Minor Mariner 4 mystery Options

[tasp]

Following the successful Mariner 4 encounter with Mars, the craft, on September 15, 1967 apparently encountered a meteor stream.

The craft recorded 17 strikes in only 15 minutes with (IIRC) it's cosmic dust detector. I am not sure any other instrument on the craft recorded the event.

Additionally, the craft had a small change in attitude and the internal temperature dropped roughly 1 degree as an apparent result of the damage to the thermal protection system.

Other than the ESA Halley mission, has any other craft experienced anything like this?

Was any ID of the meteor stream ever made? Perhaps it is associated with one we see on earth. I don't know if any of the new mission tracking software would be helpful in pinning down Mariner 4's position then. Also, I'm not sure if the small attitude change would help pin down a direction the the stream was moving in.


What an unusual event! Seems like something that might barely effect a relatively 'primitive' craft (no offense to the builders!) might be rather more drastic on a modern craft.

[Decepticon]

Didn't the Pioneers experience this also?

I vaguely remember reading as a child something about the Pioneers experience something similar to Mariner4.

[tasp]

Didn't the Pioneers experience this also?

I vaguely remember reading as a child something about the Pioneers experience something similar to Mariner4.

I have the NASA SP on the Pioneers, will check for that. Thanx for the recollection.

I do recall the Pioneers observing fewer meteoroids in the asteroid belt (apparently they get swept up by all the larger objects). That would imply seeing more elsewhere, of course.

I wonder if a meteoroid stream seen from the sunward side would noticeably brighten the geigenshine (sorry for spelling) ?

Fascinating if that particular stream Mariner 4 encountered could be associated with a specific parent object.


I have wondered if a similar meteoroid stream phenomena might exist at Jupiter or Saturn. Perhaps past objects like Shoemaker-Levy left a stream of particulate debris behind in orbit around the planet. (I suspect such features, should they be possible, would dissipate rather more quickly than the sun orbiting variety).

[edstrick]

The identification of the event as beign due to a meteor stream was probably way over-interpreted. Subsequent work seems to have proven that the piezo-electric impact-acoustic-signal detection instruments were plagued by thermal contraction and expansion noises and any variation in temperature <due to illumination> on the detector produced bogus results.

The first solidly unambiguous meteoroid data were from the penetration cells on the Pegasus spacecraft launched on the last 3 or 4 Saturn 1 test flights

Lunar Orbiters 1 through 5 carried a ring of penetration cells on the spacecraft bus, which extended the Pegasus data to lunar orbit, while Pioneer 10 and 11 used similar cells to take the measurements well beyond Jupiter and Saturn.

I think the Mariner 4 data was spurious, but I'm not intimately familiar with the literature.

[Bob Shaw]

The identification of the event as beign due to a meteor stream was probably way over-interpreted. Subsequent work seems to have proven that the piezo-electric impact-acoustic-signal detection instruments were plagued by thermal contraction and expansion noises and any variation in temperature <due to illumination> on the detector produced bogus results.

The first solidly unambiguous meteoroid data were from the penetration cells on the Pegasus spacecraft launched on the last 3 or 4 Saturn 1 test flights

Lunar Orbiters 1 through 5 carried a ring of penetration cells on the spacecraft bus, which extended the Pegasus data to lunar orbit, while Pioneer 10 and 11 used similar cells to take the measurements well beyond Jupiter and Saturn.

I think the Mariner 4 data was spurious, but I'm not intimately familiar with the literature.

At the time, it was 'a well known fact' that meteor showers were a Big Problem in outer space, so the interpretation of whatever was recorded would have leaned in that direction. It's almost a cultural thing, rather than objective reality. I wonder if the meteor shower would have made a 'whoosh' noise as it passed by...

...equally, we may currently be predisposed to accept or reject things on a false basis, too!

Bob Shaw

[JRehling]

The first solidly unambiguous meteoroid data were from the penetration cells on the Pegasus spacecraft launched on the last 3 or 4 Saturn 1 test flights

The Earth's atmosphere isn't a bad detection instrument for all but the tiniest meteoroids... It's pretty obvious that an area of ~100 square km doesn't average so much as 4/hour in the size range we can detect photographically. That is about 10^7 times bigger than a spacecraft. Kick the size threshold down according to a power law, and you can derive that a spacecraft-sized object should be able to fly quite a long time without hitting anything non microscopic (at least on the order of 10,000 hours ~= a couple of years) -- at least, in near-Earth space.

At the time, it was 'a well known fact' that meteor showers were a Big Problem in outer space, so the interpretation of whatever was recorded would have leaned in that direction. It's almost a cultural thing, rather than objective reality.
Bob Shaw

Excellent point. Qualitative reasoning takes another blow to the chin.

[Bob Shaw]

The Earth's atmosphere isn't a bad detection instrument for all but the tiniest meteoroids... It's pretty obvious that an area of ~100 square km doesn't average so much as 4/hour in the size range we can detect photographically.

Isn't it strange that we worry about space junk - and see the effects on things like the LDEF - and yet us guys on the ground don't see all that garbage when it burns up? I realise that a lot of the junk is in orbit at a reasonable altitude, but for small particles the drag from our atmosphere should have quite a big effect even at heights where spacecraft can survive for years.

Or am I missing something?

Bob Shaw

[odave]

I think sometimes we do see it burn up. A casual glance at a given "shooting star" may not be enough to differentiate a bonafide meteor from mere "shooting junk". I think you'd need to consider the trajectory as well - if it's along any of the usual satellite orbits, then it may be reentering junk. This would be even more apparent during one of the known meteor showers - if the trail does not point back to the shower's radiant, it's probably not part of the shower. But trajectory alone probably isn't enough - maybe some meteor jock out there may know more...

[JRehling]

This would be even more apparent during one of the known meteor showers - if the trail does not point back to the shower's radiant, it's probably not part of the shower. But trajectory alone probably isn't enough - maybe some meteor jock out there may know more...

I don't see any way to determine based solely on trajectory that a meteor is space junk unless the item can be shown to be in an elliptical rather than hyperbolic orbit before it slows significantly. Since it only becomes visible after it has encountered significant kinetic-to-thermal energy conversion, that seems impossible... for a single meteor.

However, it seems possible to do a survey and see what proportion over and above expectations have headings typical of Earth orbit (modest inclinations and west->east headings) and see if a signal rises above the noise.

[Bob Shaw]

However, it seems possible to do a survey and see what proportion over and above expectations have headings typical of Earth orbit (modest inclinations and west->east headings) and see if a signal rises above the noise.

The funny thing is, there are a bunch of cameras looking at the whole sky in order to do just that, but I've never heard a peep about any artificial component. You'd think that the Great Plains meteorite hunting cameras would see something, or (perhaps even better for high inclination debris) the guys in Antartica.

But... ...nothing. Nada. Zilch...

Bob Shaw

[edstrick]

Oh.. another thing I remember on that Mariner 4 mystery...
The supposed meteor stream data may have occurred as the spacecraft had run out of attitude control gas and was starting a slow wobble-spin, shortly before they ended the mission and commanded the transmitter off. That would have caused the thermal variations on the piezoelectric acoustic impact sensor that would make "crinkle" noises counted as impacts.

I believe that they "identified" a known cometary orbit the spacecraft was passing near or through and presumed <concluded> that was the source of the "impacts".

[Guest_BruceMoomaw_*]

Yeah, you're right -- it did occur after the attitude-gas exhaustion, and Aviation Week reported at the time that the "impacts" had made the craft's wobble more serious and forced them to shut it off. I had completely forgotten about the whole story (thanks to Tasp for unearthing it), and I had never heard Ed's thermal explanation -- which makes sense. (It may also explain why Mariner 4 recorded over 100 dust impacts, while Mariner 2 recorded the grand total of 2.)

[tasp]

All I had was a 2 sentence reference to the event in my Jane's book on lunar and planetary probes. I figured it was a near certainty someone here had more info on it.

Had it not been spurious, it would have been a very fascinating event. Especially for what was only the US's 2nd successful planetary probe.

Fortunately for todays delicate craft, such perilous meteoroid streams seem rather more scarce.

Thanx all!

[ElkGroveDan]

I wonder if the meteor shower would have made a 'whoosh' noise as it passed by...

The only whooshing sound you hear in space is when a spacecraft overheats it's brake drums while pulling in to a tight orbit.

[Guest_BruceMoomaw_*]

Thefre was a half-page article on it on Aviation Week at the time -- although the only other detail I remember at this point was that it occurred a week after the craft had run out of attitude-control gas. Whenever I get back to the UC-Davis library, I'll look up the incident again, although I really don't think there's much more to be said about it.