NASA Scientific and Technical Aerospace Reports

solution. The sensor responds properly during the oxygen-generating and oxygen- depleting phases. The use of these
microenvironments for in situ self-calibration is discussed to achieve functional integration as well as structural integration
of the microsensor system.
Author
Actuators; Biochemistry; Diagnosis; Dissolved Gases; Microinstrumentation; Oxygen
20040074258 Missouri Univ., Rolla, MO, USA
Flexible Microsensor Array for the Root Zone Monitoring of Porous Tube Plant Growth System
Sathyan, Sandeep; Kim, Chang-Soo; Porterfield, D. Marshall; Nagle, H. Troy; Brown, Christopher S.; 2004; 20 pp.; In
English
Contract(s)/Grant(s): NAG9-1423; 01-OBPR-01; No Copyright; Avail: CASI; A03, Hardcopy
Control of oxygen and water in the root zone is vital to support plant growth in the microgravity environment. The ability
to control these sometimes opposing parameters in the root zone is dependent upon the availability of sensors to detect these
elements and provide feedback for control systems. In the present study we demonstrate the feasibility of using microsensor
arrays on a flexible substrate for dissolved oxygen detection, and a 4-point impedance microprobe for surface wetness
detection on the surface of a porous tube (PT) nutrient delivery system. The oxygen microsensor reported surface oxygen
concentrations that correlated with the oxygen concentrations of the solution inside the PT when operated at positive pressures.
At negative pressures the microsensor shows convergence to zero saturation (2.2 micro mol/L) values due to inadequate water
film formation on porous tube surface. The 4-point microprobe is useful as a wetness detector as it provides a clear
differentiation between dry and wet surfaces. The unique features of the dissolved oxygen microsensor array and 4-point
microprobe include small and simple design, flexibility and multipoint sensing. The demonstrated technology is anticipated
to provide low cost, and highly reliable sensor feedback monitoring plant growth nutrient delivery system in both terrestrial
and microgravity environments.
Author
Oxygen; Measuring Instruments; Water; Drying; Feedback Control; Microinstrumentation; Moisture Content
20040074273 Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA, USA
Wavefront Sensing and Control Technology for Submillimeter and Far-Infrared Space Telescopes
Redding, Dave; New Concepts for Far-Infrared and Submillimeter Space Astronomy; April 2004, pp. 393-407; In English;
See also 20040074260; No Copyright; Avail: CASI; A03, Hardcopy
The NGST wavefront sensing and control system will be developed to TRL6 over the next few years, including testing
in a cryogenic vacuum environment with traceable hardware. Doing this in the far-infrared and submillimeter is probably
easier, as some aspects of the problem scale with wavelength, and the telescope is likely to have a more stable environment;
however, detectors may present small complications. Since this is a new system approach, it warrants a new look. For instance,
a large space telescope based on the DART membrane mirror design requires a new actuation approach. Other mirror and
actuation technologies may prove useful as well.
Author
Membranes; Mirrors; Submillimeter Waves
20040074275 NASA Goddard Space Flight Center, Greenbelt, MD, USA
The Wide-Field Imaging Interferometry Testbed: Progress and Plans
Rinehart, S. A.; Leisawitz, D.; Leviton, D.; Martino, A.; Maynard, W.; Mundy, L. G.; Zhang, X.; New Concepts for
Far-Infrared and Submillimeter Space Astronomy; April 2004, pp. 421-427; In English; See also 20040074260; No
Copyright; Avail: CASI; A02, Hardcopy
We describe the technique of wide field mosaic imaging for optical/IR interferometers and present early experimental
results from a laboratory instrument designed to validate, experiment with, and refine the technique. A conventional
single-detector stellar interferometer operating with narrow bandwidth at center wavelength lambda is limited in its field of
view to the primary beam of the individual telescope apertures, or approx. lambda/D(sub tel) radians, where is the telescope
diameter. Such a field is too small for many applications; often one wishes to image extended sources. We are developing and
testing a technique analogous to the mosaic method employed in millimeter and radio astronomy, but applicable to optical/IR
Michelson interferometers, in which beam combination is done in the pupil plane. An N(sub pix) x N(sub pix) detector array
placed in the image plane of the interferometer is used to record simultaneously the fringe patterns from many contiguous
telescope fields, effectively multiplying the field size by N(sub pix)/2, where the factor 2 allows for Nyquist sampling. This
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