[Sea-sa] FW: [CESG] Proposed modification to CCSDS time-code format

Tue Sep 20 16:29:06 UTC 2016

Annex D has a table of leap second corrections needed for conversion between TAI and UTC, and the table only goes up through 2009.  That table needs to be updated to at least the present, and also for as many specific future leap second adjustments as have been announced (by whatever group does that).

Other than that, I don’t see any technical issues that need fixing.

Craig

From: Shames, Peter M (312B) [mailto:peter.m.shames at jpl.nasa.gov]
Sent: Friday, September 16, 2016 7:19 PM
To: Biggerstaff, Craig (JSC-CD221)[LOCKHEED MARTIN CORP] <craig.biggerstaff at nasa.gov>
Cc: sea-sa at mailman.ccsds.org; Estefan, Jeff A (JPL-3940)[Jet Propulsion Laboratory] <jeffrey.a.estefan at jpl.nasa.gov>
Subject: Re: [Sea-sa] FW: [CESG] Proposed modification to CCSDS time-code format

Hi Craig,

Since you dug into this, did you have a chance to also give the current CCSDS 301x0b4 a thorough once over?  Is there anything else that needs fixing aside from that editorial comment and the added example?

Thanks, Peter

From: SEA-SA <sea-sa-bounces at mailman.ccsds.org<mailto:sea-sa-bounces at mailman.ccsds.org>> on behalf of "Biggerstaff, Craig (JSC-CD221)[LOCKHEED MARTIN CORP]" <craig.biggerstaff at nasa.gov<mailto:craig.biggerstaff at nasa.gov>>
Date: Friday, September 16, 2016 at 2:56 PM
To: Jeffrey Estefan <jeffrey.a.estefan at jpl.nasa.gov<mailto:jeffrey.a.estefan at jpl.nasa.gov>>, SEA-SA <sea-sa at mailman.ccsds.org<mailto:sea-sa at mailman.ccsds.org>>
Subject: Re: [Sea-sa] FW: [CESG] Proposed modification to CCSDS time-code format

Dear SAWG members,

I have obtained and reviewed ISO 8601:2004.  To answer your earlier questions:

·         ISO 8601 only addresses textual representations of time.  Binary encoding methods are not mentioned at all.

·         I don’t know if there is any relevant ISO standard comparable to the CCSDS binary formats, and haven’t tried to find out.

·         The two ASCII formats given in CCSDS 301.0-B-4, “Time Code Formats” are ISO 8601-compliant, although ISO expresses a preference for using the comma over the period to separate fractional units.  The relevant sections are:
3.5.1.1 ASCII TIME CODE A, Month/Day of Month Calendar Variation

3.5.1.2    ASCII TIME CODE B, Year/Day of Year Calendar Variation

·         301.0-B-4 correctly notes this fact way down in section B3.4:  “…The two ASCII time code variations (A, day of month, and B, day of year) include the most widely used human-readable presentations. Both variations are subsets of ISO 8601 (reference [2]).”

·         301.0-B-4 lists ISO 8601:2004 as an informative reference; there are no normative references in the document.

Best regards,

Craig

Craig Biggerstaff | Leidos
Senior Systems Engineering Staff | Civil
phone:   281.483.2027
craig.biggerstaff at nasa.gov<mailto:craig.biggerstaff at nasa.gov> | leidos.com/civil<http://www.leidos.com/civil>

[id:image001.png at 01D1F9ED.EA7FBB60]

From: SEA-SA [mailto:sea-sa-bounces at mailman.ccsds.org] On Behalf Of Estefan, Jeff A (3940)
Sent: Friday, September 09, 2016 3:03 PM
To: sea-sa at mailman.ccsds.org<mailto:sea-sa at mailman.ccsds.org>
Subject: Re: [Sea-sa] FW: [CESG] Proposed modification to CCSDS time-code format

Peter,

Only a preview of the ISO 8601:2004<https://www.iso.org/obp/ui/#iso:std:iso:8601:ed-3:v1:en> is freely available. As typical with the ISO and ISO/IEC standards many have a cost associated with obtaining copies. I suppose this is one advantage to an open standards specs such as those from CCSDS. Nevertheless, harmonization should be performed. It should be noted that ISO 8601 is also not new not even as new as the latest rev published in 2004. It goes back to 1988 so close to around the CCSDS spec came about. In any event, sending this to your distribution list so that hopefully somebody from your team will do the reconciliation.

Cheers!

 - Jeff

From: Peter Shames <Peter.M.Shames at jpl.nasa.gov<mailto:Peter.M.Shames at jpl.nasa.gov>>
Date: Friday, September 9, 2016 at 8:42 AM
To: Jeff Estefan <Jeffrey.A.Estefan at jpl.nasa.gov<mailto:Jeffrey.A.Estefan at jpl.nasa.gov>>, "sea-sa at mailman.ccsds.org<mailto:sea-sa at mailman.ccsds.org>" <sea-sa at mailman.ccsds.org<mailto:sea-sa at mailman.ccsds.org>>
Subject: Re: [Sea-sa] FW: [CESG] Proposed modification to CCSDS time-code format

Hi Jeff,

The CCSDS time code standard is intended for use everywhere, on the ground and in space.  It permits very high resolution time expression, where that is required, but also permits truncation of the time and calendar fields where the data field size is a concern.

To be frank, I have not looked at the ISO spec.  If you have it and wish to do a comparison, I would welcome that contribution.  I will point out that the CCSDS spec has been around since 1987.  This is not something new.

Thanks, Peter

From: SEA-SA <sea-sa-bounces at mailman.ccsds.org<mailto:sea-sa-bounces at mailman.ccsds.org>> on behalf of Jeffrey Estefan <jeffrey.a.estefan at jpl.nasa.gov<mailto:jeffrey.a.estefan at jpl.nasa.gov>>
Date: Friday, September 9, 2016 at 7:53 AM
To: SEA-SA <sea-sa at mailman.ccsds.org<mailto:sea-sa at mailman.ccsds.org>>
Subject: Re: [Sea-sa] FW: [CESG] Proposed modification to CCSDS time-code format

Peter. Just happened to be on your distribution list but had a couple of questions for you. First, do you know if the intended scope of this Blue book standard is for space ground systems or flight systems or both? We tend to have problems especially with fractional seconds where not only are there inconsistencies in how fractional seconds are treated across the functional areas of our ground systems and applications but even more apparent on the flight side, particularly how flight software handles this and little consistency among missions. Second, and a more fundamental question. What advantage does the CCSDS Time Code Formats Blue book standard offer over the ubiquitous and heavily reference ISO 8601:2004 standard? I see the latter is referenced in the Blue book but what are the differentiators? Do we need yet another industry standard for time code formats? Just curious. Thanks in advance! - Jeff

From: SEA-SA <sea-sa-bounces at mailman.ccsds.org<mailto:sea-sa-bounces at mailman.ccsds.org>> on behalf of Peter Shames <Peter.M.Shames at jpl.nasa.gov<mailto:Peter.M.Shames at jpl.nasa.gov>>
Date: Thursday, September 8, 2016 at 10:33 AM
To: SEA-SA <sea-sa at mailman.ccsds.org<mailto:sea-sa at mailman.ccsds.org>>
Subject: [Sea-sa] FW: [CESG] Proposed modification to CCSDS time-code format

Dear SAWG Colleagues,

In CCSDS it is typical that cross cutting topics get handled by the SEA Area.  Time codes are one such topic and the key CCSDS document defining these now needs to be reviewed.  The CESG has asked SEA to do this and the obvious WG to do this right now is the SAWG.

The current document, and a proposed page edit with some modifications that make explanatory updates, is attached.   The document itself, in its current published form is also attached.  Note that the most recent publication date is Nov 2010.   This is a relatively short document, at 43 pages in length, and the normative materials are only 8 of those pages.   Aside from it being time to re-confirm this document, what prompted this review was a confusion as to what was a valid truncation of the time code field, as described on pgs 3-6 and 3-7.   This has been discussed and resolved in the CESG.  The result was to agree that the document spec was correct as stated, and to acknowledge that it does allow a variety of truncations, but to clarify what is acceptable by adding the non-normative examples on the “ProposedMods” pages.

What I would like is to request some help from one of you.  Would one of you be willing to take on the task of reviewing this document, and the proposed modifications, and determine if there is anything else in this document that should be updated?  The only other item we know of is a reference in sec 3.5.1.d, pg 3-8, to “the need to accommodate the upcoming century rollover in only 11 years”.   Clearly that is now in the past and should be removed.

If there are only these sort of editorial changes these can easily be accommodated in a Corrigendum or as an editorial matter, but we need someone to review the document and make that determination.

Can I get a volunteer to do this so that we may discuss it, hopefully quickly, during the upcoming working meeting?

Thanks, Peter

From: CESG <cesg-bounces at mailman.ccsds.org<mailto:cesg-bounces at mailman.ccsds.org>> on behalf of Erik Barkley <erik.j.barkley at jpl.nasa.gov<mailto:erik.j.barkley at jpl.nasa.gov>>
Date: Tuesday, September 6, 2016 at 4:07 PM
To: CCSDS Engineering Steering Group - CESG Exec <cesg at mailman.ccsds.org<mailto:cesg at mailman.ccsds.org>>
Subject: [CESG] Proposed modification to CCSDS time-code format

CESG Colleagues,

Based on the interactions/e-mails from Gippo, Mario, and Peter, attached please find a proposal for update of the timecode blue book. By way of summary, I found that the language, upon close reading, was essentially okay and that it really already allows for fractional seconds to be optional in either timecode A or timecode B and in fact abbreviations/omissions in other respects as well.  I took advantage of the examples offered by Mario as I believe these help to make to illustrate more clearly how the rules of abbreviation can be applied.   I look forward to discussing this at the CESG telecon/webex tomorrow.

Best regards,

-Erik
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