Other Satellite Navigation Systems - Understanding GPS: Principles and Applications - page 613

spacecraft, at the time of this writing, was projected to weigh 825 kg, half the
weight of the GLONASS-M spacecraft. The smaller mass will allow Russians to
launch GLONASS-K satellites six at a time on a single Proton launch vehicle, or two
at a time on a Soyuz launch vehicle. The satellites are also projected to have a design
lifetime of 10-12 years. The reduced mass and increased lifetime will reduce the
overall program launch and operating costs significantly [9-12, 16-19].
The navigation payload will be improved in several ways. The satellite atomic
clock is projected to provide improved stability on the order of 1 10 −14 . The satellite

will carry a third civil and military signal in the 1,190-1,212 MHz range, near GPS
L5. In addition to transmitting navigation-message data, the two new signals will
also transmit GLONASS integrity and GLONASS wide-area differential correction
information to enhance the accuracy and reliability of the navigation services.
GLONASS-K is also projected to carry an intersatellite link similar to the intersatellite
link planned for GLONASS-M (after the third satellite) [9-12, 16-18, 28].
The Russians also plan to add a new SAR payload to the GLONASS-K series.
The payload will relay the 406-MHz SAR beacon transmissions that are designed to
work with the currently deployed COSPAS-SARSAT system. This payload is simi-
lar in design and concept to the payload planned for the European GALILEO satel-
lite navigation system [9-12, 16-18].

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11.1.11.2 Differential GLONASS Improvements
The Russians have developed several types of GLONASS differential services. They
have deployed a coastal differential service for GLONASS and GPS using maritime
radio beacons, similar to other services set throughout most of the world. The Rus-
sians actively participated in RTCM Special Committee SC-104, which developed
the series of standards that permit the seamless use of DGPS, differential
GLONASS, and differential GPS/GLONASS services [1].
A second scheme proposes to use the network of the existing Russian Military
Space Force's Command and Control sites to double as differential reference sites.
At the time of this writing, the Russians had not provided any details on the status
or plans of the program. One advantage of this plan from the Russian perspective is
that it would use preexisting accurately surveyed sites as reference points. The plan
would also use the CSIC as a hub for computing differential corrections and extend-
ing the coverage over Asia, Europe, and Northern Africa. The differential radio
communications links to transmit the differential corrections currently have not
been selected or installed [5, 29].
A third scheme is comparable to the U.S. FAA plans for local-area differential
GPS for category II and III landing approaches. The Russians plan to use differential
GLONASS and differential GPS/GLONASS for categories I, II, and III, all catego-
ries of landing approach. At the time of this writing, the Russians indicated that they
were pursuing this concept but had not deployed ground equipment [3].
A fourth scheme proposes the use of the existing ground-based radionavigation
aid, Chaika, to transmit differential GLONASS corrections in addition to its navi-
gation service. Chaika is the Russian counterpart to Loran-C. This concept is simi-
lar to the Eurofix concept. The status of the Russian program is unclear, but is
discussed extensively in the 1994 CIS Federal Radionavigation Plan. The Russians