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  • 1
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    Crosstalk in solar polarization measurements (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The instrumental crosstalk associated with the Marshall Space Flight Center Vector Magnetograph and the solar crosstalk created by the magnetic field are described and their impact on the reconstruction of the solar vector magnetic field is analyzed. It is pointed out that identifying and correcting the crosstalk is important in the development of realistic models describing the solar atmosphere. Solar crosstalk is spatially dependent on the structure of the magnetic field while instrumental crosstalk is dependent on the position of the analyzer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Polarization analysis and measurement; Proceedings of the Meeting, San Diego, CA, July 19-21, 1992 (A93-33401 12-35); p. 281-294.
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  • 2
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    Analysis of the new polarimeter for the Marshall Space Flight Center vector magnetograph (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The magnetograph was upgraded in both electronic control of the magnetograph hardware and in the polarization optics. The problems associated with the orignal polarimeter were: (1) field of view errors associated with the natural birefringence of the KD*P crystals; (2.) KD*P electrode failure due to the halfwave dc voltage required in one of the operational sequences; and (3) breakdown of the retardation properties of some KD*Ps when exposed to a zero to halfwave modulation (DC) scheme. The new polarimeter gives up the flexibility provided by two variable waveplates to adjust the retardances of the optics for a particular polarization measurement, but solves the problems associated with the original polarimeter. With the addition of the quartz quarterwave plates, a new optical alignment was developed to allow the remaining KD*P to correct for errors in the waveplates. The new optical alignment of the polarimeter is prescribed. The various sources of error, and how those errors are minimized so that the magnetograph can look at the transverse field in real time are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Meas. of Solar Vector Magnetic Fields; p 160-172
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  • 3
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    Design of the polarimeter for the Solar Activity Measurements Experiments (SAMEX) vector magnetograph (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A design concept developed for a polarimeter on the vector magnetograph of the SAMEX satellite that would be very sensitive to solar vector magnetic fields is described. A description of the Poincare sphere is presented, along with the instrument scientific requirements, to provide an understanding of how the polarimeter design has been selected. It is shown that the design goal of a polarimetric sensitivity of 0.0001 can be achieved in the linear measurements using a hybrid analyzer. It is also noted that the systematic errors that produce linear crosstalk into the circular measurement will require the use of the redundant polarization measurements for in-flight calibrations and corrections of the data.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering (ISSN 0091-3286); 28; 131-140
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  • 4
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    A comparison of two transient methods of measuring thermal conductivity of particulate samples. (1973)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A comparison is made of the line source (LS) method and the differential line source (DLS) method of measuring thermal conductivity of particulate materials in vacuum. The DLS method requires more instrumentation in the measuring circuitry (an additional amplifier and a differentiating circuit), but since it does not require a stable temperature to initiate a test, it does not need a sample temperature control system. DLS tests can be taken as the temperature in the samples is rising from liquid nitrogen temperature to room temperature. This eliminates the practice of extrapolating thermal conductivity over this large temperature range. Also, the advantages of reduced test time, data reduction time, and small sample temperature rise enable the experimenter to take about 7-12 DLS tests in the time of 2 LS tests. Test data from the two methods agree very well.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 44; Aug. 197
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  • 5
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    Thermal diffusivity measurements of particulates using the differentiated line source (1975)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A method is described in which thermal diffusivity measurements can be made on particulate materials using the identical instrumentation as described in previous papers for measuring thermal conductivity. The measurements for the two properties can be made simultaneously, thus eliminating the changes in conditions when they are made separately. This system has particular application for studies of simulated lunar, planetary, or asteroidal surfaces in which laboratory measurements can be correlated with astronomical observations of thermal inertia. A representative set of data is shown which gives thermal diffusivity and thermal conductivity measurements on a particulate basalt in which the values for each temperature were taken simultaneously. A value for specific heat is calculated for measurements taken at each temperature.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 46; May 1975
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  • 6
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    Extending the field of view of KD/asterisk/P electrooptic modulators (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The use of KD(asterisk)P as a polarization rotator has been limited to small field of view instruments. To investigate this limitation, the index ellipsoid is used to describe the optical properties of KD(asterisk)P and to calculate the retardance and fast axis as a function of the angle of incidence and voltage. Computed converging light patterns are then compared with observed intensity patterns formed by KD(asterisk)P. Finally, computed intensity patterns are used to demonstrate how the field of view of KD(asterisk)P can be increased when properly aligned with a positive uniaxial crystal.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 17; Sept. 15
    Format: text
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  • 7
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    The MSFC vector magnetograph (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-27210)
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Solar Physics; 80; Sept
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  • 8
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    The new MSFC Solar vector magnetograph. Center director's discretionary fund (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The unique MSFC solar vector magnetograph allows measurements of all three components of the Sun's photospheric magnetic field over a wide field-of-view with spatial resolution determined by a 2.7 x 2.7 arc second pixel size. This system underwent extensive modifications to improve its sensitivity and temporal response. The modifications included replacing an SEC vidicon detector with a solid-state CCD camera; replacing the original digital logic circuitry with an electronic controller and a computer to provide complete, programmable control over the entire operation of the magnetograph; and installing a new polarimeter which consists of a single electro-optical modulator coupled with interchangeable waveplates mounted on a rotating assembly. The system is described and results of calibrations and tests are presented. Initial observations of solar magnetic fields with the new magnetograph are presented.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-82568 , NAS 1.15:82568
    Format: application/pdf
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  • 9
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    Thermal conduction in a composite circular cylinder - A new technique for thermal conductivity measurements of lunar core samples (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A technique is described for the measurement of the thermal conductivity of lunar core samples. According to their technique, the core sample is heated radiatively from the outside at a known rate, the temperature is measured at the surface of the core-tube, and the thermal conductivity of the sample is determined by comparing the measured temperature with the theory. The corresponding problems for a composite slab or sphere were solved and the solutions are presented for possible future application to the thermal conductivity measurements. The experimental apparatus construction and procedure are examined as well as the number of precautions taken to preserve the sample from disturbances and to improve the measurement results.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 10
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    Polarization studies of Zeeman affected spectral lines using the MSFC magnetograph (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Marshall Space Flight Center (MSFC) vector magnetograph records polarization images of absorption lines that are sensitive to magnetic fields. A method is presented for analyzing the Stokes spectral-line profiles of a photospheric Fe I absorption line (5250.2 A) which is influenced by the Zeeman effect. Using nonlinear least-square optimization, the observed Stokes profiles are compared with those generated from the theoretical solution of the polarized radiative transfer equations. The optimization process accounts for the spectral convolution of the source and the MSFC vector magnetograph. The resulting physical properties of the active region producing the polarized light are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Polarimetry: Radar, Infrared, Visible, Ultraviolet, and X-ray; May 15, 1990 - May 17, 1990; Huntsville, AL; United States
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