NASA Technical Reports Server (NTRS) 20100001357: Multi-Sensor Mud Detection

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by  NASA Technical Reports Server (NTRS)

Technology Focus: Sensors
Cryogenic Flow Sensor
Marshall Space Flight Center, Alabama
An acousto-optic cryogenic flow sen- wave and a laser beam are present. termined from the diffraction angle.
sor (CFS) determines mass flow of When an acoustic wave is launched into The CFS acoustic Bragg grating data
cryogens for spacecraft propellant the optical medium, it generates a re- test indicates that it is capable of accu-
management. The CFS operates unob- fractive index wave that behaves like a si- rately determining flow from 0 to 10
trusively in a high-pressure, high-flow- nusoidal grating. An incident laser meters per second. The same sensor
rate cryogenic environment to provide beam passing through this grating will can be used in flow velocities exceeding
measurements for fluid quality as well diffract the laser beam into several or- 100 m/s. The POL module has success-
as mass flow rate. Experimental hard- ders. Its angular position is linearly pro- fully determined the onset of two-phase
ware uses an optical “plane-of-light” portional to the acoustic frequency, so flow, and can distinguish vapor bubbles
(POL) to detect the onset of two-phase that the higher the frequency, the larger from debris.
flow, and the presence of particles in the diffracted angle. This work was done by John Justak of Ad-
the flow of water. If the acoustic wave is traveling in a vanced Technologies Group, Inc. for Marshall
Acousto-optic devices are used in moving fluid, the fluid velocity will af- Space Flight Center. For more
laser equipment for electronic control fect the frequency of the traveling wave, information, contact Sammy Nabors, MSFC
of the intensity and position of the laser relative to a stationary sensor. This fre- Commercialization Assistance Lead, at
beam. Acousto-optic interaction occurs quency shift changes the angle of dif- [email protected]. Refer to MFS-
in all optical media when an acoustic fraction, hence, fluid velocity can be de- 32730-1.
Multi-Sensor Mud Detection
This technology is also applicable to terrain hazard assessment in terrestrial or planetary
situations.
NASA’s Jet Propulsion Laboratory, Pasadena, California
Robust mud detection is a critical per- mud body during a mission may have to be tectable electromagnetic signals, passive
ception requirement for Unm anned sacrificed or rescued, both of which are un- sensors are desirable.
Ground Vehicle (UGV) autono mous off- attractive options. There are several char- JPL has developed a daytime mud de-
road navigation. A military UGV stuck in a acteristics of mud that may be detectable tection capability using multiple passive
with appropriate UGV-mounted sensors. imaging sensors. Cues for mud from
For example, mud only occurs on the multiple passive imaging sensors are
ground surface, is cooler than surround- fused into a single mud detection image
ing dry soil during the daytime under using a rule base, and the resultant mud
nominal weather conditions, is generally detection is localized in a terrain map
darker than surrounding dry soil in visible using range data generated from a stereo
imagery, and is highly polarized. However, pair of color cameras. Thus far at the
none of these cues are definitive on their time of this reporting, JPL has:
own. Dry soil also occurs on the ground 1. Performed daytime data collections,
surface, shadows, snow, ice, and water can on wet and dry soil, with several candi-
also be cooler than surrounding dry soil, date passive imaging sensors, including
shadows are also darker than surrounding multi-spectral (blue, green, red, and
dry soil in visible imagery, and cars, water, near-infrared bands), short-wave in -
and some vegetation are also highly polar- frared, mid-wave infrared, long-wave
ized. Shadows, snow, ice, water, cars, and infrared, polarization, and a stereo
vegetation can all be disambiguated from pair of color cameras.
mud by using a suite of sensors that span 2. Characterized the advantages and dis-
multiple bands in the electromagnetic advantages of each passive imaging
A General Dynamics Robotic Systems (GDRS) ex-
spectrum. Because there are military oper- sensor to provide cues for mud.
perimental unmanned vehicle (XUV) navigates
through a muddy grass field during a data col- ations when it is imperative for UGV’s to 3. Implemented a first-generation mud
lection for the Daytime Mud Detection System. operate without emitting strong, de- detector that uses a stereo pair of color
bt
NASA Tech Briefs, January 2010 5
cameras and a polarization camera. For clutter pixels with high DOLP (such as tecting mud hazards from a UGV without
each set of input images, the innovators vegetation) are ignored. having to drive on the hazard first.
calculate degree of linear polarization Techniques to estimate soil moisture Mud detection is a terrestrial applica-
(DOLP), back-project polarization pix- content have been studied for decades tion; however, the intermediate image
els that have high DOLP into the left for agricultural applications; however, processing steps and world modeling tech-
color image, generate a stereo range mud detection for UGV autonomous nav- niques performed for this task are valu-
image (which is registered with the left igation is a relatively new research area. able to terrain hazard assessment in gen-
color image), and insert detected mud Ground vehicle methods of soil moisture eral, terrestrial, or planetary situations.
into a world map using the stereo range estimation have used passive microwave This work was done by Arturo L. Rankin
data. As it is only expected for mud to sensors, but the antennas tend to be and Larry H. Matthies of Caltech for
occur on the ground surface, stereo bulky and have been mounted directly NASA’s Jet Propulsion Laboratory. For more
range data are used to isolate ground downwards. This requires a UGV to drive information, contact [email protected].
surface pixels from the other pixels cor- on potentially hazardous terrain in order NPO-46624
responding to ground clutter. Ground to characterize it. This work involves de-
Gas Flow Detection System
Commercial applications include flow measurement systems.
John F. Kennedy Space Center, Florida
This system provides a portable means digital conversion as well as digital control. temperature peak to its stable “with
to detect gas flow through a thin-walled This data acquisition box is then con- flow” temperature will allow the opera-
tube without breaking into the tubing nected to a commercial laptop running a tor to determine whether a minimum
system. The flow detection system was custom application created using National level of flow exists.
specifically designed to detect flow Instruments’ LabVIEW. An alternative operation has the op-
through two parallel branches of a mani- The operation of the PVD WCCS Flow erator turning on the software only
fold with only one inlet and outlet, and is Detection System consists of first attach- long enough to record the ambient
a means for verifying a space shuttle pro- ing a heater/thermistor assembly to temperature of the tubing before turn-
gram requirement that saves time and re- each of the two branches of one mani- ing on the heaters and initiating GN2
duces the risk of flight hardware damage fold while there is no flow through the flow. The stable temperature of the
compared to the current means of re- manifold. Next, the software application heated tubing with GN2 flow is then
quirement verification. running on the laptop is used to turn on compared with the ambient tubing
The prototype Purge Vent and Drain the heaters and to monitor the manifold temperature to determine if flow is
Window Cavity Conditioning System (PVD branch temperatures. When the system present in each branch. To help quan-
WCCS) Flow Detection System consists of a has reached thermal equilibrium, the tify the level of flow in the manifolds,
heater and a temperature-sensing thermis- software application’s graphical user in- each branch will be bench calibrated to
tor attached to a piece of Velcro to be at- terface (GUI) will indicate that the establish its thermal properties using
tached to each branch of a WCCS mani- branch temperatures are stable. The op- the flow detection system and different
fold for the duration of the requirement erator can then physically open the flow flow rates. These calibration values can
verification test. The heaters and thermis- control valve to initiate the test flow of then be incorporated into the software
tors are connected to a shielded cable and gaseous nitrogen (GN2) through the application to provide more detailed
then to an electronics enclosure, which manifold. Next, the software user inter- flow rate information.
contains the power supplies, relays, and cir- face will be monitored for stable temper- This work was done by Thomas Moss, Cur-
cuit board to provide power, signal condi- ature indications when the system is tis Ihlefeld, and Barry Slack of Kennedy
tioning, and control. The electronics en- again at thermal equilibrium with the Space Center. For further information, contact
closure is then connected to a commercial test flow of GN2. The temperature drop the Kennedy Applied Physics Laboratory at
data acquisition box to provide analog to of each branch from its “no flow” stable [phone]. KSC-13174
Mapping Capacitive Coupling Among Pixels in a Sensor Array
Cross-talk calibration of all pixels can be performed efficiently.
NASA’s Jet Propulsion Laboratory, Pasadena, California
An improved method of mapping the characterizing such an array. The method high-performance imaging scientific in-
capacitive contribution to cross-talk among is applicable to almost all image detectors struments at the other extreme. In com-
pixels in an imaging array of sensors (typi- in modern electronic cameras for diverse parison with prior methods of quantifying
cally, an imaging photodetector array) has applications, ranging from consumer cel- the capacitive coupling among pixels, this
been devised for use in calibrating and/or lular-telephone cameras at one extreme to method is a more efficient means of ob-
6 NASA Tech Briefs, January 2010