Complex sentence: Phobos 1 failed before it could achieve its main scientific objectives, and while the Phobos program as a whole can be considered a failure, the probes discovered previously unknown information concerning Mars and Phobos during their lengthy orbital flights.
Split into simpler sentences: Phobos 1 failed before it could achieve its main scientific objectives, and while the Phobos Program as a whole can be considered a failure. The probes discovered previously unknown information concerning Mars and Phobos during their lengthy orbital flights.