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Venus Science
ljk4-1
post Feb 10 2006, 10:18 PM
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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/


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I see that such intercourse long continued would make one thoroughly prosaic, hard,
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not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Guest_PhilCo126_*
post Feb 11 2006, 04:02 PM
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Well on the subject of ' early ' missions to the planet Venus, I was always amazed that the first unmanned spacecraft didn't carry a camera to make photos of our 'sisterplanet' ... as if the engineers & scientists of the Venera program weren't interested in good photos of the cloud tops ?
huh.gif
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tedstryk
post Feb 11 2006, 04:47 PM
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QUOTE (PhilCo126 @ Feb 11 2006, 04:02 PM)
Well on the subject of ' early ' missions to the planet Venus, I was always amazed that the first unmanned spacecraft didn't carry a camera to make photos of our 'sisterplanet' ... as if the engineers & scientists of the Venera program weren't interested in good photos of the cloud tops ?
huh.gif
*

Well, as for the first successful mission, Mariner-2, I think it was simply not possible for a mission of its size at the time. But the fact that Mariner-5's camera was removed is stranger. As well as, as you mentioned, the avoidance of using them on the Veneras. My guess is that since Venus was featureless from Earth, they reasoned that, given the crude electronic imaging of the 1960s, the images would be embarassingly blank.


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Phil Stooke
post Feb 11 2006, 05:25 PM
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Ted said "My guess is that since Venus was featureless from Earth, they reasoned that, given the crude electronic imaging of the 1960s, the images would be embarassingly blank."

I think he's right. Also, there was still in those days a strong bias against imaging from the 'sky scientists' (see Don Wilhelms' great book 'To a Rocky Moon'). Why transmit a million bytes for one fuzzy image when a thousand measurements of the magnetic field, plasma and particles would tell you so much more? People had to fight to fly cameras. That seems strange to us now, but we are talking about a period when the value of images for geological study had not been fully demonstrated - Shoemaker and others at USGS were doing it, but the work was still not fully accepted outside their group.

Phil


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tedstryk
post Feb 11 2006, 05:46 PM
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QUOTE (Phil Stooke @ Feb 11 2006, 05:25 PM)
Ted said "My guess is that since Venus was featureless from Earth, they reasoned that, given the crude electronic imaging of the 1960s, the images would be embarassingly blank."

I think he's right.  Also, there was still in those days a strong bias against imaging from the 'sky scientists' (see Don Wilhelms' great book 'To a Rocky Moon').  Why transmit a million bytes for one fuzzy image when a thousand measurements of the magnetic field, plasma and particles would tell you so much more?  People had to fight to fly cameras.  That seems strange to us now, but we are talking about a period when the value of images for geological study had not been fully demonstrated - Shoemaker and others at USGS were doing it, but the work was still not fully accepted outside their group.

Phil
*


On the scientist end, this is definitely a factor. With moon and Mars missions, such as Luna-3 and Mariner-4, the propaganda factor of having images no doubt tilted the tables, but for Venus, the prospect of images that wouldn't be cause for bragging rights allowed the "sky scientist" faction to dominate.


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Guest_BruceMoomaw_*
post Feb 12 2006, 06:40 AM
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In the case of Mariner 1 & 2, there was never any question of it -- it was necessary to reduce the spacecraft's mass, and therfore its complexity, to an absolute minimum for the Atlas-Agena B to launch it to Venus at all. But even the earlier 500-kg Mariner A -- which carried a tape recorder and was originally planned for launch to Venus in 1962 by Atlas-Centaur, before it became excruciatingly clear in mid-1961 that the extremely troubled Centaur wouldn't be ready by then -- carried a multichannel microwave radiometer and a UV spectrometer, but no camera. It was simply not felt to be justified for Venus precisely because, while we'd known about the existence of the UV cloud patterns since about 1910 (!), they were not adequate justification scientifically for something as complex and data-hungry as a camera. If a third instrument had been added to Mariner A, it would certainly have been an IR spectrometer for more atmospheric composition and temperature data.

The Mariner 5 story is stranger. It was added to NASA's schedule on very short notice in December 1965 (along with the 1969 Centaur-launched Mars Mariners) after it became painfully clear that otherwise there would be no planetary probes at all between 1964 and 1973 (to which the gargantuan "Voyager" Mars landers had been delayed by then). But that very short notice for a mission which consisted of hastily reworking the backup third 1964 Mars Mariner spacecraft meant that they simply did not have time to develop and test many of the new experiments they would otherwise have put on it (UV and IR spectrometers and/or an improved microwave radiometer). Further budget cuts also meant that they had to quickly remove half of the 1964 Mariners' particle and field instruments, and cancel an Earth occultation photometer that could have measured cloud-top altitude. In fact, from the start, its top science goal was listed as determining Venus' surface air pressure (since Mariner 2 was thought to have nailed down its high surface temperature firmly, despite a few scientific dissenters) -- and so its top-priority science experiment was S-band radio occultation, which had been added to the 1964 Mariners as an afterthought!

But JPL neverthless recommended retaining the TV camera, with the red and green color filters replaced by one UV and one visible filter. The reason was that there was still some hope then that there might be gaps in the clouds that might allow the craft to get a glimpse of the surface -- plus the fact that it was fairly easy to retain the already-existing instrument and there was always a chance that it might make some useful observations on cloud patterns. However, NASA HQ overrode JPL and ordered the camera replaced by Stanford's dual-frequency radio occultation experiment (an improved version of the one on Pioneer 6), which was power-hungry enough that it and the camera could not both be flown, and which could both double-check the S-band experiment and obtain some additional data on ionospheric structure.

This is STILL the subject of dispute among scientists -- Bruce Murray, in his 1977 book on Mariner 10, bemoans the fact that the camera wasn't carried, but an article I saw in "Icarus" some time in the 1980s defends the decision. The one thing that puzzles me is that, had the camera been flown, its photos would apparently have been taken at close range like those on Mariner 4 -- although one would think that more distant whole-disk photos of Venus' cloud patterns would have been better. Some engineering reason, I suppose.

And of course we have the Soviets' Venera 2, which (like Venera 3 with its entry probe) came very close to successfully reaching Venus in early 1966, with a scanned-film camera system. I imagine this was an attempt to recycle one of the spacecraft the Soviets had planned to launch to Mars in 1964 along with Zond 2, and cancelled after that craft suffered a failure of one of its solar panels to deploy. (Zond 3, which successfully obtained the second set of lunar farside photos in 1965, was also obviously a recycled 1964 Mars craft -- its other instruments included IR and UV spectrometers which had little use for the Moon, but which were copies of the ones carried along with a camera on the 1962 Mars 1 probe. And it repeatedly replayed the lunar photos from distances up to several tens of millions of km, as an engineering test. There is, however, apparently still dispute as to whether Zond 2 itself was another flyby craft or an actual attempt to land a small parachute-equipped lander on Mars -- which would, of course, have crashed.)
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edstrick
post Feb 12 2006, 08:36 AM
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I'd have to dig in "the stacks", but I think I have a copy of a brief note from around 1965 or so, discussiong planetary quarentine stuff, maybe in Science, not sure, maybe by Bruce Murray and others, analysing the launch-trajectory info for Mars 2 and concluding it was a probably a landing attempt, given a minimal arrival velocity trajectory or something like that.
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Guest_BruceMoomaw_*
post Feb 12 2006, 08:52 AM
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I remember that -- it was indeed a letter in "Science", although I don't remember the date. (I think you can find it in the Reader's Guide to Periodical Literature.) There was a longer article on the subject in "Spaceflight" around 1990, but I haven't heard anything more on the subject since then. You'd think the official answer would be available somewhere by now.
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ljk4-1
post Feb 13 2006, 06:43 AM
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Andrew Lepage wrote about Zond 2 in the April, 1991 issue of the EJASA.
His conclusion was that the probe did have a landing capsule, but that the Soviets
assumed Mars had a thicker atmosphere than it did, so that even if Zond 2 did
release its lander, the craft would have likely crashed on the Martian surface.

The issue and article can be found here:

ftp://ftp.seds.org/pub/info/newsletters/e...91/jasa9104.txt

Regarding Mariner 5, Jane's Solar System Log by Andrew Wilson (1987) stated that the
flyby Venus probe was considered for carrying a small landing capsule, but the idea was
rejected.

Any idea what this Mariner 5 Venus lander would have looked like? What instruments it could
have carried? Could they have developed it in time? Would it have been more or less advanced
than the early Venera landers of 1966-1972? Any drawings of it available? Did they expect it
to survive to the surface, or just hope to get atmospheric readings before being crushed?

A Summary Review of the Scientific Findings of the Mariner 2 Venus Mission

http://ntrs.nasa.gov/archive/nasa/casi.ntr..._1964016602.pdf

Mariner-Venus 1967

http://ntrs.nasa.gov/archive/nasa/casi.ntr..._1972013159.pdf


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Guest_BruceMoomaw_*
post Feb 13 2006, 09:16 AM
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QUOTE (ljk4-1 @ Feb 13 2006, 06:43 AM) *
Regarding Mariner 5, Jane's Solar System Log by Andrew Wilson (1987) stated that the
flyby Venus probe was considered for carrying a small landing capsule, but the idea was
rejected.

Any idea what this Mariner 5 Venus lander would have looked like? What instruments it could
have carried? Could they have developed it in time? Would it have been more or less advanced
than the early Venera landers of 1966-1972? Any drawings of it available? Did they expect it
to survive to the surface, or just hope to get atmospheric readings before being crushed?


That I can firmly answer: it would have made temperature and pressure measurements all the way to the surface before crashing -- period -- and, had it been flown, it would have forced elimination of all other science experiments on the mission. NASA nevertheless did briefly but seriously consider it before quickly deciding that it could not be developed in time.


One additional note: until the Soviets pulled off the Venera 4 landing, NASA was leaning toward flying a single April 1972 Mariner Venus mission that would have flown by and released an entry probe, which would have carried a mass spectrometer and some of the other basic weather sensors. The flyby craft had a number of alternative instruments considered for it, including a camera and a high-resolution microwave radiometer to do some altitude mapping of the surface (although, oddly, radar altimetry doesn't seem to have been considered in the preliminary design). After Venera 4, this mission was dumped as too redundant -- although, even given a mass spectrometer cruder and less sensitive than the one on Pioneer 13, it seems to me that it would have gotten a lot of important new data. Maybe the assumption was that, by then, the Soviets would already have flown an entry probe with a mass spec. If so, NASA overestimated them.
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edstrick
post Feb 13 2006, 10:15 AM
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Something in my infinitely long list of "would love to do" is create a version of the "image" of Venus that Mariner 2 took.

Yes. I know Mariner 2 didn't carry an imaging system.

Not entirely true.

Both the microwave radiometer and infrared radiometers were mounted on a scan platform. Each had 2 channels: 2 different wavelengths.

(going from memory) The design was for the platform to scan back and forth at a high slew rate till the brighness temperature sensed by the microwave radiometer got above a threshold, then scan back and forth in a zig-zag slow scan pattern, reversing direction every time the signal dropped below a threshold. This would have generated a 4 crude zig-zag raster scanned images of Venus' disk: 2 microwave, 2 IR.

During launch, the microwave radiometer was probably damaged -- some of it's thermal shielding may have been disturbed. Output signal was lower than designed and the second channel's data was actually reversed! When scanning past a calibration "warm plate" on the edge of the scan range it put out a LOWER signal than when pointed at black space! As a result, the instrument couldn't do the fast "search" scans it was designed to do.

During the encounter, which was at about twice the nominal pre-launch distance (they didn't take the risk of a second midcourse just to get closer than the acceptable result of the first), they got 3 slow rate scans across the planet's disk, one by accident when the scan got confused by the reversed signal, sped up, hit the end of the stop and reversed direction. There were about 15 total microwave measurements (and IR) on the limb and disk of the planet and they could be turned into very crude "sparse" images.

The microwave channels basically showed limb darkening caused by the atmosphere attenuating the heat from the surface. The IR (one in a CO2 window) both showed cloud top temperatures with no breaks in the cloud, one measurement apparently hit the cold polar collar and was lower than expected for it's emission angle.
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Gsnorgathon
post Feb 13 2006, 05:38 PM
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QUOTE (ljk4-1 @ Feb 13 2006, 06:43 AM) *
Andrew Lepage wrote about Zond 2 in the April, 1991 issue of the EJASA.
His conclusion was that the probe did have a landing capsule, but that the Soviets assumed Mars had a thicker atmosphere than it did, so that even if Zond 2 did release its lander, the craft would have likely crashed on the Martian surface.

The issue and article can be found here:

ftp://ftp.seds.org/pub/info/newsletters/e...91/jasa9104.txt

<snip>


Oh dear - this is off-topic for this thread, but I can't help but note that the EJASA article makes an interesting assertion I've never heard before:

QUOTE
Because of problems with the radio relay on the MARS 3 main bus, which had just slipped into orbit around Mars, the lander's signal was lost after only twenty seconds and was never heard from again.
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Bob Shaw
post Feb 13 2006, 06:50 PM
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QUOTE (Gsnorgathon @ Feb 13 2006, 05:38 PM) *
Oh dear - this is off-topic for this thread, but I can't help but note that the EJASA article makes an interesting assertion I've never heard before:


Wrong planet, same spacecraft family, so not *too* off-topic - and an interesting article. The assertion that it was an orbiter failure that did in Mars 3 is entirely fresh so far as I can see...

Bob Shaw


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ljk4-1
post Feb 13 2006, 07:38 PM
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QUOTE (Bob Shaw @ Feb 13 2006, 01:50 PM) *
Wrong planet, same spacecraft family, so not *too* off-topic - and an interesting article. The assertion that it was an orbiter failure that did in Mars 3 is entirely fresh so far as I can see...

Bob Shaw


It was also mentioned in the October, 1989 EJASA from a Soviet source:

http://www.seds.org/pub/info/newsletters/e...89/jasa8910.txt

And in a revised version of the same article in Spaceflight magazine in the
August, 1990 issue (does the BIS have any articles online?).

The Soviets always preferred to blame nature as the cause for space probe
failures, rather than the Glorious Socialist Technology of the Workers Party.
They did the same for Mars 1 and Venera 1, both of which stopped transmitting
before reaching their target worlds (and they were hardly isolated events),
because they were apparently struck by those darn meteoroids zipping
around the Cosmos, rather than failures of their communications technology.


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Bob Shaw
post Feb 13 2006, 09:00 PM
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QUOTE (ljk4-1 @ Feb 13 2006, 07:38 PM) *
It was also mentioned in the October, 1989 EJASA from a Soviet source:

http://www.seds.org/pub/info/newsletters/e...89/jasa8910.txt

And in a revised version of the same article in Spaceflight magazine in the
August, 1990 issue (does the BIS have any articles online?).

The Soviets always preferred to blame nature as the cause for space probe
failures, rather than the Glorious Socialist Technology of the Workers Party.
They did the same for Mars 1 and Venera 1, both of which stopped transmitting
before reaching their target worlds (and they were hardly isolated events),
because they were apparently struck by those darn meteoroids zipping
around the Cosmos, rather than failures of their communications technology.


I don't suppose you know who wrote the article to which you refer?

And the article actually refers to the matter of the supposed telemetry failure being a conclusion reached by western analysts...

Oh, go on. Go on, go on, go on.

Bob Shaw


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