A 0.5 dB degradation of a flight model frequency generator was observed for three minutes. The zero risk environment led to Herculean efforts to resolve this problem. An extensive test program did not find the problem so a detailed visual inspection was performed and a dendrite was found at the lowest level of assembly. That module was replaced, and a paper search of the build process was initiated to determine if the problem was generic to the other units that had been produced.< >
The purpose of this article is to describe a new coding and data analysis method for qualitative and evaluation researchers. We label this method Environmental Coding, an adaptation of Schmieder-Ramirez and Mallette’s (2007) text, The SPELIT Power Matrix: Untangling the Organizational Environment With the SPELIT Leadership Tool, into the frameworks for qualitative data analysis outlined in Saldaña’s (2016) The Coding Manual for Qualitative Researchers. Environmental Coding employs an eclectic combination of coding approaches in hermeneutic cycles to generate a multidimensional analysis of an environment’s culture and its drivers. This article uses one of Donald Trump’s initial candidate speeches for the 2016 U.S. presidential campaign to illustrate Environmental Coding in action.
A test facility for burn-in testing of rubidium atomic frequency standards was developed and is described in this paper. This unique facility allows the investigator to capture continuous real time performance over long periods of time in a controlled environment. The facility was primarily developed to supplement post-manufacturing testing prior to integration on the spacecraft. This supplemental testing was implemented to keep the oscillators on, operating and monitored to provide a stabilization period, extended observation time, a test facility for special tests and as an aide to prevent integration returns. The secondary purpose for this facility was to perform non invasive investigative testing of problems as well as unusual phenomena. The facility and test equipment used in this facility (and their expected costs) are described.
Spurious RF oscillations were noted during the system test phase of the Geostationary Operational Environmental Satellite (GOES). A space qualified data collection platform report (DCPR) transmitter was subsequently found to have a cracked load resistor in its output isolator. The failure mechanism was caused by heat from the output power of a 20 watt transmitter being reflected into the DCPR transmitter through a sneak path. The reflection from a high VSWR at the rotary joint was not part of the normal operation but was due to unusual circumstances. The reliability of the load resistor under normal operation (low VSWR) over the life of the satellite was determined to be high.
Silicon solar cells have traditionally been used for conversion of direct sunlight to energy. These cells can also be used as low rate optical detectors. The internal resistances and capacitances, however, limit the usable bandwidth. Under forward bias conditions, diodes exhibit, in addition to the depletion layer capacitance, a diffusion capacitance caused by the rearrangement of minority carriers. A similar process occurs in solar cells when photons are absorbed and electron-hole pairs are produced. This paper presents a method successfully used by the authors to determine this unknown term as a function of background illumination.
A major part of satellite based navigation systems is the atomic frequency standard (AFS). The first satellite navigation was realized in the 1960's, with the US Navy's navigation satellite system known as TRANSIT. The TRANSIT satellites were launched with quartz crystal oscillators (XOs) for stable and precise frequency generation. In 1964 the Navy started the TIMATION program, a predecessor to GPS. The TIMATION developmental satellites (TIMATION-1 and -2) used high performance XOs and time referenced ranging signals. In 1974, TIMATION-3 extended the 'state-of-the-art' in satellite navigation by orbiting very precise AFSs. The superior frequency stability of the AFSs made satellite navigation a practical system to operate. This pioneering work provided the stimulus for developing reliable AFSs for space applications. This paper discusses AFSs on current and upcoming navigation systems. The two current systems are the Russian Global Navigation Satellite System (GLONASS) Global Positioning System (GPS). The upcoming navigation systems with AFSs are: the Galileo system, China's Beidou (a.k.a. Compass) satellite positioning system, and Japan's quasi-zenith satellite system (QZSS). Other systems with AFS are introduced. These including the Gravity Probe-A (GP-A) experiment, the military strategic and tactical relay (Milstar), the Advanced EHF (AEHF) program, the navigation experiment (NAVEX), the Cassini- Huygens mission, the cesium clock in the primary atomic clock in space (PARCS) mission and the Projet d'Horloge atomique par refroidissement d'atomes en orbite (PHARAO) project. The future of AFSs are discussed including subminiature Rb, smart clock technology, optically pumped cesium, coherent population trapping (CPT) technology. The Advanced Technology Atomic Frequency Standard (ATAFS) program and the DARPA Chip Scale Atomic Clock (CSAC) program are mentioned as well at the hydrogen maser and the developments with trapped ion, optical, and cold atom clocks.
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