Viking 1 Orbiter Chronology

Date                   Revolution                     Event 
 
June 19, 1976              0         Mars orbit insertion 

June 21, 1976              2         Trim to plan site certification orbit 

July 9, 1976               19        Orbit trim to move westward 

July 14, 1976              24        Synchronous orbit over landing site 

July 20, 1976              30        VL-1 landing 

August 3, 1976             43        Minor orbit trim to maintain 
                                     synchronization 

Sept. 3, 1976              75        VL-2 landing 

Sept. 11, 1976             82        Decrease of orbit period to begin 
                                     eastward walk 

Sept. 20, 1976             92        Orbit trim to permit synchronization 
                                     over VL-2 

Sept. 24, 1976             96        Synchronous orbit over VL-2 

Jan. 2, 1977              213        Period change to approach Phobos 

Feb. 4, 1997              227        Orbit synchronization with Phobos 
                                     period 

Feb. 12, 1977             235        Precise correction to Phobos 
                                     synchronization 

March 11, 1977            263        Reduction of periapsis to 300 km. 

March 24, 1977            278        Adjustment of orbit period to 23.5 
                                     hours 

May 15, 1977              331        Phobos avoidance maneuver 

July 1, 1977              379        Adjustment of period to 24 hours 

Dec. 2, 1978              898        Adjustment of orbit period to 24.85 
                                     hours; beginning of small walk around 
                                     the planet 

May 19, 1978              1061       Adjustment of orbit period to 25.0 
                                     hours; acceleration of walk rate 

July 20, 1979             1120       Raising of periapsis to 357 km. 
                                     Adjustment of orbit period to 24.8 
                                     hours and slowing of walk rate.