Bittersweet
memories of orbiter and final countdown LMM
brings real-time imaging in space
LMM Status March 28, 2011 - Operations were successfully completed for the 6 samples sent up on ULF-5. PRESS RELEASE: NASA DEVELOPS LIGHT MICROSCOPE FOR INTERNATIONAL SPACE STATION February 2011 - The biological samples for the LMM launched
on space shuttle Discovery's STS-133 mission on Feb. 24.
They include eight fixed slides containing yeast; bacteria;
a leaf; a fly; a butterfly wing; tissue sections and blood;
six containers of live C. elegans worms, an organism biologists
commonly study; a typed letter "r" and a piece
of fluorescent plastic.
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Overview The Light Microscopy Module (LMM) is planned as a remotely controllable on-orbit microscope subrack facility, allowing flexible scheduling and control of physical science and biological science experiments within the GRC Fluids Integrated Rack (FIR) on the International Space Station. Within the FIR, an initial complement of four fluid physics experiments will utilize an instrument built around a lightmicroscope. These experiments are the "Constrained Vapor Bubble" experiment (Peter C. Wayner of Rensselaer Polytechnic Institute), the "Physics of Hard Spheres Experiment–2" (Paul M. Chaikin of Princeton University), the "Physics of Colloids in Space–2" experiment (David A. Weitz of Harvard University), and the "Low Volume Fraction Entropically Driven Colloidal Assembly" experiment (Arjun G. Yodh of the University of Pennsylvania). The first experiment investigates heat conductance in microgravity as a function of liquid volume and heat flow rate to determine, in detail, the transport process characteristics in a curved liquid film. The other three experiments investigate various complementary aspects of the nucleation, growth, structure, and properties of colloidal crystals in microgravity and theeffects of micromanipulation upon their properties. Key diagnostic capabilities include video microscopy to observe sample features including basic structures and dynamics, thin film interferometry, laser tweezers for colloidal particle manipulation and patterning, confocal microscopy to provide enhanced three-dimensional visualization of colloidal crystal structures, and spectrophotometry to measure colloidal crystal photonic properties. In addition to using the confocal system, biological experiments can conduct fluorescence imaging by using the fiber-coupled output of the Nd:YAG laser operating at 532-nm, the 437-nm line of a mercury arc, or appropriate narrow-band filtering of the FIR provided metal halide white light source.
The
LMM concept is a modified commercial research imaging light
microscope with powerful laser-diagnostic hardware and interfaces,
creating a one-of-a-kind, state ofthe-art microscopic research
facility. The microscope will house several different objectives,
corresponding to magnifications of 10´, 40´,
50´, 63´, and 100´. Features of the LMM
include high-resolution color video microscopy, brightfield,
darkfield, phase contrast, differential interference contrast
(DIC), spectrophotometry, and confocal microscopy combined
in a single configuration. Sample manipulation techniques
also integrated with the diagnostics are laser tweezers.
The LMM provides an enclosed workarea called the auxiliary
fluids container (AFC) with gloveports and an equipment transfer
module (ETM) for transporting experiment samples from stowage
to the LMM. The multiport imaging head on the top of the
microscope provides a motorized slider to select the sensor
or sensors to which the images are directed. The AFC is fastened
to the microscope body and is sealed to provide a clean working
space and one level of containment. Gloveports allow access
to the sample area for cleaning before opening the box and
experiment sample changeout or reconfiguration. The ETM can
be configured to support various experiment modules and is
located below the AFC which has a pass-through for the samples.
Materials are thus transferred without the risk of contamination
release. The ETM will be loaded with experiment modules on
the ground, and will provide contained storage until the
samples are utilized in the experiment. Laser tweezers will be implemented using a custom-built system based upon a 1064-nm Nd:YAG laser, beam-focusing optics, and two acousto-optic deflectors to steer the trap within the field of view of the microscope. Laser tweezers simply is the trapping of a colloidal particle using radiation pressure by focusing a laser beam through a high-numerical aperture lens and striking the particle. Laser tweezers will be used to measure the viscosity and viscoelasticity of the fluid. A particle will be trapped and oscillated at a fixed frequency. When this is done, the centroid of the trap and particle will not coincide; the difference in the two positions through the scan provides the driving force. Using that information along with the motion, both linear and nonlinear viscoelastic properties can be computed. Confocal Microscopy Confocal microscopy will be implemented
using a 532-nm frequency-doubled Nd:YAG laser, a confocal scanner,
and an 8-bit digital CCD camera. The scanner will allow 30
frames per second of confocal images to the CCD camera. The
crystal's three-dimensional structure is reconstructed by assembling
the slices with an image analysis program, from which colloidal
growth, structure, and dynamics can be measured. The confocal
module will be attached and aligned to the side of the LMM
and will access the sample through an auxiliary port on the
Leica RXA. The microscope’s reflected light turret will
contain a reflecting mirror to direct the light to and from
the sample.
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Project Management: Contacts at NASA Glenn Research Center |
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