Venus Science Options

[ljk4-1]

Sunspot, NM (Feb. 7, 2006) -- The planet Venus is best known for the thick layers of clouds that veil its surface from view by telescopes on Earth. But the veil has holes, and a New Mexico State University scientist plans on using a solar telescope to peer through them to study the weather on Venus.

"Observations of Venus from a nighttime telescope at a single location are very difficult because Venus is so close to the Sun in the sky," said Dr. Nancy Chanover, a planetary scientist at NMSU in Las Cruces, NM. "You can observe it for about two hours at most." Then the Sun rises and blinds the telescope (or Venus sets, depending on the time of year).

http://www.nso.edu/press/venus06/

[ljk4-1]

"VENUS' CLIMATE IS TELLING US THAT WE REALLY DON'T UNDERSTAND THE EARTH"

The Observer, 9 April 2006

Venus: the hot spot

This week a European spacecraft will arrive for a date with Venus, our closest
planetary neighbour. Scientists hope the mission, made on a shoestring budget,
will reveal vital lessons on how unchecked greenhouse gases can turn a world
into a blistering Hades. Robin McKie reports on a journey to the Forgotten
Planet

On Tuesday morning, mission controllers in the European Space Agency's
operations centre in Darmstadt will put the finishing touches to an
international bid to study the ultimate neighbour from hell.

They will transmit a series of radio commands to a robot spacecraft currently
hurtling towards the Sun. Its rocket engine will fire for 50 minutes as it
passes Venus, slowing the craft down so that it can be captured by the planet's
gravitational field. Once in orbit, the wardrobe-sized probe - Venus Express -
will then study the planet's acid clouds, searing heat, crushingly dense
atmosphere and hurricanes to find out why Earth's nearest neighbour has become a
place of insufferable heat and poison.

'Venus is very like Earth in that it is the same size and has an orbit round the
Sun close to ours,' said David Southwood, head of science at the ESA. 'Yet Venus
went wrong. We did not. We want to find out why Venus became our evil twin.'

Venus and Earth are almost identical in size. In addition, both orbit the Sun in
'the Goldilocks zone', a swath of space in which conditions are considered by
astronomers as being not too hot and not too cold to prevent the evolution of
life. Venus should make ideal planetary real estate, in other words. Yet it is
the solar system's most inhospitable planet.

'It's very disturbing that we do not understand the climate on a planet that is
so much like the Earth,' said Professor Fred Taylor, a planetary scientist based
at Oxford University and one of the ESA's chief advisers for the Venus Express
mission. 'It is telling us that we really don't understand the Earth. We have
ended up with a lot of mysteries.'

Full article here:

http://observer.guardian.co.uk/uk_news/sto...1750001,00.html

[Julius]

Unnecessary quote removed - moderator

My biggest query about Venus is that despite the lack of magnetic field and hence complete exposure to atmospheric erosion by the solar wind,Venus has managed to retain a thick atmosphere.Could this be indirect evidence for continued volcanic activity on the planet??!!

[ljk4-1]

My biggest query about Venus is that despite the lack of magnetic field and hence complete exposure to atmospheric erosion by the solar wind,Venus has managed to retain a thick atmosphere.Could this be indirect evidence for continued volcanic activity on the planet??!!

Not long after Pioneer 12 (aka, Pioneer Venus Orbiter) arrived at the
Cloudy Planet in late 1978, it detected a recent drop in the amount of
sulfur dioxide in the planet's thick atmosphere, which was interpreted
as the result of volcanic activity.

Examining various radar images, especially from Magellan, has anyone
ever seen any flow patterns or other changes that might have indicted an
active volcano or two?

[Guest_DonPMitchell_*]

A few comments on the Russian probes:

Venera-1 - the temperature control system did not fail, but photosensitive element in the precision solar sensor overheated. It automatically put itself into a backup mode of spin stabilization, but contact was lost after the third telemetry session.

They made an attempt to send a Mars-1 style photo-flyby in 1962, and two attempts to send a Zond-3 style probe in 1965. Two failed to leave parking orbit, Venera-2 lost communication just before it was to relay all of its recorded data, including the photos. It may have actually performed its mission objectives, we will never know.

Mars-1 - a faulty valve caused a slow leak of its attitude control nitrogen. Before loss of control, it was placed in a backup mode of spin stabilization, and space science was performed for about half its flight, until contact was lost. If I was going to guess, I'd say it wobbled out of alighnment or the Earth just passed out of the funnel-shaped radiation pattern of its semi-directional antennas.

Zond-1 lost internal pressurization. From attitude pertubations, Soviets calculated that the window of its astronavigation sensor cracked. The ground crew then made a fatel mistake -- they switched on the radio transmitter before the craft was completely evaculated, and corona discharges destroyed the radio in the main bus. A back-up system switched over the main antenna to the transmitter in its landing capsule, and it continued for quite some time after that. Several midcourse corrections were performed, space science data was returned, but they lost contact before it reached Venus. In theory, it could have achieved its primary objective (landing) if they had not lost contact.

Zond-2 a photoflyby, not a lander. Its solar panels only half deployed, and lack of power ruined the mission. Zond-2, Zond-3 and Venera-2 were essentially identical spacecrafts.

[Guest_DonPMitchell_*]

A couple comments on Mariner -2 and -5

I think it was a good call that NASA put the radio occultation experiment on Mariner-5. That ended up being the key experiment that mattered. In particular, it gave an important sanity check to the Venera-4 results about the depth of the atmosphere. Due to altimeter ambiguity, it was believed at first that Venera-4 had landed, and nobody would have disputed that without the occultation data. I think this was more valuable than noisy 256x256 television pictures, which probably wouldn't have shown much.

There is a nice little book about the Mariner-2 mission published by JPL (Mariner: Mission to Venus), and lots of scuttlebutt about it. Mariner-2 just barely made it to Venus, and the inside joke then was that JPL stood for "Just Plain Lucky".

Mariner-2 was a refurbished Ranger probe, a notoriously unreliable spacecraft. It's ironic that one of them made it to Venus two years before the first one succeeded in a lunar mission. The failure of about a dozen Lunar probes by that time was the cause of a congressional investigation and management shake-ups at NASA. Of course, the Russians had similar probems, and Korolev was called on the carpet at the Kremlin about the same time. They had a series of failures in their even more ambitious program to soft land on the Moon (Luna-4 to 8).

Politicians and the public just didn't undestand how difficult and fundamentally new all of this work was.

By the time Mariner-2 reached Venus, the temperature of its body was unknown because it had exceeded the range of its sensors. Somewhere in excess of 100 C. The radiometer was so hot (60 C) that it almost couldn't function. One of its two solar panels had failed, its astro-navigation sensor was going blind and was only at a few percent of signal by then, etc. Yup, just plain lucky! But nevertheless a milestone in space history.

[Guest_BruceMoomaw_*]

A couple comments on Mariner -2 and -5

I think it was a good call that NASA put the radio occultation experiment on Mariner-5. That ended up being the key experiment that mattered. In particular, it gave an important sanity check to the Venera-4 results about the depth of the atmosphere. Due to altimeter ambiguity, it was believed at first that Venera-4 had landed, and nobody would have disputed that without the occultation data. I think this was more valuable than noisy 256x256 television pictures, which probably wouldn't have shown much.

There is a nice little book about the Mariner-2 mission published by JPL (Mariner: Mission to Venus), and lots of scuttlebutt about it. Mariner-2 just barely made it to Venus, and the inside joke then was that JPL stood for "Just Plain Lucky".

Mariner-2 was a refurbished Ranger probe, a notoriously unreliable spacecraft. It's ironic that one of them made it to Venus two years before the first one succeeded in a lunar mission. The failure of about a dozen Lunar probes by that time was the cause of a congressional investigation and management shake-ups at NASA. Of course, the Russians had similar probems, and Korolev was called on the carpet at the Kremlin about the same time. They had a series of failures in their even more ambitious program to soft land on the Moon (Luna-4 to 8).

Politicians and the public just didn't understand how difficult and fundamentally new all of this work was.

By the time Mariner-2 reached Venus, the temperature of its body was unknown because it had exceeded the range of its sensors. Somewhere in excess of 100 C. The radiometer was so hot (60 C) that it almost couldn't function. One of its two solar panels had failed, its astro-navigation sensor was going blind and was only at a few percent of signal by then, etc. Yup, just plain lucky! But nevertheless a milestone in space history.

The main occultation experiment on Mariner 5 (the S-band occultation) was never in any danger of getting the boot -- it was, in fact, officially rated by JPL as the single most important experiment on the mission. The fight was over whether to fly a second occultation experiment -- the Twin-Frequency Radio Propagation experiment, which operated on two additional frequencies and used earth-to-Mariner transmissions rather than vice versa -- or the TV camera (with one visible and one UV filter). JPL recommended the camera; NASA HQ overrode them. The fight over that, believe it or not, is still going on; Bruce Murray, in his 1977 book "Flight to Mercury", denounces the choice on the grounds that the second occultation experiment (which focused mainly on ionospheric structure) didn't tell us that much more, while some writer in a 1980s "Icarus" article that I once saw praises it.

Apparently the plan for the TV was to get entirely closeup photos of Venus, rather than long-distance photos that would have revealed good details about its overall cloud patterns. This seems puzzling at first -- but I actually have a copy of the document in which JPL made its payload recommendations, and it makes it fairly clear that they were hoping for chinks in the clouds through which Mariner 5 just might be able to see Venus' surface directly.

As for Mariner 2 being lucky: damn straight. It was a Perils of Pauline mission of a sort we didn't see again among planetary probes until the downright embarrassing flight of Mariner 10. I've always marveled that the US got a successful probe to Venus -- 150 times farther away -- 19 months before it got one to the Moon. Any SF writer who had stated that as a possibility would have been laughed out of business. Keep in mind, though, that all 8 of the first US lunar probe failures -- the Pioneers -- were pure booster failures, and in some cases remarkable episodes of bad luck with rocket stages that, by that time, were usually working right. It wasn't until Ranger 3 that US lunar spacecraft themselves started breaking down in ways that roused Congress' ire against JPL.

Finally: we've had quite a detailed discussion of the Soviet 1963-66 lunar landers down in (of all places) the "I'm back from the Europa Focus group meeting" thread in the "Europa" section (which should give you some idea of how disciplined this group is). The Journal of the British Interplanetary Society has, in recent years, had at least two splendidly detailed long pieces on the 1958-60 and 1963-68 Soviet lunar probes; I'll have to check out what else they have in their periodic special issues on the history of Soviet astronautics. You're certainly right that the Soviets were losing even more missions than the US was early on, and they continued doing so at a much higher rate than us later -- while managing to conceal most of their launch failures. Being a tyranny means never having to say you're sorry...

[ljk4-1]

Apparently the plan for the TV was to get entirely closeup photos of Venus, rather than long-distance photos that would have revealed good details about its overall cloud patterns. This seems puzzling at first -- but I actually have a copy of the document in which JPL made its payload recommendations, and it makes it fairly clear that they were hoping for chinks in the clouds through which Mariner 5 just might be able to see Venus' surface directly.

The same thinking they had with Voyager 1 and Titan.

Well, we did discover that the Titanian clouds were really orange, even
up close.

They made an attempt to send a Mars-1 style photo-flyby in 1962, and two attempts to send a Zond-3 style probe in 1965. Two failed to leave parking orbit, Venera-2 lost communication just before it was to relay all of its recorded data, including the photos. It may have actually performed its mission objectives, we will never know.

Crazy Idea of the Day: If a mission could be sent to find Venera 2 and
attempt to recover its recorded data, would it still be readable?

[ugordan]

The same thinking they had with Voyager 1 and Titan.

Well, we did discover that the Titanian clouds were really orange, even
up close.

Correct me if I'm wrong, but the scientists weren't expecting a global cloud/haze cover on Titan. All that was previously known about Titan's atmosphere was it contained methane, even methane's partial pressure was known. The major constituent - nitrogen probably escaped ground detection. I don't know whether complex hidrocarbons were detected via spectroscopy, but the overall expectations were probably of an optically thin atmosphere.