Japan’s Akatsuki Climate Orbiter muffed a critical engine firing Sept. 14, dimming the hopes of scientists that the error-prone satellite will be able to achieve an orbit around Venus conducive to observing the planet’s weather patterns.

“The results mean that we might have enough propulsion for Akatsuki to enter some kind of Venus orbit, but not the correct orbit, required. It’s possible that it might be able to do some science, but we don’t know yet,” Eijiro Namura, a spokesman for the Japan Aerospace Exploration Agency (JAXA), said Sept. 16.

The $300 million Akatsuki probe failed to enter Venus orbit in December 2010 due to the early shutoff of its orbit maneuver engine.

JAXA has been conducting a series of increasingly ambitious test fires in preparation for making a second attempt at orbital insertion in December 2015.

A critical firing of the engine Sept. 14 yielded disappointing results, with the engine developing only one-eighth of the required thrust, according to JAXA.