Akatsuki Venus Climate Orbiter |
Akatsuki Venus Climate Orbiter |
May 4 2016, 05:10 AM
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#631
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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 |
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May 4 2016, 05:33 AM
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#632
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
I can't say for certain that this is the case, but the most obvious reason to me would be the approach velocity and how much Delta-v was needed to reach orbit. Akatsuki approaching Venus direct from Earth required a much bigger VOI burn than the lower-velocity approach late last year. Thank you for this. Thank you. P |
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May 4 2016, 05:48 PM
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#633
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
No spacecraft has ever entered a close-in circular orbit around another planet without aerobraking. Orbits like that have only been achieved at Venus (Magellan being the only case) and Mars (several cases, but much less planetary mass).
An elliptical orbit with a low periapsis is pretty good for many scientific purposes. Akatsuki, like Venus Express, Mars Express, and all pre-Nineties Mars/Venus orbiters are/were able to get periodic close-ups along with regular global monitoring. Given that Venus doesn't have seasons, it seems like a pretty good option to have a Venus atmosphere observer in an orbit like Akatsuki's, to collect both close-up and global monitoring, although an orbit like that would have drastically compromised the goals of surface-mapping missions like Magellan or Mars Reconnaissance Orbiter. |
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May 4 2016, 10:39 PM
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#634
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-31
Example 5: (title): Clarifying atmospheric motions by cloud chasing (UVI+IR1+IR1 (must be 2?, P)+ LIR) (just below mini image of Venus, above earlier graphic): Obtained wind velocity distrbution by analysing 3 images (at 365mm and every 2 hours) taken by UVI (just above wind vector diagram): Wind velocity distribution in equator region (S Latitude 25 ° - N Latitude 25 °) (immediately below wind vector diagram): Atmospere flows by super rotation, but motion's spatial pattern changes constantly. By analysing, at a number of different altitudes, we aim to find out what kind of fluid waves exist and how they are related to super rotation, and how they are responsible for vertical circulation of Venusian atmosphere. P |
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May 4 2016, 10:46 PM
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#635
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
An elliptical orbit with a low periapsis is pretty good for many scientific purposes. Thank you for this. "periapsis" and a counterpart to it are the words I should have been using in some places of my translation. Instead, I always use "nearest Sun"etc etc because I can never distinguish them and remember which is which. It took me 15 to 20 years to learn the difference between latitude and longtitude, after all. So, my excuses... P |
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May 4 2016, 10:52 PM
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#636
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page number of the last translated page shoud be 32, instead of 31.
Page-33 Observation results (summary) Same as page-10 (After this page there are some more on instruments, mainly. I think I will do them, if not all, as students may not be that familiar with them) P |
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May 4 2016, 11:08 PM
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#637
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-36
IR1: 1mm camera By using 1 mm wave length which enables the camera to see below Venusian clouds down to ground level we aim to: cloud movements in lower atmosphere, water vapour distribution, mineral composition of ground surface, existence of active volcanoes etc. 1mm camera IR1 Mass: approx. 6.7kg ※ Field of view: 12° Detector: Si-CSD/CCD (1024 pixels×1024 pixels) Observed wave lengths (targets) 1.01 mm (night: ground surface, clouds) 0.97 mm (night: water vapour) 0.90 mm (night: ground surface, clouds) 0.90 mm (day time: clouds) ※ including circuits (approx. 3.9 kg) shared with IR2 P |
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May 5 2016, 02:05 AM
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#638
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-37
IR2: 2mm camera 1. By using wave lengths near 2mm which alow us to penetrate Venusian clouds we aim to obtain basic data for lower atmospheric circulation and cloud physics via cloud density, cloud nucleus size, and carbon monoxide distribution. 2. By observing, before reaching Venus, zodiacal lights we aim to clarify the behaviour of interplanetary dusts. 2mm camera: IR2 Mass: approx. 18kg ※ Field of view: 12° Detector: PtSi-CSD/CCD (1024×1024) Wave length (observation target) 1.735mm (night: clouds and nucleus size distribution) 2.26 mm (night: clouds and nucleus size distribution) 2.32 mm (night: carbon monoxide) 2.02 mm (day time: cloud top altitude) 1.65 mm (Zodiacal lights) ※ including cryos and circuits commmon to IR1 (approx. 3.9kg) P |
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May 5 2016, 05:29 AM
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#639
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-38
LIR: Mid infra red camera This camera is meant to capture cloud temperatures using 10mm wave length, thereby clarifying wave motions at top cloud layers, convection activities, and wind velocity distribution at the night side cloud top altitude. Mid infra red camera: LIR Mass: approx. 3.3kg Field of view: 12.4×16.4° Detector: unclooled borometer (248×328) Observed wavelength (target): 10 mm (Day time/night time: cloud top temp.) P |
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May 5 2016, 05:45 AM
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#640
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-39
UVI: Ultra violet imager By imaging the distribution of sulfur dioxide responsible for cloud formation and unkown chemical substance which absorbs ultra violet light and their variations we aim to obtain wind velocity distribution at cloud top levels. Ultra violet imager: UVI Mass: approx. 4.1kg Field of view: 12° Detector: Si-CCD (1024×1024) Observed wavelength (target): 283 nm: (daytime: sulfur dioxide at cloud top level) 365 nm: (night time: unknown absorbing substance) P |
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May 5 2016, 06:06 AM
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#641
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-40
LAC: Lightening and atmospheric light camera 1. By imaging the pale light emitted by oxygen molecules in the upper layer of Venusian atmosphere at around 100km we aim to visualise the variations in daytime/nightitme circulation and atmospheric wave motion. 2. By high speed exposure of 30,000 times/second (temporal resolution of 32msec) we aim to put a final end end to ongoing argument about the existence or otherwise of Venusian lightenings. Lightening/atmospheric light camera: LAC Mass: approx. 2.3kg Field of view: 16° Detector: 8×8 APD matrix array Observed wavelength (target): 777.4nm: (night: lightenings) 480-650nm: (night: oxygen molecules atmospheric light) 557.7 nm: (night: oxygen atoms atmospheric light) 545 nm (for comparison purposes) P |
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May 5 2016, 07:03 AM
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#642
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-41
USO: Ultra stable oscillator This is used for radio wave occultation. We can gain information about vertically propagating wave motion and thermal structure of Venusian atmosphere and its temperature variation with altitude by monitoring changes in strength and frequency of the radio waves reaching earth through Venusian atmosphere. Ultra stable oscillator: USO Mass: approx. 2kg Wavelength : USO frequency: 38MHz Transmission frequency: 8.4GHz Target: Temp., sulfuric acid vapour, electron density [graphic image: radio wave occultation] USO is fixed inside the satellite P |
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May 5 2016, 07:59 AM
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#643
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
In the immediate wake of this year's report I am now on to JAXA's November 2015 report.
There will be some overlapps with this year's and they will be omitted. Page-1 Circular orbit insertion (plan) and observation scheme of Akatsuki 9 November 2015 JAXA ISAS project team for Akatsuki Page-2 Outline ・ Re-insertion of Akatsuki will be attempted on 7 December 2015 (JST). ・ We tried to insert Akatsuki into a circular orbit around Venus on December 2010. That attemt failed due to mul-functioning of the main engine. Akatsuki is currently flying in an orbit around the sun. ・ The renewed attmpt this time will insert Akatsuki into an elliptical orbit with a higher furthest point from Venus using 4 attitude control engines without relying on the failed main engine. ・ Mission objective is to continously observe atmospheric motion of Venus and ellucidate on the mechanisms of its atmospheric circulation. P |
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May 5 2016, 08:26 AM
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#644
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-3
Mission Objectives 1. Earth and Venus are similar in size and solar radiation inputs are also similar. 2. However, climates are very different. For instance, the high velocity wind (approx. 100m/sec) at the upper layer of Venusian atmosphere, called "Super rotation", is noticeable. It is a high velocity wind which goes around Venus in 4 earth days. Venus has a rotation period of approx. 243 days. 3. Why these differences? We want to know. (On the diagram left globe is earth. Right globe is Venus) (around earth peripheral): Character set at 10:00 is Hudley circulation, at 11:00 Ferrell circulation, and at 11:50 Polar circulation. Character set in upper hemisphere of earth is Westerly, and that near the equator is the trade wind. Character set in the middle of Venus is Super Circulation, and at the bottom is the Meridian plane circulation. P |
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May 5 2016, 08:28 AM
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#645
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-4
Mission objective (above two graphical images) By examining, 3-dimentionally, the motion of thick Venus atmosphere we wish to clarify the mechanisms controlling the climate on Venus and compare them with those on the earth. (graphical images here) (Satellite graphic not translated) (There are 9 lines on the lefthand side of this graphics page, all pointing to the image in the middle. Numbering corresponds to those lines from top to bottom) 1. Temperature/sulfuric acid vapour altitude (radio wave occultation) 2. Atmospheric lights (Lightening and atmospheric camera) 3. Sulfur dioxide (Ultra violet image) 4. Cloud altitude (Mid infra red camera) 5. Lower altitude clouds (1&2 micrometer camera) 6. Wind velocity spectrum (as judged by cloud movement) 7. Carbon monoxide (2 micrometer camera) 8. Lightening discharge (Ligthening and atmospheric light camera) 9. Water vapour (1 micrometer camera) (and at the very bottom, from left to right) Ground surface material/active volcanos (1 micrometer camera) Ground surface (Character sets on the right hand side (Top to bottom)) 3-D observation of thick atmosphere 1. Stratosphere 2. Sulfuric acid clouds 3. Troposphere (below these two graphical images) ・ Why does the super rotation occur? ・ How does the Meridian rotation affect Venetian climate? ・ How are clouds produced that cover the entire surface of Venus? ・ Can lightenings occur in the atmosphere in which there are no ice crystals? ・ Are there active volcanoes? P |
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