Venus Express Options

[cndwrld]

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.

[cndwrld]

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

[cndwrld]

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

[Poolio]

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.

[cndwrld]

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

[MahFL]

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

[Paolo]

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

[cndwrld]

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.

[brellis]

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

[cndwrld]

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.

[djellison]

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

[cndwrld]

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.

[elakdawalla]

I would love to see a photo of that.

[cndwrld]

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.

Attached thumbnail(s)

 

[Juramike]

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