Svetoslav - 15/4/2006 11:07 AMRead:http://www.esa.int/esaCP/SEM9FZNFGLE_index_0.html
The link Jacques has provided above leads to another page in which all the latest results of Venus Express are analyzed more thoroughly. Really interesting that they've found heavy water in the upper atmosphere, and the simulation of the interactions between the solar wind and Venus' atmosphere is amazing.
I'm still reading through it, but I like the way it's presented Amazing days we are living, undoubtedly.
Scientists using ESA's Venus Express are trying to observe whether Earth is habitable. Silly, you might think, when we know that Earth is richly stocked with life. In fact, far from being a pointless exercise, Venus Express is paving the way for an exciting new era in astronomy.Read more at:http://www.esa.int/esaCP/SEMUOW4N0MF_index_0.html
The Venus Express spacecraft, now orbiting Venus and much closer to the Sun than Earth, was affected by the radiation on 7 March.The startracker cameras that help Venus Express measure its position and orientation in space were ‘blinded’ starting at 01:41 GMT. "The Mission Control Team has taken the startrackers out of service and is maintaining the spacecraft's attitude using gyroscopes until the solar effects fade," says Octavio Camino, Venus Express Spacecraft Operations Manager at ESA’s European Space Operations Centre in Darmstadt, Germany.
ESA [email protected] #Venusexpress #startrackers were back functioning as of this AM at 03:25 UT
Six years of observations by ESA’s Venus Express have shown large changes in the sulphur dioxide content of the planet’s atmosphere, and one intriguing possible explanation is volcanic eruptions. The thick atmosphere of Venus contains over a million times as much sulphur dioxide as Earth’s, where almost all of the pungent, toxic gas is generated by volcanic activity.
An extension to the operations of Venus Express until 2015 was also approved, subject to a mid-term review and confirmation by SPC in 2014. This extension will allow an aerobraking campaign to be carried out within the timescale permitted by the remaining fuel on board.The next mission extension cycle will begin in mid-2014.
Aerobraking and end of Venus Express misiónAfter more than 10 years in orbit around Venus, the Venus Express mission will come to an end. Before the spacecraft runs out of fuel, it will be manoeuvred into the tenuous upper atmosphere of the planet, where it will conduct unique science while making engineering tests of aerobraking, potentially useful for future ESA missions. The mission will end as the spacecraft descends into denser atmospheric layers and burns up. Location: TBDExpected date: June
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.
http://www.esa.int/Our_Activities/Space_Science/Venus_Express/Venus_Express_gets_ready_to_take_the_plungeQuoteAfter 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.
The 25th aerobraking orbit (Number 2975 in the mission overall) was completed earlier today; on 11 June, during orbit 2973, the spacecraft dipped down to almost 140 km above the Venusian surface – an unprecedented low altitude.
On board Venus express, everything is functioning as expected and within limits: power, propulsion, communications, temperatures of spacecraft components, & etc.
The walk-in phase finishes today, and we are officially starting the aerobraking phase. Current pericentre altitude is around 136km, and we will drop naturally about 1km over the next week after which the pericentre altitude remains nominally constant [at about 135 km] to the end of aerobraking on 11 July.
the mission operations team at ESOC used the spacecraft's thrusters today to lower the pericentre altitude by 2.8 km; this pericentre-lowering manoeuvre (think of it as a 'push-down' manoeuvre) was done by firing the thrusters as Venus Express passed through apocentre. The thruster burn took place at 12:42 CEST (10:42 UTC), and the next - and unprecedented low - pericentre pass will now occur at 00:31 CEST on 24 June (22:31 UTC on 23.06). The manoeuvre should bring pressures to 0.4 N/m^2 by the mid-point of the aerobraking plateau on 29 June.
Yesterday morning, 2 July, the spacecraft performed another manoeuvre designed to lower the pericentre altitude by 0.8 km.This pericentre lowering is being performed in order to target higher atmospheric densities; the highest dynamic pressure (drag force) experienced by the spacecraft so far is 0.45 N/m2; the VEX team is aiming higher, trying to reach dynamic pressures of over 0.50 N/m^2. Atmospheric density at pericentre can vary by over 30% from one orbit to the next, making it difficult to know what atmospheric density will be reached on the next aerobraking pass...
Venus Express is now in the final week of its aerobraking campaign, and is about as low as it’s going to get. At its last pericentre passage, its altitude was only 129.9 km and this is expected to decrease to 129.1 km before the end of the aerobraking campaign.
... you may have noticed in the plots that Venus Express has reached its 3000th pericentre, in other words it has completed 3000 orbits around Venus (it reached this milestone on Monday 7 July). Reaching this milestone is especially impressive given that the spacecraft was originally designed for a nominal science mission of only 500 orbits!
After a month surfing in and out of the atmosphere of Venus down to just 130 km from the planet’s surface, ESA’s Venus Express is about to embark on a 15 day climb up to the lofty heights of 460 km.
.... VEX has successfully completed the last pericenter raising OCM (orbit correction manoeuvre) without problems.
Some facts on the OCMs:• Over the 15 OCMs, each thruster fired more than 8000 pulses and burned about 1.3 kilos of propellant (NTO and MMH) bringing the total consumption to around 5.2 kilos for the raising.• No degradation or signs of tank depletion was seen.• The spacecraft still seems to be in excellent shape.Meanwhile, the entire team is busy working to to restart full science on this new orbit.
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.
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.
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.
As we described last Friday, the operations team at ESOC are able to continue monitoring radio signals from Venus Express; they can 'see' the X-band carrier wave being transmitted from the spacecraft's high-gain antenna despite the fact that it is not pointed at Earth, although this, too, is steadily dropping off.
Venus Express mission manager Patrick Martin says that the most recent (calculated, not observed) altitude of VEX is now below the lowest ever achieved during the aerobraking campaign, and that loss of signal will most likely occur in a matter of days rather than weeks.
It's amazing that they can still do science even thought VX's loss of attitude control means that its observations can no longer be sent back to Earth. Using the high-gain transmissions as a sort of tracking beacon may yet reveal much about the density and radius of Venus's upper atmosphere.I wonder if they'll leave the Voyagers' transmitter on, even after they have to shut down the instruments, just to keep track of its position for as long as possible to get a picture of gravitational and galactic wind densities inside the heliosheath based on the probes' motion vs predictions?
Monitoring of the unmodulated X-band carrier signal being radiated by Venus Express has been conducted since the end of the mission was declared in December.
... the last detection of an intermittent carrier signal was on Monday, 19 January.
Note that around 15:00UTC on Sunday, 18 January, there was a massive spike in the carrier signal level (over 30 db!). This spike only lasted for a minute or so but looks to be consistent with the spacecraft's High Gain Antenna actually pointing at the Earth properly for short space of time – possibly that was Venus Express in 'Earth pointing' properly one last time.
"The signal is gone, while the spacecraft may continue orbiting Venus but under conditions which do not allow us to receive a signal. We will most likely continue to monitor next week in any case," says Patrick Martin, the Venus Express mission manager.
NASA's Venus Exploration Analysis Group (VEXAG) is meeting today. Agenda here:http://www.lpi.usra.edu/vexag/meetings/vexag_12/agenda.pdfVenus Express was briefed at 9:30.
While protons and other ions (shown in blue in the inset) feel a pull due to the planet's gravity, electrons (shown in red in the inset) are much lighter and thus able to escape the gravitational tug more easily.
QuoteWhile protons and other ions (shown in blue in the inset) feel a pull due to the planet's gravity, electrons (shown in red in the inset) are much lighter and thus able to escape the gravitational tug more easily.Although electrons are much 'lighter' - i.e. much less massive - and therefore the gravitational force between the particle and the planet is weaker, the effect of the force is greater because the electron is much less massive! It's a basic result that the acceleration of an object in orbit towards the planet due to gravity is independent of the mass of the object! (Combine F=ma with F=GMm/r^2.)How did ESA allow such rubbish to be published under its name?The correct explanation is likely to be that the electrons, being less massive, are moving much faster than the protons and other ions, so reach higher altitudes (just like rockets).
... When the magnetic field carried by the solar wind encounters Venus, it drapes around the planet's ionosphere (shown here in orange), drawing its particles away.While protons and other ions (shown in blue in the inset) feel a pull due to the planet's gravity, electrons (shown in red in the inset) are much lighter and thus able to escape the gravitational tug more easily.
Scientists have used ESA’s Venus Express to characterise the wind and upper cloud patterns on the night side of Venus for the first time-with surprising results.The study shows that atmosphere on Venus’ night side behaves very differently to that on the side of the planet facing the Sun (the ‘dayside’), exhibiting unexpected and previously-unseen cloud types, morphologies, and dynamics — some of which appear to be connected to features on the planet’s surface.“This is the first time we’ve been able to characterise how the atmosphere circulates on the night side of Venus on a global scale,” says Javier Peralta of the Japan Aerospace Exploration Agency (JAXA), Japan, and lead author of the new study published in the journal Nature Astronomy. “While the atmospheric circulation on the planet’s dayside has been extensively explored, there was still much to discover about the night side. We found that the cloud patterns there are different to those on the dayside, and influenced by Venus’ topography.”
Instead, the super-rotation seems to be more irregular and chaotic on the night side. Night side upper clouds form different shapes and morphologies than those found elsewhere-large, wavy, patchy, irregular, and filament-like patterns, many of which are unseen in dayside images — and are dominated by unmoving phenomena known as stationary waves.
“This study challenges our current understanding of climate modeling and, specifically, the super-rotation, which is a key phenomenon seen at Venus,” says Håkan Svedhem, ESA Project Scientist for Venus Express. “Additionally, it demonstrates the power of combining data from multiple different sources-in this case, remote sensing and radio-science data from Venus Express’ VIRTIS and VeRa, complemented by ground-based observations from IRTF’s SpeX. This is a significant result for VIRTIS and for Venus Express, and is very important for our knowledge of Venus as a whole.”
Given the very long days and nights on Venus, is the surface temperature significantly lower at night? Low enough to make a probe viable?John
Quote from: John-H on 09/18/2017 01:32 amGiven the very long days and nights on Venus, is the surface temperature significantly lower at night? Low enough to make a probe viable?JohnWhy would you send a probe to the surface to study winds and weather paterns? Floating or flying probes equipped with radar can get you all the required data.
Quote from: high road on 09/22/2017 03:03 pmQuote from: John-H on 09/18/2017 01:32 amGiven the very long days and nights on Venus, is the surface temperature significantly lower at night? Low enough to make a probe viable?JohnWhy would you send a probe to the surface to study winds and weather paterns? Floating or flying probes equipped with radar can get you all the required data.Floating is a good idea for atmospheric science, but you still need a lander vehicle for drilling, rock chemistry, and especially seismology.
Quote from: redliox on 09/23/2017 02:48 amQuote from: high road on 09/22/2017 03:03 pmQuote from: John-H on 09/18/2017 01:32 amGiven the very long days and nights on Venus, is the surface temperature significantly lower at night? Low enough to make a probe viable?JohnWhy would you send a probe to the surface to study winds and weather paterns? Floating or flying probes equipped with radar can get you all the required data.Floating is a good idea for atmospheric science, but you still need a lander vehicle for drilling, rock chemistry, and especially seismology.With current state of technology a surface probe will survive for just a few days, at most. Probably shorter. Challenges: very high atmospheric pressure, extremely high surface- and atmospheric temperatures and highly corrosive atmosphere.Had a lander for sustained surface operations (say longer than 2 days) been possible there already would have been sent one. That much I'm convinced of. But as the Venera's demonstrated the operational duration of surface probes on Venus is measured in minutes (hours at best), not days.
