Ground segment of GAGAN i.e. Indian
Reference Station (INRES) at Delhi,
Kolkatta, Guwahati, Portblair, Ahmedabad,
Banglore, Jammu and Trivanthapuram is
in place. Except Portblair, other stations
have been connected to Indian Master
Control Center (INMCC) with fiber optic
cable in synchronous loop mode. Portblair
is connected through dedicated satellite
communication network. Its integration
and connectivity test with seven INRES
with INMCC have been completed. The
INRES data is being received through
fiber optic cable at INMCC Banglore
for corrections and validation checks
of the erroneous data. Preliminary Site
Acceptance Test (PSAT) of GAGAN
ground element was conducted in May
2006 with help of satellite emulator.
The Ground segment of GAGAN is
expected to be integrated with INMARSAT
4F1 till April 2008 and GSAT would be
available for GAGAN ground segment
integration by August 2008. The user level
testing of GAGAN has been completed in
May 2007. The Final Site Acceptance Test
(FSAT) of GAGAN system was completed
in August 2007. The GAGAN signal is
available for testing and trial. The PRN
of GAGAN GEO is 127 and continuously
broadcasting correction data for users.
The installation of
GPS-TEC at all 20
stations has been
completed at 5° x
5° grid size. The
IONO data is being
collected on the basis
of 24x7x365 basis for
last for years and has
been archived at ISRO
space application
center Ahmadabad.
Ionospheric data from
20 TEC stations are
being analyzed by
a number of Indian
universities and R&Dinstitutions involved in ionospheric studies
for development IONO-TROPO model
that is suitable for Indian airspace. As
per current analysis results, 5 more TEC
stations are recommended for equatorial
anomaly region which will from 2° x 2°
gird size, to achieve better IONO model
in the equatorial anomaly region.
The TDS phase results are to demonstrate
the expected vertical and horizontal
positional accuracies over 95% of
the time with the associated Time-toalarm
(TTA) capability. Results were
better than 7.6 meters accuracies in
both vertical and horizontal over 95%
of the time within the perimeter of the
reference stations. Using type 62 (test)
messages, the TTA was better than 6.2
seconds. Results were well within the exit
criteria set by ISRO and M/s Raytheon
and exhibited good performance.
Flight trials are scheduled in first quarter
of 2008, to check the integrity of the
up linked GAGAN signals. DGCA
(India) officials are involved in the
training process for certification of the
system and preparation of certification
documents. In November-2006, FAA
and AAI have signed MOC for GAGAN
certification and validation of SIS.
Finally, ISRO in association with the
AAI will be developing the entire
system through all the stages of TDSExtended,
and Final Operation Phase
(FOP). The final FOP document is under
review. ISRO will continue to provide
technology support, maintenance and
replenishment of the space segment of
the system, as and when required, to
maintain the system as a robust system.
Total cost of the GAGAN project
is Rs 644.00 Crores (140 m USD)
GAGAN Coverage is in TDS Phase on
24 Hours availability. Less coverage
due to non-implementation of
regional IONO-TROPO Model.
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