NavIC - Indian Regional Navigation Satellite System (IRNSS)

Introduction

ISRO is developing a satellite based navigation system, called Indian Regional Navigation Satellite System (IRNSS), with a constellation of 7 satellites and complementary ground infrastructure. Four spare satellites are also planned.

The IRNSS system is planned to be made operational by end of 2014. Government has approved the IRNSS project at a total cost of Rs. 1420.00 crores in May 2006 for both space and ground infrastructure. 

Accuracy and Coverage

The IRNSS is expected to provide positional accuracies similar to the Global Positioning System (10 m over Indian landmass and 20 m over the Indian Ocean) in a region centered around the country with a coverage extending up to 1,500 km from India between longitude 40° E to 140° E and between latitude ± 40°.

Besides accurate real time position, the system is designed to provide Navigation and Time (PNT) services to users on a variety of platforms with 24x7 service availability under all weather conditions.

As in the case of GPS, IRNSS will provide a more accurate restricted service for special authorized users.

IRNSS Features

  1. Highly accurate position, velocity and time information in real time for authorized users on a variety of vehicles
  2. Data with good accuracy for a single frequency user with the help of Ionospheric corrections
  3. All weather operation on a 24 hour basis.
IRNSS-1A
IRNSS-1A before launch on July 1, 2013.

Architecture

The INRSS will consist of three segments: space, ground and user. 

The space segment consists of a constellation of seven satellites: three (Geostationary Orbit) GEOs located at 34° E, 83° E and 131.5° E and four (Gyosynchronous Orbit) GSOs at an inclination angle of 29° placed two each at with equator crossing at 55° and 111° East. 

IRNSS ground segment consists ground stations for generation and transmission of navigation parameters, satellite control, satellite ranging and monitoring. A total of 20 stations are planned, most of them located at airports along with GAGAN ground elements. 

The ground segment ranging stations provide data for the orbital determination of the satellites and monitoring of the navigation signal.

IRNSS will have the two Master Control Stations (MCS), which may be co-located with GAGAN INMCC. 

IRNSS will have two types of signals in L5 (1176.45 MHz) & S (2492.028 MHz) band.  Both L5 and S-band consists of two downlinks.  

IRNSS provides two basic services such as Standard Positioning Service (SPS) for common civilian users and Restricted Service (RS) for special authorized users

The system can be augmented with local area augmentation for higher accuracy.

IRNSS Satellites

Each IRNSS satellite will weigh about 1,380 kg and their solar panels generate 1,400 Watt of power. The satellites will be configured with an optimized I-1K bus (compatible for launch onboard PSLV) with a power handling capability of around 1600W 

The satellite is designed for a nominal life of 7 years. Its payload will consist of electronic equipment to generate navigation signals and extremely accurate on-board atomic clocks. The navigation signals in S-band (2-4 GHz) are fed to a high performance phased array antenna for the required coverage. There is a ranging payload consisting of a C-band transponder that facilitates accurate determination of the range of the satellite. IRNSS satellites also carry CDMA ranging instruments and corner-cube retro-reflectors for laser ranging.  

IRNSS Ground Segment

A number of ground stations responsible for the generation and transmission of navigation parameters, satellite ranging and monitoring, etc., have been established in eighteen locations across the country. 

IRNSS Constellation Progress

The full constellation of 7 satellites was realized with the launch of IRNSS-1G in May 2016.

IRNSS-1A


IRNSS-1A was launched on-board PSLV-C22XL at 11:41 PM on July 1, 2013. It was ISRO's first night launch.

The PSLV-C22XL launcher injected the satellite into the intended elliptical orbit of 282.46 km X 20,625.37 km after a flight of 20 minutes 17 seconds.

After injection, the solar panels of IRNSS-1A were deployed automatically. ISRO’s Master Control Facility (at Hassan, Karnataka) then assumed control of the satellite. 

IRNSS Satellite Componentts
IRNSS Satellite Components. Credit: ISRO

After five orbit raising maneuvers using Apogee Motor Firing (AMF), on July 06, 2013 at 16:57 hrs (IST) the satellite was placed in Geo Synchronous Orbit (GSO) with 27 deg inclination at 44 deg E longitude.

The current orbital parameters are : apogee 35,870 km, perigee 35,484 km and orbital period is 23h 50m.

The launch was earlier scheduled for Jun 12, 2013, but was postponed following a glitch in the second stage electro hydraulic actuator that surfaced during integration checks, mandating a replacement of the actuator.

(It was earlier announced the satellite would be launched in May 2013.)

IRNSS-1B



IRNSS-1B


 Orbital Parameters  Geosynchronous, at 55-E longitude with 29-deg inclination
 Lift off mass  1432 kg
 Dry mass      614 kg
 Dimensions  1.58-m x 1.50-m x 1.50-m
 Power      Two solar panels generating 1660 W, one Li ion 90 AH battery
 Propulsion  440-N LAM, 12 x 22-N thrusters
 Control System  Zero momentum system: orientation input from Sun and Star sensors and gyroscopes, Reaction Wheels, Magnetic torquers and 22-N thrusters as actuators.
 Mission Life  10-yr

Integration of IRNSS-1B with launch vehicle PSLV C24 started on December 27. 

On April 4, 2014, PSLV-C24 injected IRNSS-1B into sub Geosynchronous Transfer Orbit (sub GTO) with impressive accuracy - 283-km (planned 284-km) perigee, 20,630-km (planned 20,650-km) apogee, 19.2-deg inclination, and 178.26 (planned 178.2) argument of perigee. 

The launch marked the 25th consecutive successful mission of the PSLV; the sixth of its XL variant, which has earlier been used to launch Chandrayaan-1, GSAT-12, RISAT-1, IRNSS-1A and Mars Orbiter Spacecraft. 

Following orbital insertion, the satellite's two solar panels deployed automatically. MCF Hassan took control of the satellite. 

At 5.35 PM on April 5, 2014 MCF commanded a seven minutes and a half burn of the LAM to raise the orbit of IRNSS-1B to 299-km perigee and 24,760-km apogee. 

On April 6, 2014 afternoon, second orbit raising LAM burn of 790 sec raised IRNSS-IB's orbit to 349-km perigee and 35965-km apogee. 

On April 7, 2014, a third orbit raising burn of the LAM for 2096 seconds raised the orbit to 11668-km perigee, 35924 km apogee and 27-deg inclination.

On April 8, a fourth orbit raising burn of the LAM for 1270-sec raised the orbit of IRNSS-1B to 31664-km perigee, 35931-km apogee and 30.7-deg inclination.

On April 9, the fifth and final orbit raising burn of the LAM for 134.4-sec eased the orbit of IRNSS-1B to  35328-km perigee, 35931-km apogee and 30.9-deg inclination.  The satellite would now be allowed to drift to its GSO slot at 55-deg E longitude.

(Before launch, ISRO planned five orbit raising maneuvers - two at the perigee and three at apogee - using the satellite's Liquid Apogee Motor (LAM) to place the satellite into its circular geosynchronous orbit at 55-deg East with an inclination of 31-deg with respect to the equator.

On April 23, 2014, ISRO announced that IRNSS-1B satellite has been successfully placed at 55 deg East longitude, collocated with IRNSS-1A and GSAT-8 satellites. IRNSS-1B satellite performance is normal.

IRNSS-IB being integrated with PSLV-C24


IRNSS-1B carries two types of payloads - navigation and ranging. 

The navigation payload operates in L5 band (1176.45 MHz) and S band (2492.028 MHz) and includes a highly accurate Rubidium atomic clock. 

The ranging payload consists of a C-band transponder to accurately determine the range of the satellite. IRNSS-1B also carries Corner Cube Retro Reflectors for laser ranging. 


IRNSS-1C

ISRO reported on November 26, 2014 that the health of IRNSS -1C spacecraft is normal. All the subsystems are functioning normally. The characterisation of navigation payloads and TTC systems were completed and the navigation information are regularly sent to the spacecraft.

Fourth Orbit Raising Apogee Motor Burn

The fourth orbit raising was successfully accomplished by firing the Apogee Motor for 178-sec in the evening of October 19, 2014, altering orbital parameters to - Perigee Altitude: 35647 km, Apogee Altitude: 35718 km. Orbit period: 23hr 50min 47.14sec.

Third Orbit Raising Apogee Motor Burn October  19, 2014

The third orbit raising was successfully accomplished with a 31-min Apogee Motor burn in the evening of October 18, 2014, altering orbital parameters to - Perigee Altitude: 30853 km, Apogee Altitude: 35647 km. Orbit period: 21hr 48min 31.76sec.

Second Orbit Raising Apogee Mootr Burn October  18, 2014

The second orbit raising was successfully accomplished with a 23-min burn of the Apogee Motor in the evening of October 17, 2014, altering orbital parameters to - Perigee Altitude: 7187 km, Apogee Altitude: 35634 km. Orbit period: 12hr 48min 22.4sec.

First Orbit Raising Apogee Mootr Burn October  17, 2014

The first orbit raising was successfully accomplished by firing the Apogee Motor for 20 minutes, in the early morning of October 17, 2014, altering orbital parameters to: -Perigee Altitude: 320.5 km, Apogee Altitude: 35732.4 km

Launch

The satellite was launched at 1:32 AM on Thursday, October 16, 2014 from Satish Dhawan Space Centre SHAR, Sriharikota at the PSLV-C26 XL launcher .

The launch took place after a 67-hour countdown which began at 6.32 a.m. on October 13. The launcher placed the satellite precisely into an orbit with an perigee of 282 km and an apogee of 20,670 km.

The launch window of the mission extended from 0132 hrs IST to 0147 hrs IST. The 1,425-kg satellite is to be positioned in a Geostationary orbit at 83-deg E longitude.

IRNSS-1C
The satellite was earlier scheduled to be launched on October 10, 2014. However, on October 6, 2014 ISRO announced that the 67-hr countdown of the launch, which was to start at 7 AM on October 8, 2014 had been postponed by a week. 

"Due to an observation in the telemetry system, the launch has been postponed for a week," ISRO announced on its FB page.

IRNSS-1D


The satellite was successfully launched onboard PSLV-C27, the XL variant of the launcher. The launch took place from the Second Launch Pad (SLP) of Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota. 

The launch of the satellite was initially scheduled for March 9, 2015 but was postponed after a routine check following the mating of the satellite with the launch vehicle on March 4 found a telemetry transmitter malfunctioning. ISRO deferred the flight and took out the satellite to put a new transmitter.

Following launch, IRNSS-1D was placed into a sub Geosynchronous Transfer Orbit (sub GTO) with a 284 km perigee (nearest point to Earth) and 20,650 km apogee (farthest point to Earth) with an inclination of 19.2 deg with respect to the equatorial plane.

After injection into this preliminary orbit, the two solar panels of IRNSS-1D were automatically deployed in quick succession and the Master Control Facility (MCF) at Hassan took control of the satellite. 

MCF then commanded four orbit raising maneuver - one at perigee and three at apogee -  using the Liquid Apogee Motor (LAM) of the satellite.  

First Orbit Raising Maneuver

The first orbit raising operation of IRNSS-1D was successfully completed by firing the Apogee Motor at 17 28 hrs IST, on March 29, 2015. The orbital parameters achieved were: Perigee Altitude: 314 km, Apogee Altitude: 35653 km, Orbit period: 10hr 30min.

Second Orbit Raising Maneuver

The second orbit raising operation was successfully completed by firing the Apogee Motor for 28 min 23 sec at 09 07 hrs IST, on March 30, 2015. The orbital parameters achieved were: Perigee Altitude: 8459 km, Apogee Altitude: 35565 km, Orbit period: 13 hr 13 min.

Third Orbit Raising Maneuver

The third orbit raising operation of IRNSS-1D is successfully completed by firing the Apogee Motor for 22 minutes, at 11 37 hrs IST, on March 31, 2015. The orbital parameters are: Perigee Altitude: 23881 km, Apogee Altitude: 35569 km. Orbit period: 18hr 57min.

Fourth Orbit Raising Maneuver

The fourth and final orbit raising operation of IRNSS-1D is successfully completed by firing the Apogee Motor for 493 seconds, at 06 42 hrs IST, on on April 01, 2015. The orbital parameters achieved are: Perigee Altitude: 35556 km, Apogee Altitude: 35603 km, Inclination: 30.463 degree and Orbit period: 23hr 45min

Final Slot

GPS World reported on April 9, 2015 that the satellite had reached its final slot 

Based on data supplied by the U.S. Joint Space Operations Center, IRNSS-1D is in an inclined geosynchronous orbit with an inclination of 30.5 degrees and a nodal longitude of 111.7 degrees east, within the allowed limits of the assigned longitude of 111.5 degrees east.

IRNSS-1E

The fourth and final orbit raising operation was successfully carried out for 447 sec (~7.45 min) from 22:49 hrs IST on Jan 23, 2016.

The third orbit raising operation was successfully carried out by firing the LAM engine for 1507 sec (~25 min) from 03:19 hrs IST on Jan 23, 2016.

The perigee raising maneuver was successfully carried out for 1515.36 sec (25.5 min) from 01:29 hrs IST on January 22, 2016.

The apogee raising maneuver of the satellite was carried out for 1197 sec (20 min )) from 09:41 hrs IST on January 21.1515.36 sec (25.5 min) from 01:29 hrs IST on January 22, 2016.

The 1425 kg IRNSS-1E satellite was successfully launched from the Second Launch Pad using PSLV-C31 (XL variant) on January 20, 2016) from Satish Dhawan Space Centre SHAR, Sriharikota. 

The launch marked the thirty second consecutively successful mission of PSLV and the eleventh in its 'XL' configuration.

Following launch subsequent important flight events - strap-on ignitions and separations, first stage separation, second stage ignition, heat-shield separation, second stage separation, third stage ignition and separation, fourth stage ignition and satellite injection, took place as planned. 

After a flight of about 18 minutes 43 seconds, IRNSS-1E Satellite was injected to an elliptical orbit of         282.4 km X 20,655.3 km inclined at an angle of 19.21 degree to the equator (very close to the intended orbit) and successfully separated from the PSLV fourth stage. 

After injection, the solar panels of IRNSS-1E were deployed automatically. ISRO's Master Control Facility (at Hassan, Karnataka) took over the control of the satellite. Four orbit maneuvres are planned to position the satellite in the Geosynchronous Orbit at 111.75 deg East longitude with 28.1 deg inclination.

IRNSS-1F

The satellite was successfully launched and inserted into its orbit on March 11, 2016 using PLSV-C32 launcher.

The satellite had a lift-off mass of 1,425 kg and is powered by two solar panels generating 1660 W and one Lithium-ion battery of 90 Ampere-hour capacity.

The satellite carries navigation and ranging payloads. The navigation payload will transmit navigation service signals and will operate in the L5 band and S band. The ranging payload consists of a C-band transponder that facilitates accurate determination of the range of the satellites.

The apogee was raised with a 1192-sec firing of the LAM at 16:16 hrs on March 11, 2016. Orbital parameters following the maneuver were  

35828 km x 318.5 km
Inclination is 17.86 deg.
Orbital period is 10hr 34min.

Second LAM firing for 1918.5 sec at  07:57:54 hr IST on March 12, 2016 was successful.

The orbital parameters following the LAM firing were 

35737 km x 9831 km
Inclination is 9.75deg
Orbital period now is 13 hr 46 min

Third LAM firing for 1561 sec at 11:32 hr IST on March 13, 2016 was successful.

The orbital parameters following the LAM firing were 

35749 km x 33355 km
Inclination is 5.271deg
Orbital period now is 22 hr 53 min

Fourth LAM firing for 78.8 sec at 11:42:44 hr (IST) on March 14, 2016 was successful.

The orbital parameters following the LAM firing were

35749 km x 35605 km
Inclination is 5.097deg
Orbital period now is 23 hr 50 min 32 sec

IRNSS-1G


May 03, 2016: Orbit Determination results from fourth LAM firing are : apogee X perigee height has changed to 35,811-km, 35,211-km, Inclination is 5.1 deg. Orbital period now is 23-hr 42-min 04-sec

May 03, 2016: The fourth and the final LAM firing of IRNSS-1G for 231-sec was successfully completed starting from 01:27 hr IST

May 02, 2016 : Orbit Determination results from the third LAM firing are: apogee X perigee height was changed to 35,813-km, 29,050-km, Inclination is 5.72deg. Orbital period now is 21hr 08m 09sec

May 01, 2016 : Third LAM firing of IRNSS-1G, for 1609sec has been successfully completed on 01.05.2016 starting from 06:59:07 hr IST.

May 01, 2016 : Orbit Determination results from second LAM firing are:apogee X perigee height was changed to 35803km,7750km,Inclination is 10.77deg.Orbital period now is 13h 03m 35sec 

Apr 30, 2016 : PSLV-C33 / IRNSS-1G Update : Second LAM firing of IRNSS-1G, at apogee for 1581 sec has been successfully completed on April 30, 2016 starting from 04:52:17 hrs IST.

The 1425-kg IRNSS-1G  was launched on April 28, 2016 on PSLV-C33, the thirty fifth flight of ISRO's Polar Satellite Launch Vehicle from Satish Dhawan Space Centre SHAR, Sriharikota. The launched marked the 34-th consecutively successful mission of PSLV and the 13-th in its 'XL' configuration.

Following the launch, Prime Minister of India, Mr. Narendra Modi, dedicated IRNSS to the nation as ‘NavIC’ (Navigation Indian Constellation).  

After PSLV-C33 lift-off at 1250 hrs (12:50 pm) IST from the First Launch Pad with the ignition of the first stage, the subsequent important flight events, namely, strap-on ignitions and separations, first stage separation, second stage ignition, heat-shield separation, second stage separation, third stage ignition and separation, fourth stage ignition and satellite injection, took place as planned. After a flight of 19 minutes 42 seconds, IRNSS-1G was injected into an elliptical orbit of 283 km X 20,718 km inclined at an angle of 17.867 degree to the equator (very close to the intended orbit) following which the satellite successfully separated from the PSLV fourth stage.

After separation, the solar panels of IRNSS-1G were deployed automatically. ISRO's Master Control Facility (MCF) at Hassan, Karnataka took over the control of the satellite. Four orbital maneuvers are planned from MCF to position the satellite in the Geostationary Orbit at 129.5 deg East longitude.

Constellation Status

India plans to launch a new navigation satellite in the second half of this year to replace IRNSS-1A. 

In end January, ISRO Chairman Kiran Kumar told the press that one of the three crucial rubidium timekeepers on IRNSS-1A spacecraft failed six months ago. The other two followed subsequently. The satellite was otherwise all right and performing its core function of providing accurate position, navigation and time. However, without its clocks, the IRNSS-1A “will give a coarse value. It will not be used for computation. Messages from it will still be used.”

ISRO, he said, was trying to revive the clocks on 1A and readying one of the two back-up navigation satellites to replace it in space in the second half of this year.

IRNSS Constellation Augmentation

ISRO plans to initiate work to augment the IRNSS system with 4 additional satellites during the 12th Plan (2012-17). The satellites will serve as in orbit back-ups.

“We are building four more satellites that will act as back up to the seven satellites of the IRNSS. Each individual satellite of this system can easily last for 7-15 years, but we are not taking any chances and building a back-up,” Tapan Misra, director of SAC, told the Indian Express in January 2016.



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