[X] My Assistant

[Bjorn Jonsson]

It is easy to forget that JunoCam isn't the only instrument aboard Juno that can obtain images. The Jovian Infrared Auroral Mapper (JIRAM) instrument can obtain images in two infrared bands. One of these, centered at a wavelength of 4.78 µm, shows thermal radiation emitted from Jupiter. This radiation is caused by heat from Jupiter's warm interior - as a result there is no difference between the dayside and nightside in these images. Therefore they are great for looking at Jupiter's north pole which isn't visible in the JunoCam images because it is currently winter in Jupiter's northern hemisphere.

Here is a tweened time-lapse created from three JIRAM image mosaics obtained over an interval of slightly less than three hours shortly before perijove 4 on February 2, 2017:

 jup_jiram_npole_anim_20170202.mp4 ( 2.11MB ) Number of downloads: 968


Because Juno was approaching Jupiter the image sharpness increases from start to finish.
In case you are unable to play the MP4 file above the time-lapse can also be viewed at Vimeo (the quality is somewhat lower though): https://vimeo.com/263221959

All of the JIRAM images through perijove 6 are available at the Planetary Data System Atmospheres Node and can be converted to PNG files using IMG2PNG. Thousands of images have been obtained by JIRAM.

Usually a spacecraft's highest resolution imaging instrument is a visible light camera but Juno is an exception. JIRAM's resolution is higher than JunoCam's. While JIRAM's images are small compared to the JunoCam images (only 432 pixels in the horizontal direction) it has much narrower field of view than JunoCam (5.9 degrees vs. JunoCam's 58 degrees). Combined, this means that the JIRAM images have about three times higher resolution than the JunoCam images but they also cover a much smaller area.

Here is a mosaic of Jupiter's north polar region from the data that was used to create the animation above:



This shows all nine circumpolar cyclones (CPSs) in their full glory. The mosaic shows the north polar region from directly above and is in orthographic projection. It is centered on the north pole. These images have been processed to show details in the areas that appear very dark in the original images. Comparing JIRAM images to visible light (JunoCam) images reveals that the JIRAM images are somewhat similar to inverted visible light images; features that appear bright at visible wavelength are usually dark in 4.78 µm images and vice versa.

Because JIRAM has obtained a lot of images, often with an interval of only 30 seconds, they can be animated. Below are two animated GIF examples. First an animation of 186 JIRAM images obtained over a period of 1 hour and 35 minutes on August 1, 2016 from a distance of approximately 8 million km:



And another animation that consists of 145 JIRAM images obtained over a period of 1 hour and 16 minutes on August 26, 2016 from a distance of approximately 1.6 million km. Even though it may look as if the spacecraft is traveling south to north this is not the case; it is the direction in which the spacecraft is looking that changes. The Great Red Spot is clearly visible:



In both of the animations the images have been processed to reveal details in areas that appear very dark in the original data. However, I decided not to remove noise or make the animations more 'stable'. Both because it would have been a lot of work but also because I actually prefer these animations without 'cleanup'. They appear more realistic that way. This is a matter of taste but sometimes less is more when it comes to image processing.

[Gerald]

A couple of weeks ago, I stitched some of the JIRAM images, simply using Hugin. But they are flipped. I noticed this too late before PJ12, and after Alberto Adriani's hint:





This has been an early attempt to make JIRAM images like JunoCam images:


This simple way of stitching with Hugin works only for short sequences of images. Larger sets require proper reprojection, and there are 30 seconds between two consecutive images resulting in cloud displacments. Note also, that the JIRAM imager has several dead pixels. When inverting the data and stretching them heavily, you'll notice residual striping artifacts,...

... and as Björn says, PJ12 is awaiting more processing.

JIRAM and JunoCam data appear to be mostly anticorrelated. But near the equator, you can see, that the mesoscale waves are much more distinct at 5 µm than in the visible, and wavelength seem much longer on JIRAM.

Also interesting the number and intesity of Io's volcanos, in the lower part of this tile.

[stevesliva]

Also interesting the number and intesity of Io's volcanos, in the lower part of this tile.

Wow, look at that. Plume at 8 o'clock on the dayside, too.

[volcanopele]

Wow, look at that. Plume at 8 o'clock on the dayside, too.

Okay, starting to work with this dataset. Getting some tentative IDs on the volcanoes seen.

First, that is not a plume (plumes don't show up well at these wavelengths). Looks like hotspot associated with Loki.

Other hotspots visible include Masubi, Shamshu Patera, Kanehekili, Janus Patera, Euboea Fluctus, Heno Patera, (46N, 12W), (26N, 4W), Catha Patera, Uta Patera or Uta Fluctus, Mbali Fluctus (maybe), (11N, 61W), Lei-Zi Fluctus (maybe), and Tawhaki Patera.

Brightest sources are Uta, Kanehekili/Janus, and Masubi.