The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

An examination of the local meteorology and chemical processes that lead to the simultaneous rise of ozone and fall of NOx in the morning.

A better understanding of exactly what causes measured O3 mixing ratio increases in the mid-morning to early afternoon time period over rural northern Michigan was sought by this study. Four separate instances of increased O3 mixing ratios were examined in detail looking at a wide variety of meteorological and chemical variables. An attempt was made in all of these cases to determine the extent to which the mixing ratio increase could have been caused by photochemical production, boundary layer entrainment and/or horizontal advection. Examples of all three phenomenon were encountered. Meteorological parameters at the Program for Research on Oxidants, PHotochemistry, Emissions, and Transport (PROPHET) tower were compared with meteorological parameters at the UV-B site and were found to be similar. Mixed layer height determination made at the UV-B site were thus considered to be useful to examine O3 and NOx data collected at the PROPHET tower.http://deepblue.lib.umich.edu/bitstream/2027.42/54923/1/3364.pdfDescription of 3364.pdf : Access restricted to on-site users at the U-M Biological Station

Direct measurement of volatile organic compound emissions from industrial flares using real-time online techniques: Proton Transfer Reaction Mass Spectrometry and Tunable Infrared Laser Differential Absorption Spectroscopy

During the 2010 Comprehensive Flare Study a suite of analytical instrumentation was employed to monitor and quantify in real-time the volatile organic compound (VOC) emissions emanating from an industrial chemical process flare burning either propene/natural gas or propane/natural gas. To our knowledge this represents the first time the VOC composition has been directly measured as a function of flare efficiency on an operational full-scale flare. This compositional information was obtained using a suite of proton-transfer-reaction mass spectrometers (PTR-MS) and quantum cascade laser tunable infrared differential absorption spectrometers (QCL-TILDAS) to measure the unburned fuel and associated combustion byproducts. Methane, ethyne, ethene, and formaldehyde were measured using the QC-TILDAS. Propene, acetaldehyde, methanol, benzene, acrolein, and the sum of the C₃H₆O isomers were measured with the PTR-MS. A second PTR-MS equipped with a gas chromatograph (GC) was operated in parallel and was used to verify the identity of the neutral components that were responsible for producing the ions monitored with the first PTR-MS. Additional components including 1,3-butadiene and C₃H₄ (propyne or allene) were identified using the GC/PTR-MS. The propene concentrations derived from the PTR-MS were found to agree with measurements made using a conventional GC with a flame ionization detector (FID). The VOC product (excludes fuel components) speciation profile is more dependent on fuel composition, propene versus propane, than on flare type, air-assisted versus steam-assisted, and is essentially constant with respect to combustion efficiency for combustion efficiencies >0.8. Propane flares produce more alkenes with ethene and propene accounting for approximately 80% (per carbon basis) of the VOC combustion product. The propene partial combustion product profile was observed to contain relatively more oxygenated material where formaldehyde and acetaldehyde are major contributors and account for ∼20 - 25% of VOC product carbon. Steam-assisted flares produce less ethyne and benzene than air-assisted flares. This observation is consistent with the understanding that steam assisted flares are more efficient at reducing soot, which is formed via the same reaction mechanisms that form benzene and ethyne

Data from: Analysis of local-scale background concentrations of methane and other gas-phase species in the Marcellus Shale

The Marcellus Shale is a rapidly developing unconventional natural gas resource found in part of the Appalachian region. Air quality and climate concerns have been raised regarding development of unconventional natural gas resources. Two ground-based mobile measurement campaigns were conducted to assess the impact of Marcellus Shale natural gas development on local scale atmospheric background concentrations of air pollution and climate relevant pollutants in Pennsylvania. The first campaign took place in Northeastern and Southwestern PA in the summer of 2012. Compounds monitored included methane (CH4), ethane, carbon monoxide (CO), nitrogen dioxide, and Proton Transfer Reaction Mass Spectrometer (PTR-MS) measured volatile organic compounds (VOC) including oxygenated and aromatic VOC. The second campaign took place in Northeastern PA in the summer of 2015. The mobile monitoring data were analyzed using interval percentile smoothing to remove bias from local unmixed emissions to isolate local-scale background concentrations. Comparisons were made to other ambient monitoring in the Marcellus region including a NOAA SENEX flight in 2013. Local background CH4 mole fractions were 140 ppbv greater in Southwestern PA compared to Northeastern PA in 2012 and background CH4 increased 100 ppbv from 2012 to 2015. CH4 local background mole fractions were not found to have a detectable relationship between well density or production rates in either region. In Northeastern PA, CO was observed to decrease 75 ppbv over the three year period. Toluene to benzene ratios in both study regions were found to be most similar to aged rural air masses indicating that the emission of aromatic VOC from Marcellus Shale activity may not be significantly impacting local background concentrations. In addition to understanding local background concentrations the ground-based mobile measurements were useful for investigating the composition of natural gas emissions in the region

Analysis of local-scale background concentrations of methane and other gas-phase species in the Marcellus Shale

The Marcellus Shale is a rapidly developing unconventional natural gas resource found in part of the Appalachian region. Air quality and climate concerns have been raised regarding development of unconventional natural gas resources. Two ground-based mobile measurement campaigns were conducted to assess the impact of Marcellus Shale natural gas development on local scale atmospheric background concentrations of air pollution and climate relevant pollutants in Pennsylvania. The first campaign took place in Northeastern and Southwestern PA in the summer of 2012. Compounds monitored included methane (CH4), ethane, carbon monoxide (CO), nitrogen dioxide, and Proton Transfer Reaction Mass Spectrometer (PTR-MS) measured volatile organic compounds (VOC) including oxygenated and aromatic VOC. The second campaign took place in Northeastern PA in the summer of 2015. The mobile monitoring data were analyzed using interval percentile smoothing to remove bias from local unmixed emissions to isolate local-scale background concentrations. Comparisons were made to other ambient monitoring in the Marcellus region including a NOAA SENEX flight in 2013. Local background CH4 mole fractions were 140 ppbv greater in Southwestern PA compared to Northeastern PA in 2012 and background CH4 increased 100 ppbv from 2012 to 2015. CH4 local background mole fractions were not found to have a detectable relationship between well density or production rates in either region. In Northeastern PA, CO was observed to decrease 75 ppbv over the three year period. Toluene to benzene ratios in both study regions were found to be most similar to aged rural air masses indicating that the emission of aromatic VOC from Marcellus Shale activity may not be significantly impacting local background concentrations. In addition to understanding local background concentrations the ground-based mobile measurements were useful for investigating the composition of natural gas emissions in the region

Supplementary Tables S6 and Table S7 for Emission factors from wildfires in the Western US – An investigation of burning state, ground versus air, and diurnal dependencies during the FIREX-AQ 2019 campaign

Supplementary Tables S6 and Table S7 "Emission factors from wildfires in the Western US – An investigation of burning state, ground versus air, and diurnal dependencies during the FIREX-AQ 2019 campaign" to JGR-Atmosphere: </p

Atmospheric Emission Characterization of Marcellus Shale Natural Gas Development Sites

Limited direct measurements of criteria pollutants emissions and precursors, as well as natural gas constituents, from Marcellus shale gas development activities contribute to uncertainty about their atmospheric impact. Real-time measurements were made with the Aerodyne Research Inc. Mobile Laboratory to characterize emission rates of atmospheric pollutants. Sites investigated include production well pads, a well pad with a drill rig, a well completion, and compressor stations. Tracer release ratio methods were used to estimate emission rates. A first-order correction factor was developed to account for errors introduced by fenceline tracer release. In contrast to observations from other shale plays, elevated volatile organic compounds, other than CH₄ and C₂H₆, were generally not observed at the investigated sites. Elevated submicrometer particle mass concentrations were also generally not observed. Emission rates from compressor stations ranged from 0.006 to 0.162 tons per day (tpd) for NO_<i>x</i>, 0.029 to 0.426 tpd for CO, and 67.9 to 371 tpd for CO₂. CH₄ and C₂H₆ emission rates from compressor stations ranged from 0.411 to 4.936 tpd and 0.023 to 0.062 tpd, respectively. Although limited in sample size, this study provides emission rate estimates for some processes in a newly developed natural gas resource and contributes valuable comparisons to other shale gas studies