Parker Solar Probe by the Helios 2 spacecraft. The "Parker Solar Probe" concept originates from a predecessor "Solar Orbiter" project conceived in the 1990s. Similar in design and objectives, the "Solar Probe" mission served as one of the centerpieces of the eponymous Outer Planet/Solar Probe (OPSP) program formulated by NASA. The first three missions of the program were planned to be: the "Solar Orbiter", the Pluto and Kuiper belt reconnaissance mission "Pluto Kuiper Express", and the "Europa Orbiter" astrobiology mission focused on Europa. The original "Solar Probe" design used a gravity assist from Jupiter to enter a polar orbit which dropped almost directly
The Tenth Planet of malevolent cyborgs that became a recurring adversary in later "Doctor Who" stories. The "tenth planet" in the title makes reference to a fictional lost planet in Earth's Solar System; at the time of production, the Solar System was generally held to consist of nine planets, prior to the redesignation of Pluto as a minor planet. "The Tenth Planet" is an incomplete "Doctor Who" serial – one of many serials that were affected by the BBC's policy of wiping archived programmes in the 1960s and 70s. Only three of the four episodes are currently held in the BBC archives; the