semitransparent plumes, ambiguous solutions near the tropopause temperature inversion, or the lack of solutions in undercooled plumes. The side view height estimates were in good agreement with plume heights derived from ground-based video and satellite stereo observations, suggesting they can be a useful complementary to established techniques.

Height assignment is an important problem for satellite measurements of Atmospheric Motion Vectors (AMVs) that are interpreted as winds by forecast and assimilation systems. Stereo methods assign heights to AMVs from the parallax observed between observations from different vantage points in orbit while tracking cloud or moisture features. In this paper, we fully develop the stereo method to jointly retrieve wind vectors with their geometric heights from geostationary satellite pairs. Synchronization of observations between observing systems is not required. NASA and NOAA stereo-winds codes have implemented this method and we have processed large datasets from GOES-16, -17, and Himawari-8. Our retrievals are validated against rawinsonde observations and demonstrate the potential to improve forecast skill. Stereo winds also offer an important mitigation for the loop heat pipe anomaly on GOES-17 during times when warm focal plane temperatures cause infra-red channels that are needed for operational height assignments to fail. We also examine several application areas, including deep convection in tropical cyclones, planetary boundary layer dynamics, and fire smoke plumes, where stereo methods provide insights into atmospheric processes. The stereo method is broadly applicable across the geostationary ring where systems offering similar Image Navigation and Registration (INR) performance as GOES-R are deployed.

StereoBit is an embedded application for the SpaceCube family of hybrid onboard processors developed by NASA's Goddard Space Flight Center under sponsorship of the Earth Science Technology Office. StereoBit applies structure from motion algorithms to measure disparities between clouds being tracked from multiple angles to enable 3D resolution of atmospheric motion, which is an important Decadal Survey objective. Our Advanced Information Systems Technology project has the objectives of developing and demonstrating StereoBit for a future mission architecture employing a constellation of CubeSats and to mature the capabilities of the community to program the SpaceCube- family of processors for science applications.

Science Question: How can we use two new geostationary satellite-based algorithms to constrain wildfire plume modeling simulations?Method: Our approach is twofold. Combining NASA’s legacy MODIS products with the GOES Advanced Baseline Imager imagery, the state-of-the-art 3D-Wind algorithm, we first compare satellite-based detected wildfire plume injection heights with CMAQ, a chemical transport model. The validated GOES-MODIS 3D-Wind algorithm provides plume dynamics data with < 200 m vertical resolution for plume height and < 0.5 m/s for plume speed. Secondly, we compare aerosol type observations from the novel Multi-Angle Geostationary Aerosol Research Algorithm (MAGARA) to constrain modeled smoke hotspots and dispersion patterns of aerosols. Consistently modeled meteorology and extensive satellite coverage combine to produce more accurate plume injection heights and dispersion patterns, especially in areas where ground measurements are limited or absent. We compare the results of the two novel algorithms, 3D-Wind and MAGARA, to the 2018 Camp Fire event CMAQ runs. Impact: Geostationary satellite wildfire plume-attribute products provide spatiotemporal context and can decrease errors in plume characterization. Why It Matters: According to the EPA, wildland fires contributed approximately 30 percent of directly emitted fine particulate matter, linked to premature death from heart and lung disease. By capturing the dynamic wildfire plume dispersion, height, and winds, we can determine if fire plumes stay within or shoot above the planetary boundary layer and constrain modeling results. Improved accuracy, coverage, and characterization of plume injection height data increase the effectiveness of management methods that reduce and estimate smoke exposure.

Vortex streets formed in the stratocumulus‐capped wake of mountainous islands are the atmospheric analogues of the classic Kármán vortex street observed in laboratory flows past bluff bodies. The quantitative analysis of these mesoscale unsteady atmospheric flows has been hampered by the lack of satellite wind retrievals of sufficiently high spatial and temporal resolution. Taking advantage of the cutting‐edge Advanced Baseline Imager, we derived kilometer‐scale cloud‐motion winds at 5‐min frequency for a vortex street in the lee of Guadalupe Island imaged by Geostationary Operational Environmental Satellite‐16. Combined with Moderate Resolution Imaging Spectroradiometer data, the geostationary imagery also provided accurate stereo cloud‐top heights. The time series of geostationary winds, supplemented with snapshots of ocean surface winds from the Advanced Scatterometer, allowed us to capture the wake oscillations and measure vortex shedding dynamics. The retrievals revealed a markedly asymmetric vortex decay, with cyclonic eddies having larger peak vorticities than anticyclonic eddies at the same downstream location. Drawing on the vast knowledge accumulated about laboratory bluff body flows, we argue that the asymmetric island wake arises from the combined effects of Earth's rotation and Guadalupe's nonaxisymmetric shape resembling an inclined flat plate at low angle of attack. However, numerical simulations will need to establish whether or not the selective destabilization of the shallow atmospheric anticyclonic eddies is caused by the same mechanisms that destabilize the deep columnar anticyclones of laboratory flows, such as three‐dimensional vertical perturbations due to centrifugal or elliptical instabilities., Journal of Geophysical Research: Atmospheres, 125 (4)

Image navigation and registration (INR) processing for the Geostationary Lightning Mapper (GLM) assigns geographic coordinates to lightning events using orbit and attitude telemetry and a geometric calibration that matches coastline features from the GLM background scene against a digital map. Required performance is expressed as an optical angle at the aperture of the instrument of 112 μrad (3σ), equivalent to 4 km at the subsatellite point. This is only one-half the linear dimension of the ground footprint of a detector element at the center of the field of view and is challenging to both attain and validate. Our validation approach uses imagery from the Advanced Baseline Imager (ABI) Band 3 (B03), the ABI channel closest to the GLM spectrally, with 1-km pixel resolution at the subsatellite point, as an INR reference. The finer spatial resolution and the high-accuracy INR (

Global wind observations are fundamental for studying weather and climate dynamics and for operational forecasting. Most wind measurements come from atmospheric motion vectors (AMVs) by tracking the displacement of cloud or water vapor features. These AMVs generally rely on thermal infrared (IR) techniques for their height assignments, which are subject to large uncertainties in the presence of weak or reversed vertical temperature gradients near the planetary boundary layer (PBL) and tropopause folds. Stereo imaging can overcome the height assignment problem using geometric parallax for feature height determination. In this study we develop a stereo 3D-Wind algorithm to simultaneously retrieve AMV and height from geostationary (GEO) and low Earth orbit (LEO) satellite imagery and apply it to collocated Geostationary Operational Environmental Satellite (GOES) and Multi-angle Imaging SpectroRadiometer (MISR) imagery. The new algorithm improves AMV and height relative to products from GOES or MISR alone, with an estimated accuracy of

The Johns Hopkins University Applied Physics Laboratory (JHU/APL) is developing a compact, light-weight, and low power midwave-infrared (MWIR) imager called the Compact Midwave Imaging Sensor (CMIS), under the support of the NASA Earth Science Technology Office Instrument Incubator Program. The goal of this CMIS instrument development and demonstration project is to increase the technical readiness of CMIS, a multi-spectral sensor capable of retrieving 3D winds and cloud heights 24/7, for a space mission. The CMIS instrument employs an advanced MWIR detector that requires less cooling than traditional technologies and thus permits a compact, low-power design, which enables accommodation on small spacecraft such as CubeSats. CMIS provides the critical midwave component of a multi-spectral sensor suite that includes a high-resolution Day-Night Band and a longwave infrared (LWIR) imager to provide global cloud characterization and theater weather imagery. In this presentation, an overview of the CMIS project, including the high-level sensor design, the concept of operations, and measurement capability will be presented. System performance for a variety of different scenes generated by a cloud resolving model (CRM) will also be discussed.

A set of protocols for catalytic enantioselective allylic substitution (EAS) reactions that allow for additions of alkenyl units to readily accessible allylic electrophiles is disclosed. Transformations afford 1,4-dienes that contain a tertiary carbon stereogenic site and are promoted by 1.0–5.0 mol % of a copper complex of an N-heterocyclic carbene (NHC). Aryl- as well as alkyl-substituted electrophiles bearing a di- or trisubstituted alkene may be employed. Reactions can involve a variety of robust alkenyl–(pinacolatoboron) [alkenyl–B(pin)] compounds that can be either purchased or prepared by various efficient, site-, and/or stereoselective catalytic reactions, such as cross-metathesis or proto-boryl additions to terminal alkynes. Vinyl-, E-, or Z-disubstituted alkenyl-, 1,1-disubstituted alkenyl-, acyclic, or heterocyclic trisubstituted alkenyl groups may be added in up to >98% yield, >98:2 SN2′:SN2, and 99:1 enantiomeric ratio (er). NHC–Cu-catalyzed EAS with alkenyl–B(pin) reagents containing a conjugated carboxylic ester or aldehyde group proceed to provide the desired 1,4-diene products in good yield and with high enantioselectivity despite the presence of a sensitive stereogenic tertiary carbon center that could be considered prone to epimerization. In most instances, the alternative approach of utilizing an alkenylmetal reagent (e.g., an Al-based species) represents an incompatible option. The utility of the approach is illustrated through applications to enantioselective synthesis of natural products such as santolina alcohol, semburin, nyasol, heliespirone A, and heliannuol E.

Intracellular photolysis of a novel 'caged' capsaicin analogue results in in vitro activation of the capsaicin receptor TRPV1.

Many small unmanned aerial systems use true-color digital cameras for remote sensing. For some cameras, only the red channel is sensitive to near-infrared (NIR) light. Given a camera with this spec...

Image Navigation and Registration (INR) is the engineering discipline that deals with the problem of calibrating and stabilizing image geometry, particularly in the domain of geostationary weather satellites where the term appears to have first come into use within the GOES program. GOES I-M represented the transition from spin-stabilization to three-axis control within the GOES program. A spin-stabilized spacecraft, with its large gyroscopic stiffness, is a stable platform for supporting challenging Earth-observation missions from geostationary orbit. Unfortunately, a telescope deployed on a spin-stabilized spacecraft looks towards the Earth only about 5% of the time. NASA and NOAA were justifiably concerned in the GOES I-M epoch by the idea of adapting what was essentially communications satellite attitude control technology to host precision-pointed scanning instruments and accorded special attention to these concerns within the GOES I-M specifications under the heading of INR. The technology and performance of INR systems have evolved considerably since then and the field has found application in a host of non-U.S. systems, including Meteosat, MTSAT, and COMS. This paper looks back at the field beginning with GOES I-M and traces its evolution through Meteosat Second Generation (MSG), MTSAT, COMS, and GOES N-P with advanced stellar-inertial attitude control. It concludes with an analysis of where the field is likely to be heading for the next generation systems, in particular, GOES-R and Meteosat Third Generation (MTG).

The Advanced Baseline Imager (ABI) is the primary Earth observing sensor on the new generation Geostationary Operational Environmental Satellites (GOES-R) series, and provides significant spectral, spatial and temporal observational enhancements compared to the legacy GOES satellites. ABI also provides enhanced capabilities for operational sensor calibration and image navigation and registration (INR) to enable observations of the Earth with high spectral fidelity as well as creating images that are accurately mapped and co-registered over time. Unlike earlier GOES Imagers, ABI has onboard calibration capability for all sixteen bands in the reflective and emissive bands. The calibration process includes periodic and routine views of the internal reflective and blackbody targets as well as views of space and the moon. Improvements in INR are made possible by having a Global Positioning System (GPS) on board the spacecraft and routine measurements of stars through the sensor’s boresight for orbit and attitude determination through a Kalman filter. This paper describes how the sensor data are processed into calibrated and geolocated radiances that enable the generation of imagery and higher level products for both meteorological and non-meteorological Earth science applications. Some examples of ABI images and calibration are presented to demonstrate the capabilities and applications of the sensor.

A broadly applicable method for catalytic enantioselective allylic substitution of easily accessible di- or trisubstituted allylic phosphates and alkenyl-boron reagents, resulting in formation of tertiary C—C bonds, is presented.

The total syntheses of (±)-aspercyclide A (1) and its C19 methyl ether derivative (15a) are described. ELISA studies show that both compounds display comparable antagonist activity against the IgE–FcεRI protein–protein interaction.

Catalytic enantioselective allylic substitution (EAS) reactions are of prominent utility in chemical synthesis.[i] Such transformations generate a stereogenic center adjacent to an alkene, which can be further functionalized to afford a range of other enantiomerically enriched molecules. Despite noteworthy advances, several issues remain unresolved in this area. Nearly all the existing protocols require nucleophilic metal-based reagents, which, while often the source of high reactivity, are not well suited when certain commonly occurring functional groups are present. Moreover, whereas significant focus has been placed on additions of alkyl groups,[i] reported examples of catalytic processes that lead to incorporation of aryl or heteroaryl,[ii] allyl,[iii] alkynyl[iv] or allenyl[v] moieties are markedly small in number.

The total syntheses of (±)-aspercyclide A (1) and its C19 methyl ether (15a) featuring Heck–Mizoroki macrocyclisation to form the 11-membered (E)-styrenyl biaryl ether lactone core are described.

Traditionally, optical remote sensing payload design satisfies highly defined specifications arrived at by consensus of the scientific constituency. Designs are constrained by required performance such as resolution, Modulation Transfer Function (MTF), and Signal-to-Noise-Ratio (SNR). Payload designers satisfy the specification by performing hardware and cost trades. This process may lack continuous feedback between the performance of the scientific algorithms and the payload design, potentially missing optimal design points. The traditional method has produced separate and specific designs for imagery (over-sampling ratio Q > 0.8) vs. radiometry (Q < 0.8). Radiometers are scientifically precise, with highly accurate scene collection over a tightly defined pixel size exclusive of other scene points, often across several spectral channels. Imagers reveal sharper features, but have considerable "bleeding" of scene radiance into adjacent pixels, causing errors in application of multispectral scientific algorithms. Recently, we created end-to-end models that optimize end scientific data products by considering the payload design and data processing algorithms together, rather than simply satisfying a payload specification. In this process, we uncovered optimal payload design points and insights. We explore end-to-end modeling results that show an optimal single converged payload design, and data processing algorithms that produce simultaneous radiometer and imager products. We show how payload design choices for Instantaneous Field of View (IFOV) and Ground Sampling Distance (GSD) maximize SNR for multiple data products, resulting in an optimized design that increases flexibility of space assets. This approach is beneficial as we move towards distributed and fused image systems.

Accurate and automatic image navigation and registration (INR) of remotely sensed data will be an essential element of future NASA satellite observation systems. INR describes the process by which geographic locations of the image pixels are computed and successive images from the same sensor are aligned to each other over time. For sensors such as the Advanced Geosynchronous Studies Imager (AGSI), a number of distortions prevent successive images from being perfectly registered to each other or to a fixed coordinate system. Most distortions in such images are the combined effects of sensor operation, satellite orbit and attitude, and atmospheric and terrain effects. These distortions are usually corrected by two methods; systematic correction, which relies on image acquisition models taking into account satellite orbit and attitude, sensor characteristics, platform/sensor relationship, and terrain models, and precision correction, which is feature-based, starting from the result of the systematic correction, and refining the geolocation or relative registration to subpixel precision. This paper describes the AGSI INR requirements and concepts, the image navigation model, a description of some potential precision correction methods utilizing edge and wavelet features, and a study of all the different error sources. The issues of swath-to-swath correlation and channel-to- channel coregistration are also described.

This paper demonstrates improvements in GOES on-orbit Image Navigation and Registration (INR) performance obtained from a careful method of landmark selection, coupled with changes in landmark measurement techniques. An iterative process was used which began with a search for characteristics influencing landmark stability over time, such as topography, thermal changes, and apparent sea/land boundaries, and ended with measurable improvements in the areas of navigation, within- frame, frame-to-frame, and channel-to-channel registration. An operational shift from manual to automatic landmark correlation proved to be an essential requirement influencing the overall results. Specification requirements are used as an absolute means to estimate INR performance changes for GOES 8, but whenever possible, results obtained here are also placed in perspective by comparison with previous GOES INR results. Finally, the methodology and tools described are applied to the new GOES 10 satellite in order to estimate its performance.

An independent audit of the in-orbit behavior of the GOES-8 and GOES-9 satellites has been conducted for the NASA/GSFC. This audit utilized star and landmark observations from the GOES imager to determine long-term histories for spacecraft attitude, orbital position, and instrument internal misalignments. The paper presents results from this audit. Long-term drifts are found in the attitude histories, whereas the misalignment histories are shown to be diurnally stable. The GOES image navigation and registration system is designed to compensate for instrument internal misalignments, and both the diurnally repeatable and drift components of the attitude. Correlations between GOES-8 and GOES-9 long-term roll and pitch drifts implicate the Earth sensor as the origin of these observed drifts. This results clearly demonstrates the enhanced registration stability to be obtained with stellar inertial attitude determination replacing or supplementing Earth sensor control on future GOES missions.

Aspercyclide A (1) is a biaryl ether containing 11-membered macrocyclic natural product antagonist of the human IgE-FcεRI protein-protein interaction (PPI); a key interaction in the signal transduction pathway for allergic disorders such as asthma. Herein we report a novel approach to the synthesis of the C19 methyl ether of aspercyclide A, employing a Pd(0)-catalysed, fluorous-tagged alkenylgermane/arylbromide macrocyclisation (germyl-Stille reaction) as the key step, and evaluation of both enantiomers of this compound via ELISA following optical resolution by CSP-HPLC. A crystal structure for germyl hydride 27 is also reported.

We give the superspace formulation of different versions of the D = 10, N = 2a supergravity theory. The complete supersymmetry transformations for both the massless and massive theories are given.

A one-dimensional multiple scattering model for low energy electron diffraction in the normal geometry is proposed. This model reduces to the regular or a modified kinematic approximation in the weak scattering limit. The one-dimensional multiple scattering model is applied to Xe(111), Ni(001) and Cu(001). The results with Xe(111) are very encouraging in that the calculated LEED spectral peak energies and intensities agree well with experiment. The Ni(001) and Cu(001) results are also encouraging. Although only half the peaks present in the experimental data are present in the Ni(001) and Cu(001) calculated spectra, those peaks present in the calculated spectra are in agreement with the experimental spectra. The authors hypothesize that these missing peaks can be explained by the alternating filled and vacant site structure of (001) planes in face centered cubic crystals.

A method of constructing reducible supergravity multiplets from other super-gravity multiplets is described. The method is to expand the reducible multiplet's covariant derivatives in terms of another multiplet's covariant derivatives, Lorentz group generators and charge operators, using superfield expansion coefficients. A sketch of the construction of the '16+16' multiplet from the 'minimal 12+12' and '4+4' multiplets is used as an example. Also included are the solutions for the Bianchi identities for the 'minimal 12+12' and the 'new minimal 12+12' multiplets. This exhibits their superfield content and corrects a previously published result (Gates et al. 1983).

A one-dimensional multiple scattering model is used to construct a model for normal photoelectron diffraction (NPD). The model which is an extension of earlier work on NPD and which we recently applied to LEED with some success, proves successful in interpreting experimental NPD data of Se(3d), S(2p) and O(1s) on Ni(001). The model can be used to rapidly estimate NPD structural parameters such as d from experimental data. In addition, we exhibit NPD spectra for the fictitious adsorbate Ni(001)Ni and Cu(001)Cu systems. When these spectra masquerade as LEED spectra, they exhibit the observed secondary peaks absent in the simple one-dimensional calculated LEED spectra but present experimentally. This calculation complements our previous work showing how the normal geometry LEED data on Ni(001) and Cu(001) can be described in a one-dimensional model.

The relationship between spin structures and superworldsheet topology is shown by the construction of superworldsheets in which the anticommuting coordinates of different coordinate patches are stitched together in non-trivial ways. The four spin structures of the NSR string, corresponding to R-R, NS-NS, NS-R and R-NS boundary conditions are shown to arise as a consequence of topology. More interesting is the existence of more complicated twisted spin structures for the NSR string with N=2 worldsheet supersymmetry. This class of spin structures is also shown to exist for the heterotic string when its heterotic fermions are endowed with a bundle structure. The transformation of spin structures under field redefinitions and modular transformations are examined. Finally the spin structures associated with the ghost sector of the heterotic string are explored.