Mars 2M No.521, also known as Mars M-69 No.521 and sometimes identified by NASA as Mars 1969A, was a Soviet spacecraft which was lost in a launch failure in 1969. It consisted of an orbiter. The spacecraft was intended to image the surface of Mars using three cameras, with images being encoded for transmission back to Earth as television signals. It also carried a radiometer, a series of spectrometers, and an instrument to detect water vapour in the atmosphere of Mars. It was one of two Mars 2M spacecraft, along with Mars 2M No.522, which was launched in 1969 as part of the Mars programme.

Wikipedia: https://en.wikipedia.org/wiki/Mars_1969A. Original timeline Wikipedia link: https://en.wikipedia.org/wiki/Mars_program. Related NASA reference: https://nssdc.gsfc.nasa.gov/planetary/chronology.html#1969. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).