A cost effective critical space systems design approach

NASA-ISC requires avionics platforms capable of serving a wide range of applications in a cost-effective manner. In part, making the avionics platform cost effective means adhering to open standards and supporting the integration of COTS products with custom products. Inherently, operation in space requires low power, mass, and volume while retaining high performance, reconfigurability, scalability, and upgradability. The Universal Mini-Controller (UMC) project is based on a modified PC/104-Plus architecture while maintaining full compatibility with standard COTS PC/104 products. The architecture consists of a library of stackable building block modules, which can be mixed and matched to meet a specific application. A set of NASA developed core building blocks, (e.g. processor card, analog input/output card, high level analog card, and a Mil-Std-1553 card) were constructed to meet critical functions and unique interfaces     

Direct evidence for chromospheric evaporation in a well-observed compact flare

We have observed the flare of 1980 May 7 1456 UT with several Solar Maximum Mission instruments, in coordination with the Sacramento Peak Observatory Vacuum Tower Telescope. From the X-ray data we determine the total amount of plasma at T > 2 × 10⁶ K, commonly attributed to chromospheric evaporation. From Hα we have determined the amount of plasma that has been evaporated from the chromosphere. We find that enough material has been evaporated from the chromosphere to account for the X-ray plasma. Taken together, the Hα, soft and hard X-ray images suggest that chromospheric evaporation is driven both by flare accelerated electrons, during the impulsive phase, and conduction, during the thermal phase.     

The first decade of regular observation of land transformation from space

Data for all of the landmass of Canada has been received and archived since the launch of LANDSAT-1 in July 1972. This data has been used in a number of mapping and monitoring programs such as: revising topographic maps, mapping forest fire burns, mapping the variability of water levels in shallow prairie lakes and sloughs, evaluating rangeland conditions, mapping sedimentation levels due to natural phenomena or human activities, monitoring the environmental effects of major hydro electric projects.     

Hematopoietic responses under protracted exposures to low daily dose gamma irradiation.

In attempting to evaluate the possible health consequences of chronic ionizing radiation exposure during extended space travel (e.g., Mars Mission), ground-based experimental studies of the clinical and pathological responses of canines under low daily doses of 60Co gamma irradiation (0.3-26.3 cGy d-1) have been examined. Specific reference was given to responses of the blood forming system. Results suggest that the daily dose rate of 7.5 cGy d-1 represents a threshold below which the hematopoietic system can retain either partial or full trilineal cell-producing capacity (erythropoiesis, myelopoiesis, and megakaryopoiesis) for extended periods of exposure (>1 yr). Trilineal capacity was fully retained for several years of exposure at the lowest dose-rate tested (0.3 cGy d-1) but was completely lost within several hundred days at the highest dose-rate (26.3 cGy d-1). Retention of hematopoietic capacity under chronic exposure has been demonstrated to be mediated by hematopoietic progenitors with acquired radioresistance and repair functions, altered cytogenetics, and cell-cycle characteristics. Radiological, biological, and temporal parameters responsible for these vital acquisitions by hematopoietic progenitors have been partially characterized. These parameters, along with threshold responses, are described and discussed in relation to potential health risks of the space traveler under chronic stress of low-dose irradiation.     

Meteorological satellites and cooperative programs

Satellite data are available to meteorological centers around the world in two forms: (1) real-time reception directly from the spacecraft to the users; (2) processed data via the Global Telecommunications System (GTS). Real-time data is broadcast by satellites operated by both the U.S. and the U.S.S.R. From the NOAA series, Automatic Picture Transmission (APT) has been in wide use for 19 years. High Resolution Picture Transmission (HRPT) has been available to users with more sophisticated receiving equipment for the past 10 years. The Meteor satellites have been broadcasting for over 10 years. From the geostationary satellites (GOES), specialized products are broadcast via weather facsimile (WEFAX), and for users with very sophisticated ground systems, real-time geostationary images are available. Derived data, i.e., vertical temperature soundings of the atmosphere, etc., are routinely available on the GTS. The characteristics, utility, current utilization and future developments of these services will be reviewed and discussed.     

Landsat analysis of the Yangjiatan tungsten district,Hunan Province,People's Republic of China

The Yangjiatan tungsten district at latitude 27°28′ N. and longitude 111°54′E. is located about 140 km southwest of the city of Changsha and 35 km northeast of the town of Shaoyang, southeast Hunan Province, People's Republic of China. The deposits, consisting largely of scheelite in veins (Wang, 1975), are contained in highly folded and faulted sedimentary rocks of Paleozoic, Mesozoic, and Cenozoic age intruded by granitic plutons that are circular in plan view. The major faults and folds trend in a northeasterly direction; whereas, the plutons are clustered in a more easterly trending band across the Landsat image.Landsat image E-2338-02202, acquired December 26, 1975, is number 470 in the “Landsat Image Atlas of the People's Republic of China” printed by the Publishing House of Geology in 1979. A computer-compatible tape of the image was analyzed and used as a demonstration project under a United Nations technical assistance program. Supervised classification of soils, rocks, and vegetation; band ratioing to detect limonite alteration; and edge enhancement were all conducted to demonstrate the flexibility and capability of interactive computer systems. Field evaluation of the results of this work will be conducted by colleagues of the Remote Sensing Center for Geology, Ministry of Geology, in China.     

A prospectus on airborne laser mapping systems

Airborne laser systems have demonstrated enormous potential for topographic and bathymetric mapping. Both profiling and scanning systems have been evaluated for terrain elevation mapping, stream valley cross-section determination, and nearshore bottom profiling. Performance of the laser systems has been impressive and for some applications matches current operational accuracy requirements. Determining the position of individual laser measurements remains a constraint for most applications. Laser technology constrains some terrain and bathymetric applications, particularly for water penetration and frequency of measurements for high-spatial resolution over large areas.     

Effect of gravity on coupled convective and interfacial instabilities during directional solidification

We investigate the role of gravity in a linear stability analysis of the onset of coupled convective and morphological instabilities during directional solidification at constant velocity of a dilute alloy of tin in lead. For solidification vertically upwards, the temperature gradient alone would cause a negative density gradient and the solute gradient alone would cause a positive density gradient. Two types of instability are found, a convective type that occurs for long wavelengths and a morphological type that occurs for short wavelengths. In general, these are coupled but the morphological instabilities are practically independent of gravity and thus correspond to the predictions of previous morphological stability theory in which density changes and convection are neglected. The convective instabilities depend strongly on gravity; for a growth velocity of V = 1 μm/s and a temperature gradient in the liquid of G_L = 200 K/cm, the critical concentrations for convective instabilities are 3.1 × 10^?4, 3.1 × 10^?2 and 2.39 wt. % for g_e = 980 cm/s², 10^?4 g_e and 10^?6 g_e, respectively. For low velocities, the convective instabilities occur at much lower solute concentrations than the morphological instabilities whereas at high velocities, the reverse is true. At intermediate velocities where the changeover takes place, there are oscillitory instabilities of mixed character whose periods range from 60 s at g_e to 6 × 10⁴ s at 10^?6 g_e.