156 Introduction  

CubeSats were developed wi th the intention to bring spaceflight designs and capabilities to academia. Early  in their development, academic institutions composed a majority of the market  but a decade later   government agencies and large businesses noticed the opportunity to produce big science at low cost s.  This adaptation of the CubeSat intent required these high- capital entities to compress the form factors of  conventional satellites into those outlined  in the CubeSat Design Specification. With the growing popularity  and development of CubeSats, designers, analysts, and manufacturing specialists noted that the  requirements given in the CubeSat Design Specification demanded complicated, miniature systems to  accomplish difficult tasks2. Numerous  CubeSat programs became acquainted with this reality . Thanks to  the growing market and development of low -cost launching capabilities for micro-  and nano- scale satellites,  universities, private industries, and government agencies have maneuvered large programs to take  advantage of the Cube Sat technology . Many of these CubeS ats have the potential to become engineering  marvels  - they encounter technical issues (thermal, mechanical, and power limitations) similar to larger  scale projects, but develop solutions at fractions of the cost . NEA Scout follows this suit . NEA Scou t will  employ the largest deployed solar sail to date to fly to a near -earth asteroid. The science instrument aboard  NEA Scout will then characterize the asteroid by gathering shape, location, inertial properties and  compositional information. The collected information will fill strategic knowledge gaps and lay the needed  groundwork for future missions and the eventual human exploration of asteroids1.  

Solar sails create propulsion without propellant, but the physics that makes  them excel in efficiency and  endurance also limits their ability to accelerate and decelerate quickly . Solar sails produce thrust by  reflect ing solar radiation with large areas of light weight  material . The reflected light produces solar pressure,  which then propels the vehicle with control forces on the magnitude of µN/m2 of sail material . The thrust,  though miniscule in size,  can produce large velocity deltas over  a multi- year mission . These small forces  also create disturbance torques caused by misalignments in the CM and CP . Although the CM and inertial  properties can be easily measured or calculated, the CP of the solar sail is less exact . Guidance, navigation  and control engineers have estimated the CP location with considerable margin due to the possibility of sail  tears, asymmetry and non- planar shaping. NEA Scout’s estimated CP/CM offset is large enough (about   2 cm at beginning of mission  and 4 cm at end of mission) to overload the control systems and requires a  mechanical system to adjust the center of mass and trim the spacecraft . This mechanical system became  the Active Mass Translator (AMT).  

Design Constraints  

Volume,  Mass and Power   The AMT’s early design activities acquainted the design and analysis team with numerous design  constraints and complications.  The first few parameters - volume, mass, and power - commonly limit the  design space on flight systems  and were considered the highest level requirements for the AMT due to the  vehicle’s size, mission , and risk level . Again, the nuances of the AMT design further complicated these  three requirements . First, the AMT could occupy a volume no l arger than 22.6 x 10.0 x 1.7 cm  (x y z  coordinates, respectively) . Within this design space, the complete system, including all thermal and  electrical components, could weigh no more than 320 grams. This design correlates to less than 5% of the  vehicle volume and less than 2.5% of the NEA Scout’s mass. As with many other orbiting and deep space  vehicles , individual systems’ power demands are limited and carefully monitored . The AMT was allowed  0.5 W during standby and 12 W when operating during cruise. The power requirement include d the control  board, motors, sensing, thermal blankets, and locking mechanisms . These components were chosen   accordingly.  

Feedthrough Bundle and Mobility   The next  lower  level requirements were levied by the AMT’s neighboring systems . The AMT resided in  between the deployer for the solar sail and booms and the avionics box.