Read clouds in different wavelengths

Akatsuki carried cameras spanning ultraviolet to longwave infrared. The ultraviolet imager, UVI, measured contrast near the cloud tops at 283 and 365 nanometers. Near-infrared IR1 and IR2 used selected bands to investigate different atmospheric conditions; their targets also depended on whether they viewed the illuminated or dark side. The longwave infrared camera, LIR, measured thermal emission from the cloud tops.

A detector band is not a universal window to a fixed surface. Radiation can be emitted, scattered or absorbed along its path. Before asking what a bright patch means, identify the wavelength, illumination, instrument response and processing. The word infrared alone cannot tell you whether an image emphasizes reflected sunlight, thermal emission or a deeper atmospheric window.

The displayed scientific figure preserves three early post-insertion views from December 2015: IR1 at left, UVI in the middle and LIR at right. They show different contrast. The left panel’s partial framing is present in the published figure; Atlas has retained it. These grayscale panels are not three natural-color photographs, and they cannot by themselves measure how fast a feature moved.

Use the difference as a prompt for investigation, not as a direct conversion between brightness values. The LIR archive identifies its band as 8–12 micrometers and explains its calibration products. A physically meaningful temperature interpretation requires the relevant calibration. Two equally gray pixels from different panels need not represent equal temperatures, equal amounts of cloud or even the same measured quantity.

A shared electronics problem affected IR1 and IR2 in December 2016. JAXA’s March 2017 notice reported that those cameras had paused scientific observations while the other cameras continued. An equipment list describing the spacecraft at launch therefore does not establish that every instrument produced data throughout the mission. A year in an observation’s filename is part of the scientific context.

Consider a comparison between a 2016 IR2 image and a later UVI image. Any difference could involve time, observing band, altitude sensitivity, geometry or processing. It cannot automatically be called a change in the same cloud layer. A stronger study either compares suitable like-for-like measurements or explicitly models the differences between them.