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mars_armer
post Apr 4 2005, 02:38 PM
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I just heard that Odyssey went into safe mode on Saturday. I haven't seen any official announcement yet.

One result is that MER is having to replan using direct to earth only. Current estimate is that Odyssey will not be able to support UHF relay until "mid-week at the earliest".
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djellison
post Apr 4 2005, 02:55 PM
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Now that's bad news. I suppose they could bring MGS back into a relay role, but it would take about as long to write and uplink the commands for that as it will to fix odyssey - any URL's with news on this?

Doug
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MahFL
post Apr 4 2005, 03:25 PM
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I was wondering why there were no new images since the 2nd April.
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Guest_Sunspot_*
post Apr 4 2005, 04:03 PM
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Are they still able to command the rovers in the normal way, just not transmit large amounts of data? I suppose they've put off all driving and science activities until the problem is resolved? sad.gif
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dot.dk
post Apr 4 2005, 04:18 PM
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QUOTE (Sunspot @ Apr 4 2005, 04:03 PM)
Are they still able to command the rovers in the normal way, just not transmit large amounts of data? I suppose they've put off all driving and science activities until the problem is resolved?  sad.gif
*


Why should they do that? Just send commands and downlink via direct to Earth sessions. And Why has MGS not been used for relay as much as Odessey?


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djellison
post Apr 4 2005, 04:21 PM
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A typical rover day - roughtly - in local solar time....

10:00 - Wakeup
11:00 - Direct from Earth HGA uplink of days commands
11:30 - 5 min carrier only tone on LGA to confirm handover to new sequence (if driving at the same time, this is called a honk - and no, they've not observed a dopler from the rover driving smile.gif )
11:40 - Sometimes a nap for a half an hour, or an hour.
15:00 - Sometimes an Odyssey Pass
16:00 - Sometimes an Odyssey Pass - usually one, sometimes 2 - about 90 mins apart
17:00 - Sleep
if deep sleep -thenskip straight thru to the following morning, otherwise
03:00 - 04:00 - same UHF as before, one or two, about 90 mins apart.

The bulk of the rovers activities occur between around 11:00 and 15:00. Very VERY little data gets downlinked via DTE on the HGA usually - as it's power inefficient compared to UHF ( on a Whrs / Mbit scale )

I imagine, without UHF passes - they might use an extended HGA pass in the morning and add some DTE after the uplink - and perhaps another short one in the afternoon to downlink housekeeping data for the day, and a very small ammount of science data - probably little more than thumbnails, and reduced navcam frames.

Doug
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Guest_Sunspot_*
post Apr 4 2005, 04:48 PM
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I think they were planning 2 days of imaging at Viking Crater...did that get all the imaging data down?

The lack of any picture updates, even small thumbnails might imply they've decided to forgo any driving/science at the moment?
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tedstryk
post Apr 4 2005, 04:51 PM
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QUOTE (dot.dk @ Apr 4 2005, 04:18 PM)
QUOTE (Sunspot @ Apr 4 2005, 04:03 PM)
Are they still able to command the rovers in the normal way, just not transmit large amounts of data? I suppose they've put off all driving and science activities until the problem is resolved?  sad.gif
*


Why should they do that? Just send commands and downlink via direct to Earth sessions. And Why has MGS not been used for relay as much as Odessey?
*



Because the data volume that MGS can store and relay is a pittance compared to Odyssey.


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dot.dk
post Apr 4 2005, 05:01 PM
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Can't wait for relay via MRO then hehe wink.gif


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djellison
post Apr 4 2005, 06:22 PM
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QUOTE (dot.dk @ Apr 4 2005, 04:18 PM)
downlink via direct to Earth sessions.


One 12 minute UHF pass with Odyssey = 184 Mbits
Typically done 2 times per sol, call it 300 Mbits.

300 Mbits at 8kbps DTE (on DSN antennae already scheduled for other missions) = 10.4 hrs. The most they could use the DTE for in a sol is a couple of hours, it takes a lot of power, and means that a single sols data would take perhaps 4 sols to downlink - during which time, the flash memory will have filled up - two fold smile.gif

MGS uses the MOC buffer for UHF ops - and so it plays hell with scheduling of MGS ops - has to be planned quite well in advance. Odyssey was doing more than enough for relay ops - so MGS was turned back to mapping ops. They only uplink to MGS about 3 or 4 times a week - and the sequence to include fill-in UHF passes would take a week or so to write - so by the time they've written the sequences, uplinked them....Odyssey will be back on course smile.gif

Doug
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mars_armer
post Apr 4 2005, 06:44 PM
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QUOTE (djellison @ Apr 4 2005, 04:21 PM)
The bulk of the rovers activities occur between around 11:00 and 15:00. Very VERY little data gets downlinked via DTE on the HGA usually - as it's power inefficient compared to UHF ( on a Whrs / Mbit scale )

I imagine, without UHF passes - they might use an extended HGA pass in the morning and add some DTE after the uplink - and perhaps another short one in the afternoon to downlink housekeeping data for the day, and a very small ammount of science data - probably little more than thumbnails, and reduced navcam frames.

Doug


Yes, the plan for the next few sols is to convert the morning 20-minute DTE to a 90-minute DTE. This only gives them 12.7 Mbits of downlink, of which the first 7 is engineering data. It also requires them to plan in restricted mode (relying on the previous morning's knowledge).

Since the hope is to get Odyssey relays restarted by the end of Wednesday, it doesn't make sense (yet) to try to get an MGS relay going.

And no, I haven't found a URL to confirm this information.
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dvandorn
post Apr 4 2005, 07:10 PM
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QUOTE (djellison @ Apr 4 2005, 12:22 PM)
QUOTE (dot.dk @ Apr 4 2005, 04:18 PM)
downlink via direct to Earth sessions.


One 12 minute UHF pass with Odyssey = 184 Mbits
Typically done 2 times per sol, call it 300 Mbits.

300 Mbits at 8kbps DTE (on DSN antennae already scheduled for other missions) = 10.4 hrs. The most they could use the DTE for in a sol is a couple of hours, it takes a lot of power, and means that a single sols data would take perhaps 4 sols to downlink - during which time, the flash memory will have filled up - two fold smile.gif

MGS uses the MOC buffer for UHF ops - and so it plays hell with scheduling of MGS ops - has to be planned quite well in advance. Odyssey was doing more than enough for relay ops - so MGS was turned back to mapping ops. They only uplink to MGS about 3 or 4 times a week - and the sequence to include fill-in UHF passes would take a week or so to write - so by the time they've written the sequences, uplinked them....Odyssey will be back on course smile.gif

Doug
*



Makes you appreciate why Squyres, in one Q&A session, said that his number one priority for "what to do different" on future missions is to have a bigger pipe for getting data back to Earth.

Heck -- my cable modem provides me 5 Megabits per *second*. At that rate, I can download 300 Megabits in about one minute.

How much coax cable would it take to set up the MERs with RoadRunner service, anyway...?

biggrin.gif

-the other Doug


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cIclops
post Apr 4 2005, 07:26 PM
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QUOTE (dvandorn @ Apr 4 2005, 07:10 PM)
Heck -- my cable modem provides me 5 Megabits per *second*.  At that rate, I can download 300 Megabits in about one minute.

How much coax cable would it take to set up the MERs with RoadRunner service, anyway...?


About three times as much as it needs at conjunction smile.gif

Make sure you get the heavy duty cable, it gets quite hot near the middle or use a longer run and route via Venus.

tip: twisted pair would be cheaper and lighter than coax and still work at 5 mb/s but it will need more repeaters to boost the signal.


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dot.dk
post Apr 4 2005, 07:28 PM
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IF Odessey is crippled could they use Mars Express as a temporary solution?

I know it has relayed a few pictures, but can it relay as much as Odessey?


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- Steven Squyres
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djellison
post Apr 4 2005, 07:28 PM
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I'll hold one end - and you start walking, stop when I give it two tugs so I can tie the next reel on, then get going when I give it three tugs.

That - or wait for MRO- with it's 4mbps downlink smile.gif

I think MEX is about as able as Odyssey - and it would be a nice repayment of the Odyssey-Beagle 2 attempts - if Odyssey takes a few days longer that would be a very good idea - but with MARSIS antenna deployment due soon - would they be up for it?

Doug
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