John Martin April 5, 2001 SuperNova/ Acceleration Probe (SNAP) Introduction

SNAP, June 25-28, 2001 Goddard Space Flight Center System Introduction Page 2 Summary Observations  Final choice of orbit requires more analysis  Each option considered has significant advantages, but also has significant disadvantages  Lunar assist option requires extensive analysis for final choice, but bus design can handle a reasonable class of alternatives  Eclipses are infrequent, but large enough to drive the system design  Overall, the spacecraft appears within current technology  1 Gigapixel camera sounds impressively large  Jitter requirement requires careful attention

SNAP, June 25-28, 2001 Goddard Space Flight Center System Introduction Page 3 Headlines  System - Gabe Karpati  Understanding how to build the bus is easier than understanding which orbit to choose  Flight Dynamics - Marco Concha  Ability to lower apogee after lunar assist appears quite reasonable  Mechanical - Dave Peters  Spacecraft bus is a custom but not unusual structure which can be handled by expected launch vehicles  Thermal - Wes Ousley  Spacecraft thermal design driven by the long ecipse time and large propulsion system

SNAP, June 25-28, 2001 Goddard Space Flight Center System Introduction Page 4 Headlines  Power - Bob Beaman  Power needs during the occasional, long eclipse require a large battery  Attitude Control - Aprille Ericsson  Design is well-understood, but jitter requirement and use of imager output for guidance are of concern  Command & Data Handling - Terry Smith  Image data limited to real-time transmission; other data will be stored during non-contact periods  Flight Software - Ed Greville  Flight software for this mission is not unusual

SNAP, June 25-28, 2001 Goddard Space Flight Center System Introduction Page 5 Headlines  Data Systems - Ron Vento  Large data volume dictates use of Ka-band and extensive ground station contact time  Mission/Science Operations - Tim Rykowski  Existing Berkeley SSL MOC well-suited to support SNAP  Reliability & Safety - David Bogart  In addition to usual reliability/redundancy items, consider redundant means of opening telescope door and selecting filter wheel position

SNAP, June 25-28, 2001 Goddard Space Flight Center System Introduction Page 6 Additional Information

SNAP, June 25-28, 2001 Goddard Space Flight Center System Introduction Page 7 Study Particulars  Name:  SuperNova/ Acceleration Probe (SNAP) SNAP_Discipline.ext used for discipline file names  Dates:  June 25-28, 2001  Client Representatives:  Michael Levi, Lawrence Berkeley National Lab  David Penkow, UCB/SSL  Mike Lampton, UCB/SSL  Manfred Bester, UCB/SSL  Participants:  See the file SNAP_Attendance.xls

SNAP, June 25-28, 2001 Goddard Space Flight Center System Introduction Page 8 Propulsion Subsystem Advice  Propulsion tank (or tanks) should be located close to the center of gravity, minimizing shifting the CG as propellant is used  Tanks should be located close together, with thermal controls if needed to keep all tanks near the same temperature, minimizing pressure differentials between tanks  Thrusters should be located near the tanks to minimize thermal controls required to keep lines from freezing  Thrusters should be placed to keep plumes away from optics  Imaginary lines connecting the thrusters construct a geometry which must include the spacecraft center of gravity  Failure of a single thruster may change the geometric figure defined by working thrusters, but must still include the CG  Use the smallest thrusters that will do the “job”