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The total solar irradiance (TSI) is Earth’s primary source of energy, and accurate knowledge of its value and variability is crucial for understanding Earth’s climate and variability. In order to continue the existing 44 year data record... more
The total solar irradiance (TSI) is Earth’s primary source of energy, and accurate knowledge of its value and variability is crucial for understanding Earth’s climate and variability. In order to continue the existing 44 year data record of TSI measurements from space, NASA is developing the Total and Spectral Irradiance Sensors (TSIS) -2 mission. TSIS-2 consists of the Total Irradiance Monitor (TIM) and Spectral Irradiance Monitor (SIM) on a free flyer satellite, with an anticipated launch in the latter half of 2024. The TSIS-2/TIM is the latest iteration of the TIM instrument, prior versions of which flew onboard the SORCE, TCTE and TSIS-1 missions, and a direct rebuild of the TSIS-1 instrument. We present the pre-flight ground calibration of the TSIS-2/TIM instrument and its uncertainties. A key difference between the calibrations of the TSIS-1 and TSIS-2 instruments is the use of a novel low noise ambient temperature radiometer for TSIS-2 that significantly reduces the uncertain...
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This work describes two achievements to a key data set. First, we present version 2 of the Total and Spectral Solar Irradiance Sensor‐1 Hybrid Solar Reference Spectrum (TSIS‐1 HSRS), which has recently been recognized as a new solar... more
This work describes two achievements to a key data set. First, we present version 2 of the Total and Spectral Solar Irradiance Sensor‐1 Hybrid Solar Reference Spectrum (TSIS‐1 HSRS), which has recently been recognized as a new solar irradiance reference standard (https://calvalportal.ceos.org/). Second, we present a new “full spectrum extension” of the TSIS‐1 HSRS. The TSIS‐1 HSRS observational composite solar irradiance reference spectrum spans 0.202–2.730 μm and encompasses more than 97% of the energy in the total solar irradiance (TSI). Version 2 is an incremental update that corrects the radiometric baseline between 0.202 and 0.210 μm and updates the solar lines at wavelengths longward of 0.743 μm to those listed in the most recent database. The full spectrum extension builds off version 2 of the TSIS‐1 HSRS and supports applications that require a solar spectrum encompassing nearly 100% of the energy in the TSI. It spans 0.115–200 μm and was developed by incorporating additiona...
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1. R. A. Walker, E. C. Richard, K.-T. Lu, E. L. Sibert III, J. C. Weisshaar, J. Chem, Phys., in press.
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NASA's Total and Spectral Solar Irradiance Sensor -1 (TSIS-1) operates on the International Space Station. TSIS-1 provides absolute measurements of the total solar irradiance (TSI) and spectral solar irradiance (SSI), important for... more
NASA's Total and Spectral Solar Irradiance Sensor -1 (TSIS-1) operates on the International Space Station. TSIS-1 provides absolute measurements of the total solar irradiance (TSI) and spectral solar irradiance (SSI), important for accurate scientific models of climate change and solar variability. TSIS-1 is comprised of two instruments, the Total Irradiance Monitor (TIM), and the Spectral Irradiance Monitor (SIM). This repository archives Version 6 (V06) of the TSIS-1 SIM Level 3 (L3) data release, and contains SSI in two cadences, 12-hour and 24-hour. Data is archived in ASCII, and IDL SAVfile format. See the attached release notes for further details.
The Solar Radiation and Climate Experiment (SORCE) and Total and Spectral Irradiance Sensor (TSIS‐1) conducted an intercomparison for the two Spectral Irradiance Monitors (SIM) spanning 704 days from 23 March 2018 to 25 February 2020 and... more
The Solar Radiation and Climate Experiment (SORCE) and Total and Spectral Irradiance Sensor (TSIS‐1) conducted an intercomparison for the two Spectral Irradiance Monitors (SIM) spanning 704 days from 23 March 2018 to 25 February 2020 and permitted 554 time‐matched pairs of observations. This comparison was conducted during the extremely quiescent Solar Cycle 24 minimum, so all observed differences and drifts between the two sensors are instrumental in nature. The TSIS‐1 SIM benefitted from advanced calibration capabilities based on SI standards that were not available during the preflight calibration time period of SORCE. For this reason, a revision of the SORCE SIM absolute scale is appropriate. As expected, wavelength dependent differences in absolute agreement are a function of detector sensitivity and local changes in spectral slope. At the time of the comparison SORCE SIM has been on‐orbit for 17 years while TSIS‐1 observations commenced immediately after a 100‐day outgassing and commissioning period. Peak‐to‐peak absolute scale differences are about 12% with a mean fractional difference of 0.7% ± 2.9%. The greatest scale differences occur at the change‐over between the UV and visible photodiodes in the 310 nm region, and a systematic disagreement is present in the 850–1,600 nm range. A multiplicative scale correction factor has been developed to reconcile the TSIS‐1 and SORCE difference with a wavelength dependent error on the mean typically less than 0.01% derived from every matched pair of observations.
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<p>Recently, we incorporated our new understanding of the absolute scale of the solar spectrum as measured by the Spectral Irradiance Monitor (SIM) on the Total and Spectral Solar Irradiance Sensor (TSIS-1) mission... more
<p>Recently, we incorporated our new understanding of the absolute scale of the solar spectrum as measured by the Spectral Irradiance Monitor (SIM) on the Total and Spectral Solar Irradiance Sensor (TSIS-1) mission and the Compact SIM (CSIM) flight demonstration into a solar irradiance reference spectrum representing solar minimum conditions between solar cycles 24 and 25. This new reference spectrum, called the TSIS-1 Hybrid Solar Reference Spectrum (HSRS), is developed by re-normalizing independent, very high spectral resolution datasets to the TSIS-1 SIM absolute irradiance scale. The high-resolution data are from the Airforce Geophysical Laboratory (AFGL), the Quality Assurance of Ultraviolet Measurements In Europe (QASUME) campaign, the Kitt Peak National Observatory (KPNO) and the Jet Propulsion Laboratory’s (JPL) Solar Pseudo-Transmittance Spectrum (SPTS). The TSIS-1 HSRS spans 0.202 µm to 2.73 µm and has a spectral resolution of 0.01 nm or better. Uncertainties are 0.3% between 0.4 and 2.365 mm and 1.3% at wavelengths outside that range</p><p>Recently, we have extended the long wavelength limit of the TSIS-1 HSRS from 2.73 µm to 200 µm with JPL SPTS solar line data through ~ 16 µm and theoretical understanding as represented in a computed solar irradiance spectrum by R. Kurucz. The extension expands the utility of this new solar irradiance reference spectrum to include Earth energy budget studies because it encompasses an integrated energy in excess of 99.99% of the total solar irradiance.</p><p>In this work, we discuss the TSIS-1 HSRS, the extension and uncertainties, and demonstrate consistency with TSIS-1 SIM and CSIM solar spectral irradiance observations and TSIS-1 Total Irradiance Monitor (TIM) total solar irradiance observations. Additionally, we compare the TSIS-1 HSRS against independent measured and modeled solar reference spectra.</p>
Currently at NIST, there is an effort to develop a black array of broadband absolute radiometers (BABAR) for far infrared sensing. The linear array of radiometer elements is based on uncooled vanadium oxide (VOx) microbolometer pixel... more
Currently at NIST, there is an effort to develop a black array of broadband absolute radiometers (BABAR) for far infrared sensing. The linear array of radiometer elements is based on uncooled vanadium oxide (VOx) microbolometer pixel technology but with the addition of two elements: vertically aligned carbon nanotubes (VACNTs) and an electrical substitution heater. Traditional microbolometer pixels use a thermistor film as an absorber, which is placed a quarter wavelength above a reflector, typically limiting absorption to a narrow band from 8 μm to 15 μm. To extend the sensing range of the imaging array into the far infrared (20 μm to 100 μm), we are replacing the cavity with a single absorber of VACNTs. In addition, each pixel has an electrical substitution heater which can be used to determine equivalent incident optical power when the device is non-illuminated. This device forms the basis of an absolute radiometer eliminating the need for an external reference (e.g. blackbody so...
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The Naval Research Laboratory’s (NRL) solar variability models estimate total solar irradiance (TSI) and solar spectral irradiance (SSI) changes from quiet Sun conditions due to the presence and evolution of bright faculae and dark... more
The Naval Research Laboratory’s (NRL) solar variability models estimate total solar irradiance (TSI) and solar spectral irradiance (SSI) changes from quiet Sun conditions due to the presence and evolution of bright faculae and dark sunspots are present on the solar disk. The NRLTSI2 and NRLSSI2 models are constructed from linear regression of proxies of solar sunspot and facular features with irradiance observations from the SOlar Radiation and Climate Experiment (SORCE). These models were transitioned in 2015 as the Solar Irradiance Climate Data Record to the National Oceanographic and Atmospheric Administration’s National Centers for Environmental Information Climate Data Record (CDR) Program. This Solar Irradiance CDR, operationally-produced and updated approximately every three months by the Laboratory for Atmospheric and Space Physics (LASP), is made available from 1610 to the present as yearly-average values and from 1882 to the present as monthlyand daily-averages, with assoc...
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We describe spectral and time-dependent variations in solar irradiance, discuss their implications for Earth science, and summarize ongoing work in developing the next generation of observationally-consistent models of solar irradiance... more
We describe spectral and time-dependent variations in solar irradiance, discuss their implications for Earth science, and summarize ongoing work in developing the next generation of observationally-consistent models of solar irradiance variability.
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Not only total solar irradiance (TSI) but also spectral solar irradiance (SSI) matter for our climate. Different surfaces can have different reflectivity for the visible (VIS) and near-infrared (NIR). The recent NASA Total and Spectral... more
Not only total solar irradiance (TSI) but also spectral solar irradiance (SSI) matter for our climate. Different surfaces can have different reflectivity for the visible (VIS) and near-infrared (NIR). The recent NASA Total and Spectral Solar Irradiance Sensor (TSIS-1) mission has provided more accurate SSI observations than before. The TSI observed by TSIS-1 differs from the counterpart used by climate models by no more than 1 W m−2. However, the SSI difference in a given VIS (e.g., 0.44–0.63 μm) and NIR (e.g., 0.78–1.24 μm) band can be as large as 4 W m−2 with opposite signs. Using the NCAR CESM2, we study to what extent such different VIS and NIR SSI partitions can affect the simulated climate. Two sets of simulations with identical TSI are carried out, one with SSI partitioning as observed by the TSIS-1 mission and the other with what has been used in the current climate models. Due to different VIS-NIR spectral reflectance contrasts between icy (or snowy) surfaces and open water, the simulation with more SSI in the VIS has less solar absorption by the high-latitude surfaces, ending up with colder polar surface temperature and larger sea ice coverage. The difference is more prominent over the Antarctic than over the Arctic. Our results suggest that, even for the identical TSI, the surface albedo feedback can be triggered by different SSI partition between the VIS and NIR. The results underscore the importance of continuously monitoring SSI and the use of correct SSI in climate simulations.
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An understanding of solar variability over a broad spectral range and broad range of timescales is needed by scientists studying Earth’s climate. The Total and Spectral Solar Irradiance Sensor (TSIS) Spectral Irradiance Monitor (SIM), is... more
An understanding of solar variability over a broad spectral range and broad range of timescales is needed by scientists studying Earth’s climate. The Total and Spectral Solar Irradiance Sensor (TSIS) Spectral Irradiance Monitor (SIM), is designed to measure solar spectral irradiance (SSI) with unprecedented accuracy from 200 nm to 2400 nm. SIM started daily observations in March 2018. To maintain its accuracy over the course of its anticipated 5-year mission and beyond, TSIS SIM needs to be corrected for optical degradation, common for solar viewing instruments. The differing long-term trends of various independent solar-irradiance records attest to the challenge at hand. The correction of TSIS SIM for optical degradation is based on piecewise linear fits that bring the three instrument channels into agreement. It is fundamentally different to the correction applied to the TSIS SIM predecessor on SORCE. The correction facilitates reproducibility, uncertainty estimation and is measurement-based. Corrected, integrated TSIS SIM SSI agrees with independent observations of total solar irradiance to within 45 ppm as well as various solar-irradiance models. TSIS SIM SSI is available at: http://lasp.colorado.edu/lisird/ .
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Accurate, long-term solar spectral irradiance (SSI) measurements are vital for interpreting how solar variability impacts Earth’s climate and for validating climate model sensitivities to spectrally varying solar forcing. The Compact... more
Accurate, long-term solar spectral irradiance (SSI) measurements are vital for interpreting how solar variability impacts Earth’s climate and for validating climate model sensitivities to spectrally varying solar forcing. The Compact Spectral Irradiance Monitor (CSIM) 6U CubeSat successfully launched on Dec. 3rd, 2018 as part of the SpaceX SSO-A: SmallSat Express Mission ultimately achieving a sun-synchronous 575 km orbit. CSIM brings new, emerging technology advancements to maturation by demonstrating the unique capabilities of a complete SSI mission with inherent low mass and compact design. The instrument is a compact, two-channel prism spectral radiometer incorporating Si, InGaAs, and extended InGaAs focal plane photodiodes to record the solar spectrum daily across a continuous wavelength region spanning 200 – 2800 nm (>97% of the total solar irradiance). A new, novel electrical substitution radiometer (ESR) using vertically aligned carbon-nanotube (VACNT) bolometers serves as an absolute detector for periodic on-orbit spectral calibration corrections. Pre-launch component level performance characterizations and final instrument end-to-end absolute calibration achieved low combined standard uncertainty (uc<0.5%) in irradiance. These calibrations were performed in the LASP Spectral Radiometer Facility (SRF), a comprehensive spectral irradiance calibration facility utilizing a tunable laser system tied to an SI-traceable cryogenic radiometer. On-orbit, optical degradation corrections to better than 0.05% / year uncertainty are achieved by comparing periodic, simultaneous solar measurements of the two CSIM channels operating with significantly different solar exposure duty cycles. Operational overlap of CSIM with existing SSI measurements validate concepts for maintaining critical long-term solar data records.
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A technology revolution in Earth observation sensor design is occurring. This revolution in part is associated with the emergence of CubeSat platforms that have forced a de facto standardization on the volume and power into which sensors... more
A technology revolution in Earth observation sensor design is occurring. This revolution in part is associated with the emergence of CubeSat platforms that have forced a de facto standardization on the volume and power into which sensors have to fit. The extent that small sensors can indeed provide similar or replacement capabilities compared to larger and more expensive counterparts has barely been demonstrated and any loss of capability of smaller systems weighed against the gains in costs and new potential capabilities offered by implementing them with a more distributed observing strategy also has not yet been embraced. This paper provides four examples of observations made with prototype miniaturized observing systems, including from CubeSats, that offer a glimpse of this emerging sensor revolution and a hint at future observing system design.
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The current implementation for continuous, long-term solar spectral irradiance (SSI) monitoring is the Total and Spectral Solar Irradiance Sensor (TSIS-1) Spectral Irradiance Monitor (SIM) that began operations from the International... more
The current implementation for continuous, long-term solar spectral irradiance (SSI) monitoring is the Total and Spectral Solar Irradiance Sensor (TSIS-1) Spectral Irradiance Monitor (SIM) that began operations from the International Space Station (ISS) in March 2018 and nominally provides an SSI spectrum every 12 h. Advances in both instrument design and spectral irradiance calibration techniques have resulted in the TSIS-1 SIM achieving higher absolute accuracy than its predecessor instrument in the wavelength range (200–2400 nm). A comprehensive detector-based Spectral Radiometer Facility (SRF) was developed in collaboration with the US National Institute for Standards and Technology (NIST) to ensure the ties to spectral SI standards in power and irradiance. Traceability is achieved via direct laser calibration of a focal plane electrical substitution radiometer (ESR) against a cryogenic radiometer in power and also irradiance responsivity via calibrated apertures. The SIM accura...
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The structure of hurricanes from the surface up to 200 mb (12 km) has been extensively studied. However, because of operational limitations of aircraft, very little in-situ information has been obtained within the hurricane environment in... more
The structure of hurricanes from the surface up to 200 mb (12 km) has been extensively studied. However, because of operational limitations of aircraft, very little in-situ information has been obtained within the hurricane environment in the upper troposphere-lower stratosphere (UT/LS). During the ACCENT experiment the WB-57 overflew Hurricane Floyd as it made landfall near the Georgia-South Carolina coastal boarder.
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The direct near ultraviolet absorption spectrum of the A A←X B transition of jet‐cooled chlorine dioxide. [The Journal of Chemical Physics 94, 153 (1991)]. Erik C. Richard, Veronica Vaida. Abstract. The direct absorption spectrum ...
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ABSTRACT The Magnesium II index has been continuously measured by a variety of instruments since 1978. It is a widely used proxy for solar activity, particularly for ultraviolet variability which is critical for the chemistry and dynamics... more
ABSTRACT The Magnesium II index has been continuously measured by a variety of instruments since 1978. It is a widely used proxy for solar activity, particularly for ultraviolet variability which is critical for the chemistry and dynamics of the upper atmosphere. Combining the measurements from instruments with different spectral resolution, observing cadence, and calibrations is not a trivial task. We will present the most recent composite of this critical proxy for solar activity extending thirty five years into the past. We will also describe the upcoming instruments that will continue this record into the future.
The direct near ultraviolet absorption spectrum of the A A←X B transition of jet‐cooled chlorine dioxide. [The Journal of Chemical Physics 94, 153 (1991)]. Erik C. Richard, Veronica Vaida. Abstract. The direct absorption spectrum ...
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The Particle Analysis by Laser Mass Spectrometer (PALMS) instrument measured the composition of individual atmospheric particles while intercepting a forest fire plume over Utah during the Intercontinental Transport and Chemical... more
The Particle Analysis by Laser Mass Spectrometer (PALMS) instrument measured the composition of individual atmospheric particles while intercepting a forest fire plume over Utah during the Intercontinental Transport and Chemical Transformation (ITCT) mission. Large increases in carbon monoxide (CO) and acetonitrile (a known biomass burning product) confirm the plume. The positive spectra obtained during the Utah plume contain large amounts of carbon with varying amounts of potassium in addition to small amounts of organics and particulate NO. In addition to this known plume, a large enhancement in CO accompanied by high aerosol loading, was observed at altitudes greater than 14 km on July 9, 2002 during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE) mission (Key West, FL, July 2002). To determine the origin of this plume, we compare the single particle data to the Utah plume and to those measured over urban areas in order to distinguish between particles measured in high CO regions from pollution versus biomass burning events. The mass spectra show that this stratospheric CO plume was from a biomass burning event. In addition to the PALMS data, back trajectories and other supporting data will be presented.
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