Mariner 6 and Mariner 7 successfully completed every one of the missions' science and engineering objectives during their average 219, 000, 000 mile trip to and close fly-by of the planet Mars in 1969. Man's knowledge of the “red planet” has greatly increased with the Television, Infrared Spectrometer, Ultraviolet Spectrometer, Occultation and Celestrial mechanics data returned by both Mariners.The Mariner '69 was based on a design of its predecessors, had incorporated a significant increase in flexibility that made it much more difficult to test, but yet afforded the opportunity to overcome many problems in the ground test program and compensate for all problems experienced during flight.The Test and Operations Program experienced serious problems at the start, throughout, and during the final week of launch preparations. The test organization, test procedures, spacecraft test equipment, and the project support allowed these problems to be handled in a manner that permitted the spacecraft to meet the very inflexible launch opportunity.The Mariner '69 System Test and Operation Program was not perfect but effective. The major problem in conducting the program was mainly related to the relatively short period of allowable test time. All objectives of the test program were met although in some cases they were compromised.Most of the design and workmanship problems were solved during the ground testing. However, some problems were uncovered in flight that were missed on the ground, but their effects were capable of being reduced because of the experience and knowledge gained during the ground test program, and because of the spacecraft design that provided the necessary flexibility to permit corrective actions to be taken.