NASA - National Aeronautics and Space Administration

The CPI records high-resolution (2.3 micron pixel size) digital images of particles that pass through the sample volume at speeds up to 200 m/s. In older models, CCD camera flashes up to 75 frames per second (fps), potentially imaging more than 25 particles per frame. More recent camera upgrades capable of bringing frame rate to nearly 500 fps. Real time image processing crops particle images from the full frame, eliminating blank space and compressing data by >1000:1. CPI is designed for ummanned use, with AI parameters to optimize performance without supervision.

During the 1980s, in the framework of its Earth observation program, NASA organized several workshops at which scientists demonstrated the roles of soil moisture and ocean salinity in the global environmental system. Passive microwave radiometry could be used to measure these two geophysical parameters, but the most suitable frequency bands were those below 5 GHz and it was difficult to achieve the required spatial resolution with an antenna of reasonable size. NASA's Goddard Spaceflight Center, in collaboration with the University of Massachusetts at Amherst and the US Department of Agriculture, proposed the use of aperture synthesis as a solution to this problem for the first time and started to build an aircraft-borne prototype to test the concept. This NASA ESTAR (Electronically Scanned Thinned Array Radiometer) sensor was designed to be an L-band hybrid real- and synthetic-aperture radiometer and the instrument's validity was demonstrated in several USDA campaigns.

The NASA-Langley GPS remote sensing (GPSRS) instrument simultaneously correlates the unique satellite pseudo-random noise (PRN) code in a given satellite signal with an instrument-generated copy of the code. For each surface measurement, the reflected signal is correlated at 14 successive delay times (or delay bins) relative to the arrival of the signal from the specular point. The correlation results are squared as part of instrument signal processing and recorded for later analysis.

Two GPS-derived classification features are merged with visible image data to create terrain-moisture (TM) classes, or visibly identifiable terrain or landcover classes containing a surface/soil moisture component. As compared to using surface imagery alone, classification accuracy is significantly improved for a number of visible classes when adding the GPS-based signal features. Since the strength of the reflected GPS signal is proportional to the amount of moisture in the surface, use of these GPS features provides information about the surface that is not obtainable using visible wavelengths alone. Application areas include hydrology, precision agriculture, and wetlands mapping.

GISMO is a concept for a spaceborne radar system designed to measure the surface and basal topography of terrestrial ice sheets and to determine the physical properties of the glacier bed. Our primary objective is to develop this new technology for obtaining spaceborne estimates of the mass of the polar ice sheets with an ultimate goal of providing essential information to modelers estimating the mass balance of the polar ice sheets and estimating the response of ice sheets to changing climate. Our technology concept employs VHF and P-band interferometric radars using a novel clutter rejection technique for measuring the surface and bottom topographies of polar ice sheets. Our approach will enable us to reduce signal contamination from surface clutter, measure the topography of the glacier bed, and paint a picture of variations in bed characteristics. The technology will also have applications for planetary exploration including studies of the Martian ice caps and the icy moons of the outer solar system. We have recently shown that it is possible to image a small portion of the base of the polar ice sheets using a SAR approach. Through the concept developed here, we believe that, for the first time, we can image the base and map the 3-dimensional basal topography beneath an ice sheet at up to 5 km depth.

GISMO is a NASA Instrument Incubator Project.

The GIFS instrument, a tunable triple-etalon Fabry-Perot Imaging Spectrometer, is designed to measure the O2 absorption lines in solar radiation reflected off the Earth’s surface. This optical technique can provide data to characterize cloud properties in 2 dimensions. The instrument also potentially provides measurements with spatial resolution, spatial coverage, revisit time, and precision/accuracy that would be difficult to obtain with existing methods.

The instrument enables measurements of cloud top temperature, pressure and altitude on a global scale, when deployed in geostationary orbit. Introduction of these data points into weather forecasting models will lead to significant improvements in the forecasting of weather events, including hurricane motion and intensity. The GIFS instrument successfully flew and operated on-board a NASA P-3 Orion in multiple flights throughout January and February 2008.

D2P is a JHU/APL (Johns Hopkins University/Applied Physics Laboratory) designed, built, and operated airborne radar instrument sponsored by NASA's Instrument Incubator Program (start in 1998). The goal of this project is to demonstrate the use of two enhancements to satellite radar altimetry and to reduce the risk to a future flight program that would employ an enhanced altimeter.

The D2P system is composed of two logical portions: the flight system, and the ground system. The flight system has also two logical sections:

• A set of RF and digital components that create, amplify and transmit the radar pulse, and receivers to capture the returning radar echoes

• A set of computers that control the operation of the RF/digital components as well as digitizing and recording the received data.

Developed by Droplet Measurement Technologies, the CFSTGC is based on a concept by Roberts and Nenes [2005]. The instrument counts the fraction of aerosol particles that become droplets when exposed to a given water vapor supersaturation (RH > 100%).

As with all CCN counters, a temperature gradient is applied to produce a supersaturation of water vapor. However, the mechanism for generating supersaturation is not the same for all CCN counters. For example, for continuous flow parallel plate diffusion chambers, the temperature gradient is perpendicular to the flow, and supersaturation is a result of the nonlinear dependence of vapor pressure upon temperature. The same mechanism applies for static diffusion cloud chambers, where there is no flow at all.

However, as the name implies, for the Continuous Flow Streamwise Thermal Gradient CCN Counter, the temperature gradient is in the streamwise direction (maintained by thermoelectric coolers). In this case, supersaturation results as a consequence of the greater rate of mass transfer over heat transfer.

With laminar flow, heat and water vapor are transferred to the centerline of the column from the walls only by diffusion.

Since molecular diffusivity is greater than thermal diffusivity, the distance downstream that a water molecule travels before reaching the centerline is less than the distance the heat travels downstream before reaching the centerline. If you pick a point at the centerline, the heat originated from a greater distance upstream than the water vapor.

There are four facts that are necessary to explain how supersaturation is generated within the CFSTGC:

1) Assuming that the inner surface of the column is saturated with water vapor at all points, since the temperature is greater at point B than at point A, the water vapor partial pressure is also greater at point B than at point A.

2) The actual partial pressure of water vapor at point C is equal to the partial pressure of water vapor at point B.

3) However, since the temperature at point C is the same as at point A, the equilibrium water vapor pressure at point C is equal to the water vapor partial pressure at point A.

4) The saturation ratio is the ratio between the actual partial pressure of water vapor and the equilibrium vapor pressure. This is equivalent to the partial pressure at point B divided by the partial pressure at point A, which is always greater than one. Thus supersaturation is generated through a dynamic equilibrium.