Venus Express Options

[tedstryk]

If all goes well, Venus Express will be a major topic for discussion in this forum a year from now. Does anyone know how good the surface coverage will be from VIRTIS and VMC? My understanding is that VIRTIS will obtain low resolution multispectral maps, and that VMC will, in addition to cloud monitoring, have one channel that can see the surface, but I don't know at what resolution or at what quality. It will be nice to have some non-radar images of Venus' surface besides the Venera snapshots and the shadowy images from Earth and Galileo's NIMS.

Ted

[Guest_BruceMoomaw_*]

See my new note on the "Radar on Venus Express?" thread, Ted. I may be able to get you some more precise resolutional data later on if I can find the time. (However, VMC -- unlike VIRTIS -- cannot see the surface; it's entirely for UV cloud top patterns.)

[tedstryk]

Actually, VMC will have some limited capabliity to detect the surface. My source on this is the ESA mission documentation. See below:

3.7 VMC (Venus Monitoring Camera)
Precursors. Imaging of the Venus disc at different wavelength was carried out by the Pioneer Venus orbiter, during the fly-bys of Mariner-10 and Galileo, and from the ground. These data was used to study the atmospheric dynamics at the cloud tops (UV), to investigate the thermospheric dynamics (UV, visible, and near-IR airglow), to map the surface brightness and to study cloud opacity variations (near-IR). However, these observations lacked global spatial and temporal coverage as well as spatial resolution. At the same time they demonstrated the power of the global imaging in the study of dynamical processes in the Venus atmosphere.
VMC/Mars Express. The Video Monitoring Camera (VMC) onboard the Mars Express is a monochrome wide-angle CCD camera that was designed to take the video sequence of Beagle-2 lander leaving the Mars Express spacecraft at Mars.
VMC/Venus Express. The Study Team has recommended to modify the Mars Express camera into a wide-angle multi-channel Venus Monitoring Camera. The modification will consist of adding several narrow band filters in the UV, visible, and near-IR spectral ranges that would allow the camera to provide support imaging for the whole mission, achieve additional science goals, and contribute to the public outreach programme. Preliminary study showed that the modification of VMC will not specify additional requirements to the Mars Express bus and will be fully compatible with spacecraft interfaces. More detailed elaboration of the technical, programmatic, and financial issues related to the VMC modification and accommodation on the spacecraft will be done by the VMC team, Astrium, and ESA during the pre-Phase B study in the beginning of 2002 if the mission is approved. The modified VMC will be prepared in parallel with available VMC/Mars Express in order not to jeopardize the schedule of the mission. In case of failure to modify VMC in time VIRTIS will be able to cover significant part of the VMC goals so that the achieving of the mission objectives would be secured.
The VMC camera will be capable of achieving scientific goals in atmospheric dynamics and surface studies by means of global multi-channel imaging. An example of UV image expected from VMC at Venus is shown in Figure 2.2. Sequence of such images would allow one to visualize the motions of the cloud tops and to study the general circulation and wave phenomena at the altitude of ~70 km. Images of the Venus disc taken every 30 min will be used to create movies of the cloud motions and propagating waves that would be extremely valuable for investigation of the atmospheric dynamics. Figure 2.6 shows an example of image that VMC will take in the visible at night. The monitoring of airglow patterns that originate at 90-110 km is an efficient tool to study the dynamics of the Venus upper atmosphere. The VMC observations in the 1 m transparency “window” will give the images similar to those shown in Figures 2.5 and 2.9. These images have two types of features. Some of them belong to the surface and result from the temperature and emissivity variations. Second type of markings originates in the main cloud deck and indicates cloud opacity variations. The movies based on such imaging will be used to study global atmospheric dynamics at ~50km.
To summarize, VMC will fulfill the following scientific goals:
• Support imaging, i.e. global imaging context for the whole mission;
• Observations of the global cloud motions in the UV and near-IR spectral ranges;
• Study of distribution of the unknown UV absorber at the cloud tops;
• Monitoring the UV and visible airglow and its variability as dynamical tracer;
• Mapping the surface brightness temperature distribution and search for volcanic activity.
Besides important scientific goals the VMC imaging and movies will significantly contribute to the public outreach programme.

[Guest_BruceMoomaw_*]

You've caught me -- I was completely unaware of VMC's near-IR sensitivity. Very embarrassing.

[Mode5]

To the powers that be, thank you for creating this forum. It is the first I heard of this mission.

I am fascinated by Venus and looking forward to it now. It sounds like they are interested in studying the atmosphere extensively. Some of the questions they want to answer:

"What are the global characteristics of the atmosphere?"
"How does it circulate?"
"How does the composition of the atmosphere change with depth?"
"How does the atmosphere interact with the surface?"
"How does the upper atmosphere interact with the solar wind?"

The understanding and possible control/conversion of greenhouse gasses on Venus could directly benefit us on Earth. Terraform Mars? Too easy; I say we go for Venus!

Here are some excellent Magellan images of the surface.
http://www2.jpl.nasa.gov/magellan/images.html

[Gsnorgathon]

Ted - do you have a link for the ESA mission doc(s)?

[tedstryk]

http://megasn.obspm.fr/VEX_MDR51.doc

It is a bit dated in terms of VENSIS still being listed, but I don't think anything lese has changed.

[djellison]

I wonder if the effects of looking thru narrow spectral bands will result in the sort of quality we get at Titan - or something a bit better than that

Doug

[tedstryk]

Hard to tell. It is sort of like Pre-Cassini Titan, in that the limiting factor in all images we have is the resolution of the detector, so we don't know just how well we will be able to see. I will research this a bit more and see if I can dig up any speculation. Still, if Venus Express can take images at Cassini/ISS Titan resolution, they will look even more spectacular, because Venus is so much larger. And at last we will have some global multispectral data (although some data to this effect has been assembled from different Radar systems (PVO, Magellen, Venera, and the earthbased collection).

Anyhow, it seems the VMC, while it is a clone of the "Beaglecam" on Mars Express, seems to be hav converted in to quite a good little science instrument. Here is the info from the regular Venus Express website:
http://sci.esa.int/science-e/www/object/in...bodylongid=1448

[Guest_BruceMoomaw_*]

I can dig up some stuff on this for you, given a little more time (sorry it took me so long to even notice the question). As I recall, they're hoping for a resolution of roughly 30-50 km in VIRTIS' near-IR surface maps at Venus' poles, where it will be best -- but that may be just for its possible mineral maps, with the resolution of its actual albedo maps being a lot better.

[remcook]

I believe the spectral 'windows' are much less clear than for Titan, but for Galileo NIMS, some people have made temperature maps of the surface, clearly showing topography. quite cool

[edstrick]

My understanding is that the topographically related infrared brightness variations seen by Galileo at Venus were diffused through the lower atmosphere and then the dense middle cloud deck.

VIMS' middle infrared visibility of Titan's surface is quite good, compared with poor visibility and high amounts of diffuse scattering of reflected light in the 1 micrometer 'window" as seen by the Cassini imaging system.

My understanding is that at Venus, the atmosphere has no non-scattering transmission till you reach microwave wavelengths. Basically, imagine holding a sheet of blotchy waxed paper 50 km above the planet's surface and examining the diffuse patterns on the waxed paper from variable amounts and colors <spectral emissivity variations> of the surface below. The blotches will be constantly varying with time and location, but the color and brightnesses of the glow from beneath will be constant, and the color especially, can be separated from the blotchy cloud patterns <which themselves are interesting>

[Guest_Richard Trigaux_*]

It is sort of like Pre-Cassini Titan, in that the limiting factor in all images we have is the resolution of the detector, so we don't know just how well we will be able to see.

I think the main limiting factor in Cassini was not the instruments themselves, but the radio bandwidth available, together with very brief observation opportunities. This was all the more true for Huygens, which images were ridiculously small and tremendously compressed.

With Venus we have more solar power, and a much shortest distance. And, in orbit, we have the possiblity to take hundreds of images of the same surface part, and so to statistically eliminate the effects of cloud features.

[edstrick]

On Cassin, the VIMS is the best instrument we could design with early 90's mid-infrared imaging technology.

We now have real mid-infrared imaging detectors. Not 10 megapixel, but still real camera chips, that can take quality images with really good resolution in the mid-IR (1 to 5 micrometers, more or less). We just @#$@# didn't back then.

[maycm]

An update....though not much new information.

http://www.spacedaily.com/news/venus-05a.html

[Bob Shaw]

On Cassin, the VIMS is the best instrument we could design with early 90's mid-infrared imaging technology.

We now have real mid-infrared imaging detectors.  Not 10 megapixel, but still real camera chips, that can take quality images with really good resolution in the mid-IR  (1 to 5 micrometers, more or less).  We just @#$@# didn't back then.

Well, obviously we need a Shuttle mission to replace the instrument...

[JRehling]

On Cassin, the VIMS is the best instrument we could design with early 90's mid-infrared imaging technology.

We now have real mid-infrared imaging detectors.  Not 10 megapixel, but still real camera chips, that can take quality images with really good resolution in the mid-IR  (1 to 5 micrometers, more or less).  We just @#$@# didn't back then.

It seems apparent that the 938nm wavelength, which is the best one ISS has to use on Titan, is not the best penetrator of Titan's haze, and that VIMS can thereby make up for (some of) ISS's edge in intrinsic resolution by utilizing better IR wavelengths. Not only by choosing the best possible single wavelength (the best ones are longer than 938nm, at other spectral "holes"), and taking one-wavelength images in that. Surely VIRTIS will beat ISS in that respect. On the other hand, CO2 will block different holes than CH4, and I'm not sure if it leaves us a better hole than CO2 or not.


I think the best IR products of Venus's surface will come from compiling repeated coverage of the same areas and "stacking" or somehow integrating the data to average out over varying cloud thicknesses.

Finally, note that IR is complicated terribly at Venus, but not at Titan, by thermal effects. If all we see is a thermal record of the surface, then we may not get much more than crude altimetry we already knew about. Sorting out the albedo may be impossible.

[Gsnorgathon]

I suppose it's possible, if not easy, to subtract images taken at night from daytime images. "Not easy" might be too much of an understatement.

[JRehling]

I suppose it's possible, if not easy, to subtract images taken at night from daytime images. "Not easy" might be too much of an understatement.

One problem is, can you project an image onto a map accurately? It depends upon whether you are looking at a cloud-level sphere or a surface sphere. And there is undoubtedly refraction. My guess is that you would assume that a cloud level sphere is what you're looking at, assume that when you look at a point in the clouds you are trying to collect albedo data from a diffuse area centered below that point, and use multiple images to integrate observations.

Subtracting night from day -- what does this buy? There will be a lot of thermal interference at both times, but you can't assume that it is precisely the same. You'll get some combination of thermal inertia and albedo -- messy!

When it comes right down to it, trying to observe Venus from above the clouds and learn a lot is pretty tricky. Unless some mineral of interest has a heck of a wicked IR spectrum and that happens to fall inside one of the CO2 windows, I'm just plain skeptical that we'll get good geological data from this mission. Hope I'm wrong.

Surface spectra are, IMO, going to have to come from below the clouds. That still doesn't solve the problem of atmospheric interference, but the fact that the horizons are so clear in Venera imagery provides a lot of cause for optimism. A camera-to-horizon "chord" of 5km will cut through more than or the same as atmospheric interference than a vertical line from surface to clouds (surface air is the densest, and a horizontal chord is entirely through dense air, whereas a vertical slice only goes through the densest air at the bottom). So, with clear images at the surface, I think we can get good images from several km up. A balloon could do the trick.

[TheChemist]

Venus Express arrives in Baikonur

She's got it ..... (Am I allowed to quote Bananarama in a space forum ? )

This post has been edited by TheChemist: Aug 10 2005, 04:35 PM

[Bob Shaw]

Venus Express arrives in Baikonur

She's got it ..... (Am I allowed to quote Bananarama in a space forum ?  )

It ain't what you do, it's the way that you do it!

[Guest_BruceMoomaw_*]

Here's my long-promised entry on whatever I've got regarding VIRTIS' possible ability to map Venusian surface composition.

Unfortunately, the two most important documents on this aren't available for free on the Web: the Nov. 2000 Icarus article by Langevin et al ("Detection of Sub-Micron Radiation from the Surface of Venus by Cassini/VIMS"), and the March 2002 article by V.I. Moroz in "Planetary and Space Science" ("Estimates of Visibility of the Surface of Venus from Descent Probes and Balloons"). I have a photocopy of the former, but can't find the copy I thought I had of the latter. Anyway, the former is optimistic about the possibility: "The 5 spectral windows between 0.85 and 1.18 microns now proven to be sensitive to surface spectral sensitivity provide a potentially effective means for remotely mapping the mineralogical composition of the surface of Venus" [something co-author Kevin Baines was saying for previously]... [They] can be effectively used to distinguish ferric (hematite) and ferrous minerals (e.g., the pyroxenes augite and hypersthene, and olivine). The hydrous mineral tremolite -- thought to be stable on geologic timescales on Venus -- also displays a detectable absorption feature...Both wollastonite -- a CO2 buffer mineral thought to be relating the CO2 surface pressure -- and pyrite are spectrally flat, but have distinctly different ablbedos." There's an accompanying graph of these various minerals' near-IR reflectivities, with the Venusian surface spectral windows overlaying it.

The Moroz article is much more pessimistic: "Constraints on the mineral surface composition would be difficult to derive from orbital observations due to multiple reflections between the surface and the atmosphere." The VIRTIS group itself, the Japanese VCO group and the Vernadsky-Brown Venus group are all intermediate in optimism: they think that it will almost certainly be possible to map FeO, thus distinguishing between felsic and mafic minerals and thus between granites and basalts, and also looking for magnetite on the highly radar-reflective mountaintops -- but aren't sure they can go any farther. (The two longest-wavelength windows seem to be the most useful.) Moreover, it seems much more possible to do this in the north polar regions than elsewhere (which, by an agreeable coincidence, is where Ishtar Terra -- Venus' most likely continent -- is located).

As for spatial resolution (including for temperature and near-surface volcanic gases), estimates are all over the place. Moroz sets it at 50-100 km, the VCO group at 100 km, and David Crisp at no better than 250 km (based on Galileo's flyby results). The VIRTIS group itself initially set it as high as 30 km, but now seems to have it pegged at 90-150 km ( http://irsps.sci.unich.it/~luciam/VEX/DOC/...ence_VIRTIS.pdf and the May 2005 report at the VIRTIS site: http://irsps.sci.unich.it/~luciam/VEX/ ).

As for quake detection through sensing pressure waves in Venus' dense CO2 air, they are still very interested in that -- although it will require special observational techniques (see the Dec. 2003 and May 2005 reports at the VIRTIS site).

[Guest_BruceMoomaw_*]

Two more notes:

(1) The VIRTIS team is fully ready to filter out altitude effects from their maps, using Magellan's altimetry maps (see their May 2005 report).

(2) There's another good paper on the possible detection of Venusquakes through atmospheric pressure waves at http://www.lpi.usra.edu/meetings/lpsc2005/pdf/2274.pdf .

[tedstryk]

http://messenger.jhuapl.edu/the_mission/im...ine_full_sm.jpg

You gotta love the ESA press people.

"Venus Express will be making the first global examination of the atmosphere of Venus."

Pioneer Venus Orbiter? And to some degree the Venera orbiters?



"The scientific teams of the seven very precise instruments and multi-wavelength cameras on board expect to collect infinitely more science data than all previous missions combined - with the exception of Magellan – more than 500 megabits of data received every day."

Yes, it is a lot more than missions besides Magellan, but infinite? I think there is a bit of grandstanding here.

[mike]

America will just have to make a new probe that returns infinitely more data than the infinite amount ESA is getting.

[4th rock from th...]

...

Pioneer Venus Orbiter?  And to some degree the Venera orbiters?

...

Yes, it is a lot more than missions besides Magellan, but infinite?  I think there is a bit of grandstanding here. 

If the PVO data where avaliable on the net this type of statement wouldn't be possible. Someone would gather that data and make some time lapse movies, global maps, etc, etc.

The best I could find is this: http://www.cg.its.tudelft.nl/~freek/venus/...ults/04-07.htmlhttp://www.cg.its.tudelft.nl/~freek/venus/report/last_results/04-07.html
Not much really.

So no wonder that ESA is selling their "product" as best as they can!

[Bob Shaw]

America will just have to make a new probe that returns infinitely more data than the infinite amount ESA is getting.

Mike:

It wouldn't take all that much more!

Oh, and the thing that the ESA Press Office left out is that they'll also be releasing the Venus Express data infinitely s-l-o-w-l-y...

Bob Shaw

[tedstryk]

Well, I doubt there would be time-lapse images. The cloud photopolarimeter built scans slowly like Pioneers 10 and 11, so there wouldn't be many sequences close enough together, and changes in position throughout the scan would be a problem.

[TheChemist]

Oh, and the thing that the ESA Press Office left out is that they'll also be releasing the Venus Express data infinitely s-l-o-w-l-y...

Although "infinitely more" is a very common expression and should not be taken literally. the ESA press office really deserved this

[tedstryk]

 
Although "infinitely more" is a very common expression and should not be taken literally. the ESA press office really deserved this 

Yes, but especially when compared with PVO, even in common usage it doesn't fit (well, maybe in shear bits, but not in the scope of investigations)

[RNeuhaus]

New update. Now it is less than 14 days from launching on October 26 from Baikonour Cosmodrome.

Venus Express ready for 'mating' with upper-stage

* Propellant loading already completed. Two tanks with more than 260 liters capacity.
* Venus already has its wings. Provides 1,100 watts of power. It is made of Gallium Arsenide Triple Junction
* Electrical test completed. Automatic sequence of maneuvers works.

Almost ready for a trip of 153 days toward to Venus for a mission of 500 days in Venus orbit.
Launch mass is 1,270 kg.

Rodolfo

[ljk4-1]

Preparations for ESA's Venus Express mission passed a new milestone when the
spacecraft was attached to its Fregat upper-stage rocket. The mission is now
only two weeks away from launch on 26 October.

More at:

http://www.esa.int/SPECIALS/Venus_Express/SEMTYW5Y3EE_0.html

[RNeuhaus]

The spacecraft Technical details

Spacecraft facts
Spacecraft bus dimensions 1.5 x 1.8 x 1.4 m
Spacecraft mass 1270 kg (including 93 kg of payload and 570 kg fuel)
Thrust of main engine 400 N
Attitude thrusters Two sets of four, each delivering 10 Newtons each
Solar arrays Two triple-junction Ga As;
5.7 square metres; generating 800 Watts
near Earth and 1100 Watts at Venus
Power storage Three lithium-ion batteries
Antennas Two high-gain dishes, HGA1 = 1.3 m diameter,
HGA2 = 0.3 m in diameter, 2 low-gain antennas

Venus Express

The proportion of total weight versus fuel is 44.8% of weight is fuel comparing to the MRO (1,187 kg of fuel hydrazine of 2,180 kg = 54.4% to reduce 1.4 KM/sec during the orbit insertion.) I have not found how the Venus Express will insert into the Venus. At what speed and the what orbit will be traveling VE (Polar, some inclination Equatorial).

The panel solar is very small : 5.7 M^2 versus 10 M^2 of MRO. VE will have about 1,100 Watts and MRO around 1,000 Watts of power when these spacecraft are in their orbits. VE uses Lithium-ion batteries and MRO uses Nickel-hydrogen batteries. What is the difference?

Rodolfo

[um3k]

The panel solar is very small : 5.7 M^2 versus 10 M^2 of MRO. VE will have about 1,100 Watts and MRO around 1,000 Watts of power when these spacecraft are in their orbits. VE uses Lithium-ion batteries and MRO uses Nickel-hydrogen batteries. What is the difference?

Rodolfo

I'm no expert, but I would venture to guess that the cause is the spacecrafts' distances from the sun.

[Rakhir]

The spacecraft Technical details

I have not found how the Venus Express will insert into the Venus.

Rodolfo

From http://esamultimedia.esa.int/docs/VENUSEXPRESSLR.pdf

"In April 2006, it will fire its main engine to slow down and counteract the predominant pull of the Sun and of Venus, to be captured into orbit around the planet. A large velocity change is required for the initial capture manoeuvre, which will require the engine to burn for 53 minutes."

Orbit details -> see page 8 of the pdf

[RNeuhaus]

From http://esamultimedia.esa.int/docs/VENUSEXPRESSLR.pdf

"In April 2006, it will fire its main engine to slow down and counteract the predominant pull of the Sun and of Venus, to be captured into orbit around the planet. A large velocity change is required for the initial capture manoeuvre, which will require the engine to burn for 53 minutes."

Orbit details -> see page 8 of the pdf

Thanks Rakhir, Regrettable, this link needs some kind of authorization.

Forbidden

Your request cannot be serviced due to access restrictions. Please contact your System Administrator for further details

ERROR: your request cannot be serviced

Rodolfo

[tedstryk]

Thanks Rakhir, Regrettable, this link needs some kind of authorization.

Forbidden

Your request cannot be serviced due to access restrictions. Please contact your System Administrator for further details

ERROR: your request cannot be serviced

Rodolfo

Works just fine for me.

[ugordan]

Thanks Rakhir, Regrettable, this link needs some kind of authorization.

Forbidden

Your request cannot be serviced due to access restrictions. Please contact your System Administrator for further details

ERROR: your request cannot be serviced

Rodolfo

I had no problems accessing the pdf just now. Did you try opening the link with a different browser or anything?
I don't know if uploading the document is allowed here due to copyright restrictions?

[RNeuhaus]

The problem was already solved by changing the proxy IP Address.

Thanks,

Rodolfo

[Jeff7]

I'm no expert, but I would venture to guess that the cause is the spacecrafts' distances from the sun.

I think the part in question was the composition of the batteries - lithium ion vs nickel hydrogen.
I know about li-ion, but I don't know a lot about nickel-hydrogen. I think Hubble also uses the latter type.

[helvick]

I think the part in question was the composition of the batteries - lithium ion vs nickel hydrogen.
I know about li-ion, but I don't know a lot about nickel-hydrogen. I think Hubble also uses the latter type.

Li-Ion has better power density but the varous Nickel Hydrogen designs, like the NimH used on some laptops and other consumer electronics kit, has much better charge cycle lifetime. Li-Ion is generally good for up to 1000 charge cycles while there are Ni H designs that are spec'ed out for 30000. NimH batteries also have the benefit of being able to be re-conditioned however I don't know if the process is suitable for use "in flight" with the pressurised NiH type batteries used on spacecraft. Li-Ion degradation is more or less permanent.

There are many other considerations though so the cycling capability is only one possible reason.

[Rakhir]

I'm no expert, but I would venture to guess that the cause is the spacecrafts' distances from the sun.

From the pdf of my previous post : "The sun is twice as strong at Venus as on Earth, so there is plentiful solar radiation to power the spacecraft. VE's solar arrays could therefore be made smaller (almost half the size) than those on Mars Express."

[RNeuhaus]

I think the part in question was the composition of the batteries - lithium ion vs nickel hydrogen.
I know about li-ion, but I don't know a lot about nickel-hydrogen. I think Hubble also uses the latter type.

I didn't mention well in my last post. You posted is what I was asking about this: What are the differences between the two different types of batteries?

Rodolfo

[RNeuhaus]

According to the VE's pdf document, VE has greater challenge to orbit around Venus than Mars Express since it has two great concern that must be adjusted continuously:

1) The thrusters has to adjust to correct the altitude of orbit's pericentre approximately once every day. In fact, due to the gravitational pull of the Sun while the spacecraft is further away from the planet, the pericentre naturally drifts upwards at a rate of about 1.5 kilometres per day.

2) For a spacecraft in orbit around Venus, it is not always possible to point a single
antenna dish at Earth while always keeping the cold face of the spacecraft, hosting
delicate instruments, away from the Sun.To overcome this pointing constraint,Venus
Express has two high-gain antennas mounted on different spacecraft faces.The
main high-gain antenna, used for most of the communications with Earth, is a 1.3
metre-diameter dish.The second, smaller high-gain antenna (30 centimetres
diameter) is used when the spacecraft is in the part of its orbit closest to Earth (less
than 0.78 AU* away).

On the other hand:

I have a doubt about the VE's trajectory to Venus. Will the Soyus-Fraget travel in the opposite way to the Earth's rotation before going to Venus?

I tought it since the Earth position is on the apehelion comparing to the Venus position as perihelion. Hence, the trajectory from Earth to Venus is of inward bound. To launch a spacecraft from Earth to an inner planet such as Venus using least propellant, its existing solar orbit (as it sits on the launch pad) must be adjusted so that it will take it to Venus. In other words, the spacecraft's aphelion is already the distance of Earth's orbit, and the perihelion will be on the orbit of Venus.

This time, the task is to decrease the periapsis (perihelion) of the spacecraft's present solar orbit. A spacecraft's periapsis altitude can be lowered by decreasing the spacecraft's energy at apoapsis. To achieve this, the spacecraft lifts off of the launch pad, rises above Earth's atmosphere, and uses its rocket to accelerate opposite the direction of Earth's revolution around the sun, thereby decreasing its orbital energy while here at apoapsis (aphelion) to the extent that its new orbit will have a perihelion equal to the distance of Venus's orbit. Of course the spacecraft will continue going in the same direction as Earth orbits the sun, but a little slower now. To get to Venus, rather than just to its orbit, again requires that the spacecraft be inserted into its interplanetary trajectory at the correct time so it will arrive at the Venusian orbit when Venus is there. Venus launch opportunities occur about every 19 months.



Will do VE follow the trajectory of least energy orbit as mentioned above?

Rodolfo

[dvandorn]

Your diagram shows the most common Hohmann transfer orbit, achieved by reducing the aphelion to coincide with the orbit of Venus (preferably when Venus itself is occupying that point along its own orbit).

There is another type of Hohmann trajectory for this type of mission. Instead of braking against the Earth's solar orbital velocity, the spacecraft thrusts at right angles to Earth's near-circular orbit (likely directly towards the Sun), creating a lopsided orbit with a perihelion at Venus and an aphelion well outside of Earth's orbit. The good thing is that the average orbital velocity of such an orbit is very nearly the same as the Earth's velocity, so you don't need to brake so much. The bad thing is that it takes even more energy to enter this transfer orbit, and your approach speed at Venus is somewhat higher, requiring more energy to brake you into orbit.

It gets you there a little faster than the brake-against-solar-orbit method, but it takes more energy.

-the other Doug

[Rakhir]

Fairing Installation

Today, Monday 17 October 2005, the payload fairing has been successfully installed on the nose block (composite of Fregat Upper Stage and Venus Express spacecraft). The first part of the activity was the tilting of the nose block from vertical to horizontal position. With both the spacecraft and the Upper Stage being fully fuelled the activity is classified as hazardous, and was hence conducted with the minimum number of personnel present in the clean room.

8 days...

The update including some images of the operation :
http://sci.esa.int/science-e/www/object/in...fobjectid=38153

[RNeuhaus]

New updates about Venus Express. More details about the magnetometer instrument.

http://www.spacedaily.com/news/venus-05g.html

Rodolfo

[Rakhir]

New ESA update : summary of the launch, cruise and arrival phases.

http://www.esa.int/esaCP/SEM0U7R01FE_index_0.html

Rakhir

[Adam]

Delayed:

http://www.esa.int/esaCP/SEM0CV3J2FE_index_0.html

[Rakhir]

Venus Express preliminary investigations bring encouraging news.

"On Monday 24 October the fairing was removed and engineers started the inspection to assess the status of the spacecraft.
The scenario is so far very encouraging, as only fairly large particles, pieces of the insulating material initially covering the launcher’s Fregat upper stage, have been found on the body of the spacecraft.
The ESA Project team is confident that Venus Express will be launched well within the launch window, which closes on 24 November this year."

http://www.esa.int/esaCP/SEM2714J2FE_index_0.html

Rakhir

[SigurRosFan]

Spaceflightnow Mission Status Center: Venus Express

http://spaceflightnow.com/venusexpress/status.html

--- Although a new launch date has not been set, liftoff is expected to be targeted for sometime between November 6 and 9. ---

[Rakhir]

Russian space officials Monday set a Nov. 9 blastoff.

http://www.space.com/missionlaunches/ap_05...usexp_updt.html

Rakhir

[RNeuhaus]

Strange news.

The postpone of the launch was due to contamination problem in the faring. Now, according to the news from space.com :

Russian space officials Monday set a Nov. 9 blastoff for a European probe to explore Venus after its earlier launch was postponed because of a booster rocket problem.

Is it of another story?

Rodolfo

[Rakhir]

Strange news.

The postpone of the launch was due to contamination problem in the faring. Now, according to the news from space.com :

Russian space officials Monday set a Nov. 9 blastoff for a European probe to explore Venus after its earlier launch was postponed because of a booster rocket problem.

Is it of another story?

Rodolfo

By "booster rocket", they are talking about the launch vehicle. The fairing whose thermal insulation contaminated VE is part of the booster rocket.

Rakhir

[Rakhir]

Roll Out to Launch Pad

http://sci.esa.int/science-e/www/object/in...fobjectid=38214

Rakhir

[Rakhir]

Pre-launch sequence was executed.
2 days...

http://sci.esa.int/science-e/www/object/in...fobjectid=38218

Rakhir

[Guest_paulanderson_*]

Interesting article:

'Venus Mission May Hold Surprises For Scientists And Public, Says CU Prof'
http://www.colorado.edu/news/releases/2005/421.html

[mike]

If Venus is almost exactly like Earth, but much hotter, and Mars is quite a lot like Earth, but much cooler, and Venus is closer to the sun than Earth, and Mars is further away from the sun than Earth, then hmm, what could it be I wonder...

I'm looking forward to this mission myself..

[JRehling]

If Venus is almost exactly like Earth, but much hotter, and Mars is quite a lot like Earth, but much cooler, and Venus is closer to the sun than Earth, and Mars is further away from the sun than Earth, then hmm, what could it be I wonder... 

I'm looking forward to this mission myself..

Mars is only about 11% the mass of the Earth, and the bulk composition is quite different, so the differences abound. Given that and other differences that began with formation, I'd say differences should be expected as the rule and similarities seen as more surprising.

Venus has similar mass and bulk composition, but the essential cause-of-it-all difference maker may be the slow rotation. Because of that, no magnetic field. Because of that, the upper atmosphere is pounded by solar wind. Because of that, H2O is broken up and lost. Because of that, CO2 fills the atmosphere AND lighter rock (granite) is not formed. Because of the CO2, the stifling heat. Because of the lack of granite and the heat, entirely different crustal cycling regimes.

It's unclear if that is really the chain of causality, and certainly more exploration is needed, but it would be stirring if such a small matter led to such a huge difference. And it would still be unclear why the rotation is so slow; there is a chicken-and-egg question about whether or not drag in the massive atmosphere may have controlled the rotation rate. The other external factor that may have contributed is the absence of a large satellite.

[RNeuhaus]

Besides, the other intrigating thing is that Venus sluggishly rotates on its axis once every 243 Earth days, while it orbits the Sun every 225 days - its day is longer than its year!

On the other hand, Venus rotates retrograde, or "backwards," spinning in the opposite direction of its orbit around the Sun. From its surface, the Sun would seem to rise in the west and set in the east.

The other odd thing is that its Equatorial Inclination to Orbit is 177.3 degrees. By comparison, it is: 7.56 x Earth. That is its north pole is almost pointing to the south pole.

These are at least one of the oddies things that I would like to understand:

Why does the day is longer than a year?
Why the planet rotates on backwards?

Rodolfo

[ljk4-1]

Besides, the other intrigating thing is that Venus sluggishly rotates on its axis once every 243 Earth days, while it orbits the Sun every 225 days - its day is longer than its year!

On the other hand, Venus rotates retrograde, or "backwards," spinning in the opposite direction of its orbit around the Sun. From its surface, the Sun would seem to rise in the west and set in the east.

The other odd thing is that its Equatorial Inclination to Orbit is 177.3 degrees. By comparison, it is: 7.56 x Earth. That is its north pole is almost pointing to the south pole.

These are at least one of the oddies things that I would like to understand:

Why does the day is longer than a year?
Why the planet rotates on backwards?

Rodolfo

A whomping big celestial impact is my guess.

[RNeuhaus]

A whomping big celestial impact is my guess.

Interesting but...why no a moon. After an impact to Venus and that should have a moon like the Earth's case.

I thought that the Venus' slow rotation might be caused by a very heavy atmosphere that circulates the planet in the opposite side to its rotation.

Or perhaps that is a normal for physics' law since its neigboor planet Mercury rotates around 58 Earth days and orbits around the Sun 88 Earth days. That is more or less a very long day that approach to a "planet of close one year" for both Mercury (less days) and Venus (more days).

Rodolfo

[ljk4-1]

Interesting but...why no a moon. After an impact to Venus and that should have a moon like the Earth's case.

I thought that the Venus' slow rotation might be caused by a very heavy atmosphere that  circulates the planet in the opposite side to its rotation.

Or perhaps that is a normal for physics' law since its neigboor planet Mercury rotates around 58 Earth days and orbits around the Sun 88 Earth days.  That is more or less a very long day that approach to a "planet of close one year" for both Mercury (less days) and Venus (more days).

Rodolfo

Actually, should a large impact create a moon? My guess is that if Venus did get hit by something massive and powerful enough to practically flip it over, slow down its spin rate, and have it rotate in the opposite direction of most other major worlds, Venus was lucky enough to have survived intact, forget having a moon in the outcome.

Or maybe Venus was hit BY its own moon.

[djellison]

Moons tend to orbit their parent planet in the same direction as the planets rotation - so were a moon to colide with its parent planet, the likely impact would be an increase in rotation I'd have thought.

Perhaps it's a symptom of planet formation closer to the centre of the protoplanetary disk - further out from the sun, the local gravity from chunks of whatever is the major force, but closer in, the suns gravity is dominant.

It's a complex process, that's for sure.


Doug

[JRehling]

Actually, should a large impact create a moon?  My guess is that if Venus did get hit by something massive and powerful enough to practically flip it over, slow down its spin rate, and have it rotate in the opposite direction of most other major worlds, Venus was lucky enough to have survived intact, forget having a moon in the outcome.

Or maybe Venus was hit BY its own moon.

There are good sources on the Net for things being wildly speculated about here.

To pick just one: the angular momentum of a planet-moon system would remain the same after an impact as before. Such a collision couldn't make the system go backwards unless it was going backwards in the first place.

For the Moon to be created from a collision, it had to be a glancing blow. A straight-on punch would not liberate a lot of material.

A collision would be necessary if Venus's rotation was set in place as its formation concluded. But there are suggestions that tidal and thermal dynamics of its massive atmosphere may have "set" the rotation at the current rate. If so, the initial rotation is irrelevant/unknowable. In fact, the low inclination suggests that there is some sort of sun-driven factor: a collision that reordered Venus's rotation radically would be unlikely to leave the axis so nearly perpendicular to its orbit -- although that kind of coincidence is not impossible.

The rotation is only one oddity, not two or more. Given that the rotation is so slow, the reversal is not so odd -- the difference between rotating slowly E-W or slowly W-E is not nearly so big a difference as the slow rotation in the first place. Consider that a point on Venus's equator is rotating at about the speed of a fast *walk*!!! If it were moving the other direction, but just as slowly, that would only be a difference of a few km/h.

Also, the relative relationship between the day and year of Venus is not an "extra" oddity. Given the slow rotation, that follows as a logical consequence.

There is a second mystery regarding Venus's rotation, however, and that is why it is [almost] synchronized so as to show [almost] the same face towards the Earth at every conjunction. Mathematically, it would seem impossible for the tidal attraction to make this happen... but if this is a coincidence, it is a remarkable one.

[The Messenger]

There is a second mystery regarding Venus's rotation, however, and that is why it is [almost] synchronized so as to show [almost] the same face towards the Earth at every conjunction. Mathematically, it would seem impossible for the tidal attraction to make this happen... but if this is a coincidence, it is a remarkable one.

I'm filing this gem right next to the thermal energy in the Tiger stripes of Enceladus.

One thing is clear: The Solar System loves to throw us curve balls.

[Guest_BruceMoomaw_*]

Well, as Chesterton said, the most remarkable thing about coincidences is that occasionally they DO occur. The classic one in the Solar System is the disks of the Moon and Sun being virtually the same size as seen from Earth, which is the only thing that makes solar eclipses as we know them possible.

The trouble comes when the fact that the human (and presumably animal) mind is designed to specifically look for patterns leads us to jump to the conclusion that a genuine coincidence is more than that. Arthur Koestler once wrote an infamous crank philosophical book based on precisely that logical fallacy.

[RNeuhaus]

Anyway, at the beginning of the planetary formation, all planets is formed orbiting around the sun in the counter-clockwise, all have the same plane inclination with respect to the sun, all planets has their axis in perpendicular position to the planetary plane and all rotate the same way as it is orbiting around the sun, it is counter-clockwise.

are those all above suppositions affirmative or not?

Rodolfo

[ljk4-1]

There are good sources on the Net for things being wildly speculated about here.

There was this guy a long time ago named Aristarchus who wildly speculated that Earth went around the Sun and that the stars were other suns very far away.

The powers that be of his era accused him of religious impiety. His ideas were effectively buried for 1,500 years.

These ideas may "just" be speculation, but they are not wild. Uranus has been thought by many sober, rational astronomers to be in its present state due to major collisions by natural objects in its past, so why not for Venus to explain its current different state?

[imran]

Less than one hour from launch!

Live webcast should be here:
http://www.starsem.com

[Waspie_Dwarf]

Alternative link for the live webcast of the launch: ESA's Venus Express Site

[jamescanvin]

Less than one hour from launch!

Live webcast should be here:
http://www.starsem.com

Anybody getting a feed from here yet?

Just wondering if the error message I'm getting is because it hasn't starting or if there is an incompatibilty with the OSX version of Media Player.

James

[Waspie_Dwarf]

The live feed won't start until 03:28 GMT, at least on the ESA site. I assume it is the same on the Starsem site.

[jamescanvin]

Alternative link for the live webcast of the launch: ESA's Venus Express Site

Ah, cross posting, a much more useful site.

Starts only 5 mins before launch...

[imran]

Both webcasts are working now although you get better resolution from the Starsem site.

[imran]

0327 GMT (10:27 p.m. EDT Tues.)

The Venus Express flight director in mission control has given the final "go" for launch.

[imran]

0327 GMT (10:27 p.m. EDT Tues.)

The Venus Express flight director in mission control has given the final "go" for launch.

T - 40 seconds!!

[jamescanvin]

Both webcasts are working now although you get better resolution from the Starsem site.

Starsem still doesn't work for me bu thankfully the ESA feed does (thanks Waspie_Dwarf!)

[imran]

Starsem still doesn't work for me bu thankfully the ESA feed does    (thanks Waspie_Dwarf!)

LIFTOFF!!!!

[jamescanvin]

LIFTOFF!!!!

OK through booster sep...

[imran]

0336 GMT (10:36 p.m. EDT Tues.)

T+plus 3 minutes. The first stage strap-on boosters have been jettisoned. The second stage core is still running as planned. All system parameters are reported normal.

[jamescanvin]

OK through booster sep...

Fairing sep, third stage ignition...

[imran]

Cutoff of 3rd stage and separation of nose module.

[jamescanvin]

"Everything is nominal"

Third stage cutoff!

[imran]

Third stage cutoff!

0342 GMT (10:42 p.m. EDT Tues.)

T+plus 9 minutes. The third stage motor has completed its firing and dropped away. The Fregat upper stage now must perform a brief firing to achieve an initial parking orbit around Earth.

[imran]

There goes the feed. Oh well..guess I'll have to rely on the Spaceflightnow updates.

[imran]

0348 GMT (10:48 p.m. EDT Tues.)

T+plus 15 minutes. ESA says the first Fregat burn has been successful. The vehicle is now coasting in Earth orbit for more than an hour before the upper stage is re-started to propel the spacecraft to Venus.

[elakdawalla]

Argh! Is that second Fregat burn happening or not?

[jamescanvin]

Fregat burn should be underway by now.

No word on Spaceflightnow yet...

EDIT: cross posting with you Emily. I feel your pain, I don't know how much more page reloads my computer (and me) can take!

[jamescanvin]

From Spaceflightnow.com

0514 GMT (12:14 a.m. EST)

T+plus 1 hour, 41 minutes. By this point in the flight the Fregat should have completed its burn and then released Venus Express. We're awaiting confirmation from ESA that these events have occurred successfully.

[Bricktop]

From http://sci.esa.int/science-e/www/object/in...fobjectid=38243

Fregat second stage has successfully fired and place Venus Express to an escape trajectory

[Waspie_Dwarf]

From Spaceflightnow.com

0514 GMT (12:14 a.m. EST)

T+plus 1 hour, 41 minutes. By this point in the flight the Fregat should have completed its burn and then released Venus Express. We're awaiting confirmation from ESA that these events have occurred successfully.

In other words Spaceflight Now doesn't know if the Fregat has worked either. The anticipation is killing me.

[Rakhir]

From http://sci.esa.int/science-e/www/object/in...fobjectid=38243

MET: +01h 40m
Fregat second stage has successfully fired and place Venus Express to an escape trajectory

Rakhir

EDIT : You were 1 min quicker than me Bricktop.

[Waspie_Dwarf]

From http://sci.esa.int/science-e/www/object/in...fobjectid=38243

Fregat second stage has successfully fired and place Venus Express to an escape trajectory 

That's put me out of my misery.

[jamescanvin]

Hurrrah!

Venus here we come

[elakdawalla]

This from Daniel Fischer: "Just to report that Venus Express has phoned home exactly on time at 5:30 UTC through ESA's ground station in New Norcia, Western Australia! Everything seems to be going exactly to plan since 2 hours. Now it's about 3 weeks of spacecraft and instrument checkout; perhaps some nice pictures of Earth will be taken during that period (as ESA's Gerhard Schwehm just told me). Then it's quiet cruising (no science on the way), until Venus Orbit Insertion on April 11, 2006."

[JRehling]

There was this guy a long time ago named Aristarchus who wildly speculated that Earth went around the Sun and that the stars were other suns very far away.

The powers that be of his era accused him of religious impiety.  His ideas were effectively buried for 1,500 years.

These ideas may "just" be speculation, but they are not wild.  Uranus has been thought by many sober, rational astronomers to be in its present state due to major collisions by natural objects in its past, so why not for Venus to explain its current different state?

What I meant was, sometimes the answer is in the FAQ.

[Rakhir]

MET: +02h 40m
Sun acquisiton and successfully deployment of solar arrays confirmed

http://sci.esa.int/science-e/www/object/in...fobjectid=38243

Rakhir

[Decepticon]

Venus Orbit Insertion on April 11, 2006."

And Public won't see any data till August.


Ya ya I know I'm bad.

[edstrick]

"Sun acquisiton and successfully deployment of solar arrays confirmed "

------------------ YEEEEHAAWWWWWW! ------------------------------------

Chances of "Loss-of-Mission" have dropped by some 85%