[IGSMAIL-5574]: Three new GLONASS-M satellites active

[Stefan Schaer]

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IGS Electronic Mail      12 Mar 04:19:27 PDT 2007      Message Number 5574
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Author: Stefan Schaer


Dear IGS/IGLOS colleagues,

We got confronted with first IGS/IGLOS tracking data of the three new
GLONASS-M satellites launched on 25 Dec 2006, namely:
   R14 (715) on 06 Feb 2007 (day 037)
   R10 (717) on 15 Feb 2007 (day 046)
   R15 (716) on 16 Feb 2007 (day 047)

See also:
   http://www.aiub.unibe.ch/download/igsdata/y2007/odata_glonass_d037.txt
   http://www.aiub.unibe.ch/download/igsdata/y2007/odata_glonass_d038.txt
   http://www.aiub.unibe.ch/download/igsdata/y2007/odata_glonass_d046.txt
   http://www.aiub.unibe.ch/download/igsdata/y2007/odata_glonass_d047.txt

With these three new satellites, the GLONASS-M constellation now
consists of 7 satellites: R06, R07, R10, R14, R15, R23, R24.

Remark: We observed a minor GLONASS tracking data anomaly on days 043
through 045: a particular receiver model reported R14 incorrectly as
R10.

The CODE GNSS orbit products include currently up to 47 satellites (31
GPS plus 16 GLONASS). The following GLONASS satellites may be declared
as active (not all of them are marked usable):
   R01 (796)
   R02 (794)
   R03 (789)
   R04 (795)
   R06 (701)
   R07 (712)
   R08 (797)
   R10 (717)
   R14 (715)
   R15 (716)
   R18 (783)
   R19 (798)
   R21 (792)
   R22 (791)
   R23 (714)
   R24 (713)
Inactive are:
   R05 (711)
   R17 (787)
   R20 (793)

Note that the GLONASS status page (dated March 9, 2006) does not yet
reflect the mentioned satellite constellation change:
 
http://www.glonass-ianc.rsa.ru/pls/htmldb/glonass.collectors_content.get_cys_en_as_txt

The three new GLONASS-M satellites are still marked unusable. This is
the reason why corresponding tracking data is available just from a
subnetwork of AIV tracking receivers. None of the Ashtech Z18 receivers
did recognize one of the new GLONASS-M until now (they seem to track
currently at most 10 of 16 GLONASS satellites). More alarming is the
fact that R15, transmitting on frequency channel 0, is sampled solely by
one IGS/IGLOS receiver model (Trimble NetR5)! At CODE, we perform POD
for R15 on the basis of one single Trimble NetR5 receiver baseline.

In this context, the following questions arise:
- Are specific receiver models able to track R15 after it becomes marked
   usable?
- What about negative frequency channel numbers to be expected in the
   (near) future?
- Is it possible to upgrade the firmware at legacy receiver models to
   allow sampling of GLONASS satellites transmitting on frequency
   channel numbers 0, -1, ..., -7?

Additional remark: Trimble NetR5 receivers, when configured for AIV
tracking, are able to exclusively provide R15 observations. However,
they use to provide also observations (often incomplete observation
records) with respect to, e.g., R05, R17, R20, observations which must
be considered fictitious. This problem is irrelevant to our analysis,
but important when comparing satellite tracking data availability
between the various GNSS receiver models.

Best regards,

The CODE AC Team