PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 2004-09-20 NAIF:Semenov initial version; 2005-03-01 NAIF:Semenov Post 2004 peer-review update " RECORD_TYPE = STREAM OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "SDU" INSTRUMENT_ID = "DYNSCI" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "DYNAMIC SCIENCE EXPERIMENT" INSTRUMENT_TYPE = "ATTITUDE CONTROL SYSTEM" INSTRUMENT_DESC = " Instrument Overview =================== The instrument used in the Dynamic Science Experiment conducted during the Stardust spacecraft encounter with comet Wild 2 on January 2, 2004 was the Stardust spacecraft itself, or more specifically the spacecraft's Attitude Control System (ACS). During the encounter ACS provided a significant measure of the spacecraft's performance and the control system's reaction to particle impacts. Throughout the encounter the control system maintained a three-axis stabilized attitude. The controller also included the capability to command a roll (about the spacecraft X-axis) just before closest approach. Using an updated comet trajectory computed in flight software, the controller commanded a slew to keep the comet in view of the Navigation Camera. As the comet passed, the controller commanded a return slew. The spacecraft commanded two groups of thrusters for control. Four 1.0 lbf (nominal) thrusters were available for the bang-bang control and slews. Four 0.2 lbf (nominal) thrusters were used for limit cycling and small error correction. Four of each were available as spares. The larger thrusters were designated TCM thrusters; the smaller, RCS thrusters. RCS thrusters 1-4 and TCM thrusters 1-4 were used during encounter. RCS 5-8 and TCM 5-8 were not used. Scientific Objectives ===================== The ACS provided data on attitude changes which result from particle impacts. Analysis of this information could be useful in diagnosing large particle impact events. For more information see Anderson et al 2003. Calibration =========== N/A. Operational Considerations ========================== N/A. Detectors ========= The detectors used in this experiment included the ACS that measured source data for and computed spacecraft orientation and angular rate and ACS thrusters electronics used to record thruster firing times and durations. Electronics =========== N/A. Location ======== This section contains information about ACS thruster locations and thrust vector directions, spacecraft center of mass location, and spacecraft moments of inertia. Spacecraft mass, kg: M = 330.979 Spacecraft products and moments of inertia with respect to (w.r.t.) the spacecraft coordinates translated to spacecraft center of mass, kg/meter^2: Ixx = 87.6748 Iyy = 200.2580 Izz = 241.1340 Ixy = 0.2169 Ixz = 4.1547 Iyz = -1.4881 Spacecraft center of mass w.r.t. spacecraft reference frame, meters: CM = [ -1.18277, -0.000567, 0.0340397 ] Effective thrust direction unit vectors w.r.t. spacecraft reference frame (unit vector): RCS1 = [ 0, -0.2588, 0.9659 ] RCS2 = [ 0, -0.2588, 0.9659 ] RCS3 = [ 0, 0.2588, 0.9659 ] RCS4 = [ 0, 0.2588, 0.9659 ] RCS5 = [ 0, -0.2588, 0.9659 ] RCS6 = [ 0, -0.2588, 0.9659 ] RCS7 = [ 0, 0.2588, 0.9659 ] RCS8 = [ 0, 0.2588, 0.9659 ] TCM1 = [ -0.1736, 0.2549, 0.9513 ] TCM2 = [ 0.1736, 0.2549, 0.9513 ] TCM3 = [ 0.1736, -0.2549, 0.9513 ] TCM4 = [ -0.1736, -0.2549, 0.9513 ] TCM5 = [ -0.1736, 0.2549, 0.9513 ] TCM6 = [ 0.1736, 0.2549, 0.9513 ] TCM7 = [ 0.1736, -0.2549, 0.9513 ] TCM8 = [ -0.1736, -0.2549, 0.9513 ] Thruster location w.r.t. spacecraft reference frame, meters: RCS1 = [ -0.7176, 0.2606, -0.5072 ] RCS2 = [ -1.662, 0.2606, -0.5072 ] RCS3 = [ -1.662, -0.2606, -0.5072 ] RCS4 = [ -0.7176, -0.2606, -0.5072 ] RCS5 = [ -0.7691, 0.2606, -0.5072 ] RCS6 = [ -1.611, 0.2606, -0.5072 ] RCS7 = [ -1.611, -0.2606, -0.5072 ] RCS8 = [ -0.7691, -0.2606, -0.5072 ] TCM1 = [ -0.6132, 0.257, -0.5159 ] TCM2 = [ -1.767, 0.257, -0.5159 ] TCM3 = [ -1.767, -0.257, -0.5159 ] TCM4 = [ -0.6132, -0.257, -0.5159 ] TCM5 = [ -0.6647, 0.257, -0.5159 ] TCM6 = [ -1.715, 0.257, -0.5159 ] TCM7 = [ -1.715, -0.257, -0.5159 ] TCM8 = [ -0.6647, -0.257, -0.5159 ] This -Z view of the Stardust spacecraft illustrates locations of the thrusters: .-. | |---------------.---------------.--------------. | | | | | | | | | | | | | CIDA | | +Y Solar | | +Y |.-------. | | Array | | ^ /.---------.-. | | | |----------|----\`---------'-' -'--------------' `-' || T1-T5-----------T6-T2 .-. || |O O * * * * O O|/| .' `. +Z || | R1 R5 R6 R2 | |/ \ <-------x| | | o | Return +X | | R4 R8 R7 R3 | |\ / Capsule | |O O * * * * O O|\| `. .' .-. | T4-T8-----------T7-T3 `-' | |---------------.-| |---| |-.--------------. | | | `-----' `-' | | | | Periscope NAVCAM| | -Y Solar | | | | | Array | | | | | | | | | | | |---------------'---------------'--------------' `-' O -- TCM Thrusters * -- RSC Thrusters Operational Modes ================= The spacecraft was 3-axis stabilized during the whole mission. During the comet Wild 2 encounter the spacecraft had its +X axis pointed to the incoming comet dust stream while keeping the spacecraft-to-comet vector in spacecraft the XZ plane to allow tracking of the nucleus by the navigation camera. Subsystems ========== The Stardust ACS subsystem included thrusters, IMU, star camera, and controlling electronics and software. Stardust performed attitude control and propulsive maneuvers using a redundant helium-fed mono-propellant (hydrazine) propulsion subsystem. This subsystem was comprised of one titanium propellant tank and a total of 16 thrusters (two strings of 8), all mounted on the lower deck of the spacecraft (opposite the high-gain antenna and solar panels - pointing toward the -Z axis of the spacecraft to avoid potential contamination of the aerogel collector located on the +Z size of the spacecraft). Eight of these were 0.2 lbf thrusters and were used primarily for attitude control. The other eight were 1.0 lbf thrusters and were used for propulsive maneuvers. Measured Parameters =================== The parameters measured during this experiment included spacecraft orientation and angular rate and times and durations of ACS thruster firings." END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "ANDERSONETAL2003" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END