Programmatics & Customer Liason
* Formalized the transition from the Micro-Precision CSI Program to the Interferometry Technology Program (ITP) as this programmatic entity will henceforth be called. The ITP embraces technologies like laser metrology and interferometric starlight detection in addtion to the traditional CSI technologies of precision stabilization and control. Intensive planning is underway, both internal to JPL and with NASA HQS, to define the deliverables, schedule, facilities, and resources associated with the new program. A substantial increase over the FY'95 NOA of $2.0M is anticipated.
* Completed an update to the Technology Plan for Space Interferometry Missions dated 31 July 1995. This plan is based upon the most current thinking in Code S as to their roadmap for space interferometry missions. As such it concentrates on the technology needs of the SIM / OSI mission, with secondary consideration given to the additional requirements of an ExNPS infrared interferometer and interferometers based on the separated spacecraft architecture. Further updates will be made as Code S refines its mission planning.
* Contributed to presentation material documenting the technology needs of large baseline IR interferometers being considered as part of the Exploration of Neighboring Planetary Systems (ExNPS) study.
* Coordinated with the New Millennium Program in identifying common interests for technology development and demonstration. This coordination will continue as the relationship between the ITP and the New Millennium Interferometer (Deep Space Mission 3) comes into better focus.
Systems & Analysis
* Integrated Modeling of Advanced Optical Systems (IMOS) Version 1.0 is complete. The manual is in the hands of the editor and will be released shortly. This effort represents a major FY'95 deliverable of a generic computer modeling capability critical to the design and analysis of many advanced optical systems, including optical interferometers and sparse aperture telescopes.
* A predictive optomechanical IMOS model of open loop optical performance of the MPI shaker force to fringe position transfer function has been verified. The accuracy of the predicted versus measured rms error is within 10%. This represents completion of one of the program's major milestones for FY'95.
* Initial evaluation of the CSI mode expansion techniques as applied to the current Cassini model has begun. The results thus far have been excellent in taking observed modes at the instrumented degrees of freedom and expanding them to the full analytical model. A paper on this subject entitled "Mode Shape Expansion Techniques for Predition: Part II: Experimental Evaulation.." by Marie Levine, Mark Milman, and Andy Kissil has been accepted for publication in the AIAA Journal.
* Walter Tsuha has converted a NASTRAN model of the February SIRTF baseline configuration to IMOS. Discrepancies in the stiffness matrices between the two models were noticed and resolved.
* Commercialization efforts continued. Marie is finishing a proposal to use mode extrapolation techniques to test dam integrity. This proposal has a high likelihood of being funded. Stephanie, Marie and Milman are working on a proposal on vibration suppression in civil structures. This is to be part of a larger proposal to FEMA and the State of California in collaboration with Flour Corp. and Bechtel. This proposal has a high likelihood of being funded as well.
* Two papers were presented at the ASME Design Engineering Technical Conf. in Boston this Sept. These papers were "Mode shape expansion techniques for model error localization and damage detection" by Marie Levine and Mark Milman; Model updating and evolutionary structures" by Jim Melody and Marie Levine.
* The paper "Wavefront control algorithms and analysis for a dense adaptive optics system with segmented deformable mirror" by Mark Milman and Amir Fijany has been accepted for publication in JOSA A. The paper "Some aspects of the mathematical modeling of wavefront controllers for adaptive optics systems" by Mark Milman and David Redding will appear in the SIAM publication "Control in Industry" edited by I. Lasiecka and B. Morton and published by Birkhauser
* Marie Levine is the recipient of this year's coveted "CSI Dude Award." Congratulations!!
Ground Test & Component Hardware Development
MICRO-PRECISION INTERFEROMETER (MPI) TESTBED
* Through significant tuning of MPI's electrical, computer and optical systems the period of closed loop fringe stabilization has increased to many hours. A redesign of the fringe tracking control system resulted in stabilized fringe position to the 15 nm RMS level in the presence of laboratory ambient disturbances (10 um's RMS) which are a factor of 10 higher than those expected on orbit (1 um RMS). This control system rejects disturbances by a factor of 10,000 at low frequency.
* By similar tuning and redesign of the pointing control system, the present system suppresses pointing jitter to the 250 nrad RMS level. This new system rejects disturbances from dc to 100 Hz, with a factor of 1000 in the low frequency range. The results of this work were presented at the IEEE 4th Annual Conference on Control Applications in Albany, NY (September 27-28).
* The six-axis isolation system, which attenuates input disturbances from a shaker source, has been redesigned, implemented and tested. The new system utilizes the same approach with similar performance used previously; local, identical closed loops about each strut. However, this analog design is significantly simpler in implementation.
* The latest "layered" transfer functions on the MPI testbed, measured from the input disturbance source location (on top of the 6-axis isolation platform) to fringe detector output indicate attenuation levels on the order of 60 dB in the low frequency ranges and 20 dB in the higher frequency ranges. The two control layers in operation for these measurements are the active optics loops (pointing and pathlength control) and the active isolation loops.
* The first external metrology beam on the MPI testbed has been installed and tested. This system measures the relative distance between the center of the siderostat (collecting aperture) to a point out on the end of the optics boom.
* The performance of the coarse acquisition system, which is responsible for placing the star light from each arm of the interferometer on the fine pointing camera, has been significantly improved. Through many adjustments including: realignment and precise focusing of the coarse acquisition optics, the addition of light baffles, electrical isolation/proper grounding of the truss structure and analog and digital filtering, the coarse acquisition sensor signal-to-noise level has improved by a factor of 10. This significantly improved the reliability of the coarse acquisition system placing the stellar light on the camera.
* An optical demonstration system has been added to the testbed which functions as a diagnostic tool as well as a means to easily demonstrate testbed operation to visitors. The system transduces all the primary testbed sensor signals onto a wall display using high bandwidth scanning mirrors and multi-colored independent (from the testbed) lasers.
VIBRATION ISOLATION
* Starting early in the third quarter of this fiscal year the emphasis in the vibration isolation task shifted to support of the BMDO-sponsored STRV-2 (Space Technology Research Vehicle - 2) Program. One of the technology experiments to be flown on STRV-2 is the Vibration Isolation Suppression and Steering (VISS) experiment, a 6-axis actively controlled hexapod whose function it is to provide a stabilized platform for a midwave infrared (MWIR) telescope to be supplied by the British Defense Research Agency (DRA). NASA and BMDO agreed to collaborate on VISS, with BMDO funding Phillips Lab to procure (from Honeywell Space Systems) the VISS hardware and perform system integration, while NASA funds JPL CSI to supply the VISS control laws and flight software. Work performed over the last two quarters under this arrangement includes:
- Formed JPL STRV-2 VISS team of J. Spanos, Z. Rahman, W. Tsuha and R. Laskin in May 95
- Placed preliminary requirement on MWIR dynamics and attended MWIR PDR
- Identified basic functions of VISS flight software known as "mode commander" and communicated these to Phillips labs and Honeywell
- Defined control system architecture for the three principal control modes of the VISS (isolation, suppression, steering)
- Developed simple finite element model of the system using STEP-3 bus, MWIR mass properties as per DRA, VISS strut dynamics and voice coil electrical parameters as per Honeywell
- Developed dynamics simulation testbed in the Matlab Simulink environment to test and verify the performance of the VISS control system
- Delivered the 3-tiered control architecture and the Simulink model of the VISS compensator to Honeywell
- Supported the VISS PDR on Aug. 17 with two presentations describing the mathermatical model, conrol system design, analysis and simulation results
- Supported the VISS Software PDR at Honeywell on Sep. 27
ACTIVE STRUCTURES & MICRODYNAMICS
* Development of the MPI active member has been put on indefinite hold due to budget constraints. Work on the Microdynamic Component Tester has also been discontinued. The tester has been mothballed for potential future use.
PICOMETER METROLOGY
* Yekta Gursel began testing the absolute metrology gauge. By stabilizing the 1.3 um Nd:YAG laser to an external Fabry-Perot cavity, he has achieved an accuracy of 3 microns.This accuracy is below the OSI requirements.
* Yekta is reconfiguring the surface metrology gauge to make absolute optical surface measurements. This entails rotating the test optic with respect to the reference flat and separating the measured errors. The surface metrology gauge currently has a precision of less than lambda/30,000.
Flight Experiments
STELLAR INTERFEROMETER TRACKING EXPERIMENT (SITE)
* Since submittal of the SITE Phase B proposal to the IN-STEP program we have been pursuing activities which will best position us for implementing SITE, should it be selected. These activities include:
- formed team to flight qualify commercial and in-house designs for key interferometer technologies such as delay lines, fast steering mirrors, and laser metrology components.
- met with many members of 5x and 35x to formulate an approach for flight qualification of these Class D components.
- completed design of flight delay line and began fabrication.
- placed procurement for laser frequency shifter from New Focus Inc, and began optical test setup for the frequency shifter.
- procured two fast steering mirrors from Physik Instrumente and began test setup.
SIX AXIS SMART STRUT ISOLATION EXPERIMENT (SASSIE)
* Professor John McInroy from the University of Wyoming joined the SASSIE team to perform pointing experiments with the Proto-SASSIE hardware. The goal of the experiment is to point the Proto-SASSIE platform, which is mounted to the MPI testbed, at a pseudo star (laser) mounted to MPI's star simulator. The present incarnation of the pointing system reduces open loop pointing jitter from 52 urad's RMS to 4 urad's RMS in the presence of the lab ambient disturbances (rigid body motion, star motion,....).
* Awaiting word from the IN-STEP program on the fate of the SASSIE Phase B proposal.
Commercialization
* Completed the JPL multi-tone adaptive control experiments with the Ford active engine mount actuator, attenuating 5 harmonics and the 4 in-between half-harmonics by more than 20 dB
* Ford completed the first phase of automobile tests in Dearborn demonstrating 12 dB of vibration cancellation at the transmission mounting location
* Supported the 1995 TCA annual review on Aug. 30
Planned for the next period:
o Complete detailed planning and move out on FY'96 Interferometry Technology Program
o Deliver 1-axis control code to Honeywell and support STRV-2 VISS CDR
o Issue IMOS 1.0 User's Manual
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http://ranier.oact.hq.nasa.gov/Sensors_page/MpCSI/MpCSI3&4Q95.html