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NASA NTRSDate not supplied

Senteniel-6 Radio Occultation Product Released by NASA GES DISC to Supplement Satellite Remote Sensing Datasets for PBL Study

The NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) curates hyperspectral atmospheric sounder remote sensing and numerical model reanalysis datasets which have been utilized in the Planetary Boundary Layer (PBL) research and applications. The hyperspectral sounder remote-sensing datasets include the Atmospheric Infrared Sounder (AIRS) on the Aqua satellite to the Cross-track Infrared Sounder (CrIS) on Suomi--National Polar- orbiting Partnership (NPP) and National Oceanic and Atmospheric Administration -20 (N NOAA-20)/ Joint Polar-orbiting Satellite System -1 (JPSS-1). The Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) global reanalysis product provides a data record commencing in 1980. The sounder remote sensing and reanalysis datasets include temperature, water vapor, and trace gas profile down to the PBL, and also have a derived PBL height as well. A nearly 10-year (June 2006 to December 2015) seasonal and annual PBL height climatology dataset from COSMIC Global Navigation Satellite System (GNSS) radio occultation (RO) measurement is also available from the GES DISC. In collaboration with Sentinel-6 Project, the GES DISC is implementing curation activities for GNSS RO products from the Sentinel-6A/Sentinel-6 Michael Freilich satellite launched on November 21, 2020. Sentinel-6A RO products provide refractivity, temperature, and humidity profile with finer vertical resolution, leveraging PBL research and application as a supplement to the hyperspectral sounder remote sensing and reanalysis products. The public release of Sentinel- 6A RO products is scheduled for mid-October of 2021. In this presentation, we will introduce all Senitnel-6A products and services, and demonstrate use cases studying the PBL by combining these products with other GES DISC archived data products.

Feng Ding↗
NASA NTRS1993

Electrical power technology for robotic planetary rovers

Power technologies which will enable a range of robotic rover vehicle missions by the end of the 1990s and beyond are discussed. The electrical power system is the most critical system for reliability and life, since all other on board functions (mobility, navigation, command and data, communications, and the scientific payload instruments) require electrical power. The following are discussed: power generation, energy storage, power management and distribution, and thermal management.

Bankston, C. P.↗
NASA NTRS1996

Ultralight Fabric Reflux Tube (UFRT) Thermal/Vacuum Test

Spacecraft thermal control systems are essential to provide the necessary environment for the crew and equipment to function adequately on space missions. The Ultralight Fabric Reflux Tube (UFRT) was developed by Pacific Northwest Laboratory (PNL) as a lightweight radiator concept to be used on planetary-type missions (e.g., Moon, Mars). The UFRT consists of a thin-walled tube (acting as the fluid boundary), overwrapped with a low-mass ceramic fabric (acting as the primary pressure boundary). The tubes are placed in an array in the vertical position with the evaporators at the lower end. Heat is added to the evaporators, which vaporizes the working fluid. The vapor travels to the condenser end above and cools as heat is radiated to the environment. The fluid condensed on the tube wall is then returned to the evaporator by gravity. The primary objectives for the fiscal year 1994 program included the design and fabrication of prototype UFRTs and thermal/vacuum chamber testing of these test articles. Six UFRTS, with improved titanium liners, were successfully manufactured and provided to the Johnson Space Center in July 1994. Five were tested in a thermal/vacuum chamber in September 1994. Data obtained to characterize the performance of the UFRTs under simulated lunar conditions demonstrated the design concept successfully. In addition, a trade study showed that an optimized/improved UFRT could achieve as much as a 25% mass savings in the heat rejection subsystem of future planetary-type thermal control systems.

Hurlbert, K. M.↗
NASA NTRS1993

Imaging spectrometry of the Earth and other solar system bodies

Imaging spectrometry is a relatively new tool for remote sensing of the Earth and other bodies of the solar system. The technique dates back to the late 1970's and early 1980's. It is a natural extension of the earlier multi-spectral imagers developed for remote sensing that acquire images in a few, usually broad spectral bands. Imaging spectrometers combine aspects of classical spectrometers and imaging systems, making it possible to acquire literally hundreds of images of an object, each image in a separate, narrow spectral band. It is thus possible to perform spectroscopy on a pixel-by-pixel basis with the data acquired with an imaging spectrometer. Two imaging spectrometers have flown in space and several others are planned for future Earth and planetary missions. The French-built Phobos Infrared Spectrometer (ISM) was part of the payload of the Soviet Mars mission in 1988, and the JPL-built Near Infrared Mapping Spectrometer (NIMS) is currently en route to Jupiter aboard the Galileo spacecraft. Several airborne imaging spectrometers have been built in the past decade including the JPL-built Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) which is the only such sensor that covers the full solar reflected portion of the spectrum in narrow, contiguous spectral bands. NASA plans two imaging spectrometers for its Earth Observing System, the Moderate and the High Resolution Imaging Spectrometers (MODIS and HIRIS). A brief overview of the applications of imaging spectrometry to Earth science will be presented to illustrate the value of the tool to remote sensing and indicate the types of measurements that are required. The system design for AVIRS and a planetary imaging spectrometer will be presented to illustrate the engineering considerations and challenges that must be met in building such instruments. Several key sensor technology areas will be discussed in which miniaturization and/or enhanced performance through micromachining and nanofabrication may allow smaller, more robust, and more capable imaging spectrometers to be built in the future.

Vane, Gregg↗
NASA NTRS2020

The Science Enabled by a Dedicated Solar System Space Telescope

The National Academy Committee on Astrobiology and Planetary Science (CAPS) made a recommendation to study a large/medium-class dedicated space telescope for planetary science, going beyond the Discovery-class dedicated planetary space telescope endorsed in Visions and Voyages. Such a telescope would observe targets across the entire solar system, engaging a broad spectrum of the science community. It would ensure that the high-resolution, high-sensitivity observations of the solar system in visible and UV wavelengths revolutionized by the Hubble Space Telescope could be extended. A dedicated telescope for solar system science would a) transform our understanding of time-dependent phenomena in our solar system that cannot be studied currently under programs to observe and visit new targets and b) enable a comprehensive survey and spectral characterization of minor bodies across the solar system, which requires a large time allocation not supported by existing facilities. The time-domain phenomena to be explored are critically reliant on UV observations and include: interaction of planetary magnetospheres with the solar wind and internal plasma sources, Venus and giant planet atmospheric dynamics, icy satellite geologic activity and surface evolution, cometary evolution, and evolving ring phenomena. This paper presents science themes and key questions that require a long-lasting space telescope dedicated to planetary science that can capture high-quality, consistent data at the required cadences that are free from the complicating effects of the terrestrial atmosphere and differences across observing facilities. Such a telescope would have excellent synergy with astrophysical facilities by placing planetary discoveries made by astrophysics assets in temporal context, as well as triggering detailed follow-up observations using larger telescopes. The telescope would also support future missions to the Ice Giants, Ocean Worlds, and minor bodies across the solar system by placing the results of such targeted missions in the context of longer records of temporal activities and larger sample populations.

C. L. Young↗
DOE OSTI2020

Transits of Known Planets Orbiting a Naked-eye Star

Some of the most scientifically valuable transiting planets are those that were already known from radial velocity (RV) surveys. This is primarily because their orbits are well characterized and they preferentially orbit bright stars that are the targets of RV surveys. The Transiting Exoplanet Survey Satellite (TESS) provides an opportunity to survey most of the known exoplanet systems in a systematic fashion to detect possible transits of their planets. HD 136352 (Nu{sup 2} Lupi) is a naked-eye (V = 5.78) G-type main-sequence star that was discovered to host three planets with orbital periods of 11.6, 27.6, and 108.1 days via RV monitoring with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph. We present the detection and characterization of transits for the two inner planets of the HD 136352 system, revealing radii of 1.482{sub −0.056}{sup +0.058} R {sub ⊕} and 2.608{sub −0.077}{sup +0.078} R {sub ⊕} for planets b and c, respectively. We combine new HARPS observations with RV data from the Keck/High Resolution Echelle Spectrometer and the Anglo-Australian Telescope, along with TESS photometry from Sector 12, to perform a complete analysis of the system parameters. The combined data analysis results in extracted bulk density values of ρ{sub b}=7.8{sub −1.1}{sup +1.2} g cm{sup −3} and ρ{sub c}=3.50{sub −0.36}{sup +0.41} g cm{sup −3} for planets b and c, respectively, thus placing them on either side of the radius valley. The combination of the multitransiting planet system, the bright host star, and the diversity of planetary interiors and atmospheres means this will likely become a cornerstone system for atmospheric and orbital characterization of small worlds.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1967

The Effect of Planetary Albedo on Solar Orientation of Spacecraft

The analytical expression for the solar orientation error caused by planetary albedo is derived. A typical solar sensor output characteristic is assumed and a computer solution to the analytical is obtained. The computer results are presented for a spacecraft in the vicinity of Earth, Venus, Mars, and the Moon. Each planetary body is assumed to be a spherical diffuse reflector with cylindrical shadows and a constant albedo. The data generated herein permit the selection of an appropriate coarse-sensor to fine-sensor switching angle for solar orientation control systems and facilitate the the interpretation of solar-referenced scientific experiment data.

SPACE ORIENTATION↗
NASA NTRS1984

The Io decametric emission cone

The Voyager 1 and 2 Planetary Radio Astronomy observations of Jovian decametric radiation (DAM) were transformed into a fixed Io-Jupiter coordinate system for Io longitudes every 10 deg apart starting from 200 to 260 deg (seven plots per spacecaft). An analysis of the data in this coordinate system has shown that the Io-dependent DAM emissions are generated in hollow cones at all frequencies over the fixed Io longitudes studied. The edges of the emission cones are, in many cases, broad in longitude (30 deg or more), with distinct differences found between the characteristics of DAM emission at the edges of the emission cones. The shapes of the DAM emission cones are explained by using three-dimensional ray-tracing calculations within a model Jovian atmosphere.

Green, J. L.↗
NASA NTRS1988

Spaceborne radar remote sensing: Applications and techniques

The operation and applications of spaceborne radars for terrestrial and planetary remote sensing are described in an introduction for advanced students and practicing scientists. Chapters are devoted to imaging radars, wave-surface interactions and geoscientific applications, real- and synthetic-aperture radars, end-to-end system design, SAR data processing, altimeters, and scatterometers. Extensive diagrams, drawings, graphs, photographs, and sample radar images are provided.

Elachi, Charles↗
NASA NTRS1994

The NASA Ames Closed Environmental Research Chamber: Present Status

The Closed Environmental Research Chamber (CERC) at the NASA Ames Research Center was created to investigate both components and complete systems for life support of advanced space exploration missions. This facility includes a Main Chamber, an Airlock, a Sample Transfer Lock, a Vacuum System, an Air Recompression System, a dedicated control room and a pit area for housing supporting and environmental control systems. The Main Chamber provides 310 sq ft of internal working/living space on two levels. It is planned that the CERC will be a human-rated facility for habitation simulation under mass balance closure conditions. The internal pressure will be variable over the range of 14.7 psia to 5 psia with accompanying capability for variation in atmosphere composition to maintain the oxygen partial pressure at 160 mm Hg. The CERC will be provided with a core set of primary life support subsystems for temperature and humidity control, C02 removal and trace contaminant control. Interfacing with external life support technology test b~ds with be provided, along with connection to centralized, microprocessor-based data acquisition and control systems. This paper will discuss the current status of the CERC facility and show how it is being used to address the advanced technology requirements necessary to implement an integrated working and living environment for a planetary habitat. In particular, it will be shown how the CERC, along with a human-powered centrifuge, a planetary terrain simulator and advanced displays and a virtual reality capability will work together to develop and demonstration applicable technologies for future planetary habitats. Artificial intelligence and expert system programming techniques will be used extensively to provide an automated environment for a 4-person crew. There will be several robotic mechanisms performing exploration tasks external to the habitat that will be controlled through the virtual environment to provide representative workloads for the crew. Finally, there will be a discussion of how effective are innovative new multidisciplinary test facilities to the investigation of the wide range of human and machine problems inherent in exploration missions.

Gross, Anthony R.↗
NASA NTRS2004

A Subsurface Soil Composition and Physical Properties Experiment to Address Mars Regolith Stratigraphy

Previous in-situ measurements of soil-like materials on the surface of Mars, in particular during the on-going Mars Exploration Rover missions, have shown complex relationships between composition, exposure to the surface environment, texture, and local rocks. In particular, a diversity in both compositional and physical properties could be established that is interpreted to be diagnostic of the complex geologic history of the martian surface layer. Physical and chemical properties vary laterally and vertically, providing insight into the composition of rocks from which soils derive, and environmental conditions that led to soil formation. They are central to understanding whether habitable environments existed on Mars in the distant past. An instrument the Mole for Soil Compositional Studies and Sampling (MOCSS) - is proposed to allow repeated access to subsurface regolith on Mars to depths of up to 1.5 meters for in-situ measurements of elemental composition and of physical and thermophysical properties, as well as for subsurface sample acquisition. MOCSS is based on the compact PLUTO (PLanetary Underground TOol) Mole system developed for the Beagle 2 lander and incorporates a small X-ray fluorescence spectrometer within the Mole which is a new development. Overall MOCSS mass is approximately 1.4 kilograms. Taken together, the MOCSS science data support to decipher the geologic history at the landing site as compositional and textural stratigraphy if they exist - can be detected at a number of places if the MOCSS were accommodated on a rover such as MSL. Based on uncovered stratigraphy, the regional sequence of depositional and erosional styles can be constrained which has an impact on understanding the ancient history of the Martian near-surface layer, considering estimates of Mars soil production rates of 0.5... 1.0 meters per billion years on the one hand and Mole subsurface access capability of approximately 1.5 meters. An overview of the MOCSS, XRS instrument accomodation and the impact that these instruments have on Mars science is discussed.

Richter, L.↗
NASA NTRSDate not supplied

Results of a 3-day Pilot Study to Validate Planetary Prebreathe Protocols Using a 56.5 kPa 34% O2, 66% N2 Saturation Cabin Atmosphere

INTRODUCTION: Apollo missions used 100% O2 cabin atmospheres which effectively eliminated the risk of decompression sickness (DCS) during extravehicular activities (EVAs, ‘spacewalks’); however, this atmosphere presented a flammability risk that is no longer acceptable to NASA. Denitrogenation prebreathe protocols used to mitigate DCS risk for Space Shuttle and International Space Station EVAs are validated for the microgravity environment, but the significantly increased risk of DCS during equivalent ambulatory surface EVAs make these protocols inapplicable to planetary/Lunar missions. An “exploration atmosphere” of 56.5 kPa (8.2 psia), 34% O2, 66% N2 has been recommended by NASA for future Moon and Mars missions as a compromise that balances subsequent pre-EVA prebreathe duration, hypoxia, and flammability risk, assuming a 29.6 kPa (4.3 psi) spacesuit. Prebreathe validation studies was initiated utilizing a three-story 6m diameter hypobaric chamber at NASA’s Johnson Space Center. Here, we report the results of a 3-day human-in-the-loop system checkout. METHODS: Six volunteers acclimated to the 56.6kPa/34% O2 66% N2 environment for 48hrs prior to conducting a 20-minute prebreathe and a 6-hour simulated EVA at 34kPa/85% O2 / 15% N2. The EVA simulation was designed to include tasks that are physically and ergonomically representative of future planetary EVAs. Decompression stress was evaluated by serial doppler and echocardiographs, as well as by clinical features of DCS signs/symptoms. RESULTS AND DISCUSSION: Preliminary data analysis noted venous gas emboli (VGE) in 3 of 6 subjects, with peak Grade II VGE by Doppler and peak E-B score of 5 by cardiac ultrasonography. No volunteers were diagnosed with DCS during this initial test. No acute hypoxic symptoms were noted. Musculoskeletal and gastrointestinal complaints were noted, likely associated with the exercise load and the food system. Validation of exploration prebreathe protocols has since been initiated with an 11-day saturation test using the same facility and protocol.

Alejandro Garbino↗
NASA NTRS2017

Extratropical Weather Systems on Mars: Radiatively-Active Water Ice Effects

Extratropical, large-scale weather disturbances, namely transient, synoptic-period,baroclinic barotropic eddies - or - low- (high-) pressure cyclones (anticyclones), are components fundamental to global circulation patterns for rapidly rotating, differentially heated, shallow atmospheres such as Earth and Mars. Such "wave-like" disturbances that arise via (geophysical) fluid shear instability develop, mature and decay, and travel west-to-east in the middle and high latitudes within terrestrial-like planetary atmospheres. These disturbances serve as critical agents in the transport of heat and momentum between low and high latitudes of the planet. Moreover, they transport trace species within the atmosphere (e.g., water vapor/ice, other aerosols (dust), chemical species, etc). Between early autumn through early spring, middle and high latitudes on Mars exhibit strong equator-to-pole mean temperature contrasts (i.e., "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that such strong baroclinicity supports vigorous, large-scale eastward traveling weather systems [Banfield et al., 2004; Barnes et al., 1993]. A good example of traveling weather systems, frontal wave activity and sequestered dust activity from MGS/MOC image analyses is provided in Figure 1 (cf. Wang et al. [2005]). Utilizing an upgraded and evolving version of the NASA Ames Research Center (ARC) Mars global climate model, investigated here are key dynamical and physical aspects of simulated northern hemisphere (NH) large-scale extratropica lweather systems,with and without radiatively-active water ice clouds. Mars Climate Model:

cyclones↗
DOE OSTI2020

Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a T = 9.9 mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore 35$_{-5}^{+11}$ million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color–magnitude diagram, we find that the planet has an orbital period of 8.3 days and is slightly smaller than Jupiter (R p =0.77$_{-0.07}^{+0.09}$ R Jup ). From radial velocity monitoring, we limit M p sin i to less than 1.20 M Jup (3σ). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false-positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multicolor photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI 837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1996

A matched filter method for ground-based sub-noise detection of terrestrial extrasolar planets in eclipsing binaries: application to CM Draconis

The photometric detection of extrasolar planets by transits in eclipsing binary systems can be significantly improved by cross-correlating the observational light curves with synthetic models of possible planetary transit features, essentially a matched filter approach. We demonstrate the utility and application of this transit detection algorithm for ground-based detections of terrestrial-sized (Earth-to-Neptune radii) extrasolar planets in the dwarf M-star eclipsing binary system CM Draconis. Preliminary photometric observational data of this system demonstrate that the observational noise is well characterized as white and Gaussian at the observational time steps required for precision photometric measurements. Depending on planet formation scenarios, terrestrial-sized planets may form quite close to this low-luminosity system. We demonstrate, for example, that planets as small as 1.4 Earth radii with periods on the order of a few months in the CM Draconis system could be detected at the 99.9% confidence level in less than a year using 1-m class telescopes from the ground. This result contradicts commonly held assumptions limiting present ground-based efforts to, at best, detections of gas giant planets after several years of observation. This method can be readily extended to a number of other larger star systems with the utilization of larger telescopes and longer observing times. Its extension to spacecraft observations should also allow the determination of the presence of terrestrial-sized planets in nearly 100 other known eclipsing binary systems.

NASA Discipline Number 52-10↗
NASA NTRS2020

TOI-257b (HD 19916b): a warm sub-saturn orbiting an evolved F-type star

We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA’s Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of M(P) = 0.138 ± 0.023 M(J) (43.9 ± 7.3 Mꚛ), a radius of R(P) = 0.639 ± 0.013 R(J) (7.16 ± 0.15 Rꚛ⁠), bulk density of 0.65 (+0.12,−0.11) (cgs), and period 18.38818 (+0.00085,−0.00084) days⁠. TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M⁎ = 1.390 ± 0.046 M(sun)⁠, R⁎ = 1.888 ± 0.033 R(sun)⁠, T(eff) = 6075 ± 90 K⁠, and 𝜈sin 𝑖 = 11.3 ± 0.5 km/s. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems.

asteroseismology↗
NASA NTRS2020

Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a T = 9.9 mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore 35(sup +11)(sub -5) million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color–magnitude diagram, we find that the planet has an orbital period of 8.3 days and is slightly smaller than Jupiter (R(sub p) = 0.77(sup + 0.09)(sub -0.07) R(sub Jup)). From radial velocity monitoring, we limit M(sub p) sin i to less than 1.20 M(sub Jup) (3σ). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false-positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multicolor photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI 837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time.

Exoplanets↗
NASA NTRS2001

Performance Testing of a Lightweight, High Efficiency 95 K Cryocooler

Performance data are presented for a flight-like, lightweight, high efficiency pulse tube cryogenic cooler. The cooler has a mass of less than 4.0 kg, and an efficiency of 12 W/W, which is 18% of Carnot at 95 K, nearly double the efficiency of previous cooler designs, The mass of the cooler has been reduced by approximately a factor of three. The design point cooling power is 10 watts at 95 K at a heat rejection temperature of 300 K. The no-load temperature is 45 K. The compressor is built by Hymatic Engineering, UK, and is of a horizontally opposed piston design using flexure bearings. The vertical pulse tube is built by TRW with the heat exchanger or cold block located approximately mid-way along the tube. The final assembly and integration is also performed by TRW. The inertance tube and dead volume are contained within one of the compressor end caps. The cooler was developed by TRW under a joint NASA-DOD program, and has a goal of 10 yr operating lifetime. Potential NASA applications will focus on using coolers of this type in Zero boil off (ZBO) cryogen storage topologies for next generation launch vehicles. Zero boil off systems will feature significant reductions in tank size and Initial Mass to Low Earth Orbit (IMLEO), thereby significantly reducing the cost of access to space, and enabling future missions. The coolers can be used directly in liquid oxygen (LOx) or liquid methane ZBO systems, as shield coolers in liquid hydrogen tanks, or as first stage coolers in two-stage liquid hydrogen (LH2) ZBO cooler systems. Finally, the coolers could find applications in exploration missions where either propellants or breathable oxygen are extracted from the planetary atmosphere using a Sabatier or similar process. The gases could then be liquefied for storage either directly in return vehicle propellant tanks or on the planetary surface. Data presented were taken with the cooler operating in a vacuum of 10 (exp -5) torr, at controlled rejection temperatures from 300 K down to 275 K using a cold water heat exchanger bolted to the cooler. Heat loads were varied between 0.5 W and 15 W by supplying current to a 50 omega resistor mounted on a copper cold plate which was bolted to the cooler cold block. Silicon diodes mounted on both the cold plate and the heat exchanger provided accurate temperature measurement to within plus or minus 0.25 K and plus or minus 0.5 K respectively, up to 100 K with plus or minus 1% accuracy above 100 K. Input power to the compressor was limited to 180 W, corresponding to a maximum stroke of 80%.

Salerno, Lou↗