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Mro On Approach, TCM-3 not required
Redstone
post Feb 3 2006, 11:06 PM
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MRO has shifted from the cruise phase to Approach phase. Apparently, the trajectory is so good that TCM-3 was cancelled. This is good news for the prospects for a long life for MRO supporting future missions. TCM-4 is on Feb 28, and MOI on March 10. Only 5 weeks away! smile.gif
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edstrick
post Feb 20 2006, 08:46 AM
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I think we're dealing with paleolithic technology standards, maybe from the 70's or 80's.
<grin>
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Airbag
post Feb 20 2006, 07:22 PM
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QUOTE (edstrick @ Feb 20 2006, 03:46 AM) *
I think we're dealing with paleolithic technology standards, maybe from the 70's or 80's.
<grin>


Perhaps, but the Small Deep Space Transponders are new technology and used by many current missions. There are only so many X-band channels and they are simply all used up. This is all from the DESCANSO MER telecoms report (very interesting reading I thought).

The spacecraft do have their own IDs, but best not to tempt fate with multiple bit errors etc. and perhaps accidentally accept and decode a command not intended for that spacecraft. And yes, that can happen - Opportunity accidentally went into safe mode during a solar opposition experiment in which a bunch of NOPs was changed into something else as multiple bit errors slipped by the error checking etc.

There are several techniques (other than the obvious one of using Mars itself as a "blocker") that can be used to make sure X-band signals intended for MRO (and that is the important one during aerobraking) only get to MRO. From memory, I can recall these (there were others too):

- Change Opportunity's antennas' polarization (so that it is opposite to that of MRO)
- Doppler adjustment for specific target
- Reduce transmit power level (MRO has more gain)

Airbag

PS BTW, receivers are typically *never* turned off (except during Opportunity's Deep Sleep).
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Bob Shaw
post Feb 20 2006, 10:18 PM
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Can I patent interplanetary MAC addresses - they could be stored digitally in a small solid-state pod, perhaps?

We could call, them, oh, iMACs and iPods...

Seriously, if a $10 network card can have a unique identifier burned in, why don't spacecraft?

Bob Shaw


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Remember: Time Flies like the wind - but Fruit Flies like bananas!
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helvick
post Feb 21 2006, 12:08 AM
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QUOTE (Bob Shaw @ Feb 20 2006, 10:18 PM) *
Seriously, if a $10 network card can have a unique identifier burned in, why don't spacecraft?

I had a long boring waffle about bit rate, harmonics, the history of MAC addresses, Ethernet's emergence in the late 1980's and collisions on ARCNET networks in the early 1990's here but re-reading it made my eyes glaze over so I thought it would be better to simply point to the CCSDS website and in particular the Space Packet Protocol Blue Book Specification as an example of just hom much thought has to go into doing this sort of thing properly.

If only it was as simple as tagging each packet with a 12 byte target identifier.
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Bob Shaw
post Feb 21 2006, 11:16 AM
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QUOTE (helvick @ Feb 21 2006, 12:08 AM) *
I had a long boring waffle about bit rate, harmonics, the history of MAC addresses, Ethernet's emergence in the late 1980's and collisions on ARCNET networks in the early 1990's here but re-reading it made my eyes glaze over so I thought it would be better to simply point to the CCSDS website and in particular the Space Packet Protocol Blue Book Specification as an example of just hom much thought has to go into doing this sort of thing properly.

If only it was as simple as tagging each packet with a 12 byte target identifier.


I followed the links, and yes, there's a lot of work been put into the definition of the systems and architecture pertaining to Space Packets and wholly laudable commitments to international and interplanetary interoperability. But nowhere do I see such a thing as an analogue of a MAC address, which has historically provided a more-or-less fail-safe identifier for almost any bit of hardware. I still can't see why not...

...am I missing something?

Bob Shaw


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mcaplinger
post Feb 21 2006, 02:39 PM
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QUOTE (Bob Shaw @ Feb 21 2006, 03:16 AM) *
...am I missing something?


See the Global Spacecraft ID document: http://public.ccsds.org/publications/archive/320x0b1s.pdf

Of course, these are only 8 or 10 bits long.

But has been already pointed out, just relying on an ID field to reject commands would be foolish in the presence of bit errors. If you were designing a mission-critical system based on Ethernet (which probably wouldn't be a good idea anyway because of single point failures in the shared transmission medium) you would hopefully not rely on MAC uniqueness to keep the wrong receiver from doing something. It might be unlikely for a burst of errors to corrupt one MAC address into another in such a way to get past CRC checking, but it's not "fail-safe". Even with your home LAN, there are acknowledgement protocols in TCP/IP to keep such problems from happening.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Posts in this topic
- Redstone   Mro On Approach   Feb 3 2006, 11:06 PM
- - RNeuhaus   Good news. I seems that MRO has started to gain it...   Feb 4 2006, 04:41 AM
|- - ugordan   QUOTE (RNeuhaus @ Feb 4 2006, 05:41 AM)I seem...   Feb 4 2006, 12:13 PM
|- - jmknapp   QUOTE (ugordan @ Feb 4 2006, 07:13 AM) As...   Feb 15 2006, 01:19 PM
|- - jmknapp   PS: Does anyone know what the field-of-view and re...   Feb 15 2006, 02:28 PM
- - abalone   QUOTE (Redstone @ Feb 4 2006, 10:06 AM)MRO ha...   Feb 4 2006, 12:49 PM
- - djellison   It's odd to think that from 'aboe' - M...   Feb 4 2006, 03:19 PM
|- - SFJCody   How many pixels would HiRise get across the disc o...   Feb 4 2006, 03:50 PM
|- - mcaplinger   QUOTE (SFJCody @ Feb 4 2006, 07:50 AM)How man...   Feb 4 2006, 05:26 PM
- - djellison   This is from a little PDF I found at the same plac...   Feb 4 2006, 05:41 PM
|- - crabbsaline   QUOTE (djellison @ Feb 4 2006, 12:41 PM)This ...   Feb 7 2006, 11:11 AM
- - djellison   I think they're using the ONC more as a tech-d...   Feb 7 2006, 11:57 AM
- - djellison   http://bookstore.spie.org/index.cfm?fuseac...d=619...   Feb 15 2006, 02:35 PM
|- - jmknapp   QUOTE (djellison @ Feb 15 2006, 09:35 AM)...   Feb 15 2006, 03:52 PM
|- - Bob Shaw   From the MRO website: http://mars.jpl.nasa.gov/mr...   Feb 15 2006, 07:29 PM
|- - jmknapp   I made an animation of the approach through the fi...   Feb 16 2006, 03:35 PM
- - djellison   Given the addition of some post-moi-pre-aerobrakin...   Feb 16 2006, 03:46 PM
|- - jmknapp   QUOTE (djellison @ Feb 16 2006, 10:46 AM)...   Feb 16 2006, 05:00 PM
|- - mcaplinger   QUOTE (jmknapp @ Feb 16 2006, 09:00 AM) L...   Feb 16 2006, 05:34 PM
|- - jmknapp   QUOTE (mcaplinger @ Feb 16 2006, 12:34 PM...   Feb 16 2006, 06:03 PM
|- - helvick   QUOTE (jmknapp @ Feb 16 2006, 06:03 PM) W...   Feb 16 2006, 06:30 PM
|- - mcaplinger   QUOTE (jmknapp @ Feb 16 2006, 10:03 AM) W...   Feb 16 2006, 10:14 PM
|- - jmknapp   QUOTE (mcaplinger @ Feb 16 2006, 05:14 PM...   Feb 16 2006, 10:42 PM
|- - mcaplinger   QUOTE (jmknapp @ Feb 16 2006, 02:42 PM) I...   Feb 16 2006, 11:31 PM
|- - jmknapp   QUOTE (mcaplinger @ Feb 16 2006, 06:31 PM...   Feb 17 2006, 02:00 AM
|- - mcaplinger   QUOTE (jmknapp @ Feb 16 2006, 06:00 PM) H...   Feb 17 2006, 04:05 AM
|- - Bob Shaw   QUOTE (mcaplinger @ Feb 17 2006, 04:05 AM...   Feb 17 2006, 12:18 PM
|- - AlexBlackwell   QUOTE (Bob Shaw @ Feb 17 2006, 12:18 PM) ...   Feb 17 2006, 06:13 PM
|- - jmknapp   QUOTE (AlexBlackwell @ Feb 17 2006, 01:13...   Feb 17 2006, 06:28 PM
||- - AlexBlackwell   QUOTE (jmknapp @ Feb 17 2006, 06:28 PM) B...   Feb 17 2006, 06:34 PM
||- - elakdawalla   QUOTE (AlexBlackwell @ Feb 17 2006, 10:34...   Feb 17 2006, 06:36 PM
||- - AlexBlackwell   QUOTE (elakdawalla @ Feb 17 2006, 06:36 P...   Feb 17 2006, 06:50 PM
|- - mcaplinger   QUOTE (AlexBlackwell @ Feb 17 2006, 10:13...   Feb 17 2006, 07:50 PM
|- - AlexBlackwell   QUOTE (mcaplinger @ Feb 17 2006, 07:50 PM...   Feb 17 2006, 08:06 PM
||- - djellison   QUOTE (AlexBlackwell @ Feb 17 2006, 08:06...   Feb 17 2006, 08:09 PM
||- - RNeuhaus   QUOTE (AlexBlackwell @ Feb 17 2006, 03:06...   Feb 17 2006, 10:55 PM
|- - jmknapp   QUOTE (mcaplinger @ Feb 17 2006, 02:50 PM...   Feb 17 2006, 09:39 PM
|- - ElkGroveDan   QUOTE (jmknapp @ Feb 17 2006, 09:39 PM) F...   Feb 17 2006, 11:06 PM
- - Sunspot   I kept reading that they wouldn't be doing any...   Feb 16 2006, 05:15 PM
- - Phil Stooke   It wouldn't be targeted, just whatever they ar...   Feb 16 2006, 06:49 PM
|- - babakm   Some imaging of Phoenix candidate site D is on the...   Feb 16 2006, 07:05 PM
- - RNeuhaus   Below is the Sout Pole Cap that looks different th...   Feb 16 2006, 07:10 PM
|- - brianc   A nice article about the MRO HIRISE camera syst...   Feb 16 2006, 08:00 PM
- - djellison   Thing is - only a tiny tiny change in the altitiud...   Feb 17 2006, 12:47 PM
- - Phil Stooke   Emily: "I guess no joke is too old and tired...   Feb 17 2006, 06:58 PM
|- - lyford   QUOTE (Phil Stooke @ Feb 17 2006, 10:58 A...   Feb 17 2006, 08:06 PM
|- - dvandorn   QUOTE (lyford @ Feb 17 2006, 02:06 PM) It...   Feb 18 2006, 12:57 AM
|- - Bob Shaw   QUOTE (dvandorn @ Feb 18 2006, 12:57 AM) ...   Feb 18 2006, 01:06 AM
- - djellison   Being VERY unscientific, approx speed at periareio...   Feb 17 2006, 09:59 PM
|- - Bob Shaw   The way I see it, almost *any* orbit is better tha...   Feb 17 2006, 10:46 PM
|- - AlexBlackwell   QUOTE (Bob Shaw @ Feb 17 2006, 10:46 PM) ...   Feb 17 2006, 10:52 PM
- - AlexBlackwell   Feb. 17, 2006 Dwayne Brown/Erica Hupp Headquarter...   Feb 17 2006, 10:25 PM
- - dvandorn   I think it's probably safest to blame it all o...   Feb 18 2006, 01:19 AM
- - yaohua2000   Mars Reconnaissance Orbiter was only 5 million kil...   Feb 19 2006, 01:12 AM
- - RNeuhaus   After reading more details about MRO. I found it m...   Feb 19 2006, 06:14 AM
|- - djellison   [quote name='RNeuhaus' post='42269' date='Feb 19 2...   Feb 19 2006, 09:32 AM
|- - helvick   QUOTE (djellison @ Feb 19 2006, 09:32 AM)...   Feb 19 2006, 10:57 AM
- - The Messenger   Nice collection of details. Hydrazine (HN#NH) has ...   Feb 19 2006, 06:35 AM
|- - dilo   Thanks for resuming all these infos, Rodolfo (perh...   Feb 19 2006, 07:50 AM
- - deglr6328   QUOTE (RNeuhaus @ Feb 19 2006, 06:14 AM) ...   Feb 19 2006, 10:46 AM
- - Airbag   Another interesting tidbit - MRO uses the same X-b...   Feb 19 2006, 07:26 PM
|- - Bob Shaw   QUOTE (Airbag @ Feb 19 2006, 07:26 PM) An...   Feb 19 2006, 09:41 PM
|- - belleraphon1   QUOTE (Airbag @ Feb 19 2006, 02:26 PM) An...   Feb 20 2006, 12:51 AM
- - Myran   QUOTE Bob Shaw said Am I alone in thinking that th...   Feb 19 2006, 11:03 PM
- - djellison   I imagine that a spacecraft that notices a signal ...   Feb 19 2006, 11:07 PM
|- - Steve   QUOTE (djellison @ Feb 19 2006, 06:07 PM)...   Feb 19 2006, 11:27 PM
|- - Bob Shaw   QUOTE (Steve @ Feb 19 2006, 11:27 PM) Ass...   Feb 19 2006, 11:40 PM
- - djellison   I was thinking that, I imagine they can sequence t...   Feb 19 2006, 11:42 PM
- - edstrick   On it's second lunar day, JPL tried to get Sur...   Feb 20 2006, 06:08 AM
|- - ugordan   Don't the DSN uplink commands have a sort of d...   Feb 20 2006, 08:27 AM
- - edstrick   I think we're dealing with paleolithic technol...   Feb 20 2006, 08:46 AM
|- - Airbag   QUOTE (edstrick @ Feb 20 2006, 03:46 AM) ...   Feb 20 2006, 07:22 PM
|- - Bob Shaw   Can I patent interplanetary MAC addresses - they c...   Feb 20 2006, 10:18 PM
|- - helvick   QUOTE (Bob Shaw @ Feb 20 2006, 10:18 PM) ...   Feb 21 2006, 12:08 AM
|- - Bob Shaw   QUOTE (helvick @ Feb 21 2006, 12:08 AM) I...   Feb 21 2006, 11:16 AM
|- - helvick   QUOTE (Bob Shaw @ Feb 21 2006, 11:16 AM) ...   Feb 21 2006, 02:19 PM
|- - mcaplinger   QUOTE (Bob Shaw @ Feb 21 2006, 03:16 AM) ...   Feb 21 2006, 02:39 PM
- - Myran   QUOTE Airbag said: Change Opportunity's antenn...   Feb 20 2006, 10:40 PM
- - djellison   As I understand it - spacecraft are all moving ver...   Feb 21 2006, 03:27 PM
- - Toma B   Is there any planed imaging with HiRISE on approac...   Feb 24 2006, 07:47 AM
|- - ugordan   There's always a good reason for not performin...   Feb 24 2006, 08:06 AM
|- - djellison   --><div class='quotetop'>QUOTE(T...   Feb 24 2006, 08:27 AM
- - Sunspot   The same was done with Cassini during the week or ...   Feb 24 2006, 09:38 AM
- - AlexBlackwell   The MRO arrival press kit is now up: Mars Reconna...   Feb 24 2006, 04:35 PM
|- - mcaplinger   QUOTE (AlexBlackwell @ Feb 24 2006, 08:35...   Feb 26 2006, 06:06 PM
- - djellison   And the press conf is in an hour and a bit as well...   Feb 24 2006, 04:53 PM
|- - jmknapp   QUOTE (djellison @ Feb 24 2006, 11:53 AM)...   Feb 25 2006, 03:29 PM
- - RNeuhaus   The MRO spacecraft will remain out of contact for ...   Feb 26 2006, 06:27 PM
|- - The Messenger   QUOTE (RNeuhaus @ Feb 26 2006, 11:27 AM) ...   Feb 27 2006, 04:17 PM
|- - Bob Shaw   QUOTE (RNeuhaus @ Feb 26 2006, 06:27 PM) ...   Feb 27 2006, 04:21 PM
- - edstrick   With apollo, for both orbit insertion and trans-ea...   Feb 27 2006, 07:10 AM
|- - jmknapp   Does anyone know which DSN stations and/or other f...   Feb 27 2006, 03:32 PM
|- - RNeuhaus   QUOTE (jmknapp @ Feb 27 2006, 10:32 AM) D...   Feb 27 2006, 07:07 PM
|- - mcaplinger   QUOTE (RNeuhaus @ Feb 27 2006, 11:07 AM) ...   Feb 27 2006, 07:46 PM
- - djellison   Of course - the reason for having such a low targe...   Feb 27 2006, 04:28 PM
|- - jmknapp   QUOTE (djellison @ Feb 27 2006, 11:28 AM)...   Feb 27 2006, 04:50 PM
|- - mcaplinger   QUOTE (djellison @ Feb 27 2006, 08:28 AM)...   Feb 27 2006, 04:54 PM
- - djellison   Stanford was listening to MER because MER was also...   Feb 27 2006, 04:53 PM
- - djellison   Ahh - someone mis-quoted the press pdf previously ...   Feb 27 2006, 05:01 PM
- - Bob Shaw   QUOTE (djellison @ Feb 27 2006, 05:01 PM)...   Feb 27 2006, 05:11 PM
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