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NASA NTRS2008

Astrobiology Sample Analysis Program (ASAP) for Advanced Life Detection Instrumentation Development and Calibration

Scientific ground-truth measurements for near-term Mars missions, such as the 2009 Mars Science Laboratory (MSL) mission, are essential for validating current in situ flight instrumentation and for the development of advanced instrumentation technologies for life-detection missions over the next decade. The NASA Astrobiology Institute (NAI) has recently funded a consortium of researchers called the Astrobiology Sample Analysis Program (ASAP) to analyze an identical set of homogenized martian analog materials in a "round-robin" style using both state-of-the-art laboratory techniques as well as in-situ flight instrumentation including the SAM gas chromatograph mass spectrometer and CHEMIN X-ray diffraction/fluorescence instruments on MSL and the Urey and MOMA organic analyzer instruments under development for the 2013 ExoMars missions. The analog samples studied included an Atacama Desert soil from Chile, the Murchison meteorite, a gypsum sample from the 2007 AMASE Mars analog site, jarosite from Panoche Valley, CA, a hydrothermal sample from Rio Tinto, Spain, and a "blind" sample collected during the 2007 MSL slow-motion field test in New Mexico. Each sample was distributed to the team for analysis to: (1) determine the nature and inventory of organic compounds, (2) measure the bulk carbon and nitrogen isotopic composition, (3) investigate elemental abundances, mineralogy and matrix, and (4) search for biological activity. The experimental results obtained from the ASAP Mars analog research consortium will be used to build a framework for understanding the biogeochemistry of martian analogs, help calibrate current spaceflight instrumentation, and enhance the scientific return from upcoming missions.

Glavin, Daniel↗
NASA NTRS2007

27 Years of Satellite Ozone Data: Merging of Data Records from Multiple Instruments to Observe Global Trends and Recovery

Satellite measurements provide a unique global view of the stratospheric ozone layer. The perspective from satellites allowed for the early mapping of the extent of the phenomenon that became known as the ozone hole. The use of the satellite data for global trends outside of the ozone hole confronts the problem of the possible drift of the calibration of the instrument. The TOMS and SBUV instruments on Nimbus 7 lasted for more than a decade. During that time, the diffuser plate used to reflect sunlight into the measurement degraded (darkened) and the instruments each had a number of events that made calibration determination difficult. Initially the TOMS data were used for global trends by adjusting the overall calibration to agree with a set of ground-based measurement stations. But this was unsatisfactory because the record was not independent of those ground measurements and problems were found in many of the ground stations by using TOMS as a transfer standard. After many years of dedicated work, the TOMS/SBUV team learned how to correct for instrument drift, remove the interfering effects of aerosols, and establish instrument-to-instrument calibrations resulting in a long-term record that can be used for accurate trend and recovery determination. The global view of the satellites allows for determination not only of temporal change in ozone, but spatial fingerprints that allow more confidence in assigning cause to observed changes.

Stolarski, Richard S.↗
NASA NTRS2008

Hyperspectral Fluorescence and Reflectance Imaging Instrument

The system is a single hyperspectral imaging instrument that has the unique capability to acquire both fluorescence and reflectance high-spatial-resolution data that is inherently spatially and spectrally registered. Potential uses of this instrument include plant stress monitoring, counterfeit document detection, biomedical imaging, forensic imaging, and general materials identification. Until now, reflectance and fluorescence spectral imaging have been performed by separate instruments. Neither a reflectance spectral image nor a fluorescence spectral image alone yields as much information about a target surface as does a combination of the two modalities. Before this system was developed, to benefit from this combination, analysts needed to perform time-consuming post-processing efforts to co-register the reflective and fluorescence information. With this instrument, the inherent spatial and spectral registration of the reflectance and fluorescence images minimizes the need for this post-processing step. The main challenge for this technology is to detect the fluorescence signal in the presence of a much stronger reflectance signal. To meet this challenge, the instrument modulates artificial light sources from ultraviolet through the visible to the near-infrared part of the spectrum; in this way, both the reflective and fluorescence signals can be measured through differencing processes to optimize fluorescence and reflectance spectra as needed. The main functional components of the instrument are a hyperspectral imager, an illumination system, and an image-plane scanner. The hyperspectral imager is a one-dimensional (line) imaging spectrometer that includes a spectrally dispersive element and a two-dimensional focal plane detector array. The spectral range of the current imaging spectrometer is between 400 to 1,000 nm, and the wavelength resolution is approximately 3 nm. The illumination system consists of narrowband blue, ultraviolet, and other discrete wavelength light-emitting-diode (LED) sources and white-light LED sources designed to produce consistently spatially stable light. White LEDs provide illumination for the measurement of reflectance spectra, while narrowband blue and UV LEDs are used to excite fluorescence. Each spectral type of LED can be turned on or off depending on the specific remote-sensing process being performed. Uniformity of illumination is achieved by using an array of LEDs and/or an integrating sphere or other diffusing surface. The image plane scanner uses a fore optic with a field of view large enough to provide an entire scan line on the image plane. It builds up a two-dimensional image in pushbroom fashion as the target is scanned across the image plane either by moving the object or moving the fore optic. For fluorescence detection, spectral filtering of a narrowband light illumination source is sometimes necessary to minimize the interference of the source spectrum wings with the fluorescence signal. Spectral filtering is achieved with optical interference filters and absorption glasses. This dual spectral imaging capability will enable the optimization of reflective, fluorescence, and fused datasets as well as a cost-effective design for multispectral imaging solutions. This system has been used in plant stress detection studies and in currency analysis.

Ryan, Robert E.↗
NASA NTRS2008

TES Carbon Monoxide Validation during the Two AVE Campaigns using the Argus and ALIAS Instruments on NASA's WB-57F

The Aura Validation Experiment (AVE) focuses on validating Aura satellite measurements of important atmospheric trace gases using ground-based, aircraft, and balloon-borne instruments. Global satellite observations of CO from the Tropospheric Emission Spectrometer (TES) on the EOS Aura satellite have been ongoing since September 2004. This paper discusses CO validation experiments during the Oct-AVE (2004 Houston, Texas) and CR-AVE (2006 San Jose, Costa Rica) campaigns. The coincidences in location and time between the satellite observations and the available in situ profiles for some cases are not ideal. However, the CO distribution patterns in the two validation flight areas are shown to have very little variability in the aircraft and satellite . observations, thereby making them suitable for validation comparisons. TES CO profiles, which typically have a retrieval uncertainty of 10-20%, are compared with in situ CO measurements from NASA Ames Research Center's Argus instrument taken on board the WB-57F aircraft during Oct-AVE. TES CO retrievals during CR-AVE are compared with in situ measurements from Jet Propulsion Laboratory's Aircraft Laser Infrared Absorption Spectrometer (ALIAS) instrument as well as with the Argus instrument, both taken on board the WB-57F aircraft. During CR-AVE, the average overall difference between ALIAS and Argus CO was 4%, with the ALIAS measurement higher. During individual flights, 2-min time-averaged differences between the two in situ instruments had standard deviation of 14%. The TES averaging kernels and a priori constraint profiles for CO are applied to the in situ data for proper comparisons to account for the reduced vertical resolution and the influence of the a priori in the satellite-derived profile. In the TES sensitive pressure range, approx.700-200 hPa, the in situ profiles and TES profiles agree within 5-10%, less than the variability in CO distributions obtained by both TES and the aircraft instruments in the two regions. TES CO is slightly lower than in situ measurements in the Houston area (midlatitudes) and slightly higher than in situ CO measurements in the Costa Rica region (tropical).

Lopez, Jinena P.↗
NASA NTRS2011

Component-Level Electronic-Assembly Repair (CLEAR) Synthetic Instrument Capabilities Assessment and Test Report

The role of synthetic instruments (SIs) for Component-Level Electronic-Assembly Repair (CLEAR) is to provide an external lower-level diagnostic and functional test capability beyond the built-in-test capabilities of spacecraft electronics. Built-in diagnostics can report faults and symptoms, but isolating the root cause and performing corrective action requires specialized instruments. Often a fault can be revealed by emulating the operation of external hardware. This implies complex hardware that is too massive to be accommodated in spacecraft. The SI strategy is aimed at minimizing complexity and mass by employing highly reconfigurable instruments that perform diagnostics and emulate external functions. In effect, SI can synthesize an instrument on demand. The SI architecture section of this document summarizes the result of a recent program diagnostic and test needs assessment based on the International Space Station. The SI architecture addresses operational issues such as minimizing crew time and crew skill level, and the SI data transactions between the crew and supporting ground engineering searching for the root cause and formulating corrective actions. SI technology is described within a teleoperations framework. The remaining sections describe a lab demonstration intended to show that a single SI circuit could synthesize an instrument in hardware and subsequently clear the hardware and synthesize a completely different instrument on demand. An analysis of the capabilities and limitations of commercially available SI hardware and programming tools is included. Future work in SI technology is also described.

Oeftering, Richard C.↗
NASA NTRS2011

Virtual Sensor Test Instrumentation

Virtual Sensor Test Instrumentation is based on the concept of smart sensor technology for testing with intelligence needed to perform sell-diagnosis of health, and to participate in a hierarchy of health determination at sensor, process, and system levels. A virtual sensor test instrumentation consists of five elements: (1) a common sensor interface, (2) microprocessor, (3) wireless interface, (4) signal conditioning and ADC/DAC (analog-to-digital conversion/ digital-to-analog conversion), and (5) onboard EEPROM (electrically erasable programmable read-only memory) for metadata storage and executable software to create powerful, scalable, reconfigurable, and reliable embedded and distributed test instruments. In order to maximize the efficient data conversion through the smart sensor node, plug-and-play functionality is required to interface with traditional sensors to enhance their identity and capabilities for data processing and communications. Virtual sensor test instrumentation can be accessible wirelessly via a Network Capable Application Processor (NCAP) or a Smart Transducer Interlace Module (STIM) that may be managed under real-time rule engines for mission-critical applications. The transducer senses the physical quantity being measured and converts it into an electrical signal. The signal is fed to an A/D converter, and is ready for use by the processor to execute functional transformation based on the sensor characteristics stored in a Transducer Electronic Data Sheet (TEDS). Virtual sensor test instrumentation is built upon an open-system architecture with standardized protocol modules/stacks to interface with industry standards and commonly used software. One major benefit for deploying the virtual sensor test instrumentation is the ability, through a plug-and-play common interface, to convert raw sensor data in either analog or digital form, to an IEEE 1451 standard-based smart sensor, which has instructions to program sensors for a wide variety of functions. The sensor data is processed in a distributed fashion across the network, providing a large pool of resources in real time to meet stringent latency requirements.

Wang, Roy↗
NASA NTRS2004

Multifunction Imaging and Spectroscopic Instrument

A proposed optoelectronic instrument would perform several different spectroscopic and imaging functions that, heretofore, have been performed by separate instruments. The functions would be reflectance, fluorescence, and Raman spectroscopies; variable-color confocal imaging at two different resolutions; and wide-field color imaging. The instrument was conceived for use in examination of minerals on remote planets. It could also be used on Earth to characterize material specimens. The conceptual design of the instrument emphasizes compactness and economy, to be achieved largely through sharing of components among subsystems that perform different imaging and spectrometric functions. The input optics for the various functions would be mounted in a single optical head. With the exception of a targeting lens, the input optics would all be aimed at the same spot on a specimen, thereby both (1) eliminating the need to reposition the specimen to perform different imaging and/or spectroscopic observations and (2) ensuring that data from such observations can be correlated with respect to known positions on the specimen. The figure schematically depicts the principal components and subsystems of the instrument. The targeting lens would collect light into a multimode optical fiber, which would guide the light through a fiber-selection switch to a reflection/ fluorescence spectrometer. The switch would have four positions, enabling selection of spectrometer input from the targeting lens, from either of one or two multimode optical fibers coming from a reflectance/fluorescence- microspectrometer optical head, or from a dark calibration position (no fiber). The switch would be the only moving part within the instrument.

Mouroulis, Pantazis↗
NASA NTRS2004

Position-Finding Instrument Built Around a Magnetometer

A coarse-positioning instrument is built around a three-axis magnetometer. The magnetometer is of a type that is made of inexpensive hardware and is suitable for use aboard spacecraft orbiting no more than 1,000 km above the surface of the Earth. A data processor programmed with suitable software and equipped with a central processing unit, random-access memory, programmable read-only memory, and interface circuitry for communication with external equipment are added to the basic magnetometer to convert it into a coarse-positioning instrument. Although the instrument was conceived for use aboard spacecraft, it could be useful for navigation on Earth under some circumstances. A major feature of the proposed instrument is an ability to generate a coarse estimate of its position in real time (that is, without start-up delay). Algorithms needed to solve the position equations have been developed. These include algorithms to work around gaps in measurement data that arise from a singularity near the minimum in the magnetic field of the Earth. Some work has been done to develop a prototype of this instrument incorporating a standard three-axis flux-gate magnetometer and a Pentium P-5 (or equivalent) processor with a clock frequency of 120 MHz. Alternatively, the processor could be of the 486 class. A computer model of the instrument has been completed and tested.

Ketchum, Eleanor↗
NASA NTRS2011

Reconciling Simulated and Observed Views of Clouds: MODIS, ISCCP, and the Limits or Instrument Simulators

The properties of clouds that may be observed by satellite instruments, such as optical depth and cloud top pressure, are only loosely related to the way clouds m-e represented in models of the atmosphere. One way to bridge this gap is through "instrument simulators," diagnostic tools that map the model representation to synthetic observations so that differences between simulator output and observations can be interpreted unambiguously as model error. But simulators may themselves be restricted by limited information available from the host model or by internal assumptions. This paper considers the extent to which instrument simulators are able to capture essential differences between MODIS and ISCCP, two similar but independent estimates of cloud properties. The authors review the measurements and algorithms underlying these two cloud climatologies, introduce a MODIS simulator, and detail data sets developed for comparison with global models using ISCCP and MODIS simulators, In nature MODIS observes less mid-level doudines!> than ISCCP, consistent with the different methods used to determine cloud top pressure; aspects of this difference are reproduced by the simulators running in a climate modeL But stark differences between MODIS and ISCCP observations of total cloudiness and the distribution of cloud optical thickness can be traced to different approaches to marginal pixels, which MODIS excludes and ISCCP treats as homogeneous. These pixels, which likely contain broken clouds, cover about 15 k of the planet and contain almost all of the optically thinnest clouds observed by either instrument. Instrument simulators can not reproduce these differences because the host model does not consider unresolved spatial scales and so can not produce broken pixels. Nonetheless, MODIS and ISCCP observation are consistent for all but the optically-thinnest clouds, and models can be robustly evaluated using instrument simulators by excluding ambiguous observations.

Ackerman, Steven A.↗
NASA NTRS1970

Backscatter Ultraviolet (BUV) Instrument

This final project report covers the design, development, construction, testing and qualification of the NIMBUS D BUV (Backscatter Ultraviolet) instrument. The instrument was designed and constructed in accordance with GSFC specification S-623-P-l and amendments. The design phase consisted of activity in three areas of technology: (1) Optical, (2) Mechanical, and (3) Electrical. Beckman Instruments, Inc. performed the tasks concerned with optical and mechanical design while Analog Technology Corporation was the electronics subcontractor. Initial studies resulted in the development of a breadboard model of the BUV instrument. Following extensive testing, additional mathematical analyses, and required modifications, preliminary and critical design reviews were performed. The results of these activities were the construction of an engineering model, used for extensive testing and demonstration of the final design features. Final design data resulted in the construction of two flight-rated instruments, serial numbers P103 and Fl04. On April 8, 1970, the P103 instrument was successfully launched into orbit on NIMBUS D and is presently fully operational.

Source record↗
NASA NTRS2011

Reconciling Simulated and Observed Views of Clouds: MODIS, ISCCP, and the Limits of Instrument Simulators in Climate Models

The properties of clouds that may be observed by satellite instruments, such as optical depth and cloud top pressure, are only loosely related to the way clouds are represented in models of the atmosphere. One way to bridge this gap is through "instrument simulators," diagnostic tools that map the model representation to synthetic observations so that differences between simulator output and observations can be interpreted unambiguously as model error. But simulators may themselves be restricted by limited information available from the host model or by internal assumptions. This work examines the extent to which instrument simulators are able to capture essential differences between MODIS and ISCCP, two similar but independent estimates of cloud properties. We focus on the stark differences between MODIS and ISCCP observations of total cloudiness and the distribution of cloud optical thickness can be traced to different approaches to marginal pixels, which MODIS excludes and ISCCP treats as homogeneous. These pixels, which likely contain broken clouds, cover about 15% of the planet and contain almost all of the optically thinnest clouds observed by either instrument. Instrument simulators can not reproduce these differences because the host model does not consider unresolved spatial scales and so can not produce broken pixels. Nonetheless, MODIS and ISCCP observation are consistent for all but the optically-thinnest clouds, and models can be robustly evaluated using instrument simulators by excluding ambiguous observations.

Pincus, Robert↗
NASA NTRS2012

Increased Science Instrumentation Funding Strengthens Mars Program

As the strategic knowledge gaps mature for the exploration of Mars, Mars sample return (MSR), and Phobos/Deimos missions, one approach that becomes more probable involves smaller science instrumentation and integrated science suites. Recent technological advances provide the foundation for a significant evolution of instrumentation; however, the funding support is currently too small to fully utilize these advances. We propose that an increase in funding for instrumentation development occur in the near-term so that these foundational technologies can be applied. These instruments would directly address the significant knowledge gaps for humans to Mars orbit, humans to the Martian surface, and humans to Phobos/ Deimos. They would also address the topics covered by the Decadal Survey and the Mars scientific goals, objectives, investigations and priorities as stated by the MEPAG. We argue that an increase of science instrumentation funding would be of great benefit to the Mars program as well as the potential for human exploration of the Mars system. If the total non-Earth-related planetary science instrumentation budget were increased 100% it would not add an appreciable amount to the overall NASA budget and would provide the real potential for future breakthroughs. If such an approach were implemented in the near-term, NASA would benefit greatly in terms of science knowledge of the Mars, Phobos/Deimos system, exploration risk mitigation, technology development, and public interest.

Graham, Lee D.↗
NASA NTRS2012

Development of a Compact, Deep-Penetrating Heat Flow Instrument for Lunar Landers: In-Situ Thermal Conductivity System

Geothermal heat flow is obtained as a product of the geothermal gradient and the thermal conductivity of the vertical soil/rock/regolith interval penetrated by the instrument. Heat flow measurements are a high priority for the geophysical network missions to the Moon recommended by the latest Decadal Survey and previously the International Lunar Network. One of the difficulties associated with lunar heat flow measurement on a robotic mission is that it requires excavation of a relatively deep (approx 3 m) hole in order to avoid the long-term temporal changes in lunar surface thermal environment affecting the subsurface temperature measurements. Such changes may be due to the 18.6-year-cylcle lunar precession, or may be initiated by presence of the lander itself. Therefore, a key science requirement for heat flow instruments for future lunar missions is to penetrate 3 m into the regolith and to measure both thermal gradient and thermal conductivity. Engineering requirements are that the instrument itself has minimal impact on the subsurface thermal regime and that it must be a low-mass and low-power system like any other science instrumentation on planetary landers. It would be very difficult to meet the engineering requirements, if the instrument utilizes a long (> 3 m) probe driven into the ground by a rotary or percussive drill. Here we report progress in our efforts to develop a new, compact lunar heat flow instrumentation that meets all of these science and engineering requirements.

Nagihara, S.↗
NASA NTRS2014

Using Lunar Observations to Validate Pointing Accuracy and Geolocation, Detector Sensitivity Stability and Static Point Response of the CERES Instruments

Validation of in-orbit instrument performance is a function of stability in both instrument and calibration source. This paper describes a method using lunar observations scanning near full moon by the Clouds and Earth Radiant Energy System (CERES) instruments. The Moon offers an external source whose signal variance is predictable and non-degrading. From 2006 to present, these in-orbit observations have become standardized and compiled for the Flight Models -1 and -2 aboard the Terra satellite, for Flight Models-3 and -4 aboard the Aqua satellite, and beginning 2012, for Flight Model-5 aboard Suomi-NPP. Instrument performance measurements studied are detector sensitivity stability, pointing accuracy and static detector point response function. This validation method also shows trends per CERES data channel of 0.8% per decade or less for Flight Models 1-4. Using instrument gimbal data and computed lunar position, the pointing error of each detector telescope, the accuracy and consistency of the alignment between the detectors can be determined. The maximum pointing error was 0.2 Deg. in azimuth and 0.17 Deg. in elevation which corresponds to an error in geolocation near nadir of 2.09 km. With the exception of one detector, all instruments were found to have consistent detector alignment from 2006 to present. All alignment error was within 0.1o with most detector telescopes showing a consistent alignment offset of less than 0.02 Deg.

Daniels, Janet L.↗
NASA NTRS2012

Guidelines for Successful Use and Communication of Instrument Heritage in Early Mission Development with a Focus on Spectrometers

Heritage is important for both cost and risk related issues and as such, it is heavily discussed in NASA proposal evaluations. If used and communicated efficiently, heritage can lower both the perception of risk and the associated costs. Definitions of heritage vary between engineering, cost, and scientific communities, but when applied appropriately, heritage provides a benefit to the proposed mission. By making an instrument at least once before, the cost of producing it again can be reduced. The time and effort needed to develop the instrument concept and test the product represent an expense that can be lowered through the use of a previously built and developed instrument. This same thought can be applied when using a flight spare or build-to-print model of the heritage instrument. The lowered perception of risk is a result of the confidence gained in the instrument through successful use in the target environment. This is extremely important in early mission development to the evaluation board. This analysis will use JPL-managed proposals from 2003 to 2011, including Discovery, New Frontiers, and Mars Scout missions. Through the examination of these proposals and their associated debriefs, a set of guidelines have been created for successful use and communication of instrument heritage in early mission development

specrtometers↗
NASA NTRS2011

The Planned Soil Moisture Active Passive (SMAP) Mission L-Band Radar/Radiometer Instrument

The Soil Moisture Active/Passive (SMAP) mission is a NASA mission identified by the NRC 'decadal survey' to measure both soil moisture and freeze/thaw state from space. The mission will use both active radar and passive radiometer instruments at L-Band. In order to achieve a wide swath at sufficiently high resolution for both active and passive channels, an instrument architecture that uses a large rotating reflector is employed. The instrument system has completed the preliminary design review (PDR) stage, and detailed instrument design has begun. In addition to providing an overview of the instrument design, two recent design modifications are discussed: 1) The addition of active thermal control to the instrument spun side to provide a more stable, settable thermal environment for the radiometer electronics, and 2) A 'sequential transmit' strategy for the two radar polarization channels which allows a single high-power amplifier to be used.

radiometer↗
NASA NTRS2011

On-Orbit Performance of the TES Pulse Tube Cryocooler System and the Instrument - Six Years in Space

The Tropospheric Emission Spectrometer (TES) instrument pulse tube cryocoolers began operation 36 days after launch of the NASA Earth Observing System (EOS) Aura spacecraft on July 15, 2004. TES is designed with four infrared Mercury Cadmium Telluride focal plane arrays in two separate housings cooled by a pair of Northrup Grumman Aerospace Systems (NGAS) single-stage pulse tube cryocoolers. The instrument also makes use of a two-stage passive cooler to cool the optical bench. The instrument is a high-resolution infrared imaging Fourier transform spectrometer with 3.3-15.4 micron spectral coverage. After four weeks of outgassing, the instrument optical bench and focal planes were cooled to their operating temperatures to begin science operations. During the early months of the mission, ice contamination of the cryogenic surfaces including the focal planes led to increased cryocooler loads and the need for periodic decontamination cycles. After a highly successful 5 years of continuous in-space operations, TES was granted a 2 year extension. This paper reports on the TES cryogenic system performance including the two-stage passive cooler. After a brief overview of the cryogenic design, the paper presents detailed data on the highly successful space operation of the pulse tube cryocoolers and instrument thermal design over the past six years since the original turn-on in 2004. The data shows the cryogenic contamination decreased substantially to where decontamination cycles are now performed every six months. The cooler stroke required for constant-temperature operation has not increased indicating near-constant cooler efficiency and the instrument's thermal design has also provided a nearly constant heat rejection sink. At this time TES continues to operate in space providing important Earth science data.

cryocoolercraft↗
NASA NTRS2012

The Process of Developing a Multi-Cell KEMS Instrument

Multi-cell KEMS offers many advantages over single cell instruments in regard to in-situ temperature calibration and studies on high temperature alloys and oxides of interest to NASA. The instrument at NASA Glenn is a 90 deg magnetic sector instrument originally designed for single cell operation. The conversion of this instrument to a multi-cell instrument with restricted collimation is discussed. For restricted collimation, the 'field aperture' is in the copper plate separating the Knudsen Cell region and the ionizer and the 'source aperture' is adjacent to the ionizer box. A computer controlled x-y table allows positioning of one of the three cells into the sampling region. Heating is accomplished via a Ta sheet element and temperature is measured via an automatic pyrometer from the bottom of the cells. The computer control and data system have been custom developed for this instrument and are discussed. Future improvements are also discussed.

Copland, E. H.↗