I've been fiddling with Venera radar data. These two mapping orbiters have been somewhat forgotten, after the dramatic results form Magellan, but they were very important. For six years, they were the only really good images of the surface of Venus, studied by the experts in Russia and America. Most of the major ideas about Venusian surface geomorphology comes from this data - coronae, lack of tectonic activity, the low meteorite crator count and relative youth of the surface, etc.

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The SAR data is high frequency only, because of the use of automatic gain control. But the altimetry data can be used to create a nice hill-shaded low-frequency component. The raw data is in various conformal projections, but very precisely registered. Thank god! It turned out to be easy to combine all of it into one spherical map with no seams.

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Here are the orbits of all Venus satellites (except Venus Express). The two darker orbits are Magellan (the smaller one) and Pioneer Venus (at one point in time). The two extremely eccentric orbits are Venera-9 and 10, placed in molniya orbits to "hover" over the Venera landers while relaying their data. The two Venera radar mappers are in 24 hour orbits. They made a close pass over the north pole, recording radar holograms, and then replay the results to Earth during the rest of the orbit.

The Venera radar data got widely ignored in the west, partially because there was a lot of striping and cross-strip brightness "ripple" in the data that made it rather ugly, partly because of Soviet PR that made ESA's look brilliant, and mostly because the western mass media didn't care.

But the Venera data were really the first data that permitted true geologic analysis and mapping on Venus. Venera and Magellin are rather like Mariner 9 and Viking orbiter. The later coverage was far better (and the Venera data weren't global), but the earlier mission was the one that really let us see the essentials of what was there.

Don:

Nice map! It's much easier to get a grasp of than most of the other ones out there - I hope you pursue this further.

And as for the Venera-9 and 10 Molniya orbits, I hadn't realised that before. The Soviets really had come a long way as compared to their Mars orbital insertion attempts, but they always were particularly creative about such things!

Bob Shaw

Yeah, they didn't always do as neat a job of feathering the individual strips. But the data was no ignored by the scientific community. The Venera and Magellan teams overlapped quite a bit, as the Russians invited Jim Head and Campbell and others to participate in the Venera mission, and shared the data with them. When Magellan was launched, we reciprocated and Bazilevsky and other Russians were PI's on that mission. An excellent example of international cooperation. There is a perminant Brown-Vernadsky symposium on Planetology now, which is one of the major scientific forums in that field.

There was also delay-doppler imaging from Earht, which had good resolution in theory, but failed to show geological formation for various reasons. Arecebo and the crude radar images from Pioneer Venus mislead people into thinking the corona volcanic structures were meteor impact crators.

Here's a piece of full-resolution data from Venera, taken from the same quad seen above, just the SAR image:

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Great Thread!

Looking forward to more images.

I did a search on Info related of Verera radar mapping. Came up with this. I'm surprised how much resolution we got from earth alone.

http://carnap.umd.edu/phil250/venus_alive_...pter7/CH7-0.pdf


Please note the continue button at the bottom of the PDF file.

Here are a couple full-resolution delay-doppler images of the same area of Venus shown in the Venera image--the volcano cauldera of Colette Patera on Ishtar Terra. These Arecibo images, made in 1983 and 1988, look good at low resolution, but when you really try to look closely at things, the quality is very poor. The Venera images were vastly more useful for studying the geology of Venus.

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Oh and just to be complete, here is Magellan's view, about 10x the resolution of Venera.

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I've been tinkering with this data too, and also the altimeter data. The orbital data that comes with Magellan products is way off, so you cannot make good pictures with the altimetry. I managed to eventually lay my hands on a revised spacecraft ephemeris, which fixed that right up.

One of my someday projects is to make a better map of Venus, now that I have all the data laying around. I've never been happy with the puke-colored NASA images. Ralph Aeschliman had made some beautiful hypsometric maps of Venus, google around for them.

One reason they didn't get all that much publicity was that -- after their images had started to come in -- the Soviet military establishment suddenly got cold feet about allowing them to be released because they might provide the West with information on the maximum capabilities of Soviet military radar. They sat on the images for months.

I never thought of this before, but maybe this sudden switch in policy after the Brezhnev government had funded the missions had something to do with his replacement by Andropov, who was apparently downright paranoid toward the West -- he came chillingly close to launching a nuclear first strike in Nov. 1983 in response to a normal NATO military exercise. (His "cold" was probably the single most beneficial illness in human history.)

The Radar system in Venera-15 and 16 was essentially the same as a military surveillance system on the Almaz-T satellite. I don't know about delays, but in the six years before Magellan, the scientific community had ready access to the Venera radar data. It was the primary data set for Venusian geologists.

I believe the Andropov crisis was about a first-strike weapons system deployment, not just a NATO exercise.

IIRC, the Venera data is still the only surface imagery we have for Magellan's "blind spots" on the surface.

Yep. I've been putting together a map of Venus, and Venera data is the second most important source. The Arecibo images help some in the southern hemisphere, but there are still some big gaps down there. Maybe some cloud-penetrating IR images from Venus Express will give some clues there, although its orbit is optimized for studying the north.