Japanese Halley exploration project

Planet-A, Japan's first interplanetary mission, will be launched in August 1985 by an improved version of the M-3S satellite launch vehicle, the M-3SII. Planet-A will fly past the comet near its descending node at the beginning of March 1986. The spacecraft is cylindrical, with a weight of about 140 kg, a diameter of 1.4 m, and a height of 0.7 m. A high-gain mechanically despun off-set parabolic antenna is mounted on the top, and a medium-gain antenna is attached to the bottom. The spacecraft is spin-stabilized, with its spin axis perpendicular to the ecliptic plane during the entire mission. A momentum wheel is installed to maintain attitude stability during the imaging phase, which will last many days. The two scientific instruments to be carried are a vacuum ultraviolet TV camera and a solar wind particle analyzer.