Hypothetically, if the low gain transmitter were non-functional, but the receiver and other communication assets (UHF, high gain) were ok, could the rover still be recovered? From a practical standpoint, would recovery be unlikely in that case?

There's only one X-band transmitter (though there are redundant solid-state power amplifiers) that can be switched between the LGA and the HGA. The HGA can't be pointed at the Earth in a clock fault because the rover doesn't know what time it is and therefore where the Earth is. So the HGA path is useless for recovery unless the clock can be updated. See https://descanso.jpl.nasa.gov/DPSummary/MER...cmp20051028.pdf Figure 3-1 on page 17.

In theory both transmit and receive could happen via the UHF. With a clock fault, though, the exact time of UHF comm windows is moving around in a hard-to-predict manner and it's unlikely that an orbiter pass will happen to coincide with one of these windows, though I expect this is being tried.

Hi Oppy, we can at least see you again: https://www.jpl.nasa.gov/news/news.php?feature=7245

Glad to see the old girl... a poignant image if there ever was one!

Full res blend of HiRISE RGB mapped to gray pass, Oppy is centered.

How a Tiny Curiosity Motor Identified a Massive Martian Dust Storm Link

Click to view attachment

Looks like Oppy has taken on a lot more dust than its immediate surroundings (unless the area around it is in darkness and the rover is poking into the light). It would be nice to have a stereo pair---the brain does a great job of combining information from the two eyes.

I don't think that follows, as the color and reflectivity of the rover is obviously different than the surroundings regardless of the dust loading.

https://www.uahirise.org/ESP_056955_1775 says

I wondered if the dust would fall out of the atmosphere at around the same rate globally if a dust storm turns into a global one? Maybe it might be possible to use Curiosity to give some idea of how much dust is settling on the rovers.

Given that there are dustier (Gale and Gusev) environments than others (Meridiani), I would be surprised if that was the case. Even after the 2007 PEDE, the amount of dust accumulation on the two MER vehicles was different. Keep in mind that even a 0.1 difference on the dust factor can have a significant impact on solar array output.

Paolo

The DSN is currently transmitting an UP signal to Opportunity at a data rate of
2.00 kb/sec. Isn't that a little high for trying to send to the LGA?

[EDIT: I guess it is the DSN power level that matters, not the rover's].

From https://descanso.jpl.nasa.gov/DPSummary/MER...cmp20051028.pdf

So it seems very unlikely that they are sending 2K to the LGA. I don't know what they're doing. It's possible that DSN Now gets confused about uplink in MSPA or something, I suppose.

Uplink rate in a fault mode to the LGA is 7.8125 bps

See https://www.cs.princeton.edu/courses/archiv.../mars.rover.pdf

2 kbps is the sort of into-an-HGA nominal upilnk data rate one might expect for many spacecraft. Certainly not what was happening today for MERB.

Click to view attachment

Screen capture from DSN Now this morning.

Could the MER team be trying to rouse the rover via the HGA, on the theory that the LGA is not working? It may be that there was a known occurrence where by chance the HGA was pointed towards Earth.

Is it even possible to communicate using the HGA when the rover is in fault mode?

Sigh. I think a more likely explanation is that this was an uplink to some other spacecraft, and DSN Now got confused.

I suppose it's possible that there could be a switch fault that would preclude connecting the LGA to the SDST, but then I wouldn't expect them to use the highest-possible uplink rate to command, even if the HGA happened to be pointed at the Earth.

The HGA requires a mission clock and knowledge of where the Sun and Earth are in the sky for pointing the HGA. It's pretty safe to assume that the clock faulted, the rover hasn't woken up yet as the sky has cleared to levels to where a healthy and clean rover should automatically power up and start sending beeps on schedule. That is, if the clock didn't fault...in a perfect world. So, as I understand it, once 1.1 amps hits the array, the rover should wake up and start beeping on the only antenna that doesnt need any knowlege of orbiter overpasses or where the Earth is in the sky. That is the LGA, which is omni-directional.

By the way. I've been watching DSN now quite a lot lately during the attempts. Manage your expectations with it. Take everything Oppy related with a grain of salt. Don't get to excited if something appear's like Oppy is talking. These false alarms further highlights it to be super cautious. Any news of possible com with Oppy will come from the rover team and a press release. Not DSN now....

It is not.

This was not a 2kbps uplink to Opportunity.

It was some idiosyncrasy in the way the various antennas report data to the server that collates data into the form DSN Now uses.

I know it's tempting but please stop trying to infer something about recovery efforts via DSN Now. It's not what it was designed for. It's going to be wrong more than it's right.

Source : I work on Opportunity and worked on DSN Now.

"Amateur" observations regarding this question have been made during the 2018 dust storm, but don't seem to be publicly accessible, yet.

https://twitter.com/dsn_status/status/1046058741974609920

DSS 36 carrier lock on Opportunity
Frequency: 8.4351GHz
Signal strength: -164dBm
IDLE OFF 1 MCD2
8:26 AM - 29 Sep 2018 from Paddys River, Canberra

Ticks more of the criteria set in this thread, but just a carrier lock.

Hopefully, this means we just got at least 1.1 amps out of the solar array.

Here's hoping this is a start to recovery. No way a sure thing yet, but fingers and toes all crossed...

-the other Doug

Likely another false carrier lock. Like I said with DSN Now above, take anything Oppy related with a grain of salt. To be honest, I'd just pretty much ignore the Opportunity DSN status twitter messages because of the high potential for false locks with other orbiting assets.

Just for curiousity (the mental attitude, NOT the robotic craft), what help could the currently-orbiting assets be to this effort? They all have there regular jobs to do, and limited capabilities, and limited time in view of Opportunity, but their one-over-R-squared advantage is significant over earthbound resources......

DTE LGA passes have been used in the past and the DSN is well capable of detecting and carrying those passes. Either the rover has enough energy to start a comm pass or it does not, it is binary, not analog where the transmitted power varies according to the energy level.

Paolo

This has been discussed several times in this thread, look for "UHF".

The bottom line is that in this particular fault it doesn't help very much.

https://en.wikipedia.org/wiki/Snowdrift
If there is any wind when the dust is being deposited, then perhaps it would depend on the local topography, like a snowdrift. Some kind of barrier that abruptly slows the wind might form a relative drift. For example, if the rover deck were tilted in the windward direction, then it might receive a lot of dust.

You are correct, the local topography greatly affects the dust deposition but your example is backwards, I think. The side facing the wind sees the highest pressure and wind speed, therefore lower dust deposition. As an example, if you remember the dune field we have traversed before and after Victoria, had an asymmetric dust deposition. Even when the crest was about 20cm taller than the trough there was a noticeable difference in dust. This is why we were usually driving on the West side of the trough, and why the Sol 833 embedding happened (Jammerbugt).

In fact, the current rover position is probably one of the best possible to expose the deck to cleaning events. If you look at the surface (before the PEDE) there wasn't much dust drifts around.

Paolo

Probably a public announcement on JPL or NASA sites. Also, if you see me heading for the liquor store, that might be a good sign.

Paolo

That's what I figured, but the trouble is that there are seemingly so many ways the news of Opportunity waking up could be disseminated: could it be a rover team member's social media account, a press release from NASA/JPL as you said, some lucky person looking at DSN Now at the right moment, or a 'leak' to a space news reporter?
There's no technical disclaimer on the DSN Now interface, and I'm not sure what the NASA PR rules are about private social media accounts apart from 'opinions are my own'. The chance of false alarms are still too high...

As far as I know the automated DSN twitter account is basically getting the same information as DSN Now. Many of us have said over and over again that this is not a reliable source of information with regard to the Opportunity recovery, and you can appreciate that there might be a certain amount of frustration when these caveats are ignored.

I've tried to figure out what an unambiguous detection might look like on DSN Now, but the initial contacts will likely just be beeps (carrier only) and with just this, my criterion of actually seeing data flowing at 10 bits/sec will never be met. Read https://descanso.jpl.nasa.gov/DPSummary/MER...cmp20051028.pdf 5.1.6 X-Band Carrier-Only Beeps for more information. It may be that once the recovery is well underway, DSN Now will be a viable way of seeing how it's progressing, but not initially.

The bottom line is that an official announcement is the only reliable way to know if something has been detected. AFAIK, team members are not supposed to be unofficially posting status information on social media. I don't think the team will sit on the news for any length of time, but it has to be coordinated with JPL PIO so I wouldn't expect it to happen over a weekend.

Perhaps one way of ruling out false contacts might be to look at the Local Solar Time at the Opportunity location for when they occurred. As an example, if my calculations are correct, the 3 most recent candidate "beeps" occurred at 13:28:42, 12:50:19, and 13:45:57 LST. (I assumed the times given by the twitter reports were Pacific Time.) If the onboard clock were still working, then (according to the fault protection documentation) the spontaneous beeps should be at 11:00:00 LST.

The clock has almost certainly faulted, and even if it hasn't, I don't think one can presume anything close to the level of accuracy that you're suggesting.

The fact that there is no public source that says how long a particular signal is in carrier lock makes it impossible to tell a short transient from a longer, more plausible actual contact.

I see people are still trying to use DSN Now as some way of detecting an Opportunity recovery. Some of these points have been made earlier but just so people are clear....

https://twitter.com/dsn_status
This is an unofficial bot written by the awesome Russ Garrett. It says so right in the accounts profile. It is not a NASA account. It is simply a bot posting every time it detects a change to the XML file that drives the DSN Now website.

I get it - we all want to hear from Opportunity - but believe me, you've not going to figure it out with DSN Now. I worked on it for years, and it is a victim of many idiosyncrasies in how the DSN operates, how the network reports its status internally and - to be brutal - a lack of resources to engineer a level of robustness into its pipeline to avoid all those idiosyncrasies.

Seriously people - I know watching DSN Now like a hawk may feel like a way of getting ahead of an official press release, but you're largely wasting your time.

The way we're going to hear that Opportunity has been heard from is via a NASA and/or JPL press release. Not an overly enthusiastic fan reading too much into DSN Now.

ADMIN MODE: This thread has become beyond overheated, and we're turning the flames down right now. Three particularly inflammatory posts hidden.

New info/rules for this discussion to continue:

1. It has been stated. And stated. And stated. REPEATEDLY...that the DSN Now interface cannot be considered an authoritative source to determine whether or not any sort of signal has been received from Oppy. Therefore, there will be no more excited future posts claiming to have seen such a signal nor passionate defenses of one's 'find'.

2. There has also been an exhaustive explanation from persons in positions to know the many technical reasons why this is, as well as the various possible failure modes that are causing the silence (all of which are at this stage possibilities, not confirmed hypotheses). Nobody else here is in a position to question their opinions.

3. Unless and until NASA/JPL makes an official announcement that Oppy has been heard from we will not know anything at all. If anyone begins claiming some sort of conspiracy about this they will be immediately and permanently banned.

Most of all, let's keep it civil. Many people here are, naturally enough, emotionally invested in this situation. Let's please not let that concern and frustration overwhelm our good sense (and I really don't wanna hear any "but s/he started it!" cries of protest--just knock it off. Now.)

Back to our regular programming.

Bravo Zulu nprev. Not before time.

My relationship with JPL media has always been difficult at best. I'm pretty sure that if I made an anouncement before they did, it would be my last post as a JPL employee.

I am also sure that JPL/NASA would not hide or delay such news. Yes, there will likely be some handshake with teh rover to make sure she's still up and running. Mars works slowly. Be patient, and watch where I'm heading ;-)

Paolo

Me and I'm sure all of us here wouldn't want that to happen to you Paolo.
So yes, please don't.

https://static.uahirise.org/images/2014/det...5408_1775-1.jpg
Happier times for Opportunity! Hirise image from Valentine's Day 2014.

Click to view attachment Click to view attachment

Oppy seems much clearer in the old Hirise. We can see a shadow cast by the rover.

Is the lesser clarity in the new image due to lighting, or dust? Of course Oppy is now in a valley sloping to the East, while the Sun is in the West at 3 pm local time.

There's about a 30 degrees delta rover attitude between the two pictures, almost entirely to the East. Same holds true for the terrain. If you look at the Sun elevation angle for the two pictures, you can figure out the difference in lighting conditions.

Paolo

Perhaps snow was the wrong analogy; being pelted by rain or hail might be a better one. The dust is already falling so the carrying capacity of the wind may not be the significant factor. Instead, the angle of the fall (modified by the wind) may be the important issue. If the trajectory of the falling dust is exactly perpendicular to the plane of the tilted deck, then the deck will pick up more dust than if it had no tilt.
I think, surprisingly it may even pick up more dust than if the deck was level and the dust was falling staight down. The reason is that the angled dust will be packed the same on a level deck as if it were falling straight down, and thus more tightly on the perpendicular deck.

Click to view attachment

The size of the dust grains is on the order of one micron. Therefore aerodynamical considerations will be the most relevant ones regarding dust settlement. Air is moving parallel to surfaces. and so do mostly the aerosols, not perpendicular like rain or hail. If it would be otherwise, the dust would have settled within hours after the storm, and wouldn't have been able to spread globally.

You make a good point. However, if the local wind is slow enough, in the tenuous Martian atmosphere, then the ability of the wind to push dust uphill on the rover deck may be limited. One would expect a critical wind speed below which dust settlement will be more like a rain of dust. Stronger winds at high altitudes may have kept the overall dust from settling more quickly.

Also the tendency of Martian dust to form aggregates of size ~100 microns or more may be a relevant factor. See
http://www.marsjournal.org/contents/2010/0...s_2010_0005.pdf

Theory is nice but have there been any wind tunnel experiments to investigate dust deposition under
simulated Martian conditions?

Strong winds don't keep the dust from settling, although turbulence does; they just change where it falls. For winds of 1 mm/s or more, the dust moves much more with the wind than down, even though the average velocity is down in the post-storm environment. Look at the cal target post to see evidence of dust moving with the wind.

The large aggregates form on surfaces not in the air, so they matter for cleaning events. But we see cleaning events. Aerodynamics matters quite a bit there too, since the wind on a rough surface (rover deck, not necessarily solar cells) is much less at 100 microns than at 10 meters.

Some quotes from
http://www.marsjournal.org/contents/2010/0...s_2010_0005.pdf



Seems to imply possibility of growth while suspended in the atmosphere.

Suggests a mechanism.

Nevertheless, dust will prefer to settle and remain at locations, where wind velocities are lowest. That's usually on the lee side of an obstacle, especially in concavities.
Your rain or hail analog would apply to saltating grains. But for a tilted surface, these usually rounded larger grains tend to roll downslope, and will mostly end up in concavities, too.

I don't like the rain analogy--nothing falls like that. Rather than further picking that nit, here's what I see as ways stuff does fall.

(1) There is the background of globally homogenized atmospheric dust. The Lemmon et al. (2004) reference above, and many others before and after, have put that dust in the vicinity of 3 micron diameter. This is in no way a lower limit. That is a measurement of the dust, while it is suspended, in bulk. The 3-micron number is a cross-section weighted mean diameter: the vast majority of dust particles are smaller than this, and some are significantly larger. The width of the distribution is difficult to pin down, and even then it would be an 'effective' width. One cannot say precisely how many 20-micron diameter particles there are (but not many).

(2) That dust (from 1) looks a lot like the globally homogenized post-storm dust. After the 2007 storm, when dust had mixed around the planet about as much as it was going to, and lifting had stopped, the dust settled (as opposed to 'was advected away'). At both rover sites, Lemmon et al. (2015) the dust opacity decayed exponentially with a 43 sol timescale (1/43 of the dust was removed each sol). That's close to the Pollack et al. (1979) values for Viking or 51 sols. We know the timescale for dust falling. We know the spatial scale is around the 10-11 km scale height. So the characteristic mean fall speed has to be in the ball park of 3 mm / s (I think I somehow got 10x lower, before). Sure, it is different high vs. low and day vs. night, but the average sedimentation speed cannot get far from this. Since the start of July, this is what has been happening, based on close analogy with measurements from the Martian surface in similar circumstances.

(1) and (2) describes dust falling like Martian dust. I don't have a good analogy. I don't have data, but I'll assert dust in my living room falls much faster. Volcanic dust could ... but the fine component that usually falls literally as rainfall far from the eruption.

(3) At the other end, there is ballistic material. This is saltating sand. Lots has been reported. Maybe during the storm, this scoured the already clean rover deck. Maybe it piled up on parts of the panels. When the wind stopped blowing, this stopped within seconds.

(4) In between, you have the gradation of stuff falling at a terminal velocity that is significantly greater than eddy speeds. Maybe one could say it falls like snow, or maybe volcanic ash. (4a) Some stuff is big when lifted, but not sand sized. It has a short residence time in the atmosphere, so it does not contribute significantly to the 'global' dust. It is likely not there most of the time. But Opportunity was in the middle of lifting areas. Did big stuff fall out as dust that settled by one to a few km in hours to a few sols? Possibly (personally, I think it is quite likely). (4b) Some stuff may have grown to 100-micron sizes and then fallen. Large aggregates fall slowly (snow, not rain). If the fractal dimension is ~2, their cross-section grows as fast as their mass, so they don't even speed up. If the fractal dimension is ~3, it falls like rain; and if this is an important mechanism, the skies clear much faster than we see happening on Mars. I guess one may speculate; but I have not seen any evidence of this stuff in the atmosphere, or clear examples of stuff that fell out (let alone that this is an important mechanism). (4c) Stuff certainly gets to 100-micron sizes on surfaces, likely growing there but maybe falling there. (I figure this is a good thing, as this stuff sticks up more into the wind and becomes easier to clean.)

But overall, there are lots of mechanisms that get the deck dusty as the various sizes interact with different winds and terrains. There are many unknowns, since we've never had active measuring happening inside that kind of storm; MSL didn't see the same activity. I'm not sure it is worth drilling deeply into one unknown without rover data.

http://www.planetary.org/explore/space-top...pportunity.html
A.J.Rayl's Planetary Society update, Oct 4.

Selective quoting on your part?



The fact of the matter is that not much can be determined from the HiRISE image, but clearly people want to believe that the rover is very dusty, since that's an explanation for why it hasn't woken up yet.

I could say the same. The bulk of opinion expressed in the article favored this view, although there were caveats.

Of more interest are the detailed descriptions of the recovery attempts.

Taking your words out of context...
This will be the case, even if only a fraction of the atmospheric dust column settled on the solar panels.
Let's hope for a few gusts in time.

As I understand it, for a global dust storm the tropics and the low to mid latitudes are the sinks for dust deposition, so as far as dust fallout is concerned Opportunity is pretty well positioned.