With the launching of
GSAT 7
on August 30, 2012 India gets its
first dedicated defence satellite, getting
into a subtle civil-defence partnership. It's a spacecraft
dedicated to Indian
Navy because of its space bound marine communications. The satellite soared for
34 minutes before getting into the Geosynchronous Transfer Orbit (GTO) of 249 km
perigee, 35,929 km apogee as well as an inclination of 3.5 degree with regards
to the equator (Perigee and Apogee are the distances of the satellite from the
earth, across the GTO, with former being the nearest and also the latter being
the farthest).
- Inside a five days period (Aug 31st to Sep 4th) the
satellite had completed three orbit raising manoeuvres (manned from ISRO) which
to set up simple words is the utilization of propulsion systems to change the
orbit of the spacecraft. Ending this the satellite was finally injected right
into a geosynchronous orbit 36,000 kms over the earth’s surface. The satellite
will be positioned in its destination slot of 74 degree east longitude by Sept
14th 2013.
- The satellite premiered from Kourou spaceport in French Guiana
while using French company Ariansespace’s Ariane 5 rocket launcher. (The
organization was established in 1980 because the world’s first commercial launch
services provider).
- Together with GSAT 7, the launcher also orbited another
spacecraft EUTELSAT 25B/Es'hail.
Geosynchronous Transfer Orbit (GTO): is
medium difficulty orbit used to reach the destined geosynchronous or
geostationary orbit while
using satellite’s engine. The latitudinal angle of the
geosynchronous orbit is maintained with respect to the equator.
Bands
based on the satellite: The satellite carries payloads operating in
UHF, S, C
and Ku bands.
A GSAT uses transponder i.e. a tool which helps in
magnifying a frequency signal or changing a frequency from the earth and
reflecting it well to any location on earth’s surface.
The microwave spectrum
ranges from 1 giga hertz to 100 giga hertz with many common applications lying
within 1-40 GHz (L, S, C, X, Ku, K, Ka Bands).
Services Offered: A range of
services which would be delivered when the satellite becomes functional ranges
from low bit rate voice/fax/data to high bit rate enhanced audio/video/data
communication capabilities over vast marine areas and Indian terrestrial
areas.
This could come as an aid in search and rescue operations,
distress forewarning, weather forecasting, data relaying, etc.
India’s GSLV
Programme: India continues to be developing its Geosynchronous Launch Vehicles
by means of three generations with all the launches being conducted from Satish
Dhawan Space Centre in Sriharikota:
1) GSLV Mark I - 1-2 tonne GSAT
launching capacity had following launches under it:
MK I (a) : GSLV D1
didn't place GSAT 1 in GTO in April 2001
Mk I (a) : GSLV D2 placed GSAT2 in
May 2003
Mk I(b): GSLV F01 placed GSAT 3 (EDUCAT) in September 2004
Mk
I(b): GSLV F02 was unsuccessful in launching INSAT 4C in the year 2006
Mk
I(b): GSLV F04 failed partially to produce INSAT-4CR in 2007
Mk I( c ) : GSLV
D4 didn't launch GSAT 5P in Dec 2010.
2) GSLV Mark II - 2-3 tonne GSAT
launching capacity had following launches under it:
GSLV D3 - It had been
the first Indian rocket operated by indigenously built cryogenic engine. It was
to place GSAT 4, a 2220 kg communication satellite in GTO in Apr 2010 however
was not successful due to non-ignition from the cryogenic stage.
GSLV D5 - It
was to put GSAT 14 into 74 degree east longitude to assist provisioning of a
number of satellite based services viz. tele-education, telemedicine, etc
however the launch was called off as a result of leakage in the second liquid
stage throughout the pre-launch pressurisation phase. It has been rescheduled
for Dec 2013.
3) GSLV Mark III - Heaviest and many powerful launch vehicle
asia which can place 4-5 tonne or heavier satellites.
India’s Three Stage
Cryogenic Engine: ISRO is yet to check successfully our indigenous three stage
cryogenic engine that is a requisite for launch of heavy satellites for example
GSAT 7. Our home grown GSLV is really a three stage vehicle that's 49 metre
tall, with a lift-off weight of 414 tonne.
First stage includes S125
solid booster with four liquid (L40) strap-on motors i.e. solid fuel
based.
Second stage (GS2) is liquid engine which supplies a better
thrust.
Third stage (GS3) may be the cryogenic stage, which is more efficient
when compared to liquid stage in PSLV and uses cryogenic fuel - liquid hydrogen
at -253 degree Celsius which utilizes surrounding air to boil and expand like a
gas to more than 1000 times its volume. It offers one and a half times extra
thrust than solid and liquid propellant and also at the same time weighs 50%
less thereby enhancing the payload capacity of the launch vehicle.
Initially,
India was acquiring Cryogenic Engine from Russian Space Agency. But, Russia
refused to own technology to India within the wake of pressure in the USA,
fearing that India can use the technology to develop long-range missiles. ISRO
has been developing fraxel treatments since 1993. Testing of cryogenic rocket
engine in India has been carried out at Liquid Propulsion System Centre (LPSC)
in Mahendragiri, Tamil Nadu underneath the banner Cryogenic Upper Stage Project
(CUSP).
To date, only USA, European Space Agency, Russia, China and Japan
happen to be successful at developing their very own cryogenic engine
technologies. Hope is the fact that India would join their league soon.
Indigenous technologies aside from providing an edge to India would also reduce
our expenditures to some great deal. But unless there's two such successful test
flights, the hopes are minimal too.
