Japan's third HTV cargo freighter is on track to plunge back into Earth's atmosphere as scheduled Friday after an unknown problem on Wednesday triggered an expedited departure from the International Space Station, according to a NASA spokesperson.

HTV is released from the station's robot arm. Credit: NASA TV

The barrel-shaped resupply craft was released from the space station's robotic arm at 11:50 a.m. EDT (1550 GMT). A few minutes later, the H-2 Transfer Vehicle pulsed its thrusters and quickly flew away from the complex.

According to Kelly Humphries, a spokesperson at NASA's Johnson Space Center in Houston, the HTV executed an abort maneuver.

Like other spacecraft visiting the space station, the HTV is designed to autonomously command an abort in the event of a major problem to avoid colliding with the 450-ton orbiting outpost.

"The abort system did what it was supposed to do and took the HTV safely away from the station, and it's on track to re-enter as scheduled," Humphries told Spaceflight Now.

A daily space station status report posted on a NASA website said the abort was triggered by a drop-out of In/Out Computer 2. The maneuver placed the HTV well away from the space station, according to the status report.

Japan Aerospace Exploration Agency flight controllers in Tsukuba, Japan, restored full telemetry from the HTV through another computer, and the root cause of the anomaly is under investigation, NASA officials wrote in the report.

The Japanese cargo vehicle is scheduled to conduct a final de-orbit burn at 12:51 a.m. EDT (0451 GMT) Friday, and the spacecraft will drop back into the atmosphere at 1:24 a.m. EDT (0524 GMT).

The HTV is designed to dispose of trash from the space station during re-entry, when the craft and its cargo will break up and fall into a remote part of the Pacific Ocean.

Two data recorders, one provided by JAXA and another by the Aerospace Corp., will log data on the re-entry conditions, such as position, acceleration, temperature and imagery.

Engineers will incorporate the data in the design and operations of future spacecraft, yielding more accurate re-entry predictions, casualty expectations, and potentially leading to a "black box" for spacecraft similar to devices on airliners.

The HTV is wrapping up a 47-day stay at the space station, in which the craft delivered food and clothing, an aquatic habitat experiment, an Earth observation camera, and other supplies.

The cargo craft also delivered five small CubeSat satellites and a Japanese-built deployer apparatus. The CubeSats will be released outside the space station beginning this fall.

The spacecraft, which is dubbed Kounotori 3, carried two research payloads mounted outside the space station.

A NASA-led communications experiment launched aboard the HTV could lead to more capable and less complex spacecraft radios, and a Japanese experiment package includes a set of investigations probing plasma and lightning in Earth's atmosphere, collecting data on inflatable space structures and robotics systems, and testing commercial off-the-shelf HDTV video equipment in the harsh environment of space.

The Kounotori 3 cargo freighter is the third of at least seven HTVs planned by JAXA to resupply the space station. Japan provides the HTV cargo service to pay for its share of the station's operating costs.

NASA and JAXA expect to negotiate for further HTV missions to cover the lab's supply needs and Japan's cost obligations through 2020, the currently planned end-of-life for the space station.