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ESAhangout: How to surf the Venus atmosphere
Tomorrow, Jul 10, 4:00 PM - 5:00 PM
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After eight years in orbit, ESA’s Venus Express has completed routine science observations and has spent the last month orbiting through the planet's hostile atmosphere. Join Venus Express mission experts in our ESAhangout to talk about how to surf the Venus atmosphere.

Host: Emily Baldwin
Håkan Svedhem - Venus Express Project Scientist
Adam Williams - Venus Express Spacecraft Operations Manager
Colin Wilson - Venus Express Science Operations Coordinator
(TBC: Patrick Martin, Venus Express Mission Manager)

Thursday, 10 July, 15:00 GMT (17:00 CEST)

Click to play embedded YouTube video.

Venus Express plunging into the atmosphere

European Space Agency, ESA

Uploaded on 8 Jul 2014
After eight years in orbit, ESA's Venus Express has completed routine science observations and is preparing for a daring plunge into the planet's hostile atmosphere.

Venus Express was launched on 9 November 2005, and arrived at Venus on 11 April 2006.

It has been orbiting Venus in an elliptical 24-hour loop that takes it from a distant 66 000 km over the south pole -- affording incredible global views -- to an altitude of around 250 km above the surface at the north pole, close to the top of the planet's atmosphere.

With a suite of seven instruments, the spacecraft has provided a comprehensive study of the ionosphere, atmosphere and surface of Venus.

This video includes interviews in English with Håkan Svedhem, ESA mission scientist and Patrick Martin, ESA Venus Express mission manager.

http://www.esa.int/Our_Activities/Space ... ds_so_high
ESA’s Venus Express spacecraft has climbed to a new orbit following its daring aerobraking experiment, and will now resume observations of this fascinating planet for at least a few more months.
... This orbit will slowly decay again under gravity, but with only a few kilograms of fuel at most now remaining further altitude-raising manoeuvres may not be possible. If no further corrections are made, Venus Express will probably reenter the atmosphere again in December, but this time for good, ending the mission.

In the meantime, having survived not only the aerobraking experiment but also the most recent orbit-raising manoeuvres, all of the science experiments will be reactivated, continuing their detailed study of Venus for at least a few more months.
...

Click to play embedded YouTube video.

Venus Express Aerobraking - Credit: ESA, C. Carreau

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Click to play embedded YouTube video.

A Day in the Life of Venus Express
Credit: ESA/MPS/DLR/IDA, M. Pérez-Ayúcar & C. Wilson

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ESA’s Venus Express spacecraft has climbed to a new orbit following its daring aerobraking experiment, and will now resume observations of this fascinating planet for at least a few more months.

The orbit-raising followed a month of aerobraking that saw the spacecraft surf in and out of the atmosphere at altitudes typically between 131 km and 135 km for a couple of minutes on each of its closest approaches to the planet.

Before, normal operations involved an elliptical orbit every 24 hours that took Venus Express from 66 000 km over the south pole down to around 250 km at the north pole, just above the top of the atmosphere.

But, after eight years and with propellant running low, the Venus Express team began a daring aerobraking campaign, dipping the craft progressively lower into the atmosphere on its closest approaches.

The experiment directly explored previously uncharted regions of the atmosphere, while also providing information on how a spacecraft responds when encountering the tenuous upper reaches of an atmosphere at high speed.

Aerobraking can be used to reduce the speed of a spacecraft approaching a planet or moon with an atmosphere, allowing it to be captured into orbit, and to move from an elliptical orbit to a more circular one. Less fuel has to be carried, yielding benefits all round. The technique will be used on future missions and the Venus Express experiments will help guide their design. ...

Between altitudes of 165 km and 130 km, the atmospheric density increases by a factor of roughly a thousand, meaning that the forces and stress encountered by Venus Express were much higher than during normal operations.

It also experienced extreme heating cycles, with temperatures rising by over 100ºC during several 100 second-long passages through the atmosphere.

In addition, the atmospheric drag at these lower altitudes was so great that the spacecraft’s orbital period was reduced by more than an hour. ...

At the end of the campaign, 15 thruster burns raised the craft’s altitude, preventing it from dropping into the atmosphere. The last was executed on Thursday evening, boosting Venus Express to a new altitude of 460 km at its closest and 63 000 km at its furthest. This new orbit takes 22 hours 24 minutes to complete. ...

The Planetary Society blog: Close to the end for Venus Express
Posted by Emily Lakdawalla

2014/11/24 20:42 UTC

...ESA doesn't know exactly when Venus Express is going to run out of fuel, because it's actually a difficult problem to measure the amount of fuel remaining in a spacecraft fuel tank; most spacecraft fuel "gauges" are actually just bookkeeping of the amount of fuel used over the lifetime of a spacecraft. Small uncertainties in that bookkeeping add up over time, so it's hard to know just how empty the tank is. We're now within the error bars of ESA's estimate of where zero is.
...As long as Venus Express survives, it'll keep doing science. Venus Express science ground segment manager Don Merritt keeps us updated in the Venus Express thread at unmannedspaceflight.com:

'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 sulfur dioxide levels. The sulfur dioxide levels in the atmosphere have seen dramatic changes between the previous missions and Venus Express; and the levels are dropping over the lifetime of our mission. So it may be an indication of volcanic activity replenishing sulfur dioxide levels, which then drop. There are other activities, as well."

ESA news release November 11, 2014
As the end of its eight-year adventure at Venus edges ever closer, ESA scientists have been taking a calculated risk with the Venus Express spacecraft in order to carry out unique observations of the planet's rarefied outer atmosphere.

[Venus Express arrived at Venus on 11 April 2006. ]
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Having survived its dives into the atmosphere, Venus Express is continuing a programme of more routine science observations. However, the intrepid orbiter is living on borrowed time.

"Since July the pericentre of the orbit has been naturally decreasing again, and by the end of November we shall attempt to raise it once again," said Håkan Svedhem.

"Unfortunately, we do not know how much fuel remains in its tanks, but we are intending to continue the up-down process as long as possible, until the propellant runs out.

"We have yet to decide whether we shall simply continue until we lose control, allowing it to enter the atmosphere and burn up naturally, or whether we attempt a controlled descent until it breaks up."

Either way, the tough little spacecraft will have revolutionised our knowledge of Earth's mysterious, cloud-shrouded neighbour, sending back more data than all previous missions to Venus combined.

ESA: Venus Express goes gently into the night

Click to view full size image

Visualisation of the Venus Express aerobraking manoeuvre

16 December 2014

ESA’s Venus Express has ended its eight-year mission after far exceeding its planned life. The spacecraft exhausted its propellant during a series of thruster burns to raise its orbit following the low-altitude aerobraking earlier this year... full contact with Venus Express was lost on 28 November. Since then the telemetry and telecommand links had been partially re-established, but they were very unstable and only limited information could be retrieved.

“The available information provides evidence of the spacecraft losing attitude control most likely due to thrust problems during the raising manoeuvres,” says Patrick Martin, ESA’s Venus Express mission manager.

“It seems likely, therefore, that Venus Express exhausted its remaining propellant about half way through the planned manoeuvres last month.”

...“After over eight years in orbit around Venus, we knew that our spacecraft was running on fumes,” says Adam Williams, ESA’s acting Venus Express spacecraft operations manager.

“It was to be expected that the remaining propellant would be exhausted during this period, but we are pleased to have been pushing the boundaries right down to the last drop.”

"While we are sad that this mission is ended, we are nevertheless happy to reflect on the great success of Venus Express as part of ESA’s planetary science programme and are confident that its data will remain important legacy for quite some time to come,” says Martin Kessler, Head of ESA Science Operations.

“The mission has continued for much longer than its planned lifetime and it will now soon go out in a blaze of glory.”