[MOIMS-NAV-EXEC] ARE: Notional Events requirements from NAV WG

[Lamy Alain]

Just one comment :

Having  more than one (absolute or relative) time is associated with an event may cause confusion :
The time associated with an event enables defining an “order”.
But if there are 2 different time references, you may have :
T1(event a) < T1(event b)
T2(event a) > T2(event b)

This would be not consistent.
(to avoid this, T1 and T2 would have to be guaranteed equivalent, which is difficult to achieved).

But I suppose there are other ways :
It should (and this could be a new requirement) to add information (that is to say data) to an event.
This could for instance allow adding timing information or anything else that may be useful to the user of the event
(in some particular context).


PS: I’ll answer the 1st message from Dan later

Alain


De : MOIMS-NAV-EXEC [mailto:moims-nav-exec-bounces at mailman.ccsds.org] De la part de Gramling, Cheryl J. (GSFC-5950)
Envoyé : jeudi 20 octobre 2016 14:05
À : Oltrogge, Daniel; moims-nav-exec at mailman.ccsds.org
Objet : Re: [MOIMS-NAV-EXEC] Notional Events requirements from NAV WG

Ah, well, now you raise a good point.
I wasn’t thinking of 2 different absolute time scales or even 2 different absolute time epochs, associated w 2 (or more) relative times; merely 2 different relative time scales referenced to the same absolute scale/epoch.  In my case [1 at ABS:2 at REL], you could identify RELTIME_1,….RELTIME_n.

If we try to address your point, it seems you’d need a way to define cross-strapping of the systems.  ABSTIME_1,…ABSTIME_n  to each of RELTIME_1,…RELTIME_n :
                RELTIME_1_1
                RELTIME_1_2
                :
                RELTIME_1_n
                RELTIME_2_1
                RELTIME_2_2
                :
                RELTIME_2_n
                :
where the second number refers to the ABSTIME.

How often would more than one ABSTIME [SYS or SCAL]  be used?  I can’t think of any examples.  However, I do think at least 2 different RELTIME [SYS] would be used somewhat frequently.

Cheryl


From: "Oltrogge, Daniel" <doltrogge at agi.com<mailto:doltrogge at agi.com>>
Date: Thursday, October 20, 2016 at 1:46 PM
To: "Gramling, Cheryl J. (GSFC-5950)" <cheryl.j.gramling at nasa.gov<mailto:cheryl.j.gramling at nasa.gov>>, "moims-nav-exec at mailman.ccsds.org<mailto:moims-nav-exec at mailman.ccsds.org>" <moims-nav-exec at mailman.ccsds.org<mailto:moims-nav-exec at mailman.ccsds.org>>
Subject: RE: [MOIMS-NAV-EXEC] Notional Events requirements from NAV WG

You raise a very good point.  And that’s fundamentally different that what I’d assembled below.

Any suggestions on how we could potentially reference the different relative times to their respective absolute times in a non-confusing, rigorous way ?

Thanks,

Dan

Daniel L. Oltrogge
SDC Program Manager & Senior Research Astrodynamicist
Center for Space Standards and Innovation
Analytical Graphics Incorporated
Voice: 719-482-4552; E-mail: oltrogge at agi.com<mailto:oltrogge at agi.com>

From: Gramling, Cheryl J. (GSFC-5950) [mailto:cheryl.j.gramling at nasa.gov]
Sent: Thursday, October 20, 2016 5:07 AM
To: Oltrogge, Daniel <doltrogge at agi.com<mailto:doltrogge at agi.com>>; moims-nav-exec at mailman.ccsds.org<mailto:moims-nav-exec at mailman.ccsds.org>
Subject: Re: [MOIMS-NAV-EXEC] Notional Events requirements from NAV WG

Dan,

I think we need a requirement that more than one relative time may optionally be associated with an event [e.g. the case of UTC relative time and Spacecraft Clock relative time].

Should it explicitly be stated that both an absolute and a relative time may optionally be associated with an event, or does the “or” in Req 3.a adequately cover that?

Thanks for putting this together.
Cheryl

From: MOIMS-NAV-EXEC <moims-nav-exec-bounces at mailman.ccsds.org<mailto:moims-nav-exec-bounces at mailman.ccsds.org>> on behalf of "Oltrogge, Daniel" <doltrogge at agi.com<mailto:doltrogge at agi.com>>
Date: Wednesday, October 19, 2016 at 4:57 PM
To: "moims-nav-exec at mailman.ccsds.org<mailto:moims-nav-exec at mailman.ccsds.org>" <moims-nav-exec at mailman.ccsds.org<mailto:moims-nav-exec at mailman.ccsds.org>>
Subject: [MOIMS-NAV-EXEC] Notional Events requirements from NAV WG

Particularly for Fran, Dale and Alain (but feedback from all welcomed):

Here’s a rough draft of the NAV WG requirements for us to send to Colin regarding the events message…


(1)     The elements of information that are *not* associated with timing systems that are in the current rough draft Events Message look okay;

(2)     In a parent segment, a global absolute reference epoch may be specified.

a.       For this reference epoch, the optional capability is required to specify the time scale upon which this absolute reference epoch is based.  If not specified, then the global absolute reference epoch’s time scale shall default to UTC.

(3)     Multiple events can be declared within a global object.

a.       For each of these events, the event’s timing may optionally be specified as relative or absolute.  If not specified, the event’s timing defaults to absolute.

b.       When absolute timing is used:

                                                               i.      The timescale of that event-unique absolute time may optionally be set.  If not specified, then the event-unique absolute reference epoch’s time scale shall default to UTC.

c.       When relative timing is used:

                                                               i.      An event-unique absolute reference epoch to which this relative timing is measured may optionally be specified.

                                                             ii.      If an event-unique absolute reference epoch is specified, then the time scale upon which that event-unique absolute reference epoch is based may optionally be specified.  If not specified, then the event-unique absolute reference epoch’s time scale shall default to UTC.

                                                            iii.      If an event-unique absolute reference epoch is not specified, then it is mandatory that a global absolute reference epoch is specified.

                                                            iv.      If both a global and an event-unique absolute reference epoch are specified, the event-unique absolute reference epoch shall override the global absolute reference epoch for that event.

                                                             v.      The timescale of the event relative time may optionally be set.  If not specified, then the timescale shall default to UTC seconds.

Thanks,

Dan

Daniel L. Oltrogge
SDC Program Manager & Senior Research Astrodynamicist
Center for Space Standards and Innovation
Analytical Graphics Incorporated
Voice: 719-482-4552; E-mail: oltrogge at agi.com<mailto:oltrogge at agi.com>

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