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The NASA Ionospheric Connection Explorer (ICON) was launched in October 2019 and has been observing the upper atmosphere and ionosphere to understand the sources of their strong variability, to understand the energy and momentum transfer, and to determine how the solar wind and magnetospheric effects modify the internally-driven atmosphere-space system. The Far Ultraviolet Instrument (FUV) supports these goals by observing the ultraviolet airglow in day and night, determining the atmospheric and ionospheric composition and density distribution. Based on the combination of ground calibration and flight data, this paper describes how major instrument parameters have been verified or refined since launch, how science data are collected, and how the instrument has performed over the first 3 years of the science mission. It also provides a brief summary of science results obtained so far. [ABSTRACT FROM AUTHOR]

One of the objectives of the Far UltraViolet (FUV) imager on the Ionospheric Connection Explorer (ICON) spacecraft is to make high resolution images of the nighttime near equatorial oxygen 135.6 nm airglow emission. This emission is largely the product of O+ ion re-combination and therefore the emission intensity is a proxy for remote measurement of ionospheric density. The ICON FUV instrument is capable of high resolution imaging of the night glow by viewing the Earth's limb from above on the left side of the spacecraft and taking rapid exposures and co-adding the resultant images for 12 seconds. To improve the resolution and compress the resulting data a new type of Time Delay Integration (TDI) technique was developed, which involves transforming the images into a distorted frame so that the displacement due to orbital motion becomes a singular constant vector for all pixels. Operating in this transformed frame it is possible to co-add and shift the images to retain the resolution and minimize the required data bandwidth. The transformation needs modeling of the object distance for all pixels. Two models, the "limb" and "sub-limb" models, are used for transforming the upper and lower parts of the ICON FUV images, respectively. At the input of the instrument there is a rotatable mirror, which allows directing the optic axis near to the plane of the local magnetic field. The images are co-added for 12 sec and are down linked and re-assembled on the ground into maps of the O emission showing an entire night pass. This is the first report on the performance of this newly developed TDI system. ICON with its low inclination (27 degree) orbit provides an extensive longitudinal coverage on each orbit complementing the coverage of GOLD or TIMED. During 179 orbits in October 2021 ICON FUV saw significant nighttime ion densities on 76% of the orbits. At low latitudes the ionization was clearly associated with the equatorial ionospheric anomaly (EIA). The maps showed significant structuring during 34% of the orbits when ICON was in the position to view the EIA. In coordinated observations GOLD and ICON FUV observed regular structuring in the form of Equatorial Plasma Bubbles (EPB-s). Comparing to GOLD observations in 2018, ICON saw significantly fewer EPB-s in the month of October 2021. ICON TDI integrated sub-limb view was tested for resolution using star images and should have seen structures less than 10 km. From the 179 orbits taken in October 2021 the shortest repetition EPB-were 350 km from peak to peaks. [ABSTRACT FROM AUTHOR]

Subauroral emissions known as STEVEs (Strong Thermal Emission Velocity Enhancements) are sometimes accompanied by green arcs containing magnetic field‐aligned "picket fence" structures. In a newly published spectrum of a green picket fence arc Gillies et al. (2019, https://doi.org/10.1029/2019GL083272) showed that the visible emission in such arcs is mostly OI 557.7 nm with minimal N2+ 1N. This finding is consistent with the color ratios found in digital camera photos (Mende & Turner, 2019, https://doi.org/10.1029/2019JA026851) and is distinct from the ratios in auroral precipitation. The spectrum also contains intense N2 first positive (1P) emission. The presence of OI 557.7 (~4.19 eV excitation energy) and N2 1P (~7.35 eV), combined with the lack of N2+ first negative (~18.75 eV) commonly seen in the aurora, suggests that the particles exciting the emission have energy <18.75 eV. This is strong evidence against the precipitation hypothesis recently put forth (Nishimura et al., 2019, https://doi.org/10.1029/2019GL082460; Gillies et al., 2019, https://doi.org/10.1029/2019GL083272). Key Points: Recent spectra of a green STEVE arc shows intense 557.7 nm OI and N2 1P nitrogen emission in the IR but minimal N2+ 1N in the blueColor ratios in photos of the green "picket fence" arcs are consistent with the spectrospcopic resultsSpectra and the color ratios show low energy excitation which is inconsistent with auroral source from the magnetosphere [ABSTRACT FROM AUTHOR]

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of $\mathrm{O}^{+}$ ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a Czerny-Turner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft. [ABSTRACT FROM AUTHOR]

Lactose-free dairy products become increasingly important for lactose-intolerant consumers, but there are only few studies concerning the rheological properties of fermented dairy products from lactose-hydrolysed milk. Hydrolysation was performed with commercial β-galactosidase either before or during fermentation (co-hydrolysis). In each trial, fermentation of the base milk was carried out simultaneously using the same starter cultures for (a) untreated milk (reference) (b) hydrolysed milk as substrate and (c) by performing lactose hydrolysis and fermentation simultaneously (co-hydrolysis). In total, five thermophilic starter cultures and two products (yoghurt and Greek-style yoghurt) were investigated. Results show that the influence of hydrolysis of lactose on the properties of the fermented dairy products strongly depends on starter culture and substrate. For starters C and D, apparent viscosity (extracted from flow curves at a shear rate of 75 s) of fermented milks was only marginally affected by lactose hydrolysis, ranging between approx. 0.34-0.31 and 0.37-0.31 Pa.s, respectively. Hydrolysed products from starters A and E exhibited significant lower apparent viscosity (0.16 and 0.24 Pa.s) compared with their respective references (0.29 and 0.35 Pa.s). Fermentation of both substrates (regular yoghurt, Greek-style yoghurt) with starter B resulted in a decrease of yield stress and apparent viscosity because of lactose hydrolysis only for Greek-style yoghurt. Furthermore, a trend towards higher EPS synthesis was found when using hydrolysed milk. The results clearly show that products made from lactose-hydrolysed milk with similar rheological properties as the reference product can be obtained but that there is a lack of information concerning the complex interactions between starter culture and milk substrate. [ABSTRACT FROM AUTHOR]

Coupling of the solar wind to the Earth magnetosphere/ionosphere is primarily through the high latitude regions, and there are distinct advantages in making remote sensing observations of these regions with a network of ground-based observatories over other techniques. The Antarctic continent is ideally situated for such a network, especially for optical studies, because the larger offset between geographic and geomagnetic poles in the south enables optical observations at a larger range of magnetic latitudes during the winter darkness. The greatest challenge for such ground-based observations is the generation of power and heat for a sizable ground station that can accommodate an optical imaging instrument. Under the sponsorship of the National Science Foundation, we have developed suitable automatic observing platforms, the Automatic Geophysical Observatories (AGOs) for a network of six autonomous stations on the Antarctic plateau. Each station housed a suite of science instruments including a dual wavelength intensified all-sky camera that records the auroral activity, an imaging riometer, fluxgate and search-coil magnetometers, and ELF/VLF and LM/MF/HF receivers. Originally these stations were powered by propane fuelled thermoelectric generators with the fuel delivered to the site each Antarctic summer. A by-product of this power generation was a large amount of useful heat, which was applied to maintain the operating temperature of the electronics in the stations. Although a reasonable degree of reliability was achieved with these stations, the high cost of the fuel air lift and some remaining technical issues necessitated the development of a different type of power unit. In the second phase of the project we have developed a power generation system using renewable energy that can operate automatically in the Antarctic winter. The most reliable power system consists of a type of wind turbine using a simple permanent magnet rotor and a new type of power control system with variable resistor shunts to regulate the power and dissipate the excess energy and at the same time provide heat for a temperature controlled environment for the instrument electronics and data system. We deployed such systems and demonstrated a high degree of reliability in several years of operation in spite of the relative unpredictability of the Antarctic environment. Sample data are shown to demonstrate that the AGOs provide key measurements, which would be impossible without the special technology developed for this type of observing platform. [ABSTRACT FROM AUTHOR]

The NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) project is intended to investigate magnetospheric substorm phenomena, which are the manifestations of a basic instability of the magnetosphere and a dominant mechanism of plasma transport and explosive energy release. The major controversy in substorm science is the uncertainty as to whether the instability is initiated near the Earth, or in the more distant >20 Re magnetic tail. THEMIS will discriminate between the two possibilities by using five in-situ satellites and ground-based all-sky imagers and magnetometers, and inferring the propagation direction by timing the observation of the substorm initiation at multiple locations in the magnetosphere. An array of stations, consisting of 20 all-sky imagers (ASIs) and 30-plus magnetometers, has been developed and deployed in the North American continent, from Alaska to Labrador, for the broad coverage of the nightside magnetosphere. Each ground-based observatory (GBO) contains a white light imager that takes auroral images at a 3-second repetition rate (“cadence”) and a magnetometer that records the 3 axis variation of the magnetic field at 2 Hz frequency. The stations return compressed images, “thumbnails,” to two central databases: one located at UC Berkeley and the other at the University of Calgary, Canada. The full images are recorded at each station on hard drives, and these devices are physically returned to the two data centers for data copying. All data are made available for public use by scientists in “browse products,” accessible by using internet browsers or in the form of downloadable CDF data files (the “browse products” are described in detail in a later section). Twenty all-sky imager stations are installed and running at the time of this publication. An example of a substorm was observed on the 23rd of December 2006, and from the THEMIS GBO data, we found that the substorm onset brightening of the equatorward arc was a gradual process (>27 seconds), with minimal morphology changes until the arc breaks up. The breakup was timed to the nearest frame (<3 s) and located to the nearest latitude degree at about ±3oE in longitude. The data also showed that a similar breakup occurred in Alaska ∼10 minutes later, highlighting the need for an array to distinguish prime onset. [ABSTRACT FROM AUTHOR]

The comprehensive THEMIS approach to solving the substorm problem calls for monitoring the nightside auroral oval with low-cost, robust white-light imagers and magnetometers that can deliver high time resolution data (0.33 and 2 Hz, respectively). A network of 20 Ground-Based Observatories (GBOs) are deployed across Canada and Alaska to support the collection of data from these instruments. Here we describe the system design of the observatory, with emphasis on how the design meets the environmental and data-collection requirements. We also review the design of the All Sky Imager (ASI), discuss how it was built to survive Arctic deployments, and summarize the optical characterizations performed to qualify the design to meet THEMIS mission requirements. [ABSTRACT FROM AUTHOR]

A joined research project between the Technical University of Braunschweig and the Technical University of München investigates the possibilities for the production of stable product suspensions in a particle size range smaller than 100 nm. In this paper results for comminution of fused corundum showing the influence of the electrostatic stabilization at different pH-values on the grinding progress and the grinding media wear are presented. Furthermore, by means of experimental results the influence of the grinding media diameter and the stirrer tip speed is discussed. [ABSTRACT FROM AUTHOR]

Helium nanodroplets are doped with metal atoms by means of laser evaporation. The material is evaporated directly in front of the helium nozzle by a pulsed laser. In comparison with conventional pickup from an oven we deduce that the droplets can be loaded with more than one atom per droplet on average. Conditions and efficiencies for loading are evaluated. Furthermore, metal ions can be attached to helium droplets by this method, allowing isolation of charged particles at temperatures below 1 K. In this way we can directly measure size distributions of helium nanodroplets which are compared to results using other techniques. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A joint research project between the Technical University of Braunschweig and the Technical University of Mu¨nchen investigates the possibilities for the production of stable product suspensions in a particle size range smaller than 100 nm. This paper shows the experimental setup which allows the measurement of the most important electrochemical properties and the analysis of the particle size distribution of the product suspension as well as an adjustment of the pH value for stabilization during the comminution process. Results for comminution of fused corundum with different grinding media materials and grinding media sizes are shown. In addition, results showing the influence of the electrostatic stabilization on the grinding progress are presented. Further, the rheology of the product suspension is examined depending on grinding progress and suspension stability. [Copyright &y& Elsevier]

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. This connection is made in the ionosphere, which has long been known to exhibit variability associated with the sun and solar wind. However, it has been recognized in the 21st century that equally significant changes in ionospheric conditions are apparently associated with energy and momentum propagating upward from our own atmosphere. ICON's goal is to weigh the competing impacts of these two drivers as they influence our space environment. Here we describe the specific science objectives that address this goal, as well as the means by which they will be achieved. The instruments selected, the overall performance requirements of the science payload and the operational requirements are also described. ICON's development began in 2013 and the mission is on track for launch in 2018. ICON is developed and managed by the Space Sciences Laboratory at the University of California, Berkeley, with key contributions from several partner institutions. [ABSTRACT FROM AUTHOR]

The Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) was launched aboard NASA's Ionospheric Connection (ICON) Explorer satellite in October 2019 to measure winds and temperatures on the limb in the upper mesosphere and lower thermosphere (MLT). Temperatures are observed using the molecular oxygen atmospheric band near 763 nm from 90–127 km altitude in the daytime and 90–108 km in the nighttime. Here we describe the measurement approach and methodology of the temperature retrieval, including unique on-orbit operations that allow for a better understanding of the instrument response. The MIGHTI measurement approach for temperatures is distinguished by concurrent observations from two different sensors, allowing for two self-consistent temperature products. We compare the MIGHTI temperatures against existing MLT space-borne and ground-based observations. The MIGHTI temperatures are within 7 K of these observations on average from 90–95 km throughout the day and night. In the daytime on average from 99–105 km, MIGHTI temperatures are higher than coincident observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on NASA's TIMED satellite by 18 K. Because the difference between the MIGHTI and SABER observations is predominantly a constant bias at a given altitude, conclusions of scientific analyses that are based on temperature variations are largely unaffected. [ABSTRACT FROM AUTHOR]

We present a method for estimating incident photoelectrons' energy spectra as a function of altitude by combining global scale far‐ultraviolet (FUV) and radio‐occultation (RO) measurements. This characterization provides timely insights important for accurate interpretation of ionospheric parameters inferred from the recently launched Ionospheric Connection Explorer (ICON) observations. Quantification of photoelectron impact is enabled by the fact that conjugate photoelectrons (CPEs) directly affect FUV airglow emissions but not RO measurements. We demonstrate a technique for estimation of photoelectron fluxes and their spectra by combining coincident ICON and COSMIC2 measurements and show that a significant fraction of ICON‐FUV measurements is affected by CPEs during the winter solstice. A comparison of estimated photoelectron fluxes with measured photoelectron spectra is used to gain further insights into the estimation method and reveals consistent values within 10–60 eV. Plain Language Summary: The impact of solar radiation on the atmosphere produces highly energetic electrons, which travel freely along the magnetic Earth's field lines from one hemisphere to the other. When these electrons flow from the sunlit side into the nightside hemisphere, they interact with the neutral species and produce noticeable effects in the ionosphere such as an increase in electron temperature and enhancement of airglow emissions. This study presents a method to quantify the amount of precipitating electrons and their energy on a global scale using two recent satellite missions, ICON and COSMIC2. Our results demonstrate that coincident far‐ultraviolet (ICON) and radio‐occultation (COSMIC2) measurements from space are valuable resources to study precipitating electrons in the ionosphere and their impact on inferring ionospheric plasma parameters. Key Points: Nightglow emissions excited by photoelectrons originating in the magnetically conjugate hemisphere are observed by the ICON missionConjugate photoelectron energy spectra are derived for the first time using global scale far‐ultraviolet and radio‐occultation observationsComparison of estimated photoelectron fluxes with measurements on a rocket flight shows consistent characteristics at all altitudes [ABSTRACT FROM AUTHOR]

The article reports on scientific research on closed magnetic flux trapped in the high-latitude magnetosphere. Topics discussed include poor scientific understaing about the Earth’s magnetosphere when the interplanetary magnetic field is northward; satellite observation which show lobe plasma signatures occur on high-latitude magnetic field lines; and the fundamental plasma process of magnetic reconnection.

Pulsating aurora, a spectacular emission that appears as blinking of the upper atmosphere in the polar regions, is known to be excited by modulated, downward-streaming electrons. Despite its distinctive feature, identifying the driver of the electron precipitation has been a long-standing problem. Using coordinated satellite and ground-based all-sky imager observations from the THEMIS mission, we provide direct evidence that a naturally occurring electromagnetic wave, lower-band chorus, can drive pulsating aurora. Because the waves at a given equatorial location in space correlate with a single pulsating auroral patch in the upper atmosphere, our findings can also be used to constrain magnetic field models with much higher accuracy than has previously been possible. [ABSTRACT FROM AUTHOR]

THEMIS was launched on February 17, 2007 to determine the trigger and large-scale evolution of substorms. During the first seven months of the mission the five satellites coasted near their injection orbit to avoid differential precession in anticipation of orbit placement, which started in September 2007 and led to a commencement of the baseline mission in December 2007. During the coast phase the probes were put into a string-of-pearls configuration at 100 s of km to 2 RE along-track separations, which provided a unique view of the magnetosphere and enabled an unprecedented dataset in anticipation of the first tail season. In this paper we describe the first THEMIS substorm observations, captured during instrument commissioning on March 23, 2007. THEMIS measured the rapid expansion of the plasma sheet at a speed that is commensurate with the simultaneous expansion of the auroras on the ground. These are the first unequivocal observations of the rapid westward expansion process in space and on the ground. Aided by the remote sensing technique at energetic particle boundaries and combined with ancillary measurements and MHD simulations, they allow determination and mapping of space currents. These measurements show the power of the THEMIS instrumentation in the tail and the radiation belts. We also present THEMIS Flux Transfer Events (FTE) observations at the magnetopause, which demonstrate the importance of multi-point observations there and the quality of the THEMIS instrumentation in that region of space. [ABSTRACT FROM AUTHOR]

Abstract: The overarching objective of the ILWS Geospace program is to facilitate system level science. This demands synoptic observations such as global auroral imaging. At present, there is no funded mission during ILWS that incorporates a global auroral imager. The imaging community needs to move now to address this important gap. While doing so, it is interesting to take stock of global auroral observations that have not been achieved, or that have been achieved only to a limited extent. These include simultaneous imaging across all relevant scales, spectral resolution of sufficient quality to allow for global maps of characteristic energy and energy flux of precipitating electrons, continuous global auroral imaging for time periods spanning long-duration geomagnetic events, systematic interhemispheric conjugate observations, auroral observations magnetically conjugate to in situ measurements, and automatic classification of auroral images. These observations can be achieved within the next decade. If they are, then they will facilitate exciting new science. [Copyright &y& Elsevier]

The most important process that allows solar-wind plasma to cross the magnetopause and enter Earth's magnetosphere is the merging between solar-wind and terrestrial magnetic fields of opposite sense-magnetic reconnection. It is at present not known whether reconnection can happen in a continuous fashion or whether it is always intermittent. Solar flares and magnetospheric substorms-two phenomena believed to be initiated by reconnection-are highly burst-like occurrences, raising the possibility that the reconnection process is intrinsically intermittent, storing and releasing magnetic energy in an explosive and uncontrolled manner. Here we show that reconnection at Earth's high-latitude magnetopause is driven directly by the solar wind, and can be continuous and even quasi-steady over an extended period of time. The dayside proton auroral spot in the ionosphere-the remote signature of high-latitude magnetopause reconnection-is present continuously for many hours. We infer that reconnection is not intrinsically intermittent; its steadiness depends on the way that the process is driven. [ABSTRACT FROM AUTHOR]