Bibliography Description Current TT Progress and Plans Goals Colin Eaton Undergraduate Senior SAWDRIP Intern Code 551 (Optics) Trans-Track (TT): – … is a 6-DOF object-transformation functionality in the Spatial Analyzer (SA) metrology software – …is currently used in real-time precision applications for assembly and collision avoidance – e.g. Mounting science instruments (SI) to payload structures – …uses Laser Trackers (LT) to record locations of various spherically mounted retroreflectors (SMR) attached to the moving object – One LT monitoring 3 SMRs completes 6-DOF, discrete TT system – Three networked LTs monitoring 3 SMRs provides real-time updates for 6-DOF TT – …utilizes watch windows to monitor relationships between corresponding source and target SMRs during assembly, and updates the net distances/angles to the destination position/orientation Trans-Track with Laser Tracker Laser Radar Applications – Monitor 6-DOF motion required to guide a moving object through a static environment – Both discrete and real-time – Adapt a warning mechanism feature to the software in order to alert the operator if objects are within a given tolerance and/or if the minimum clearance is violated – Audio and/or visual feedback – Develop a simplified mating assembly to demonstrate features that can be used in full-scale applications – e.g. An IATF-ISIM scenario on behalf of the JWST project – Utilize the Measurement Planning (MP) functionality of SA to help automate the processes Spherically Mounted Retroreflector (SMR) Networked Laser Trackers (LT) Houston, we have a problem with the tolerances. < 0.001” Acknowledgements: Mentors and *Lab Associates : Joseph Stock, SGT, Inc. Joseph Hayden, Sigma Space Corp. *Henry Sampler, NASA/GSFC *Phillip Anz-Meador, NASA/JSC *David Parker, Lockheed Martin Corp. Sponsors: NASA Goddard Space Flight Center Stinger Ghaffarian Technologies University of Michigan – Ann Arbor College of Engineering Michigan Space Grant Consortium – Explored the Interferometry (IFM) and Absolute Distance Meter (ADM) settings on the LT to establish advantages and disadvantages of each: – Successfully simulated discrete Trans-Track translation using 3 SMRs and one LT – Associated SMR locations with their base in SA – Observed discrete translation of target locations and base in SA using instrument updates – Near completion of audio and video feedback features with MPs – Scheduled time for access to all three GSFC LTs – Plan to perform real-time TT testing on (to be assembled) simplified IATF setup – Will present findings to Optics division for potential uses and feasibility for full-scale applications Base SMR Nests ADM Mode IFM Mode •Records absolute distances from a known coordinate system, and does not need initial reference measurement •Only capable of measuring relative positions and thus needs an initial reference measurement •Utilizes automatic target-locking feature when the line-of-sight between the LT and the SMR is compromised •Break of beam requires “homing” of SMR to known location •Internal integration times slightly delay measurements and introduce source of error when measuring moving objects •Near-immediate measurements induce no loss in accuracy in measurements of objects moving slower than ~3m/sec > Used for discrete TT applications > Used for real-time TT applications – Following the impressive results of the RSU scans, it was proposed that the LR be used to analyze the micro-meteorite impacts on the radiator of the Wide Field Planetary Camera 2 (WFPC2) – The LR was networked into the reference frame via scans of retro-targets and key features of the face plate – specifically the corners and two port hole centroids – Hi-resolution scans were performed on the two largest craters (numbered 13 and 14) – These scans proved to be beneficial in the analysis of the impacts, and may be considered as a viable alternative for similar applications in the future LR Trans-Track LR vs. PG – Photogrammetry (PG) is currently the primary method employed in optical metrology measurements under cryogenic conditions – PG is derived from photographic images and the PG camera system is tested and calibrated through the multi-layer windows of the cryogenic chambers (which induce Snell’s Law image distortions) – It has been suggested that the relatively new LR technology be adapted to take cryogenic measurements as a cross-check for PG – Research has been done to analyze the window distortion effects on LR measurements, and the results are promising – Current plans: – Determine the most robust method of centroiding the PG targets from LR scans – Characterize the LR returns on PG targets at different incidence angles – Compare relative accuracy between LR and PG on the same PG targets – Test the repeatability of LR measurements Hubble Ex-Flight Hardware Scans – On Hubble Servicing Mission 4 (SM4), the astronauts were unable to place one of the Rate Sensing Units (RSU) in its mounting plate – As per the request of Code 442 scientists, LR scans of the feet and pinholes on the bottom surface of two RSUs were taken (one that fit, and the one that didn’t fit) – Relative locations and other requirements were analyzed, and it was deduced that all dimensions were well within their respective tolerances (within ~30microns) – The RSU was transported to the Hi-Fidelity Hubble Mock-up at GSFC and was easily placed into its respective mounting plate – Original plans to utilize the laser radar (LR) included scanning the envelopes of objects in the system as an alternative/addition to simply translating the CAD models – An anomalous effect intrinsic to the LR was discovered in the process, where scans of flat surfaces yielded oscillatory patterns (nicknamed the “Metrology Genome Effect”) – This problem was resolved when the Decimation setting was returned to its default position (it is still unknown how/when this setting was manipulated) – Once the LR was fixed, it was realized that the tooling ball (TB) measurement feature of the LR could be used in place of the LT for discrete TT – Discrete TT with the LR has been successfully tested and compared to the LT method – Slightly longer delay between measurements – Equivalent accuracy Gyros WFPC2 Side view of the scan of a flat metallic surface. Horizontal scale is around 10mm, and vertical scale of oscillations ranged from 100-300 microns (0.1 - 0.3mm) PG targets are retro-reflective surfaces that reflect light very efficiently back to the light source LR surface scans of the bottom surface of the ex- flight RSU super- imposed onto the dimensioned CAD model Photograph of crater “big 13 .“ Hole diam. <2mm LR surface scan of crater 13 JWST: James Webb Space Telescope ISIM: Integrated Science Instrument Module IATF: ISIM Alignment Target Fixture