Tuesday, March 8, 2016

ISRO All Set to Launch Its Newest Navigation Satellite

Fully integrated PSLV-C32 with IRNSS-1F being moved out of vehicle assembly building to the second launch pad. Photo Credit: ISRO

The Indian Space Research Organisation (ISRO) is ready to expand its homegrown satellite navigation system by sending the IRNSS-1F spacecraft into space on Thursday, Mar. 10. The satellite is expected to liftoff atop India’s Polar Satellite Launch Vehicle (PSLV) at 5:30 a.m. EST (10:30 GMT) from the Second Launch Pad at the Satish Dhawan Space Centre in Sriharikota.

The mission, designated PSLV-C32, is the 34th flight of the PSLV booster. It will last approximately 20 minutes and 11 seconds, ending in spacecraft separation at an altitude of 304 miles (489 kilometers). Finally, the satellite will be delivered into a geostationary transfer orbit (GTO), inclined 17.86 degrees. It is expected to be operational for up to 12 years.

Preparations for this mission started last year with the integration of the launch vehicle. In September 2015, after series of successful tests, the IRNSS-1F payload was delivered to the ISRO Satellite Centre for integration with the spacecraft. On Monday, Mar. 7, the Launch Authorisation Board gave the green light for the mission, clearing it for a 54-and-a-half-hour countdown.

IRNSS-1F is the sixth out of seven satellites in the Indian Regional Navigational Satellite System (IRNSS). It has a mass of 1.425 tons and its dimensions are: 5.18 x 4.92 x 4.92 feet (1.58 x 1.5 x 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 liquid apogee motor, dual helix antenna, corner cube retro reflector and star sensors. It will carry navigation and ranging payloads. The navigation payload will transmit navigation service signals to the users. Navigation data will be acquired by sun and star sensors as well as an inertial measurement unit. The ranging payload will consist a C-band transponder which facilitates accurate determination of the range of the satellite. The design of the payloads makes the IRNSS system inter-operable and compatible with American 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 orbited on Jan. 20, 2016, also by a PSLV booster. Next IRNSS spacecraft (IRNSS-1G) is expected to be launched in April 2016.

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.

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 provide a position 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 in April 2016. While four satellites would be sufficient to start operations of the IRNSS system, the remaining three would make it more accurate and efficient. All the satellites of the constellation are configured identically.

IRNSS will also have a network of 21 ranging stations geographically distributed primarily across India. They provide data for the orbit determination of IRNSS satellites and monitoring of the navigation signals.

The four-stage PSLV booster is India’s most reliable launch vehicle. It has been in service for more than twenty years and has been used to launch various satellites for some of the country’s most historic missions, such as Chandrayaan-1, the Mars Orbiter Mission (MOM), the Space Capsule Recovery Experiment, as well as the IRNSS system.

The rocket has been used to delivered more than 40 satellites to space for some 19 countries. PSLV is capable of lofting up to 3.25 metric tons to LEO 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, that will be used in Thursday’s mission, is the upgraded version of the rocket in its standard configuration. It is boosted by more powerful, stretched strap-on boosters. The vehicle has a mass of 320 metric tons at liftoff and uses larger strap-on motors (PSOM-XL) that provide the capability of hoisting heavier payloads to 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 is 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 to orbit. The exact date is yet to be announced.

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