”India and Russia signed an agreement to share high-precision signals from the Global Navigation Satellite Syatem(GLONASS) for defence as well as civilian use. As per the agreement, Russia will provide access to the GLONASS high-precision navigation signals to India. The Russian Federal Space Agency Roscosmos, the Indian Space Research Organisation (ISRO) and Russian Navigation Information Syatems (NIS) GLONASS signed a 'Memorandum of Cooperation'. The representatives from NIS-GLONASS and ISRO's commercial arm, Antrix Corporation, agreed to setup a joint venture providing navigation and information services on the GLONASS/GPS platform.”
GLONASS (Global Navigation Satellite System) is a global position Satellite System realized by ex-Urss at the same time with the United State's GPS(Global Positioning System).
Why GLONASS?
The purpose of the Global Navigation Satellite System GLONASS is to provide unlimited number of air, marine, and any other type of users with all-weather three-dimensional positioning, velocity measuring and timing anywhere in the world or near-earth space.
Completely deployed GLONASS constellation is composed of 24 satellites in three orbital planes whose ascending nodes are 120 apart. 8 satellites are equally spaced in each plane with argument of latitude displacement 45. The orbital planes have 15 -argument of latitude displacement relative to each other. The satellites operate in circular 19100-km orbits at an inclination 64.8, and each satellite completes the orbit in approximately 11 hours 15 minutes. The spacing of the satellites allows providing continuous and global coverage of the terrestrial surface and the near-earth space.
The control segment includes the System Control Center and the network of the Command and Tracking Stations that are located throughout the territory of Russia. The control segment provides monitoring of GLONASS constellation status, correction to the orbital parameters and navigation data uploading.
User equipment consists of receives and processors receiving and processing the GLONASS navigation signals, and allows user to calculate the coordinates, velocity and time.
Navigation determination concept
User equipment performs passive measurements of pseudoranges and pseudorange rate of four (three) GLONASS satellites as well as receives and processes navigation messages contained within navigation signals of the satellites. The navigation message describes position of the satellites both in space and in time.
Combined processing of the measurements and the navigation messages of the four (three) GLONASS satellites allows user to determine three (two) position coordinates, three (two) velocity vector constituents, and to refer user time scale to the National Reference of Coordinated Universal Time UTC(SU).
The data ensuring of sessions scheduling for navigational determinations, selection of working "constellation" of SVs and detection of radiosignals transmitted by them, are transmitted as a part of the navigation message.
Basic System Design of GLONASS:
As with GPS, the GLONASS system uses a satellite constellation to provide, ideally, a GLONASS
receiver with six to twelve satellites at most times. A minimum of four satellites in view allows a GLONASS receiver to compute its position in three dimensions, as well as become synchronized to the system time.
The GLONASS system design consists of three parts:
- The Control segment(Ground-based control facilities)
- The Space segment(Constellation of satellites)
- The User segment(User equipment)
All these parts operate together to provide accurate three-dimensional positioning, timing and velocity data to users worldwide.
The Control Segment
The Control Segment consists of the system control center and a network of command tracking stations across Russia. The GLONASS control segment, similar to GPS, must monitor the status of satellites, determine the ephemerides and satellite clock offsets with respect to GLONASS time and UTC Coordinated Universal Time), and twice a day upload the navigation data to the satellites.
The Space Segment
The Space Segment is the portion of the GLONASS system that is located in space, that is, the GLONASS satellites that provide GLONASS ranging information. When complete, this segment will consist of 24 satellites in three orbital planes, with eight satellites per plane. Figure 1 on Page 3 shows a combined GPS and GLONASS satellite system.
The User Segment
The User Segment consists of equipment (such as a NovAtel OEMV family receiver) that tracks and receives the satellite signals. This equipment must be capable of simultaneously processing the signals from a minimum of four satellites to obtain accurate position, velocity and timing measurements. Like GPS, GLONASS is a dual military/civilian-use system. The system’s potential civil applications are many and mirror those of GPS.
0 Leave / View your comment:
Post a Comment