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Skillman, D. R.

Publications and source records attributed to Skillman, D. R..

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Proposed SLR Optical Bench Required to Track Debris Using 1550 nm Lasers

A previous study has indicated that by using approx.1550 nm wavelengths a laser ranging system can track debris objects in an "eye safe" manner, while increasing the expected return rate by a factor of approx. 2/unit area of the telescope. In this presentation we develop the optical bench required to use approx.1550nm lasers, and integration with a 532nm system. We will use the optical bench configuration for NGSLR as the baseline, and indicate a possible injection point for the 1550 nm laser. The presentation will include what elements may need to be changed for transmitting the required power on the approx.1550nm wavelength, supporting the alignment of the laser to the telescope, and possible concerns for the telescope optics.

Satellite Laser Ranging↗
NASA NTRS2003

X-ray Variability of the Magnetic Cataclysmic Variable V1432 Aql and the Seyfert Galaxy NGC 6814

V1432 Aquilae (=RX J1940.2-1025) is the X-ray bright, eclipsing magnetic cataclysmic variable approximately 37 (sup) away from the Seyfert galaxy, NGC 6814. Due to a 0.3% difference between the orbital (12116.3 s) and the spin (12150 s) periods: the accretion geometry changes over the approximately 50 day beat period. Here we report the results of an RXTE campaign to observe the eclipse 25 times, as well as of archival observations with ASCA and BeppoSAX. Having confirmed that the eclipse is indeed caused by the secondary, we use the eclipse timings and profiles to map the accretion geometry as a function of the beat phase. We find that the accretion region is compact, and that it moves relative to the center of white dwarf on the beat period. The amplitude of this movement suggest a low-mass white dwarf, in contrast to the high mass previously estimated from its X-ray spectrum. The size of the X-ray emission region appears to be larger than in other eclipsing magnetic CVs. We also report on the RXTE data as well as the long-term behavior of NGC 6814, indicating flux variability by a factor of at least 10 on time scales of years.

Mukai, K.↗
NASA NTRS1985

Space Telescope moving target tracking

This paper formulates a Space Telescope (ST) moving target tracking algorithm and evaluates a practical implementation. The algorithm is shown to be satisfactory for tracking such moving objects as the moons of Mars.

Strikwerda, T. E.↗
NASA NTRS1981

54 Cam - A new variable star

Differential photometry of the RS CVn-type binary 54 Cam is presented, which shows that the light was variable with a period of 10.163 + or - 0.009 d, and with an amplitude increase from 0.03 to 0.06 m between 1979 and 1980. The photometric period of 10.163 d is 9% shorter than the orbital period of 11.0764 d, and is suggested as an explanation for the radio emission from 54 Cam due to a process of connection, disruption, and reconnection of magnetic field lines.

Hall, D. S.↗
NASA NTRS1976

EUV flux variations with solar rotation observed during 1974-1976 from AE satellites C, D, and E

Solar EUV fluxes in the spectral range from 140 to 1850 A have been observed by spectrophotometers on the satellites AE-C, D, and E. Variations over the long period of one or two years cannot be verified quantitatively, as the observed small variations are of the same magnitude as possible variations of instrumental sensitivities and estimated uncertainties of absolute values from the rocket experiment which established the calibration of the AE-C instrument. Fortunately, no similar difficulty exists for the interpretation of observed EUV variations within smaller time periods up to that of a full solar rotation. Results from AE-C observations for many different wavelength groups for the year 1974 are shown by some detail and compared with some recent observations made by the AE-D and AE-E instruments.

Hinteregger, H. E.↗