latter was also measured using the dynamometer as the sum of the contributions of all load cells. The  load is applied along the Y direction of the dynamometer. The input loads matched the output load. The  Spectral Dynamics Data Acquisition System of BATC’s Vibration Lab was also used to further check the  response and the results. They were found to be identical to the reference load.  Frequency response function (FRF) tests The FRF shows that the data is unaffected by the fundamental modes of the dynamometer either in a  clamped or a simply supported configuration. The difference in loads is negligible in the vicinity of 0.5 Hz.While the results of the excitation illustrated in Figures 6 and 7 are for the Y-axis, similar results are  recovered for the X-axis. The FRF was also measured prior to balancing GMI either in the clean room or in the vacuum chamber BRUTUS where additional modes are present due to the mounting equipment.  The mount and fixture hosting GMI during spin balance testing in the BRUTUS vacuum chamber is analyzed using the finite element method incorporating a GMI model to ensure that we have nointerference from the added structural resonance modes. The mounting beams in BRUTUS (Figure 2b) were stiff enough and produce no modes that interfere with measurements.   Speaker tests The goal of the dynamic calibration using a speaker load input is to verify that we are reading the correct  dynamic loads while balancing the GMI instrument, no matter where these loads are applied over the dynamometer. The calibration consists in applying known forces using a speaker precisely oriented andlocated at different elevations over the dynamometer and measure the reaction forces and moments imparted on the surface of the dynamometer. The speaker is attached to a fixture through an  encapsulated load cell to ensure a precise knowledge of the magnitude and location of the excitation. The speaker is actuated using a form generator to deliver an accurate input frequency. The test shows the  input load from the speaker force transducer and the measurement from the dynamometer are the same  in different orientations. In particular, this test is required to verify the correctness of the measured  moments which are crucial for dynamic imbalance predictions. Risk Mitigation Balance Tests In order for the GMI balancing task to run smoothly, a risk reduction set of tests were carried using the  SMA drive and a flywheel on which known masses are placed in well-known locations on the flywheel as shown in Figure 8. The first test consists of the placement of an imbalance mass of about 1.1-lb (4.9-N) at  the edge of the flywheel. The second test is an extreme case created by a 16-lb (71-N) imbalance, also  placed at the edge of the flywheel. Finally, the last case is of a situation in which an attempt was made to balance the flywheel and the SMA to the best available capabilities. The results of this test points to how a balanced situation results in very small shear and moment loads exported to the mount of the SMA. The data from the dynamometer is compared to the mass tally data. It is found that accurate estimates of the  imbalance can be made using the dynamometer. In addition, a balanced state can be easily identified  once the shear force and moment become small . In the first test case, a set of known imbalance masses were placed on the bare flywheel .Knowing the  location of the masses, a static imbalance of 13.491 in-lb (1.5243 N-m) and a dynamic imbalance of  139.077 lb-in2(0.040699 kg-m2) are computed. The total mass of the added hardware consisting of studs,  washers and spacers weighs 1.1075 lb (4.9264 N) and its center of mass is located at a radius of 12.18 in(30.93 cm). The radial force and radial moment maintain a nearly constant value as the SMA and its  payload rotate. The mean static and dynamic imbalances given by Equations (4) and (5) are computed over a period of 70 seconds at a rate of 1 KHz. These values are within 1% of the expected values as  shown in Table 1. The second test is an extreme case in which 18.20 lb (80.95 N) is placed at the edge of the flywheel to produce an imbalance which is about 100 times the imbalance requirement. The static and dynamic imbalances are about 270 lb-in (30.5 N-m) and 2900 lb-in 2(0.8487 kg-m2) respectively. The total  mass of the added hardware consisted of two dumbbells, studs, washers and spacers is 18.2025 lb(80.9688 N). Again, the radial force and radial moment maintained constant values as the SMA and its flywheel payload with imbalance mass rotate and the system recovered the static and dynamic imbalances with errors of 0.41% and 1.8% respectively. In the third test case, the measured mean 311