Moscow A US-Russian crew remained on course to dock with the International Space Station today, 48 hours after embarking on a new era in space exploration that could see man set foot on Mars. US astronaut William Shepherd and Russian cosmonauts Sergei Krikalyov and Yury Gidzenko spent yesterday preparing for an automatic docking by their Soyuz craft with the ISS. The crew are scheduled to link up with the ISS's Zvezda module at 9.24 a.m. Irish time today for a four-month mission.