Summer Internship Poster Presentation
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Transcript of Summer Internship Poster Presentation
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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