Impressive!



That's kind of sad IMO. Mars gets all the love

Venus Express will be starting aerobraking soon. Our first pericentre pass using the aerobraking mode is on Tuesday, 20 May. More details in the ESA announcement here.

Updates about the Venus Express aerobraking will be placed on the ESA Rocket Science blog at:

http://blogs.esa.int/rocketscience/

There will be a Google Hangout today (Thursday, 10 July 2014) to talk about aerobraking with Venus Express. Information can be found, along with information on the aerobraking, at the ESA Rocket Science Blog at http://blogs.esa.int/rocketscience/.

As of 09 July, we're at 130 kilometers. Before the aerobraking, we had never been lower than 165 Km. Aerobraking will end in a few days.

Venus Express has finished its amazing aerobraking campaign. The spacecraft got down to 129.1 Km at pericentre. During the normal mission, the pericentre was maintained between 250 to 450 Km. The lowest it ever got during the atmospheric drag experiments earlier in the mission was 165.5 Km. In those extra few kilometers, the spacecraft was experiencing a lot of pressure on the panels and structure. The final orbital period is not precisely known yet, but the orbit has certainly changed a lot.

The magnetometer and plasma/neutral particle detector were on during the aerobraking pericentre passes. And the spacecraft itself was an instrument in the aerobraking, as the data from the spacecraft dynamics and the heating will be analyzed for information on the upper atmosphere.

The spacecraft is now performing one apocentre motor firing each orbit, and has completed three of them so far. These will continue until the final pericentre altitude of 460 Km is reached on 25 July 2014, or the fuel runs out, whichever comes first. If the fuel runs out before we get to 460, the science will continue until we die in a fire. If we get all the burns, we may be able to operate as long as the end of 2014. But fuel is needed for momentum dumping on a regular basis. The end of mission all depends now on how much fuel is in the tanks, which is uncertain.

Not bad for a spacecraft which wasn't designed for this.

The updates are put on the ESA Rocket Science blog.

Is Venus Express still in operation? Having a hard time finding an update on the ESA sites.

I see a couple of entries ( 4 in total ) in the long range DSN schedule for the first two weeks in January 2015 ( DOY 6, 11, 12 and 13 ) for VEX - but the DSN schedule isn't particularly reliable that far out.

As of 28 July 2014, Up above the clouds so high:

I know they were running low on fuel .. so it has been about three months since that update. Guess no news is good news.

We're like the guy in the Monty Python movie; we're not dead yet.

The post-aerobraking status is that everything is exactly the same as at the start of aerobraking. Astrium built VEX very well. The post-aerobraking series of pericentre raising maneuvers were fine, and we got bumped up out of the atmosphere. We've been operating nominally ever since.

We are within the error bands of our bookkeeping fuel measurements. That means that we could run out of fuel at any time; we just don't know. Every day we do minor momentum dumps, but the most likely time it will happen is during an orbital correction maneuver (OCM) used to do the regular pericentre raising required at Venus. Our next set of OCM burns is beginning 23 November and is repeated for about 10 orbits. If we survive past that set of burns, the next set is in February. If we survive past that, the next set of burns is in June. And so on.

Scientifically, we're using our remaining time on two main issues, both related to volcanism: looking for surface volcanic activity with the infrared channel of our low resolution camera; and looking at atmospheric SO2 levels. The SO2 levels in the atmosphere have seen dramatic changes between the previous missions and VEX; and the levels are dropping over the lifetime of our mission. So it may be an indication of volcanic activity replenishing SO2 levels, which then drop. There are other activities, as well.

I tried to upload our long term planning poster for the year, but it is too large. Since there probably will not be another mission to Venus for 10 or 20 years, we're trying to get all the information that we can squeeze out of the mission. The ESA Communications office is overwhelmed with work on Rosetta at the moment, so there isn't much being done for other missions.

Happy to hear someone was interested in us.

Thanks for update cndwrld!

Would love to see continued Venus exploration.

Good to hear that VEX is working well. Venus as our close neighbor, and in many ways planet similar to Earth, deserve at least one spacecraft at any time.
Hopefully Akatsuki orbit insertion will be OK and our presence around this planet will be continuing.

Don, if you can provide me the poster in an email or dropbox link, I can host it and post a link here.

Hey now, I like Game of Thrones and all, but the nitty-gritty details are more interesting in the long run. Thanks for the update.

Here's the poster!

Due to solar effects, Venus Express must do regular burns to raise the pericentre of the orbit. These used to be done in a single burn. But because the fuel is so low, there is concern about how fast the fuel can collect on the fuel tank sponge. The burns are now broken into multiple small burns, to avoid burping.

And one day, there just won't be any fuel. We are currently well within the error bars of the measurements, so every burn (even a daily momentum dump of a few milligrams of fuel) could be the last one and therefore be the last day of the mission. But one of the bigger burns for pericentre raising is probably where we'll run out of fuel.

Sunday we started our most recent pericentre raising burn sequence. The first two burns, on Sunday and Monday, went well. Tomorrow, Tuesday, will be orbit 3151 (25-Nov-2014, DOY329). The plot attached shows our projected pericentre altitude for this 28 day medium term planning period, and our slowly increasing pericentre altitude as we do the sequence of nine burns.

Every day, we're hoping the burn worked. Either it works, or we're done. So it is a bit nerve wracking.

We know this might be the last mission to Venus for 20 years, so we are concious of trying to wring out every last bit of science data that we can.

Click to view attachment

Wow. Thanks for the update, cndwrld; a bittersweet situation for the program to be sure, but quite interesting in terms of fuel consumption modeling.

contact with VEx was lost last 28 November
http://blogs.esa.int/rocketscience/2014/12...xpress-anomaly/

EDIT: some telemetry packets have been received afterwards confirming the probe to be spinning

Well, it is now officially over.

Venus Express goes gently into the night

Thank you, Venus Express!

And farewell to Venus too, at least until whenever the next visitor shows up...

Yes, we're done. We have a few months of clean-up to do, to ensure everything gets documented and archived. Then we're off to other things.

The data archive will survive, and be used for a very long time. Especially since there may not be another serious mission for a very long time (although let's hope Akatsuki makes it into orbit in Nov 2015). The Planetary Science Archive at ESA is a great resource.

We can't be sure of the VEX pericentre altitude. But it is likely that it will burn up in late January 2015. There will be no way to know for sure exactly when it burns up, but there is no doubt that it will unless aliens refuel it. The spacecraft was in Sun hold mode, with its panels pointed to the Sun. We happen to have just come out of Superior Conjunction, so the spacecraft, when pointing at the Sun, put the Earth into a side lobe of the high gain antenna. This allowed us to get an unreliable but occasional downlink/uplink. The spacecraft, for the moment, can probably stay on the Sun using its thrusters and just pushing out gas. But the gas pressure is not enough to get you slewed around to direct Earth pointing and hold it, so each time the spacecraft tried that it panicked and stayed on Sun pointing. As it stays pointing at the Sun, the Sun-Venus-Earth angle grows every day, taking us out of the side lobe of the antenna. The angle was such that we finally lost even minimal contact, and we know it isn't ever going to improve.

Best guess is that the spacecraft stays Sun pointing until it gets a very slight nudge from the upper atmosphere. With only the gas pressure in the thrusters (if even that is left), the spacecraft will tumble and continue dropping about 3 km lower every day. Tumbling means that power is irregular from the panels, if they generate any at all. Eventually, the pericentre altitude will get low enough that the dynamic pressure of the atmosphere tears the MLI thermal insulation, when the electronics will fail due to loss of thermal control. At that point, it's brain dead. And eventually, the inert body will get trapped by the atmosphere and do its final plunge. Nothing is expected to survive down to the surface.

Astrium built a heck of a spacecraft. Its brother, Mars Express, continues to carry the flag at Mars. And Venus Express data will generate Ph.d's for decades, and be the basis for any future missions (as Venera and Pioneer Venus et al were for VEX). Every mission stands on the shoulders of the ones before.

On 31 January, I'll hoist a few drinks to Venus Express. After a decade, it will be weird to work on something else.

thank you for the update. just a quick question: is sporadic contact still maintained or was it lost for good? do we know the time of the last contact?

As far as I know, there won't be any more attempts at contact. They tried for a long time, but the geometry means that it is over.

Farewell VEX .

Can only add my own belated thanks to the VEX team for a job well done.

A hearty thank you to cndwrld for your final detailed report, and for all the other reports you've given us over the years.

Please let us know about your next project. I assume it will be on topic , but you should tell us (briefly) even if it isn't.

What an amazing mission. A big thank-you to all who worked on it.

I've got funding for about six months to finalize the stuff at the VEX Science Operations Centre. Then I expect to be moving over to Mars Express science operations. There's not a lot of fuel left on MEX either, but it needs very, very little to maintain orbit. So we hope it will keep working as well as it has so far, for some years to come. For me, that's great. I love looking a pictures of rocks. And living in Spain.

Venus Express is no longer functional, but it isn't dead yet. The ground station time was already booked and not suitable for other missions, so they look for VEX once a day. And we continue to see little bits of the carrier signal. There are too many variables to use the carrier signal for any kind of status information, but at least we know that our old friend is still alive at the moment.

ESA blog post here.

That's gotta be...more than a little heartbreaking. She's sure not gong down without a fight, though.

I am hoping we will be able to say - roughly - where Venus Express burns up over the planet. I have tried to find this for Pioneer Venus Orbiter and Magellan was well, without success.

We should be able to figure it out, assuming the time of the atmospheric entry is know. For VE we might not know exactly which orbit is its last, but we could extrapolate. For PVO and Magellan the exact entry orbit is known. Since we will have the periapsis latitude, and the orientation in space of both the orbit and the planet at that time, the entry area should be identifiable within a few hundred km (I'd settle even for 1000 km). But I can't put those things together myself. If anyone can put the geometry together for the older missions I would be very pleased to see it, and I hope the VE case will be possible as well even with limited or no telemetry, if we can approximate the time of entry.

Phil

I'd think, predicting uncontrolled re-entry is close to impossible.
A probe may enter the upper atmosphere, and leave it again.
During this aerobreaking the probe may disintegrate. Dependent of whether, when and to which degree the probe disintegrates, the drag coefficient, mass and area will change, all of which are relevant for the further fate. Density, temperature, wind, and composition of Venus' atmosphere are more variable parameters.
Assuming all parameters known, the resulting system of differential equations is called 'stiff', meaning it's numerically very unstable, and difficult to solve.

My expectation would be, that the probe will end up as several fragments settling at different locations almost along one or more (displaced by angle) circumferences.

Not really - it has to happen at periapsis so we know the latitude, and for near-polar orbits, if we know the plane of the orbit and the orientation of Venus we know the longitude. I don't see this like a 'skip entry' like Apollo or Chang'E 5 T1. And I only want an approximate position - just to say "over Alpha Regio" or "over Fortuna Tessera" would be quite sufficient. It should just be geometry - periapsis latitude plus or minus a bit and sub-surface longitude of that particular periapsis (plus or minus a couple of orbits if necessary, and for a slow-rotating planet that's not much difference). I just can't put it together myself.

I would actually expect the solution to be an ellipse a few hundred km wide and 1000 km long, approximately.

Phil

Determining the nominal periapsis points should be possible.
(Candidates for break-up.)

This WGCCRE paper, you co-authored, provides a basis for the orientation of Venus (Table I, c).
(Edit: For January 31, 2015, 12 h, I get d = 5509, hence W = 160.20 − 1.4813688d = 160.20 − 1.4813688 * 5509 = -8000.66 = 279.34 (mod 360) degrees east of point Q, one of the two intersections of the ICRF equator with the Venus equator.)

I didn't yet find the pointing of the orbital plane of VEX. The periapsis latitude should be 82° N.
The break-up is expected to be near the end of January 2015.

It's also a "glory" at this UK based site: http://www.atoptics.co.uk/droplets/gloab.htm. I think the other names are generally for other effects.

On the Wikipedia page Philip Laven's link is another one with a lot of explanation.

For anyone interested, here is an image from the Venus Express planning tool which shows the planned orbits from 04 January through 31-Jan-2015, DOY 031. If you want to take a whack at figuring out the final minutes of the mission, maybe this will help.

The pericentre height today was predicted to be at an altitude of 130 km.

Some explanations of the image:
*The planet position is that of the last orbit (orbit 3223).

*The centre of the image where the orbits cross is the north pole. The
right side is in darkness; the left side is lit. Atmosphere not
shown.

*The orbit track is from top to bottom.

*The purple triangles near the centre are the pericentre points. They are at Position [lat, long]: [73.6133799 (N), 159.509745 (E)] (degrees)

*The orbit track in yellow shows it is in sunlight; the orbit track in cyan
means it was in the dark. For example, the last orbit starts on the upper
left, goes past pericentre and over the pole. The image of the planet is
for the last orbit, so the orbit track changes to cyan as it crosses
the terminator.


First orbit: 3194 (04-Jan-2015, DOY004)
Final orbit: 3223 (31-Jan-2015, DOY031)

Click to view attachment

The latest press release on VEX status is here.

This is probably our last view of Venus Express.
ESA Rocket Science blog here.

I suppose this fits here.

'Hot Lava Flows Discovered on Venus' - VEX/ESA

Finally able to another peg in a long mystery, and (likely) another active planet in the solar system.

unfortunately the paper by Shalygin et al. is beyond the paywall
http://sci.esa.int/venus-express/56053-sha...ev-et-al-2015/#

We need to go back to Venus, it's been neglected for too long now.

A whole 6 months?

By December, there may be another chance to reaffirm these findings with Akatsuki, granted in a somewhat limited capability. But yeah, a couple Discovery class orbiters flown in parallel for some interferometric SAR or simultaneous left and right looking SAR, along with a multispectral imager with thermal for comparison to ground data. Would be a good update to what we have.

I don't see us going back to Venus any time soon, sadly. On the other hand, there are many year's worth of data in the VEX archive that has hardly been looked at yet. With the small size of the Venus science community, I think there are a lot of discoveries waiting in the PSA archive.

This would be a great time, if you're a grad student, to decide to focus on Venus. There's a ton of essentially new data available, and not a lot of competition to look at it. And if you master this stuff now, then you'll be solidly in the community when another spacecraft finally does get to Venus.

From several of the same associates including the primary author in 2012, 'Search for ongoing volcanic activity on Venus: Case study of Maat Mons, Sapas Mons and Ozza Mons volcanoes'. Seems likely that this is a similar process to what they were using in this new article.

Compared to the lead time for outer solar system missions, I bet another radar mission sneaks in there faster than you think.

I would be happy with a a lander mission

Well, if we drop it from an orbiter straight onto a then-actively-observed hotspot to find out if it's a vulcano we could save ourselves the radar...

Balloon.

Doing the aerobraking experiments at the end of the VEX mission was a ton of work. So we're all glad to see the first results published, and happy that the results are so interesting.

VEX AB- Astronomy Now

VEX AB - ESA