India’s PSLV rocket successfully launches IRNSS-1F navigation satellite

Tomasz Nowakowski

PSLV-C32 liftoff with IRNSS-1F. (Click to enlarge.) Photo Credit: ISRO

India’s Polar Satellite Launch Vehicle (PSLV) has successfully launched the IRNSS-1F navigation satellite on Thursday, March 10, increasing the fleet of the Indian Regional Navigation Satellite System (IRNSS) to six. Liftoff took place at 16:01 IST (5:31 a.m. EST; 10:31 GMT) from the Second Launch Pad at the Satish Dhawan Space Centre in Sriharikota. The launch was delayed by one minute for collision avoidance according to space debris studies.

The rocket commenced its short vertical ascent as planned, igniting its four boosters. Then the launch vehicle started heading southeast across the Indian Ocean, and about 25 seconds after liftoff, the remaining two boosters began firing at an altitude of 1.6 miles (2.6 kilometers). The four ground-lit boosters were jettisoned one minute and ten seconds into the flight, whereas the air-lit duo separated 22 seconds later.

Continuing the flight for the next 17 seconds, the rocket’s first stage detached from the launch vehicle at an altitude of about 34.8 miles (56 kilometers). Then the second stage ignited, taking control of the mission. It flew for nearly one and a half minutes when the payload fairing separated, unveiling the IRNSS-1F spacecraft. The separation of the second stage took place approximately four minutes and 21 seconds after launch.

The launch vehicle was at an altitude of 83.8 miles (134.8 kilometers) when the ignition of the third stage occurred. This stage accelerated the stack from 12,000 mph to nearly 17,300 mph (19,310 km/h to 27,840 km/h) during this phase of the mission which lasted some six minutes and 24 seconds. Then the third stage separated, deploying the spacecraft mated with the fourth stage.

Ten seconds later, the fourth stage fired its two engines, beginning the last phase of the flight. The stack flew for about nine minutes until the separation of the IRNSS-1F satellite approximately 20 minutes and 11 seconds after launch, at an altitude of 304 miles (489 kilometers). Shortly after separation, the spacecraft deployed its two solar arrays and established communications with ground stations.

Finally, the satellite will be delivered to a geostationary orbit (GTO), inclined 32.5 degrees. It is expected to be operational for up to 12 years.

The Indian Space Research Organisation (ISRO) started preparations for this mission last year with the integration of the launch vehicle. In Sept. 2015, after a series of successful tests, the IRNSS-1F payload was delivered to the ISRO Satellite Centre for integration with the spacecraft. The PSLV rocket was assembled in January and February. After the assembly, a set of checkout operations began to check all subsystems and test the communication lines.

On Monday, March 7, the Launch Authorisation Board gave the green light for the mission, clearing it for a 54-and-a-half-hour countdown. Next day, the rocket was rolled out to the launch pad. The countdown started a busy sequence of operations to configure the PSLV booster for the mission.

IRNSS-1F is the sixth out of seven satellites in the Indian Regional Navigational Satellite System (IRNSS). It has a mass of some 1.425 metric tons and its dimensions are 5.18 × 4.92 × 4.92 feet (1.58 × 1.5 × 1.5 meters). It can generate up to 1,660 W of power.

The satellite is based on the I-1K (I-1000) bus. It features two solar panels and one lithium-ion battery. The spacecraft is fitted with a liquid apogee motor, dual helix antenna, corner cube retroreflector, and star sensors. It will carry navigation and ranging payloads. The navigation payload will transmit directional service signals to users. Navigation data will be acquired by Sun and star sensors as well as an inertial measurement unit. The ranging payload will consist of a C-band transponder which facilitates accurate determination of the range of the satellite. The design of the payloads makes the IRNSS system interoperable and compatible with both the U.S. GPS and European Galileo system.

The configuration of IRNSS-1F is similar to its predecessors: IRNSS-1A, 1B, 1C, 1D, and 1E. The first IRNSS satellite (IRNSS-1A) was launched by a PSLV rocket on July 1, 2013, from the Satish Dhawan Space Centre. The most recent satellite in the series, IRNSS-1E, was sent into orbit on Jan. 20, 2016, also by a PSLV booster. The next IRNSS spacecraft (IRNSS-1G) is expected to be launched in April of this year.

IRNSS-1F should provide accurate position information services to users in India as well as the surrounding region. It will deliver Standard Positioning Service (SPS), responsible for navigation parameter generation and transmission, satellite control, ranging, and integrity monitoring, as well as timekeeping services.

Approved in 2006, IRNSS is a satellite-based positioning system for critical national applications. Its main objective is to provide reliable position, navigation, and timing services over India and its neighborhood. It is expected to grant accuracy of better than 66 feet (20 meters) in the primary service area.

The system will consist of some seven satellites. Once complete, the constellation should provide their services in a fixed orbit above the Indian region. The IRNSS fleet is expected to be complete by April 2016. While four satellites would be sufficient to start operations of the IRNSS system, seven would make it more accurate and efficient. All the satellites of the constellation are configured identically.

The four-stage PSLV booster is India’s most reliable launch vehicle. The rocket has been used to delivered more than 40 satellites into space for some 19 countries. PSLV is capable of lofting up to 3.25 metric tons to low-Earth orbit and about 1.42 metric tons to a geosynchronous transfer orbit (GTO).

The rocket uses an Earth-storable, liquid-fueled rocket engine for its second stage, known as the Vikas engine; it was developed by the Liquid Propulsion Systems Centre. The third stage of the PSLV is powered by a solid rocket motor that provides the upper stage’s high thrust after the atmospheric phase of the mission. The fourth stage is composed of two Earth-storable liquid-fueled engines.

The 144 ft. (44 meters) tall XL version of the PSLV, which was used for Thursday’s mission, is the upgraded variant of the rocket in its standard configuration. Its thrust is increased by more powerful, stretched strap-on boosters. The vehicle has a mass of 320 metric tons at liftoff and uses the larger strap-on motors (PSOM-XL) that provide the capability of hoisting heavier payloads into orbit. PSOM-XL uses the larger, 1-meter diameter, 44 ft. (13.5 m) length motors. This version of the rocket carries 12 metric tons of solid propellants instead of the nine metric tons that were used on an earlier configuration of the PSLV.

The PSLV rocket in its XL configuration was launched for the first time on Oct. 22, 2008, when it sent India’s Chandrayaan-1 lunar probe toward the Moon.

Thursday’s mission was India’s second launch this year. The country’s next flight is currently scheduled to take place in April when a PSLV-XL rocket will send the IRNSS-1G navigation satellite into orbit. The exact date of that launch has yet to be announced.

PSLV-C32 liftoff with IRNSS-1F. Photo Credit: ISRO