Technology Focus Electronics/Computers - NASA · 20 Production of Tuber-Inducing ... This document...

Technology Focus

Electronics/Computers

Software

Materials

Mechanics

Machinery/Automation

Manufacturing & Prototyping

Bio-Medical

Physical Sciences

Information Sciences

Books and Reports

04-06 April 2006

https://ntrs.nasa.gov/search.jsp?R=20100021326 2018-07-16T17:41:34+00:00Z

NASA Tech Briefs, April 2006 1

INTRODUCTIONTech Briefs are short announcements of innovations originating from research and develop-

ment activities of the National Aeronautics and Space Administration. They emphasizeinformation considered likely to be transferable across industrial, regional, or disciplinary linesand are issued to encourage commercial application.

Availability of NASA Tech Briefs and TSPsRequests for individual Tech Briefs or for Technical Support Packages (TSPs) announced herein shouldbe addressed to

National Technology Transfer CenterTelephone No. (800) 678-6882 or via World Wide Web at www2.nttc.edu/leads/

Please reference the control numbers appearing at the end of each Tech Brief. Information on NASA’s Innovative Partnerships Program (IPP), its documents, and services is also available at the same facility oron the World Wide Web at http://ipp.nasa.gov.

Innovative Partnerships Offices are located at NASA field centers to provide technology-transfer access toindustrial users. Inquiries can be made by contacting NASA field centers and Mission Directorates listed below.

Ames Research CenterLisa L. Lockyer(650) [email protected]

Dryden Flight Research CenterGregory Poteat(661) [email protected]

Goddard Space Flight CenterNona Cheeks(301) [email protected]

Jet Propulsion LaboratoryKen Wolfenbarger(818) [email protected]

Johnson Space CenterHelen Lane(713) [email protected]

Kennedy Space CenterJim Aliberti(321) [email protected]

Langley Research CenterRay P. Turcotte(757) [email protected]

John H. Glenn Research Center atLewis FieldRobert Lawrence(216) [email protected]

Marshall Space Flight CenterVernotto McMillan(256) [email protected]

Stennis Space CenterJohn Bailey(228) 688-1660 [email protected]

Carl RaySmall Business Innovation Research Program (SBIR) &Small Business TechnologyTransfer Program (STTR)(202) [email protected]

Frank SchowengerdtInnovative Partnerships Program(Code TD)(202) [email protected]

John MankinsExploration Systems Researchand Technology Division(202) [email protected]

Terry HertzAeronautics and Space MissionDirectorate(202) [email protected]

Glen MucklowMission and Systems Management Division (SMD)(202) [email protected]

Granville PaulesMission and Systems Management Division (SMD)(202) [email protected]

Gene TrinhHuman Systems Research andTechnology Division (ESMD)(202) [email protected]

John RushSpace Communications Office(SOMD)(202) [email protected]

NASA Field Centers and Program Offices

NNAASSAA MMiissssiioonn DDiirreeccttoorraatteess

At NASA Headquarters there are four Mission Directorates underwhich there are seven major program offices that develop andoversee technology projects of potential interest to industry:

5 Technology Focus: Sensors

5 Replaceable Sensor System for BioreactorMonitoring

5 Unitary Shaft-Angle and Shaft-Speed SensorAssemblies

6 Arrays of Nano Tunnel Junctions as InfraredImage Sensors

7 Catalytic-Metal/PdOx /SiC Schottky-Diode GasSensors

8 Compact, Precise Inertial Rotation Sensors forSpacecraft

9 Electronics/Computers

9 Universal Controller for Spacecraft Mechanisms

9 The Flostation — an Immersive CyberspaceSystem

10 Algorithm for Aligning an Array of ReceivingRadio Antennas

11 Single-Chip T/R Module for 1.2 GHz

13 Software

13 Quantum Entanglement Molecular AbsorptionSpectrum Simulator

13 FuzzObserver

13 Internet Distribution of Spacecraft Telemetry Data

13 Semi-Automated Identification of Rocks inImages

14 Pattern-Recognition Algorithm for Locking Laser Frequency

15 Materials

15 Designing Cure Cycles for Matrix/Fiber Composite Parts

17 Machinery/Automation

17 Controlling Herds of Cooperative Robots

17 Modification of a Limbed Robot to FavorClimbing

19 Bio-Medical

19 Vacuum-Assisted, Constant-Force Exercise Device

20 Production of Tuber-Inducing Factor

21 Physical Sciences

21 Quantum-Dot Laser for Wavelengths of 1.8 to2.3 µm

21 Tunable Filter Made From Three Coupled WGMResonators

22 Dynamic Pupil Masking for Phasing TelescopeMirror Segments

04-06 April 2006


This document was prepared under the sponsorship of the National Aeronautics and Space Administration. Neither the United States Govern-ment nor any person acting on behalf of the United States Government assumes any liability resulting from the use of the information containedin this document, or warrants that such use will be free from privately owned rights.


Technology Focus: Sensors

The figure depicts a unit that containsa rotary-position or a rotary-speed sen-sor, plus electronic circuitry necessaryfor its operation, all enclosed in a singlehousing with a shaft for coupling to anexternal rotary machine. This rotation-

sensor unit is complete: when its shaft ismechanically connected to that of therotary machine and it is supplied withelectric power, it generates an outputsignal directly indicative of the rotaryposition or speed, without need for addi-

tional processing by other circuitry. Theincorporation of all of the necessary ex-citatory and readout circuitry into thehousing (in contradistinction to usingexternally located excitatory and/orreadout circuitry) in a compact arrange-

Unitary Shaft-Angle and Shaft-Speed Sensor AssembliesAll necessary mechanical and electronic components are packaged together in compact units. Marshall Space Flight Center, Alabama

A sensor system was proposed thatwould monitor spaceflight bioreactorparameters. Not only will this technol-ogy be invaluable in the space programfor which it was developed, it will findapplications in medical science and in-dustrial laboratories as well.

Using frequency-domain-based fluo-rescence lifetime technology, the sensorsystem will be able to detect changes influorescence lifetime quenching that re-sults from displacement of fluorophore-labeled receptors bound to target lig-ands. This device will be used to monitorand regulate bioreactor parameters in-cluding glucose, pH, oxygen pressure(pO2), and carbon dioxide pressure(pCO2). Moreover, these biosensor fluo-rophore receptor-quenching complexescan be designed to further detect andmonitor for potential biohazards, bio-products, or bioimpurities.

Biosensors used to detect biologicalfluid constituents have already been devel-oped that employ a number of strategies,including invasive microelectrodes (e.g.,dark electrodes), optical techniques in-cluding fluorescence, and membrane per-meable systems based on osmotic pressure.Yet the longevity of any of these sensorsdoes not meet the demands of extendeduse in spacecraft habitat or bioreactormonitoring. It was therefore necessary todevelop a sensor platform that could deter-mine not only fluid variables such as glu-cose concentration, pO2, pCO2, and pHbut can also regulate these fluid variableswith controlled feedback loop.

To accommodate the inevitable failureof sensing elements, a biosensor arraymust be noninvasive and interchangeable— something missing in the current stateof the art. Robust, compact, in-situbiosensor arrays that are easy to use andself-contained are needed for the on-board testing and monitoring of bioreac-tor parameters. In a miniaturized fre-quency-domain lifetime fluorescence(fLF) system, sensor arrays can be inte-grated into a “dead leg” where the de-sired assays of bioreactor constituents canbe analyzed and results can be sent to afeedback control of regulatory valves thatwill release nutrients and maintain a con-stant bioenvironment for cell or tissueculture growth.

The sensor array and dead-leg test so-lution must be designed so that they areinterchangeable for the inevitable re-quirement of sensor replacement. Thisdesign will take into account sterilizationconsiderations as well as the ease withwhich a part can be replaced in order tominimize the use of astronaut time. Thedead leg will allow a small volume of sam-ple to be directed over the fLF sensorsurface in order to collect multicompo-nent emissions and analyze them for dif-ferent constituents. The biosensor sys-tem will also contain feedback controlsto the feed lines of the bioreactor, thusproviding autonomous operation.

The final fLF sensor system will containa fully optimized sensor array that can beinterfaced with the dead leg of a bioreac-tor or bioenvironment where current fLF

analysis can be performed repeatedly andthen replaced when sensor failure occurs.The fLF has a proven track record and thesmall dimensions needed to accommo-date removable and interchangeable in-terfacings with the bioreactor/bioenvi-ronment. Scientists believe that an evensmaller dimension system can be devel-oped for interfacing directly with thebioreactor. This sensor platform, whichwill be built around this dead-leg sampleanalysis segment, will be used for preflighttesting/evaluation as a solution to biore-actor environment control and will alsobe marketed in a development programfor use in bioreactor control in the bio-pharmaceutical and medical industries.

The development of this multi-analytebiosensor system has broad commercialapplications in the biopharmaceutical in-dustry where genetically engineered drugsare produced by bioreactors. In additionto its use for bioreactor monitoring, thisfLF biosensor technology will be useful forbiosensor applications including detec-tion of toxins, dangerous chemicals, andhazardous environmental agents. In addi-tion to monitoring bioreactor parametersduring long spaceflights of the future, thissystem can be used to monitor for biohaz-ards to ensure astronaut safety.

This work was done by Mike Mayo, SteveSavoy, and John Bruno of Systems &Processes Engineering Corporation for John-son Space Center. For further information,contact the Johnson Technology Transfer Of-fice at (281) 483-3809.MSC-23032.

Replaceable Sensor System for Bioreactor MonitoringAn instrument is capable of detecting and monitoring biological media constituents in aspaceflight bioreactor.Lyndon B. Johnson Space Center, Houston, Texas

6 NASA Tech Briefs, April 2006

Infrared image sensors based on high-density rectangular planar arrays of nanotunnel junctions have been proposed.These sensors would differ fundamentallyfrom prior infrared sensors based, vari-ously, on bolometry or conventional semi-conductor photodetection.

Infrared image sensors based on con-ventional semiconductor photodetec-tion must typically be cooled to cryo-genic temperatures to reduce noise toacceptably low levels. Some bolometer-type infrared sensors can be operatedat room temperature, but they exhibitlow detectivities and long response

times, which limit their utility. The pro-posed infrared image sensors could beoperated at room temperature withoutincurring excessive noise, and wouldexhibit high detectivities and short re-sponse times. Other advantages wouldinclude low power demand, high reso-lution, and tailorability of spectral re-sponse.

Neither bolometers nor conventionalsemiconductor photodetectors, the basicdetector units as proposed would partlyresemble rectennas. Nanometer-scaletunnel junctions would be created bycrossing of nanowires with quantum-me-

chanical-barrier layers in the form of thinlayers of electrically insulating materialbetween them (see figure). A micro-scopic dipole antenna sized and shapedto respond maximally in the infraredwavelength range that one seeks to detectwould be formed integrally with thenanowires at each junction. An incidentsignal in that wavelength range would be-come coupled into the antenna and,through the antenna, to the junction. Atthe junction, the flow of electrons be-tween the crossing wires would be domi-nated by quantum-mechanical tunnelingrather than thermionic emission. Rela-

Arrays of Nano Tunnel Junctions as Infrared Image SensorsHigh detectivity and rapid response would be attainable at room temperature.NASA’s Jet Propulsion Laboratory, Pasadena, California

ment is the major difference betweenthis unit and prior rotation-sensor units.

The sensor assembly inside the hous-ing includes excitatory and readout in-tegrated circuits mounted on a circularprinted-circuit board. In a typical casein which the angle or speed trans-ducer(s) utilize electromagnetic induc-tion, the assembly also includes an-other circular printed-circuit board onwhich the transducer windings aremounted. A sheet of high-magnetic-permeability metal (“mu metal”) isplaced between the winding board and

the electronic-circuit board to preventspurious coupling of excitatory signalsfrom the transducer windings to thereadout circuits.

The housing and most of the othermechanical hardware can be commonto a variety of different sensor designs.Hence, the unit can be configured togenerate any of variety of outputs bychanging the interior sensor assembly.For example, the sensor assemblycould contain an analog tachometercircuit that generates an output pro-portional (in both magnitude and

sign or in magnitude only) to thespeed of rotation.

This work was done by Dean C. Alhorn,David E. Howard, and Dennis A. Smith ofMarshall Space Flight Center. Further in-formation is contained in a TSP (see page 1).

This invention has been patented byNASA (U.S. Patent No. 6,313,624). In-quiries concerning nonexclusive or exclusivelicense for its commercial developmentshould be addressed to Sammy Nabors,MSFC Commercialization Assistance Lead,at [email protected]. Refer toMFS-31238.

Transducers and Readout Electronic Circuits are parts of a sensor assembly contained in a single housing.

Windings

Shaft

ElectronicCircuits


Metal 2

Metal 1

A A

Thin Dielectric(Barrier) Layer

Si Substrate

Dielectric(e.g., SiO2)

Metal 2

Metal 1

SECTION A-A

Thin Dielectric(Barrier) Layer

TunnelJunctions

NPO-42587ABPI

11-2-05 es

Crossed Nanowires with dielectric barriers between them would constitute quantum-mechanical-tunneling junctions that could be used to detect infraredradiation. This device would be fabricated by a process including electron-beam lithography, deposition of metal, and etching. For simplicity, antennas thatwould be formed integrally with the nanowires are omitted.

tive to thermionic emission, quantum-mechanical tunneling is a fast process. Asdescribed below, the quantum-mechani-cal tunneling would be exploited to rec-tify the infrared-frequency alternating sig-nal delivered to the junction from theantenna.

Each nanojunction would be asym-metrical in that the crossing nanowireswould be made of two different materi-als: for example, two different metals, ametal and semiconductor, or the samesemiconductor doped at two differentlevels. The resulting asymmetry andnonlinearity of the tunneling current asa function of voltage across the junctioncould be exploited to effect rectificationof the signal. Because the asymmetry

would be present even in the absence ofbias, the device could be operated at lowor zero bias and, therefore, would de-mand very little power.

Other advantages of the proposed sen-sors would include the following:• High spatial resolution would be achieved

by virtue of the density of nanowires and,consequently, of nanojunctions.

• The barriers are expected to keep darkcurrents very small, leading to high signal-to-noise ratios.

• Different nanojunctions within thesame sensor could be fabricated with an-tennas tailored for different wave-lengths, enabling multispectral imaging.This work was done by Kyung-Ah Son of

Caltech; Jeong S. Moon of HRL, LLC; and

Nicholas Prokopuk of Naval Air Warfare Cen-ter for NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1).

In accordance with Public Law 96-517, thecontractor has elected to retain title to this inven-tion. Inquiries concerning rights for its commer-cial use should be addressed to:

Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099(818) 354-2240E-mail: [email protected] to NPO-42587, volume and number of

this NASA Tech Briefs issue, and the pagenumber.

Miniaturized hydrogen- and hydrocar-bon-gas sensors, heretofore often con-sisting of Schottky diodes based on cat-alytic metal in contact with SiC, can beimproved by incorporating palladiumoxide (PdOx, where 0≤x≤1) between thecatalytic metal and the SiC.

In prior such sensors in which the cat-alytic metal was the alloy PdCr, diffusionand the consequent formation of oxidesand silicides of Pd and Cr during opera-tion at high temperature were observedto cause loss of sensitivity. However, itwas also observed that any PdOx layersthat formed and remained at PdCr/SiCinterfaces acted as barriers to diffusion,preventing further deterioration by pre-venting the subsequent formation ofmetal silicides.

In the present improvement, the les-son learned from these observations is

applied by placing PdOx at the catalytic-metal/SiC interfaces in a controlled anduniform manner to form stable diffusionbarriers that prevent formation of metalsilicides. A major advantage of PdOx

over other candidate diffusion-barriermaterials is that PdOx is a highly stableoxide that can be incorporated into gas-sensor structures by use of depositiontechniques that are standard in the semi-conductor industry.

The PdOx layer can be used in a gassensor structure for improved sensor sta-bility, while maintaining sensitivity. Forexample, in proof-of-concept experi-ments, Pt/PdOx/SiC Schottky-diode gassensors were fabricated and tested. Thefabrication process included controlledsputter deposition of PdOx to a thicknessof ≈50 Å on a 400-µm-thick SiC sub-strate, followed by deposition of Pt to a

thickness of ≈450 Å on the PdOx. TheSiC substrate (400 microns in thickness)was patterned with photoresist and aSchottky-diode photomask. A lift-offprocess completed the definition of theSchottky-diode pattern.

The sensors were tested by measuringchanges in forward currents at a bias po-tential of 1 V during exposure to H2 inN2 at temperatures ranging from 450 to600 °C for more than 750 hours. Thesensors were found to be stable after abreak-in time of nearly 200 hours. Thesensors exhibited high sensitivity: sensorcurrents changed by factors rangingfrom 300 to 800 when the gas waschanged from pure N2 to 0.5 percent H2

in N2. The high sensitivity and stability ofthese Pt/PdOx/SiC sensors were foundto represent a marked improvementover comparable Pt/SiC sensors. More-

Catalytic-Metal/PdOx/SiC Schottky-Diode Gas Sensors PdOx layers inhibit the undesired formation of metal silicides. John H. Glenn Research Center, Cleveland, Ohio


over, surface analysis showed that therewas no significant formation of silicidesin the Pt/PdOx/SiC sensors.

This work was done by Gary W. Hunterand Jennifer C. Xu of Glenn Research

Center and Dorothy Lukco of QSS Group,Inc. Further information is contained in aTSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressed

to NASA Glenn Research Center, InnovativePartnerships Office, Attn: Steve Fedor, MailStop 4–8, 21000 Brookpark Road, Cleve-land, Ohio 44135. Refer to LEW-17859-1.

A document describes a concept foran inertial sensor for measuring the ro-tation of an inertially stable spacecraftaround its center of gravity to within100 microarcseconds or possibly evenhigher precision. Whereas a currentproposal for a spacecraft-rotation sen-sor of this accuracy requires one space-craft dimension on the order of ten me-ters, a sensor according to this proposalcould fit within a package smaller than1 meter and would have less than atenth of the mass. According to the

concept, an inertial mass and an appa-ratus for monitoring the mass would beplaced at some known distance fromthe center of gravity so that any rotationof the spacecraft would cause relativemotion between the mass and thespacecraft. The relative motion wouldbe measured and, once the displace-ment of the mass exceeded a pre-scribed range, a precisely monitoredrestoring force would be applied to re-turn the mass to a predetermined posi-tion. Measurements of the relative mo-

tion and restoring force would provideinformation on changes in the attitudeof the spacecraft. A history of relative-motion and restoring-force measure-ments could be kept, enabling determi-nation of the cumulative change inattitude during the observation time.

This work was done by David Rosing, Jef-frey Oseas, and Robert Korechoff of Caltechfor NASA’s Jet Propulsion Laboratory.Further information is contained in a TSP(see page 1).NPO-41926

Compact, Precise Inertial Rotation Sensors for SpacecraftNASA’s Jet Propulsion Laboratory, Pasadena, California


An electronic control unit has beenfabricated and tested that can be repli-cated as a universal interface betweenthe electronic infrastructure of aspacecraft and a brushless-motor (orother electromechanical actuator)driven mechanism that performs a spe-cific mechanical function within theoverall spacecraft system. The unit in-cludes interfaces to a variety of space-craft sensors, power outputs, and hasselectable actuator control parametersmaking the assembly a mechanismcontroller. Several control topologiesare selectable and reconfigurable atany time. This allows the same actuatorto perform different functions duringthe mission life of the spacecraft. Theunit includes complementary metaloxide/semiconductor electronic com-ponents on a circuit board of a typecalled “rigid flex” (signifying flexibleprinted wiring along with a rigid sub-

strate). The rigid flex board is foldedto make the unit fit into a housing onthe back of a motor. The assembly hasredundant critical interfaces, allowingthe controller to perform time-criticaloperations when no human interfacewith the hardware is possible. The con-troller is designed to function over awide temperature range without theneed for thermal control, includingwithstanding significant thermal cy-cling, making it usable in nearly all en-vironments that spacecraft or landerswill endure. A prototype has withstood1,500 thermal cycles between –120 and+85 °C without significant deteriora-tion of its packaging or electronicfunction. Because there is no need forthermal control and the unit is ad-dressed through a serial bus interface,the cabling and other system hardwareare substantially reduced in quantityand complexity, with corresponding

reductions in overall spacecraft massand cost.

This work was done by Greg Levanas,Thomas McCarthy, Don Hunter, ChristineBuchanan, Michael Johnson, RaymondCozy, Albert Morgan, and Hung Tran ofCaltech for NASA’s Jet Propulsion Labo-ratory. Further information is contained ina TSP (see page 1).

In accordance with Public Law 96-517,the contractor has elected to retain title to thisinvention. Inquiries concerning rights for itscommercial use should be addressed to:

Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099(818) 354-2240E-mail: [email protected] to NPO-41776, volume and number

of this NASA Tech Briefs issue, and thepage number.

Electronics/Computers

Universal Controller for Spacecraft MechanismsThe controller interfaces to spacecraft sensors and power.NASA’s Jet Propulsion Laboratory, Pasadena, California

A flostation is a computer-controlledapparatus that, along with one or morecomputer(s) and other computer-con-trolled equipment, is part of an immer-sive cyberspace system. The system issaid to be “immersive” in two senses ofthe word: (1) It supports the body in amodified form neutral posture experi-enced in zero gravity and (2) it isequipped with computer-controlled dis-play equipment that helps to give the oc-cupant of the chair a feeling of immer-sion in an environment that the system isdesigned to simulate.

Neutral immersion was conceived dur-ing the Gemini program as a means oftraining astronauts for working in a zero-gravity environment. Current derivativesinclude neutral-buoyancy tanks and theKC-135 airplane, each of which mimicsthe effects of zero gravity. While thesehave performed well in simulating the

shorter-duration flights typical of thespace program to date, a training devicethat can take astronauts to the next levelwill be needed for simulating longer-du-ration flights such as that of the Interna-tional Space Station. The flostation is ex-pected to satisfy this need. The flostationcould also be adapted and replicated foruse in commercial ventures rangingfrom home entertainment to medicaltreatment.

The use of neutral immersion in theflostation enables the occupant to re-cline in an optimal posture of rest andmeditation. This posture, combinessavasana (known to practitioners ofyoga) and a modified form of the neu-tral posture assumed by astronauts inouter space. As the occupant relaxes,awareness of the physical body is re-duced. The neutral body posture, whichcan be maintained for hours without dis-

comfort, is extended to the eyes, ears,and hands. The occupant can be sur-rounded with a full-field-of-view visualdisplay and “nearphone” sound, and canbe stimulated with full-body vibrationand motion cueing. Once fully im-mersed, the occupant can use neutralhand controllers (that is, hand-posturesensors) to control various aspects of thesimulated environment.

A logical extension of the basic flosta-tion concept is the concept of a floroom— a system of multiple flostations thatcan be used by multiple occupants work-ing either by themselves or interactionwith each other. As the use of flostationsspreads, the immersive cyberspace envi-ronments that they create will likely ap-peal to a vast audience. Indeed, the in-ventor of the flostation foresees a daywhen floors will be installed in venues asdiverse as hotels, museums, airports, and

The Flostation — an Immersive Cyberspace SystemNeutral buoyancy is exploited along with advanced computer-generated displays.Lyndon B. Johnson Space Center, Houston, Texas


theme parks — a far cry from the utili-tarian scope of neutral immersion asconceived in the early days of space-flight. Florooms would enable users toshare experiences on a large scale — forexample, immersive rock concerts orsporting events. A floroom could con-tain hundreds of flostations.

At present, the flostation is availablein two versions. One is a static version,which includes the chair portion (theflochair) equipped with a hemisphericalscreen (the flodome) that is loweredover the occupant’s head so the occu-pant’s eyes are at the center of the dome

and the field of view is filled by an imagegenerated on a standard liquid-crystal-display projector. The static version alsoincludes shakers and loudspeakersmounted on a simple motorized reclin-ing base. The other version is a dynamicone in that the flochair is mounted on asix-degree-of-freedom hydraulic base.The static version is intended for publicand home use; the dynamic version isbetter suited to the space program.

Flostations could prove beneficial inapplications beyond the space programfor which they were originally devel-oped. For example, they might be used

in medicine for pain-reduction therapyor to treat psychoses.

This work was done by Brian Park of Flo-giston Corp. for Johnson Space Center.


Flogiston Corp. 16921 Crystal Cave DriveAustin, TX 78737Refer to MSC-22932, volume and number


A digital-signal-processing algorithm(somewhat arbitrarily) called “SUMPLE”has been devised as a means of aligningthe outputs of multiple receiving radio an-tennas in a large array for the purpose ofreceiving a weak signal transmitted by asingle distant source. As used here, “align-ing” signifies adjusting the delays andphases of the outputs from the various an-tennas so that their relatively weak repli-cas of the desired signal can be added co-herently to increase the signal-to-noiseratio (SNR) for improved reception, asthough one had a single larger antenna.The method was devised to enhancespacecraft-tracking and telemetry opera-tions in NASA’s Deep Space Network(DSN); the method could also be usefulin such other applications as both satelliteand terrestrial radio communications andradio astronomy.

Heretofore, most commonly, align-ment has been effected by a process thatinvolves correlation of signals in pairs.This approach necessitates the use of alarge amount of hardware most no-tably, the N(N - 1)/2 correlators neededto process signals from all possible pairsof N antennas. Moreover, because theincoming signals typically have lowSNRs, the delay and phase adjustmentsare poorly determined from the pair-wise correlations.

SUMPLE also involves correlations,but the correlations are not performedin pairs. Instead, in a partly iterativeprocess, each signal is appropriatelyweighted and then correlated with acomposite signal equal to the sum of theother signals (see Figure 1). One benefit

of this approach is that only N correla-

tors are needed; in an array of N>>1 an-tennas, this results in a significant reduc-tion of the amount of hardware.Another benefit is that once the arrayachieves coherence, the correlation SNRis N - 1 times that of a pair of antennas.

Two questions about the performanceof SUMPLE have been investigated bycomputational simulation. The first ques-tion is that of how SUMPLE performs atthe beginning of a signal-processing pass,before coherence is achieved among theantennas. The second is a question of

phase wandering: In some other methods

of correlation, one antenna is designatedthe reference antenna and all the otherantennas are brought into alignmentwith it. However, in SUMPLE, all the an-tennas are aligned to what amounts to a“floating” reference. There is concern asto whether the phase of the floating refer-ence wanders as a function of time, intro-ducing unknown phase instability.

In one simulation, the combining lossas a function of time (equivalently, as afunction of the number of iterations)was computed for a 100-antenna array by

Figure 1. SUMPLE is a digital-signal-processing algorithm in which the signal received by each antennain an array is correlated with the sum of all the other signals.

Algorithm for Aligning an Array of Receiving Radio AntennasRelative to prior such algorithms, this one requires less hardware.NASA’s Jet Propulsion Laboratory, Pasadena, California

Combine

Reference

ArrayOutput

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Weight&

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use of SUMPLE. At the beginning of thesimulated reception process, the signalphases were taken to be random, result-ing in a very large combining loss. The

combining loss was found to decrease toa few tenths of a decibel in about eightiterations and to remain at this levelthereafter (see Figure 2). Simulations of

many different array configurationsyielded essentially the same results.

Answering the question of phase wan-dering, the simulations did, indeed, showslow phase variations of a few degreesover time intervals of 10 to 20 iterations.However, it was found that this wanderingcould be prevented by forcing, to zero,the total phase correction obtained bysumming the individual corrections overall the antennas. Inasmuch as the phasecorrections are meant to bring the an-tenna signals into alignment with eachother, forcing the total phase correctionto zero does not pose an obstacle to theachievement of array coherence.

SUMPLE has been tested on an arrayof 34-m-diameter antennas in the DSN.The results of this test have been foundto agree with those of the simulations.

This work was done by David Rogstad ofCaltech for NASA’s Jet Propulsion Labo-ratory. Further information is contained ina TSP (see page 1).

The software used in this innovation is availablefor commercial licensing. Please contact KarinaEdmonds of the California Institute of Technologyat (818) 393-2827. Refer to NPO-40574.


Figure 2. The Combining Loss of a 100-antenna array using SUMPLE was simulated for reception of arepresentative telemetry signal. The unit of time on the abscissa is an iteration period defined, for thepurpose of this specific example, as an integration time of 5,000 telemetry-symbol periods.

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Single-Chip T/R Module for 1.2 GHzT/R modules can be made smaller and at lower cost.NASA’s Jet Propulsion Laboratory, Pasadena, California

A single-chip CMOS-based (comple-mentary-metal-oxide-semiconductor-based) transmit/receive (T/R) module isbeing developed for L-band radar sys-tems. Previous T/R module implementa-tions required multiple chips employingdifferent technologies (GaAs, Si, and oth-ers) combined with off-chip transmissionlines and discrete components includingcirculators. The new design eliminatesthe bulky circulator, significantly reduc-ing the size and mass of the T/R module.

Compared to multi-chip designs, the sin-gle-chip CMOS can be implemented withlower cost. These innovations enablecost-effective realization of advancedphased array and synthetic apertureradar systems that require integration ofthousands of T/R modules.

The circulator is a ferromagnetic devicethat directs the flow of the RF (radio fre-quency) power during transmission andreception. During transmission, the circu-lator delivers the transmitted power from

the amplifier to the antenna, while pre-venting it from damaging the sensitive re-ceiver circuitry. During reception, the cir-culator directs the energy from theantenna to the low-noise amplifier (LNA)while isolating the output of the poweramplifier (PA). In principle, a circulatorcould be replaced by series transistors act-ing as electronic switches. However, inpractice, the integration of conventionalseries transistors into a T/R chip intro-duces significant losses and noise.

The prototype single-chip T/R mod-ule contains integrated transistorswitches, but not connected in series; in-stead, they are connected in a shunt con-figuration with resonant circuits (see fig-ure). The shunt/resonant circuittopology not only reduces the losses as-sociated with conventional semiconduc-tor switches but also provides beneficialtransformation of impedances for thePA and the LNA. It provides full single-pole/double-throw switching for the an-tenna, isolating the LNA from the trans-mitted signal and isolating the PA fromthe received signal. During reception,

50-Ω Antenna10 Ω 800 Ω

L1 L2LNAPA

S1

S2

S3C1 C2 C3

RX/TX

NPO40869ABPI

3-24-04 bs

A 1.2-GHz Single-Chip T/R Circuit for a radar system eliminates a bulky circulator.


the voltage on control line RX/TX is high, causing the field-effect transistor(FET) switch S1 to be closed, forming aparallel resonant tank circuit L1||C1.This circuit presents high impedance tothe left of the antenna, so that the re-ceived signal is coupled to the LNA. Atthe same time, FET switches S2 and S3are open, so that C2 is removed from thecircuit (except for a small parasitic ca-pacitance). The combination of L2 andC3 forms a matching network that trans-forms the antenna impedance of 50ohms to a higher value from the per-spective of the LNA input terminal. Thistransformation of impedance improvesLNA noise figure by increasing the re-ceived voltage delivered to the inputtransistor. This allows lower transcon-ductance and therefore a smaller transis-tor, which makes it possible to design the

CMOS LNA for low power consumption.During transmission, the voltage on con-trol line RX/TX is low, causingswitch S1 to be open. In this configura-tion, the combination of L1 and C1transforms the antenna impedance to alower value from the perspective of thePA. This low impedance is helpful inproducing a relatively high outputpower compatible with the low CMOSoperating potential. At the same time,switches S2 and S3 are closed, formingthe parallel resonant tank circuit L2||C2.This circuit presents high impedance tothe right of the antenna, directing thePA output signal to the antenna andaway from the LNA. During this time, S3presents a short circuit across the LNAinput terminals to guarantee that thevoltage seen by the LNA is small enoughto prevent damage.

This work was done by Alina Moussessian,Mohammad Mojarradi, Travis Johnson, JohnDavis, Edwin Grigorian, James Hoffman, andEdward Caro of Caltech; and William Kuhn ofKansas State University for NASA’s JetPropulsion Laboratory. Further informa-tion is contained in a TSP (see page 1).





Software

Quantum EntanglementMolecular Absorption Spectrum Simulator

Quantum Entanglement Molecular Ab-sorption Spectrum Simulator (QE-MASS)is a computer program for simulating two-photon molecular-absorption spec-troscopy using quantum-entangled pho-tons. More specifically, QE-MASSsimulates the molecular absorption of twoquantum-entangled photons generated bythe spontaneous parametric down-conver-sion (SPDC) of a fixed-frequency photonfrom a laser. The two-photon absorptionprocess is modeled via a combination ofrovibrational and electronic single-photontransitions, using a wave-function formal-ism. A two-photon absorption cross sec-tion as a function of the entanglementdelay time between the two photons iscomputed, then subjected to a fast Fouriertransform to produce an energy spectrum.The program then detects peaks in theFourier spectrum and displays the energylevels of very short-lived intermediatequantum states (or virtual states) of themolecule. Such virtual states were onlypreviously accessible using ultra-fast (fem-tosecond) laser systems. However, with theuse of a single-frequency continuous wavelaser to produce SPDC photons, and QE-MASS program, these short-lived molecu-lar states can now be studied using muchsimpler laser systems. QE-MASS can alsoshow the dependence of the Fourier spec-trum on the tuning range of the entangle-ment time of any externally introducedoptical-path delay time. QE-MASS can beextended to any molecule for which anappropriate spectroscopic database isavailable. It is a means of performing an apriori parametric analysis of entangled-photon spectroscopy for developmentand implementation of emergingquantum-spectroscopic sensing tech-niques. QE-MASS is currently imple-mented using the Mathcad® softwarepackage.

This program was written by Quang-VietNguyen of Glenn Research Center andJun Kojima of the National Academy of Sci-ences. Further information is contained in aTSP (see page 1).

Inquiries concerning rights for the commer-cial use of this invention should be addressedto NASA Glenn Research Center, InnovativePartnerships Office, Attn: Steve Fedor, MailStop 4–8, 21000 Brookpark Road, Cleve-land, Ohio 44135. Refer to LEW-17830-1.

FuzzObserverFuzzy Feature Observation Planner

for Small Body Proximity Observations(FuzzObserver) is a developmental com-puter program, to be used along withother software, for autonomous plan-ning of maneuvers of a spacecraft nearan asteroid, comet, or other small astro-nomical body. Selection of terrain fea-tures and estimation of the position ofthe spacecraft relative to these features isan essential part of such planning. Fuz-zObserver contributes to the selectionand estimation by generating recom-mendations for spacecraft trajectory ad-justments to maintain the spacecraft’sability to observe sufficient terrain fea-tures for estimating position. The inputto FuzzObserver consists of data fromterrain images, including sets of data onfeatures acquired during descent to-ward, or traversal of, a body of interest.The name of this program reflects its useof fuzzy logic to reason about the terrainfeatures represented by the data and ex-tract corresponding trajectory-adjust-ment rules. Linguistic fuzzy sets and con-ditional statements enable fuzzy systemsto make decisions based on heuristicrule-based knowledge derived by engi-neering experts. A major advantage ofusing fuzzy logic is that it involves simplearithmetic calculations that can be per-formed rapidly enough to be useful forplanning within the short times typicallyavailable for spacecraft maneuvers.

This program was written by AyannaHoward and David Bayard of Caltech forNASA’s Jet Propulsion Laboratory. Fur-ther information is contained in a TSP (seepage 1).

This software is available for commerciallicensing. Please contact Karina Edmonds ofthe California Institute of Technology at(818) 393-2827. Refer to NPO-41290.

Internet Distribution ofSpacecraft Telemetry Data

Remote Access Multi-mission Process-ing and Analysis Ground Environment(RAMPAGE) is a Java-language servercomputer program that enables near-real-time display of spacecraft telemetrydata on any authorized client computerthat has access to the Internet and isequipped with Web-browser software. Inaddition to providing a variety of dis-

plays of the latest available telemetrydata, RAMPAGE can deliver notificationof an alarm by electronic mail. Sub-scribers can then use RAMPAGE displaysto determine the state of the spacecraftand formulate a response to the alarm, ifnecessary. A user can query spacecraftmission data in either binary or comma-separated-value format by use of a Webform or a Practical Extraction and Re-porting Language (PERL) script to auto-mate the query process. RAMPAGE runson Linux and Solaris server computersin the Ground Data System (GDS) ofNASA’s Jet Propulsion Laboratory andincludes components designed specifi-cally to make it compatible with legacyGDS software. The client/server archi-tecture of RAMPAGE and the use of theJava programming language make it pos-sible to utilize a variety of competitiveserver and client computers, therebyalso helping to minimize costs.

This program was written by Ted Specht ofCaltech and David Noble of Oak Grove Con-sulting for NASA’s Jet Propulsion Labora-tory. Further information is contained in aTSP (see page 1).


Semi-Automated Identification of Rocks in Images

Rock Identification Toolkit Suite is acomputer program that assists users inidentifying and characterizing rocksshown in images returned by the MarsExplorer Rover mission. Included inthe program are components for auto-mated finding of rocks, interactive ad-justments of outlines of rocks, activecontouring of rocks, and automatedanalysis of shapes in two dimensions.The program assists users in evaluatingthe surface properties of rocks and soiland reports basic properties of rocks.The program requires either the MacOS X operating system running on aG4 (or more capable) processor or aLinux operating system running on aPentium (or more capable) processor,plus at least 128MB of random-accessmemory.

This program was written by BenjaminBornstein, Andres Castano, and Robert An-


derson of Caltech for NASA’s Jet Propul-sion Laboratory. Further information iscontained in a TSP (see page 1).


Pattern-Recognition Algorithm for Locking Laser Frequency

A computer program serves as part ofa feedback control system that locks thefrequency of a laser to one of the spec-tral peaks of cesium atoms in an optical-absorption cell. The system analyzes asaturation absorption spectrum to find atarget peak and commands a laser-

frequency-control circuit to minimize anerror signal representing the differencebetween the laser frequency and the tar-get peak. The program implements analgorithm consisting of the followingsteps:• Acquire a saturation absorption signal

while scanning the laser through thefrequency range of interest.

• Condition the signal by use of convolu-tion filtering.

• Detect peaks.• Match the peaks in the signal to a pat-

tern of known spectral peaks by use ofa pattern-recognition algorithm.

• Add missing peaks.• Tune the laser to the desired peak and

thereafter lock onto this peak.Finding and locking onto the desired

peak is a challenging problem, given

that the saturation absorption signal in-cludes noise and other spurious signalcomponents; the problem is furthercomplicated by nonlinearity and shiftingof the voltage-to-frequency correspon-dence. The pattern-recognition algo-rithm, which is based on Hausdorff dis-tance, is what enables the program tomeet these challenges.

This program was written by VahagKarayan, William Klipstein, Daphna Enzer,Philip Yates, Robert Thompson, and GeorgeWells of Caltech for NASA’s Jet PropulsionLaboratory. Further information is con-tained in a TSP (see page 1).



Materials

Designing Cure Cycles for Matrix/Fiber Composite PartsThis methodology enables production of void-free laminates.Langley Research Center, Hampton, Virginia

A methodology has been devised fordesigning cure cycles to be used in thefabrication of matrix/fiber compositeparts (including laminated parts). As usedhere, “cure cycles” signifies schedules ofelevated temperature and pressure asfunctions of time, chosen to obtain de-sired rates of chemical conversion of ini-tially chemically reactive matrix materialsand to consolidate the matrix and fibermaterials into dense solids. Heretofore,cure cycles have been designed followingan empirical, trial-and-error approach,which cannot be relied upon to yield opti-mum results. In contrast, the presentmethodology makes it possible to designan optimum or nearly optimum cure cyclefor a specific application.

Proper design of a cure cycle is criticalfor achieving consolidation of a reactive-matrix/fiber layup into a void-free lami-nate. A cure cycle for a composite con-taining a reactive resin matrix usuallyconsists of a two-stage ramp-and-hold tem-perature profile. The temperature andthe duration of the hold for each stage areunique for a given composite material.The first, lower-temperature ramp-and-hold stage is called the B stage in compos-ite-fabrication terminology. At this stage,

pressure is not applied, and volatiles (sol-vents and reaction by-products) are freeto escape. The second, higher-tempera-ture stage is for final forced consolidation.

The design of such a cure cycle is nottrivial. The trial-and-error approach, stillcommonly used in industry, has severaldrawbacks:• Extensive experimentation is usually

necessary for determining the propercure cycle for a given material,

• A cure cycle found to be satisfactory fora given material under one set of con-ditions may not apply under a differentset of conditions, and

• This approach does not ensure thatthe composite is cured completelyunder the optimal conditions andshortest amount of time.Therefore, the trial-and-error ap-

proach is deemed costly, time-consum-ing, and inefficient as a means of design-ing cure cycles for the production oflaminates of acceptable quality.

In order to make a void-free laminate,one must design the cure cycle to pro-vide for depletion of a sufficient propor-tion of volatiles through the B stage, be-fore consolidation. However, theviscosity of the resin increases during the

B stage. Therefore, it is necessary to de-sign the B stage so that the residual flu-idity of the resin after the B stage is suf-ficient to enable infiltration of resinthrough fiber bundles during the subse-quent pressure consolidation stage. Theproblem of balancing between the resid-ual volatile content and the residual flu-idity is very complex and unique for agiven composite system.

The present methodology is founded ona universal “processing science” approachin which one uses available analyticalequipment and techniques to effectivelymeasure and logically analyze and design aworkable cycle for any given uniqueresin/fiber composite. The methodologyincludes a protocol for:• Measurements by a thermal gravimet-

ric analyzer (TGA) to characterizemechanisms of depletion of volatiles,

• Differential scanning calorimetry(DSC) to characterize the degrees ofimidization reactions and some aspectsof the microstructures of partiallycured resins, and

• Melt rheometry to characterize theresidual fluidity and the temperatureof onset of gelation of a partially curedresin.

Determine relationship among kb and thermal-annealing

conditions Tb and tb.

Start with specimen that has kb < 0.5 specimen after annealing at Tb and tb.

Select Pc < 100 psi if ηmin < 105 P or Pc < 250 psi if ηmin < 106 P.

Measure the Tm,max (if any), by DSC.

Measure viscoelastic properties by rheometer.

Determine Tη.ηmin < 106 P?

Select progressively higher kb and associated Tb and tb.

Start with 0.5 < kb < 2, and then 2 < kb < 3, etc., if

necessary.

No

Yes

Nomenclature:weight percent of residual volatiles after B stage.kb =poise, a unit of viscosity.P =consolidation pressure.Pc =B-stage temperatureTb =duration of B stage.tb =consolidation temperature.Tc =maximum crystalline melting temperatureTm,max =temperature at which minimum viscosity occurs.Tη =minimum viscosity in P.ηmin =

LAR-16604-1ABPI

5-10-04 bs

A workable two-step ramp-and-hold cure cycle is

obtained. It consists of Tb, tb, and Tc > (Tη or Tm,max,

whichever is higher.

This Flow Diagram represents the iteration scheme of the cure-cycle-design methodology.


On the basis of these measurements,a workable cure cycle for the subjectcomposite system can be readily andlogically designed.

This design methodology involves aniteration scheme (see figure) for satisfy-ing several design criteria to arrive atthe design cure cycle for any given ther-moset-reactive-matrix-resin/fiber com-posite system. The number of iterationsis based upon scientific judgments in-stead of empirical reasoning. A work-able cure cycle can be established afteronly one iteration if the following crite-ria are satisfied:• The residual volatile content after the

B stage is < 0.5 weight percent;• The forced-consolidation temperature

(Tc) exceeds either the maximum crys-

talline melting temperature (Tm,max) orthe temperature at which minimum vis-cosity occurs (Tη); and

• The residual minimum viscosity (ηmin)is less than 106 poise.In the event that ηmin exceeds 106

poise, it is necessary to perform a sec-ond iteration utilizing a less severe B-stage condition. This condition re-sults in greater fluidity and greaterresidual volatile content after the Bstage. Consequently, ηmin is reducedto < 106 poise, making it possible touse only moderate pressure for finalconsolidation. Optionally, during thesecond temperature ramp beforefinal forced consolidation, the appli-cation of pressure can be delayeduntil the temperature reaches Tη in

order to allow for additional deple-tion of volatiles.

The subject resin/fiber composite ma-terial is considered unprocessable (inthat a laminated part made of this mate-rial cannot be made free of voids) undermoderate pressures when the above-mentioned criteria cannot be satisfiedconcurrently. It is possible to refine thecure cycle by narrowing the B-stage pre-treatment conditions in the TGA, DSC,and melt-rheometry analyses.

This work was done by Tan-Hung Hou ofLangley Research Center. For further in-formation, contact the Innovative Partner-ships Office, NASA Langley Research Center,3 Langley Boulevard, Mail Stop 200, Hamp-ton, VA 23681-2199. Tel: (757) 864-3936.LAR-16604-1


Machinery/Automation

Modification of a Limbed Robot to Favor ClimbingA kinematically simplified design affords several benefits.NASA’s Jet Propulsion Laboratory, Pasadena, California

The figure shows the LEMUR IIb,which is a modified version of theLEMUR II — the second generation ofthe Limbed Excursion Mechanical Util-ity Robot (LEMUR). Except as de-scribed below, the LEMUR IIb hard-

ware is mostly the same as that of theLEMUR II. The IIb and II versions dif-fer in their kinematic configurationsand characteristics associated with theirkinematic configurations. The differ-ences are such that relative to the

LEMUR II, the LEMURIIb is simpler and is bettersuited to climbing on in-clined surfaces.

The first-generationLEMUR, now denotedthe LEMUR I, was de-scribed in “Six-LeggedExperimental Robot”(NPO-20897), NASA TechBriefs, Vol. 25, No. 12 (De-cember 2001), page 58.The LEMUR II was de-scribed in “Second-Gen-eration Six-Limbed Ex-perimental Robot”(NPO-35140) NASA TechBriefs, Vol. 28, No. 11 (No-vember 2004), page 55.To recapitulate: theLEMUR I and LEMUR IIwere six-legged or six-

limbed robots for demonstrating ro-botic capabilities for assembly, mainte-nance, and inspection. They were de-signed to be capable of walkingautonomously along a truss structuretoward a mechanical assembly at a pre-scribed location. They were equippedwith stereoscopic video cameras andimage-data-processing circuitry for nav-igation and mechanical operations.They were also equipped with wirelessmodems, through which they could becommanded remotely. Upon arrival ata mechanical assembly, the LEMUR Iwould perform simple mechanical op-erations by use of one or both of itsfront legs (or in the case of the LEMURII, any of its limbs could be used to per-form mechanical operations). EitherLEMUR could also transmit images to ahost computer. The differences be-tween the LEMUR IIb and the LEMURII are the following:• Whereas the LEMUR II had six limbs,

the LEMUR IIb has four limbs. Thischange has reduced both the complex-ity and mass of the legs and of the over-all robot.

The LEMUR IIb Walking Robot is simpler and less massive, yet abetter climber, relative to its predecessor, the LEMUR II.

A document poses, and suggests a pro-gram of research for answering, questionsof how to achieve autonomous operationof herds of cooperative robots to be used inexploration and/or colonization of re-mote planets. In a typical scenario, a flockof mobile sensory robots would be de-ployed in a previously unexplored region,one of the robots would be designated theleader, and the leader would issue com-mands to move the robots to different loca-tions or aim sensors at different targets tomaximize scientific return. It would be nec-essary to provide for this hierarchical, co-operative behavior even in the face of suchunpredictable factors as terrain obstacles.A potential-fields approach is proposed as

a theoretical basis for developing methodsof autonomous command and guidance ofa herd. A survival-of-the-fittest approach issuggested as a theoretical basis for selec-tion, mutation, and adaptation of a de-scription of (1) the body, joints, sensors, ac-tuators, and control computer of eachrobot, and (2) the connectivity of eachrobot with the rest of the herd, such thatthe herd could be regarded as consisting ofa set of artificial creatures that evolve toadapt to a previously unknown environ-ment. A distributed simulation environ-ment has been developed to test the pro-posed approaches in the Titanenvironment. One blimp guides three sur-face sondes via a potential field approach.

The results of the simulation demonstratethat the method used for control is feasi-ble, even if significant uncertainty exists inthe dynamics and environmental models,and that the control architecture providesthe autonomy needed to enable surfacescience data collection.

This work was done by Marco B. Quadrelliof Caltech for NASA’s Jet Propulsion Labo-ratory. For further information, access theTechnical Support Package (TSP) free on-lineat www.techbriefs.com/tsp under the Softwarecategory.


Controlling Herds of Cooperative RobotsNASA’s Jet Propulsion Laboratory, Pasadena, California


• Whereas each limb of the LEMUR IIhad four degrees of freedom (DOFs),each limb of the LEMUR IIb has threeDOFs. This change has also reducedboth complexity and mass. Notwith-standing the decrease in the numberof DOFs, the three remaining DOFsare configured to provide greater dex-terity for motion along a surface.

• To extend reach, the limbs of theLEMUR IIb are 25 percent longer thanthose of the LEMUR II.

• Additional benefits stemming fromthe modifications are that the robotbody supported by the limbs is nowless massive and its center of gravityis now closer to the surface alongwhich the robot is to move.

These benefits have been obtainedwithout sacrificing load-carrying capac-ity. Hence, overall, the LEMUR IIb is amore adept climber.

This work was done by Avi Okon, BrettKennedy, Michael Garrett, and Lee Magnoneof Caltech for NASA’s Jet Propulsion Lab-oratory. Further information is contained ina TSP (see page 1). NPO-40354


Vacuum-Assisted, Constant-Force Exercise DeviceAn important advantage over other exercise machines would be light weight.Lyndon B. Johnson Space Center, Houston, Texas

The vacuum-assisted, constant-forceexercise device (VAC-FED) has beenproposed to fill a need for a safe, reli-able exercise machine that would pro-vide constant loads that could rangefrom 20 to 250 lb (0.09 to 1.12 kN) withstrokes that could range from 6 to 36 in.(0.15 to 0.91 m). The VAC-FED was orig-inally intended to enable astronauts inmicrogravity to simulate the lifting offree weights, but it could just as well beused on Earth for simulated weight lift-

ing and other constant-force exercises.Because the VAC-FED would utilize at-mospheric/vacuum differential pres-sure instead of weights to generateforce, it could weigh considerably lessthan either a set of free weights or a typ-ical conventional exercise machinebased on weights. Also, the use of atmos-pheric/vacuum differential pressure togenerate force would render the VAC-FED inherently safer, relative to freeweights and to conventional exercise

machines that utilize springs to gener-ate forces.

The overall function of the VAC-FEDwould be to generate a constant tensileforce in an output cable, which wouldbe attached to a bar, handle, or otherexercise interface. The primary forcegenerator in the VAC-FED would be apiston in a cylinder. The piston wouldseparate a volume vented to atmosphereat one end of the cylinder from an evac-uated volume at the other end of thecylinder (see figure). Hence, neglectingfriction at the piston seals, the forcegenerated would be nearly constant —equal to the area of the piston multi-plied by the atmospheric/vacuum dif-ferential pressure.

In the vented volume in the cylinder, adirect-force cable would be loopedaround a pulley on the piston, doublingthe stroke and halving the tension. Oneend of the direct-force cable would be an-chored to a cylinder cap; the other end ofthe direct-force cable would be wrappedaround a variable-ratio pulley that wouldcouple tension to the output cable. As itsname suggests, the variable-ratio pulleywould contain a mechanism that couldbe used to vary the ratio between the ten-sion in the direct-force cable and the ten-sion in the output cable. This mechanismcould contain gears, pulleys, and/orlevers, for example. By use of this mecha-nism, the tension in the output cablewould be set to a desired fraction of theforce generated by the pulley and thestroke would be multiplied by the recip-rocal of that fraction.

A vacuum could be generated in sev-eral alternative ways. The way thatwould involve the least equipmentwould involve the use of a one-way valvein an outlet at the vacuum end of thecylinder (the lower end in the figure).At first, the piston would be forced allthe way down in the cylinder to pushout most of the air from the lower cylin-der volume. Thereafter, the one-wayvalve would keep air from re-enteringthe lower cylinder volume, and the de-vice could be used to provide nearlyconstant tension on the cable during ex-ercise. Of course, air would gradually

Output Cable

Cylinder Cap

Vent and Cable Hole

Cylinder

This Volume Vented to AtmosphereThrough Cable Hole

Piston Pulley

Spring-Loaded Seals

EvacuatedVolume

VacuumPump

VacuumPump

One-Way ValvePressureRegulator

Low-PressureStorage Tank

Direct-Force Cable

MSC23180

7-31-00 bs

Atmospheric/Vacuum Differential Pressure on the piston would be utilized to generate an adjustable,nearly constant tension in the output cable.

Bio-Medical


leak past the piston seals into the lowercylinder volume, so that it would eventu-ally be necessary to repeat the initialbottoming of the piston to restore theatmospheric/vacuum differential pres-sure.

Alternatively, a vacuum could be gen-erated and maintained by use of asmall manual or electric vacuum

pump. Still another alternative is toconnect the lower cylinder volume tothe combination of a low-pressure stor-age tank, pressure regulator, and vac-uum pump. This combination could beused to maintain the lower cylinder vol-ume at a subatmospheric pressure(partial vacuum) that could be con-trolled to set the differential pressure

and thus the output-cable tension at adesired level.

This work was done by Christopher P.Hansen of Johnson Space Center andScott Jensen of Lockheed Martin Corp. Forfurther information, contact the JohnsonCommercial Technology Office at (281) 483-3809.MSC-23180

Production of Tuber-Inducing FactorThis substance regulates the growth of potatoes and some other plants.John F. Kennedy Space Center, Florida

A process for making a substance thatregulates the growth of potatoes andsome other economically importantplants has been developed. The processalso yields an economically importantby-product: potatoes.

The particular growth-regulating sub-stance, denoted tuber-inducing factor(TIF), is made naturally by, and acts nat-urally on, potato plants. The primary ef-fects of TIF on potato plants are reduc-ing the lengths of the main shoots,reducing the numbers of nodes on themain stems, reducing the total biomass,accelerating the initiation of potatoes,and increasing the edible fraction (pota-toes) of the overall biomass. To some ex-tent, these effects of TIF can overrideenvironmental effects that typically in-hibit the formation of tubers. TIF can beused in the potato industry to reducegrowth time and increase harvest effi-ciency. Other plants that have been ob-served to be affected by TIF includetomatoes, peppers, radishes, eggplants,marigolds, and morning glories.

In the present process, potatoes aregrown with their roots and stolons im-mersed in a nutrient solution in a recir-culating hydroponic system. From timeto time, a nutrient replenishment solu-tion is added to the recirculating nutri-ent solution to maintain the required

nutrient concentration, water is addedto replace water lost from the recirculat-ing solution through transpiration, andan acid or base is added, as needed, tomaintain the recirculating solution at adesired pH level. The growing potatoplants secrete TIF into the recirculatingsolution. The concentration of TIF inthe solution gradually increases to arange in which the TIF regulates thegrowth of the plants.

In a procedure for concentrating TIF,no attempt is made to separate TIF fromthe nutrient and other solutes in the so-lution. Instead, the solution is simplypoured onto flat trays at a depth between0.5 and 1.0 cm, then concentrated bydrying for 12 to 24 hours in a forced-airoven at a temperature of 70 °C. The con-centrated solution is stable at and belowroom temperature and in the presenceof ultraviolet light. Optionally, one canfreeze-dry the solution to remove all thewater, leaving a water-soluble dry powder.The concentrated solution or dry pow-der is stored in a dry environment.Thereafter, one simply adds deionizedwater to the concentrated solution or drypowder to make a TIF-containing nutri-ent solution having the desired lesserconcentration.

Results of laboratory tests suggestthat TIF-containing solutions made in

this way are suitable for use in diversesettings, including fields, green houses,and enclosed environments containingnatural- and artificial-soil-based as wellas hydroponic plant-growth systems. Po-tential commercial applications includethe following:• Hydroponic, aeroponic, or field pro-

duction of seed potatoes;• Dwarfing of bedding plants in con-

trolled environments;• Dwarfing of ornamental plants in fields

and in controlled environments; and• As a quasi-natural regulator (in this case,

as a suppressor) of the growth of weeds.This work was done by Gary W. Stutte

and Neil C. Yorio of Dynamac Corp. forKennedy Space Center.

Title to this invention, covered by U.S.Patent No. 5,992,090 has been waived underthe provisions of the National Aeronautics andSpace Act 42 U.S.C. 2457 (f). Inquiries con-cerning licenses for its commercial developmentshould be addressed to:

Gary W. Stutte, Ph.D. or Neil C. YorioPhone Nos.: (321) 861-3493 or

(321) 861-2497E-mail: [email protected] or

[email protected] to KSC-12007/513, volume and

number of this NASA Tech Briefs issue,and the page number.


Physical Sciences

The figure depicts a proposed semi-conductor laser, based on In(As)Sbquantum dots on a (001) InP substrate,that would operate in the wavelengthrange between 1.8 and 2.3 µm. InSb andInAsSb are the smallest-bandgap con-ventional III-V semiconductor materials,and the present proposal is an attemptto exploit the small bandgaps by usingInSb and InAsSb nanostructures as mid-infrared emitters.

The most closely related prior III-Vsemiconductor lasers are based, vari-ously, on strained InGaAs quantumwells and InAs quantum dots on InPsubstrates. The emission wavelengths ofthese prior devices are limited to about2.1 µm because of critical quantum-wellthickness limitations for these lattice-mismatched material systems.

The major obstacle to realizing theproposed laser is the difficulty of fabri-cating InSb quantum dots in sufficientdensity on an InP substrate. This diffi-culty arises partly because of the weak-ness of the bond between In and Sb andpartly because of the high temperatureneeded to crack metalorganic precursorcompounds during the vapor-phase epi-taxy used to grow quantum dots: Themobility of the weakly bound In at thehigh growth temperature is so high thatIn adatoms migrate easily on the growthsurface, resulting in the formation oflarge InSb islands at a density, usually

less than 5 × 109 cm–2, that is too low forlaser operation.

The mobility of the In adatoms couldbe reduced by introducing As atoms tothe growth surface because the In-Asbond is about 30 percent stronger than isthe In-Sb bond. The fabrication of theproposed laser would include a recentlydemonstrated process that involves theuse of alternative supplies of precursorsto separate group-III and group-Vspecies to establish local non-equilibriumprocess conditions, so that In(As)Sbquantum dots assemble themselves on a(001) InP substrate at a density as high as4 × 1010 cm–2. Room-temperature photo-luminescence spectra of quantum dotsformed by this process indicate that theyemit at wavelengths from 1.7 to 2.3 µm.

This work was done by Yueming Qiu of Cal-tech for NASA’s Jet Propulsion Labora-tory. Further information is contained in aTSP (see page 1).

In accordance with Public Law 96-517, thecontractor has elected to retain title to this inven-tion. Inquiries concerning rights for its commer-cial use should be addressed to:

Innovative Technology Assets ManagementJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099(818) 354-2240E-mail: [email protected] to NPO-40653, volume and number of

this NASA Tech Briefs issue, and the pagenumber.

Quantum-Dot Laser for Wavelengths of 1.8 to 2.3 µmProcess conditions must be controlled to form quantum dots at sufficient density.NASA’s Jet Propulsion Laboratory, Pasadena, California

Laser BeamOut

AuContact

Polyimide

First-OrderGrating

(Optional)

Active RegionContaining

Quantum Dots

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In the Proposed Semiconductor Laser, the active region would contain In(As)Sb quantum dots, whichemit at wavelengths from 1.7 to 2.3 µm. The first-order grating would be included, optionally, to se-lect operation at a single wavelength.

A tunable third-order band-pass opti-cal filter has been constructed as an as-sembly of three coupled, tunable, whis-pering-gallery-mode resonators similarto the one described in “Whispering-Gallery-Mode Tunable Narrow-Band-Pass Filter” (NPO-30896), NASA TechBriefs, Vol. 28, No. 4 (April 2004), page5a. This filter offers a combination offour characteristics that are desirable for

potential applications in photonics: (1)wide real-time tunability accompaniedby a high-order filter function, (2) nar-rowness of the passband, (3) relativelylow loss between input and output cou-pling optical fibers, and (4) a sparsespectrum. In contrast, prior tunableband-pass optical filters have exhibited,at most, two of these four characteristics.

As described in several prior NASA Tech

Briefs articles, a whispering-gallery-mode(WGM) resonator is a spheroidal, disklike,or toroidal body made of a highly transpar-ent material. It is so named because it is de-signed to exploit whispering-gallery elec-tromagnetic modes, which are waveguidemodes that propagate circumferentiallyand are concentrated in a narrow toroidalregion centered on the equatorial planeand located near the outermost edge.

Tunable Filter Made From Three Coupled WGM ResonatorsThis is a prototype of high-performance filters for photonic applications.NASA’s Jet Propulsion Laboratory, Pasadena, California


Figure 1 depicts the optical layout ofthe present filter comprising an assemblyof three coupled, tunable WGM res-onators. Each WGM resonator is madefrom a disk of Z-cut LiNbO3 of 3.3-mm di-

ameter and 50-µm thickness. The perime-ter of the disk is polished and rounded toa radius of curvature of 40 µm. The freespectral range of each WGM resonator isabout 13.3 GHz. Gold coats on the flat

faces of the disk serve as electrodes for ex-ploiting the electro-optical effect inLiNbO3 for tuning. There is no metalcoat on the rounded perimeter region,where the whispering-gallery modespropagate. Light is coupled from aninput optical fiber into the whispering-gallery modes of the first WGM resonatorby means of a diamond prism. Anotherdiamond prism is used to couple lightfrom the whispering-gallery modes of thethird WGM resonator to an output opti-cal fiber.

The filter operates at a nominal wave-length of 1,550 nm and can be tunedover a frequency range of ±12 GHz by ap-plying a potential in the range of ±150 Vto the electrodes. The insertion loss (theloss between the input and output cou-pling optical fibers) was found to be re-peatable at 6 dB. The resonance qualityfactor (Q) of the main sequence of res-onator modes was found to be 5 × 106,which corresponds to a bandwidth of 30MHz. The filter can be shifted from oneoperating frequency to another within atuning time ≤30 µs. The transmissioncurve of the filter at frequencies near themiddle of the passband closely approxi-mates a theoretical third-order Butter-worth filter profile, as shown in Figure 2.

This work was done by Anatoliy Savchenkov,Vladimir Iltchenko, Lute Maleki, and AndreyMatsko of Caltech for NASA’s Jet PropulsionLaboratory. Further information is containedin a TSP (see page 1).




Light In Light Out

Output CouplingOptical Fiber

Input CouplingOptical Fiber

DiamondPrism

DiamondPrism

Three CoupledWGM Resonators

With Tuning Electrodes

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Figure 1. Three Coupled, Tunable WGM Resonators constitute a third-order tunable band-pass opticalfilter.

Figure 2. The Measured Transmission Spectrum of the filter was fitted with a Butterworth profilefunction γ6/[(ν)6+γ6], where γ = 29 MHz and ν is the laser frequency detuning (the difference betweenthe laser frequency and the peak-transmission frequency).

A method that would notably includedynamic pupil masking has been pro-posed as an enhanced version of a priormethod of phasing the segments of aprimary telescope mirror. The method

would apply, more specifically, to a pri-mary telescope mirror that comprisesmultiple segments mounted on actua-tors that can be used to tilt the segmentsand translate them along the nominal

optical axis to affect wavefront control inincrements as fine as a fraction of awavelength of light. An apparatus (seefigure) for implementing the proposedmethod would be denoted a dispersed-

Dynamic Pupil Masking for Phasing Telescope Mirror SegmentsPiston and tilt adjustments could be performed more efficiently.NASA’s Jet Propulsion Laboratory, Pasadena, California


fringe-sensor phasing camera system(DPCS).

The prior method involves the use ofa dispersed-fringe sensor (DFS). Theprior method was reported as part of amore comprehensive method in “CoarseAlignment of a Segmented TelescopeMirror” (NPO-20770), NASA Tech Briefs,Vol. 25, No. 4 (April 2001), page 15a.The pertinent parts of the prior methodare the following:• The telescope would be aimed at a

bright distant point source of light(e.g., a star) and form a broadbandimage on an imaging detector arrayplaced at the telescope focal plane.

• The construction and use of a dis-persed-fringe sensor would begin withinsertion of a grism (a right-angleprism with a transmission grating onthe hypotenuse face) into the opticalpath. With other segments tilted awayfrom the investigating region of thedetector, a dispersed-fringe imagewould be formed by use of a desig-nated reference segment and a se-lected mirror segment. The modula-tion period and orientation of thefringe would be analyzed to determinethe magnitude and sign of the pistonerror (displacement along the nomi-nal optical axis) between the two seg-ments. The error would be used to per-form a coarse-phase piston adjustmentof the affected mirror segment. Thisdetermination and removing of piston

error is what is meant by “phasing” asused above. The procedure as de-scribed thus far would be repeateduntil all segments had been phased.A major drawback of the prior

method is the time-consuming nature ofthe repeated tilting of mirror segments,necessitated by the fact that the DFS asdescribed above could not be used tophase more than two mirror segments ata time. To be able to phase more thantwo segments simultaneously, it wouldbe necessary to augment the DFS withan array of prisms and a pupil mask andto implement a complicated pupil-regis-tration process.

In the proposed method, the need forrepeated tilting would be eliminated byusing a programmable spatial light mod-ulator (SLM) as a dynamic segment edgemask in conjunction with a weak cylindri-cal lens: At a given instant of time, theSLM would be made transparent only inareas containing the edges of the mirrorsegments to be phased. Elsewhere, theSLM would be opaque to block light fromall other mirror segments. The SLMwould also enable accurate in situ pupilregistration and could readily be adaptedto different segment geometries. Also aspart of the proposed method, the weakcylindrical lens would be used to separateDFS fringes across the wavelength disper-sion of the grism, thereby making it pos-sible to phase multiple pairs of mirrorsegments in one image exposure. Hence,

the combination of the SLM and theweak cylindrical lens would greatly in-crease the efficiency of the segment-phas-ing process.

Other elements of the proposedmethod are the following:• The DPCS could be designed to en-

able simultaneous measurements ontwo edge orientations of the hexago-nal segments by use of both polariza-tion channels. Alternatively, as shownin the figure, the DFS assembly in theDPCS could be designed to rotateabout the optical axis, enabling meas-urements on all segment edges.

• The combination of a flip-in pupil im-aging lens and the SLM would enableaccurate pupil registration.

• The DFS assembly could be removedand a weak spherical lens used in combi-nation with the SLM to form a Shack-Hartmann sensor for measuring tilts ofmirror segments. In this case, the SLMwould be used to create subapertureswithin each segment.

• The weak spherical lens could also serveas part of a prescription-retrieval sensor,the use of which would enable furtherreduction of piston errors. In this case,the SLM would be used to form sub-apertures on the segment edges.This work was done by Fang Shi, David

Redding, Catherine Ohara, and Mitchell Troyof Caltech for NASA’s Jet Propulsion Labo-ratory. Further information is contained in aTSP (see page 1). NPO-41996

Weak CylindricalLens

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A DPCS would combine several telescope-alignment instruments into one that would function more efficiently.

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