Editing Viking program (section)

===Navigation and communication===
An acquisition [[Sun sensor]], a cruise Sun sensor, a [[Canopus]] [[star tracker]] and an inertial reference unit consisting of six [[gyroscope]]s allowed three-axis stabilization. Two [[accelerometers]] were also on board.

Communications were accomplished through a {{Nowrap|20 W}} [[S-band]] (2.3 [[gigahertz|GHz]]) [[transmitter]] and two {{Nowrap|20 W}} [[TWTA]]s. An [[X-band|X band]] {{Nowrap|(8.4&nbsp;GHz)}} [[downlink]] was also added specifically for [[Doppler effect|radio science]] and to conduct communications experiments. [[Uplink]] was via S band {{Nowrap|(2.1&nbsp;GHz).}} A two-axis steerable [[Directional antenna|parabolic dish antenna]] with a diameter of approximately 1.5 m was attached at one edge of the orbiter base, and a fixed low-gain antenna extended from the top of the bus. Two tape recorders were each capable of storing 1280 [[megabit]]s. A 381-[[MHz]] relay radio was also available.{{citation needed|date=December 2023}}