Maybe we need a "Science Experiments" thread. :-)

--Greg

Well, having swept up the sugar in the broom cupboard I'm still trying to find more answers to the questions I posed in post 344 about the asymmetric form of heavy water and water with heavy oxygen. I found another very helpful link, given below, where both are briefly described. HDO seems to have at least three names: hydrogen deuterium oxide, hydrogen protium oxide and semiheavy water. Apparently H and D exchange easily between molecules so the relative abundances of H2O, D2O and HDO are in equilibrium in any given environment with absolute amounts determined by the overall H:D ratio. I think this means that where there is much less D than H there will be much more HDO than D2O. (The link in my 'heavy water isn't blue' post was all abour D2O.)

As to whether the asymmetry of HDO results in spectral properties of significance to planetary science I am still none the wiser.

http://wapedia.mobi/en/Heavy_water

H and D (and T) will exchange among depending on the acidity function (pKa) of the protons. Acidic protons exchange. Water or methanol terminal protons are acidic. So if you start with CH3OH and put it in with a lot of D2O you will end up with CH3OD, D2O, some HDO, very little CH3OH and probably a few molecules of H2O.

(Chemists use deuterated solvents all the time to aquire 1H NMR spectra, the D signal acts is used to "lock" the magnetic field. Exchangeable protons usually disappear and are not visible or diminished in the 1H NMR spectrum. Likewise, the deuterated solvent always shows a residual peak due to some proton exchanging in, that can also be used to reference the 1H NMR spectrum.)


For IR spectra, here is an available reference for the region 8100-7600 cm-1 (1.23-1.32 um): http://staff.ustc.edu.cn/~smhu/publication...203_HDO_300.pdf

Here is a reference (I couldn't get it) for the region 700 nm to 10,000 nm (=10 um) http://adsabs.harvard.edu/abs/1963InfPh...3..211B


Here is also a reference that shows that comets have a different H/D ratio than on Earth. (Thus Earth's water might've been intrinsic.):
http://www.sciencemag.org/cgi/content/abstract/279/5352/842

Thanks for those links! I've printed off the first one and the abstract of the comets one, but like you couldn't get the second one at all - a pity since it covers a wide spectral range highly relevant to the study of planetary atmospheres. Not being a specialist in all this I will continue to look for an 'easier' overview, but I suspect I may be out of luck. I think a rummage through a few good hefty textbooks is what's required, but our college library doesn't run to such.

Whoops! My bad! Here is a link to the 0.7-10 um region article is available with paid-for access.

Bayly et al. Infrared Physics, 1963 3, 211-223. "Absorption spectra of liquid phase H2O, HDO, and D2O from 0.7 um to 10 um."

The article shows the full spectrum for H2O and D2O, with an estimated spectrum for HDO, along with (technical) explanations of the assymmetry of HDO and how it would affect the spectrum.

It also highlights the areas where there are big differences between the absorbances of H2O and HDO.
HDO has a big extinction coefficient at 4 um, while H2O has a big extinction coefficient around 3 um.

(The spectra for H2O and D2O look like the spectra you showed from the article, there are just more details regarding exact shifts, extinction coefficients, and vibrational mode assignments.)

-Mike

Thanks again Mike. That's obviously the one I need to track down when I get the chance. Your summary is most useful (more so than the abstract for my purposes, as you mention that the effects of asymmetry are specifically discussed).

The Science Programme Committee (SPC) of the European Space Agency (ESA) met on 02 October, and approved the mission extensions for Venus Express and Mars Express through the end of 2012. More details, and all the other missions affected, should be reported soon.

Mission Extension News from: http://sci.esa.int/science-e/www/object/in...fobjectid=45685

ESA's Science Programme Committee has approved the extension of mission operations for XMM-Newton, INTEGRAL, Venus Express, Mars Express and Cluster, as well as the ESA support to the operations of HST and SOHO, until 31 December 2012. An additional year of operations has been approved for Planck.

At the 126th meeting of the Science Programme Committee, held 2 October 2009, at ESTEC, the Netherlands, the decision was taken to approve the period of mission operations for seven missions until end 2012. This meeting marked the first application of a new procedure whereby mission extensions for all missions whose approved operations end within the following four years are considered as a whole.

The missions under consideration at this meeting were: XMM-Newton, INTEGRAL, Venus Express, Mars Express and Cluster, and the ESA support to the operations of HST and SOHO. The case for extending the period of operations for these missions is based on the value of the science added as a result of extended operations. The proposal for extension of mission operations for all of these missions, based on recommendations from an SPC Task Group and the Space Science Advisory Committee (SSAC), was accepted by the SPC.

The extensions for mission operations are approved up to 31 December 2012, subject to a mid-term review in 2010. Towards the end of 2010 the SPC will be requested to confirm, subject to the satisfactory performance of the missions, the remaining two years of the extension and to consider further extensions of operations.

The additional year of Planck operations, to follow on from the end of nominal operations in 2010, would facilitate an additional two sky surveys. This extra period of operations is subject to the SSAC confirming that the mission has achieved satisfactory in-orbit performance. Planck, launched in May 2009, has recently commenced routine operations following the successful completion of the in-orbit commissioning and performance verification phases.

The nominal mission operations for Herschel, which was launched with Planck in May 2009, were previously approved until end 2012.

The 6th release of the Venus Monitoring Camera (VMC) data for the extended mission is available on the ESA Planetary Science Archive (PSA) at
http://www.rssd.esa.int/index.php?project=PSA.

You will be able to see products up to orbit 1079, which was 04 April 2009.

Did I miss something but could anyone find me a news source from ESA stating that Venus express did find evidence suggestive of recent and ongoing volcanism??

I was a little puzzled by these statements, too. I think it may be referring to this:

http://www.esa.int/SPECIALS/Venus_Express/SEMUQCLXOWF_0.html

See if that helps. The people involved readily admit that what they have are "hints" of volcanic activity.

There's a chance that our old Fregat upper stage may be trying to come home. The small asteroid 2010 AL 30 zoomed past us yesterday, and it might turn out to be the VEX upper stage.

http://www.scilogs.eu/en/blog/go-for-launc...ounter-tomorrow

New evidence for recent volcanism on Venus

08 Apr 2010
Emissivity measurements carried out with the VIRTIS instrument aboard the European Space Agency's Venus Express spacecraft indicate that Venus has been volcanically active in recent geological times. This result, reported in the 8 April issue of Science, has important consequences for the understanding of the geological processes at work on the planet.

ESA Press Release at:
http://sci.esa.int/science-e/www/object/in...fobjectid=46815

If you haven't already seen it, Emily has written a fascinating and comprehensive entry on the volcanism discovery on the TPS blog. As usual it is thorough, entertaining, and accessible, even to us lay-people.

There's a press release on the latest aerodrag campaign now up on the ESA site at:

http://www.esa.int/esaCP/SEMUDKF098G_index_0.html

I did not realise they had done this in 08 and 09 too.

What the ESA release does not mention is that very similar windmilling experiments had been already carried out by Magellan in 1994

The big difference between the earlier campaigns and the one currently being done is that they are using the asymetrical settings of the wings to get more data. The earlier campaigns relied solely on flight dynamics being able to tease out the information from the orbit data. The models of the upper atmosphere at Venus are not very good, and no one knew what to expect, so there wasn't much to see because they were lowering the orbit very slowly into an area of very low density. Using the wheels to measure the torque, it is easier and more accurate in some ways, but difficult to become confident in your computed absolute density value because of the assumptions and calculations you have to make, such as the surface area of the spacecraft body at various angles. But using both techniques at the same time helped to give confidence in the numbers out of the new technique.

It is certainly true that Magellan did all this first. That was the first time anyone did it, and how NASA learned to do it. ESA is using the same laboratory, but with better equipment. Magellan was a flying scrap heap by the time we did this. The antenna had to be pointed to Earth during the drag passes, because the (pre-digital) tape recorders were gone and there was no way to store data. So the windmilling technique was required as the spacecraft could only rotate around the antenna axis and stay on the Earth. VEX is lucky to have a healthier spacecraft, and so has more flexibility about how to do these passes. VEX can windmill, or paddlewheel (one panel perpendicular, one tilted at an angle), and they don't have to be Earth pointing during the drag passes.

How does this test compare to aerobraking? I'd assume a level of many magnitudes as to accuracy of the components in the atmosphere.

For the drag campaigns, we're trying to work out the techniques while also seeing how the results compare to models of the atmosphere. What we are not trying to do is change the orbit. If our extension is approve for operations in 2013 and 2014, and it is approved, we'll use what was learned in the drag campaign to then use a much higher level of drag (drop lower into the atmosphere) to significantly change the orbit. Slowing down via aerodrag at pericenter will allow us to significantly reduce the apocenter to a yet undetermined level.

I guess you would want to do it, for operational purposes, at a nice fraction of the 24 hours.... 18, 12, 6 hrs perhaps?

I found myself trying to explain these aero-passes to someone with both arms stuck out like a windmill the other day

Exactly right. The desired orbit period is based as much on operations (cost for staffing outside of normal working hours) as it is on science.

And if you are sticking out your arms to explain this, then you're doing it exactly right. We look goofy in our conference room when we're talking about it, three or four people twisting their arms around.

I would love to see a photo of that.

I don't have a photo of that. So here's a photo of my radar hat, when I worked on Magellan. Careful observers will note the attention to detail, with the radiometer cone on the left side, and the altimeter antenna on the right ear.

I hope they've renovated building 230 since then.

Impressive. Looks like your focused brain energy blew out the fluorescent light above you!

Marvelous.

Great attention to detail.

From the bygone era when engineers wore ties.

It's a good thing you didn't try it outside in the rain.

Andy

Venus Express (and all the other ESA operating missions) has been extended until 2014. Excellent news for people working on the mission.

More information is in the ESA press release at:

http://www.esa.int/esaCP/SEMR1MIRPGG_index_0.html

You had mentioned earlier upthread about using drag to lower the orbit once approved for an extended mission. Any details yet on that?

Regarding the orbit lowering, the current aerodrag campaigns are useful science and a good precursor for it. But the spacecraft wasn't designed for the dynamic pressures of high levels of drag. And using low levels of drag, within everyone's comfort zone, means that the orbit lowering would take a long, long, long time. During which not much science would get done. The drag is at pericenter, which is also where most of the science data is taken. And the attitude for drag lowering wouldn't allow pointing the instruments where needed.

So my current impression is that things are still being discussed, but any serious orbit lowering with drag passes would fit better at the very end of mission. Surprises then don't forfeit a lot of science. So 2014 or later, depending when our fuel and money run out.

To put this issue to bed in the forum, Venus Express will not be doing aerobraking before end of mission.

ESA held a full review board to look at the question of performing aerobraking with Venus Express. After a lot of good work, it was decided that it just wasn't worth it. At least, right now.

The original idea was to use aerobraking to drop the orbit from a 24 hour period to an 18 hour period, making use of the regular periods when the pericenter altitude dropped quite low. Instead of raising the pericenter height as is done now, well before hitting atmosphere, could we use the periods of low pericenter height to use atmospheric drag to slow the spacecraft at pericenter, which would drop the apocenter, and reduce the orbit period to a level where the science would be better.

Turns out that the allowed dynamic pressure on the spacecraft would not be enough to get the orbit down to 18 hours, or even close. Therefore, there was no scientific justification for the added expense and added risk.

However, the idea of doing hard aerobraking after the end of the science mission is still very much under consideration. Just as the dying Magellan spacecraft was used many years ago, Venus Express may end its active life by becoming an aerobraking test bed.

I am very happy to mention that a special issue of Icarus will be coming out in February that is dedicated to advances in Venus science, primarily due to Venus Express data. This issue is largely based around presentations for meetings in 2010.

The 40 papers that make up the issue can already be viewed on-line. The contents can be browsed at http://www.sciencedirect.com/science/journal/00191035/217/2

too bad they are not free to access

The European Space Agency (ESA) has two sets of web sites; one for the general public, and one that is a little more technical. On the latter, the Science and Technology pages, there is one for Venus Express (VEX). And on that page is a link to a monthly operations report (MOR). Which until recently had been last updated in the middle of 2010.

We're trying to get the status reports up to date, and then hope to keep them current with regular updates. Currently on-line as of today are reports up to September of 2011. We'll try to get them up to date before too much longer.

For anyone interested, the Venus Express page on the ESA Science and Technology pages is at:

http://sci.esa.int/venusexpress

And the most recent Venus Express status report is listed on the SciTech home page:
http://sci.esa.int

The Venus Express status reports are available through the end of 2012 at:

http://sci.esa.int/science-e/www/object/in...mp;fareaid_2=63

... and it just took a bit of a hit from the recent solar storm...

http://www.space.com/14834-solar-storm-bli...spacecraft.html



Phil

esaoperations tweeted this 3 hours ago

Venus Express is currently in what is called quadrature operations, where the spacecraft is tilted 10 degrees when Earth pointing in order to keep the Sun out of the Venus Monitoring Camera field of view. This puts a lot of thermal constraints on the operations. They expect to get back to normal science operations within a few days, but the quadrature thermal restrictions slow things down a bit. So far, everything looks fine with the trackers, though.

ESA science tweeted this this morning



any more info? VEx is getting prepared for what exactly?

I don't know, but presumably any communication is impossible, so it may need to be protected from potential problems (certain safe modes etc.) during this period.

Phil

I don't know what they were tweeting. But the transit observations are being scheduled right now. The bus will be left largely nominal. There are no comms for three days, but the science instruments will operate during that period to capture data simultaneously with ground observations. On the back side, in eclipse, the ground track will happen to be over an area that is suspected of volcanic activity, and eclipse allows an attempt to get low-res images of the ground at about the same time as the transit.

VEX is back to nominal operations now.

http://www.esa.int/SPECIALS/Operations/SEM402BYLZG_0.html

We're hard to kill.

The status report for the period 15 January to 4 February 2012 is now
at the VEX Status Archive.

The VEX Mission Operations Report number 244 is now on-line at the VEX Status Report Archive,
here.


This report covers the 76th month of operations, including the start of the special 'quadrature' operations.

Thank you cndwrld, you guys plan anything special for the transit in about a months time?

The unfortunate thing about the transit is that Venus is so close to the Sun that we will lose communications. We got permission to operate the instruments, but a difficult thermal situation and the need to store all the data in memory for three days makes it difficult to do some observations.

In the day before and after the transit, we will be taking spectroscopic cloud data of the southern latitudes, in coordination with ground observers. On the day of the transit, we'll be taking direct solar observations, as well as some atmospheric observations using the sunlight diffraction in the upper to middle atmosphere.

At the European Space Astronomy Centre, the VEX team just put on a series of talks about the Transit, and how important they were historically and also how much they are still useful. But, if one is actually in orbit around Venus, there isn't really anything different than normal.

From what I've seen, the most interesting possible use of the transit and VEX is for studies about exoplanet atmospheres. We discover exoplanets outside our solar system by noticing their transits in front of their associated stars. With enough resolution, it is possible to resolve some details of the exoplanet atmospheres. So far, only done for a very few planets which are incredibly large gas planets. And it is incredibly difficult.

Think about our solar system: if one looked at our planets from afar as exoplanets, how would we remotely tell the difference between two almost identical planets, Earth and Venus, where one is Eden and the other is Hell?

The transit of Venus allows a test case. We can resolve the Venus atmosphere from Earth at the transit ingress and egress. VEX can use the SOIR instrument to record sunlight as the spacecraft goes behind the planet, 'following' the Sun as the light goes through the atmosphere. The data taken by VEX can be used as a baseline to compare the data taken of the refracted sunlight through the atmosphere as seen by Earth ground observers. It is hoped that this will be a useful test case for developing techniques to detect exoplanet atmospheres, as well as learn how to detect basic compositions of those atmospheres. That might allow researchers to determine which exoplanets might have habitable atmospheres, and which definitely do not.

Will it work? Who knows. It's Science!!

Thank you for your long reply.
And yes I did in fact expect that you would loose communications with Venus express during the actual transit.
So perhaps I should have phrased my question as if you had anything else planned, public outreach program or whatever.

But yes, it is a good idea to use the transit as a testbed for exo-planet studies.
Not that I actually think we will find a second Earth any time soon, but such studies will be make it possible to find the promising planets for in-depth studies when the technology (and funding) might be available.

For public outreach, the Venus Express Science Operations Centre is sending two people to Svalbard Island, above the Arctic Circle, with a solar telescope. Where we're located, near Madrid, there's no visibility. And there's limited visibility in Europe (for the most part). But above the Arctic Circle, the Sun doesn't set, so the transit will be visible. We have the 9" solar telescope, plus a normal telescope, and the mount. The team is finalizing testing now. And if the weather cooperates, we'll show the transit on the Web, live from Svalbard.

There is also a second team, with identical telescopes, who are going to Australia. They'll be watching the transit from the NASA Deep Space Network station near Canberra, and also broadcasting live on the Web.

For people in Europe, the EuroNews network has taped interviews at ESAC for the transit. They are putting together one of their nice 30 minute science shows about the transit, which will be out (I'm guessing) right before the transit.

That's all I know about right now.