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Dust Storm
marsophile
post Jun 22 2018, 03:40 PM
Post #106


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https://forum.nasaspaceflight.com/index.php...9668#msg1559668

Being designated as the uplink in an MSPA can be an artifact of the way the MSPA is set up. Uplink means that it gets the only two-way channel in the MSPA group. AFAIK, this doesn't preclude doing only downlink.
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mcaplinger
post Jun 22 2018, 04:11 PM
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QUOTE (marsophile @ Jun 22 2018, 07:40 AM) *
Being designated as the uplink in an MSPA can be an artifact of the way the MSPA is set up.

You'll have to explain what you meant by this. I don't know exactly how DSN Now works as far as MSPA is concerned. When DSN is looking for a signal from a drifting frequency reference (which may be the case here), I think they often record in wideband and don't even try to lock up in real time, and I suspect this doesn't show up on DSN Now as a downlink (Doug would know for sure.)

However, if DSN Now says the uplink is to a specific spacecraft, I'm pretty sure it really is to that spacecraft.


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xflare
post Jun 22 2018, 04:22 PM
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Hopeful tweet from yesterday

https://twitter.com/AnthonyJCook2/status/1009920728546754561

QUOTE
Image from yesterday by Anthony Wesley of Australia, shows that dust, which had almost completely obscured this Martian hemisphere a week ago, has thinned enough for the dark markings to re-appear. At right is simulation of appearance of unobscured features. ALPO-Japan.
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djellison
post Jun 22 2018, 04:31 PM
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QUOTE (mcaplinger @ Jun 22 2018, 07:41 AM) *
Really?


Really. To be specific, we are commanding 5 minute beeps when we believe every fault window opens.....the expected behavior is thus just 5 minute beeps to preclude a lengthy power hungry DTE.
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scalbers
post Jun 22 2018, 09:11 PM
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Interesting paper. I coded up the equations and tested it to reproduce tables 2 and 3, so now I can plug in additional values. A tau of 10.8 still seems to be a few percent for green light depending on solar elevation angle. For practical powering up purposes it is rather dark, though quite a brighter than the full moon. With tau=15 I get between 0.4% and 1.2%.

QUOTE (serpens @ Jun 18 2018, 12:19 AM) *
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.


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marsophile
post Jun 22 2018, 09:36 PM
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https://mars.nasa.gov/mer/mission/status.html#opportunity

QUOTE
The project is listening every day for the rover during both the time of low-power fault communication windows and listening over a broader range of times under mission clock fault. Additionally, for the near term, the project is also sending a command to elicit a beep if the rover happens to be awake. The Deep Space Network (DSN) Radio Science Receiver (RSR) team is using the RSR to listen in on any DSN pass pointed at Mars that corresponds to possible wake up times for the rover.
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RoverDriver
post Yesterday, 03:15 AM
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QUOTE (scalbers @ Jun 22 2018, 02:11 PM) *
...
though quite a brighter than the full moon.
...


You are right, I thought that day/moonlight difference was corresponding to a Tau of 14 or thereabouts but it was the closest thing I could find. I would not be surprised if Oppy experienced a Tau at that level anyway.

Paolo


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scalbers
post Yesterday, 03:26 PM
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As a bit of nuance, a Tau of 14 sounds about right to make the direct solar illumination match the full moon, so one could look for an (Earth) moonlike orb to be somewhat visible through the dust. Otherwise there is brighter overall illumination from diffuse scattered light. How about a full Phobos smile.gif ?

The faint sun appearance shows up in a sky that is not quite black on the right panel of the second picture shown in this link posted earlier. Turning up the monitor brightness helps to see this. This is a useful example for expanding the envelope with my sky simulation software.


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Deimos
post Yesterday, 08:13 PM
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As further nuance, exp(-tau) is only appropriate when the Sun is straight up. Later in the mid-afternoon, a (normal) tau of 10.8 might have an effective extinction of, say, exp(-14.5). That would seem very similar to the right-most frame in the panel from that link--if you look very closely, the Sun is still visible as a faint, bluish disk.
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serpens
post Yesterday, 11:51 PM
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Remember that the panel view in the link is a simulation. The other point is that the brightness of the sun in any "real" image will be a function of the exposure time.
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scalbers
post Today, 01:48 AM
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Comparing simulations, mine so far is rather simplified given the high Tau values, though I'm getting a notably redder sky color than the one posted by the team. I'm pretty much developing a sky hue from color ratios derived using the paper discussed in post #110. This is reminiscient of the YouTube video posted earlier from a dust storm on Earth, and consistent if we extrapolate some of the redder colors in Curiosity images to higher Tau.


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