Read our full story.
Check out launch photos showing GSLV's picturesque liftoff.
Separation of the GSAT 14 spacecraft is expected momentarily.
The third stage engine is designed to produce 75 kilonewtons, or 16,860 pounds, of thrust and burns more than 28,000 pounds of liquid hydrogen and liquid oxygen during its 12-minute burn.
The rocket's second stage engine will shut down at T+plus 4 minutes, 49 seconds. Just a few seconds later, the third stage will separate and ignite to continue propelling GSAT 14 toward orbit.
Ignition of the launcher's S139 solid-fueled core stage occurs as the countdown clock hits zero, followed immediately by liftoff.
The countdown is under the control of a computerized automatic sequence.
The payload for this launch is GSAT 14, a 4,369-pound Indian communications satellite. GSAT 14 will extend India's Ku-band and C-band communications capacity with 12 transponders, along with a pair of Ka-band beacons for frequency attenuation studies.
After three orbit-raising maneuvers with its on-board engine and deployment of its solar panels and two antennas, the satellite will be positioned in geostationary orbit at 74 degrees east longitude for a 12-year mission.
GSAT 14 will be positioned near other Indian satellites, such as INSAT 3C, INSAT 4CR and Kalpana 1, according to ISRO. The spacecraft also carries several technological experiments, including a fiber optic gyroscope, an active pixel sun sensor and new types of thermal coatings.
The S139 core motor and Vikas engines on the boosters will jettison and two-and-a-half minutes after liftoff, yielding to the GSLV's second stage Vikas engine for a more than two-minute burn, during which the rocket's 11.1-foot-diameter metallic payload fairing will fall away.
The third stage will ignite for a 12-minute burn before releasing the GSAT 14 spacecraft in an orbit with a low point of about 180 kilometers, or 111 miles, a high point of 35,975 kilometers, or 22,353 miles, and an inclination of 19.3 degrees. See more details on the GSLV's flight sequence in our launch timeline.
The leak of toxic hydrazine fuel was blamed on cracks in the second stage fuel tank, which was made of an aluminum-zinc alloy known as Afnor 7020. The Indian launch team rolled the GSLV back to the vehicle assembly building at the Satish Dhawan Space Center to be taken apart and refurbished.
Engineers replaced the first and second stages of the GSLV after the Aug. 19 launch attempt. The new second stage has a fuel tank made of a different aluminum-copper alloy named AA2219.
ISRO also changed out electronic components inside the GSLV's four liquid-fueled strap-on boosters damaged by the fuel leak and subsequent cleaning with water. The third stage and GSAT 14 spacecraft were inspected and tested during the fall and found to be ready for launch.
Six of the GSLV's seven missions to date have flown with Russian-built hydrogen-fueled third stage engines, but India attempting to demonstrate its own cryogenic third stage to give the nation a launcher with all-Indian components.
The first GSLV launch occurred on April 20, 2001, with the GSAT 1 satellite. The mission was a partial success, delivering its payload to a slightly lower-than-planned orbit due to the premature shutdown of the rocket's Russian third stage.
Two subsequent launches of the GSLV in May 2003 and September 2004 proved successful before the GSLV was hamstrung by a series of mishaps.
A launch in July 2006 ended when the GSLV veered out of control and disintegrated about 55 seconds after liftoff due to a malfunctioning propellant regulator inside one of four liquid-fueled strap-on boosters, which allowed excess propellant to flow into the Vikas engine, driving up temperatures and pressures inside the engine.
The next GSLV mission in September 2007 placed the INSAT 4CR communications satellite in orbit, but the rocket's third stage again underperformed, deploying the spacecraft in the wrong orbit.
India followed with another GSLV launch in April 2010, the first time the launcher had ever used an Indian-built third stage. The rocket fell short of orbit due to a fuel pump anomaly on the indigenous cryogenic upper stage.
Another GSLV launch in December 2010, which reverted back to using the Russian third stage, disintegrated in a fireball less than a minute after liftoff, when cables between the launcher's computer and strap-on boosters inadvertently disconnected in flight, causing the GSLV to lose control.
ISRO considers four of the seven GSLV missions to date to be failures.
The third stage is the only part of the GSLV not already loaded with propellant. Its liquid hydrogen tank will be filled next. The third stage tanks will contain more than 28,000 pounds of propellant at the time of launch.
After the 161-foot-tall rocket rolled to the launch pad Dec. 28, engineers completed final preparations on the launch vehicle and commenced the 29-hour countdown at 0548 GMT (12:48 a.m. EST) Saturday.
Later Saturday, the GSLV's second stage and four L40H strap-on boosters were loaded with hydrazine and nitrogen tetroxide propellants.
The second stage and four strap-on boosters are powered by hydrazine-fueled Vikas engines, each producing about 150,000 pounds of thrust.
The GSLV's first stage is powered by a solid-fueled motor generating more than a million pounds of thrust. Its propellant was packed inside the motor casing before the rocket was assembled.
Fueling of the third stage comes last in the sequence because its cryogenic propellant is stored at frigid temperatures, and the liquid oxygen and liquid hydrogen boils off when exposed to ambient temperatures.
Liftoff is set for 1048 GMT (5:48 a.m. EST) from the Satish Dhawan Space Center on India's east coast.
The rocket sprung a fuel leak during a countdown Aug. 19, forcing Indian officials to scrap a long-delayed test launch of the GSLV with an Indian-built cryogenic upper stage, which engineers see as a pathway to building larger launchers with all-Indian technology.
The launch team aborted the countdown about an hour and 15 minutes before liftoff in August, then ground crews rolled the GSLV back inside its assembly building to be taken apart, inspected and refurbished.
We'll have live updates during the final countdown and launch.
Read our full story.
The 29-hour countdown began at 0620 GMT (2:20 a.m. EDT) Sunday, followed by fueling of the GSLV's second stage and four liquid-fueled L40 strap-on boosters with hydrazine and nitrogen tetroxide propellants.
The second stage and four strap-on boosters are powered by hydrazine-fueled Vikas engines, each producing about 150,000 pounds of thrust.
The GSLV's first stage is powered by a solid-fueled motor generating more than a million pounds of thrust. Its propellant was packed inside the motor casing before the rocket was assembled.
Fueling of the third stage comes last in the sequence because its cryogenic propellant is stored at frigid temperatures, and the liquid oxygen and liquid hydrogen boils off when exposed to ambient temperatures.
The Geosynchronous Satellite Launch Vehicle, or GSLV, will take off at 1120 GMT (7:20 a.m. EDT) from the Satish Dhawan Space Center on India's east coast. It will be 4:50 p.m. local time at the launch base, which is situated on Sriharikota Island on the east coast of India.
The 161-foot-tall rocket is carrying the GSAT 14 communications satellite, a 4,369-pound spacecraft to extend Ku-band and C-band services over India.
But much of the attention on Monday's launch will focus on the GSLV, the centerpiece of India's ambition to become a fully independent space power. Without the GSLV, India must launch its heaviest satellites on foreign rockets such as the European Ariane 5.
India grounded the GSLV following a pair of launch failures in 2010 - first a premature shutdown of the GSLV's Indian cryogenic upper stage in April, then an explosive mishap shortly after liftoff on another mission in December.
Engineers are confident they have fixed the problems.
"We are sure, with the adjustments we have mad eand the meticulous reviews we have gone through, this stage should perform precisely, and we'll have a very successful GSLV mission," said S. Ramakrishnan, director of India's Vikram Sarabhai Space Center. "I'm sure with the kind of teamwork we have, and the kind of people we have with us, we will be able to definitely overcome any issue or problem, and GSLV will also be operational one day as PSLV."
India's Polar Satellite Launch Vehicle, or PSLV, has racked up a string of successful launches dating back to 1994. But the PSLV's capacity is limited to satellites bound for low orbits or smaller spacecraft heading for higher altitudes.
The GSLV is designed to loft more massive satellites, including payloads for India's growing fleet of communications spacecraft.
Monday's flight will feature an Indian-built hydrogen-fueled third stage built to replace a Russian-provided engine used on the GSLV Mk.1 model, the rocket's early variant.
International missile and defense technology agreements stipulated Russia could only provide readymade third stages for the GSLV, forcing India to start an in-house program to design and build its own upper stage.
The Indian upper stage failed during its first test flight in April 2010, when the engine's fuel turbopump failed about one second after igniting, dooming the mission. Another GSLV launch with a Russian third stage disintegrated in a fireball less than a minute after liftoff in December 2010, a failure caused by the "untimely and inadvertent snapping of connectors" between the GSLV's computer and the control system on its four liquid-fueled strap-on boosters.
Since 2010, Indian engineers made a number of improvements to the GSLV, including a redesign of the third stage engine's fuel turbopump to account for the expansion and contraction of bearings and casings as super-cold liquid propellant flows through the engine.
Officials also modified the third stage's ignition sequence to ensure the "smooth, successful and sustained ignition" for the main engine, steering engine and gas generator system.
India also made improvements to the third stage engine's protective shroud and a wire tunnel in the third stage. Engineers revised their understanding of the aerodynamic characteristics of the GSLV and added an on-board camera system to better monitor the rocket's performance in flight.
Before approving the improved GSLV for flight, India completed two acceptance tests of the GSLV's third stage fuel turbopump to ensure it will not succumb to the same problem that plagued the April 2010 launch. Engineers also put the third stage engine into a vacuum chamber to simulate ignition at high altitude.
The third stage engine, designed to produce nearly 16,860 pounds of thrust, will take over 4 minutes, 54 seconds after liftoff.
The third stage engine will fire for 12 minutes during Monday's launch to inject the GSAT 14 satellite into a geosynchronous transfer orbit with a low point of 111 miles, a high point of 22,353 miles and an inclination of 19.3 degrees.
GSAT 14's own propulsion system will raise the low point, or perigee, of its orbit to an altitude of 22,300 miles and align its orbit over the equator to begin a 12-year mission.