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NASA.gov has an image of the James Webb space telescope's nircam tracking a high speed belt near Jupiter's equator. They measured the speed by looking at wind shears in millibars. How does Webb do that? What instrumentation is used for this purpose? Thanks.

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The team determined how quickly the winds vary with altitude and produce wind shears by comparing the currents detected by Webb at high altitudes to those observed by Hubble at deeper layers

https://www.techexplorist.com/new-feature-discovered-jupiter-atmosphere/75903/

In short:

  • NIRCam obtained images of Jupiter 10 hours apart — one Jupiter day — in four different filters, each uniquely able to detect changes in small features at different altitudes of Jupiter’s atmosphere.
  • The wind speed was calculated by tracking the motion of small features, such as clouds
  • use the timing of the data to see how rapidly storms develop
  • results compared with data from contemporary observations made by other means, ie. HubbleST

enter image description here

https://blogs.nasa.gov/webb/2022/08/22/webbs-jupiter-images-showcase-auroras-hazes/

... images come from the observatory’s Near-Infrared Camera (NIRCam), which has three specialized infrared filters that showcase details of the planet. Since infrared light is invisible to the human eye, the light has been mapped onto the visible spectrum. Generally, the longest wavelengths appear redder and the shortest wavelengths are shown as more blue.

The auroras shine in a filter that is mapped to redder colors, which also highlights light reflected from lower clouds and upper hazes. A different filter, mapped to yellows and greens, shows hazes swirling around the northern and southern poles. A third filter, mapped to blues, showcases light that is reflected from a deeper main cloud.

“The brightness here indicates high altitude – so the Great Red Spot has high-altitude hazes, as does the equatorial region,” said Heidi Hammel, Webb interdisciplinary scientist for solar system observations and vice president for science at AURA. “The numerous bright white ‘spots’ and ‘streaks’ are likely very high-altitude cloud tops of condensed convective storms.” By contrast, dark ribbons north of the equatorial region have little cloud cover.

https://www.nature.com/articles/s41550-023-02099-2

We observed Jupiter’s atmosphere on 27 July 2022 using the Near Infrared Camera (NIRCam) instrument on the James Webb Space Telescope (JWST) as part of the Jupiter System Early Release Science Program no. 1373.

Because Jupiter is a bright target for JWST, we selected filters centred in strong atmospheric methane absorption bands (F164N, F335M, F360M and F405N) and in the strong H2–H2 and H2–He collision-induced absorption band at 2.12 μm (F212N), and obtained full-disk images of the planet.

We repeated our observations after one planetary rotation (about 10 h) to observe the same hemisphere twice and examine temporal changes and dynamics, with the exception of filters F360M and F405N, which were only used once.

Comparison to Hubble:

Ground-based and Hubble Space Telescope (HST) observations of Jupiter at these wavelengths generally result in images with very low contrast in which most fine-scale atmospheric details cannot be resolved.

Wind results

We tracked the motions of atmospheric features observed in the F164N, F212N and F335M images by comparing map-projected images of the planet separated in time by one planetary rotation. We used image correlation software designed for cloud-tracking wind analysis and excluded from the analysis regions covered by large atmospheric systems like the GRS.

enter image description here

Winds analysis

Maps of the planet were compared using the PICV3 software This software performs one- or two-dimensional correlations over two images using boxes whose size can be configured and adapted to the contrast of the region of the image where the analysis is run. Winds were measured over the final composed images except in the F164N images, where image pairs over the same B detector were compared individually producing 16 individual data sets that were later merged into a single zonal wind profile. PICV3 has a graphical user interface that allows selection of specific regions of the images. We avoided regions with large-scale features and examined the equatorial region with long boxes with typical longitudinal sizes of 20° and latitudinal sizes of 1°. The F164N images were analysed using 16 image pairs from the combination of 4 subarrays and 3 dither positions combining the results from the individual zonal wind profiles in a single zonal wind profile in that filter.

PICV stands for Particle Image Correlation Velocimetry

PICV was created by Dr. Ricardo Hueso at UPV/EHU as a software tool to retrieve wind fields in images of planetary objects with atmospheres by analyzing the displacement of common regions found in images separated by a given amount of time.

enter image description here

The NIRCam obtained images of Jupiter 10 hours apart — one Jupiter day — in four different filters, each uniquely able to detect changes in small features at different altitudes of Jupiter’s atmosphere. The wind speed was calculated by tracking the motion of small features, such as clouds — most likely ammonia ice mixed with photochemical haze particles typical of Jupiter's atmosphere.

“We knew the different wavelengths of Webb and Hubble would reveal the three-dimensional structure of storm clouds, but we were also able to use the timing of the data to see how rapidly storms develop,” said UC Berkeley co-author Michael Wong, co-investigator for the Jovian system ERS program.

https://vcresearch.berkeley.edu/news/webb-telescope-discovers-intense-jet-stream-jupiters-atmosphere

enter image description here

Source data: https://www.nature.com/articles/s41550-023-02099-2#MOESM2

https://zenodo.org/records/4312675

enter image description here

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