From Concepción to the "Twin Craters", and beyond... Options

[Stu]

Not necessarily. **** happens. She still sent back some nice parting shots of Concepcion...

http://twitpic.com/17yy6c

[Phil Stooke]

Worst ... artifacts .... everrrr!

Phil

[Stu]

Having a really hard time making anaglyphs out of them...

[djellison]

A ratty UHF comms pass ( perhaps with the UHF antenna to orbiter line of sight being interrupted by the LGA or PCMA ) and it on'y takes a few dropped packets to corrupt lots of pictures.

Note that the corruption is in lots of images of a wide range of time. They are not all taken today, for example, inferring a problem with transmission or receipt rather than the actual data or the rover itself.

[Stu]

Maybe a family of gorillas wandering past got too close and accidentally knocked the antennae out of alignment...

[Tesheiner]

Nah! Too far from their niche. Oh, perhaps we're talking about the "Gorilla Meridiannii"; that's a different species.

Now, back to business: a 70+ meter drive SW was performed some hours ago. Waiting for the pictures...

[Louise Sharples]

A ratty UHF comms pass ( perhaps with the UHF antenna to orbiter line of sight being interrupted by the LGA or PCMA ) and it on'y takes a few dropped packets to corrupt lots of pictures.

I'm sure I read in the MER technical guides that UHF passes are always error-free (which if true, points to an orbiter-to-DSN issue). I hope this isn't due to the loss of DSS-14...

[djellison]

Then you've read wrong. Whatever the problem was, it was clearly temporary as the most recent down link was fine. The UHF passes are pretty damn reliable, but they're not perfect.

http://an.rsl.wustl.edu/mer/merbrowser/bro...=res&m=MERA

Four CSV's at the bottom of this page are of UHF passes and have a data quality field, you can see many data dropouts within them.

[Tesheiner]

It's impossible to warrant zero errors on any kind of electromagnetic transmission, so "error-free" can only mean that errors are detected and not propagated.
Besides, I'm pretty sure that this "error-free" (if true) applies to the telemetry packets exchanged between the rovers and the orbiters; we are not talking about image files but only about the chuncks that will later on be assembled in a file. You may have error-free packets but still only, say, 10% of the packets making an image file correctly transmitted.
Now, with all of this into account, try to imagine how a heavily compressed JPEG picture will look like when 90% of data are missing and the 10% which are there has no errors. Perhaps like this: http://qt.exploratorium.edu/mars/opportuni...LNP1665L0M1.JPG

[Louise Sharples]

Four CSV's at the bottom of this page are of UHF passes and have a data quality field, you can see many data dropouts within them.

Indeed, but the data quality field suggests that '1' could represent DSN issues:

"Flag which indicates data quality: (0 indicates valid, 1 indicates bad). Data may be flagged as 'bad' due either to telemetry indicating a bad receiver condition or to telemetry integrity checks indicating errors in telemetry record from ODY to the DSN containing the measurement data."

[Louise Sharples]

You may have error-free packets but still only, say, 10% of the packets making an image file correctly transmitted.

Very good point.

[djellison]

Indeed, but the data quality field suggests that '1' could represent DSN issues:

If it were a DSN issue, then we would likely have heard about problems with MRO, MEX and MODY downlink - not just Opportunity.

It would be most strange for a DSN issue to interject occasionally, within the downlink time of the packets from MER UHF passes.

[Deimos]

Thanks to all posters for this--the good news is I would not have known about it unless I happened to check here. I have forwarded the concern and included it in my downlink report. In a spot check, I see the affected images as being associated with (I cannot speak to causality) the images being reprocessed into the right sol. So, good images exist, and I hope the problem (late) in the pipeline will be resolved soon.

Edit: PS, got a good laugh about UHF passes always being error free... I agree with most of the commentary following that. In theory, all bit errors are trapped and do not propagate, except some small fraction. In practice, there was a time when errors got through all the time. And the images then looked just like what is at Exploratorium now. Since the on-board compression is (usually) a wavelet based one, simple dropouts look different (missing or blurry rectangles) from this and from some JPEG errors.

[ElkGroveDan]

simple dropouts look different (missing or blurry rectangles) from this and from some JPEG errors.

Ah...in (nerdy) layman's terms those would be the Borg ships we occasionally see, as compared to the monochrome bed quilt above.

[djellison]

I'm trying to think of the various times we've had few, borked, or no images - apart from ODY safe modes, most of the time it's been problems on the ground with scripts, processing etc rather than a problem inboard the spacecraft.