[X] My Assistant

[Guest_DonPMitchell_*]

Mariner-9 was a turning point for American probes, I've always thought. I'd argue it was the point at which the US surpassed the Soviet's in the sophistication of planetary probes. We still couldn't send an 8-ton probe to Mars like they could, but our electronics and camera technology was advanced enough that we could do more with a lot less.

[nprev]

Couldn't agree more. Mariner 9 clearly established UMSF as the preferred method of planetary exploration by virtue of its results and its durability.

More speculation: What if all the Soviet Mars probes had worked? They were of course desperate for them to do so, both scientifically and for symbolic purposes (the red planet, after all). Do you think that they would have become more aggressive in both manned and UMSF? What would the US have done in response?

[Guest_DonPMitchell_*]

James Burke wrote that they kept a picture of Venera-1 on the wall at JPL, to remind them that the Russians were ahead. They were well aware that Mariner-2 was a huge stroke of good luck, with a pretty crappy spacecraft.

Sputnik, Luna-3, Vostok-1 were all a bit disturbing to the US. There could have been more impresseve successes --photos from Mars and Venera capsules on Venus in 1962, and a Moon landing with pictures in 1964, etc. But ultimately, I don't think the Soviet system could have stayed ahead.

Landing a man on the Moon was carefully calculated to be the first major thing that America could do before the Russians, with almost no danger of getting scooped. They knew they had to catch up, but they also knew they were up against a burocratically planned socialist economy that couldn't make enough toilet paper for its people, much less land a man on the Moon.

I admire the spunk and cleverness of the Soviet scientists, but they were working in a hopeless system. They couldn't get modern electronic parts, they couldn't get sufficient QA. They flew 6-ton spacecrafts to Venus, filled with vacuum tubes and gears and relays. It's fascinating, but there was never any question of them beating the Americans.

[edstrick]

Mariner 2 flew with a lot of luck, but it was the real working prototype (based on Ranger) for the Mariner series, starting in mature form with Mariner Mars 64. The near total success of Mariner 2 proved that the essential design was right, and just needed maturing.

There were two real problems on Mariner 2. The Microwave Radiometer was apparently damaged during launch, I think they suspected a thermal shroud was damaged. One of the 2 channels was greatly reduced in sensitivity, and it's response was actually reversed! The other worked reasonably well. This sort of problem was instrument-specific, of course.

The spacecraft overheated badly, and failed not long after the Venus encounter, quite likely due to the overheating. Getting thermal control "right" took time. Modeling was not adequate, and in-space behavior of materials didn't match predictions as they outgassed, changed color, whatever. Mariner 4 actually carried an engineering experiment, besides it's science instruments and the experimental solar light pressure stabilization paddles. It carried a small set of candidate thermal control "plaques" on the sun-facing side of the main body of the spacecraft, with a temperature sensor behind each one to monitor it's temperature changes relative to predicted values as the mission proceeded.

Teeny-tiny "micro-experiments" like that can often be fitted on missions and return significant value for the future. The Magnets on Mars landers are also "micro-experiments", as was Geoff Landis's (I think) dust accumulation experiment of the Sojourner rover.

[tedstryk]

I have always thought that a problem with the Soviet craft, especially in the early days, was the fact that they were not constantly transmitting, meaning that problems could develop and kill them with much less data to doa post-mortem. That and the need for pressurization.

[JRehling]

What if the Mariner pictures had shown a Lowellian Mars instead?

Actually, what if Mariner 4 had only returned one image and it was the "Face"?

That extremely unlikely event would have made it a noncrazy hypothesis that it was an artifact. Then there'd be a long slow hiss of disappointment as more missions flew by.

[angel1801]

I believe that first impression of a body (ie planet, moon, etc) is important. If the first impression really wows the people, politicans and the scientific community, they will demand another mission. If not, future missions are very hard to justify, let alone get funded and launch.

Where first impressions were good:

Jupiter
Saturn
Titan
Moon
Neptune
Europa
Io
Miranda
Ariel
Triton

Where first impressions were not good:
Uranus
Mercury
Venus
Mars [1]
Pluto
Rhea
Oberon
Enceladus

[1] Mars is big news and popular largely because of the 1950's (and earlier) Sci-fi connotation


You see, us humans like seeing eye candy, even when it comes to outer space!

[dvandorn]

Mariner 4 actually carried an engineering experiment, besides it's science instruments and the experimental solar light pressure stabilization paddles.

Maybe it's just because I started following space exploration back in the 60s, but I have always been mystified by the negative reaction to "engineering experiments" on board any type of space probe.

I know, we can now use computer models to predict the operation of engineering systems. However, such models are only as accurate as the data input into them. It seems to me that, if an engineer feels the need to gather empirical data to support a model, it should be allowed if at all possible.

Engineering experiments might not return a ton of data about the planets, but they can make possible the next generations of spacecraft that *will* return such data. As such, I think they ought to be embraced and not sneered at...

-the other Doug

[Guest_DonPMitchell_*]

Mariner 2 flew with a lot of luck, but it was the real working prototype (based on Ranger) for the Mariner series, starting in mature form with Mariner Mars 64. The near total success of Mariner 2 proved that the essential design was right, and just needed maturing.

Mariner-2 was a repurposed ranger probe, yes. And the ranger series had a long history of failure. The lunar missions didn't work until Ranger-7 in 1964. Heads rolled over this, and there was a congressional inquiry. Mariner-2 suffered a number of systems failures:

1. Failure of one solar panel very early in the mission.

2. Failure of the temperature control system (a bad design, not a failure to function). By the time of Venus encounter, the spacecraft was over 100 C. I say "over" because the thermometers were off scale by then.

3. The optical navigation sensors used for attitude control were slowly going blind, only a few percent of normal signal by the time it reached Venus.

JPL was "Just Plain Lucky" as they joked at the time.

THe probe passed Venus at a rather great distance, which reduced the value of its magnetometer, but it got close enough to tell that Venus did not have as strong a field as the Earth. Venera-4 provided the first accurate measurement of the field.

The most important experiment of Mariner-2 was the mesurement of microwave limb darkening. Most historians fail to mention that one of the two microwave channels did not actually show limb darkening. And in fact, this measurment was performed from Earth by radio telescopes several months before the Mariner encounter.

OK, I'm beating a dead horse here. Mariner-2 still deserves an important place in history, as the first spacecraft to reach another planet and return data.

[tedstryk]

Granted, given the horrible luck of the early U.S. lunar program, it is almost a balancing out of things that Mariner-2 made it.

[dvandorn]

I'll take a stab at that simulation, but this is just scaled to match the Mariner-4 camera, and eyeballing the noise levels in actual Mariner-4 images...

Don, that is great work. Looks exactly like the Mariner 4 image quality. Thanks!

-the other Doug

[MizarKey]

What happened to Don's Mariner 4 simulation images from post #13? This thread isn't very old but the pics are gone.

[ugordan]

Maybe he accidentally erased all his attachments again?

[djellison]

Nothing done by me or the team.

Doug

[helvick]

Doug,

Don's messages refer to these attachments which appear to be dead links now.

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