Re: [LEAPSECS] Problems with GLONASS Raw Receiver Data at Start of New Year

From: Rob Seaman <seaman_at_NOAO.EDU>
Date: Sat, 14 Jan 2006 08:45:29 -0700

On Jan 13, 2006, at 7:51 AM, Richard Langley wrote:

> The International GNSS Service (IGS) includes a sub-network of
> continuously
> operating GLONASS monitor stations (about 50) including one at the
> University
> of New Brunswick (UNB1). At UNB1 we lost C1 (coarse code on L1
> frequencies),
> P1 (precision code on L1), and P2 (precision code on L2)
> observations on the 5
> GLONASS satellites we were tracking at 00:01:30 GPS Time on 1
> January 2006
> along with phase jumps in L1 (carrier phase on L1) and L2 (carrier
> phase on
> L2).

Perhaps you can expand on the meaning of all this. Presumably this
would represent an infrequent occurrence? What are the implications
for downstream systems? For that matter, what systems lie downstream?

> Code measurements were back at 00:04:00.

So the problem extended for 2.5 hours from 00:01:30 - 00:04:00 GPS
Time? Were there repercussions that have persisted after this?

> I have just learned from one of the IGS analysis centres that all
> January 1
> IGS GLONASS observation files that they checked show a similar
> problem.

The leap second has not been mentioned, but presumably we are to
infer that it triggered this behavior? Would be absolutely delighted
to learn more about the IGS, both in general and to provide context
for interpreting this report.

As with the previous mail, I won't claim to be able to attach an
estimation of the importance of the events described. We obviously
all believe leap seconds are worthy of discussion or we wouldn't be
here. I presume many of us read RISKS Digest and can dream up scary
scenarios. But there are also risks associated with *not* having
leap seconds, with allowing DUT1 to increase beyond 0.9s, for
instance. And events triggered by those risks would not draw
worldwide scrutiny - they could occur year-round and the media circus
would have moved on.

Rob Seaman
NOAO
Received on Sat Jan 14 2006 - 07:45:45 PST