JAXA, the Japanese space agency, confirmed that its space probe Akatsuki has successfully accomplished the maneuvers to allow it to enter the orbit of the planet Venus. These maneuvers took place exactly five years after the failure of the first attempt. The orbit is significantly different from the one programmed for the mission and JAXA engineers are assessing it to schedule some additional maneuvers. However, there’s optimism about the possibility of carrying out the scientific mission Akatsuki was built for.
The Akatsuki space probe, also known as Venus Climate Orbiter (VCO) or Planet-C, was launched on a H-IIA 202 rocket on May 20, 2010. This is in many ways a specialized weather satellite for the study of the planet Venus’ weather. On December 7, 2010 the maneuver with a 12-minute burn of the main engine was supposed to be carried out, with the goal of braking Akatsuki enough to allow it to enter Venus’ orbit.
According to a subsequent reconstruction carried out thanks to the telemetric data, Akatsuki’s engine worked for less than 3 minutes then it got damaged after reaching too high temperatures, probably due to an excess of oxidant in its combustion chamber.
As a result, the Akatsuki space probe wasn’t captured by the planet Venus’ gravity but remained in orbit around the Sun. After the incident, JAXA has verified that the instruments on board were still working and at that point started developing an alternative plan that required the use of other Akatsuki’s engines.
A test of the orbital maneuvering engines found out that they were affected by the damage and could deliver only 10% of the expected thrust. Consequently, it’s been necessary to program the use of the attitude control thrusters, an independent system still working, for new maneuvers. These thrusters use hydrazine and don’t need an oxidant, which consequently was dumped into space in 2011.
Because of the limitations of the attitude control thrusters and the position of the Akatsuki space probe, it took five years before they could try a new orbit insertion maneuver. In fact, those thrusters have been used beyond their safety limits but there was no alternative.
The orbit around Venus reached by Akatsuki is quite different from the one originally planned: it’s much more elliptical and after the adjustments if all goes well it will take nine days for it to perform a complete orbit. However, it will still take a while to assess the exact orbit reached and the possible adjustments because the thrusters were used in a manner very different from the one they were built for.
It will also be necessary to verify the proper operation of the Akatsuki space probe’s instruments because they stayed in space for a time already longer than expected for the mission and they were exposed to solar radiation more than expected. During the unexpected journey, it was kept in hibernation to try to preserve it and only now it’s possible to assess their state. If Akatsuki can fulfill its mission, it will still be a victory for JAXA because space is unforgiving and saving a mission from what looked like a disaster would be the great achievement of the ingenuity of the JAXA’s staff.
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