430 a toolkit of hardware and flexible software to respond to the particular needs of the application producing  jitter.  

The paper addresses the experience and capabilities for jitter verification at BATC . In particular, the  following topics are discussed:   

(a) The modal characteristics of measuring platform s and their dynamic coupling with the behavior of  the instrument under test. Often, the potential for interaction between the instrument and the  measurement platform prompts t he identification of the frequency content of the setup in the  frequency band of interest. In addition, the type, number and layout of the force sensor s together  with the choice of the encapsulating hardware are discussed in light of stiffness and  measurem ent requirements.  

(b) The different methods used for dynamic calibration of a  six-degree of freedom FMP  in light of the  test setup environment, and applicable requirements.  These include harmonic stinger tests,  frequency response function tests, speaker tests  and independent measurement verification , e.g. ,  through a Vibration Lab data acquisition system network  or portable systems . 

(c) The handling of background noise to ensure adequate measurements. There are two sources of background noise:  one from the measur ing equipment  used in the test setup and the other is of  environmental origin, often induced by nearby operating machinery and/or  human activities.  

Finally, t he paper gives e xamples of jitter measurement, mitigation and verification of mechanisms,  includ ing cryocoolers and momentum wheels.   

Measurement Verification     Fast steering mirrors,  gimbals , reaction wheels, shutter mechanisms, cryocoolers  and other instruments  with moving components impart dynamic loads that require proper characterization to meet mission requirements such as those involving line of sight stability, optical jitter and image quality.  These dynamic  loads need to be measured and often mitigated using advanced design layouts. In certain mechanisms  involving optical systems such as f ast steering mirrors, gimbals , reaction wheels, shutter mechanisms,  cryocoolers  and other instruments with moving components , inertial load couplings and reactions from  actuation need to be cancelled and therefore the v erification of imparted loads becomes essential during  the integration of the mechanisms. In many applications, jitter elimination is addressed through either  active or passive isolation sy stems.  The performance of such systems needs to be evaluated through  measurements and FMPs are essential for such verifications.   

Over the past  twenty five years, BATC built and internally calibrated several  multi- degree of freedom  precision FMPs  to measure jitter and reaction loads from  space instruments.  Some of the tables are static  and others are dynamic, capable of simulating complex multi -axis external jitter input. These tables were  used for multiple space programs and in multiple environme nts, including vacuum, cold temperature,  simulated weightlessness (as low as a fraction of 1 Hz).  In addition to simultaneously measuring three  forces and three moments in the time and frequency domains, the tables were used for static and  dynamic balancing, JPL’s f orce limiting during environmental testing,  and bearing contact angle  verification.  Depending on the application,  FMPs  were developed to meet a variety of requirements  involving particular geometric configurations , weight, stiffness , and low jitt er load amplitudes and  frequencies . Some FMPs  were built for applications where the frequency of interest is around 0.5 Hz .  Other dynamometers were built to handle high frequency measurements where stiffness requirements are dictated by high bandwidth cont rol loops (e.g. , fast steering mirrors).    Because t here is no dynamometer  that can address all sorts of requirements  from one program to  another , BATC elected to acquire the capability to rapidly put together c ustomized exported force and  torque (EFT)  test setups depending on the mechanism under test and what is being measured.  To this