Engineering topics

Young, Erick T.

Publications and source records attributed to Young, Erick T..

23 records · Page 2

NASA NTRS1989

Future directions for NICMOS arrays

The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) for the Hubble Space Telescope (HST) requires focal plane arrays of 256x256 pixels for both its cameras and its spectrometers. The new arrays, developed by the Rockwell Corporation for NICMOS, have 40 microns pixels of HgCdTe bump bonded to a switched MOSFET readout. Expected read noise and dark current for the arrays at 60 K are 30 e and 1 e/sec. respectively. The basis for these numbers is previous experience with 128x128 arrays.

Thompson, R.↗

NASA NTRS1989

IRAS observations of dust heating and energy balance in the Rho Ophiuchi dark cloud

The equilibrium process dust emission in the Rho Ophiuchi dark cloud is studied. The luminosity of the cloud is found to closely match the luminosity of the clouds's known embedded and external radiation sources. There is no evidence for a large population of undetected low-luminosity sources within the cloud and unknown external heating is also only a minor source of energy. Most of the cloud's luminosity is emitted in the mid-to-far-IR. Dust temperature maps indicate that the dust is not hot enough to heat the gas to observed temperatures. A simple cloud model with a radiation field composed of flux HD 147889, S1, and Sco OB2 associations predicts the observed IRAS 60 to 100 micron in-band flux ratios for a mean cloud density n(H2) = 1400. Flattened 12 and 25 micron observations show much extended emission in these bands, suggesting stochastic heating of very small grains or large molecules.

Greene, Thomas P.↗

NASA NTRS1988

An unusual outflow around IRAS 16293-2422

The dense dusty molecular cloud core associated with the unusual protostellar source IRAS 16293-1422 (IRAS 1629A) was observed in the J = 2-1 transition of (C-12)O and (C-13)O. These observations indicate that IRAS 1629A is a source of an unusual high-velocity molecular outflow with four separate emission lobes. The morphology and velocity structure of the lobes may suggest the presence of a dual jet or double bipolar outflow system originating from the vicinity of IRAS 1269A. These observations resolve the outflowing gas into numerous high-velocity clumps which are either being continuously accelerated from low to high velocity along the entire length of the flow or are undergoing free-flow expansion.

Walker, Christopher K.↗

NASA NTRS1988

Development of FIR arrays with integrating amplifiers

The development of optimized photoconductor arrays suitable for far infrared space astronomical applications are described. Although the primary impetus is the production of a 16 by 16 element Ge:Ga demonstration array for SIRTF, the extension of this technology to Large Deployable Reflector (LDR) is considered. The optimization of Ge:Ga and Ge:Be photoconductor materials is discussed. In collaboration with Lawrence Berkeley Laboratory, measurements of FIR photoconductors with quantum efficiencies greater than 20 percent at 100 micrometers, and dark currents below 300 electrons/s are presented. Integrating J-FET amplifier technology is discussed. The current generation of integrating amplifiers has a demonstrated read noise of less than 20 electrons for an integration time of 100 s. The design is shown for a stackable 16 x n Ge:Ga array that utilizes a 16-channel monolithic version of the J-FET integrator. A part of the design is the use of a thin, thermally insulating substrate that allows the electronics to operate at the optimum temperature of 50 K while maintaining thermal and optical isolation from the detectors at 2 K. The power dissipation for the array is less than 16 mW. The array design may particularly be applicable to high resolution imaging spectrometers for LDR.

Young, Erick T.↗

NASA NTRS1986

Spectroscopic evidence for infall around an extraordinary IRAS source in Ophiuchus

Millimeter-wave continuum observations and spectral line observations of the J = 5-4 and J = 2-1 transitions of CS toward IRAS 16293-2422, an extremely cold infrared source associated with a high-velocity molecular outflow in the Rho Ophiuchi molecular cloud, are reported. The observations indicate that this source is a dust-enshrouded object embedded in a dense, elongated configuration of molecular gas whose major axis is roughly orthogonal to the direction of the double bipolar outflow observed in it. The observations appear to provide spectroscopic evidence for significant mass infall motions associated with a young stellar object, and suggest that IRAS 16293-2422 is a true protostar.

Walker, Christopher K.↗