Donald M. Horan

Electron temperature and emission measure variations during solar X-ray flares

X-ray emission from seventeen X-ray flares was analyzed to obtain electron temperatures and emission measures associated with the source region in the solar corona. The source region was assumed to be isothermal with a Maxwellian electron velocity distribution.Flares which were characterized by a rapid initial X-ray flux increase were found to also have a rapid initial rise in electron temperature and emission measure. Flares which were characterized by a gradual initial X-ray energy flux increase were found to have a less rapid initial rise in electron temperature and emission measure. In all X-ray flares studied the peak temperature chronologically preceded the peak X-ray flux and the peak flux never came after the peak emission measure.

The spectral dependence of solar soft X-ray flux values obtained by SOLRAD 9

Abstract The determination of solar energy flux values from ionization chamber experiments is discussed. Procedures and calculations necessary for the correction of SOLRAD 9 0.5–3 A and 1–8 A data and for the determination of the flare plasma temperature and emission measure are presented. These calculations are based on the continuum spectrum of Culhane (1969), the line spectrum of Tucker and Koren (1971), and experimental values of the detector efficiencies.

A multithermal analysis of solar x-ray emission

The NRL SOLRAD 10 satellite carries six ionization chambers to measure solar X-radiation in the 0.5 to 60 Å wavelength band. The X-ray emission spectrum in this range is determined by the derivative of the coronal emission measure (∫ Ne2dV) with respect to temperature when the thermal processes of bremsstrahlung, radiative recombination and line radiation are considered. If a simple model for this differential emission measure is used and detector responses to the calculated spectra are fitted to the SOLRAD data by a least squares method, the differential emission measure can be obtained for temperatures between 2 × 106K and 64 × 106K. Data during quiet and flaring periods are analyzed and the general behavior of the differential emission measure during flares is presented. This analysis is based on experimental measurements of the efficiencies of the SOLRAD detectors.

Direct measurements of the gradual extreme ultraviolet emission from large solar flares

Broadband sensors aboard the Naval Research Laboratorys SOLRAD 11 satellites measured solar emission in the 0.5 to 3 Å, 1 to 8 Å, 8 to 20 Å, 100 to 500 Å, 500 to 800 Å, and 700 to 1030 Å bands. Data from sixteen large flares show that the EUV emission is dominated by gradual emission which parallels the soft X-ray emission in duration and magnitude. The data are consistent with the separation of EUV and X-ray flare emission into two distinct components. A persistent component is made up of gradual EUV and gradual soft X-ray emissions. A brief component consists of hard X-rays, impulsive soft X-rays, and impulsive EUV emission.

On-orbit calibration of the Naval EarthMap Observer (NEMO) coastal ocean imaging spectrometer (COIS)

ABSTRACT Production of science or Naval products from hyperspectral data requires the careful calibration of thesensor and the validation of the algorithms to demonstrate that they produce the correct products at therequired accuracy. Thus a key part of the Navys Hyperspectral Remote Sensing Technology Program is the maintenance of accurate calibration for the Naval EarthMap Observer (NEMO) spacecrafts Coastal Ocean Imaging Spectrometer (COTS) during the lifetime of the spacecraft. On-Orbit COTS is calibrated in three ways: Moon imaging, using on-board calibration lamps, and imaging of wellcharacterized ocean and land scenes. The primary standard for COTS on-orbit calibration will be monthly imaging of the moon. The approach is similar to that used in NASAs SeaWiFS and MODISprograms, with the added complication that COTS images the Moon surface at much higher resolution than the NASA 1 km resolution sensors. On-board calibration lamps will not provide absolute calibration, but will be used to provide a stability check as frequently as once per orbit. Tmaging theknown reflectance land and open ocean sites will provide a data set for validating the calibration andatmospheric correction against measured surface reflectances. As an additional check COTS will becross-calibrated with two well calibrated aircraft sensors, NRLs Ocean PHILLS and NASAs AVTRTS,which will under-fly COTS and image the same ocean and land scenes.

Design And Description Of The Ultraviolet Plume Instrument (UVPI)

The Ultra Violet Plume Instrument (UVPI) is designed to image and make radiometric measurements of rocket plumes; image and conduct earth background measurements; and gather earth background clutter data in the 200 to 450 nm region. The instrument will be one of several experiments in an earth orbiting satellite to be launched by the Naval Research Laboratory. The optical system uses a ten cm aperture telescope with the image divided into two overlapping spectral regions, 200 to 360 nm and 250 to 450 nm. Four spectral filters isolate selected portions of the lower region for the plume camera and the upper region (i.e., 250 to 450 nm) is used primarily for tracking. Two intensified CCD cameras are used as sensors. Pointing and tracking capability for the UVPI system is provided by a two axis gimballed mirror with supporting electronics and software. The instrument can be configured for a specific encounter by ground command, or can be completely autonomous through use of its own onboard computer and data recorder.

Satellite observations with the UVPI instrument

Since its launch in February 1990, the Low-Power Atmospheric Compensation Experiment (LACE) satellite has been used as a space-based platform from which numerous observations have been carried out using the onboard Ultraviolet Plume Instrument (UVPI). UVPI consists of two pointable, co-aligned, intensified charged-coupled-device (ICCD) cameras sharing a common telescope mount. The instrument has obtained high spatial resolution near-UV/visible images of rocket plumes, and has observed aurorae, the Earths limb, and other features of the Earth background. A description of the instrument, the data gathered, and some selected results are presented.