[Sea-sa] Initial draft of revised CCSDS 870x1y10 Yellow Book - with attachments

[Shames, Peter M (312B)]

Hi Richard,

Thanks for taking the time to review this (again).  And I am glad that you did not find any major issues.

On the two points you did raise I think we have a simple way to handle them.

Point 1: For the MAL header mapping I'll insert a note to the effect of what you stated.  However, for the MAL mapping where the existing spec is followed I believe that it is exactly the case that the specified MAL to SPP secondary header mapping yields at least a 57 byte header (and much more if long strings are used in the various variable length identifier fields.

Point 2: I agree that a "MAL on the ground; PUS in space" approach could be used.  I think that this is a specialization of Case 1, where MAL is on the ground and "standard TT&C communications" are used over the space link and on-board.  PUS is just the ECSS "standardized" way of doing TT&C.  We could insert a note to that effect if you all felt that was well advised.

Agreed?

Thanks, Peter


From: Richard Melvin <Richard.Melvin at scisys.co.uk>
Date: Wednesday, February 6, 2019 at 4:56 AM
To: Peter Shames <Peter.M.Shames at jpl.nasa.gov>, SEA-SA <sea-sa at mailman.ccsds.org>, "Wilmot, Jonathan J. (GSFC-5820)" <jonathan.j.wilmot at nasa.gov>, Dan Smith <danford.s.smith at nasa.gov>
Subject: RE: Initial draft of revised CCSDS 870x1y10 Yellow Book - with attachments

I spent some time reviewing this, and it looks good.


Two quick points:

As shown in Table 5-2 the MAL version of the SPP secondary header is a minimum of 37 octets plus another 4 variable length fields that are a minimum of 20 more octets but have a potential maximum length of thousands of bytes (each variable length field has a 32 bit length field).

I don’t think this is accurate, as the entire field, including the length, would not be present if the corresponding header flag is not set. This does complicate decoding a bit, but not excessively



–        In order to be efficient to use in a real-time, on-board, environment significant effort should be invested to develop efficient mappings across the space communication links as well as to develop instances of on-board deployments that minimize the impact on these resource constrained environments.


Conceptually, you could make the point that a possible solution to this is to map the MO services to the full PUS stack, instead of merely to CCSDS space packets. This would mean that the MO services would have access to:


-          The protocol optimisation work already done

-          The multiple existing onboard implementations.

-          Extensive operational usage experience

In practise, this is probably what would happen if the ground-segment side of ESA adopts MO and the spacecraft-specification side sticks with PUS.

However, that is a big enough political can of worms that I would definitely not suggest actually raising it in the context of this document.


Richard

From: Shames, Peter M (312B) <Peter.M.Shames at jpl.nasa.gov>
Sent: 01 February 2019 23:25
To: SEA-SA <sea-sa at mailman.ccsds.org>; Wilmot, Jonathan J. (GSFC-5820) <jonathan.j.wilmot at nasa.gov>; Dan Smith <danford.s.smith at nasa.gov>; Richard Melvin <Richard.Melvin at scisys.co.uk>
Subject: Re: Initial draft of revised CCSDS 870x1y10 Yellow Book - with attachments

Re-do, bloody Outlook outlaws … it thought I was done.

Peter


From: Peter Shames <Peter.M.Shames at jpl.nasa.gov<mailto:Peter.M.Shames at jpl.nasa.gov>>
Date: Friday, February 1, 2019 at 3:21 PM
To: SEA-SA <sea-sa at mailman.ccsds.org<mailto:sea-sa at mailman.ccsds.org>>, "Wilmot, Jonathan J. (GSFC-5820)" <jonathan.j.wilmot at nasa.gov<mailto:jonathan.j.wilmot at nasa.gov>>, Dan Smith <danford.s.smith at nasa.gov<mailto:danford.s.smith at nasa.gov>>, Richard Melvin <Richard.Melvin at scisys.co.uk<mailto:Richard.Melvin at scisys.co.uk>>
Subject: Initial draft of revised CCSDS 870x1y10 Yellow Book

Gentlemen,

Attached please find the initial draft of the revised CSDS 870x1y10 Yellow Book.  All of the text that was added or changed is shown in red, as are the title of any changed figures.

It includes the following kinds of updates:

1)      Inclusion of sections to respond to MOIMS review comments

2)      Inclusion of "the 3 cases" that were discussed at the last joint meeting

3)      The results of discussions held on-line with Richard Melvin and members of the SEA SAWG

4)      Revised diagrams that reflect these discussions.

A spreadsheet we used to track all of the inputs and dispositions is attached.  It is not as formal as a set of RIDs and from/to, but it gets the job done.

Please review this draft and signal your acceptance (or displeasure) with what has been proposed.

Once this successfully passes our "internal" SEA-SA (and supporters) review I will distribute it to the rest of the team.

Thanks, Peter



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