Apollo 11 SLA panels - how bright?

[ChrLz]

Do we have any resident expert/s on luminosity of tumbling objects in space illuminated by the Sun?

Over at Unexplained Mysteries, the topic of the Buzz Aldrin "UFO" has re-surfaced, and Lost Shaman has offered an 'interesting' calculation which he seems to want to use to create a figure (or range - I can but hope!) for the distance the SLA panels would have to be for their reported brightness.

He made these initial comments:

I've been thinking of calculating this recently after I had done similar earlier this year with LUU-2 flares in the Phoenix Lights case. Of course that was much easier because there we could start with the LUU-2 specs that tell us those Flares are rated at 1,800,000 lumens. That's a pretty easy starting point. But an SLA panel isn't so easy. One side is painted NASA White and convex, and the other is metallic and concave. What are the Albedos of those surfaces? It will take a bit of research to come up with a reasonable luminance for the two sides, but then it would be fairly straightforward using the inverse square law equation:
  B =  L
  --------
  4piD^2

B = Brightness
L = Luminance
D = Distance (Radius of a sphere)

He then did the calculation:

So I played around with some numbers, and IF assuming a Panel was reflecting all the light hitting it(*)... It would be 412.59 statute miles away to flash at you as a Mag 1 star (1.0E-6 Lux). Now that distance would be closer depending on an SLA Panels actual Albedo (which I do not know, anyone know that?). If Albedo of 0.9 that distance would be 391.46 statute miles.
* Area of SLA Panel = 43.5715 m^2 X 1,370 w/m^2 = 59,692.955 watts X 93 Lumens per watt of solar Flux = 5,551,444.815 Lumens (4,996,300.3 Lumens @ 0.9 Albedo)

(Just ignore the ridiculous use of up to 8-digit accuracy for a moment!!)
When I saw that calculation, while my knowledge of this type of analysis is rather slim, I'm thinking that it doesn't seem to be taking anything much into account, like f'rinstance:
- the panels are strongly curved - doesn't that mean the *reflecting* surface area is less, or is that for only specular illumination (isn't this a mixture of specular and diffuse, esp given we are talking about the 'flashes'?)
- the panels may have been at any angle, including end on at times, rotating on deity knows what axis
- the albedo of 0.9 seems a little *non*-conservative, especially for the inside and given the points above

The point seems to be that we are talking about only the 'flashes' as being the operational number, but even so, is that calculation valid?

I queried the claim and invited Jim Oberg to comment, and he thinks I'm wrong too... Oh well, I'm currently outgunned!  But I still have a strong feeling that this is being reduced to unjustified simplicity!  I'm happy to apologise and accept that the calculation is right, but I'm finding it hard to find references one way or the other and I'd really like another opinion or two, preferably from someone/s who genuinely has/have the expertise...

And then I can try to work out where LS wants to go with this.  I think he really wants the SLA panel to be (twilight zone music) something else....

[ka9q]

One comment about tumbling. If an object has some way to dissipate energy, e.g., by flexing, by sloshing a liquid, etc, it will eventually settle down into a stable spin around the axis with the greatest moment of inertia. For a SLA panel I'd expect this to be the axis normal to the surface, i.e., a "flat" spin.

But I can't say how long it would take for this to happen. The SLA panels were jettisoned tumbling end-over-end. They were fairly rigid and (unlike a spent rocket stage) contained no fluids, so they might have retained their original rotation for a long time -- perhaps longer than their travel time to the moon when they would have parted ways with Apollo 11 as it decelerated into lunar orbit.

I wonder what eventually happened to them. If the TLI gave a truly precise free-return trajectory, they would have looped around the moon, returned to earth and burned up in the atmosphere. The S-IVB is in solar orbit only because, after jettisoning the SLA panels along with Apollo, it dumped propellant, slowing it down enough to pass the trailing edge of the moon where it got a slingshot kick out of earth orbit.

[Kiwi]

Bill Keel's marvellous web page, "Telescopic Tracking of the Apollo Lunar Missions" at the University of Alabama's website
http://www.astr.ua.edu/keel/space/apollo.html
has photos shot from Earth that include SLA panels from some of the missions and mentions the magnitudes of various bits and pieces, so you might be able to find something useful there.

For those who want to learn Astronymish:
Back in the olden days of the 60s and 70s, there were two uses of the abbreviation SLA.  One was Spacecraft Launch Adapter and the other, which applies here, was SM/LM Adapter, and it contains two more abbreviations, SM for Service Module and LM for Lunar Module. The adapter held the two of those together for launch from Earth, and its covering panels prevented the LM being destroyed by the tremendous pressure of the atmosphere while the Saturn V was hurtling through it at speeds we can hardly imagine.

[bknight]

Bill Keel's marvellous web page, "Telescopic Tracking of the Apollo Lunar Missions" at the University of Alabama's website
http://www.astr.ua.edu/keel/space/apollo.html
has photos shot from Earth that include SLA panels from some of the missions and mentions the magnitudes of various bits and pieces, so you might be able to find something useful there.

For those who want to learn Astronymish:
Back in the olden days of the 60s and 70s, there were two uses of the abbreviation SLA.  One was Spacecraft Launch Adapter and the other, which applies here, was SM/LM Adapter, and it contains two more abbreviations, SM for Service Module and LM for Lunar Module. The adapter held the two of those together for launch from Earth, and its covering panels prevented the LM being destroyed by the tremendous pressure of the atmosphere while the Saturn V was hurtling through it at speeds we can hardly imagine.

Those are a good group of images of the Apollo missions, I have to admit that I could not make out what was described, but I'm looking at a single image not a real time observation through a telescope.

[ChrLz]

Thanks for the helpful comments and links.  Thinking further about this led to me coming up with a whole pile of objections to the approach, which was essentially to use the maximum surface area (wrongly calculated) of the SLA panel as the light source and assuming it was going to be fully face on at some point to any given observer, and from that compare it to magnitude guesses made at the time...

IMNSHO,
- the axis of rotation is essentially impossible to guess at (it was set spinning by a fairly simple spring mechanism that was only intended to push it away, and the forces thus imparted could have partly gone into spinning it, as well as imparting the outward velocity.  So, given the spin after some time could be anything from a flat side on spin (ie virtually no surface area facing observer at any time, thru to a flat outside-area-facing-observer spin (albedo would be close to 1 at times..) and a flat inside-facing-observer spin (albedo maybe 6? from the dullish metal) and anything in between...you just can't say anything useful from using the max possible surface area reflectance..
- the distance is also impossible to guess at - given 4 sla panels were sent spinning, and the spacecraft curved away to a different path, at least one of the panels could have remained quite close..
- there is nothing much to compare any calculation with anyway - they were only loose guesses at the magnitude of the 'ufo', and it wasn't clear if comparative stars were in the field of view..

Too many variables and unknowns, huge error ranges, subjective comparisons?  No way.

Anyway, even right at the start - his calculation of the SLA panel surface area was painfully incorrect, at 40+ square metres...  I won't give the correct answer as I'm giving him time to do it properly.. you know, teach 'em to fish...   Interestingly, about ten years ago he made similar claims, but on that occasion his SLA area was .. 17 sq m!   (Still wrong, and the new one is worse....)

So I think it's a dead end.  I still believe an SLA panel is the likeliest candidate (so does Buzz, and I've seen what happens if you argue with him !)  While I guess mylar off the LM is also a possibility, I think it unlikely that such a big piece could come off and the astronauts not notice it while EVAing...

[bknight]

IMO there is/was no Intelligent UFO that was observed, just pieces of the vehicle that put the mission on a trajectory to the moon.

[smartcooky]

I still believe an SLA panel is the likeliest candidate (so does Buzz, and I've seen what happens if you argue with him !)  While I guess mylar off the LM is also a possibility, I think it unlikely that such a big piece could come off and the astronauts not notice it while EVAing...

The other thing to consider is that there were four panels, so four times the chance that at least one of them might be spinning in an orientation conducive to good solar reflection back towards the Apollo spacecraft. Whatever the truth, I think the statistical probability that what was seen was an SLA panel is hugely greater than any chance it was a spaceship from Alpha Draconis!!