actual magnitude of the pull-in torque at a desired pulse rate is more of an iterative process. A relatively  simple method that is not as laborious of continually increasing the torque test by test is to run the actuator at the desired pulse rate and increase the torque until the unit pulls-out of synchronous  operation. While the unit is “buzzing” in this pulled out condition, decrease the brake torque until the actuator regains synchronous operation. Stop the unit and allow the actuator to return to room  temperature, then test the pull-in torque at the torque value that returned the actuator to synchronous operation. A final minor adjustment may be necessary, but this value should be a negligible difference to  the actual pull-in torque value.  Now that the performance at room temperature has been characterized, it may be desired to simulate or  test the performance at maximum temperature. It is actually simple to simulate high temperature  performance at ambient room temperature by calculating the motor resistance and power input as described in Equation 7 and Appendix A. With the reduced power calculated, simply adjust the power input to the supply to apply the high temperature input power, and duplicate the dynamic tests described above.  Adjusting the supply voltage cannot simulate testing an actuator at colder temperatures. While the  electromagnetically generated torques are proportional in decreasing temperature, increased lube viscosity could dominate at colder temperatures and increase torque losses greater than the increased generated torque through reduced resistance. Testing inside a temperature chamber may be the only  alternative, but if the cold temperature values are well within a lubricant’s rating, room temperature  performance may be acceptable.    Conclusion Linear interpretation to simulate stepper motor performance when introduced to load inertia, given motor  performance parameters, such as Motor Constant, Response Rate Constant and Motor frictional components has been presented. The analysis shows how to predict performance at room temperature  as well as elevated temperatures. The linear approximation, however, does not predict actual variances  (Cardinal Maxima and Minima) that naturally occur in stepper motor actuators. The magnitude and frequency of these variances that occur can be minimized through damping techniques.     The industry has applied the requirements of Torque Margin in many ways. To consolidate efforts and  avoid over-margining, a breakdown of torque components and applied reasonable margins, in  accordance with GSFC-STD-7000 has been presented.    Finally, recommendations for proper actuator specification and verification requirements were detailed. It is extremely important to conduct acceptance testing with a controller and test set-up that reflects the actual drive method and operational conditions that the actuator will see in the instrument.  References 1. Scott Starin “Stepper Motor Product Catalog and Design Guidelines V2.3” November, 2013   2. GSFC-STD-7000, “General Environmental Verification Standard” (GEVS), NASA Goddard Space  Flight Center, Greenbelt, MD USA, 2005 3. Shane Brown, Scott Starin “Implications of Underdamped Stepper Mechanism Performance and  Damping Solution Methodology”, Proceedings of the 39 thAerospace Mechanism Symposium,  NASA Marshall Space Flight Center, May 7 – 9, 2008 387