Mariner Mark II wasNASA's planned family of uncrewedspacecraft for the exploration of theouter Solar System that were to be developed and operated byJPL between 1980 and 2010.

After the"flagship" multibillion-dollar missions of the 1970s, in the 1980s NASA was looking for a new, more affordable direction for the 1990s and beyond. Two projects were conceived by NASA's Solar System Exploration Committee in 1983, thePlanetary Observer program, and Mariner Mark II.^[1]

The Observer program, starting with theMars Observer, was envisioned as a series of low-cost missions to theinner Solar System, based on commercial Earth satellites, while the Mariner Mark II was to be a series of large spacecraft for the exploration of theouter Solar System.^[2]

Mariner Mark II spacecraft were to use common design, hardware and software solutions, much of it derived from previous missions such asVoyager andGalileo as well as select new technologies, such as advanced gyroscopes, all with the aim of cutting costs. It was hoped that this new approach would reduce the mission costs to about $400 million each, about half the price of Galileo.^[3]

The first two missions of the project were to be a mission to Saturn and its moon Titan, theSaturn Orbiter/Titan Probe, or SOTP (laterCassini) and theComet Rendezvous Asteroid Flyby (CRAF), both of which were approved by Congress in 1990.^[4]

Other planned Mariner Mark II-based spacecraft were anESA led follow-on to CRAF, theComet Nucleus Sample Return or CNSR (laterRosetta, without the sample return);Pluto Fast Flyby, a flyby of Pluto (laterPluto Kuiper Express, eventually realized asNew Horizons); and aNeptune Orbiter with an atmospheric probe.^[5]

However, congressionally imposed reductions to FY 1992–93 funding requirements forced NASA to terminate the CRAF mission^[6] and to delay theCassini launch from April 1996 to October 1997.^[7] In order to save it, NASA was forced to significantly redesignCassini to reduce the total program cost, mass and power requirements.^[8]

NASA has had to replace theMariner Mark II program with the lower-costDiscovery Program.^[9]

• Mariner program
• Voyager program
• Pioneer program

• Proposed NASA space probes
• NASA programs
• Cancelled spacecraft
• Missions to Neptune
• Missions to Pluto

• Articles with short description
• Short description matches Wikidata