The rocket, which was commissioned by Japan’s Aerospace Exploration Agency (JAXA), took off from Japan’s Tanegashima Space Center at its scheduled instantaneous launch window of 12:05 PM EDT (1:05 AM JST) on Tuesday September 24 and arrived the International Space Station on Saturday, 28 September, succeeding during its second try after an initial attempt was scrubbed earlier this month.
Among the cargo carried onboard the HTV-8 rocket were three small satellites(AQT-D, NARSScube-1 and RWASat-1) for deployment from the International Space Station via the JEM Small Satellite Orbital Deployer (J-SSOD).
NARSScube-1 and RWASat-1 were built to the CubeSat standard, and are scheduled to be released from Kibo module’s airlock later this year.
NARSScube-1 is a single-unit CubeSat built by Egypt’s National Authority for Remote Sensing and Space Sciences (NARSS). The satellite equipped with a miniature of 200-meter resolution camera will record images of the Earth and transmit them back to its operators while providing them with experience and demonstrating technologies ahead of future missions. It follows on from the identical NARSScube-2, deployed from a US Cygnus spacecraft in August.
RWASAT-1, which is Rwanda’s first satellite, carries a communication payload that will collect and forward data to remote monitoring stations on the ground. It was developed at the University of Tokyo by 15 Rwandan Engineers. It also carries two cameras for Earth Observation and will serve as a technology demonstrator. According to Rwandan officials, the satellite will aid agricultural and environmental monitoring.
Information from the ground is transmitted to the satellite and later beamed back to control areas. In this way, sensors can be installed on the ground to monitor water resources in disaster-prone areas. According to Risk Atlas for Rwanda, a combined assault by disasters could cost the country a loss of USD 132m. Therefore, the launch of such CubeSats will be instrumental in providing substantial data to help the government in disaster management.
The launch scheduled for take-off in April was postponed due to adverse weather conditions and unavailability of a launch vehicle, but couldn’t meet the rescheduled launch date of11 September due to a fire outbreak in the launch pad during the prelaunch operations. The fire, which was notably close to the rocket, was due to an increase in the concentration of liquid oxygen used to cool the H2B rocket engine. The fire was later put out by water suppression systems. Liquid oxygen usually diffuses in the wind, but at that time, the wind was weak, thus increasing the concentration and making it easier to ignite, and might have been ignited by static electricity. The stack was rolled back off the pad for further checks before returning for the new launch attempt on Tuesday.
Three minutes and thirty-eight seconds into the flight, with the rocket at an altitude of about 119 kilometres (74 miles, 64 nautical miles), the payload fairing separated from the nose of the H-IIB. The structure, designed to protect Kounotori 8 during its ascent through the atmosphere and to ensure the rocket had a consistent aerodynamic profile, was no longer needed once the rocket reached space and was discarded to save weight.
H-IIB’s first stage continued to burn until Main Engine Cutoff (MECO), at the five-minute, 44-second mark in the mission. Having expended their supply, the two first-stage engines will shut down, with the spent stage separating eight seconds later. Eleven seconds after stage separation, H-IIB’s second stage ignited its LE-5B engine for an eight-minute, eleven-second burn.
The second-stage burn took Kounotori 8 directly into its initial orbit. JAXA has stated that this will be a 200 by 300-kilometre orbit. At fifteen minutes and five seconds mission elapsed time, HTV-8 detached from the upper stage of its carrier rocket. Eighty-four minutes after separation, the second stage restarted for a short disposal burn, firing for about 64 seconds to remove itself from orbit, ensuring a safe reentry.
After separation, Kounotori 8 underwent initial activation and checkout, before spending the first few days of its mission making a series of manoeuvres ahead of rendezvous with the International Space Station on the fourth day of the flight. Kounotori moved into position ten meters away from the station, where it was grappled by the CanadArm2 remote manipulator system (RMS) under the control of the outpost’s crew.
According to JAXA, the Kounotori 8 (HTV-8) mission, the penultimate flight of the HTV, will be replaced with the enhanced HTV-X in the early 2020s.
The launch, which was JAXA’s eighth mission to the station, coincided with the tenth anniversary of the first HTV launch on 11 September 2009. The Kounotori 1 HTV-1 spacecraft spent six weeks at the ISS before ending its mission with a planned destructive re-entry on November 1.
The HTV measured about 10 meters in length and 4.4 meters in diameter. It has a mass of up to 16,500 kilograms, including up to 4,100 kg of pressurised and 1,900 kg unpressurised cargo.