James W. Hoffman

Preliminary spaceflight results from the uncooled infrared spectral imaging radiometer (ISIR) on shuttle mission STS-85

In August 1997 an infrared spectral imaging radiometer (ISIR) based on uncooled microbolometer array technology was flown on space shuttle mission STS-85. In this paper the design of the instrument and experimental goals are presented, and initial results from the flight mission are described. The ISIR instrument provided 1/4 km resolution imagery at four wavelengths that were selected for cloud remote sensing. A major goal of the work is development of compact and less costly cloud imagers for small satellite missions. A large data set of earth imagery and test operations was obtained from the mission. In most regards the ISIR functioned within its design parameters.

Design and fabrication of the Infrared Spectral Imaging Radiometer (ISIR)

The design and fabrication of the infrared spectral imaging radiometer (ISIR) is presented. The ISIR was designed in 1994 to provide calibrated images in four thermal wavelength bands without cryogenic cooling by utilizing the new, uncooled microbolometer detector technology. The complete system was fabricated at Space Instruments, Inc. (SI) in 1995 and 1996 and delivered to NASA Goddard Space Flight Center (GSFC) for flight on the space shuttle in 1997. Photographs of the flight hardware are shown. The ISIR operates in a pushbroom fashion and utilizes real time, digital time delay and integration (TDI) to improve the signal to noise ratio. From a nominal shuttle altitude of 140 nmi, the nadir pixel subtends 240 by 240 meters on the ground. The size of the radiometer is minimized by the elimination of mechanical scan mechanisms and a space radiator. The ISIR instrument utilizes a through-the- optics calibration system to periodically obtain a two-point calibration for each pixel in the detector array. A blackbody with both heating and cooling capability is used to obtain accurate calibration data for both terrestrial and cloudtop measurements. The timeline logic, TDI integration, mechanism control, calibration, and data formatting are performed in the onboard digital processor which utilizes two microprocessors and seven programmable logic devices. The output data is recorded on two, 8 mm tape recorders.

FireMapper 2.0: a multispectral uncooled infrared imaging system for airborne wildfire mapping and remote sensing

FireMapper®2.0 is a second-generation airborne system developed specifically for wildfire mapping and remote sensing. Its design is based on lessons learned from two years of flight-testing of a research FireMapper® system by the Pacific uthwest Research Station of the USDA Forest Service. The new, operational design features greater coverage and improved performance with a rugged sensor that is less than one third the size and weight of the original research sensor. The sensor obtains thermal infrared images in two narrow spectral bands and one wide spectral band with the use of a single uncooled microbolometer detector array. The dynamic range of the sensor is designed to accurately measure scene temperatures from normal backgrounds, for remote sensing and disaster management applications, up to flaming fronts without saturating. All three channels are extremely linear and are calibrated in-flight with a highly accurate absolute calibration system. Airborne testing of the research system has led to improved displays and simplified operator interfaces. These features facilitate the operational use of the FireMapper®2.0 system on both fixed wing aircraft and helicopters with minimal operator inputs. The operating system features custom software to display and zoom in on the images in realtime as they are obtained. Selected images can also be saved and recalled for detailed study. All images are tagged with GPS date, time, latitude, longitude, altitude, and heading and can be recorded on a portable USB hard drive upon operator command. The operating system can also be used to replay previously recorded image sequences. The FireMapper® 2.0 was designed and fabricated by Space Instruments, Inc. as part of a Research Joint Venture with the USDA Forest Service.

ISIR (Infrared Spectral Imaging Radiometer) flight results from shuttle mission STS-85

ISIR (Infrared Spectral Imaging Radiometer) was designed and fabricated by Space Instruments, Inc. and flown by NASA/GSFC on the Discovery shuttle mission STS-85 in August 1997. ISIR collected over 60 hours of infrared data on a variety of cloud, land, and ocean scenes. Data was obtained in four spectral bands with a single, uncooled microbolometer detector array operating in the pushbroom mode. Data was collected with varying amounts of TDI (Time Delay & Integration) to enhance system sensitivity. The design of the ISIR instrument and selected mission results will be presented.

HIPPI-6400 technology dissemination

This report covers the technological aspects of high performance parallel interface-6400 (HIPPI-6400), a forthcoming upgrade to the existing HIPPI protocol suite. The report concentrates on the technological advancements and situations that occur in a 6400 Megabit/s network and the solutions produced by the ANSI X3T11 committee. The first section of the report introduces HIPPI-6400 to familiarize the reader with basic concepts and lay ground work for future sections. Section 2 analyzes the transmission control link-layer embedded in HIPPI-6400 hardware. Section 3 describes the scheduled transfer protocol and connection setup that allows the user to partake of the entire 6400 Mbit bandwidth; followed by section 4 that describes the signaling interface. Section 5 provides an overview of switching requirements and constructs. Finally, section 6 concludes the paper, describes works in progress, including simulation, and points to further reading.

High-accuracy laser power meter

A laser power meter has been developed which can measure absolute power output to better than 0.1%. The power meter has a flat spectral response from ultraviolet to far infrared and is essentially 100% linear over its full dynamic range. The power meter has long term stability better than 0.001% per day. The operation of the power meter is discussed and performance measurement data are presented.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Multispectral power meter

As optical sensor and source technologies advance, it is important to improve the ability to accurately calibrate these sensors and sources. A new type of power meter which has excellent absolute accuracy, long term stability, and linear output over its full dynamic range will be described. The Multispectral Power Meter (MSP) makes direct power measurements by the substitution of electrical power to balance the radiant power from a radiation source. The MSP can operate in air at ambient temperature, in a vacuum environment, or even in space. It monitors ultraviolet to far infrared wavelengths with equal responsivity and can thus measure laser output at any wavelength or blackbodies at any temperature. In addition to characterizing the output from spectral sources, the MSP can also calibrate sensors and act as a transfer standard from a cryogenic primary standard. A digital controller enables the MSP to be remotely operated. The various measurement techniques and the performance levels of the MSP will be described.

Earth Radiation Array (ERA)

The Earth Radiation Array (ERA) represents a new instrument under development for climate research and global monitoring of the earth radiation budget. The ERA contains a mosaic array of detectors which measures the outgoing radiation of the earth in all directions without the need for mechanical scanning. The goal is to eliminate all moving parts and obtain highly calibrated measurements for up to one solar cycle (11 years) without being susceptible to mechanical failure. Over set intervals of time, the angular measurements are integrated up to produce total reflected and emitted flux values from each target area on the earth. To achieve the required sensitivity while maintaining a flat spectral response, an improved dual cavity detector with digital control loop has been developed. The detector is self calibrating to maintain high precision over the life of the instrument. Prototype detectors and a complete set of electronics with a microprocessor controller are currently being fabricated and tested by Space Instruments, Inc ., under contract to NASA/GSFC. Early measurements indicate that the new detectors are more than an order of magnitude more sensitive than previous versions. The design concept for the complete ERA and the status of the hardware development will be presented, along with key test results obtained to date.