[Css-csts] FW: CCSDS SLE FCLTU ERT/LRT discrepancy

[Brian Safigan]

FYI - The Avtec implementation allows them to be equal

On May 6, 2010, at 10:07 PM, "John Pietras" <john.pietras at gst.com<mailto:john.pietras at gst.com>> wrote:

Wolfgang and Martin,
Jonathan Brasier appears to have discovered a discrepancy between the FCLTU spec and the FCLTU API spec. My off-the-cuff assessment would be that the Blue Book (912.1) takes precedence over the Magenta Book (916.1). However, that does beg the question as to what the implementations that are based on the API do?

John

From: Brasier, Jonathan [mailto:jbrasier at rtlogic.com]
Sent: Thursday, May 06, 2010 6:24 PM
To: John Pietras
Subject: CCSDS SLE FCLTU ERT/LRT discrepancy

John,

I’m the developer responsible for maintaining our SLE implementation here at RT Logic.

I was wondering if I could get a “ruling” from you on an inconsistency I’ve observed between two SLE FCLTU documents regarding the values of ERT and LRT within a CLTU-TRANSFER-DATA operation?  Or perhaps you would know to whom I should send this inquiry?

1.  According to CCSDS 912.1-B-2 paragraph 3.6.2.7.4, “If latest-radiation-time equals earliest-radiation-time, radiation shall occur at this time.”  Which implies that ERT can be equal to LRT.

2.  However, 916.1-M-1 section A3.2 contains a table with the heading “Checking of Invocation Parameters” (pg. A-13 in the October 2008 version) which implies that ERT may not be equal to LRT:

“earliest radiation time: if earliest and latest radiation times are set, must be earlier than latest radiation time”

“latest radiation time: if earliest and latest radiation times are set, must be later than earliest radiation time”

3.  To complicate matters, 916.1-M-1 contradicts itself in paragraph 3.1.4.1.1.a where it implies that ERT can be equal to LRT:

“if the ‘earliest radiation time’ and the ‘latest radiation time’ are both specified, the
‘earliest radiation time’ must not be later than the ‘latest radiation time’”

I was unable to find anything within these two documents which would indicate that one supersedes the other however, it’s quite possible it’s there and I overlooked it.

Which is correct?  ERT may equal LRT, or ERT may not equal LRT (i.e., ERT must always be earlier)?

Thank you,
Jonathan Brasier
RT Logic

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