[CESG] [EXTERNAL] Re: Comments (and only comments) on space link directionality discussion yesterday

[Shames, Peter M (US 312B)]

Dear Margherita,

Actually, this whole problem started in 2003 when the support for AOS forward links in the TM Sync & Channel coding books were erroneously removed during the slew of edits that were made at that time.  I have actually done the forensic analysis in the earlier documents and located exactly when that change was made. I cannot confirm why the change was made, but it had the effect of moving us backwards and this was truly unfortunate.

The WG has been asked to rectify this error and chose to throw up road-blocks instead of making the simple fix.  This is also unfortunate. This has nothing to do with being "input driven".

These changes took place during the "SLS restructuring" which was accomplished during 2001-2003.  This massive editing operation, which resulted in a real improvement in this set of specs, was aimed at the existing space data link protocol specs and the coding specs.  My interest in doing this research was to establish facts, not to assign blame.  My assertion is that all of these changes were puiblished in the 2002-2003 era and that the Coding WG went backwards between 2002 and 2003 and abandoned support for AOS in the forward direction in the process.

According to the CCSDS Silver Book documents archived on the web site this is clearly the case.  Key items are highlighted for emphasis.  Follow the bouncing ball.

Coding & Synch

  *   Prior to 2003 we had a CCSDS 101.0-B-6-S<https://public.ccsds.org/Pubs/101x0b6s.pdf> , Telemetry Channel Coding. Silver Book. Issue 6. October 2002. It said, in sec 1.3 Applicability "In addition to being applicable to conventional Packet Telemetry systems [1], the codes in this recommendation are applicable to the forward and return links of Advanced Orbiting Systems (AOS) [2]. "
  *   This 2002 channel coding spec referenced both the current "TM" spec 102.0-B-5, and the then current AOS spec, 701.0-B-3.  That spec, in sec 1.2b, said "Advanced Orbiting Systems include manned and man-tended space stations, unmanned space platforms, free-flying spacecraft and new space transportation systems, many of which need services to concurrently transmit multiple digital data types (including audio and video) through space/ground and ground/space data channels. "
  *   In Sept 2003 we got CCSDS 131.0-B-1-S<https://public.ccsds.org/Pubs/131x0b1s.pdf>, TM Synchronization and Channel Coding. Silver Book. Issue 1. September 2003.  It said, in sec 1.1 "The purpose of this Recommended Standard is to specify synchronization and channel coding schemes used with the TM Space Data Link Protocol (reference [1]) or the AOS Space Data Link Protocol (reference [2]). These schemes are to be used over space-to-ground or space- to-space communications links by space missions. "  Note that ground to space has been dropped.
  *   So somehow, between the original "CCSDS 101x0 coding book" and the revised "CCSDS 131x0 coding book" the use these codes that was allowed on AOS forward links got removed.  This was right at the same time as the rest of the SLS document restructuring was done.
  *   Similar changes were made to TC synch & channel coding in 2003.  And to Space Packet.  It was all part of the same set of sweeping changes, Takahiro was the lead tech editor and Gippo was the WG chair.  I think the Panel was led by Kaufeler at that time.

Space Data Link

  *   Prior to 2003 we had CCSDS 103.0-B-2-S<https://public.ccsds.org/Pubs/103x0b2s.pdf> , Packet Telemetry Service Specification. Silver Book. Issue 2. June 2001.  It said, in Sec 1.1 "The layered model and services are based on the CCSDS Recommendations for Packet Telemetry and Telemetry Channel Coding, references [1] and [2]. These referenced Recommendations define the formats of the protocol-data-units used to transfer telemetry from spacecraft to ground or spacecraft to spacecraft, as well as the protocol procedures that support that transfer. "  And in Sec 1.2 it said "This Recommendation defines only the services provided between protocol layers of the CCSDS space to ground link."
  *   Contemporaneous with this TM Service spec was the TM spec itself, CCSDS 102.0.  It was also explicit in stating, in Sec 1.2 "The end-to-end transport of space mission data sets from source application processes

located in space to distributed user application processes located on the ground. "

  *   In Sept 2003 we got CCSDS 132.0-B-1-S<https://public.ccsds.org/Pubs/132x0b1c1e1s.pdf>, TM Space Data Link Protocol. Silver Book. Issue 1. September 2003.  It said, in sec 1.1 "This protocol is a Data Link Layer protocol (see reference [1]) to be used over space-to-ground or space-to-space communications links by space missions. "
  *   The 2003 revised AOS spec, as already noted, explicitly supported space/ground and ground/space. There is apparently not an extant copy of the original AOS spec.  All that is available in the CCSDS Silver docs is CCSDS 701.00-R-3 (Red Book)<https://public.ccsds.org/Pubs/701RB3.pdf> , Advanced Orbiting Systems, Networks and Data Links: Architectural Specification. Silver Book. Issue 3. June 1989.  That AOS spec, or really set of specs, which supported space/ground and ground/space, were quite thorough and comprehensive.  I do not think that all of these features were ever implemented, but someone familiar with the ISS comm architecture would have to confirm that.
  *   I do know that AOS has been used for years in both the forward and return directions, since I know that we created the EF-CLTU Orange Book, CCSDS 912.11-O-1, in 2012, explicitly to provide JSC with a variant of the SLE F-CLTU that would support AOS forward, synchronous, encoded links.  Prior to that they had been using F-CLTU for AOS with some awkward work-arounds to keep the forward link synchronous.  This was all to be replaced by FF-CLTU, which is still hung up, in part, because there is no longer a "formal" CCSDS forward coding standard for AOS.
  *   In 2003 we got CCSDS 732.0-B-1-S<https://public.ccsds.org/Pubs/732x0b1s.pdf> , AOS Space Data Link Protocol. Silver Book. Issue 1. September 2003. As a part of that same restructuring package.  In sec 1.1 it says "This protocol is a Data Link Layer protocol (see reference [1]) to be used over space-to-ground, ground-to-space, or space-to-space communications links by space missions. "  So the AOS spec covers all of the directions, but the coding specs no longer support that with any formal text.  Hence the dilemma, in place since 2003.
  *   The 2003 AOS spec did directly reference CCSDS 131.0-B-1 , but as we have already seen that spec had already been neutered and no longer supported use of the TM codes for forward links.  This was an issue that could have been easily remedied, as was requested on a number of occasions, but making that change has consistently been thwarted by the C&S WG.


To this date there is no longer a published CCSDS coding and synch spec that actually supports the AOS capabilities that have been on the books since that spec was first published.

Kind regards, Peter



From: CESG <cesg-bounces at mailman.ccsds.org> on behalf of "Margherita.di.Giulio at esa.int" <Margherita.di.Giulio at esa.int>
Date: Sunday, June 7, 2020 at 3:30 AM
To: Erik Barkley <erik.j.barkley at jpl.nasa.gov>
Cc: CCSDS Engineering Steering Group - CESG Exec <cesg at mailman.ccsds.org>
Subject: [EXTERNAL] Re: [CESG] Comments (and only comments) on space link directionality discussion yesterday

Dear Erik,
        indeed all started in 2017 and at Fall 2017 C&S WG had a principle agreement for re-introducing the codes already used for AOS uplink, together with a down selection of more recent codes. It is therefore very unfortunate that this issue has not been finalised.
As you know, WGs are input driven . Since Fall 2017 such inputs have been either missing or modifying the (previous) position(s). Consequently, the progress has been slow.
The history was reported at the CESG telecon on 10 March 2020, as per second slide of the attached ppt (also available in CWE).

With respect to the Forward Frame Blue Book, this book specifies the service provision, leaving to other books the service production. The way forward is to mention, w.r.t. the supported uplink options,  the relevant CCSDS books in progress , with eventual Editorial Corrigenda at due time.
This has been the approach taken by many other CCSDS recommendations, and it has been no problem.
Notice that in FF CSTS those books are, correctly, referred to only as informative reference.

It is my understanding that currently C&S WG is working at the update of 131.0-B, 131.2-B and 131.3-B, and hopefully they can quickly converge on this.
Kind regards,
Margherita



--------------------------------------------------------------
Margherita di Giulio
Ground Station Systems Division
Backend Software Section (OPS-GSB)


European Space Agency ESA/ESOC
Robert-Bosch-Str. 5
D-64293 Darmstadt - Germany
Tel: +49-6151-902779
e-mail: Margherita.di.Giulio at esa.int





From:        "Barkley, Erik J (US 3970)" <erik.j.barkley at jpl.nasa.gov>
To:        "Margherita.di.Giulio at esa.int" <Margherita.di.Giulio at esa.int>, "Tai, Wallace S (US 9000)" <wallace.s.tai at jpl.nasa.gov>
Cc:        "CESG -- CCSDS-Engineering Steering Group (cesg at mailman.ccsds.org) (cesg at mailman.ccsds.org)" <cesg at mailman.ccsds.org>
Date:        04/06/2020 18:40
Subject:        Comments (and only comments) on space link directionality discussion yesterday
________________________________


Dear CESG Chairs,



Now that I have had a little time to digest yesterday’s proceedings, I offer some comments and observations with regard to the CESG discussion yesterday on the directionality of space links and related conversation.



1.        The apparent lack of progress/resolution of the issue leaves the CSS Area with a dilemma of how to proceed with publication polling for the FF-CSTS (Forward Frame) recommendation.  From all reports that I have from the CSTS working group, the book will be ready for publication very soon as prototyping has been satisfactorily completed. To the best of my recollection it was three years ago, the spring meetings of 2017, where a request was made to see if some sort of reference could be provided such that we could include it in the forward frame book. At this point I suspect the forward frame book will be ready for publication long before the issue is resolved -- in the CSS area we may have to figure out some sort of wording to work around the fact that there is no CCSDS standard that can be referenced -- this could be something to indicate that as per common usage in the real world FF-CSTS can use this for forwarding of AOS frames etc.
2.        I believe the comments yesterday about AOS already being used in real world operations in the forward direction are correct. As such I find it concerning that CCSDS as a whole cannot muster the ability to document this as a proper use of the AOS standard. It is also troubling as, if it is correctly reported, this was already indicated in prior versions of documentation and changed circa 2004.
3.        We have seen this past week very real evidence of the ascendancy of commercial ventures with the launch of a privately developed rocket contracted to NASA for carrying astronauts to the ISS (which I believe uses AOS in the forward direction). I'm concerned that in this case, CCSDS seems to be unable to keep up with current developments on the world stage and that this may present a risk to long term CCSDS relevancy.



The above is offered only as commentary and is not meant to impugn the integrity or good work of anybody that labors for the cause of CCSDS standardization. Rather I'm concerned that this issue, if not resolved sooner rather than later, will impact CCSDS as a whole and may serve to make CCSDS less viable in general, thereby exacerbating what I see as already an issue of succession planning toward the next generation of engineers who may have an interest in international standardization.



These are only my comments – I do not speak for any other parties.  The comments are meant only for consideration by the CESG Chairs, with CESG copied for cognizance.



Best regards,

-Erik

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