I'd have guessed no dimmer than mag 5 or 6 on the basis of nothing in particular. We have no real requirement to image stars at all, and the only reason I'm interested is to help constrain the accuracy of camera pointing and optical distortion knowledge.

We didn't do any lossless high-TDI imaging during EFB; only EFB17 (which is full of particle hits from the Van Allen belts) was taken lossless. But we have lots of lossless cruise imaging that I could make available.

I could fix that problem in Photoshop in about 5 seconds

I tried to figure out how many pixels across an Earth image would be, but couldn't find the focal length or the FOV of these cameras. That could be guessed from the sizes and ranges of the hardware, but I'm too lazy.

I think that was a joke.

While it would be interesting to use image processing techniques to generate the maps (define a model of the wheel, extract the image geometry from the SPICE kernels, have a camera model, map-project and mosaic, etc.) it would be simpler in the short term to do this by eye.

AFAIK, these are all low-res video versions of the original source images, so better quality should be out there somewhere. A little saturation at zero phase would be almost inevitable given the contrasty scene.

As to color, the Apollo astronauts found this to be pretty subjective and phase-dependent, but the consensus was for at least a hint of brown ("mouse gray" and "mouse brown" are often used, whatever that means -- there's a lot of variability among mice too.) White-balancing off the rover's white HGA should work well.

grabbed this from NSF:

Wow, nice work. Seems convincing to me.

Oh, I get it, you're saying that the Viking cal targets worked better than the MER and MSL cal targets. That could very well be true, at least in some ways. Perhaps for Viking having a clean calibration target was critical (presumably true given the embarrassing confusion with the sky color shortly after landing ) I'd argue that modern camera systems are stable enough that in-situ color calibration is much less important, but I am admittedly biased.

Viking also had the luxury of having an EDL system that left the deck much cleaner than MSL's did. I'm not sure how well Viking-style targets would fare on MSL, but there are color swatches on the Chemcam cal target that could be examined (I don't know the specifics, maybe they aren't colors); I think there are a few Mastcam images of those.

That's what we did with the MAHLI cal target, and it's arguably even dirtier than the Mastcam cal target because of landing dust. Also, the science team insisted on horizontal surfaces at a specific location to meet their requirements on phase angle. So vertical surfaces are not a panacea.

Thanks, Gerald.

I'd say it was an overstatement to say that the magnets weren't working at all on the MSL cal target. Certainly there are clearish spots on all the color chips and the gray ring, so I think the claim that the magnets would make things worse is just false. I have to mention that if this issue was being discussed before launch, it didn't filter down to those of us doing the work. And the cal target is, IMHO, nice to have but in no way critical to anything.

Making things magnetic, BTW, means that they can't be mounted near anything that could be affected adversely by the magnetism, which is another constraint that has to be considered when adding a target like this.

The Juno EFB press conference is at http://www.youtube.com/watch?v=gtvsiRPzcXU

The first image, a triplet of EFB10, 11, and 12 produced at MSSS, was apparently not deemed worthy of Planetary Photojournal, nor is it on missionjuno, so here it is. Still not perfect, but not too bad.

My original draft caption:

These three Junocam images of Earth were taken during Juno's close flyby on October 9, 2013. The leftmost was taken at 19:08 UT at a altitude of 5741 km; the center was taken at 19:11, 4001 km, and the right at 19:12, 3197 km. The center image was taken using Junocam's narrowband methane filter; the other two are combinations of the instrument's red, green, and blue filters and approximate natural color. Each image is a mosaic of 82 individual frames taken as the spacecraft spun; these have been composited and remapped by ground processing.

The first shows the southern two-thirds of South America. As the spacecraft moves eastward, the Chilean coast and the snowy line of the Andes mountains recedes toward the limb. The third image has a good view of the Argentinean coastline with specular highlights off the Rio Negro north of Golfo San Matias, as well as cloud formations over the continent of Antarctica.

I referenced that thesis a long time ago (can't find the post now) but there is some controversy that the results are actually applicable to the martian environment. At any rate, the target is what it is.

Certainly. One way to get a better apples-to-apples comparison would be to produce a Mastcam RGB composite from the narrowband filter images in that set, since those are very similar to the MER bandpasses. I presume the image shown is just the Bayer image.

Also, the phase angles were quite different between MER and MSL, as you can tell from the gnomon shadows.

We have no plans to do anything with Junocam with regard to asteroids.

Because it costs money, and in a world of finite resources, there has to be cost-benefit analysis.

The Masursky images count as dots as far as I'm concerned.

MARCI had no blankets of any kind, so it looked exactly like the picture at http://www.msss.com/all_projects/mars-clim...biter-marci.php -- most of the external surfaces were clear-anodized aluminum, and the center housing sections were painted with white thermal control paint.

The pictures at http://en.wikipedia.org/wiki/Mars_Climate_Orbiter are the best I know of that could be publicly released but they don't show the blanket configuration very well. IIRC correctly, most of the nadir deck was blanketed with black Kapton, but the battery louvers were covered with silver FEP (shiny tape.)

I think there was a photo on the cover of AW&ST but I don't have a copy readily available.

Galileo predates the frames kernel concept, and it seems likely that no one has been motivated to go back and build them from scratch (we didn't have FKs for most of MGS either, but they were generated in 2007.) Some of that information is in the I kernels for the various Galileo instruments, though I didn't look at the C kernels to understand which frame(s) were in there. Historically image processing was done with the Euler angles in each image file.

Because they would weigh more and be less compliant; the wheels are basically the only shock absorbers in the system.

I have to say I feel a bit conflicted about this thread. On the one hand, some posts seem to be armchair engineering suggesting that there's something wrong with the system. On the other, some are just mostly-baseless cheerleading. I've tried to stay in between those two places by talking about the real engineering to the extent that I can, but maybe we've reached the point of diminishing returns on this topic.

I assume (with no evidence to support it) that the wheels are 7075 alloy, which is somewhere near the upper end of aluminum alloys for fracture toughness -- http://en.wikipedia.org/wiki/Brittle_strength . http://en.wikipedia.org/wiki/Fracture is a useful intro to various types of fracture; see "ductile fracture". I'm not a mechanical engineer or a materials scientist and a hole is a little surprising to me too, but I'd rather see a clean hole than a big propagating rip.

To anticipate a question, aluminum is less subject than say, steel, to low-temperature embrittlement. See http://www.keytometals.com/page.aspx?ID=Ch...e=ktn&NM=23 -- "Below zero, most aluminum alloys show little change in properties; yield and tensile strengths may increase; elongation may decrease slightly; impact strength remains approximately constant. Consequently, aluminum is useful material for many low-temperature applications."

To sum up (note that this is all my opinion derived from public information because I've intentionally not looked at any project-internal sources on this): yes, there are holes in the wheels. Some level of wheel damage was clearly anticipated by the designers. There are a lot of tradeoffs in the MSL wheel design and it may well have not been feasible to make wheels that were impervious to puncture. Imaging the wheels is being done, presumably to assess the amount and evolution of damage. Exactly what the level of concern is, if any, is something for the project to say.

It's not obvious to me that the Juno payload would really provide much useful data from any plausible asteroid flyby; at least Junocam is not well-suited for such an encounter.

I'll note that neither Cassini nor New Horizons returned any asteroid images that were anything but dots IIRC, and they were far more capable of flyby science.

I would hesitate to call this science. At best we get a crude idea about rock size statistics, cruder I expect than what you could get just by counting rocks in images.

Of course I wasn't counting you, Doug.

I'll confess that I've made minor engineering changes just to stop baseless concerns, so let's look at the details. If the wheels are 0.5m in diameter and 0.4m wide, then roughly speaking the outer surface volume is pi*0.5**2*0.4*0.75e-3 = 235 cm3 and its mass (aluminum density is about 2.7 gm/cm3) would be about 600 grams. Doubling the thickness would increase the mass to about 1.2 kg per wheel (times six of course) so the overall mass increase would be about 3.6 kg -- nearly twice the mass (for example) of two Mastcam camera heads. [edit: of course each wheel's mass is greater than 600 gm, this is just a rough cylindrical approximation of the mass of the 0.75mm "skin" of the wheel. For reference, 0.75mm is about 7x thicker than a typical Coke can.]

However, I don't see much evidence that anyone actually read the viewgraphs I linked to. It's worth remembering that unlike MER, MSL relies on the wheels to absorb not only driving loads but landing shock, and the wheels may have to elastically deform a fair bit in the process. Making the wheels thicker would reduce their ability to do so; I'm not sure by how much, but it could be a concern.

Did you read the viewgraph package referenced in http://www.unmannedspaceflight.com/index.p...st&p=200198 ?

Other than that, I don't know of anything. There are some useful quotes in http://news.discovery.com/space/rough-rovi...tear-130522.htm (from May 2013)

In my experience, science teams are no more immune to having concerns about things outside their area of expertise than any other group.

The Spirit description was less than crystalline to me, but I think the wheel problem was more a cause than a symptom of that bus imbalance (if that's what it really was.)

In all honesty, though I'm probably supposed to understand this, I'm not certain what the advantages of a balanced bus are. I think it just gives increased visibility into current paths. I do know that the low side of the bus could be completely shorted to chassis and our instruments would work just fine -- in fact, that's how we usually operate them on the bench.

Technically chassis ground is referenced to the actual surface (more or less, though if you were to drive a metal rod into the surface of Mars and measure the impedence to chassis ground I'm not sure what you'd get), so it's not really floating. It's more that the low side of the battery is intentionally not at the same voltage as chassis ground.

Appendix A of https://standards.nasa.gov/documents/detail/3314876 shows the Cassini balanced bus, which is similar.