around the antenna dish when the HGAS is deployed. The g-negation system, with HGAS integrated to  the spacecraft, is shown in Figure 4. Stow/Deployment Bias  Ideally the system will exactly negate the effects of gravity on the HGAS for ground tests. As this is not  feasible, the g-negation system will either hinder or aid in the deployment of the system. In order to confidently qualify the deployment system, it is important that the g-negation system does not assistdeployment. To be conservative in ground testing, the system should be tuned to slightly hinder  deployment or bias the system toward the stowed configuration. This is referred to as stow bias. Stow bias is the load or torque applied by the gnegation system that retards system deployment compared to a “perfectly” gravity negated state. Adeployment bias would be a load or torque that assists deployment.  The starting point for calculating the masses of the gnegation system’s three elements was the development of an accounting/moment balance spread sheet. This spreadsheet tracked mass and moment  arm for the lower and upper booms separately as well  as the three g-negation elements. The mass and moment arm data was comprised of actual measured inertia, CAD-based inertial information, and engineering estimates. This data was used to sum the  torques and masses and determine what counter masswas needed for each of the three g-negation elements. This g-negation configuration is specific to the flight hardware configuration for which it was determined.  During HGAS subsystem integration, the g-negation  was verified by removing the deployment springs (harness was not present at this time) and observing system motion. Small changes to the mass configuration were made to fine tune the system.  Any mass changes to the deployable section of the HGAS impacts the g-negation configuration. The  addition of T-Vac test instrumentation, then vibration test instrumentation, and later removal of this  hardware required changes to the g-negation mass configuration. These changes were determined analytically, with the balance spreadsheet, as it was no longer an option to remove the harness and  deployment springs to verify the stow/deployment bias. This is a key limitation in ground testing.   Deployment Instrumentation As part of the ground support equipment, instrumentation was developed to document deployment tests.  Inclinometers were added to the lower and upper b ooms to track their angles during deployment. L oads  in the g-negation system were recorded via two load cells on either end of the C-hook cable assembly. The load cells were used primarily to ensure the stow/deployment bias did not change appreciably during  deployment. Data from the inclinometers was more useful. From inclinometer data, the deployment rates for the shoulder and elbow hinge can be determined, as well as the elbow delta angle /g11/g507/g12/g17 This data is  shown in Figure 5. Subtleties of G-negation System There were several subtleties discovered during the early trials. While the gantry cable and pulley system  is intended to only apply a vertical force to g-negate the upper boom/ gimbal assembly, any tendency of   Figure 4. HGAS during g-negated  deployment testing, integrated to GPM  spacecraft 49