Dust Storm- Opportunity EOM, the end of the beginning of a new era in robotic spaceflight Options

[marsophile]

...solution that requires state to be recorded and used from sol to sol is usually not used in deep fault responses...

Not to mention the fact that flash memory is unavailable, so only measurements from a single Sol could be considered, and the CPU would have to stay on throughout the Sol.

In principle, the rover might be able to autonomously reset its clock if there was enough energy to take images of the sun position but (as the previous post points out) such complex algorithms would be unlikely in fault protection. Waking up every 4 hours is a simple and seemingly adequate solution.

The biggest danger I see from the dust storm is a poor dust factor going into the winter season leading to desperate measures. If I recall, the issue with Spirit was precipitated by over-winter issues that upset the original plan of driving along Home Plate. Hopefully we will get cleaning after the current dust storm but we may also get a second dust storm in the current summer season.

[scalbers]

How severe is this dust storm compared with others weathered by Opportunity? Estimating the total solar radiation in heavy dust conditions is an interesting exercise and the scattered light will be the main contributor when the direct radiation diminishes. I'm trying to model all this with my simulated weather imagery package. A key factor would be how much light gets absorbed for each scattering event (a single scattering albedo of about .90 in green light and .97 in the IR see figure 8). A tau of around 10 would only cut the light down about 50% if absorption wasn't a factor. I can note a Titan analog with a tau of around 8 and estimates of 10% of the visible band light getting through when absorption is factored in. Deimos' formulation in post #28 is reasonable. As mentioned more light in the IR will help for the solar panels. Serpens' YouTube video is pretty impressive.

[mcaplinger]

How severe is this dust storm compared with others weathered by Opportunity?

The worst previous was back in 2007: "Due to extensive dust storms in Mars' southern hemisphere causing record atmospheric opacity levels, Opportunity is currently experiencing its lowest power levels to date. The tau measurement as of sol 1225 is 4.12, resulting in a mere 280 watt-hours of array energy. A tau measurement of 5.0 would result in approximately 150 watt-hours."

https://mars.nasa.gov/mer/mission/status_op...07.html#sol1382

Keep in mind that we have two competing measurements, the tau determined by analysis from Pancam images, and the actual solar production. From an engineering perspective, only the second one is of direct interest. I'm sure they have a model to go from the first to the second, but once you have an actual number for the second you should use it. And of course for any model, you not only have to know the irradiance but also how much dust is on the panels.

[djellison]

I guess the question is: how does the rover decide if it's midday?

It doesn't. Assuming a loss of clock fault - it simply boots up when 2 amps are on the array. The IDD heater is not a significant concern when you're at 2 amps.

[mcaplinger]

Not to mention the fact that flash memory is unavailable, so only measurements from a single Sol could be considered...

While the flash is not available, the rover also has 11MB of EEPROM thst could be used to store state information. I think, for example, that this is where Earth position as a function of SCLK is kept. Without time reference, no HGA comm will work until this can be updated.

[serpens]

How severe is this dust storm compared with others weathered by Opportunity? ..... A key factor would be how much light gets absorbed for each scattering event (a single scattering albedo of about .90 in green light and .97 in the IR A tau of around 10 would only cut the light down about 50% if absorption wasn't a factor......

This may help (or not). https://www.swsc-journal.org/articles/swsc/...swsc150027.html
The maximum tau assessed by Opportunity in 2007 was 5.5. The maximum assessed this time around before she went dark was 10.8 and this may have increased. This doubling of the tau, ignoring the airmass variable means that direct insolation would be 0.005 that enjoyed by opportunity at the height of the 2007 storm.

EDIT. An update by A.J.S. Rayl. http://www.planetary.org/explore/space-top...torm-sleep.html
An interesting extract: “The dust here is thicker than anything I have ever encountered, going back to Viking missions,” said MER Deputy Principal Investigator Ray Arvidson ........It’s dark, like the end of twilight dark.”
Paolo. described it as basically "the difference between a full sunshine day and a full moon night kind of state". Even a minor increase in tau over the 10.8 value and all ambient light would go.

[fredk]

From the latest MRO weather report:

By the end of the week, the storm was nearly planet-encircling. Skies above the Opportunity rover site in Endeavour Crater remained completely obscured each sol.

[mcaplinger]

http://www.planetary.org/explore/space-top...mer-update.html has some discussion with John Callas about the consequences of the mission clock fault on Spirit.

It might be interesting if someone from TPS sat down with him to discuss the recovery of Opportunity in light of that experience. (Edit: I note that there's a little bit of that in http://www.planetary.org/explore/space-top...torm-sleep.html linked upthread.)

[djellison]

"The Martian dust storm has grown in size and is now officially a "planet-encircling" (or "global") dust event."
https://www.jpl.nasa.gov/news/news.php?feature=7164

[JRehling]

Christopher Go is the ace of [superior planet] astrophotography and his latest Mars picture (as of now; his page updates in case anyone is reading this weeks from now) gives an outstanding idea of how devastating this storm is:

http://astro.christone.net/mars/

Looking down on what should be extremely high-contrasty terrain and seeing that blankness might communicate the intensity more clearly (no pun intended) than stats re: sunlight.

[vjkane]

Forgive me, I'm traveling and can't always check the website. Wanted a reply up so I can get email notifications of new posts.

[mcaplinger]

It's about 11:30 LST at Opportunity as I post this, and I see that DSN Now says they are uplinking to MER1 from Canberra. I wonder what they're trying to do? I thought they were in listen-only mode.

[RoverDriver]

I believe they are trying to solicit a beep.

Paolo

[djellison]

The fault modes open a comm window - you have to Uplink to get a response as Paolo said

As a heads up to people watching DSN Now - you may, quite often, see what appears to be MER 1 transmitting to the ground for a few seconds, maybe half a minute. That’s not Opportunity. That’s the DSN getting a false lock on noise from MRO.

Were we to get a response from Oportunity - it would more than likely be a complete 5 minute beep.

[mcaplinger]

The fault modes open a comm window - you have to Uplink to get a response

Really? There's never any attempt to send anything on the X-band LGA autonomously? The fault protection paper implies that there is:

At the next solar wakeup, the flight software schedules one LGA
communication window at a predetermined hour (11:00 LST) to report
to Earth. No UHF windows are attempted because these usually occur
in the early morning or late afternoon, when the available solar
power is low. The vehicle remains in this configuration
(with autonomous shutdown mode active, in receive mode via the
LGA, performing one DTE window per day) until the operations
team reconfigures the vehicle to resume normal operations.

I read that as meaning that it's in receive mode as long as it's powered up and that it tries to send at 11 LST even if it hasn't heard anything. But I may be misinterpreting what "schedules a communication window" means.

In my experience it would be unusual to never transmit autonomously, since that would mean that if there was a receiver failure, you'd never hear anything even if the transmitter was healthy.