Venus Express Options

[stevesliva]

Nice! Lot of potential in those frames.

[cndwrld]

The latest Venus Express status report is on-line, with the results for mid-September to mid-October 2012. This is report 252, for our 84th monthly planning cycle (MTP084).
The Science and Technology page for Venus Express is here, and then you click on the Latest Status Report link.

[cndwrld]

29 January 2013

ESA’s Venus Express has made unique observations of Venus during a period of reduced solar wind pressure, discovering that the planet’s ionosphere balloons out like a comet’s tail on its nightside. The results are discussed on the ESA web page here .

[cndwrld]

The latest Venus Express status report is on-line, with the results for mid-October to mid-November 2012. This is report 253, for our 85th monthly planning cycle (MTP085).
The Science and Technology page for Venus Express is here, and then you click on the Latest Status Report link and choose report 253.

[cndwrld]

Latest Venus Express status report on-line for January 2013, at http://sci.esa.int/science-e/www/object/in...fobjectid=51597. It is, of course, written in the required humorless way. But I try to explain things so that people new to this stuff can understand it. If you find mistakes or things that aren't clear, please let me know.

And for your information, the ESA Science & Technology web pages (including for Venus Express) have been upgraded to a new format. It looks a lot better. The link to the Venus Express SciTech page is http://sci.esa.int/venusexpress.

[cndwrld]

The Venus Express Mission Operations Report 257, for our 89th monthly planning cycle, is now on-line.

It includes an overview of our simultaneous seasons of solar eclipses and Earth occultations, targets for the surface mapping campaign, and an explanation of how we manage orbit correction maneuvers as fuel and oxidizer tanks approach low liquid levels in zero gravity.

VEX Mission Operations Report 257 (Planning Cycle 089))

[cndwrld]

The Venus Express mission operations summaries now go up to the end of April 2013. Reports 258 and 259 are available.

These two reports cover the entry into, and exit from, the superior conjunction shutdown, automation of spacecraft passes at the Mission Operations Centre and thermal fuel gauging tests.

The status report archive is here.

[Doug M.]

It includes an overview of our simultaneous seasons of solar eclipses and Earth occultations, targets for the surface mapping campaign, and an explanation of how we manage orbit correction maneuvers as fuel and oxidizer tanks approach low liquid levels in zero gravity.

I understand that measuring remaining levels of fuel in a spacecraft is something of a black art. That said, do we have an idea approximately how much fuel remains, and how long it's likely to last?

By the way, these are great -- thank you for posting them, and please do continue.


Doug M.

[cndwrld]

I understand that measuring remaining levels of fuel in a spacecraft is something of a black art. That said, do we have an idea approximately how much fuel remains, and how long it's likely to last?

By the way, these are great -- thank you for posting them, and please do continue.


Doug M.

We typically get zero feedback for the public outreach stuff, so thanks for the note.

The fuel/ox level measurement is quite the black art. What we have right now is the numbers from the archaic but still prevalent method on all spacecraft: bookkeeping. Those numbers tell us that we can make it to at least December 2014 and probably a bit later. But there's enormous uncertainty in those numbers after 7 years of daily burns. The numbers from the new method are still being evaluated. And there's only been one advanced test, so we'll have one data point from that. Maybe next year we'll get more tests, and numbers. For now, that's all we've got.

[Doug M.]

We typically get zero feedback for the public outreach stuff, so thanks for the note.

You're very welcome! Seriously, I check in every couple of months and skim a bunch of these. Read like that, they're really interesting. A bit dry, but that's to be expected. They give a good picture of what it's like to actually run a spacecraft over time.

The fuel/ox level measurement is quite the black art. What we have right now is the numbers from the archaic but still prevalent method on all spacecraft: bookkeeping. Those numbers tell us that we can make it to at least December 2014 and probably a bit later. But there's enormous uncertainty in those numbers after 7 years of daily burns. The numbers from the new method are still being evaluated. And there's only been one advanced test, so we'll have one data point from that. Maybe next year we'll get more tests, and numbers. For now, that's all we've got.

I assume that fuel is the limiting factor? If you had enough fuel to go to, say, 2016, there'd be nothing else that would stop you from continuing the mission?

Also, according to the mission FAQ online the plan is to decommission VE with a terminal burn into the atmosphere. Is that still the plan -- and if so, wouldn't you want a reserve of fuel for that final burn?


Doug M.

[Explorer1]

Well, the orbit would decay sooner or later, given the sun's influence. It's only a matter of how soon it will happened.

[Doug M.]

Well, the orbit would decay sooner or later, given the sun's influence. It's only a matter of how soon it will happened.

Right, but IIUC once they run out of fuel, they won't be able to stabilize the orbiter, and they'll lose contact with Earth. Whereas, if they keep a bit of fuel, they can get some science from that terminal orbit -- observations at a much lower altitude than they would otherwise have dared. At least, that's the plan with Cassini and with MESSENGER. Don't know about Venus Express.


Doug M.

[cndwrld]

Right, but IIUC once they run out of fuel, they won't be able to stabilize the orbiter, and they'll lose contact with Earth. Whereas, if they keep a bit of fuel, they can get some science from that terminal orbit -- observations at a much lower altitude than they would otherwise have dared. At least, that's the plan with Cassini and with MESSENGER. Don't know about Venus Express.


Doug M.

The VEX spacecraft is in great shape. I'm continuously surprised by how robust it has been. All the usual consumables (batteries, wheels, solar panels, star trackers) are in great shape. Kudos to Astrium. We're just running out of gas.

The plan for the final day is, as you say, a controlled burn into the atmosphere. At Venus, we all get a Viking funeral. And the 'control' part is the hard part. But once the fuel is gone, there's always something left. We say 'fuel' and sort of mean three things: fuel, oxidizer (in our case, a dual system) and pressurant. When the fuel or ox runs dry, there's still impulse to be gained just by pushing out the other fluid. And even when both the fuel and ox are gone, you can still blow the helium out. Neither of the latter two options give you much, but we won't need much. Our apocentre is very high; just blowing helium out for a while would probably be enough to tip our pericentre low enough so that in a few orbits we'd be toast.

I'm sorry the status reports are so dry. Sigh. There's nothing I can do. The alternative is to have nothing at all.

[Doug M.]

The VEX spacecraft is in great shape. I'm continuously surprised by how robust it has been. All the usual consumables (batteries, wheels, solar panels, star trackers) are in great shape. Kudos to Astrium. We're just running out of gas.

It's the same with Mars Odyssey, Cassini, and MESSENGER. It really is striking how many long-lived spacecraft we have out there now. Even putting aside the Voyagers, I know of well over a dozen space probes and comsats that are over 10 years old and still in good repair and active. (And I'm sure there are plenty more that I don't know of.) It's particularly impressive for a probe like VEX that is in a challenging thermal and radiation environment.

The plan for the final day is, as you say, a controlled burn into the atmosphere. At Venus, we all get a Viking funeral. And the 'control' part is the hard part. But once the fuel is gone, there's always something left. We say 'fuel' and sort of mean three things: fuel, oxidizer (in our case, a dual system) and pressurant. When the fuel or ox runs dry, there's still impulse to be gained just by pushing out the other fluid. And even when both the fuel and ox are gone, you can still blow the helium out. Neither of the latter two options give you much, but we won't need much. Our apocentre is very high; just blowing helium out for a while would probably be enough to tip our pericentre low enough so that in a few orbits we'd be toast.

So, basically you could alter your orbit by mechanical rather than chemical means! Very cool.

cheers,


Doug M.

[stevesliva]

Gravity Probe B spent a lot of time blowing out helium...