A commercially available Macintosh-based data acquisition system and its application to a specific measurement is described. Based on Computer Aided Measurement and Control (CAMAC) and Nuclear Instrumentation Module (NIM) standard modules, the data acquisition system features a hardware and software interface to a Macintosh computer. This system has been used both for laboratory and remote site measurements, and has been found to perform well as both a highly interactive laboratory system and as a very automatable system for long term data acquisition. Ease in configuration allows for flexibility in fast response applications where a data acquisition system is needed in short time. The system software also supports much of the data analysis and presentation of results with a versatile set of histogram display and manipulation tools. In a recent application, the system controlled data acquisition for two germanium detectors used as part of the whole-spacecraft induced activation measurements of the Long Duration Exposure Facility (LDEF) satellite.

The Shuttle Activation Monitor (SAM) experiment was flown on the Space Shuttle Columbia (STS-28) from 8 – 13 August, 1989 in a 57°, 300 km orbit. One objective of the SAM experiment was to determine the relative effect of different amounts of shielding on the gamma-ray backgrounds measured with similarly configured sodium iodide (NaI) and bismuth germante (BGO) detectors. To achieve this objective twenty-four hours of data were taken with each detector in the middeck of the Shuttle on the ceiling of the airlock (a high-shielding location) as well as on the sleep station wall (a low-shielding location). For the cosmic-ray induced background the results indicate an increased overall count rate in the 0.2 to 10 MeV energy range at the more highly shielded location, while in regions of trapped radiation the low shielding configuration gives higher rates at the low energy end of the spectrum.

An X2/2B level solar flare occurred on 12 August, 1989, during the last day of the flight of the Space Shuttle Columbia (STS-28). Detectors on the GOES 7 satellite observed increased X-ray fluxes at approximately 1400 GMT and a solar particle event (SPE) at approximately 1600 GMT. Measurements with the bismuth germanate (BGO) detector of the Shuttle Activation Monitor (SAM) experiment on STS-28 showed factors of two to three increases in count rates at high latitudes comparable to those seen during South Atlantic Anomaly (SAA) passages beginning at about 1100 GMT. That increased activity was observed at both north and south high latitudes in the 57 degrees, 300 kilometer orbit and continued until the detector was turned off at 1800 GMT. Measurements made earlier in the flight over the same geographic coordinates did not produce the same levels of activity. This increase in activity may not be entirely accounted for by observed geomagnetic phenomena which were not related to the solar flare.

We report the first complete gamma-ray survey of a large spacecraft, the Long Duration Exposure Facility (LDEF). The survey was conducted using an array of germanium detectors from the U.S. Naval Research Laboratory (NRL) and individual detectors from the Institute for Space Science and Technology (ISST) to study the accumulation and distribution of radioisotopes induced in the wide variety of materials present on LDEF. Na-22, Be-7, Mn-54, and the positron annihilation line were all strongly observed. Also observed were traces of Co-58, Co-57, and Co-60. The most striking feature of the data was the unexpected distribution of Be-7, which was predominately observed on the leading surfaces of the spacecraft. The evidence clearly indicates an accretion of the Be-7 onto the surface of the LDEF. This is the first known observation of the deposition of a radioisotope onto the surface of a spacecraft. Be-7 is a spallation product of cosmic rays on nitrogen and oxygen in the upper atmosphere[1]. To explain the surface density of 5.4 x 10(5) atoms/cm2, the light Be-7 atom must be transported up from lower altitudes.

THE Long Duration Exposure Facility (LDEF), an orbiting unmanned satellite, was recently returned to Earth after almost six years in space. From radioactivity measurements, we have found significant quantities of the isotope Be-7 on the leading edge (but only on the leading edge) of LDEF. Although the absolute atmospheric concentration of Be-7 needed to explain this detection is extremely small (10(-7) atoms cm-3), it concentration of LDEF's altitude (310 km) must be several orders of magnitude higher than in the stratosphere below, where it is produced by cosmic-ray reactions with atmospheric nitrogen and oxygen nuclei. To explain the presence of Be-7 on the surface of LDEF, it must first be rapidly and efficiently transported to high altitudes, and then adsorbed onto the surface of the spacecraft. Neither process had been expected. Our detection may therefore lead to the use of Be-7 as an exo-atmospheric tracer, as well as to studies of surface interactions in space.

An experimental system was flown on the Space Shuttle Columbia from August 8 to 13, 1989 as part of the Shuttle Activation Monitor (SAM) program [P.S. Haskins et al., IEEE Trans. Nucl. Sci. NS-37 (6) (1990) 1256]. Gamma-ray spectra were collected both during flight and after landing from two 3 in. × 3 in. scintillation detectors, Nal and BGO. The shuttle was in a high inclination (57 °) orbit, at an altitude of 300 km which provided exposure to the trapped charged particles in the South Atlantic Anomaly (SAA) as well as the electrons in the Polar regions. The induced radiation observed by the detectors resulted from both external and internal sources activated by the interaction with the energetic charged particles. The flight data analysis indicates variation of the induced external radiation as a function of geomagnetic coordinates and amount of shielding, whereas the post-landing data exhibits induced internal radiation from the two different types of detector materials.

The retrieval of the Long Duration Exposure Facility spacecraft in January 1990 after nearly six years in orbit offered a unique opportunity to study the long term buildup of induced radioactivity in the variety of materials on board. We conducted the first complete gamma-ray survey of a large spacecraft on LDEF shortly after its return to earth. A surprising observation was the Be-7 activity which was seen primarily on the leading edge of the satellite, implying that it was picked up by LDEF in orbit. This is the first known evidence for accretion of a radioactive isotope onto an orbiting spacecraft. Other isotopes observed during the survey, the strongest being Na-22, are all attributed to activation of spacecraft components. Be-7 is a spallation product of cosmic rays on nitrogen and oxygen in the upper atmosphere. However, the observed density is much greater than expected due to cosmic-ray production in situ. This implies transport of Be-7 from much lower altitudes up to the LDEF orbit.

An experimental system which was used to compare gamma-ray detector materials in a space environment is described. Two 3-in*3-in scintillator detectors, NaI and BGO, were flown on the Space Shuttle Columbia as part of the Shuttle Activation Monitor (SAM) experiment. The goals of this experiment were to compare the performance of the two detector materials in the same environment and to measure the...

A 7.6-cm*7.6-cm BGO (bismuth germanate) detector was flown in the middeck of the Space Shuttle Columbia August 8-13, 1989, as part of the Shuttle Activation Monitor (SAM) experiment. One of the goals of this experiment was to compare the performance of the BGO to that of NaI in the same environment. Twenty-four hours of data in 5-min time bins were recorded with each detector in each of two locations in a high-inclination orbit (57 degrees , 300 km). Pre- aid post-flight low-background counting was preformed for identification of activities induced by the space radiation environment. A number of isotopes attributed to induced activity from exposure to the space radiation environment have been tentatively identified. >

(power requirements, cooling, and associated electronics). However, the factors are weighted differently for different applications. Energy resolution and timing characteristics may be the prime concern in an accelerator laboratory experiment, while weight, volume, and power requirements may override energy and timing preferences for space use. An experiment system is described which was used to materials in a space environment* Two 3 x 3 scintillator detectors, NaI and BGO, were flown on the Space Shuttle Columbia August 8-13, 1989 as part of gamma-ray the Shuttle Activation Monitor (SAM) experiment. The goals of this experiment were to compare the performance of the two detector materials in the same environment and to measure the variations in dynamic radiation background as a function of geomagnetic coordinates, amount of shielding, and type of detector material. Twenty-four hours of data in five-minute time bins were recorded with each detector in both highshielding and low-shielding locations in the Orbiter middeck. The high-inclination orbit (57O, 160 nautical miles) provided exposure to the trapped charged particles in the South Atlantic Anomaly as well as the electrons in the polar regions. The system used specially adapted off-the-shelf hardware for data acquisition and storage. The multichannel analyzer was a commercially available unit with added circuitry to support an active particle shield. Data during the flight were stored using a cassette tape recorder. A preliminary look at some of the data from the first flight is included.

A gamma-ray spectrometer for an upcoming space shuttle mission is described. Consisting of a 150 cm3 n-type germanium detector set inside active shielding of bismuth germanate and plastic scintillator, the instrument will be used in studies of the Orbiter background and the galactic center.

Ten of thirty burned patients tested by virus isolation and weekly serology showed evidence of active virus infection caused by Herpesvirus simplex, Herpesvirus varicellae, cytomegalovirus and vaccinia. The cytomegalovirus and most of the H. simplex infections were revealed only by laboratory investigation. The viral infections occurred most frequently in the more severely burned patients.