In the most recent phase of the CyMISS (tropical Cy clone intensity M easurements from the ISS ) project, our team has been exploring improvements we can make to our observing techniques. One of our investigations involves observing storms at night using moonlight as the source of illumination. On February 20, 2019, the Expedition 58 crew of ISS acquired a series of 240 image pairs of Tropical Cyclone Oma with the exposure times alternating between 1/30th and 1/8th of a second. The image sequence spans from 16:58:46 to 17:02:45 GMT when the Moon, which provided the only source of illumination for the storm, was about 25 hours past full. At this time, Tropical Cyclone Oma was located at about 22.1° S, 160.6° E in the South Pacific off the east coast of Australia and was rated as Category 2 storm on the Australian tropical cyclone intensity scale with sustained winds of about 105 kph (65 mph).

A typical image from this sequence with an exposure time of 1/8th of a second is shown below. Apparent in the image is the moonlit eye of the Tropical Cyclone Oma as well as stars above the horizon. Visible above the horizon is the airglow layer at an altitude of about 90 kilometers caused by sodium deposited by meteors which had burned up in Earth’s upper atmosphere. Also visible is sunlight filtering through the atmosphere from the Sun far below the horizon and even hints of zodiacal light in the upper left corner caused by sunlight scattering off interplanetary dust (see “The South Pacific Nighttime Sky as Seen from the ISS“).

March’s Image of the Month is a 3D view of Tropical Cyclone Oma created using images acquired by the crew of the ISS on February 20, 2019. In order to create this anaglyphic 3D image (left eye red, right eye blue), the individual longer-exposure photographs from the original image sequence were remapped to approximate an overhead view before various parts of the frames were stitched together into a synoptic 3D mosaic covering an area of 1,500 by 1,000 kilometers with a stereo angle of about 20°. A high resolution version of this synoptic 3D mosaic with an image scale of 500 meters/pixel can be viewed by clicking on the image below. Note that the cloud bands of this southern hemisphere storm (which clearly stand above the other clouds in this 3D view) display a clockwise rotation – the opposite of its northern hemisphere kin. Just visible in the upper left corner of the image are the city lights of Brisbane, Australia

The goal of the ongoing CyMISS (tropical Cyclone intensity Measurements from the ISS) project is to acquire image sequences of intense tropical cyclones (TCs), such as hurricanes, to support the development of an improved remote sensing method to determine more accurately the strength of these destructive storms using stereoscopy. The CyMISS team at Visidyne would like to thank the crew of the ISS as well as the staff at NASA’s Marshall Space Flight Center and Johnson Space Center for their ongoing efforts. The original images are courtesy of the Earth Science and Remote Sensing Unit at NASA Johnson Space Center. The work presented here is supported in part under CASIS Grant UA-2019-013.

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See earlier articles on the CyMISS program here.