Radioisotope AMTEC power system designs for spacecraft applications

The authors describe and compare small (two-module) and larger (16-module) AMTEC (alkali metal thermal-to-electric converter) radioisotope powered systems and describe the computer model developed to predict their performance. The high efficiency and static conversion process combined with minimized parasitic losses and operating temperatures that allow the use of current materials while still maintaining a competitive radiator area are found to make AMTEC an excellent candidate for enhanced performance space power systems. AMTEC has the capability of reducing mission costs relative to other static conversion systems because of its high efficiency. AMTEC can also reduce cost relative to dynamic systems simply by being less massive (10 to 5000 W level), and its use eliminates the torque and vibration issues of dynamic systems     

The potential of direct broadcast satellites for the USA

The extensive coverage of the USA by cable television has posed a major hurdle for successful use of direct broadcast satellites. However, the potential for DBS service is improving because of breakthroughs in development of digital video compression and the availability of high-power satellites, combined with ample allocations of radio spectrum and orbital slots to DBS service. The success of DBS applications will depend critically on (a) the cost of small-antenna home receiving terminals, (b) operating expenses, and (c) demand for new services, such as HDTV, that could be provided by DBS systems more quickly and cheaply than through terrestrial transmission.     

Design and integration of a solar AMTEC power system with anadvanced global positioning satellite

A 1,200-W solar AMTEC (alkali metal thermal-to-electric conversion) power system concept was developed and integrated with an advanced global positioning system (GPS) satellite. The critical integration issues for the SAMTEC with the GPS subsystems included: (1) packaging within the Delta II launch vehicle envelope; (2) deployment and start-up operations for the SAMTEC; (3) SAMTEC operation during all mission phases; (4) satellite field of view restrictions with satellite operations; and (5) effect of the SAMTEC requirements on other satellite subsystems. The SAMTEC power system was compared with a conventional planar solar array/battery power system to assess the differences in system weight, size, and operations, Features of the design include the use of an advanced multitube, vapor anode AMTEC cell design with 24% conversion efficiency, and a direct solar insolation receiver design with integral LiF salt canisters for energy storage to generate power during the maximum solar eclipse cycle, The modular generator design consists of an array of multitube AMTEC cells arranged into a parallel/series electrical network with built-in cell redundancy. Our preliminary assessment indicates that the solar generator design is scaleable over a 500 to 2,500-W range. No battery power is required during the operational phase of the GPS mission. SAMTEC specific power levels greater than 5 We/kg and 160 We/m² are anticipated for a mission duration of 10 to 12 years in orbits with high natural radiation backgrounds     

Geostationary operational environmental satellite system performance

The United States supported the First GARP Global Experiment (FGGE) by the use of three geostationary satellites: GOES-East, located at 75°W longitude, GOES-West at 135°W longitude, and, through a special cooperative effort by the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, and the European Space Agency, GOES-Indian Ocean at 58°E longitude. During the FGGE Operational Year, the GOES-East coverage was provided, in turn, by GOES-2, SMS-1, and SMS-2. The GOES-West coverage was provided by GOES-3, and GOES-1 served at the GOES-Indian Ocean location. Satellite and instrument performance was generally satisfactory during that period except for the loss of infrared data from the Indian Ocean GOES for an aggregate of 31 days due to intermittent operation of the sensor. From the GOES-East and GOES-West data, the National Environmental Satellite Service produced cloud motion vectors for 0000, 1200, and 1800 GMT daily, numbering in total about 1400 vectors per day. High resolution wind vectors at the rate of somewhat under 3000 daily were derived from the data from all three satellites in the tropical zone bounded by 15°N and 15°S latitude by the University of Wisconsin. In addition to their contributions to the FGGE research data sets, these three satellites provided other real-time benefits and services.     

Recent results from satellite measurements of low-energy particles precipitated at high latitudes

Space Science Reviews -     

Thermal/suprathermal plasmas observed by the S-302 experiment on GEOS-1

The S-302 experiment has benefited more than most from the non-geostationary nature of the GEOS-1 orbit in so far as additional regions of quite different thermal and suprathermal plasmas were made accessible. Electron and positive ion spectra from three regions, the plasmasphere, plasmatrough and boundary layer, are described in order to highlight the variety of thermal plasmas observed.We show how, even in the presence of the local photoelectron sheath and its associated electric potential, the thermal characteristics can be derived. The success of this technique during active periods is demonstrated by the observation of both a heating of the thermal population and the appearance of a second field aligned thermal component during a period of intense wave activity.The detailed structure of the boundary layer adjacent to the magnetopause as observed on the 2nd December, 1977 shows only slow systematic development over a period of more than an hour. Where the thermal plasma density peaks the suprathermal positive ions show considerable drift motion as well as non-Maxwellian characteristics. This region is identified from the thermal particle data as being very close to the magnetopause, however, whether in fact the magnetopause was crossed requires corroborative data from the magnetometer and other experiments.