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Dust Storm
marsophile
post Sep 17 2018, 05:55 AM
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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.
QUOTE
With more sunlight reaching the rover's solar array, the Opportunity team at NASA's Jet Propulsion Laboratory in Pasadena, California, are increasing the frequency of commands it beams to the 14-plus-year-old rover via the dishes of NASA's Deep Space Network from three times a week to multiple times per day.

[EDIT] Uplink to MER1 from Goldstone now (12:30am). Maybe the action just happens while I'm asleep...
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djellison
post Sep 17 2018, 03:18 PM
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QUOTE (marsophile @ Sep 16 2018, 10:55 PM) *
Are the antennas that are not displayed idle


They are no longer used for routine DSN operations.
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xflare
post Sep 18 2018, 07:53 AM
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QUOTE (mcaplinger @ Sep 15 2018, 08:19 PM) *
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.


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

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
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akuo
post Sep 18 2018, 08:02 AM
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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.


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djellison
post Sep 18 2018, 03:20 PM
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-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.
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akuo
post Sep 19 2018, 07:12 AM
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DSN has brought out the big guns tonight. The 70 metre DSS 14 "Mars" in action with MER1 now smile.gif


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xflare
post Sep 19 2018, 08:37 AM
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QUOTE (akuo @ Sep 19 2018, 08:12 AM) *
DSN has brought out the big guns tonight. The 70 metre DSS 14 "Mars" in action with MER1 now smile.gif


Still up linking, although it did disappear for about 15 minutes then come back. unsure.gif EDIT: About 2 hours now, maybe trying to cover the whole window where Oppy might be awake with the larger antenna?
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marsophile
post Sep 23 2018, 06:01 AM
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QUOTE (djellison @ Sep 18 2018, 08:20 AM) *
Expect something more like -160 dBm.

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
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djellison
post Sep 23 2018, 03:54 PM
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QUOTE (marsophile @ Sep 22 2018, 10:01 PM) *
That would be lower even than the signal strength from the Voyagers at around 10 billion miles!


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.
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fredk
post Sep 23 2018, 06:47 PM
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In defence of physics, I've never known it to be mean. It just doesn't care. wink.gif
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marsophile
post Yesterday, 02:19 AM
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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?
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mcaplinger
post Yesterday, 02:53 AM
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QUOTE (marsophile @ Sep 23 2018, 06:19 PM) *
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?

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.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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climber
post Today, 06:42 PM
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Hi Oppy, we can at least see you again: https://www.jpl.nasa.gov/news/news.php?feature=7245


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Explorer1
post Today, 08:24 PM
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Glad to see the old girl... a poignant image if there ever was one!
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