 L1, L2 and L5 bands which are processed by ground-based receivers like any other GPS signal. Augmentation messages are not generated onboard the satellite but on the ground through monitoring of GPS signal variability by an array of ground stations across Japan and surrounding regions which detect GPS clock errors and other factors like signal delay caused by changes in Earth’s ionosphere.
Correction data for these varying factors is uplinked to the QZS satellite which immediately re-transmits it to any enabled receiver in its footprint which can then apply the corrections to its navigation solution to yield a more accurate location, on average with one-meter accuracy.
QZSS delivers the L1-SAIF (Sub-meter class Augmentation with Integrity Function) that is compatible with the U.S. Wide Area Augmentation System, plus an L1-SAIF+ signal that allows receivers to acquire GPS position lock faster and provides space for messages for disaster relief. Additionally, an experimental signal designated L-EX is compatible with the European Galileo satellite constellation coming on line by the end of the decade.
QZS-4 will be an identical carbon copy of the second satellite and complete the three-satellite constellation that allows one of the satellites to be almost directly overhead (zenith) as seen from a user in Japan. The QZS-3 satellite will be slightly heavier, weighing in at 4,700 Kilograms, and aiming for a 15-year mission in the traditional Geostationary Orbit from where it can relay augmentation messages to a large area.
Called upon for the launch of QZS-2 was Japan’s trusted H-IIA rocket that debuted back in 2001 and has flown 33 times prior to Thursday’s mission, logging 32 successful missions.
Standing 53 meters tall, the launch vehicle consists of a stack of two four-meter diameter stages, each powered by a single liquid-fueled engine, plus two SRB-A3 Solid Rocket Boosters on the first stage to deliver the initial kick needed to send the satellite toward its high-energy orbit. At liftoff, H-IIA weighs 285 metric tons and the launcher can lift up to 4,100 Kilograms into a Geostationary Transfer Orbit.
H-IIA was moved to its launch pad at 9:30 UTC on Wednesday, marking the start of the lengthy launch countdown with final hands-on work at the launch pad to connect the launcher to ground systems ahead of detailed systems testing before propellant loading started at 16:31 UTC. Over the course of a three-hour sequence, H-IIA received 120 metric tons of -183°C Liquid Oxygen oxidizer and -253°C Liquid Hydrogen fuel for consumption by the rocket’s LE-7A and LE-5B engines.
Testing continued throughout the countdown and H-IIA was prepared for its automatic countdown sequence heading into the last hour of the day’s count. As the countdown switched to auto-mode at X-4.5 minutes, H-IIA pressurized its propellant tanks, transferred to internal power and switched to onboard control before activating thermal batteries and completing a final thrust vector control check on the boosters to clear the way for ignition.
H-IIA came to life at X-5.2 seconds when the LE-7A engine began its carefully controlled ignition sequence to roar to a thrust of 86 metric-ton-force before the twin boosters were fired up when clocks hit zero – catapulting the rocket off the ground with a thrust of 596 metric-ton-force. Climbing away from its sea-side launch pad, H-IIA maintained a vertical orientation for only a few seconds before its engine and boosters gimbaled to enter the pitch and roll program designed to align the vehicle with its south-easterly flight path across the Pacific Ocean.
The familiar scream unique to the H-II rocket series was heard across the Tanegashima Space Center as the vehicle accelerated downrange, passing Mach 1 and encountering Maximum Dynamic Pressure one minute into the flight, burning 1,600 Kilograms of propellant every second of powered flight.
The twin boosters, doing most of the work during the initial flight phase, helped accelerate the vehicle to a speed of 1.5 Kilometers per second as each delivered a thrust of 255 metric 