204 The BEI ARA nanoSer ies encoders  have demonstrated resolutions  up to 25 bits and absolute position  accuracy  less than 5 μrad rms over a full revolution  at data rates  of up to 8 kHz. The power dissipation for the  readhead at that rate is just 0.6 watt, while  the remote electronics  will consume about  3.0 watts  with a 5-volt  supply  and a single  readhead,  and a little more if the 24-volt option is used.  The remote  electronics  has been   designed to handle up to four readheads  with no reduction.  

BEI can also supply  engineering prototype units.  Our AIME nanoSeries  encoders  are industrial temp  range   encoders  that mimic  the readhead  size of the ARA nanoSeries  encoders.  These much less  expensive units   are form, fit and function equivalent  to the ARA space encoder  readheads, even to using the same test  box design.  The AIME  encoders  do not require  a remote electronics assembly  however,  since  the complete  electronics  package can be fit inside  the space of the ARA readhead enve lope.  This allows  for cost-effective   prototypes  and risk reduction units  to make system  checkout  much easier  and with much  higher  fidelity.  The  AIME encoders  are not rad-hard, but  are a logical choice  for any application  that is less demanding.  The  same  code disk sizes  and hub/readhead materials are used for  both designs.    It is important  to know  how well a kit encoder  is mounted and calibrated and the effects  of spindle runout   and environments  on the encoder  during operation.  Standard interface and test boxes  are available for  power,  communications  and evaluat ion of the health/status of  the ARA and AIME encoders.  These test  boxes  provide the ability  to command auto- calibration,  normal  operation,  set output  parameters,  and  evalua te and view in real time the quality  and status  of each tier of position information and the alignment  of  all other  position  tiers internal  to the encoder.  This information is output  in part through health and status  bits with each position  output  word and is valuable  in determining if and when  re-calibrat ion in-situ may be  needed. In- situ calibration can compensate for  changes  in gravitational  loads,  component  drifts  and  degradation due to extreme environmental conditions  such  as radiation,  although generally  adjustments  will  not be necessary.  The test box software is written in LabVIEW and can suppor t position reporting, analysis,  control, and data logging.    For the future,  it should be clear  that the new ARA nanoSeries  space  encoder  has the potential  to  dramatically  improve  performanc e of space systems,  especially  when paired  with a servo  system designed   by BEI. BEI has primarily  been involved in precision servo  systems for  only the most demanding  applications,  such  as the pointing  systems in the Hubble  Space  Telescope,  or for  the Microwave  Limb   Sounder,  one of four instruments  on the NASA’s  EOS AURA satellite.  Today’s  space systems  are  smaller,  lighter,  and higher  performance than in the past,  and BEI  can bring  our experience in designing  space systems  to assist  you in meeting  and exceeding your most  stringent program performance  requirements.