IPB

Welcome Guest ( Log In | Register )

48 Pages V  « < 45 46 47 48 >  
Reply to this topicStart new topic
Akatsuki Venus Climate Orbiter
Paolo
post Dec 8 2017, 06:24 AM
Post #691


Senior Member
****

Group: Members
Posts: 1619
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
Go to the top of the page
 
+Quote Post
elakdawalla
post Dec 8 2017, 07:57 PM
Post #692


Administrator
****

Group: Admin
Posts: 5081
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 blog - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
Go to the top of the page
 
+Quote Post
Paolo
post Dec 8 2017, 08:19 PM
Post #693


Senior Member
****

Group: Members
Posts: 1619
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
Go to the top of the page
 
+Quote Post
JRehling
post Dec 11 2017, 04:22 PM
Post #694


Senior Member
****

Group: Members
Posts: 2055
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.
Go to the top of the page
 
+Quote Post
Ant103
post Dec 22 2017, 10:49 AM
Post #695


Senior Member
****

Group: Members
Posts: 1485
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 smile.gif

IR2 in false colors :


UV1 in false colors :




A little bit more here.


--------------------
Go to the top of the page
 
+Quote Post
antipode
post Dec 23 2017, 04:54 AM
Post #696


Member
***

Group: Members
Posts: 224
Joined: 1-October 06
Member No.: 1206



Wow! Awesome. Thanks Ant....

P
Go to the top of the page
 
+Quote Post
Bjorn Jonsson
post Dec 23 2017, 06:34 PM
Post #697


IMG to PNG GOD
****

Group: Moderator
Posts: 1954
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.
Go to the top of the page
 
+Quote Post
pandaneko
post Jan 2 2018, 03:42 AM
Post #698


Member
***

Group: Members
Posts: 704
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.

Go to the top of the page
 
+Quote Post
marsbug
post Jan 7 2018, 12:03 AM
Post #699


Member
***

Group: Members
Posts: 326
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!


--------------------
Go to the top of the page
 
+Quote Post
scalbers
post Jan 7 2018, 12:38 AM
Post #700


Senior Member
****

Group: Members
Posts: 1300
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.


--------------------
Go to the top of the page
 
+Quote Post
scalbers
post Jan 7 2018, 12:57 AM
Post #701


Senior Member
****

Group: Members
Posts: 1300
Joined: 5-March 05
From: Boulder, CO
Member No.: 184



QUOTE (Paolo @ Dec 8 2017, 06:24 AM) *
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).


--------------------
Go to the top of the page
 
+Quote Post
JRehling
post Jan 9 2018, 04:39 PM
Post #702


Senior Member
****

Group: Members
Posts: 2055
Joined: 20-April 05
Member No.: 321



QUOTE (scalbers @ Jan 6 2018, 05:57 PM) *
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.
Go to the top of the page
 
+Quote Post
Ant103
post Jan 9 2018, 05:47 PM
Post #703


Senior Member
****

Group: Members
Posts: 1485
Joined: 12-February 06
From: Bergerac - FR
Member No.: 678



Some new pictures I made today smile.gif





--------------------
Go to the top of the page
 
+Quote Post
JRehling
post Jan 10 2018, 12:03 AM
Post #704


Senior Member
****

Group: Members
Posts: 2055
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.
Go to the top of the page
 
+Quote Post
jccwrt
post Jan 15 2018, 04:52 AM
Post #705


Member
***

Group: Members
Posts: 207
Joined: 4-October 14
Member No.: 7273



I've attempted to make some pseudo-true color views using the 360nm UV and 0.90 μm IR cameras. I realize these are poor approximations of the actual visible spectrum appearance of Venus, but those are kinda boring anyway! laugh.gif





Go to the top of the page
 
+Quote Post

48 Pages V  « < 45 46 47 48 >
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 18th June 2018 - 01:02 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.