Akatsuki Venus Climate Orbiter |
Akatsuki Venus Climate Orbiter |
Dec 8 2017, 06:24 AM
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#691
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
JAXA has released an image of Venus showing also the Earth and the moon: Venus image with the Earth and also the Moon!
but what is more interesting are the links to archived and calibrated Akatsuki images: UV1 IR1 IR2 LIR |
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Dec 8 2017, 07:57 PM
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#692
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Augh, the site is timing out for me. If I can get my hands on these data I'll rehost it on our Amazon S3 server. I'll keep trying.
-------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Dec 8 2017, 08:19 PM
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#693
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
it worked this morning (European time) but now it's timing out here too
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Dec 11 2017, 04:22 PM
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#694
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
It's working for me now, for what it's worth.
Maybe there was a traffic spike when it was first published. I love this data, and it is tantalizing, because I took two Venus images in UV in December 2016. At that point, Earth had an almost opposite perspective but I can see a match between the larger features in these images and one that I took. I (and other amateurs) took many UV images of Venus from the same perspective as there images in mid-2017. I can't wait to see Akatsuki's images from that time. In particular, there was an interesting phenomenon regarding which the British Astronomical Association sent out an alert in late July 2017 for more observers: Venus had two dark bands in UV, making it look almost like Jupiter. I got one picture of it before my weather hit a bad streak of morning fog. Akatsuki was certainly capable of revealing this in more detail. |
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Dec 22 2017, 10:49 AM
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#695
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Senior Member Group: Members Posts: 1619 Joined: 12-February 06 From: Bergerac - FR Member No.: 678 |
I did some processing by myself after a dive into the RAW imagery of the spacecraft, concerning IR2 and UV1 imagers.
Here is some results I would like to share IR2 in false colors : UV1 in false colors : A little bit more here. -------------------- |
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Dec 23 2017, 04:54 AM
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#696
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Member Group: Members Posts: 315 Joined: 1-October 06 Member No.: 1206 |
Wow! Awesome. Thanks Ant....
P |
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Dec 23 2017, 06:34 PM
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#697
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IMG to PNG GOD Group: Moderator Posts: 2250 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
This is clearly a very interesting data set. These are some of the best images of Venus I've ever seen.
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Jan 2 2018, 03:42 AM
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#698
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Thanks, Paolo
I have translated this article as follows for those who do not go into the walls. P 29 August 2017 Hitherto unkown jet stream found in the Venusian atmosphere Outline Akatsuki's onboard instruments can make observations through layers of thick clouds in the atmosphere of Venus. We examined Akatsuki data in order to find the wind velocity and found that some time during 2016 the wind flow in the lower to mid cloud layers (altitude of 45 to 60 km) formed a jet stream like structure (note: 1) with an axis near the equatorial region. We now call this "equatorial jet". Up until then it was thought that the wind velocity at these altitudes have high horizontal uniformity (note: 2) with little temporal variation, but we now know that there are signigicant variations beyond our previous expectation. The behaviour of Venusian atmosphere is such that the wind velocity from the ground up to cloud top level (70km altitude) increases rapidly, exceeding the velocity of self-rotation, and it is called "super rotation". We do not yet understand its mechanism. We hope that this newly discovered equatorial jet formation and its formation theory will help understand the mechanism of super rotation by numerial simulation. Main text Venus is covered by thick clouds between 45 to 70 km altitudes and the visual appearance of Venus is due to the reflection of Sun light by these clouds. Venus is close to the earth in size and its rotational orbit around the sun is also similar to the earth rotation. However, similarity ends there. Almost all of Venusian atmosphere rotates far faster than its own self-rotational speed. For instance, the rotational period of Venus is 243 days and it is relatively slow, but at an altitude of about 70km the atmosphere is rotating 60 times as fast as its self rotational speed. It is called "super rotation" and it is hoped that Akatsuki's data will help understand more about this super rotation. It is not possible to see through these clouds with visible light, but a limited range of IR can see through them. Akatsuki's IR2 camera can observe the silhouette when the infrared light due to thermal radiation of the lower clouds goes through the clouds. In particular, it enables us to visualise the thick mid to lower layers (45 to 60 km range) of cloud formation. (figures: 1 and 2) Obervations similar to Akatsuki IR2 were conducted by the European Venus Express (2006-2014) and others. However, satellite orbit limitation and visibility restrictions meant limited observations of the low latitude region. Consequently, it has been thought that the wind velocity in this range of altitude is horizontally uniform with little temporal variation. In our research we extensively used the highly reliable cloud chasing technique developped by the team led by Prof. Horinouchi. It enables us to examine closely the horizontal spread of atmospheric flow by cloud movements. (note: 3) Fig. 1: Night side observation (image only) Image down load:[JPG: 3.1MB: (3840x2160px)] [JPG: 1.1MB: (1920x1080px)] Fig. 2: False colour image of night side cloud pattern by IR2 Fig. 2a: 図2a:False colour image of night side cloud pattern by IR2 Darker (blacker) areas have thicker layers of clouds (because there are more cloud forming particles shutting out the IR radiation coming from lower regions of the atmosphere). White area to the left is the day side. © PLANET-C Project Team IR2 camera false colour images were rendered into an animation. Images were obtained during 11th to 12th of July 2016. Fig. 2b: IR2 camera false colour images were rendered into an animation. Images were obtained during 11th to 12th of July 2016. © PLANET-C Project Team While trying to find wind velocities from the IR2 images we discovered, from observatios during July 2016, the existence of equatorial jet. (Fig. 3) This equatorial jet continued to exist at least for 2 months after this point. Prior to June Akatsuki's orbit meant very limited observation of the night side, but we know that the wind velocity in the low lattitude region was a little smaller and there was not jet like structure. The discovery of the horizontal structure of wind velocity that the wind velocity becomes exceptionally faster in the low lattitude region is thought to be significant, because there has been no such example even in the regions of high altitude including cloud top level by a lot more of earlier researches, let alone the research in the less observed middle to low altitude layers. Fig. 3: Example of east-west winds from our research This example is based on the data from 11th to 12th July 2016. The velocity is the average over east-west 3000km region at each latitude. Unit is m/s and N is northern hemisphere and horizontal bars are estimated error bars. At this time an equatorial jet stream with an axis at around 5 degrees north is seen. Since equatorial jets extend east-west this fig. can be thoght of its north-south cross section. For your informaion, the lattitude of the axis shifted slowly during the observation period. The curve in the figure with an annotation such as "5 days" indicates how many earth days are needed for that particular wind velocity to make one complete east-west travel around Venus. © PLANET-C Project Team The reason for the equatorial jet stream formation is unkown, but we believe that there are only a few mechanisms which can explain this phenomenon. Since these limited candidates are also related to super rotation it is expected that further research will lead to theoretical understanding of not only the localised jets but also super rotation itself. We also note the discovery of huge arc structure made by Akatsuki's middle IR camera on the cloud top level. Nobody had expected it. We now know that the properties of these huge arcs can provide information on the near ground level state of Venusian atmosphere, which is difficult to achieve with other means. We will continue with data analysis and and apply the result into numerical simulation for understanding of super rotation. Appendices: Note 1: Jet (Jet stream) Flow region of fast wind which looks like a band. Usually, the fastest (jet axis) is surrounded by less fast wind streams. Note. 2: Horizontal uniformity As stated in Note.1 jets have fatser and less fast portions. Consequently, jets are not horizontally uniform. Fig.3: Recently developped very reliable cloud chasing method Previous methods used 2 subsequent images, but this new method used a large number of temporal images. Further improvements are being made. |
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Jan 7 2018, 12:03 AM
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#699
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Member Group: Members Posts: 401 Joined: 5-January 07 From: Manchester England Member No.: 1563 |
I've been away from this thread for far too long. Thank you for the translations Pandaneko, and for the images Ant103!
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Jan 7 2018, 12:38 AM
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#700
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Senior Member Group: Members Posts: 1637 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
One fine point about the main text. I think the visual appearance of Venus can be considered to be influenced both by clouds and the clear atmosphere. If the clouds have an optical depth of about 30 and the clear air of ~15, then both would be able to scatter light back out to space. It's true most of the light we see (about 75%) is scattered back by clouds. However it's interesting to note that if Venus had just the gas and no clouds it would still be just about as bright. Contributing to this is the fact that clear air scatters light more evenly forwards and backwards, whereby clouds do more forward scattering.
-------------------- Steve [ my home page and planetary maps page ]
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Jan 7 2018, 12:57 AM
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#701
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Senior Member Group: Members Posts: 1637 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
JAXA has released an image of Venus showing also the Earth and the moon: Venus image with the Earth and also the Moon! Interesting with the shortwave IR is that we can see the bright daylit side by reflected sunlight, and some emitted light on the nightside (right). -------------------- Steve [ my home page and planetary maps page ]
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Jan 9 2018, 04:39 PM
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#702
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Interesting with the shortwave IR is that we can see the bright daylit side by reflected sunlight, and some emitted light on the nightside. I aspire, later this year, to become part of the small group of amateurs to make this observation from Earth. Christophe Pellier first did this in 2004; it's the glare from the dayside that makes this challenging. From Earth, there is the additional challenge that such an observation entails that the Sun is close to Venus in any such situation, making the day sky an additional source of noise (though minimized in IR, if sky conditions are good). That's no issue for Akatsuki. It's an interesting issue for IR imagery at ~1-5 microns of Venus and, for that matter, Io, that reflectance/absorption and emission all play a part. For Io's volcanoes, the thermal signal is much stronger at shorter wavelengths, but the reflectance signal is still stronger yet, so effective thermal imagery of Io (the dayside, which is all we see from Earth) has to be done at longer IR where the signal is weaker but the competition with reflectance is weaker still. With Venus' nightside, reflectance does not occur except in that the sunlit crescent can offer noise. At somewhat longer (≥2 microns) wavelengths, the clouds block the radiation coming up from the surface, so we end up measuring cloud thickness as backlit by the surface glow, and ~1 micron, we see the surface itself. As far as I know, there's no groundbreaking science to be done in imaging the surface at regional-scale resolution, but it certainly is a neat accomplishment to do so from Earth. The clouds, meanwhile, offer a lot of science opportunities. However, I don't know of any amateurs with gear for 2 micron imaging. |
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Jan 9 2018, 05:47 PM
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#703
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Senior Member Group: Members Posts: 1619 Joined: 12-February 06 From: Bergerac - FR Member No.: 678 |
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Jan 10 2018, 12:03 AM
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#704
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Superb, Ant! Some of the best Venus images that exist. It really brings out how the equatorial regions look more chaotic on this scale than do the higher latitudes.
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Jan 15 2018, 04:52 AM
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#705
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Member Group: Members Posts: 306 Joined: 4-October 14 Member No.: 7273 |
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