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Maxwell, M. S.

Publications and source records attributed to Maxwell, M. S..

16 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The Sequential Filter Imaging Radiometer (SFIR), a new instrument configuration for Earth observations

The sequential filter imaging radiometer (SFIR) concept is presented, contrasted with other sensor configurations, and its strengths and weaknesses discussed. In a pushbroom SFIR the optics images the scene onto a long, narrow area array. The length of the array defines the field of view. The spectral defining filters are sequentially placed over the full array, a sample of data for that band taken, and then the next filter placed in front of the array. All of the filters are placed over the array in the time that it takes the image of the scene to advance the array width. Thus the entire scene is observed in each band. Advantages of the SFIR are: spectral bands can be broad, narrow or overlap; it is easy to improve signal to noise ratio; and it is simple to make bands polarized. Its main disadvantage is that it requires more detectors than other instrument configurations.

Maxwell, M. S.↗
NASA NTRS1986

High-resolution observations of low contrast phenomena from an advanced geosynchronous platform

Present technology allows radiometric monitoring of the earth, ocean and atmosphere from a geosynchronous platform with good spatial, spectral and temporal resolution. The proposed system could provide a capability for multispectral remote sensing with a 50 m nadir spatial resolution in the visible bands, 250 m in the 4 micron band and 1 km in the 11 micron thermal infrared band. The diffraction limited telescope has a 1 m aperture, a 10 m focal length (with a shorter focal length in the infrared) and linear and area arrays of detectors. The diffraction limited resolution applies to scenes of any brightness but for a dark low contrast scenes, the good signal to noise ratio of the system contribute to the observation capability. The capabilities of the AGP system are assessed for quantitative observations of ocean scenes. Instrument and ground system configuration are presented and projected sensor capabilities are analyzed.

Maxwell, M. S.↗
NASA NTRS1984

High resolution observations of low contrast phenomena from an Advanced Geosynchronous Platform (AGP)

Present technology allows radiometric monitoring of the Earth, ocean and atmosphere from a geosynchronous platform with good spatial, spectral and temporal resolution. The proposed system could provide a capability for multispectral remote sensing with a 50 m nadir spatial resolution in the visible bands, 250 m in the 4 micron band and 1 km in the 11 micron thermal infrared band. The diffraction limited telescope has a 1 m aperture, a 10 m focal length (with a shorter focal length in the infrared) and linear and area arrays of detectors. The diffraction limited resolution applies to scenes of any brightness but for a dark low contrast scenes, the good signal to noise ratio of the system contribute to the observation capability. The capabilities of the AGP system are assessed for quantitative observations of ocean scenes. Instrument and ground system configuration are presented and projected sensor capabilities are analyzed.

Maxwell, M. S.↗
NASA NTRS1984

A case for Gohrem - Geosynchronous orbit high resolution earth monitoring

Although the constant viewing geometry of the geostationary orbit simplifies quantitative monitoring of study areas, the high satellite altitude, in conjunction with the need for high spatial resolution, leads to large and complex sensors and spacecraft. State-of-the-art linear array detectors and a telescope of 1 m diameter and 10 m focal length can meet the requirements in question, which include a scan rate of the ground of at least 25 km/sec, the ability to cover a 150 X 150-km scene every several minutes, and an instantaneous field of view of 50 m in the visible portion of the spectrum and 1000 m in the IR.

Otterman, J.↗
NASA NTRS1982

Recommended satellite imagery capabilities for disaster management

This study explores the role that satellite imaging systems might play in obtaining information needed in the management of natural and manmade disasters. Information requirements which might conceivably be met by satellite were identified for over twenty disasters. These requirements covered pre-disaster mitigation and preparedness activities, disaster response activities, and post-disaster recovery activities. The essential imaging satellite characteristics needed to meet most of the information requirements are 30 meter (or finer) spatial resolution, frequency of observations of one week or less, data delivery times of one day or less, and stereo, synoptic all-weather coverage of large areas in the visible, near infrared, thermal infrared and microwave bands. Of the current and planned satellite systems investigated for possible application to disaster management, Landsat-D and SPOT appear to have the greatest potential during disaster mitigation and preparedness activities, but all satellites studied have serious deficiencies during response and recovery activities. Several strawman concepts are presented for a satellite system optimized to support all disaster management activities.

Richards, P. B.↗
NASA NTRS1976

Documentation of the recording environment

The distortion and degradation of the informational content of satellite sensed data by scene generation and atmospheric propagation are discussed. A method is described for obtaining a system point spread function representing the fractional radiance poisoning each pixel gives and receives. The sensor data output is then reprocessed or restored. The degree of restoration is signal to noise dependent. A technique is given for approximating the impact of the atmosphere on the propagation of scene radiance.

Ritter, M.↗
NASA NTRS1973

Plural beam antenna

An antenna capable of deriving several beams about a single boresight axis including a focusing means, such as a parabolic reflector or a lens is described. Plural arrays, each including plural radially aligned antenna elements extending from the boresight axis, are located in proximity to a focal point for the focusing means. The elements of the plural arrays are independently excited as each of the arrays is independently rotated about the boresignt axis.

Keller, G. C.↗
NASA NTRS1973

Multimegabit Operation Multiplexer System

The Multimegabit Operation Multiplexer System (MOMS) is a high-data-rate PCM telemetry unit capable of sampling and encoding 60 scanning radiometer and four vidicon channels at 250 kilosamples/second and 5 megasamples/second, respectively. This sampling capacity plus the seven-bit quantization requires a total throughput rate of 40 megasamples/second and 280 megabits/second. To produce these rates efficiently, the system was divided into a pair of identical 140-megabit blocks. A low-power 20-MHz analog multiplexer and analog-to-digital converter were developed together with a video sample-and-hold that features an aperture time error of less than 50 psec. Breadboard testing of these basic building blocks confirmed the design prediction that the total system would consume 27 watts of power. Two 140-megabit output parts are suitable for quadriphase modulation.

Giri, R. R.↗
NASA NTRS1971

Radial rotating antenna-feed system

System incorporating two or more radial feed assemblies tracks and communicates with multiple moving transmitters, receivers, or transponders. System utilizes a fixed parabolic reflector or other beam-forming device such as a lens or spherical reflector.

Dodd, L. R.↗