https://mars.nasa.gov/msl/mission/instrumen...onsensors/rems/

Maximum daily ground temperature from REMS now above freezing. This suggests a clearing at least at the Curiosity site. Being a worry wart, I am now wondering if, ironically, Opportunity might overheat the warm electronics box while in fault mode with no human supervision.

There is no risk of Opportunity overheating. That would require an amount of power than would guarantee reliable communication with Earth.

As a side note, those conditions are above the triple point aren't they? Above 611 pascals and 0ºC during the day.

It's a sol-average pressure so you can't tell if the triple point was exceeded at some point diurnally, not that it would be so amazing if it was.

Even of it is the important variable is the absolute humidity. The actual amount of water vapour in the atmosphere so in this environment being above the triple point for a brief period would be of passing interest only.

I wonder if we will get another twitter/internet false alarm today

https://www.jpl.nasa.gov/news/news.php?feature=7227

"When the tau level [a measure of the amount of particulate matter in the Martian sky] dips below 1.5, we will begin a period of actively attempting to communicate with the rover by sending it commands via the antennas of NASA's Deep Space Network. Assuming that we hear back from Opportunity, we will begin the process of discerning its status and bringing it back online........

.....If we do not hear back after 45 days, the team will be forced to conclude that the Sun-blocking dust and the Martian cold have conspired to cause some type of fault from which the rover will more than likely not recover," said Callas. "At that point our active phase of reaching out to Opportunity will be at an end. However, in the unlikely chance that there is a large amount of dust sitting on the solar arrays that is blocking the Sun's energy, we will continue passive listening efforts for several months."

Reading this article a quote stuck out:

Can't MRO just take a picture? I can guess that HiRISE is either in the wrong orbit to attempt imaging, or the resolution isn't quite high enough to resolve the rover as dust-covered or not, so it's not worth bothering to do? Would the surface be visible from orbit by now?

Have you looked at the images of Opportunity already taken by HiRISE? They are useless, IMHO, for assessing anything about the dust loading.

I think the answer is yes. AFAIK MRO is in a sun-synchronous orbit, so it should pass over every part of Mars in due course. It used to pass always at 2pm local time, but that may have changed. Even if the dust completely settles, there should be only a couple of microns of dust cover (as discussed in a previous post). I can't believe that would blanket the terrain in a way that would make the rover invisible. The only caveat I can think of is that Oppy is on a slope, which may help rather than hinder. IMHO, the only scenario in which Opportunity should be unrecoverable is if some combination of fault modes conspired somehow to place Oppy in an infinite loop of recovery efforts.
[EDIT: Evaluating the dust loading is a very different matter. Maybe it might be possible to look for a glint (specular reflection) from the solar panels?]

I suppose you may not need to resolve Oppy. In principle I could imagine comparing images of Perserverance Valley now with images before the storm under the same lighting conditions, and looking for signs of increased dust on the ground more generally. In principle.

In practice this sounds hard if not impossible. Can images at sufficiently similar lighting be obtained, especially given the changing season? And a current tau above the pre-storm level will surely confound a fair comparison due to the atmospheric dust contribution. And it's not clear how much of an increase of dust cover on the panels would be implied by some increase on the ground, due to the different surface characteristics.

I think that's not possible given the orbital geometry; given the low tilt the imaging would have to happen around local noon, and MRO is in a roughly 3 PM orbit.

The one time we’ve seen a ‘glint’ via HiRise was off Spirit years after it died. And it was just lucky. I don’t believe it can be used quantitatively.

There is a huge back catalog of dust factor and tau data that’s been collated by people here.....one could quite easily see when cleaning events occur by plotting dust factor against Ls and looking for periods of general improvement.

I think if an orbital pass was chosen to be about 22.5 degrees to the east of Opportunity, the geometry might be about right to hope for a reflection, since 3pm should mean a sun angle of 45 degrees from the zenith. Of course it would still take careful planning and a lot of luck.

I think that would be way off nadir, since from the MRO orbit the limb is only about 27 degrees of longitude from nadir. But I haven't studied the geometry carefully, and if there was an observed glint from Spirit there must be some way to make it work, though I don't remember what Spirit's tilt was.

However, I still argue that it's not diagnostic at all anyway.

Well we know that Opportunity is in a good position for panel cleaning events which is a plus. I would have thought that the real danger period would be as the dust settles and minimum temperatures start dropping while power levels are insufficient to recharge the batteries for heating.

Is it possible that the same thing could happen in reverse? That a low bit/sec signal from Opportunity might go unnoticed because it is misidentified as being from MRO or another mission? Something like this, for example:
Click to view attachment

No - 11b/sec on MAVEN is a regular LGA telemetry only check in. Moreover - in the same way we can go 'that's a false lock on MRO while looking for MERB' it's also similarly obvious if there's a false lock on MERB when looking for something else.

The data rate for Opportunity in various fault modes would also be unique compared to other Martian spacecraft.

Recommended reading - the DESCANSO Design and Performance Summary Series

https://descanso.jpl.nasa.gov/DPSummary/summary.html

Being "in lock" is only a very early step in the whole decoding process that ends with digital packet data being produced. If a signal makes it all the way to the end, it has a unique spacecraft ID in it AFAIK, and shouldn't be confusable with anything else; even without the unique ID it's hard to confuse one spacecraft's packets with another's.

In listen-only mode, signals are recorded in wideband, not decoded in real time, and can be combed through later in much more detail than real time will permit. So if there's a signal in there, it will be found.

Apart from the luminance, the color spectrum might also provide useful information on the combined attenuation due to the tau and the dust factor. If a glint could be obtained, even if it proved not to be diagnostic, I think the general public might be excited by the daring and audacity of the attempt.

However, the existing tilt of the rover (is it known?) might render the task impossible. A tilt in the wrong direction would be doubled in terms of the needed offset to get a reflection.

The exact pitch/roll/yaw are known.

From A.J.S. Rayl's latest report:
I'm sure we're all looking forward to seeing Opportunity, even if it remains silent at the time of the imagery.

Maybe a lot of people don't realize that because it's never been written down anywhere publicly before now, at least as far as I know.

It's good to finally read some detail on the active/passive distinction. From the report:Still, "probably" and "shouldn't" aren't definitive. Is anyone aware of a scenario where we could regain contact actively but not passively? (I guess we don't have the mistake in the fault protection settings that Spirit had, so that shouldn't be a problem.)

Is this the issue? (From the MER update from 2010 that you cited above.)

https://mars.nasa.gov/mer/home/

The 45 day period of "active listening" has apparently begun.
Reevaluation at the end of that period?

According to the latest article i've seen "It's now sending commands multiple times per day", now if it were only possible to pull the queue or history list on the DSN page..

Best way to see the DSN Now history is to look at the timeline of DSN Status - https://twitter.com/dsn_status

It's not an official NASA thing - but does the job.

Was this a hit? (Now 10:25pm PDT.)
https://twitter.com/dsn_status/status/1040813778147926016

Would have been around 11am LST at Opportunity location.

Thanks Doug for that link.

Just now I noticed:
Click to view attachment

Just now, there isn't a live signal or carrier, but DSS 35 is sending a data signal to Oppy.

The frequency is different to MRO too?

Different from MRO, but looking at the history, Odyssey's frequency is almost the same (8.4067GHz vs 8.4068GHz above), so not sure if there is some possibility of confusion there for a carrier lock.

Yes. I think we've been mistaken again, this time with Odyssey rather than MRO, here's a tweet from 16th August https://twitter.com/dsn_status/status/1030026880068595712

Here are the results when you search the DSN twitter timeline for Opportunity

https://twitter.com/search?f=tweets&ver...us&src=typd

Most of the frequency's for Opportunity are 8.4358GHz

edit: confirmed false alarm : https://twitter.com/AstroStaab/status/1040845967233150976

Were any false alarms during the Spirit listening campaign? The DSN Now site didn't exist, so it wasn't all over Twitter if any happened, but the same orbiters were around the planet with the same potential for "mimicry".

And what exactly will a DSN signal from Opportunity look like on the DSN website/twitter feed? Such as signal strength, data rate, frequency etc?

If you look back to May 2nd we see this:

DSS 24 carrier lock on Opportunity
Frequency: 8.4072GHz
Signal strength: -125dBm

With the next tweet being:

DSS 24 receiving data from Opportunity at 142.2kb/s.
IN LOCK OFF 1 MCD3

Which is quite similar to what we saw this morning, minus the data tweet ofcourse.

The bit rate would be very low for starters (<10 bps IIRC). If you don't see "receiving data" then I would assume it's a false alarm.

If a real signal is seen I don't think the team will keep it a secret.

The signal strength should be consistent with the low gain antenna (LGA) on Opportunity.
For comparison, this shows an example of an LGA comm from Maven:
https://twitter.com/dsn_status/status/1040572487174639617

Here is an example attributed to Mars Odyssey with an even lower signal strength:
https://twitter.com/dsn_status/status/1040558512282259457

This old one from Opportunity is almost identical to last night's.
https://mobile.twitter.com/dsn_status/statu...07412912128?p=v
I assume without data being transferred, there is no way to verify, but we can hope that initial abortive attempts might be indications of Oppy struggling to come back...

IIRC, false alarms are not only possible because of false contacts that end up being chatter with other assets in the region. I recall that there was a repeated set of false alarms during the active contact attempt phase with MPL back in '99, up to the point of a news release that there had been a signal detected that could well be from MPL. And all it ended up being was a reflection of the signal being sent out to MPL, not anything back from the crashed lander.

As Mike and Doug and others keep preaching, false alarms are quite possible, anything that appears to be a contact needs to be verified as two-way and containing at least valid headers in the downloaded data stream. In other words, while you may get a heads-up looking at the DSN status, the real proof of the pudding will be when downlinked data, if any, is analyzed and found to have valid headers. And valid engineering status data, hopefully...

And, guys? If the worst has happened and Oppy has finally gone on to meet her sister in whatever afterlife exists for such entities, it's not a sad time. Fourteen years of impressive and fundamentally game-changing data from a rover designed to last 90 days is not something to mourn. It's something to celebrate! Oppy doesn't deserve a dirge, she deserves a happy, rollicking Dixieland funeral parade!

-the other Doug

So maybe something more like this from Feb 2nd

https://twitter.com/dsn_status/status/959285817138008065
https://twitter.com/dsn_status/status/959286333024776192

If you see a "receiving data at 10 bps", then that might be a real signal. (They've transmitted from the LGA at higher rates but I don't think that the fault modes will ever try this.) My advice is to ignore all carrier lock messages.

There's a good chance that the first signals will only be seen in radio science recordings, which won't show up in the realtime DSN status anyway.

The DSN Now display shows 4 antennas at each complex. However, there may actually be more than 4. For example, Goldstone seems to have 8.
https://en.wikipedia.org/wiki/Goldstone_Dee...omplex#Antennas

Are the antennas that are not displayed idle, or are they doing stuff that we can't see, such as attempts to transmit commands to Opportunity? This might explain why we don't see the every-day attempts discussed in the most recent MER press release.

[EDIT] Uplink to MER1 from Goldstone now (12:30am). Maybe the action just happens while I'm asleep...

They are no longer used for routine DSN operations.

arggh you're right, was just watching the DSN status page and their twitter page, and another false alarm, this time with Maven.

edit: Here is the History of MAVEN from the DSN status twitter feed https://twitter.com/search?f=tweets&q=M...us&src=typd

And Opportunity's last DSN comm from June 10th? https://twitter.com/dsn_status/status/1005823559166459908

Well, that momentary carrier lock at 8.4351GHz was a lot closer to the expected Oppy frequency (8.4358GHz you pointed before), than Maven's 8.4454GHz... But yeah, maybe it's the doppler shift around the orbit.

-148dBm is FAR too strong for a MER LGA on the surface. That last DSN Now entry was a high gain antenna. Not the low gain that will be used now. Expect something more like -160 dBm.


Honestly - given the idiosyncrasies of how the DSN works - it is unlikely you're gonna be able to identify a successful vehicle recovery via DSN Now.

DSN has brought out the big guns tonight. The 70 metre DSS 14 "Mars" in action with MER1 now

Still up linking, although it did disappear for about 15 minutes then come back. EDIT: About 2 hours now, maybe trying to cover the whole window where Oppy might be awake with the larger antenna?

That would be lower even than the signal strength from the Voyagers at around 10 billion miles!
https://twitter.com/dsn_status/status/1043512420768120833
https://twitter.com/dsn_status/status/1043219216659361793
Admittedly, they would be using high-gain antennas and the bit rate is around 160 b/sec.
https://twitter.com/dsn_status/status/1043220222327627776

The Voyagers all transmit with large high gain antennas that are VERY directional and pointed at Earth. At X Band they have a beam width of half a degree and 48db of gain.

Opportunity will be using its low gain antenna that transmits to 180 degrees of the sky and has only 7 dB of gain

Physics is mean like that.

In defence of physics, I've never known it to be mean. It just doesn't care.