On Vibration-Design Aspects Of An IR - Scanning Earth Sensor

The paper discusses the design considerations made on a 'scanning earth sensor' in order to avoid the possible failure of the system due to resonance induced by the vibrations generated during the launch and by the vibrations existing on the spacecraft structure. The most severely affected part of the sensor is its scan mechanism. The scan mechanism consists of a scan mirror and an angle encoder which are fixed on a torsional flexture. The oscillating frequency of the mechanism is made use of, in the necessary attitude determination and control process of the satellite. The transverse frequencies of the flexture are brought to a safe range by adjusting the tension on the flexture which in turn, eliminates the encoder-reference errors. An experimental set up is established in which a reflective sensor is used to measure this frequency which yields the tension on the flexture. This methodology for measurement of frequency and tension is successfully realized and the sensor is qualified in the necessary vibration test requirements of the mission.