MIT Space Systems Laboratory Chart: 1 August 23, 2002 de Weck, Miller and Mosier Multidisciplinary Analysis of the Multidisciplinary Analysis of the NEXUS Precursor Space Telescope NEXUS Precursor Space Telescope Olivier L. de Weck David W. Miller Gary E. Mosier Olivier L. de Weck David W. Miller Gary E. Mosier [email protected][email protected]millerd millerd @ @ mit mit .edu .edu gary gary .e. .e. mosier mosier .1@ .1@ gsfc gsfc . . nasa nasa . . gov gov SPIE SPIE - - 4848 4848 - - 39 39 Highly Innovative Space Telescopes Highly Innovative Space Telescopes Session 6: Detectors, Modeling and Testbeds Session 6: Detectors, Modeling and Testbeds SPIE Astronomical Telescopes and Instrumentation SPIE Astronomical Telescopes and Instrumentation 22 22 - - 28 August 2002, Waikoloa, Hawaii, USA 28 August 2002, Waikoloa, Hawaii, USA
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Multidisciplinary Analysis of the NEXUS Precursor Space Telescope · • For new generation of lightweight, deployable telescopes such as NGST and NEXUS the disciplines of structures,
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MIT Space Systems LaboratoryChart: 1August 23, 2002
de Weck, Miller and Mosier
Multidisciplinary Analysis of theMultidisciplinary Analysis of theNEXUS Precursor Space TelescopeNEXUS Precursor Space Telescope
SPIESPIE--48484848--3939Highly Innovative Space TelescopesHighly Innovative Space Telescopes
Session 6: Detectors, Modeling and TestbedsSession 6: Detectors, Modeling and Testbeds
SPIE Astronomical Telescopes and InstrumentationSPIE Astronomical Telescopes and Instrumentation2222--28 August 2002, Waikoloa, Hawaii, USA28 August 2002, Waikoloa, Hawaii, USA
MIT Space Systems LaboratoryChart: 2August 23, 2002
de Weck, Miller and Mosier
Problem SettingProblem Setting
Disturbances
Opto-Structural Plant
White Noise Input
Control
Performances
Phasing
Pointing
Appended LTI System Dynamics
(ACS, FSM)
(RWA, Cryo)
d
w
u y
z
Σ ΣActuator Noise Sensor
Noise
Jz,1=RMMS WFE
[Ad,Bd,Cd,Dd]
[Ap,Bp,Cp,Dp]
[Ac,Bc,Cc,Dc]
[Azd, Bzd, Czd, Dzd]
z=Czd qzd
“Science Target Observation Mode”
Parameters: pj Jz,2 = RSS LOS
Traditionally: Define System Parameters pj = po Predict H2 performances Jz,iIsoperformance: Find Locus of Solutions pLB < pj < pUB Constrain performances Jz,i = Jz,req
MIT Space Systems LaboratoryChart: 3August 23, 2002
Improvements are achieved by a well balanced mix of changes in thedisturbance parameters, structural
redesign and increase in control gainof the FSM fine pointing loop. Centroid X
MIT Space Systems LaboratoryChart: 12August 23, 2002
de Weck, Miller and Mosier
Paper ConclusionsPaper Conclusions
• For new generation of lightweight, deployable telescopes such asNGST and NEXUS the disciplines of structures, optics and controls are coupled and must be considered together during early design stages
• Performance predictions can be made for “engineering” metrics such as WFE, LOS jitter etc that flow down from science requirements. These predictions are based on integrated models, but are uncertain and depend on many assumptions.
• Nevertheless one can gain valuable insights from sensitivity analysis to identify key driving system parameters.
• Isoperformance seeks not the best achievable performance, but acceptable performance, while balancing the burden among subsystems.
• Error budgeting and Integrated Modeling can be linked.