Modal-Testing Options for Spacecraft Developments

This paper describes the current options for performing modal tests of spacecraft structures. Excitation options include sine dwell, sine sweep, fast sine sweep (chirp), random, initial velocity (impulse), initial displacement (twang), and ambient. Mode detection and modal tuning are discussed. Several methods of modal characterization are examined. These include tuned dwell, tuned sweep, curvefitting to frequency-response data, and time-domain analysis. Comparision of the various options are made on the basis of practical and theoretical observations as well as results of comparative tests performed on a simple structure.