[LEAPSECS] Leap Second and GNSS Probems

Richard B. Langley lang at unb.ca
Wed Jul 4 12:12:12 EDT 2012

One of the continuously operating GNSS receivers at UNB had trouble
with the GLONASS satellites after the leap second. A top-of-the-line
Trimble NetR9 GNSS infrastructure receiver stopped tracking GLONASS
satellites at 00:00:17 UTC on 1 July. Tracking on two satellites was
recovered within seconds but some satellites were not recovered for up
to an hour or more. This can be seen in the following plot of GLONASS
satellite observability with 30-second epochs stretching from one hour
before the leap second until one hour after (time scale is referenced
to GPS System Time; PRN number is actually orbital slot number):

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More detail in the vicinity of the leap second is possible using the
high-rate (1 Hz) data from the receiver with the plot available in a
different format (again, time scale is referenced to GPS System
Time--16 seconds ahead of UTC after the leap second):

SV
+
-----------|
-----------|-----------|-----------|-----------|-----------|+ SV
R 1|NNNNN NNNNN NNNNN NN NNNN NNNNN NNNNN NNNNN NNNNN NNNNN NNNNN
NNNNNN|R 1
R18|NNNNN NNNNN NNNNN
NN |R18
R 3|NNNNN NNNNN NNNNN
NN |R 3
R17|NNNNN NNNNN NNNNN
NN |R17
R15|NNNNN NNNNN NNNNN NN NNNNN NNNNN NNNNN NNNNN
NNNNNN|R15
R16|NNNNN NNNNN NNNNN
NN |R16
R 2|NNNNN NNNNN NNNNN
NN |R 2
R 9|NNNNN NNNNN NNNNN
NN |R 9
R19|NNNNN NNNNN NNNNN
NN |R19
Obs|99999 99999 99999 99 1111 11111 11111 22222 22222 22222 22222
222222|Obs
Clk

|

|
Clk

+
-----------|
-----------|-----------|-----------|-----------|-----------|+
00

:

00

00:01
2012 Jul 1
2012 Jul 1

The receiver had no difficulty in tracking GPS satellites through the
leap second.

A more than 10-year-old Javad GPS/GLONASS receiver had no difficulty
in tracking GLONASS satellites through the leap second event. We are
currently assessing the quality of the data from this receiver around
the time of the leap second.

-- Richard

On 1-Jul-12, at 11:24 PM, Richard B. Langley wrote:


> A u-blox 6 GPS Engine did not play nice with the leap second. This

> new engine is GPS/SBAS/QZSS/GLONASS compatible but it only runs in

> either GPS/SBAS/QZSS mode or GLONASS mode. I was running it under

> GLONASS mode for the leap second check and recording its NMEA

> messages. Just before the leap second, it was tracking 9 satellites.

> At the leap second it reset itself. I don't know if this was caused

> by an error associated with the leap second or the receiver was

> programmed to do this. At second 0 of 1 July, it ceased positioning

> and did not know the time (at least no information was in the $GLZDA

> NMEA message). At 00:00:40.48 seconds, it once again knew UTC, and

> by 00:02:39.00, it was tracking enough GLONASS satellites (4) to

> report position information again. Extracted $GLGGA and $GLZDA

> messages from before and after the leap second are in the appended

> file.

> I'll be contacting u-blox to report the behaviour.

>

> Note that when I was monitoring a previous leap second with a GPS-

> only u-blox receiver, it sailed through the leap second with no

> problem:

> $GPZDA,235955.00,31,12,2005,00,00*6D

> $GPZDA,235956.00,31,12,2005,00,00*6E

> $GPZDA,235957.00,31,12,2005,00,00*6F

> $GPZDA,235958.00,31,12,2005,00,00*60

> $GPZDA,235959.00,31,12,2005,00,00*61

> $GPZDA,235960.00,31,12,2005,00,00*6B

> $GPZDA,000000.00,01,01,2006,00,00*62

> $GPZDA,000001.00,01,01,2006,00,00*63

> $GPZDA,000002.00,01,01,2006,00,00*60

> $GPZDA,000003.00,01,01,2006,00,00*61

> $GPZDA,000004.00,01,01,2006,00,00*66

> $GPZDA,000005.00,01,01,2006,00,00*67

>

> We may have had trouble tracking GLONASS satellites with some of the

> continuously operating GNSS receivers operating at UNB and the

> Russian Space Agency may have had trouble monitoring the GLONASS

> satellites. I'll report on these anomalies later.

>

> -- Richard

>

> -----------------------------------------------------------------------------

> | Richard B. Langley E-mail:

> lang at unb.ca |

> | Geodetic Research Laboratory Web: http://www.unb.ca/GGE/

> |

> | Dept. of Geodesy and Geomatics Engineering Phone: +1 506

> 453-5142 |

> | University of New Brunswick Fax: +1 506

> 453-4943 |

> | Fredericton, N.B., Canada E3B

> 5A3 |

> | Fredericton? Where's that? See: http://

> www.fredericton.ca/ |

> -----------------------------------------------------------------------------

>

> -----------------------------------------------------------------------------

> | Richard B. Langley E-mail:

> lang at unb.ca |

> | Geodetic Research Laboratory Web: http://www.unb.ca/GGE/

> |

> | Dept. of Geodesy and Geomatics Engineering Phone: +1 506

> 453-5142 |

> | University of New Brunswick Fax: +1 506

> 453-4943 |

> | Fredericton, N.B., Canada E3B

> 5A3 |

> | Fredericton? Where's that? See: http://

> www.fredericton.ca/ |

> -----------------------------------------------------------------------------

> <output.txt>_______________________________________________

> LEAPSECS mailing list

> LEAPSECS at leapsecond.com

> http://six.pairlist.net/mailman/listinfo/leapsecs


-----------------------------------------------------------------------------

| Richard B. Langley E-mail:

lang at unb.ca |

| Geodetic Research Laboratory Web: http://www.unb.ca/GGE/

|

| Dept. of Geodesy and Geomatics Engineering Phone: +1 506

453-5142 |

| University of New Brunswick Fax: +1 506

453-4943 |

| Fredericton, N.B., Canada E3B

5A3 |

| Fredericton? Where's that? See: http://

www.fredericton.ca/ |
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