Indian space agency ISRO launched yesterday their last navigation satellite from IRNSS series on atop of PSLV launch vehicle. Launch was performed from first launch pad in Satish Dhawan Space Center at 07:20 GMT. Just as during previous missions of IRNSS satellites, ISRO decided to rely on their PSLV XL rocket.
IRNSS stands for Indian Regional Navigation Satellite System and is independently developed navigation system for Indian military and emergency services. It was design to provide navigational services in real time with precision up to 10 m on Indian Territory with surrounding regions up to 1500 km from Indian boarders. Its development started in 2010 and first satellite, IRNSS-1A, was launched on 1 July 2013 from Satish Dhawan Space Center on atop of PSLV XL rocket. IRNSS-1G is seventh and ultimate satellite from series, which makes possible starting and operating IRNSS with its full potential.
Preparing to mission passed without any delays, but ISRO confirmed in statement quoted by "The New Indian Express" that small issues with checks before flight appeared:
"During the electrical checks of the launch vehicle, an anomaly was observed in one of the electro-hydraulic control actuators in the second stage. It has been decided to replace this actuator."
35th flight of PSLV started with rocket lift off at 07:20 GMT and according to flight plan after T+1' boosters started to separate; booster 1 and 2 separated at T+1'9"90'", 3 and 4 at T+1'10"10"' and 5 and 6 separated at T+1'32". First stage separated at T+1'50"12'" and second stage ignited at T+1'50"32"'. Payload fairing was jettisoned at T+3'19"92'" and second stage separated one minute after, at T+4'22"04"'. Ignition of third stage started at T+4'23"24"' and lasted for seven minutes until at T+11'3"2'" third stage separated. Propulsion of the fourth stage was started at T+11'13"20"' and was shut down at T+19'42"02'". Final deployment of the IRNSS-1G took place at T+20'19"02"'.
After yesterdays launch constellation of IRNSS looks as follow (data provided by ISRO):
- IRNSS-1A - with planned operational life for 10 years, launched on atop of PSLV XL on July 1, 2013; placed on GEO slot 55° East, on altitude of 35,706.1 km
- IRNSS-1B - with planned operational life for 10 years, launched on atop of PSLV XL on July 4, 2014; placed on GEO slot 31° East, on altitude of 35,714 km
- IRNSS-1C - with planned operational life for 10 years, launched on atop of PSLV XL on 15 October, 2014; placed on GEO slot 83° East, with perigee at 35697 km and apogee at 35889 km with inclination at 17.86°
- IRNSS-1D - with planned operational life for 12 years, launched on atop of PSLV XL on 5 May, 2015; placed on GEO slot 111.75° East, with perigee at 35750 km and apogee at 35884.1 km with inclination at 19.2°
- IRNSS-1E - with planned operational life for 12 years, launched on atop of PSLV on 20 January, 2016; placed on GEO slot 111.75° East, with perigee at 35708 km and apogee at 35882 km with inclination at 19.2°
- IRNSS-1F - with planned operational life for 12 years, launched on atop of PSLV XL on 10 March, 2016; placed on GEO slot 32.5° East, with perigee at 284 km and apogee at 20657 km with inclination at 17.86°
- IRNSS-1G - with planned operational life for 12 years, launched on atop of PSLV XL on 28 April, 2016; placed on GEO slot 129.5° East, with perigee at 254 km and apogee at 20657 km with inclination at 17.86°
Satellites are generally based on I-1000 bus developed by ISRO. Satellites weigh 1425 kg and are equipped with solar arrays and onboard lithium battery (with capacity of 90 Ah) to provide 1660 w of power. Outer dimensions with folded solar arrays are 158 cm x 150 cm x 150 cm. Liquid Apogee Motor for final injection is generating thrust at 440 N and is supported by twelve 22 N thrusters for performing maneuvers. Three axis attitude control system is based on sun and star sensors along with gyroscopes combined with reaction wheels and magnetic torquers; attitude control system also could utilize twelve 22 N thrusters. Each satellite is equipped with Rubidium atomic clock, C band transponder for satellite ranging and navigation payload which will transmit signal to Earth on L5 band (1176.45 MHz) and on S band (2492.028 MHz).
PSLV XL is extended version of Polar Satellite Launch Vehicle which was developed by Vikram Sarabhai Space Centre in the beginning of the nineties as expandable solid/liquid fueled launch vehicle. Rocket was considered as launch vehicle for Indian remote sensing and communication satellites to give India independent access to space. Maiden flight of PSLV was performed on 20 September 1993. PSLV XL was upgraded with larger six strap-on boosters. Rocket weighs 320 t at start (comparing to 295 t of PSLV-G) and its solid propellant is HTPB. Boosters are height is 13.5 m with diameter at 1 m and have 30% more fuel (12200 kg) than regular boosters of PSLV. Central core has four stages: first stage (with mass at 138200 kg, diameter at 2.8 m and length of 20 m) is powered by solid fueled (HTPB) S139 engine with 4800 kN of thrust. Second stage (weight at 24000 kg, diameter at 2.8 m and long for 12.8 m) is equipped with one Vikas engine liquid fueled with N2O4/UDMH and providing 799 kN of thrust. Third stage (mass at 7600 kg, diameter at 2 m and length of 3.6 m) is solid fueled with single HPS3 engine which generates 240 kN of thrust. Fourth stage is powered by two L-2-5 engines with thrust at 15.2 kN fueled with liquid MMH/MON propellant and weighs 2500 kg while its length is at 3 m and diameter at 1.3 m. PSLV XL is able to lift up to 1425 kg to GTO orbit.