I am currently working on a book about lunar exploration, but looking ahead to the next one, which will cover Mars. One question to which I think I have an answer - but I'd like to see what my fellow Mars enthusiasts think - is this:

Mariner 3 failed to leave Earth. But if it had flown successfully, what area on Mars would it have photographed?

My understanding is that there was no specific plan. The MM64 press kit, for instance, says nothing about image coverage for either Mariner 3 or Mariner 4. I believe that navigation to planetary distances was still so uncertain that the flight team could not predict at launch the sub-spacecraft point at closest approach - uncertainties included the exact time of the flyby, the distance and the point at which the spacecraft would pass through the target plane. These things would be known closer to the flyby but they weren't precisely predictable at launch, so Mariner 3 never got to the stage of having an imaging plan.

Am I right?

Phil

Well, actually it DID leave Earth -- it just left Earth still wadded up inside its nose cone (and missed Mars by several tens of millions of km as a result of the added mass...)

I can confirm -- having followed the US space program pretty closely since the end of 1964 (in fact it was the 1964 Mariners that turned me into a fanatic on the subject) that there was no specific target planned for either of the 1964 Mariners. The 1969 Mariners were the first to have such a goal.

I imagine they would indeed have played it by ear for the 1964 Mariners, taking into account both the initial trajectory onto which the Mariners were injected by their Atlases and the serious needs of the non-imaging experiments (atmospheric occultation, flight through Mars' solar wind shock). I also know that any flyby distance between 3600 and 8600 miles was considered acceptable for the Mariners -- Mariner 4 was eventually targeted for a flyby at 5400 miles range, but due to a slight midcourse error actually flew at 6100 miles. As you say, their targeting accuracy at that time was not high enough that they could afford to get seriously persnickety over which part of Mars they tried to photograph with the two Mariners. It's likely that they would simply have assumed that, as long as the two Mariners photographed different parts of Mars, ANY two such different parts were acceptable. (I have, by the way, never been able to discover where the remaining 1969 Mars Mariner would have been retargeted had one of them failed early on.)

Personally, if Mariner 1 had succeeded, I wonder whether one of the 1962 Venus Mariners might have tried a radio occultation of Venus' atmosphere -- although Arvydas Kliore seems to have started pushing that experiment only in early 1964. I do know that this was actually the single highest-ranked experiment on Mariner 5.

And while we're taking a stroll through Space Memory Lane, remember that until Mariner 2 succeeded NASA was planning two more Mariner R spacecraft to be launched on Venus flybys in March 1964 -- with some science instrument modifications (improved microwave radiometer and magnetometer; ion chamber and cosmic dust detector replaced by the same UV photometer that got kicked off the 1964 Mars Mariners because it caused TV camera arcing, and finally DID get flown to Venus on Mariner 5. See "JPL Space Programs Summary #37-19".) I wonder if, had they been flown, THOSE Mariners would have carried out a radio occultation of Venus -- they even had high-gain antennas designed from the start to be smoothly tiltable, whereas Mariner 5's fixed high-gain dish had to add a feature allowing it to suddenly be tilted into a new fixed position to partially compensate for Venus' atmospheric refraction of its radio beam. (Since the 1964 Mariners had Earth sensors mounted on their high-gain dishes to aim and tilt them, they might even have been able to pull off another experiment very seriously considered but finally rejected for Mariner 5: an Earth sensor to measure the altitude of Venus' cloud tops.)

Coming soon, if you're all nice to me: a brief report on how NASA came within one month of trying to launch a VENUS ORBITER in June 1959 (although it definitely would have failed had it been launched). One of the most bizarre forgotten episodes of the early Space Age.

If the time of the flyby was not well-constrained, then the answer falls out of that. An arrival a few hours earlier or later would have rotated any target terrain out of view.
It's an interesting question, however, since telescopic maps of Mars did exist, and there would therefore have been a basis for prioritizing targets, if the operational precision were there.

As a side note, we're now in a very similar circumstance with Pluto. Our telescopic (incl. occultation) maps of Pluto have roughly the detail that pre-Mariner maps of Mars did, and the single flyby we'll get will only provide best resolution at one longitude. (Although NH will certainly image the rest of Pluto in a way that Mariner 3/4 could not for Mars. Of course, Pluto won't receive any followups anytime soon.) It would be interesting to ask Alan Stern if any plutonian targets have thereby been prioritized. Have 40 years and a dozen+ solid worlds flown by given us any insights for Pluto-2006-launch that we lacked for 1964-Mars-launch??? The comparison is flawed, however: I think geometry regarding Charon's orbital position will actually drive the decision, rather than the visibility of specific Pluto terrain.

Thanks for these comments. And Bruce, I was inadvertently thinking of Mariner 8 not leaving Earth. You were right, of course.

Phil

Mariner 4 had a scan platform, and one option they had was to do the flyby with the platform in a slow back-and-forth <I think> scanning mode, maybe within a limited angular range. The pre-encounter decision was, as I recall, to set the platform at an angle that gave a "best" single swath of pictures across the planet: Middle of the illuminated limb, approximately across the sub-spacecraft point, and on to the terminator.

Arrival date would have set the hemisphere covered. If Mariner 3 had not been enshrouded at launch, Mariner 4 would have launched earlier and imaged some other strip, possibly hitting more interesting features, possibly somewhat less.

Bruce:

"Tell us about it, Janet!"

A 1959 Venus Orbiter - betcha it wasanother NOTSNIK!

You are right about Mariner 4 scan platform. A few hours before planetary encounter "NRT" (nonreal-time) power is turned on to energize the TV and scan platforms. The scan subsystem initiates a "search mode" of operation, causing the scan platform to oscillate such that the TV and scan sweep an arc approximately perpendicular to the motion of the spacecraft. When the planet comes in view of the scan subsystem sensor, the scan subsystem switches to a "tracking mode" in which the sensor and the platform is kept pointing at the planet.



More about Mariner 4 original telemetry data at Mariner 4 data analysis

Yep. In fact, they decided some months before the flyby to orient the scan platform in advance such that it would already be aimed at the estimated center of Mars' disk as soon as the tracking system was turned on, thus eliminating any need to actually move the platform. (This, I think, is what is Ed Strick was really referring to when he mentioned a decision not to "do the flyby with the platform in a slow back-and-forth mode" -- that wouldn't have occurred during the actual photography session in any case.)

Now, the two 1969 Mariners had not only a 2-axis tiltable scan platform, but a Mars wide-angle sensor capable of keeping that platform pointed at the exact center of Mars' disk on both axes (not on just one axis and at just one time, like Mariner 4's wide-angle Mars sensor). This was to ensure good long-distance photos of Mars' whole disk by the narrow-angle camera during the few days before the flyby.

Bruce.. that matches what I recall without digging into the archives. I expect the design was intended to be able to find the planet, even if command capability had been lost and the flyby geometry was poorly known.

I'm still at a loss to understand why missions like Galileo and Cassini don't have "planet sensors" to help with fine targeting during close encounters. Cassini's lost full disk mosaics of moons just cause the targeting was say 50 or 100 km off and a big chunk of limb was clipped.

Mariner 69 was the "bridge" to everything later. Mariner 62 and 64 had "central computers and sequencers", but they weren't reprogrammable in flight. Mariner 69 had 128 or 256 command-words of storage. (Mariner 9 in 1971 had (I think) 512.)

With that added command capability, they were able to reprogram Mariner 7 to take a full tape recorder load of some 33 pictures instead of about 24 that Mariner 6 did, DESPITE having a Loss-of-Signal event and major spacecraft emergency only 5 days before, while Mariner 6 was doing it's close flyby. (They added more frames to the pass over the south polar cap and then let the tape run till it was full as it crossed the terminator over Hellas, trusting that real-time telemetry would get the nightside and night-limb data, as it had worked on Mariner 6.) Mariner 7's battery had overcharged, shorted, and *RUPTURED*, venting into the spacecraft, sending it into a roll, and giving a small propulsive nudge to the spacecraft from the vapors venting from the main body of the spacecraft!

Yep, that's all correct. (Don't ask me how I remember exactly how many command words in memory Mariner Mars '71 had, when I have no idea how many any later spacecraft had...)

While the '69 Mariners were indeed a complete quantum leap upwards from the earlier Agena-launched Mariners in many ways, though, I think the most dramatic was the incredible leap in their communications rate from 8 bps for the earlier Mariners to fully 16,200 bits for the '69 Mariners. I couldn't believe that figure when I first read it in 1968 and thought it was a misprint -- especially since the earlier design for the "Mariner B" line of spacecraft on which Mariner 69 was patterened only had a bit rate of (I think) 256 bps. However, there had been very dramatic improvements in communcations technology since Mariner B was designed in 1962, and NASA decided to take full advantage of them.

Mariner 7's recovery from near-disaster was indeed very lucky -- although not as lucky as the incredible Perils of Pauline experiences of Mariner 10, when they practically had pieces fall off the spacecraft all the way to Mercury. (I suspect it was that experience that soured NASA on cost-control programs for some time.)

A planet sensor might be more trouble than it is worth in a system like the Saturnian system. For example, when studying one of the smaller moons, it might accidentally point the camera at Saturn, or even another moon. Also, it was originally hoped that the Mariner 4 track would touch the south polar cap, but it ended up missing. The planet sensor basically made sure that what happened to DS-1 at Braille did not happen (does anyone else find it ironic that imaging was unsuccessful at Braille?).

Ted - thanks for this... I'm not doubting you, but I would really like a source for the statement about the intention to image the south polar cap. I would be looking for more details about the plan, sufficient to plot the intended image coverage as well as the actual coverage, on a map.

Phil Stooke

I've got some documentation of this somewhere around here....might take a few days though....I need to figure out which box it is in, thanks to my recent move.

Mariner 69 and it's mission was designed around a much slower communications link than they ended up using. ... some 512 bits/sec compared with 8 <at mars> for Mariner 4. The 16,200 bps data rate was an "engineering test" included on teh spacecraft. The original goal was to tape some 8 late far encounter full disk images and fill the rest of the tape with near encounter images.

Since the high-data-rate link worked flawlessly and clearly had plenty of margin at Mars, the mission ended up using it for all it was worth.

Similarly, Mariner Venus/Mercury 1973 <Mariner 10> was designed around a 16,200 or whatever datarate, and included an engineering-test data rate of 144,000 or some such data rate with the intent of using it for real time transmission of all data if it worked and taping the closest encounter frames on a Mariner 9 vintage tape for backup and multiple replay to get best quality data.

Ted... I'd assume a planet sensor would only be "enabled" for final targeting adjustments when the target was already in view. Basically an auto-nav capability. They *** SHOULD *** have been able to do it using data from Cassini's wide angle <relatively> camera, but maybe the antique computer on Cassini can't do that much math. <sarcasm here>

And yeah... I though Braille was a bad-luck name choice even before DS-1 flew past.

I'm also intrigued about this and the current status of the Mariner IV data analysis page mentioned above.

In 1964, the question of whether there were 'canal' on Mars was still open, and although the Mariner 4 photos produced no evidence of canal, there was enough graininess to leave the question open - at least for the 'Hoaglandites'.

With both Mariner 3 and 4, they were hoping to get as close as possible, within NASA planet contamination control constraints, which was about 6000km.

http://ntrs.nasa.gov/archive/nasa/casi.ntr..._1968009274.pdf

Phil Stooke ... when will You start the work on the Mars exploration book ?
An interesting source for writing books & articles are the NASA Technical Reports written for each mission... I have made a list of the most important Tech Reports at the weblink below ( with thanks to Donald Boggs for hosting the list on his excellent spaceflight books website )

http://www.boggsspace.com/jpl_tech_reports.htm

Best regards,
Philip

I'm in the editing phase on the Moon book. Next year at this time I hope to begin the Mars book.

Phil

Great Phil ... don't hesitate to contact me whenever You need some information
By The Way are You also on forum collectSpace.com ?
Best regards,
Philip

In Bruce Murray's book "Journey into Space: The First Three Decades of Space Exploration" (1989), Murray gives an account of of a coup he pulled off for one of the early planetary spacecraft, which might be relevant to the quantum leap to which Bruce refers.

In the process of designing a mission, Murray was frustrated by the bandwidth limitations of communications with the Deep Space Network. Despite what Murray described as a policy of DSN to reveal as little information as possible to other NASA centers, an unguarded remark in a paper by a DSN engineer gave Murray an inkling that DSN's actual communications abilities were substantially (orders of magnitude?) better than it was willing to admit.

Murray made them 'fess up, and the mission's product return goals were substantially increased.

***

My memory tells me that this anecdote related to a sixties mission and that the destination was Mercury, but one of these must be false, since Mariner 10 wasn't launched until 1973. I owned the book briefly when it came out, thanks to an enthusiastic review in the NYT, despite the fact that my interest in space exploration was in a decades-long lull that didn't pass until December 2003. I had expected an armchair tour of Pioneer, Voyager, etc., and was disappointed by Murray's focused recollections of small group interactions and institutional politics. I had to borrow another copy from the library to reread it last spring, when I found it much more interesting. The account of early Shuttle politics is grimly fascinating.

Murray also singles out for criticism one or more eighties NASA administrators who couldn't be bothered to show up for important unmanned spacecraft rendezvous. The more recent administrators are doing much better.

Tom Tamlyn

Phil ... with ' information ' I meant in fact 'documentation' as I have a large collection of NASA photos showing unmanned spacecraft being tested & assembled before launch... So if You need a High Res photo, don't hesitate to contact me!
Philip
http://mars-literature.skynetblogs.be/

The only information I could find in my library was a reference to Atlas Able 4. Launch date seems to have been 11/26/1959 and the launch was a failure. Payload was a TV camera to view the earth's moon from lunar orbit. Original destination was Venus. Weight was under 400 lbs.

What's "the rest of the story"?

Inquiring minds want to know!

Should we fawn or something?

Not quite. The mission was Mariner Venus-Mercury 1973 (aka Mariner 10) but the realization was that if the bit error rate was increased the bit rate could also be increased, and with imaging it didn't matter much if the bit error rate was higher, since isolated bad pixels could be removed with simple filtering techniques (such as median filters.) MVM73's bit rate was 117 Kbps at a BER of 5e-3 for this reason.

See http://history.nasa.gov/SP-424/app-b.htm for more info.

Fawning won't be necessary. It was indeed the originally planned destination of one of the 1959 Atlas-Able probes. It and the probe that later became Pioneer 5, after being launched in 1960, were to be launched in the direction of Venus in the first few days of June 1959 -- but Pioneer 5 (lauched by a Thor-Able, later to be renamed Thor-Delta) had no midcourse correction system and so would certainly have missed Venus by a great distance, whereas the spin-stabilized Atlas-Able probe had two hydrazine engines pointing out its two poles. The rearward pointing one could be fired four times; the forward-pointing one only twice (at least in the lunar version), with one of those burns being for final orbit insertion -- but apparently they had some confidence that this awkward setup could put them close enough to have a shot at orbiting Venus.

This thing came astonishingly close to being launched -- the front-page headline for the NY Times on (I believe) May 1, 1959 shows the mission being cancelled only then, apparently because the planned science experiments couldn't be gotten ready in time. I've spent years trying to find out what those experiments were, but the only clue I've found is a single paragraph in a 1959 issue of "Astronautics" magazine quoting a Lousisiana Congressman on "Meet the Press" who very briefly described them in a way which implies that they were exactly the same as on the second Atlas-Able Pioneer, which was scheduled for a launch to the Moon later in 1959. That is, they were particles and fields experiments, plus an IR photometer that could build up a low-resolution spin-scan map -- of the Moon's farside, or (presumably) Venus' cloud tops. (I'd assume that such a craft could have carried a UV photometer like Mariner 5's, to measure the planet's atomic H and O and thus provide an indirect estimate of its water vapor; but this wasn't mentioned. I also presume that it could, in any case, have carrried out radio occultations of Venus' atmosphere.)

At any rate, after that cancellation, Pioneer 5 was rescheduled for a launch in late 1959 into a solar orbit with its perihelion at Venus' orbit -- and after months of technical delays it ws finally launched in March 1960, although the booster underperformed somewhat and so it fell well short of reaching Venus' orbit. They had hoped to communicate with it at distances of up to 50 million miles, but a slow battery leak finally silenced it 22.5 million miles out -- which still utterly shattered Pioneer 4's radio-range record of 407,000 miles.

The Atlas-Able probe was rescheduled for that single launch to the Moon on Oct. 3 (a day before the Russians launched Luna 3), but its Atlas booster blew itself to kingdom come during a static test on Sept. 24, so they drafted the Atlas that had been scheduled for the second unmanned Mercury "Big Joe" test (which had been cancelled because the first was successful) and attached the Able upper stages and the probe to that instead. It took off on Nov. 26 and immediately failed ignominiously because its payload shroud hadn't been adequately vented and came off due to internal air pressure about 45 seconds after launch; the air blast quickly tore off the probe and the third stage, and damaged the second state enough to knock out its radio (apparently it then ignited without separating from the Atlas). This, of course, would have happened had it been launched to Venus.

Since the cancellation of the Venus launch meant that they still had a second such probe built, the White House ordered a third probe to be built, one launch attempt to be made in 1960, and the third probe launched only if that first 1960 effort failed. Alas, they too both failed. (Neither carried that IR scanner; instead, they were the very first US spacecraft to carry plasma analyzers.)

Clearly NASA's very early ambitions exceeded its grasp; the agency must have initiated this plan almost as soon as it was created at the start of 1959. It's very hard to find data on the Venus plan for this thing, but I first heard about it at age 11 from the space column of a 1959 back issue of "Sky & Telescope". You can find sprinkled references to it in other places, such as Aviation Week -- and notably that NY Times front-page headline article -- but about a decade ago, when I corresponded with one of the experimenters for the Atlas-Able probes' radiation experiments to try and get more information on it (he'd written a late 1980s nostalgic retrospective in a major science journal), I was thunderstruck to learn that HE had never heard of the Venus part of the plan!

You can find a brief Web reference to it: a chapter of Homer Newell's official 1979 NASA history document "Beyond the Atmosphere: The Early Years of Space Science: http://www.hq.nasa.gov/office/pao/History/SP-4211/ch10-4.htm . (There were nine early Pioneers rather than eight, though -- he forgets the Air Force's very first lunar Pioneer attempt in August 1958.)

Amazing!

NASA certainly had the 'vision thing' right out of the starting gate. I suppose with no past negative experiences in trying an ambitious planetary mission, everyone involved was pretty gung-ho to orbit Venus.

Egad, what if they had tried and succeeded?

Appreciate the update on this, I had never expected to know any more than what I posted about Atlas Able 4. Jane's had put out a reference book in 1987 that had a brief blurb on the mission. They did have a launch photo of Atlas Able 5, too.

Wonder what else they were thinking about back then?

Random note: The UV photometer that flew on Mariner 5 to Venus was supposed to fly on Mariner Mars 64, but the instrument had high voltage electrical problems during development, and was replaced by a mass model (and maybe electrical-draw model, to preserve fidelity to all spacecraft/instrument interactions) that of couse did nothing scientifically. The problems were fixed in time for Mariner Venus 67.

Try the combination of "Venus" and "Atlas-Able" on Google. I did just now and found a few new tidbits -- including one article ( http://66.102.7.104/search?q=cache:Lt4FgV9...e%22+arpa&hl=en ) that goes into a bit more detail about just how NASA initially embraced this thing (apparently it started out as the Air Force's planned successor to its unsuccessful 1958 Pioneer lunar orbiters), and one German author ( http://www.bernd-leitenberger.de/pioneer-p.html ) who's dug up the precise cause of that static-firing Atlas explosion.

However, LePage's article says that NASA decided to cancel the Venus orbiter (though not the Pioneer 5 Venus flyby) very early in 1959, which directly clashes with that NY Times article and my other sources. And the German's got the failure causes of the remaining three flights mixed up -- his very last paragraph records the true cause of the Nov. 1959 failure while mixing it up with the Dec. 1960 failure, and he falsely says that the Nov. 1959 failure had a similar cause to the Sept. 1960 one, having clearly instead printed two accounts of the latter that differ slightly in their phrasing.

Yeah, I've got the full dibs on the process by which Mariner 5's science payload was selected. And I knew about the 1964 problems with the Mariner Mars UV photometer all the way back in 1964, nyahh nyahh! (It was only some time later that they decided to add the radio occultation experiment, which as things turned out told us a lot more about Mars.)

The problem with Mariner 5 is that they decided to fly it literally at the last minute -- Dec. 1965 -- and there was simply no time to develop some of the experiments they would have liked most to include, such as UV or IR spectrometers. (In fact, the radio occultation experiment was officially ranked as the most important one!) But they did come fairly close to adding an Earth-occultation photometer that could have told us what the cloud-top altitude was, which makes me wonder whether it might have clued us in to the clouds being sulfuric acid -- which instead wasn't discovered until 1973.

By the way, I first learned about the cancelled 1959 Venus orbiter back in 1965. The Space History Geek Knows All! (Or would like to think so.)

While we're on the subject of lost opportunities: I heard in spring 1967 that NASA was seriously considering launching a sixth Lunar Orbiter made out of the program's leftover spare parts (though it was thought unlikely even then), and remember thinking how nice it would be if they'd fly it with a copy of the gamma-ray spectrometer from the failed 1962 Rangers. In 1977 I learned, to my astonishment, that they had planned to do just that. (Otherwise it would have been similar to Orbiter 5, but would have photographed the Moon's far side in as good detail as Orbiter 4 had done for the near side.)

Well, they ended up leaning against flying this (it would have flown in Nov. 1967) even if Orbiter 5 had failed, and its success totally kiboshed Orbiter 6. I find myself wondering, though, just how much of Lunar Prospector's data might have been gotten three decades earlier if they had flown this -- or put the GRS on Orbiter 5. (I doubt the GRS could have detected the hydrogen at the poles, but I don't know it for sure.)

Bruce Moomaw: ".... But they did come fairly close to adding an Earth-occultation photometer that could have told us what the cloud-top altitude was, which makes me wonder whether it might have clued us in to the clouds being sulfuric acid -- which instead wasn't discovered until 1973....."

I doubt it would have helped much. We actually "knew" what the cloud top altitude was from the visible/(and IR?) spectra of CO2, assuming the atmosphere was CO2 dominated, and not mostly nitrogen. And UV data indicated little Rayleigh scattering gas above the cloudtops, so there wasn't a huge over-abundance of Nitrogen.

What we didn't know was the "altitude" o fhte suface below the cloud tops!.... where the bottom was.

The expectation was that we'd eventually learn the cloud composition from infrared spectra, but that was "underinformative" and we weren't experienced enough to find a match to the so-so at best quality data we had. Somehow, people never included sulfuric acid in lists of candidates matched against cloud data so there never was a good match. A review article from the early 70's showed a distinct sense of frustration at the lack of progress and lack of signs of how to make progress in solving the problem.

It took polarimetery data from earthbased observations to suddenly break the logjam. It showed with astonishing precision that the cloud particles were non-absorbing spherical droplets, about 2 micrometers in size with a narrow size distribution, and last but overwhelmingly most importantly ... a refractive index of 1.44 +- 0.01 (If I remember right).

This totally blew away any candidates and yielded 90% sulfuric acid droplets as the only even close match.. and it wasn't close.. suddenly everything fit and made sense.

They certainly came breathtakingly close before then -- hydrochloric acid was one of the favorite theories.

I'd have to dig in my "stacks" to find the review article that tried to evaluate a good number of candidates for Venus' Clouds against the observational data and failed. Hydrochloric was one of them, and flunked on a number of grounds, I think the main one being the observed abundance above the clouds was far to low for the clouds observed temperature. They'd have to have been much colder to have the observed HCL vapor levels.

Sulfuric Acid just didn't seem to be on anybody's list so the multiple choice answere was: D.) None of the above. It might have emerged as a leading candidate if it had been included in the list.

Based on Venera and Vega descent composition data, and argued-about Pioneer Venus cloud particle spectrometer results, there are other composition particles in the clouds, but we know almost nothing about them, and the information is distinctly contradictory. Venera 13/14 and/or Vega 1/2 collected aerosol on a filter and then x-ray fluorescence'd them for element abundances, and got (besides sulfur), I think, Iron and Phosphourus. Iron Chloride was a proposed cloud component in the early 70's, I think. Sulfur crystals are one candidate for larger particles, but I don't know the current status on that as a candidate.

Polarimetry has almost always been a technique in search of problems to solve in Planetary Science. Unfortunately, it's far less revealing of particle properties when measuring scattered light from solid, non-spherical particles, whether they're martian dust and ice hazes, Jovian etc ammonia and other hazes, or Titanian tholin smog. It does help study atmosphere structure, the size/abundance of aerosols with altitude, and the crude physical properties of the aerosol particles, but it's only had the one "mega-success" of nailing the main Venus cloud composition.

Any truth that Mariner 4's flight path was aimed at a region of the
planet where a number of "known" canals were?

Not really. Any long strip of images like that would cross a few canals. The targeting was all just about the trajectory design and a desire to see light and dark areas.

Phil

At that time they had very little confidence in their ability to aim the Mars Mariners within more than a few thousand km of ANY target -- and sure enough, Mariner 4 ended up flying by Mars at 1200 km higher altitude than had been intended in the midcourse maneuver. Just photographing Mars would be adequate.

For the canal freaks, the flyby trajectory and viewing was rather disappointing, as the image strip generally crossed what were generally mapped as minor, low-contrast canals.

What finally nuked the canalist's hopes were the global Mars Rotation Sequences from Mariners 6 and 7 on approach.

Imagine if the random-ish targetting of Mariner IV had picked up on any of the dried up river channels - or if we'd recognised what we were seeing on those Mariner 1969 far encounter sequences (Valles Marineris is there, if you look not very hard at all!). Or if just *one* Soviet image had scooped the US with a picture of a dried-up-something, or a volcano, or...

Still, we got there in the end (and even Mars Observer has now, in effect, flown again!).

Bob Shaw

Oh, yes. I well remember the shock when the dust cleared and all those things started getting gradually unveiled before Mariner 9. Still, I doubt that their earlier discovery would have done much to change the schedule of launches -- the one aspect of that schedule that wasn't rational was the launch of the 1969 flyby Mariners instead of jumping directly to 1971-type orbiters, and that was a consequence of the fact that the Mariner Mars program kept getting expanded incrementally as the Voyager Mars program gradually fell apart. (I even learned recently that in 1968 they seriously considered cancelling the second 1969 Mariner flyby so that they could save money by rebuilding the craft into one of the 1971 Mariner orbiters, as they rebuilt the 1969 spare flyby craft into the other 1971 orbiter.)

Talking about Mariner IX... Phil (Stooke) I've contacted You about the Martian Moons article
Thanks again for Your help...
Philip

Bruce:

As things turned out, yes - but if Mars had been seen as more like Earth than merely a big Moon then we might have seen quite a different turn of events. Stephen Baxter had fun with some of these possibilities in his novel 'Voyage'.

Bob Shaw

I wrote a story with William Barton that appeared in Amazing a few years back called "Thematic Torus in Search of a Cusp." It's also alternate history starting with Mariner IV finding large structures on Mars. For us as kids Mariner IV was a watershed event, and I didn't really get interested in planetary exploration again until Voyager.

Michael

It was for me, too. Although I was already interested in science, it was the news in a Sept. 1964 issue of "My Weekly Reader" that there were two Mariners scheduled to go to Mars (which I hadn't known, although I already knew about the Rangers and the 1962 Mariners) that turned my tentative interest in Solar System exploration into a flat-out obsession.

By the way, Harry Turtledove -- who specializes in alternate history (he's just finishing up Vol. 10 of his grisly history of the world if the South had won the Civil War) -- wrote a novel called "A World of Difference" back around 1990 on how things would have turned out if everything had been just as it actually is except that Mars was Earth-sized and therefore capable of holding a CO2 atmosphere dense enough to keep it habitable despite its distance from the Sun, and the last photo from Viking 1 had shown an indignant native advancing on it with a club. Plausibly but depressingly, the US and the Soviets would immediately have started trying to convert the Martians to their particular ideologies. (Since such a planet would have been dazzlingly bright white rather than red, it would have been called "Minerva".)

P.S.: I admire the hell out of Barton's considerably grimmer and more likely alternate history story "Age of Aquarius", on what the Sixties would have been like if the Cuban Missile Crisis had turned out just a wee bit differently.

I do too, and I'm a character in it. It's a shame it hasn't been reprinted. Did you catch his alternate lunar program story "Harvest Moon" in Asimov's last year?

Michael

'Now that we have a map, let's start colonizing outer space'

The Register Mar. 17, 2006

*************************

Mapping the solar system started in
1965 when Mariner 4 sent back much
improved pictures of Mars, said SETI
expert Seth Shostak. Since that
time, astronomers -- with the help
of high-powered telescopes and
various exploration vehicles and
probes -- have delivered stunning
pictures of most of the planets and
their moons. The quality of these...

http://www.kurzweilai.net/email/newsRedire...sID=5393&m=7610

Hey, I'm interested! Was this the idea of sending Pioneer 5 toward Venus?

One of the greatest old books on space is the McGraw Hill Encyclopedia of Space (1968). Find a copy if you can, and buy it! I sure wish someone would put together a contemporary book that's as good. One odd thing about this book is that it lists Pioneer 5 as a failed Venus probe, which I don't think is quite accurate. But the idea must have still been in the air then.

And I'm still looking for a really good photograph of Pioneer 5.

The scheme was more complex than that. It did involve launching Pioneer 5 toward Venus in early June 1959, but without a midcourse correction motor no one thought it would get anywhere close. HOWEVER: it also involved simultaneously launching the very first of the much bigger Atlas-Able Pioneer orbiters to Venus -- and since that had two restartable hydrazine motors sticking out of its poles, the plan really would been to make an honest effort to put it into Venus orbit. Aviation Week had several short items on it in 1959 -- and the NY Times of (I believe) May 1, 1959 made the plan's last-minute cancellation its front-page headline. (It was cancelled on the grounds that "the science payload could not be gotten ready in time", by which NASA may have meant the entire spacecraft.)

A second Pioneer orbiter was to be built simultaneously to be put into lunar orbit later. I've wasted a little time trying to find out what the exact science payload of the Venus version would have been, and all I've been able to find is one short paragraph in a 1959 aerospace magazine quoting a Democratic Louisiana Congressman briefly describing its payload on "Meet the Press" in a way that suggests it would have been identical to the payload on the lunar Atlas-Able orbiter -- that is, a bunch of fields and particles instruments plus a spin-scan IR photometer that could build up images (in this case, presumably a temperature map of Venus' cloud cover). No mention of a UV photometer, which would seem to be a natural for such a mission -- but such an orbiter could have given us radio occultations of the atmosphere.

I first heard about this plan all the way back in 1965, when I was 11 years old. (It was mentioned briefly in a back issue of "Sky and Telescope".) But finding information on it is like looking for an Upsidaisium mine -- you just find tiny crumbs here and there (including one brief mention in the June 1959 "American Mercury", H.L. Mencken's magazine which by then had been bought by a bunch of rabid right-wing anti-Semites who used to refer to "the Jewish termites gnawing at the Cross"). I finally found, in an early 1990s issue of the Proceedings of the National Academy of Sciences, a long historical reminiscence by a fields and particles scientist mentioning some of the instruments he'd put on these Atlas-Able orbiters, and I eagerly asked him for the Straight Dope -- only to be told that even HE had never heard of the Venus plan!

Anyway, after the cancellation of that plan, the goal of the smaller Pioneer 5 remained to be put into a solar orbit with its perihelion at Venus' orbit -- and after sitting on the pad through delay after delay during the last half of 1959, it finally got off the ground in March 1960 and became the only genuine success of the early Pioneers (although its perihelion ended up considerably outside Venus' orbit, and its power supply failed at a range of 22.5 million miles instead of the 50 million hoped for). The plan to launch a single Atlas-Able orbiter to the Moon remained; and after its planned October launch was scrubbed when the booster blew up during a September static test, NASA grabbed the Atlas planned for the cancelled second Mercury "Big Joe" test and launched it in late November -- only to end up with the infamous "turkey shoot" in which the shroud came off due to inadequate venting of internal air pressure, and the air blast then tore off the probe and third stage and crippled the second stage. No doubt this would have been its fate had it been launched to Venus in June.

Since this meant that there was still one spare Pioneer orbiter, Eisenhower gave permission to try to launch it to the Moon in late 1960 -- and to build a third copy for one last attempt if the second one failed. Unfortunately, both the second AND third tries also failed ignominously (due to failures of the second stage, which by then was usually working pretty reliably on Thor-Able). Both these versions had slightly changed science instruments -- the IR farside spin-scanner was removed and replaced by the first plasma probe on any NASA spacecraft, for instance. All the instruments on those two 1960 lunar orbiters were fields and particles; pretty much the only information they could have gotten on the Moon itself was to look for a magnetic field, but then that was also the case for Explorer 35. And so ended one of the stranger (and sadder) forgotten stories of the early Space Age.

Very interesting. I don't think their rockets could have hit Venus at that time, and I'm pretty sure the telemetry system couldn't have picked up its signal (Only Jodrell Bank could get Pioneer 5's signal after about a month), so there were probably a lot of reasons it was not actually done. But it is too bad there is not more written about this.

I have been intrigued by the notion of comparing detailed images,
from the Viking Orbiters or Mars Express, of the same areas of Mars
photographed by Mariner 4.

Here is a view of the footprints of each Mariner 4 image.


Click to view attachment


Here is a link to a low-res map of where those images are located
on Mars.

http://www.solarviews.com/raw/mars/mar4geom.jpg


Does anyone have access to Viking or Mars Express images that
would match up with those of Mariner 4?


Another Phil