Calibration and testing of wide‐field UV instruments

Frey, H. U.; Mende, S. B.; Loicq, Jérôme; Habraken, Serge

doi:10.1002/2016ja022700

Cited by 3 publications

(6 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The absolute calibration and its corrections for the sensitivity decrease are difficult problems for satellite instruments performing measurements in the UV range (see, e.g., Quémerais et al 2013or Frey et al 2017. As discussed recently by Baliukin et al (2019) and Koutroumpa et al (2019), the SOHO/SWAN instrument showed a significant sensitivity degradation from 2008 to 2014, which can be…”

Section: Solar Far-ultraviolet/extreme-ultraviolet Anisotropymentioning

confidence: 97%

Effects of Heliolatitudinal Anisotropy of Solar Far-ultraviolet/Extreme-ultraviolet Emissions on Lyα Helioglow

Strumik,

Bzowski,

Kubiak

2024

ApJ

View full text Add to dashboard Cite

We present a study of the influence of solar UV anisotropy on the heliospheric backscatter helioglow generated by resonant scattering of solar Lyα photons on interstellar hydrogen atoms around the Sun. Simulations based on the WawHelioGlow model suggest that the response of the helioglow pole-to-ecliptic ratio to the anisotropy is linear, but 15% of the anisotropy (polar darkening) generates 30%–40% change in the ratio in the solar minimum and 15%–20% in the solar maximum. We attribute this difference to an interplay between the solar UV anisotropy and the latitudinal structure of the solar wind in solar minima. The solar UV anisotropy also increases the helioglow intensity from the downwind direction by 5%–10%, due to the influence of the anisotropy on the ionization losses and trajectories of atoms passing by the Sun in polar regions. Consequently, midlatitude regions (in the heliographic and ecliptic coordinates) are least affected by the UV anisotropy. By comparison of the simulation results with observations of the Solar and Heliospheric Observatory/SWAN satellite instrument, we derive the day-by-day time evolution of the solar Lyα anisotropy for the north and south poles over two solar cycles from 1996 to 2022. The inferred anisotropy is ∼5%–10% in solar minima and ∼15%–25% in solar maxima, the northern anisotropy being stronger than the southern one. Our study suggests that in solar minima a highly structured solar wind is associated with relatively small solar UV anisotropy, while in solar maxima the solar wind is more isotropic but a substantial solar UV anisotropy appears.

show abstract

Section: Solar Far-ultraviolet/extreme-ultraviolet Anisotropymentioning

confidence: 97%

Effects of Heliolatitudinal Anisotropy of Solar Far-ultraviolet/Extreme-ultraviolet Emissions on Lyα Helioglow

Strumik,

Bzowski,

Kubiak

2024

ApJ

View full text Add to dashboard Cite

show abstract

“…Before integration of the FUV instrument into the ICON satellite, a dedicated calibration campaign was performed (Frey et al. 2017 ) which determined not only the geometric imaging properties of the system but also the passbands, field of view, out of band contributions from scattering, and the overall quantitative sensitivity of the system (Mende et al. 2017 ).…”

Section: Altitude Profile Data Collectionmentioning

confidence: 99%

“…One of the most important properties of the instrument is its passband and its response to photons of different wavelengths (Frey et al. 2017 ). The careful characterization of the pass band allows then for an on-orbit confirmation or improvement of the calibration accuracy by using regular observations of bright early type-B UV stars (Frey et al.…”

Section: Radiometric Calibration: Theorymentioning

confidence: 99%

“…6 show the temperatures of key electronics components of the detector system during the star observations, namely the CCD, digital board, and high voltage power supplies (Frey et al. 2017 ). There are no indications that these temperatures have an impact on the relative response of the detector systems for as long as they stay within the operating range of .…”

Section: Conversion Of Detector Counts To Radiance and Long-term Stab...mentioning

confidence: 99%

“…Around the subsolar point the daytime thermosphere is sufficiently homogeneous and evenly illuminated by the solar EUV that the observed scene can be considered a “flat” surface without structure (Frey et al. 2017 ). Such observations allow the determination of the flat field response of the instrument.…”

Section: Flat Field Determination and Correctionmentioning

confidence: 99%

See 2 more Smart Citations

In Flight Performance of the Far Ultraviolet Instrument (FUV) on ICON

et al. 2023

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Influence of Heliolatitudinal Anisotropy of Solar FUV/EUV Emissions on Lyα Helioglow: SOHO/SWAN Observations and WawHelioGlow Modeling

Strumik

Bzowski

Kubiak

2021

ApJL

View full text Add to dashboard Cite

Observations of the Sun’s surface suggest a nonuniform radiated flux as related to the presence of bright active regions and darker coronal holes. The variations of the FUV/EUV source radiation can be expected to affect the Lyα backscatter glow measured by spaceborne instruments. In particular, inferring the heliolatitudinal structure of the solar wind from helioglow variations in the sky can be quite challenging if the heliolatitudinal structure of the solar FUV/EUV radiation is not properly included in the modeling of the heliospheric glow. We present results of analysis of the heliolatitudinal structure of the solar Lyα radiation as inferred from comparison of SOHO/SWAN satellite observations of the helioglow intensity with modeling results obtained from the recently developed WawHelioGlow model. We find that in addition to time-dependent heliolatitudinal anisotropy of the solar wind, time-dependent heliolatitudinal variations of the intensity of the solar Lyα and photoionizing emissions also must be taken into account to reproduce the observed helioglow modulation in the sky. We present a particular latitudinal and temporal dependence of the solar Lyα flux obtained as a result of our analysis. We also analyze differences between polar-equatorial anisotropies close to the solar surface and seen by an observer located far from the Sun. We discuss the implications of these findings for the interpretation of heliospheric-glow observations.

show abstract

Calibration and testing of wide‐field UV instruments

Cited by 3 publications

References 33 publications

Effects of Heliolatitudinal Anisotropy of Solar Far-ultraviolet/Extreme-ultraviolet Emissions on Lyα Helioglow

Effects of Heliolatitudinal Anisotropy of Solar Far-ultraviolet/Extreme-ultraviolet Emissions on Lyα Helioglow

In Flight Performance of the Far Ultraviolet Instrument (FUV) on ICON

Influence of Heliolatitudinal Anisotropy of Solar FUV/EUV Emissions on Lyα Helioglow: SOHO/SWAN Observations and WawHelioGlow Modeling

Contact Info

Product

Resources

About