Subscribe free to our newsletters via your
. 24/7 Space News .




VENUSIAN HEAT
Venus Express goes gently into the night
by Staff Writers
Paris (ESA) Dec 18, 2014


Visualisation of Venus Express during the aerobraking manoeuvre, which will see the spacecraft orbiting Venus at an altitude of around 130 km from 18 June to 11 July. In the month before, the altitude will gradually be reduced from around 200 km to 130 km. If the spacecraft survives and fuel permits, the elevation of the orbit will be raised back up to approximately 450 km, allowing operations to continue for a further few months. Eventually, however, the spacecraft will plunge back into the atmosphere and the mission will end. Image courtesy ESA-C. Carreau.

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.

Since its arrival at Venus in 2006, Venus Express had been on an elliptical 24-hour orbit, traveling 66 000 km above the south pole at its furthest point and to within 200 km over the north pole on its closest approach, conducting a detailed study of the planet and its atmosphere.

However, after eight years in orbit and with propellant for its propulsion system running low, Venus Express was tasked in mid-2014 with a daring aerobraking campaign, during which it dipped progressively lower into the atmosphere on its closest approaches to the planet.

Normally, the spacecraft would perform routine thruster burns to ensure that it did not come too close to Venus and risk being lost in the atmosphere. But this unique adventure was aimed at achieving the opposite, namely reducing the altitude and allowing an exploration of previously uncharted regions of the atmosphere.

The campaign also provided important experience for future missions - aerobraking can be used to enter orbit around planets with atmospheres without having to carry quite so much propellant.

Between May and June 2014, the lowest point of the orbit was gradually reduced to about 130-135 km, with the core part of the aerobraking campaign lasting from 18 June to 11 July.

After this month of 'surfing' in and out of the atmosphere at low altitudes, the lowest point of the orbit was raised again through a series of 15 small thruster burns, such that by 26 July it was back up to about 460 km, yielding an orbital period of just over 22 hours.

The mission then continued in a reduced science phase, as the closest approach of the spacecraft to Venus steadily decreased again naturally under gravity.

Under the assumption that there was some propellant still remaining, a decision was taken to correct this natural decay with a new series of raising manoeuvres during 23-30 November, in an attempt to prolong the mission into 2015.

However, 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."

Unlike cars and aircraft, spacecraft are not equipped with fuel gauges, so the time of propellant exhaustion for any satellite - especially after such a long time in space - is difficult to predict. The end could not be predicted but was not completely unexpected either.

Without propellant, however, it is no longer possible to control the attitude and orient Venus Express towards Earth to maintain communications. It is also impossible to raise the altitude further, meaning that the spacecraft will naturally sink deeper into the atmosphere over the coming weeks.

"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."

"During its mission at Venus, the spacecraft provided a comprehensive study of the planet's ionosphere and atmosphere, and has enabled us to draw important conclusions about its surface," says Hakan Svedhem, ESA's Venus Express project scientist.

Venus has a surface temperature of over 450 C, far hotter than a normal kitchen oven, and its atmosphere is an extremely dense, choking mixture of noxious gases.

One highlight from the mission is the tantalising hint that the planet may well be still geologically active today. One study found numerous lava flows that must have been created no more than 2.5 million years ago - just yesterday on geological timescales - and possibly even much less than that.

Indeed, measurements of sulphur dioxide in the upper atmosphere have shown large variations over the course of the mission. Although peculiarities in the atmospheric circulation may produce a similar result, it is the most convincing argument to date of active volcanism.

Even though the conditions on the surface of Venus are extremely inhospitable today, a survey of the amount of hydrogen and deuterium in the atmosphere suggests that Venus once had a lot of water in the atmosphere, which is now mostly gone, and possibly even oceans of water like Earth's.

Also just like Earth, the planet continues losing parts of its upper atmosphere to space: Venus Express measured twice as many hydrogen atoms escaping out of the atmosphere as oxygen atoms. Because water is made of two hydrogen atoms and one oxygen atom, the observed escape indicates that water is being broken up in the atmosphere.

Studies of the planet's 'super-rotating' atmosphere - it whips around the planet in only four Earth-days, much faster than the 243 days the planet takes to complete one rotation about its axis - also turned up some intriguing surprises. When studying the winds, by tracking clouds in images, average wind speeds were found to have increased from roughly 300 km/h to 400 km/h over a period of six Earth years.

At the same time, a separate study found that the rotation of the planet had slowed by 6.5 minutes since NASA's Magellan measured it before completing its five-year mission at Venus 20 years ago. However, it remains unknown if there is a direct relationship between the increasing wind speeds and the slowing rotation.

"While the science collection phase of the mission is now complete, the data will keep the scientific community busy for many years to come," adds Hakan.

"Venus Express has been part of our family of spacecraft in orbit since it was launched in 2005," says Paolo Ferri, Head of ESA Mission Operations.

"It has been an exciting experience to operate this marvellous spacecraft in the Venus environment. The scientific success of the mission is a great reward for the work done by the operations teams and makes us more proud than sad in this moment of farewell."

"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."

"Venus Express was an important element of the scientific programme of ESA and, even though mission operations are ending, the planetary science community worldwide will continue to benefit from more than eight years of Venus Express data and major discoveries which foster the knowledge of terrestrial planets and their evolution," says Alvaro Gimenez, ESA's Director of Science and Robotic Exploration.

Summary of the first science results from the aerobraking campaign can be found here


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
Venus Express at ESA
Venus Express News and Venusian Science






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








VENUSIAN HEAT
Venus Express anomaly
Paris (ESA) Dec 08, 2014
On 28 November 2014, the flight control team at ESOC reported loss of contact with Venus Express. It is possible that the remaining fuel on board VEX was exhausted during the recent periapsis-raising manoeuvres (see blog post here) 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 ... read more


VENUSIAN HEAT
'Shooting the Moon' with Satellite Laser Ranging

Moon Express testing compact lunar lander at Kennedy

UK Plans to Drill Into Moon, Explore Feasibility of Manned Base

Carnegie Mellon Unveils Lunar Rover "Andy"

VENUSIAN HEAT
Australian university students aim to generate first 'breathable' air on Mars

Opportunity drives on in no-flash mode

Flying over Becquerel

New idea for transporting spacecraft could ease trip to Mars

VENUSIAN HEAT
XCOR Announces Further Progress on XCOR Lynx Spacecraft

NASA releases video of Orion spacecraft re-entry from astronaut's perspective

Russia, US to Cooperate on Orion Spacecraft Modernization

NASA Voyager: 'Tsunami Wave' Still Flies Through Interstellar Space

VENUSIAN HEAT
China's Long March puts satellite in orbit on 200th launch

Countdown to China's new space programs begins

China develops new rocket for manned moon mission: media

Service module of China's returned lunar orbiter reaches L2 point

VENUSIAN HEAT
NASA, SpaceX Update Launch of Fifth SpaceX Resupply Mission to ISS

Politics no problem, say US and Russian spacefarers

Bright lights: big cities at night

ISS Experiment May Hold Key to Alzheimer's Cause

VENUSIAN HEAT
SpaceX postpones launch after rocket 'issues'

SES: Astra 2G ready for december 28 proton launch

US Space Launcher to Get 60 Russian Engines in $1Bln Deal

State Spaceports Receive Federal Funding

VENUSIAN HEAT
Kepler Proves It Can Still Find Planets

NASA's Kepler Reborn, Makes First Exoplanet Find of New Mission

Super-Earth spotted by ground-based telescope, a first

Astronomers spot Pluto-size objects swarming about young sun

VENUSIAN HEAT
NASA just emailed the space station a new socket wrench

Inmarsat-2 F2 satellite retired after more than 23.5 years of GEO operations

Penn Research Outlines Basic Rules for Construction With a Type of Origami

Dutch Navy LPD getting new radar system




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.