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. Funded by CASIS (Center for the Advancement of Science in Space) which manages the ISS US National Laboratory for NASA, this project has amassed a large collection of storm images during the last four years. While a number of processed images have been released to the public over the years through various online and print outlets, the CyMISS team at Visidyne (the prime contractor of the project) wanted to share some of the best images we have been creating.
In the latest phase of CyMISS, our team has begun exploring improvements we can make to our observing techniques as well as new potential applications. One of our new investigations involves observing storms at night using moonlight as the source of illumination. For our first nighttime photography session, the crew of the ISS took a sequence of photographs of the remains of Subtropical Storm Alberto as it passed over the southeastern US in the early morning hours of May 30, 2018 (see “CyMISS Image of the Month: Alberto by Moonlight from the ISS”). For our second successful nighttime observation session, the crew of the ISS acquired a sequence of photographs of Post-Tropical Cyclone Gilma in the central Pacific Ocean on July 31.
This B&W mosaic shows Post-Tropical Cyclone Gilma as viewed by moonlight from the ISS on July 31, 2018. It was created by remapping the original 240 photographs taken by the crew of the ISS to approximate an overhead view before stitching them together and covers an area of 1,000 by 500 kilometers. Click on the image to view a high-resolution version with a scale of 500 meters/pixel. (A.J. LePage/Visidyne/JSC-NASA)
The four-minute photography session of Gilma started at 11:18:48 GMT on July 31 with a nominal aim point of 15.5°N, 146.8° W when the remains of this storm were well southeast of Hawaii. Gilma had already reached its peak strength as a minimal tropical storm with maximum winds of 64 kph (40 mph) four days earlier and was being viewed by moonlight about 86 hours past full Moon yielding an illumination level of about 10-6 that of the Sun. A mosaic of those images providing a synoptic view of Gilma is shown above. Post-Tropical Cyclone Gilma is the irregularly shaped mass of bright clouds near the center of this image. The graininess in these images is the result of enhanced noise levels caused by the low ambient illumination requiring an ISO setting of 51,200 with the 1/30th of a second exposure time chosen to minimize smearing caused by the seven kilometer per second motion of the ISS.
Even though Gilma was a comparatively weak storm when it was observed for CyMISS from the ISS, it still packed quite a punch. An inspection of the mosaic showed a bright rectangular shape in the lower part of Gilma left of the image center. Further investigation showed that this was the result of a powerful lightning strike taking place when the photograph which makes up that part of the mosaic was taken. While numerous lightning strikes were recorded during our nighttime observations of Alberto two months earlier, none proved to be as spectacular as this one. A closeup view of that strike extracted from the image ISS056-E-100802 is August’s CyMISS Image of the Month. The image, shown below, was acquired at 11:20:25 GMT and provides a view that is about 150 kilometers wide. The bright light from this lightning strike overwhelms the illumination provided by moonlight and produces a cloud top aureole that is over 30 kilometers across in addition to providing a spectacular view of the clouds in this weakening, yet still potent, storm.
This is a color closeup of the powerful lightning strike inside the remains of Post-Tropical Storm Gilma over the central Pacific. This image, ISS056-E-100802, was acquired by the crew of the ISS at 11:20:25 GMT on July 31, 2018 and provides a view which is about 150 kilometers wide. Click on the image to see a full resolution version of this image. (A.J. LePage/Visidyne/JSC-NASA)
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 GA-2018-272.
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See earlier articles on the CyMISS program here.