European Venus Express Spacecraft May Be Out of Fuel

[Buster's Uncle]

European Venus Express Spacecraft May Be Out of Fuel
SPACE.com
By Mike Wall  2 hours ago



Artist's concept of Europe's Venus Express spacecraft, which has been studying Venus from orbit since 2006.



The end may be near for Europe's venerable Venus probe.

On Nov. 28, mission controllers lost contact with the European Space Agency's (ESA) Venus Express spacecraft, which has been circling Earth's hellishly hot "sister planet" for more than eight years. Over the past few days, the team was able to re-establish limited contact and also downlink some data, confirming that Venus Express' solar arrays are pointed at the sun as desired, mission officials said.

The reasons for the communications blackout remain unclear at the moment, but one possibility is that the probe has finally run out of fuel.

"It is possible that the remaining fuel on board VEX was exhausted during the recent periapsis-raising maneuvers … and that the spacecraft is no longer in a stable attitude (the spacecraft’s high-gain antenna must be kept pointed toward Earth to ensure reliable radio contact)," ESA officials wrote in a blog post Friday (Dec. 5. ).

Those maneuvers began on Nov. 23 and were intended to raise Venus Express' orbit, which was lowered during a dramatic "aerobraking" campaign this past summer.

The aerobraking moves took Venus Express deep into Venus' thick atmosphere, often getting the probe within 81 to 84 miles (131 to 135 kilometers) of the planet's surface. The goals were twofold, mission officials said — to sample regions of the Venusian atmosphere that weren't well known, and to test out aerobraking for use on future missions as a trajectory- and orbit-altering strategy.

Venus Express arrived in orbit around Venus in April 2006, with plans calling for a two-year primary mission life and then perhaps two more years of extended operations. The probe has outlasted expectations significantly, but it cannot keep going forever; sooner or later, its fuel will run out, and Venus Express will make one final dive into the Venusian atmosphere.

Mission team members aren't sure exactly how much propellant remains onboard, but they know it can't be much. In fact, the probe's handlers weren't certain that Venus Express would be able to perform last month's orbit-raising maneuvers.

The continuing investigation into the Nov. 28 communications blackout may reveal the answer.

"The operations team is currently attempting to downlink the table of critical events that is stored in protected memory on board, which may give details of the sequence of events which occurred over the past few days," ESA officials wrote in the Friday blog post. "The root cause of the anomaly (fuel situation or otherwise) remains to be established. We will provide an update as soon as something more concrete is known."


http://news.yahoo.com/european-venus-express-spacecraft-may-fuel-171349193.html

[Geo]

Perhaps the antenna array got damaged during this aerobreaking manoeuver?

[Buster's Uncle]

I don't understand any of this.

[Geo]

The probe dipped in the Venusian atmosphere, creating stress and heat on its parts. Perhaps some parts got enough damaged because of this.

[Buster's Uncle]

No, I got that - I was thinking about the last Venus Express article I saw, that made nonsensical claims about how deep it was in the atmosphere, for how long.

[Geo]

...131 to 135 kilometers)

You mean this distance to the surface?
If correct, that's still over a hundred kilometers inside the atmosphere. But it sounds fishy to me. At that depth, the probe should've been disintegrated since Venus' atmosphere is about 250 km thick.

[Buster's Uncle]

Yeeess.

Doesn't sound possible.  The artist's conceptions I keep seeing are not of an atmospheric probe.  At the very best, they're explaining badly - it sounds like complete bullcrap fantasy.

[Unorthodox]

The whole aerobraking thing was a calculated long shot that they expected to be suicide in the first place, just trying to get a last bit of data from an unexplored portion of the atmosphere.  It was also a test for aerobraking, as if we can figure that out, it would be loads more efficient to use in the future.  Yes, distance is correct, it surviving is a surprise, bits damaged is not. 

[Buster's Uncle]

I'd have sworn that a story a couple of months ago had the VE deep in the atmosphere for over a week - yeah, no; I don't believe that.

[Unorthodox]

Sort of.  The periapsis was in the atmosphere for a week.  So, each orbit (don't know how long one took off the top of my head) would dip it into the atmosphere for a period before it climbed back out.  Thus, each orbit's apsis would significantly lower (periapsis not so much).   

It didn't hover in the atmosphere for a week straight, no.   

VE was in a very eliptical orbit, they aerobraked it to something more circular, and TRIED to then raise the periapsis out of the atmosphere.  Sounds like it ran out of fuel before they could finish that final maneuver and it never stabalized it's antenna towards earth.   Whether it's in stable orbit or not at present, I really haven't looked into much. 

Well, it wouldn't be completely stable, but whether we're talking years or months depends on how well that last maneuver worked. 

[Buster's Uncle]

There's been some very bad science reporting when it come to Venus Express...

[Unorthodox]

More or less what they tried to do:

Kerbal Space Program: Eve Aerobraking and Orbit

[Buster's Uncle]

Still doesn't sound possible, to go that deep (repeatedly!) and not burn up or crash...

[Unorthodox]

They were surprised too, it was supposed to be suicide. 

[Buster's Uncle]

I wish the thing got more coverage - it can't have discovered nothing, and the magical orbital stuff is intriguing, if not total bull.